Wilderness Medicine, 5th Edition

Conversion Charts b LENGTH 1 inch = 2.54 cm 1 foot = 0.3048 m 1 yard = 0.9144 m 1 mile = 1.609 km

1 cm = 0.3937 inches 1 m = 3.2808 feet 1 m = 1.0936 yards 1 km = 0.6214 miles

b VOLUME 1 oz (U.S., liquid) = 29.5735 mL 1 oz (U.K.) = 28.4131 mL 1 CUP = 0.2366 L 1 pint (U.S., liquid) = 0.4732 L 1 pint (U.K.) = 0.5683 L 1 quart (U.S.) = 0.95 L 1 quart (U.K.) = 1.14 L 1 gallon (U.S.) = 3.7854 L 1 gallon (U.K.) = 4.55 L

1 mL = 0.0338 oz (U.S., liquid) 1 mL = 0.0352 oz (U.K.) 1 L = 4.2268 CUPS 1 L = 2.1 134 pints (U.S., liquid) 1 L = 1.7598 pints (U.K.) 1 L = 1.06 quarts (U.S.) 1 L = 0.88 quarts (U.K.) 1 L = 0.2642 gallons (U.S.) 1 L = 0.22 gallons (U.K.)

b WEIGHT 1 oz = 28.3495 g 1 Ib = 0.4536 kg

1 g = 0.0353 oz 1 kg = 2.2046 Ibs

b ENERGY 1 Joule = 0.000239 Kcal

1 Kcal = 4184 Joules

b TEMPERATURE To convert Fahrenheit to Celcius: degrees F - 32 x 5/9 To convert Celcius to Fahrenheit: degrees C x 9/5 + 32

Contributors Javier A. Adachi, MD Assistant Professor, Department of Infectious Diseases, Infection Control, and Employee Health, The University of Texas MD Anderson Cancer Center; Clinical Assistant Professor, Department of Internal Medicine, The University of Texas Health Science Center at Houston Medical School, Houston, Texas; Visiting Professor, Universidad Peruana Cayetano Heredia, Lima, Peru Martin E. Alexander, BScF, MScF, PhD, RPF Adjunct Professor, Wildland Fire Science and Management, Department of Renewable Resources, University of Alberta; Senior Fire Behavior Research Officer, Northern Forestry Centre, Canadian Forest Service, Edmonton, Alberta; Honorary Research Associate, Faculty of Forestry and Environmental Management, University of New Brunswick, Fredericton, New Brunswick, Canada Robert C. Allen, DO, FACEP Colonel, United States Air Force MC CFS; Chief, Aeromedical Evacuation Branch, USAF School of Aerospace Medicine, Brooks City-Base, Texas Bryan E. Anderson, MD Assistant Professor of Dermatology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania Susan Anderson, MD, MS Adjunct Clinical Assistant Professor, Division of Infectious Diseases and Geographic Medicine, Stanford University, Stanford; Travel, Tropical, and Wilderness Medicine Consultant, Travel Medicine and Urgent Care, Palo Alto Medical Foundation, Palo Alto, California Christopher J. Andrews, BE, MBBS, MEngSc, MAppLaw, PhD, DipCSc, EDIC Consulting Medical Practitioner and Electrical Engineer, Indooroopilly Medical Centre, Brisbane, Queensland, Australia E. Wayne Askew, PhD Professor and Director, Division of Nutrition, University of Utah College of Health, Salt Lake City, Utah Dale Atkins, BA United States Representative, Avalanche Commission, International Commission for Alpine Rescue Switzerland, RECCO, AB, Lidingö, Sweden Brett D. Atwater, MD Fellow in Cardiovascular Medicine, Department of Medicine, University of Wisconsin Hospital and Clinics, Madison, Wisconsin

Paul S. Auerbach, MD, MS, FACEP Clinical Professor of Surgery, Division of Emergency Medicine, Department of Surgery, Stanford University School of Medicine, Stanford, California Kira Bacal, MD, PhD, MPH Health Policy Fellow, Voinovich Center for Leadership and Public Affairs, Ohio University, Athens, Ohio; Consultant, Mauri Ora Associates, Auckland, New Zealand Howard D. Backer, MD, MPH, FACEP Lecturer, Department of Public Health, University of California, Berkeley; Chief, Immunization Branch, Medical Consultant, Emergency Preparedness, Division of Communicable Disease Control, California Department of Health Services, Richmond, California Greta J. Binford, PhD Assistant Professor, Department of Biology, Lewis & Clark College, Portland, Oregon Jolie Bookspan, MEd, PhD Instructor, Temple University; Director, Neck and Back Pain Sports Medicine; Advisory and Review Board, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania Warren D. Bowman, MD, FACP Clinical Associate Professor Emeritus, Department of Internal Medicine, University of Washington School of Medicine, Seattle, Washington; Staff Physician (Retired), Department of Internal Medicine, Division of Hematology-Oncology, The Billings Clinic, Billings, Montana Leslie V. Boyer, MD, FACMT Associate Professor of Clinical Pediatrics, Department of Pediatrics, University of Arizona College of Medicine, Tucson, Arizona George H. Burgess Director, Florida Program for Shark Research, Florida Museum of Natural History, University of Florida, Gainesville, Florida Robert K. Bush, MD Professor, Department of Medicine, University of Wisconsin School of Medicine and Public Health; Professor (Courtesy), Food Research Institute, University of Wisconsin; Chief of Allergy, William S. Middleton VA Hospital, Madison, Wisconsin Sean Paul Bush, MD, FACEP Professor of Emergency Medicine, Department of Emergency Medicine, Loma Linda University School of Medicine; Director, Fellowship of Envenomation Medicine, Department of Emergency Medicine, Loma Linda University Medical Center, Loma Linda, California

v

vi

Contributors

Frank K. Butler, Jr., MD Command Surgeon, U.S. Special Operations Command, Tampa, Florida Steven C. Carleton, MD, PhD Associate Professor, Department of Emergency Medicine, University of Cincinnati College of Medicine; Emergency Physician, Center for Emergency Care, University Hospital, Inc., Cincinnati, Ohio Betty Carlisle, MD Assistant Adjunct Professor, Division of Public Health, Center for Global Health, University of Rochester, Rochester, New York; Director, McMurdo Medical, and Base Physician, Amundsen-Scott Station and Palmer Station, Antarctica John W. Castellani, PhD Research Physiologist, Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts Monalisa Chatterjee, MPhil PhD Candidate, Department of Geography, Rutgers University, New Brunswick, New Jersey Richard F. Clark, MD Professor of Medicine, University of California, San Diego, School of Medicine; Director, Division of Medical Toxicology, Department of Emergency Medicine, UCSD Medical Center; Medical Director, California Poison Control System, San Diego Division, San Diego, California Bryan R. Collier, DO, FACS, CNSP Assistant Professor of Surgery, Vanderbilt University School of Medicine; Assistant Professor of Surgery, Department of Surgical Sciences, Division of Trauma and Surgical and Critical Care, Vanderbilt University Medical Center, Nashville, Tennessee Donald C. Cooper, PhD, CFO, OFE, NREMT-P Deputy Fire Chief, Cuyahoga Falls Fire Department, City of Cuyahoga Falls; President, National Rescue Consultants, Inc., Cuyahoga Falls, Ohio Mary Ann Cooper, MD Professor, Departments of Emergency Medicine and Bioengineering, University of Illinois College of Medicine at Chicago, Chicago, Illinois Larry Ingram Crawshaw, PhD Professor, Department of Biology, Portland State University; Professor, Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, Oregon Gregory A. Cummins, DO, MS Assistant Clinical Instructor, Adjunct Faculty, Department of Internal Medicine, Kansas City University of Medicine and Biosciences, Kansas City; Hospitalist, Department of Internal Medicine, North Kansas City Hospital, North Kansas City, Missouri Daniel F. Danzl, MD Professor and Chair, Department of Emergency Medicine, University of Louisville School of Medicine, Louisville, Kentucky

Richard C. Dart, MD, PhD Professor of Surgery, Division of Emergency Medicine, University of Colorado School of Medicine; Director, Rocky Mountain Poison and Drug Center, Denver Health, Denver, Colorado Samhita Dasgupta, BS Department of Biology, Portland State University, Portland, Oregon Ian Davis, MBBCH, BSc (Hons) Resident Medical Officer, Department of Accident and Emergency, Cirencester Hospital, Gloucestershire; Polar Medicine, Medical Cell, Royal Geographical Society, London; Chief Medical Officer, Polar Challenge, Venture Group, Cirencester, England, United Kingdom Kathleen Mary Davis, MS Superintendent, Montezuma Castle and Tuzigoot National Monuments, National Park Service, U.S. Department of the Interior, Camp Verde, Arizona Kevin Jon Davison, ND, LAc Clinic Director, Maui East-West Clinic, Haiku, Hawaii Chad P. Dawson, PhD Professor, Faculty of Forest and Natural Resources Management, State University of New York, College of Environmental Science and Forestry, Syracuse, New York Thomas G. DeLoughery, MD, FACP Professor of Medicine and Pathology, Department of Medicine and Pathology, Divisions of Hematology and Laboratory Medicine, Oregon Health and Science University, Portland, Oregon Mark W. Donnelly, MD Attending Physician, Department of Emergency Medicine, Samaritan Lebanon Community Hospital, Lebanon, Oregon Howard J. Donner, MD Family Physician, Telluride, Colorado Eric Douglas, BA, DMT Director of Training, Divers Alert Network, Durham, North Carolina Herbert L. DuPont, MD Chief, Internal Medicine, St. Luke’s Episcopal Hospital; Director, Center for Infectious Diseases, University of Texas, Houston, School of Public Health; Mary W. Kelsey Chair, University of Texas, Houston, Medical School; H. Irving Schweppe, Jr., Chair and Vice Chairman, Department of Medicine, Baylor College of Medicine, Houston, Texas Thomas J. Ellis, MD Associate Professor, Department of Orthopaedic Surgery, Oregon Health and Science University, Portland, Oregon Blair Dillard Erb, MD, FACP Grand Junction, Colorado; Past President, Wilderness Medical Society, Lawrence, Kansas

Contributors Timothy B. Erickson, MD, FACEP, FACMT, FAACT Professor, Department of Emergency Medicine, and Director, Division of Toxicology, University of Illinois College of Medicine at Chicago, Chicago, Illinois Charles D. Ericsson, MD Professor of Medicine and Head, Clinical Infectious Diseases, Department of Medicine, University of Texas Medical School at Houston; Chief of Infectious Diseases, Hermann Hospital; Chief of Infectious Diseases and Medical Director of Infection Control, Lyndon Baines Johnson Hospital; Director, Travel Medicine Clinic, University of Texas Medical School at Houston, Houston, Texas Joanne Feldman, MD, MS Wilderness Medicine Fellow and Clinical Instructor, Division of Emergency Medicine, Department of Surgery, Stanford University School of Medicine, Stanford, California Murray E. Fowler, DVM Professor Emeritus, Department of Medicine and Epidemiology, University of California, Davis, School of Veterinary Medicine, Davis, California

vii

Kimberlie A. Graeme, MD Associate Professor, Department of Emergency Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota; Consultant, Department of Emergency Medicine, Mayo Clinic Scottsdale, Scottsdale, Arizona Andrea R. Gravatt, MD, FAAP Clinical Assistant Professor, Department of Pediatric Medicine, University of Washington School of Medicine; Clinical Assistant Professor, Department of Pediatrics, Children’s Hospital and Regional Medical Center, Seattle; Attending Physician, Department of Pediatric Emergency Medicine, Mary Bridge Children’s Hospital, Tacoma, Washington Colin K. Grissom, MD Associate Professor of Medicine (Clinical), Department of Internal Medicine, Division of Pulmonary and Critical Care, University of Utah School of Medicine; Co-Director, Shock Trauma Respiratory Intensive Care Unit, Critical Care Medicine, LDS Hospital; Assistant Medical Director, Life Flight, LDS Hospital and Intermountain Health Care, Salt Lake City, Utah

Mark S. Fradin, MD Clinical Associate Professor, Department of Dermatology, University of North Carolina School of Medicine, Chapel Hill, North Carolina

Peter H. Hackett, MD Clinical Director, Altitude Research Center, University of Colorado School of Medicine, Denver; Director, Center for Altitude Medicine; Director of Emergency Services, Telluride Medical Center, Telluride, Colorado

Bryan L. Frank, MD Past President, International Council of Medical Acupuncture and Related Techniques, Brussels, Belgium; President, Global Mission Partners, Edmond, Oklahoma

Charles G. Hawley, BS Vice President of Product Development, West Marine, Watsonville, California

Luanne Freer, MD, FACEP Staff Physician, Emergency Department, Bozeman Deaconess Hospital, Bozeman, Montana; Medical Director, Yellowstone National Park, Yellowstone, Wyoming Steven P. French, MD Co-Founder, Yellowstone Wyoming

Grizzly

Foundation,

Jackson,

Stephen L. Gaffin, PhD Professor of Physiology, American University of the Caribbean, St. Maarten, Netherlands Antilles; Research PhysiologistImmunologist, Thermal and Mountain Medicine, U.S. Army Medical Corps (Retired), Framingham, Massachusetts Angela F. Gardner, MD, FACEP Assistant Professor, Division of Emergency Medicine, Department of Surgery, University of Texas Medical Branch, Galveston, Texas Daniel Garza, MD Clinical Instructor, Division of Emergency Medicine, Department of Surgery, Stanford University School of Medicine, Stanford; Team Physician, San Francisco 49ers, San Francisco, California Gordon G. Giesbrecht, PhD Professor, Health, Leisure and Human Performance Research Institute; Professor, Department of Anesthesia, University of Manitoba Faculty of Medicine, Winnipeg, Manitoba, Canada

Sue L. Hefle, PhD† Associate Professor, Food Allergy Research and Resource Program, University of Nebraska, Lincoln, Nebraska John P. Heggers, PhD, FAAM, CWS (AAWM) Professor of Surgery (Plastic) (Retired), University of Texas Medical Branch School of Medicine; Director of Clinical Microbiology and Director of Microbiology Research, Shriners Burns Institute, Galveston, Texas David M. Heimbach, MD Professor of Surgery, University of Washington School of Medicine, Seattle, Washington Lawrence E. Heiskell, MD, FACEP, FAAFP Department of Emergency Medicine, Marine Corps Air Ground Combat Center, Robert E. Bush Naval Hospital, Twenty Nine Palms; Director, International School of Tactical Medicine, Palm Springs, California John C. Hendee, PhD Professor Emeritus and Dean (Retired), University of Idaho College of Natural Resources, Moscow, Idaho; Vice President for Science and Education, WILD Foundation, Boulder, Colorado Henry J. Herrmann, DMD, FAGD Private Practice, Falls Church, Virginia †

Deceased.

viii

Contributors

Ronald L. Holle, MS Meteorologist, Holle Meteorology & Photography, Oro Valley, Arizona Renee Y. Hsia, MD, MSc Stanford/Kaiser Emergency Medicine Residency Program, Division of Emergency Medicine, Department of Surgery, Stanford University School of Medicine, Stanford, California Franklin R. Hubbell, DO Clinical Professor, University of New England College of Osteopathic Medicine, Biddeford, Maine Steve E. Hudson Deputy Director, Walker County Emergency Management Agency; President, Pigeon Mountain Industries, Inc., LaFayette, Georgia Kenneth V. Iserson, MD, MBA Professor, Department of Emergency Medicine, University of Arizona College of Medicine; Chair, Bioethics Committee and Emergency Physician, University Medical Center; Medical Director, Southern Arizona Rescue Association (SARA); Director, Arizona Bioethics Program, University of Arizona Health Sciences Center, Tuscon, Arizona Michael E. Jacobs, MD United States Coast Guard Licensed Captain; MedSail Founder and Program Director; Medical Director, Vineyard Medical Services, Martha’s Vineyard, Massachusetts Suzanne C. Jensen, MD Emergency Physician, Department of Emergency Medicine, Mills-Peninsula Hospital, Burlingame, California Lee A. Kaplan, MD Clinical Professor (Voluntary), Division of Dermatology, Department of Medicine, University of California, San Diego, School of Medicine; Dermatologist Medical Group, La Jolla, California James W. Kazura, MD Professor of International Health, Medicine and Pathology, Center for Global Health and Diseases, Case Western Reserve University School of Medicine; Professor of Medicine, University Hospitals of Cleveland, Cleveland, Ohio Garry W. Killyon, MD, DDS, FACS Assistant Professor, Department of Surgery, Division of Plastic Surgery, University of Texas Medical Branch; Shriners Burns Hospital, Galveston, Texas Kenneth W. Kizer, MD President and CEO, Medsphere Systems Corporation, Aliso Viejo, California Judith R. Klein, MD, FACEP Assistant Clinical Professor of Medicine, Emergency Services, Department of Medicine, University of California, San Francisco, School of Medicine; San Francisco General Hospital, San Francisco, California

Karen Nolan Kuehl, MD, FACEP Adjunct Assistant Professor, Department of Emergency Medicine, Oregon Health and Science University; Attending Physician, Department of Emergency Medicine, Legacy Good Samaritan Hospital, Portland, Oregon; Attending Physician, Department of Emergency Medicine, St. John’s Hospital, Jackson, Wyoming Peter Kummerfeldt, AD (Rescue and Survival Operations) President, OutdoorSafe, Inc., Colorado Springs, Colorado Carolyn S. Langer, MD, JD, MPH Instructor, Harvard School of Massachusetts

Public

Health,

Boston,

Daniel M. Laskin, DDS, MS Professor and Chairman Emeritus, Department of Oral and Maxillofacial Surgery, Virginia Commonwealth University Schools of Dentistry and Medicine; Professor of Surgery, Department of Oral and Maxillofacial Surgery, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia Patrick H. “Rick” LaValla President, ERI International, Olympia, Washington; Director of Operations, All Hands Consulting, Columbia, Maryland; Director, International Search and Rescue Alliance Catherine Yumi Lee, MPH Research Faculty Associate, School of Public Health, New York Medical College, Valhalla, New York Jay Lemery, MD Attending Physician, Department of Emergency Medicine, Weill Medical College of Cornell University; Attending Physician, Department of Emergency Medicine, New York-Presbyterian Hospital, New York, New York Matthew R. Lewin, MD, PhD Assistant Professor of Medicine, Division of Emergency Medicine, Department of Medicine, University of California, San Francisco, School of Medicine, San Francisco, California James R. Liffrig, MD, MPH Lieutenant Colonel, U.S. Army Medical Corps; Chief, Department of Family Medicine, Womack Army Medical Center, Fort Bragg, North Carolina Grant S. Lipman, MD Clinical Instructor of Surgery, Division of Emergency Medicine, Department of Surgery, Stanford University School of Medicine, Stanford, California Binh T. Ly, MD Associate Clinical Professor, Department of Medicine, University of California, San Diego, School of Medicine; Director, Medical Toxicology Fellowship, UCSD Medical Center, Division of Medical Toxicology, and California Poison Control System–San Diego Division; Associate Director, Emergency Medicine Residency, Department of Emergency Medicine, UCSD Medical Center, San Diego, California

Contributors

ix

Edgar Maeyens, Jr., MD Private Practice in Dermatology and Dermatopathology; Department of Medicine, Division of Dermatology, Bay Area Hospital, Coos Bay, Oregon; Advisory Board Member, Nicholas School of the Environment and Earth Sciences, Marine Laboratory, Duke University, Durham, North Carolina

Jude T. McNally, RPh, DABAT Managing Director, Arizona Poison and Drug Information, University of Arizona, Tucson, Arizona

Swaminatha V. Mahadevan, MD, FACEP, FAAEM Assistant Professor of Surgery/Emergency Medicine; Associate Chief, Division of Emergency Medicine, Department of Surgery; and Medical Director, Stanford University Emergency Department, Stanford University School of Medicine, Stanford, California

James Messenger Lieutenant, Cuyahoga Falls Fire Department, City of Cuyahoga Falls, Cuyahoga Falls, Ohio

Roberta Mann, MD Clinical Associate Professor, Department of Surgery, University of Southern California Keck School of Medicine, Los Angeles; Medical Director, Torrance Memorial Burn Center and Wound Healing Center, Torrance Memorial Medical Center, Torrance, California Rick Marinelli, ND, MAcOM Clinical Professor, National College of Naturopathic Medicine, Oregon College of Oriental Medicine; Clinic Director, Natural Medicine Clinic, Portland, Oregon Ariel Dan Marks, MD, MS, FACEP Director of Quality Improvement, Emergency Department, Sequoia Hospital, Redwood City, California James G. Marks, Jr., MD Professor and Chair, Department of Dermatology, Penn State Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania Denise Martinez, MS, RD Clinical Instructor, Division of Nutrition, University of Utah College of Health, Salt Lake City, Utah Michael J. Matteucci, MD Assistant Clinical Professor, Department of Medicine, University of California, San Diego, School of Medicine; Attending Physician, Division of Medical Toxicology and Department of Emergency Medicine, University of California, San Diego, Medical Center; Assistant Residency Director, Department of Emergency Medicine, Naval Medical Center San Diego, San Diego, California

Liran Mendel, MSc Researcher, Heller Institute for Medical Research, Sheba Medical Center, Tel-Hashomer, Israel

Timothy P. Mier, BA, EMT-P Lieutenant and Deputy Fire Marshal, Cuyahoga Falls Fire Department, City of Cuyahoga Falls, Cuyahoga Falls, Ohio James K. Mitchell, PhD Professor of Geography, Rutgers University, Piscataway, New Jersey David G. Mohler, MD Associate Clinical Professor, Department of Orthopaedic Surgery, Stanford University School of Medicine, Stanford, California Richard E. Moon, MD, FACP Professor of Anesthesiology and Associate Professor of Medicine, Duke University School of Medicine; Medical Director, Center for Hyperbaric Medicine and Environmental Physiology; Senior Medical Consultant, Divers Alert Network, Duke University Medical Center, Durham, North Carolina Daniel S. Moran, PhD Department of Physiology and Pharmacology, Tel-Aviv University Sackler School of Medicine, Tel-Aviv; Institute of Military Physiology, Heller Institute for Medical Research, Sheba Medical Center, Tel-Hashomer, Israel Barry Morenz, MD Associate Professor of Clinical Psychiatry, University of Arizona College of Medicine; Medical Staff, Department of Psychiatry, University Medical Center, Tucson, Arizona John A. Morris, Jr., MD Professor of Surgery and Biomedical Informatics, Department of Surgery, Division of Trauma, Vanderbilt University School of Medicine; Director, Division of Trauma and Surgical Critical Care, Department of Surgery, Division of Trauma, Vanderbilt University Medical Center, Nashville, Tennessee

Vicki Mazzorana, MD, FACEP Clinical Assistant Professor, Division of Emergency Medicine, Department of Surgery, Stanford University School of Medicine, Stanford, California

Robert W. Mutch, BA, MSF Consultant, Fire Management Montana

Robert L. McCauley, MD Professor of Plastic and Reconstructive Surgery and Pediatrics, Department of Surgery, University of Texas Medical Branch; Chief, Plastic and Reconstructive Surgery, Shriners Hospital for Children, Galveston, Texas

Arian Nachat, MD Ultrasound Director, Valley Emergency Physicians, Oakland; Undersea and Hyperbaric Fellow, Department of Emergency Medicine; Attending and Clinical Instructor, Long Beach Memorial Medical Center, Long Beach, California

Loui H. (Clem) McCurley Technical Specialist, Alpine Rescue Team, Evergreen, Colorado; Vice President, Pigeon Mountain Industries, Inc., LaFayette, Georgia; Past President, Society of Professional Rope Access Technicians (SPRAT), Wayne, Pennsylvania

Roger J. Nagy, MD Assistant Director, Department of Trauma, Penrose-St. Francis Hospitals; Partner, Colorado Springs Surgical Associates, PC, Colorado Springs, Colorado

Applications,

Missoula,

x

Contributors

Andrew B. Newman, MD, FCCP Adjunct Professor of Medicine, Pulmonary and Critical Care, Stanford University School of Medicine, Stanford; Chairman and Managing Director, Ocean Medicine Foundation, Palo Alto, California

Mark Plotkin, PhD President, Amazon Conservation Team, Arlington, Virginia

Donna L. Nimec, MD Director, Pediatric Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Boston, Massachusetts

William P. Riordan, Jr., MD Assistant Professor of Surgery, Division of Trauma and Surgical Critical Care, Vanderbilt University Medical Center, Nashville, Tennessee

David A. Nix, MD, PhD Academic and Administrative Follow, Stanford/Kaiser Emergency Medicine Residency Program, and Clinical Instructor, Division of Emergency Medicine, Department of Surgery, Stanford University School of Medicine, Stanford, California

Robert C. Roach, PhD Chief, Research Division, Altitude Research Center, University of Colorado at Denver Health Sciences Center, Denver, Colorado

Eric K. Noji, MD, MPH Senior Policy Advisor for Health and National Security, Office of Terrorism Preparedness and Emergency Response, Centers for Disease Control and Prevention, Atlanta, Georgia Donald B. Nolan, MD Clinical Associate Professor of Neurology, University of Virginia School of Medicine, Charlottesville; Attending Physician (Retired), Department of Neurology, Carilion Roanoke Memorial Hospitals, Roanoke, Virginia Robert L. Norris, MD, FACEP Associate Professor of Surgery and Chief, Division of Emergency Medicine, Department of Surgery, Stanford University School of Medicine, Stanford, California Bohdan T. Olesnicky, MD, ABEM, ABIM Vice Chairman, Department of Emergency Medicine, Christ Hospital, Jersey City, New Jersey; Instructor, International School of Tactical Medicine, Palm Springs, California Sheryl K. Olson, RN, BSN, CCRN Rotor Wing Flight Nurse, Colorado Springs; Wilderness Medicine and Survival/Safety Instructor, WildernessWise, LLC, Manitou Springs, Colorado Edward J. (Mel) Otten, MD, FACMT Professor of Emergency Medicine and Pediatrics and Director, Division of Toxicology, University of Cincinnati College of Medicine, Cincinnati, Ohio Ketan H. Patel, MD Stanford/Kaiser Emergency Medicine Residency Program, Division of Emergency Medicine, Department of Surgery, Stanford University School of Medicine, Stanford, California

Sheila B. Reed, MS Partner, InterWorks LLC, Madison, Wisconsin

Martin C. Robson, MD Emeritus Professor, Department of Surgery, University of South Florida College of Medicine, Tampa, Florida Matthew T. Roe, MD, MHS Assistant Professor of Medicine, Division of Cardiovascular Medicine, Duke Clinical Research Institute, Duke University Medical Center, Durham, North Carolina Sandra M. Schneider, MD, FACEP Professor and Chair, Department of Emergency Medicine, University of Rochester School of Medicine and Dentistry; Emergency Physician-in-Chief, Department of Emergency Medicine, Strong Memorial Hospital, Rochester, New York Robert B. Schoene, MD Professor of Medicine, Division of Pulmonary, Critical Care Medicine and Physiology, University of California, San Diego, School of Medicine; Program Director, Internal Medicine Residency, Department of Medicine, University of California, San Diego, Medical Center, San Diego, California Jamie Shandro, MD, MPH Assistant Professor, Division of Emergency Medicine, Harborview Medical Center, University of Washington School of Medicine, Seattle, Washington David J. Smith, Jr., MD Juan Bolivar Chair of Surgical Oncology, Professor, and Director, Division of Plastic Surgery, Department of Surgery, University of South Florida College of Medicine; Medical Director, Tampa General Hospital Regional Burn Center, Tampa, Florida

Naresh J. Patel, DO Private Practice, Fort Wayne Allergy and Asthma Consultants, Fort Wayne, Indiana

Alan M. Steinman, MD, MPH Professional Affiliate, Health, Leisure and Human Performance Research Institute, University of Manitoba, Winnipeg, Manitoba, Canada; Rear Admiral (Retired), U.S. Public Health Service, U.S. Coast Guard

Sheral S. Patel, MD Pediatric Infectious Diseases, International Adoption, and Travel Medicine, Coventry, Connecticut

Robert C. Stoffel, BS President and CEO, Emergency Response International, Cashmere, Washington

Timothy F. Platts-Mills, MD Emergency Physician, Department of Emergency Medicine, University of California, San Francisco, Fresno, Medical Education Program, Fresno, California

Jeffrey R. Suchard, MD, FACEP, FACMT Associate Professor of Clinical Emergency Medicine and Director of Medical Toxicology, Department of Emergency Medicine, University of California, Irvine, Medical Center, Orange, California

Contributors Marc F. Swiontkowski, MD Professor and Chair, Department of Orthopaedic Surgery, University of Minnesota Medical School, Minneapolis, Minnesota Julie A. Switzer, MD Assistant Professor, Department of Orthopaedic Surgery, University of Minnesota Medical School, Minneapolis; Director of Geriatric Trauma, Department of Orthopaedic Surgery, Regions Hospital, St. Paul, Minnesota Steve L. Taylor, PhD Professor, Food Allergy Research and Resource Program, University of Nebraska, Lincoln, Nebraska Robert I. Tilling, PhD Senior Research Geologist—Volcanologist (Scientist Emeritus), Volcano Hazards Team, U.S. Geological Survey, Menlo Park, California David A. Townes, MD, MPH, FACEP Associate Professor and Associate Residency Program Director, Division of Emergency Medicine, University of Washington School of Medicine; Founder and Medical Director, AdventureMed, Seattle, Washington Stephen J. Traub, MD Assistant Professor of Medicine, Harvard Medical School; CoDirector, Division of Toxicology, Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts Karen B. Van Hoesen, MD, FACEP Clinical Professor of Medicine and Director, Undersea and Hyperbaric Medicine Fellowship, Department of Emergency Medicine, University of California, San Diego, School of Medicine, San Diego, California Christopher Van Tilburg, MD Editor, Wilderness Medicine; Medical Committee Member, Mountain Rescue Association John Walden, MD, DTM&H Professor and Associate Dean, Department of Family and Community Health, Marshall University Joan C. Edwards School of Medicine, Huntington, West Virginia

xi

Helen L. Wallace, BS Department of Biology, Portland State University, Portland, Oregon Andrew Wang, MD Associate Professor of Medicine, Division of Cardiovascular Medicine, Duke University School of Medicine, Durham, North Carolina David A. Warrell, MA, DM, DSc, FRCP, FRCPE, FMedSci Emeritus Professor of Tropical Medicine, Nuffield Department of Clinical Medicine, and Honorary Fellow of St. Cross College, University of Oxford; Consultant Physician (Acute General Medicine and Infectious Diseases), Oxford Radcliffe Hospitals NHS Trust, Oxford, United Kingdom Eric A. Weiss, MD, FACEP Assistant Professor, Division of Emergency Medicine, Department of Surgery; Director, Wilderness Medicine Fellowship; and Medical Director, Office of Disaster Planning and Service Continuity, Stanford University School of Medicine, Stanford; Medical Director, Emergency Medical Services, San Mateo County, California Lynn E. Welling, MD Adjunct Assistant Professor of Military and Emergency Medicine, Uniformed Services University of the Health Sciences F. Edward Hébert School of Medicine, Bethesda, Maryland; Assistant Clinical Professor of Medicine, Department of Emergency Medicine, University of California, San Diego, School of Medicine; Staff Emergency Physician, Naval Medical Center San Diego; Staff Emergency Physician, Scripps Mercy Hospital and Medical Center, San Diego; Staff Emergency Physician, Sharps Grossmont Hospital, La Mesa, California James A. Wilkerson III, MD Merced Pathology Medical Group, Inc. (Retired), Merced, California Knox Williams, MS Director (Retired), Colorado Avalanche Information Center, Boulder, Colorado Sarah R. Williams, MD, FACEP Director, Emergency Department Ultrasound, Division of Emergency Medicine, Department of Surgery, Stanford University School of Medicine, Stanford, California

Foreword More than a decade ago, I had the good fortune to be searching for new species of flowering lianas in the remote jungles of central Suriname. A tropical downpour had just ended, and we wandered through a forest still dripping from the rain shower. The air had become cool and buoyant, perfumed with a panoply of enticing floral scents. Within a few hours of collecting, however, the heat had once again set into the equatorial lowland forest. Members of our small expedition sat down underneath the shade of a large bergibita tree on granitic stones covered with a fine green moss to take a rest in the torpid jungle atmosphere. As I struggled to fish granola out of my waterproof daypack, the botanist accompanying me cursed and jumped to his feet. “Something bit me!” he exclaimed. We searched the site but never found the offending creature. Only two small pinpoints on the skin of his ankle, separated by no more than a couple of millimeters, could scarcely be discerned, nothing remotely commensurate to the pain experienced by my friend. I asked our Indian guide—a shaman of the Trio tribe and a man of few words—what had happened. He replied, “Mwe,” the Trio word for spider. In short order, the botanist became very ill. He became dizzy and dropped to his knees. Delirium set in as he begged for water and crawled into a nearby shallow stream. Nausea set in, accompanied by dry heaves. This famously stoic scientist was reduced to sobbing from the excruciating pain, which seemed to wrack every joint of his body. My first aid kit offered no remedy with which we could be hopeful of improvement. My colleague’s condition steadily deteriorated. Fighting the urge to panic, I tried to determine the best course of action. Should I attempt to move him? Leave him and seek help? We were dozens of miles of trackless jungle away from any Western-trained health care professional or even the most rudimentary pharmaceuticals or supportive care. I was terrified and powerless to help my friend. I felt a presence and looked up from my incapacitated colleague onto the stream bank. There sat the medicine man, serenely surveying the scene with calm, knowing eyes. I had hired him to teach us the indigenous names of the plants we were collecting, never anticipating that we might need his healing services as well. Working in the Amazon as an ethnobotanist for 20 years, I have developed an immense respect for the traditional knowledge of these ancient healers. I asked the shaman if my ailing colleague would die. The Indian grunted as he pointed his chin at the botanist. “Not going to die,” he said, in his language. “Going to suffer, but not die.” His words began to lift my weight of concern, but were soon contradicted by the pitiful cries and moans of my colleague. “Well,” I urgently asked, “do you know of any therapies that can help him?”

“Yes,” he nodded, standing up from his resting place on the ground and brushing coarse sand off his red breechcloth. “Give me your machete.” He took the knife and disappeared into the bush. About three minutes later, he returned with two meters of a dull brown liana stem from the Philodendron family. The medicine man walked into the stream, turned the botanist onto his back, sliced the liana into four pieces and carefully let the liana sap drip onto the bite marks on the victim’s ankles. In less than 10 minutes, our patient felt well enough to sit up. His dizziness and nausea had diminished substantially. Within a half-hour, we were able to help him back to camp, where he spent the rest of the day recuperating in his hammock. He dozed fitfully for most of the afternoon, awoke in time to eat a hearty dinner by the campfire, and then slept through the night. By the next morning, he seemed back to normal. This episode is likely how most of wilderness medicine was originally practiced and how, in more than a few remote corners of the world, it is still practiced today. For most of human history and prehistory, there was not a significant presence of doctors, validated drugs, or hospitals. There were, of course, healers (e.g., shamans, herbalists, bonesetters) and remedies (usually plants, but also other substances ranging from molds to insects to honey to soils); these evolved from trial and error to our current scientific approach. So it was a supreme irony when Paul Auerbach and his colleagues coalesced the field of Wilderness Medicine two and a half decades ago—clearly a case of back to the future! In my world of ethnobotany, work and adventure carry me far from medical security. I have the good fortune to work in remote places where much of Western medicine has never been available. This is not thrill seeking—it is my professional calling. For large portions of my life, I live in the wilderness. Thus, I regularly witness the practice of wilderness medicine. It is at once remarkable and frightening—remarkable in the sense that indigenous healers know so many things from which we could derive enormous benefit and frightening because their medicine is laden with empiricism, mysticism, and lack of what we would consider detailed scientific substantiation. Some would call it “primitive,” but that shouldn’t be taken to mean it is incorrect. In fact, time and time again, as in the case of the spider bite, I have seen it heal. In an age in which medicine becomes increasingly specialized and enhanced by technology, I like to think of practitioners of wilderness medicine as masters of “Renaissance medicine.” They must be willing to abandon urban trappings and tools to get “down and dirty.” Furthermore, they must know much more than they learned in medical school. If you are in a mountaineering accident, do you want the first healer on the scene to be a doctor whose expertise is confined to cancer? If you fall out of a tree and break your bones, do you want the first responder to be someone who has never attended a fracture?

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When my wife was bitten by a copperhead snake in Virginia several years ago, she was taken by ambulance to a major, wellequipped suburban hospital. The good news was that she had no end of doctors eager to examine her. The bad news was that none of them had ever treated or even seen a snakebite, hence their interest in having a look! I was able to track down Paul Auerbach, who talked the treating physician through the necessary treatment. I had known enough to turn to my friend from the Wilderness Medical Society. Where else in the medical world can you consistently find people adept at treating victims of snakebite, frostbite, lightning strikes, volcanic eruptions, and scorpion envenomation? This is not to argue that wilderness medicine is restricted solely to treating obscure afflictions or problems of the past. The marriage of traditional wisdom with cutting edge science offers new and important potential for better treatment of everything from high-altitude pulmonary and cerebral edema to

heat stroke. These new approaches may incorporate everything from wisdom of local peoples to biodesign of novel medical devices. Remember that doctors now place leeches on healing wounds, which is more effective than drugs designed by modeling proteins with computers. We live in an interesting epoch in which our societies are increasingly urban and technology oriented. Yet, something in our souls yearns for regular and sustained contact with the wonders of Mother Nature. The demand for ecotourism is expanding at an astounding rate. Doctors, nurses, and other health care providers simply must know what to do when confronted by the inevitable afflictions that result from our species’ collisions with the natural world. Mark J. Plotkin, PhD Amazon Conservation Team www.amazonteam.org

Preface I am very excited to present this fifth edition of Wilderness Medicine, which supports a phase of tremendous growth and excitement in the discipline. As man extends into remote reaches of the globe and large populations encounter environmental changes at an ever-increasing rate, this medicine of exploration, adventure, travel, and disaster response has become indispensable. Although much of the medicine practiced in remote areas or under environmental extremes is emergency in nature, and local conditions and considerations by necessity dominate, the field of wilderness medicine has advanced beyond the exciting rescues of extreme alpinists and survivalists. It has expanded in scope to include the practice of medicine in situations of constrained resources, during times of catastrophe, and often in impoverished countries. In noble responses to events that generate urgent and profound medical needs, practitioners skilled in wilderness medicine have become rescuers and leaders noted for their resourcefulness and rugged practicality. Because humans continually try to dominate the landscape in their disregard for the environment and fellow man, nature is the force with which we must constantly reckon. All major hazards ultimately involve the power and energy of mighty winds, harsh solar radiation, extreme cold, and the like. I am particularly gratified that wilderness medicine is a discipline on the verge of becoming a specialty, on its own and possessed of profound relevance. Wilderness medicine is advanced in basic science laboratories and by academicians who witness their efforts translated under harsh field conditions within hazardous wilderness areas above, upon, and under every natural surface on Earth, and soon, in space. We might investigate the application of protein kinase inhibition to treat reperfusion injury in the mitochondria of endothelial cells, then find willing volunteers on expeditions to investigate its application for prevention and treatment of frostbite. Curiosity about the stinging mechanism of jellyfish, combined with observation of clownfish protected with a host anemone, leads to clinical trials in which volunteers demonstrate the efficacy of a topical jellyfish sting inhibitor. Drugs designed to treat hypertension and sexual dysfunction are evaluated for potency in the prevention and treatment of high altitude pulmonary edema. Cooling devices designed for elite athletes may save the lives of firefighters. On mountaintops, within jungle canopies, and in arid canyonlands, we seek to understand the forces of pressure, temperature, and weather, so that we may enjoy better health and safer journeys. The growth of wilderness medicine as a field of study and practice is remarkable only with respect to the brief history of the term. When Ed Geehr, Ken Kizer, and I dreamed up the Wilderness Medical Society, it was not a brainstorm, but an obvious response to pent-up demand. There are innumerable physicians, allied health professionals, rescuers, and laypersons dedicated by profession and avocation to wilderness environments. The current status of wilderness medicine is characterized by increasing interest from the medical community as

structure is imposed on persons and institutions possessing expertise. Wilderness medicine is now well established, so training programs are being tailored to correspond to the educational level and certifications of trainees and practitioners. However, as we attempt to apply urban standards of hygiene and health to every environment in which man has a consistent presence, wilderness medicine must never lose sight of its origin in the medical concerns existing in true wilderness territories. Herein lies the essential nature and appeal of the specialty. Is wilderness medicine important in an age of widespread communicable disease and potential pandemics? How many people are victims of shark attacks versus how many persons suffer from diabetes? How many climbers reach the Seven Summits versus how many elders are stricken with congestive heart failure? How many children fall prey to high altitude pulmonary edema versus how many infants acquire HIV from their mothers? The inquisitive mind seeks not to partition what we learn from our test tubes and urban patients, but to constantly integrate and extrapolate. I am thoroughly convinced that wilderness medicine supports some of the most practical education and skills acquisition in the health care profession. Medicine and its science are intricate, so what is learned in one venue is commonly applicable across a wide spectrum of human disease. We owe it to our hearts and minds to pursue every aspect of medicine that challenges our imaginations and ingenuity. As an additional benefit, it is a joy to observe a healer normally bound to an urban existence lifted in spirit by recognition that medicine applies equally well to adventure, travel, and discovery. Furthermore, while wilderness medicine was not conceived solely to be medicine in the absence of customary resources, it has to a certain extent evolved that way. Wilderness medicine is not practiced in wilderness hospitals, but in the field—not on paved pathways, but in forests, at base camp, and on the beach. We will advance the science, increase the teaching, and improve the practice of wilderness medicine. Even while wilderness medicine is often practiced solo, it brings people together, bonded by their community of search and rescue, medicine, and love of the outdoors. We will reach out in public health and service related to wilderness medicine. Many global health issues are in part within the purview of wilderness medicine. In response to these, and other, scourges of mankind, practitioners of wilderness medicine will bring their expertise to bear on developing sensible solutions that can actually be implemented. Injury prevention will have its day in a more concerted effort to make the outdoors safe for those who choose or need to enter it. In this new age of medicine, when diagnostics and therapeutics in the hospital have evolved to molecular and nano methods, what is the impact of technology on wilderness medicine? At the true wilderness level, not much. Technology can mitigate risk only to a certain degree. In the field, there is not yet computed tomography or magnetic resonance imaging, and I do not foresee a wilderness intensive care unit, notwithstand-

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ing the space station. Perhaps when we have miniaturized everything, we will occasionally interpret ultrasounds and read brain waves on mountains and glaciers, but that will not change the essence of making do when all you have is your senses and courage. So, downstream wilderness medicine is very hands-on and frequently improvisational. One need only consider what was valuable in the wake of recent tidal waves, hurricanes, mudslides, and earthquakes to appreciate our increasing need for people who practice medicine with very little on short notice under extreme environmental stress. Much in this volume is new and enhanced. In deference to current political conflicts that are perpetrated in rugged environments, it has become appropriate to introduce concepts related to the military, so that medics are familiar with considerations of tactics. Because astronauts seek to expand their boundaries, unique medical concerns of this new wilderness are once again part of the discussion. Competitive athletes take their marathons, races, and survival events farther into the backcountry, so there is new emphasis on adventure sports and the medicine necessary to support them. When the first edition of this book was published, my colleagues and I dove, climbed, soared, and trekked with impunity. These days, our lungs and limbs talk back to us, and we appreciate the opportunities for contemplation as much as challenges. Who among us will not grow older or develop functional limitations? The wilderness is for everyone and should not be limited to only the hardiest and most intrepid. Therefore, I have added chapters on pre-existing conditions, chronic illnesses, and persons with disabilities. More in-depth coverage of “traditional” wilderness medicine topics, such as acclimatization, natural hazards, search and rescue, and poisonous and venomous creatures is ably provided by a very dedicated group of experts. To allow sufficient space

for all the upgrades, the references have been moved to an accompanying DVD-ROM. As in previous editions, I am greatly indebted to my remarkable wife Sherry and children, Brian, Lauren, and Dan; to all of the tireless contributors; and to the supportive and gracious Todd Hummel, Jennifer Shreiner, and Michael Goldberg at Elsevier. I practice and preach wilderness medicine with passion—for medicine, for my patients, for my colleagues, and for the wilderness. I am perpetually amazed by remarkable tales of adversity, endurance, rescue, faith, the will to live, and the indomitable human spirit. That is most fitting for the setting in which these events occur, for at most times in the wilderness, we are able to appreciate everything that is natural and wonderful upon this Earth. As you peruse this book, take a few moments to reflect upon the images of the wilderness that grace the opening of the sections. Whether you stand before a majestic mountain, descend into a vast blue ocean, walk softly through a coniferous forest, or lie in a misty moonlit meadow and count shooting stars, you are at peace. Imagine the soothing sounds of a river, the caress of a snowflake, or the penetrating warmth of a desert rock. Wilderness is our greatest blessing, for it exists to support life, yet bestows uncommon beauty. We may manipulate and seek to conquer our environment, but in the end, it is always we who must adapt to the forces of nature. Wilderness medicine, then, exists on the premise that humans will encounter forces beyond their control. As we learn to keep ourselves healthy and whole in the outdoors, we come to appreciate the essences of healing and renewal. In medicine, there is service to the living. In wilderness medicine, there is service to humankind and our precious habitat. Paul S. Auerbach, MD, MS

Photo credits for cover images and section openers Cover: Polar Touch, Manitoba, photo by Tim Floyd, MD; Thomserku Silouette, photo by Lanny Johnson; clownfish on shipwreck, Truk Lagoon, Federated States of Micronesia, photo by Ian Jones, MD; barrier reef, south of Papua New Guinea, photo by Ian Jones, MD; sandstorm, Sossusvlei Sand Dunes, Namibia, photo by Cyril Mazansky, MD; White Mountains, New Hampshire, photo by Tim Floyd, MD; Yosemite, photo by Mathias Schar, MD. Section One (page 1): Exum Ridge, photo by Lanny Johnson; Inca Trail, photo by Paul Auerbach, MD. Section Two (page 109): Sandstorm, Sossusvlei Sand Dunes, Namibia, photo by Cyril Mazansky, MD; Black and White or Not, photo by Gordon Giesbrecht, PhD. Section Three (page 285): Emerald Pool, photo by Lanny Johnson. Section Four (page 399): Helicopter rappel at Mt. Moran, photo by Lanny Johnson; moon over Ama Dablam, photo by Lanny Johnson. Section Five (page 693): View of Ama Dablam from Kunde, photo by Lanny Johnson; Salt Flats, photo by Daniel Ryan, MD. Section Six (page 891): Coastal brown bear sow and cubs enjoy a salmon meal at McNeil River, Alaska, photo by Luanne Freer, MD; tundra wolf, photo by Donna Nayduch, RN, MSN, ACNP (www.wolfsanctuary.net). Section Seven (page 1251): Flower, photo by Daniel Ryan, MD; Germany (leaves), photo by Mathias Schar, MD. Section Eight (page 1367): Havasupai, photo by Mathias Schar, MD. Section Nine (page 1567): Squid eye, photo by Paul Auerbach, MD; oceanic whitetip shark, Kona, Hawaii, photo by Marty Snyderman. Section Ten (page 1807): Crystal Crag from Mammoth Crest, photo by Mathias Schar, MD; Yosemite, photo by Mathias Schar, MD. Section Eleven (page 1893): White Mountains, New Hampshire, photo by Tim Floyd, MD; Khunde camp, photo by Lanny Johnson. Section Twelve (page 1985): Climber on Middle Grand, photo by Lanny Johnson; Aurora Borealis, Manitoba, photo by Tim Floyd, MD. Section Thirteen (page 2183): Golden eagle, Idaho, photo by Tim Floyd, MD; Death Canyon, Grand Teton National Park, photo by Tim Floyd, MD.

1

High-Altitude Medicine Peter H. Hackett and Robert C. Roach

Millions of people visit recreation areas above 2400 m in the American West each year. Hundreds of thousands visit central and south Asia, Africa, and South America, many traveling to altitudes over 4000 m.311 In addition, millions live in large cities above 3000 m in South America and Asia. The population in the Rocky Mountains of North America has doubled in the past decade. Increasingly, physicians and other health care providers are confronted with questions of prevention and treatment of high-altitude medical problems (Box 1-1) as well as the effects of altitude on preexisting medical conditions. Despite advances in high-altitude medicine, significant morbidity and mortality persist (Table 1-1). Clearly, better education of the population at risk and of those advising them is essential. This chapter reviews the basic physiology of ascent to high altitude, as well as the pathophysiology, recognition, and management of medical problems associated with high altitude. The clinical issues likely to be encountered in lowlanders visiting high-altitude locations are emphasized, and medical problems of people living at high altitude are discussed (see Box 1-1).


DEFINITIONS High Altitude (1500 to 3500 m*) The onset of physiologic effects of diminished inspiratory oxygen pressure (Pio2) includes decreased exercise performance and increased ventilation (lower arterial Pco2) (Box 1-2). Minor impairment exists in arterial oxygen transport (arterial oxygen saturation [Sao2] at least 90%), but arterial Po2 is significantly diminished. Because of the large number of people who ascend rapidly to 2500 to 3500 m, high-altitude illness is common in this range (Table 1-2, and see Table 1-1).

Very High Altitude (3500 to 5500 m) Maximum Sao2 falls below 90% as the arterial Po2 falls below 60 mm Hg (Table 1-3 and Fig. 1-1). Extreme hypoxemia may occur during exercise, during sleep, and in the presence of highaltitude pulmonary edema or other acute lung conditions. Severe altitude illness occurs most commonly in this range.

Extreme Altitude (above 5500 m) Marked hypoxemia, hypocapnia, and alkalosis are characteristic of extreme altitudes. Progressive deterioration of physiologic function eventually outstrips acclimatization. As a result, no *To convert meters to feet, multiply meters × 3.2808. To convert feet to meters, multiply feet × .3048.

2

permanent human habitation occurs above 5500 m. A period of acclimatization is necessary when ascending to extreme altitude; abrupt ascent without supplemental oxygen for other than brief exposures invites severe altitude illness.


ENVIRONMENT AT HIGH ALTITUDE

Barometric pressure falls with increasing altitude in a logarithmic fashion (see Table 1-2). Therefore, the partial pressure of oxygen (21% of barometric pressure) also decreases, resulting in the primary insult of high altitude: hypoxia. At approximately 5800 m, barometric pressure is one-half that at sea level, and on the summit of Mt. Everest (8848 m), the Pio2 is approximately 28% that at sea level (see Figure 1-1 and Table 1-2). The relationship of barometric pressure to altitude changes with the distance from the equator. Thus, polar regions afford greater hypoxia at high altitude in addition to extreme cold. West467 has calculated that the barometric pressure on the summit of Mt. Everest (27° N latitude) would be about 222 mm Hg instead of 253 mm Hg if Everest were located at the latitude of Mt. McKinley (62° N). Such a difference, he claims, would be sufficient to render an ascent without supplemental oxygen impossible. In addition to the role of latitude, fluctuations related to season, weather, and temperature affect the pressure–altitude relationship. Pressure is lower in winter than in summer. A lowpressure trough can reduce pressure 10 mm Hg in one night on Mt. McKinley, making climbers awaken “physiologically higher” by 200 m. The degree of hypoxia is thus directly related to the barometric pressure, not solely to geographic altitude.467 Temperature decreases with altitude (an average of 6.5° C per 1000 m [3.6° F per 1000 ft]), and the effects of cold and hypoxia are generally additive in provoking both cold injuries and highaltitude pulmonary edema.351,462 Ultraviolet light penetration increases approximately 4% per 300-m gain in altitude, increasing the risk of sunburn, skin cancer, and snowblindness. Reflection of sunlight in glacial cirques and on flat glaciers can cause intense radiation of heat in the absence of wind. The authors have observed temperatures of 40° to 42° C (104° to 108° F) in tents on both Mt. Everest and Mt. McKinley. Heat problems, primarily heat exhaustion, are often unrecognized in this usually cold environment. Physiologists have not yet examined the consequences of heat stress or rapid, extreme changes in environmental temperature combined with the hypoxia of high altitude.

Chapter 1: High-Altitude Medicine Above the snow line is the “high-altitude desert,” where water can be obtained only by melting snow or ice. This factor, combined with increased water loss through the lungs from increased respiration and through the skin, commonly results in dehydration that may be debilitating. Thus, the high-altitude environment imposes multiple stresses, some of which may contribute to or be confused with the effects of hypoxia.

BOX 1-1. Medical Problems of High Altitude LOWLANDERS ON ASCENT TO HIGH ALTITUDE

Acute hypoxia High-altitude headache Acute mountain sickness High-altitude cerebral edema Cerebrovascular syndromes High-altitude pulmonary edema High-altitude deterioration Organic brain syndrome Peripheral edema Retinopathy Disordered sleep Sleep periodic breathing High-altitude pharyngitis and bronchitis Ultraviolet keratitis (snowblindness) Exacerbation of preexisting conditions

3


ACCLIMATIZATION TO HIGH ALTITUDE

Rapid ascent from sea level to the altitude at the summit of Mt. Everest (8848 m) causes loss of consciousness in a few minutes and death shortly thereafter. Yet climbers ascending Mt. Everest over a period of weeks, without supplemental oxygen, have experienced only minor symptoms of illness. The process by which individuals gradually adjust to hypoxia and enhance survival and performance is termed acclimatization. A complex series of physiologic adjustments increases oxygen delivery to cells and also improves their hypoxic tolerance. The severity

BOX 1-2. Glossary of Physiologic Terms PB Po2 Pio2

LIFE-LONG OR LONG-TERM RESIDENTS OF HIGH ALTITUDE

Chronic mountain sickness (chronic mountain polycythemia) High-altitude pulmonary hypertension, with or without right heart failure Problems of pregnancy: preeclampsia, hypertension, and low-birth-weight infants Exacerbation of common illnesses, such as lung disease

Barometric pressure* Partial pressure of oxygen Partial pressure of inspired oxygen (0.21 × [PB − 47 mm Hg]) (47 mm Hg = vapor pressure of H2O at 37° C) Po2 in alveolus Pco2 in alveolus Po2 in arterial blood Pco2 in arterial blood Arterial oxygen saturation (HbO2 ÷ total Hb × 100) Respiratory quotient (CO2 produced ÷ O2 consumed) PAo2 = Pio2 − (PAco2/R)

PAo2 PAco2 Pao2 Paco2 Sao2% R Alveolar gas equation

*Pressures are expressed as mm Hg (1 mm Hg = 1 torr).

TABLE 1-1. Incidence of Altitude Illness in Various Groups

STUDY GROUP Western State Visitors Mt. Everest Trekkers Mt. McKinley Climbers Mt. Rainier Climbers Mt. Rosa, Swiss Alps Indian Soldiers Aconcagua Climbers

MAXIMUM ALTITUDE REACHED (m)

AVERAGE RATE OF ASCENT*

3500

1–2

15,000

~2000 ~2500 ~≥3000 3000–5200

5500

1200

3000–5300

6194

1–2 (fly in) 10–13 (walk in) 3–7

18–20 22 27–42 47 23 30–50 30

4392

1–2

2850 4559 3000–5500

2850 4559 5500

3300–5800

6962

NUMBER AT RISK PER YEAR

SLEEPING ALTITUDE (m)

30 million

10,000 †

Unknown 4200

3000

PERCENT WITH HAPE AND/OR HACE

REFERENCES

0.01

183

1.6 0.05 2–3

155 — 321 147

67

—

250

1–2 2–3 1–2

7 27

— 5 2.3–15.5

273 83, 273, 401 420, 421

2–8

39 (LLS > 4)

2.2

341

PERCENT WITH AMS

†

*Days to sleeping altitude from low altitude. † Reliable estimate unavailable. AMS, acute mountain sickness; HACE, high-altitude cerebral edema; HAPE, high-altitude pulmonary edema; LLS, Lake Louise score.

PART ONE: MOUNTAIN MEDICINE

m Sea level 1,000 1,219 1,500 1,524 1,829 2,000 2,134 2,438 2,500 2,743 3,000 3,048 3,353 3,500 3,658 3,962 4,000 4,267 4,500 4,572 4,877 5,000 5,182 5,486 5,500 5,791 6,000 6,096 6,401 6,500 6,706 7,000 7,010 7,315 7,500 7,620 7,925 8,000 8,230 8,500 8,534 8,839 8,848 9,000 9,144 9,500 10,000

ft

PB

PIO2

Sea level 3,281 4,000 4,921 5,000 6,000 6,562 7,000 8,000 8,202 9,000 9,843 10,000 11,000 11,483 12,000 13,000 13,123 14,000 14,764 15,000 16,000 16,404 17,000 18,000 18,045 19,000 19,685 20,000 21,000 21,325 22,000 22,966 23,000 24,000 24,606 25,000 26,000 26,247 27,000 27,887 28,000 29,000 29,029 29,528 30,000 31,168 32,808

759.6 678.7 661.8 640.8 639.0 616.7 604.5 595.1 574.1 569.9 553.7 536.9 533.8 514.5 505.4 495.8 477.6 475.4 460.0 446.9 442.9 426.3 419.7 410.2 394.6 393.9 379.5 369.4 364.9 350.7 346.2 337.0 324.2 323.8 310.9 303.4 298.6 286.6 283.7 275.0 265.1 263.8 253.0 252.7 247.5 242.6 230.9 215.2

149.1 132.2 128.7 124.3 123.9 119.2 116.7 114.7 110.3 109.4 106.0 102.5 101.9 97.9 95.9 93.9 90.1 89.7 86.4 83.7 82.9 79.4 78.0 76.0 72.8 72.6 69.6 67.5 66.5 63.6 62.6 60.7 58.0 57.9 55.2 53.7 52.6 50.1 49.5 47.7 45.6 45.4 43.1 43.1 42.0 40.9 38.5 35.2

FIO2 AT SL 0.209 0.185 0.180 0.174 0.174 0.167 0.164 0.161 0.155 0.154 0.149 0.144 0.143 0.137 0.135 0.132 0.126 0.126 0.121 0.117 0.116 0.111 0.109 0.107 0.102 0.102 0.098 0.095 0.093 0.089 0.088 0.085 0.081 0.081 0.077 0.075 0.074 0.070 0.069 0.067 0.064 0.064 0.060 0.060 0.059 0.057 0.054 0.049

*Barometric pressure is approximated by the equation PB = Exp(6.6328 − {0.1112 × altitude − [0.00149 × (altitude2)]}), where altitude = terrestrial altitude in meters/1000, or km. Pio2 is calculated as (PB − 47) (where 47 = water vapor pressure at body temperature) × fraction of O2 in inspired air. The equivalent Fio2 at sea level for a given altitude is calculated as Pio2 ÷ (760 − 47). Substituting ambient PB for 760 in the equation allows similar calculations for Fio2 at different altitudes. Exp, Exponent. Meters = feet × .3048. Feet = meters × 3.2808.

SaO2

160

100

140

90 PIO2

120

80

100 80

70

SaO2 (%)

TABLE 1-2. Altitude Conversions Barometric Pressure (PB), Estimated Partial Pressure Inspired Oxygen (PIO2), and the Equivalent Oxygen Concentration at Sea Level (FIO2 at SL)*

Partial pressure oxygen (mm Hg)

4

PaO2

60

60 40 20 0

2000

760

590

4000

6000

50 8000 10000

Altitude (m) 460

306

277

215

Barometric pressure (mm Hg)

Figure 1-1. Increasing altitude results in a decrease in inspired PO2 (PIO2), arterial PO2 (Pao2), and arterial oxygen saturation (SaO2). Note that the difference between PIO2 and PaO2 narrows at high altitude because of increased ventilation, and that SaO2 is well maintained while awake until over 3000 m. (Data from Morris A: Clinical pulmonary function tests: A manual of uniform lab procedures.Intermountain Thoracic Society,1984,and Sutton JR,Reeves JT,Wagner PD,et al: Operation Everest II: Oxygen transport during exercise at extreme simulated altitude. J Appl Physiol 64:1309–1321, 1988, with permission.)

of hypoxic stress, rate of onset, and individual physiology determine whether the body successfully acclimatizes or is overwhelmed. Individuals vary in their ability to acclimatize, no doubt reflecting certain genetic polymorphisms. Some adjust quickly, without discomfort, whereas acute mountain sickness (AMS) develops in others, who go on to recover. A small percentage of people fail to acclimatize even with gradual exposure over weeks. The tendency to acclimatize well or to become ill is consistent on repeated exposure if rate of ascent and altitude gained are similar, supporting the notion of important genetic factors. Successful initial acclimatization protects against altitude illness and improves sleep. Longer-term acclimatization (over weeks) primarily improves aerobic exercise ability. These adjustments disappear at a similar rate on descent to low altitude. A few days at low altitude may be sufficient to render a person susceptible to altitude illness on re-ascent, especially high-altitude pulmonary edema (HAPE). The improved ability to do physical work at high altitude, however, persists for weeks.268 People who live at high altitude during growth and development appear to realize the maximum benefit of acclimatization changes; for example, their exercise performance matches that of persons at sea level.312

Ventilation By reducing alveolar carbon dioxide, increased ventilation raises alveolar oxygen, improving oxygen delivery (Fig. 1-2, and see Figure 1-1). This response starts at an altitude as low as 1500 m (Pio2 = 124 mm Hg; see Table 1-2) and within the first few minutes to hours of high-altitude exposure. The carotid body, sensing a decrease in arterial Po2, signals the central res-

Chapter 1: High-Altitude Medicine

5

TABLE 1-3. Blood Gases and Altitude POPULATION Altitude residents* Acute exposure†

Chronic exposure during Operation Everest II‡ Acclimatized subjects studied during acute exposure to the simulated summit of Everest§

ALTITUDE (m)

ALTITUDE (ft)

PB (mm Hg)

PaO2 (mm Hg)

SaO2 (%)

1,646 2,810 3,660 4,700 5,340 6,140 6,500 7,000 8,000 8,848 8,848

5,400 9,200 12,020 15,440 17,500 20,140 21,325 22,966 26,247 29,029 29,029

630 543 489 429 401 356 346 324 284 253 253

73.0 (65.0–83.0) 60.0 (47.4–73.6) 47.6 (42.2–53.0) 44.6 (36.4–47.5) 43.1 (37.6–50.4) 35.0 (26.9–40.1) 41.1 ± 3.3 — 36.6 ± 2.2 30.3 ± 2.1 30.6 ± 1.4

95.1 (93.0–97.0) 91.0 (86.6–95.2) 84.5 (80.5–89.0) 78.0 (70.8–85.0) 76.2 (65.4–81.6) 65.6 (55.5–73.0) 75.2 ± 6 — 67.8 ± 5 58 ± 4.5 —

PaCO2 (mm Hg) 35.6 33.9 29.5 27.1 25.7 22.0

(30.7–41.8) (31.3–36.5) (23.5–34.3) (22.9–34.0) (21.7–29.7) (19.2–24.8) 20 ± 2.8 — 12.5 ± 1.1 11.2 ± 1.7 11.9 ± 1.4

Data are mean values and (range) or ±SD, where available. All values are for subjects of age 20 to 40 years who were acclimatizing well. *Data from reference 265. † Data from reference 293. ‡ Data from reference 434. § Data from reference 360.

12

10

.

VE (L/min, BTPS)

14

8 PACO2 (mm Hg)

40

35

30

25

SaO2 (%)

100

90

80

0 1 Denver

2

3

4

5

Days at 4300 m

. Figure 1-2. Change in minute ventilation (VE), alveolar carbon dioxide (PACO2), and arterial oxygen saturation (SaO2) during 5 days’ acclimatization to 4300 m. BTPS, Body temperature, ambient pressure, saturated with water vapor. (Modified from Huang SY, Alexander JK, Grover RF, et al: J Appl Physiol 56:602–606, 1984, with permission.)

piratory center in the medulla to increase ventilation. This carotid body function (hypoxic ventilatory response, or HVR) is genetically determined464 but influenced by a number of extrinsic factors. Respiratory depressants such as alcohol and soporifics, as well as fragmented sleep, depress the HVR. Agents that increase general metabolism, such as caffeine and coca, as well as specific respiratory stimulants, such as progesterone242 and almitrine,159 increase the HVR. (Acetazolamide, a respiratory stimulant, acts on the central respiratory center rather than on the carotid body.) Physical conditioning apparently has no effect on the HVR. Numerous studies have shown that a good ventilatory response enhances acclimatization and performance and that a very low HVR may contribute to illness363 (see Acute Mountain Sickness, and High-Altitude Pulmonary Edema). However, over a normal range of values, the HVR is not a reliable predictor of susceptibility to altitude illness. Other factors influence ventilation on ascent to high altitude. As ventilation increases, hypocapnia produces alkalosis, which acts as a braking mechanism on the central respiratory center and limits a further increase in ventilation. To compensate for the alkalosis, within 24 to 48 hours of ascent the kidneys excrete bicarbonate, decreasing the pH toward normal; ventilation increases as the negative effect of the alkalosis is removed. Ventilation continues to increase slowly, reaching a maximum only after 4 to 7 days at the same altitude (see Figure 1-2). The plasma bicarbonate concentration continues to drop and ventilation to increase with each successive increase in altitude. People with lower oxygen saturation at altitude have higher serum bicarbonate values; whether the kidney might be limiting acclimatization or whether this reflects poor respiratory drive is not clear.86 This process is greatly facilitated by acetazolamide (see Acetazolamide Prophylaxis). The paramount importance of hyperventilation is readily apparent from the following calculation: the alveolar Po2 on the summit of Mt. Everest (about 33 mm Hg) would be reached at only 5000 m if alveolar Pco2 stayed at 40 mm Hg, limiting an

6

PART ONE: MOUNTAIN MEDICINE

ascent without supplemental oxygen to near this altitude. Table 1-3 gives the measured arterial blood gases resulting from acclimatization to various altitudes.

Circulation The circulatory pump is the next step in the transfer of oxygen, moving oxygenated blood from the lungs to the tissues.

Systemic Circulation Increased sympathetic activity on ascent causes an initial mild increase in blood pressure, a moderate increase in heart rate and cardiac output, and an increase in venous tone. Stroke volume is low because of decreased plasma volume, which drops as much as 12% over the first 24 hours478 as a result of the bicarbonate diuresis, a fluid shift from the intravascular space, and suppression of aldosterone.30 Resting heart rate returns to near sea level values with acclimatization, except at extremely high altitude. Maximal heart rate follows the decline in maximal oxygen uptake with increasing altitude. As the limits of hypoxic acclimatization are approached, maximal and resting heart rates converge. During Operation Everest II (OEII), cardiac function was appropriate for the level of work performed and cardiac output was not a limiting factor for performance.349,431 Interestingly, myocardial ischemia at high altitude has not been reported in healthy persons, despite extreme hypoxemia. This is partly because of the reduction in myocardial oxygen demand from reduced maximal heart rate and cardiac output. Pulmonary capillary wedge pressure is low, and catheter studies have shown no evidence of left ventricular dysfunction or abnormal filling pressures in humans at rest.140,207 On echocardiography, the left ventricle is smaller than normal because of decreased stroke volume, whereas the right ventricle may become enlarged.431 The abrupt increase in pulmonary artery pressure can cause a change in left ventricular diastolic function, but because of compensatory increased atrial contraction, no overt diastolic dysfunction results.5 In trained athletes doing an ultramarathon, the strenuous exercise at high altitude did not result in left ventricular damage; however, wheezing, reversible pulmonary hypertension, and right ventricular dysfunction occurred in a third of those completing the race and resolved within 24 hours.91

Pulmonary Circulation A prompt but variable increase in pulmonary vascular resistance occurs on ascent to high altitude as a result of hypoxic pulmonary vasoconstriction, which increases pulmonary artery pressure. Mild pulmonary hypertension is greatly augmented by exercise, with pulmonary pressure reaching near-systemic values,140 especially in people with a previous history of highaltitude pulmonary edema.27,93 During OEII, Groves and colleagues140 demonstrated that even when associated with a mean pulmonary artery pressure of 60 mm Hg, cardiac output remained appropriate and right atrial pressure did not rise above sea level values. Thus, right ventricular function was intact in spite of extreme hypoxemia and pulmonary hypertension. Administration of oxygen at high altitude does not completely restore pulmonary artery pressure to sea level values, an indication that increased pulmonary vascular resistance does not result solely from hypoxic vasoconstriction.274 The explanation is likely to be vascular remodeling with medial hypertrophy. See Stenmark and colleagues for an excellent review of molecular and cellular mechanisms of the pulmonary vascular

response to hypoxia, including remodeling.427 Pulmonary vascular resistance returns to normal within days to weeks after descent to low altitude.

Cerebral Circulation Cerebral oxygen delivery is the product of arterial oxygen content and cerebral blood flow (CBF) and depends on the net balance between hypoxic vasodilation and hypocapnia-induced vasoconstriction. CBF increases, despite the hypocapnia, when Pao2 is less than 60 mm Hg (altitude greater than 2800 m). In a classic study, CBF increased 24% on abrupt ascent to 3810 m and then returned to normal over 3 to 5 days.412 More recent studies have shown considerable individual variation39,41,218 and also an impairment of cerebral autoregulation.216,260,450 The individual variation in cerebral blood flow is linked to individual variation in the ventilatory response to hypoxia.2 Regional brain tissue oxygenation assessed by near-infrared spectroscopy reveals mild tissue hypoxia.165,212,388 Overall, global cerebral metabolism is well maintained with moderate hypoxia.87,304

Blood Hematopoietic Responses to Altitude

Ever since the observation in 1890 by Viault453 that hemoglobin concentration was higher than normal in animals living in the Andes, scientists have regarded the hematopoietic response to increasing altitude as an important component of the acclimatization process. On the other hand, hemoglobin concentration apparently has no relationship to susceptibility to high-altitude illness on initial ascent, although this has not been adequately studied. In response to hypoxemia, erythropoietin is secreted and stimulates bone marrow production of red blood cells.409 The hormone is detectable within 2 hours of ascent, nucleated immature red blood cells can be found on a peripheral blood smear within days, and new red blood cells are in circulation within 4 to 5 days. Over a period of weeks to months, red blood cell mass increases in proportion to the degree of hypoxemia. Iron supplementation can be important: women who take supplemental iron at high altitude approach the hematocrit values of men at altitude169 (Fig. 1-3). The increase in hemoglobin concentration seen 1 to 2 days after ascent is due to hemoconcentration secondary to decreased plasma volume, rather than a true increase in red blood cell mass. This results in a higher hemoglobin concentration at the cost of decreased blood volume, a tradeoff that might impair exercise performance. Longer-term acclimatization leads to an increase in plasma volume as well as in red blood cell mass, thereby increasing total blood volume. Overshoot of the hematopoietic response causes excessive polycythemia, which may actually impair oxygen transport because of increased blood viscosity. Although the “ideal” hematocrit at high altitude is not established, phlebotomy is often recommended when hematocrit values exceed 60% to 65%. During the American Medical Research Expedition to Mt. Everest (AMREE), hematocrit was reduced by hemodilution from 58% ± 1.3% to 50.5% ± 1.5% at 5400 m with no decrement in maximal oxygen uptake and an increase in cerebral functioning.393

Oxyhemoglobin Dissociation Curve The oxyhemoglobin dissociation curve (ODC) plays a crucial role in oxygen transport. Because of the sigmoidal shape of the

Chapter 1: High-Altitude Medicine

50

100

Men

7

~ No change

Women (Fe)

~10% Decrease

80

46 Women (
Fe)

44 60 42 Sea level

40 1

20

40

60

SaO2 (%)

Hematocrit (%)

48

40

Days at 4300 Meters

Figure 1-3. Hematocrit changes on ascent to altitude in men and in women,with and without supplemental iron (Fe).(Modified from Hannon JP,Chinn KS,Shields JL:Fed Proc 28:1178–1184, 1969, with permission.)

B

20

A

0

curve, Sao2% is well maintained up to 3000 m, despite a significant decrease in arterial Po2 (see Figure 1-1). Above that altitude, small changes in arterial Po2 result in large changes in arterial oxygen saturation (Fig. 1-4). The oxygen saturation determines arterial oxygen transport, but the Po2 determines diffusion of oxygen from the capillary to the cell. In 1936, Ansel Keys and colleagues230 demonstrated an in vitro right shift in the position of the ODC at high altitude, a shift that favors release of oxygen from blood to the tissues. This change occurs because of the increase in 2,3-diphosphoglycerate (2,3-DPG), which is proportional to the severity of hypoxemia. In vivo, however, this is offset by alkalosis, and at moderate altitude little net change occurs in the position of the ODC. On the other hand, the marked alkalosis of extreme hyperventilation, as measured on the summit and simulated summit of Mt. Everest (Pco2 8 to 10 mm Hg, pH > 7.6), shifts the ODC to the left, which facilitates oxygen–hemoglobin binding in the lung, raises Sao2%, and is thought to be advantageous.391 This concept is further supported by observing that when people with a very left-shifted ODC, caused by an abnormal hemoglobin (Andrew-Minneapolis), were taken to moderate (3100 m) altitude, they had less tachycardia and dyspnea and remarkably had no decrease in exercise performance.175 High-altitude adapted animals also have a left-shifted ODC.

Tissue Changes The next link in the oxygen transport chain is tissue oxygen transfer, which depends on capillary perfusion, diffusion distance, and driving pressure of oxygen from the capillary to the cell. The final link, then, is use of oxygen within the cell. Banchero15 has shown that capillary density in dog skeletal muscle doubled in 3 weeks at a barometric pressure of 435 mm Hg. A recent study in humans noted neither change in capillary density, nor in gene expression thought to enhance muscle vascularity.267 Ou and Tenney334 revealed a 40% increase in mitochondrial number but no change in mitochondrial size, whereas the study of Oelz and colleagues332 showed that high-altitude climbers had normal mitochondrial density. A significant drop

0

20

40

60

80

100

120

PaO2 (mm Hg)

Figure 1-4. Oxyhemoglobin dissociation curve showing effect of 10 mm Hg decrement in PaO2 on arterial oxygen saturation at sea level (A) and near 4400 m (B). Note the much larger drop in SaO2 at high altitude. (Modified from Severinghaus JW, Chiodi H, Eger EI, et al: Circ Res 19:274–282, 1966, with permission.)

in muscle size is often noted after a high-altitude expedition due to net energy deficit,267,270 and it results in shortening of the diffusion distance for oxygen. This occurs in spite of no de novo synthesis of capillaries or mitochondria, yet results in increased capillary density and ratio of mitochondrial volume to contractile protein fraction, which are primarily a result of the atrophy.267,270

Sleep at High Altitude Disturbed sleep is common at high altitude. Its cause appears to be multifactorial. Reflecting the great interest in sleep in general, more than 140 papers have addressed sleep at altitude in the last 10 years; a complete discussion is outside our purview. The interested reader is referred to recent reviews and online databases (Medline).454,463 Nearly all subjects complain of disturbed sleep at high altitude, with severity increasing with the altitude. At moderate altitude, sleep architecture is changed, with reduction in stage 3 and 4 sleep, increase in stage 1 time, and little change in stage 2. Overall, there is a shift from deeper sleep to lighter sleep. In addition, more time is spent awake, with significantly increased arousals. Authors have reported either slightly less rapid eye movement (REM) time, or no change in REM compared to low altitude. REM sleep may improve over time at altitude.232 The subjective complaints of poor sleep are out of proportion to the small reduction (if any) in total sleep time, and appear to be due to sleep fragmentation. With more extreme hypoxia, sleep time was dramatically short-

8

PART ONE: MOUNTAIN MEDICINE

Placebo

Sleep saturation at 5360 m 100 80 SaO2 %

Respiratory Pattern 100 80 60 40

SaO2 (%)

60 40

Arrival Acclimatized

20 Acetazolamide

0

Time asleep in minutes

Respiratory Pattern 100 80 SaO2 (%) 60 40

Figure 1-5. Respiratory patterns and arterial oxygen saturation (SaO2) with placebo and acetazolamide in two sleep studies of a subject at 4200 m. Note pattern of hyperpnea followed by apnea during placebo treatment,which is changed with acetazolamide.(Modified from Hackett PH, Roach RC, Harrison GL, et al: Am Rev Respir Dis 135:896–898, 1987, with permission.)

ened and arousals increased, without a change in ratio of sleep stages but with a reduction in REM sleep.8 The mechanisms of this change in sleep architecture and fragmentation are poorly understood. Periodic breathing appears to play only a minor role in altering sleep architecture at high altitude.390 The arousals have been linked to periodic breathing in some studies but not others. Other factors might include change in circadian rhythm and perhaps body temperature.82 Problematic sleep is quite variable, with predisposing factors such as obesity explaining a degree of susceptibility to both deranged sleep and sleep-disordered breathing in some individuals.125 Recent studies of infants and children488 and athletes in simulated altitude devices used for training also revealed deranged sleep quality in these groups.233,234,337 Although deranged sleep is a frequent complaint in high-altitude visitors, it seems to have little relation to susceptibility to altitude illness or other serious problems. Symptomatic treatment that avoids respiratory depression is safe. (See Treatment under Acute Mountain Sickness section.)

Periodic Breathing Periodic breathing is most common in early and light sleep, may occur during wakefulness when drowsy, and does not occur in REM sleep. The pattern is characterized by hyperpnea followed by apnea (Fig. 1-5), and it is caused by a battle for control of breathing between the peripheral chemoreceptors (carotid body) and the central respiratory center. Respiratory alkalosis during the hyperpnea acts on the central respiratory center, causing apnea. During apnea, Sao2% decreases, carbon dioxide increases, and the carotid body is stimulated, causing a recurrent hyperpnea and apnea cycle. The apnea is central, not associated with snoring, and with absence of rib cage movement. Persons with a high hypoxic ventilatory response have more periodic breathing, with mild oscillations in Sao2%,246 whereas

50 100 150 200 250 300 350 400 450 500

Figure 1-6. Sleep oxygenation improves with acclimatization to same altitude. Top line is maximum and bottom line is minimum SaO2 in an acclimatized person. Shaded area shows maximum and minimum SaO2 values for new arrival at 5360 m (17,581 feet). (Modified from Sutton JR, Houston CS, Mansell AL, et al: N Engl J Med 301:1329–1331, 1979, with permission.)

persons with a low hypoxic ventilatory response have more regular breathing overall but may suffer periods of apnea with extreme hypoxemia distinct from periodic breathing.159 As acclimatization progresses, periodic breathing lessens but does not disappear, especially over 5000 m, and Sao2% increases (Fig. 1-6).8,432 Periodic breathing has not been implicated in the etiology of high-altitude illness, but nocturnal oxygen desaturation has been implicated.111,121 Eichenberger and colleagues have also reported greater periodic breathing in persons with HAPE, secondary to lower Sao2%.108 As with fragmented sleep, the intensity of periodic breathing is quite variable. Total sleep time with periodic breathing can vary from 1% to over 90%.494 Most studies report no association between periodic breathing and AMS. This may relate to the fact that persons with periodic breathing tend to have higher HVR, and greater average ventilation and oxygenation.463

Pharmaceutical Aids Acetazolamide, 125 mg at bedtime, diminishes periodic breathing and awakenings, improves oxygenation and sleep quality, and is a safe and superior agent to use as a sleeping aid (see Figure 1-5). It has the added benefit of diminishing symptoms of AMS. Other agents include diphenhydramine (Benadryl, 50 to 75 mg) or the short-acting benzodiazepines such as triazolam (Halcion, 0.125 to 0.25 mg) and temazepam (Restoril, 15 mg). Although caution is warranted for any agent that might reduce ventilation at high altitude, some studies have suggested that benzodiazepines in low dosages are generally safe in this situation.104,131,327 Another option is to use both acetazolamide and a benzodiazepine. Bradwell and colleagues55 showed that acetazolamide (500 mg slow-release orally) given with temazepam (10 mg orally) improved sleep and maintained Sao2%, counteracting a 20% decrease in Sao2% when temazepam was given alone. The nonbenzodiazepine hypnotic zolpidem (Ambien, 10 mg) was shown to improve sleep at 4000 m without adversely affecting ventilation.42

Exercise Maximal oxygen consumption drops dramatically on ascent to high altitude (see references 122 and 364 for recent reviews).

Chapter 1: High-Altitude Medicine

40

180

Alveolar

Endurance time · VO2max

160

Arterial 140

30

120 PO2 (torr)

Sea level performance (%)

9

100

20

Mixed venous

Assumed critical PO2

80

Loss of consciousness

. VO2max

10

60

Man on summit PB 253 torr DMO2 100 mL/min/torr

40 0

2

4

6

8

10

12

Days at altitude

. Figure 1-7. On ascent to altitude, VO2max decreases and remains suppressed. In contrast, . endurance time (minutes to exhaustion at 75% of altitude-specific VO2max) increases with acclimatization.(Modified from Maher JT,Jones LG,Hartley LH:J Appl Physiol 37:895–898,1974, with permission.)

. Maximal oxygen uptake (Vo2max) falls from sea level by approximately 10% for each 1000 m of altitude gained above . 1500 m. Those with the highest sea level Vo2max values have . the largest decrement in Vo2max at high altitude, but overall performance at high altitude is not consistently related to sea . level Vo2max.332,358,469 In fact, . many of the world’s elite mountaineers have quite average Vo2max values, in contrast to other endurance athletes.332 Acclimatization at moderate altitudes . enhances submaximal endurance time but not Vo2max 122 (Fig. 1-7). Oxygen transport during exercise at high altitude becomes increasingly dependent on the ventilatory pump. The marked rise in ventilation produces a sensation of breathlessness, even at low work levels. The following quotation is from a highaltitude mountaineer: After every few steps, we huddle over our ice axes, mouths agape, struggling for sufficient breath to keep our muscles going. I have the feeling I am about to burst apart. As we get higher, it becomes necessary to lie down to recover our breath.297 In contrast to the increase in ventilation with exercise, at increasing altitudes in OEII, cardiac function and cardiac output were maintained at or near sea level values for a given oxygen consumption (workload).349 . Recent work has attributed the altitude-induced drop in Vo2max to (1) the lower Pio2, (2) impairment of pulmonary gas exchange, and (3) reduction of maximal cardiac output and peak leg . blood flow, each explaining about one third of the loss in Vo2max.65 However, mechanisms to explain impairment of gas exchange and lower blood flow remain elusive. Wagner459 proposes that the pressure gradient for diffusion of oxygen from capillaries to the working

0 0

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400

600

800

1000

1200

Oxygen uptake (mL O2/min)

Figure 1-8. Calculated changes in the PO2 of alveolar gas and arterial and mixed venous blood as oxygen uptake (mL O2/min) is increased for a climber on the summit of Mt. Everest. Unconsciousness develops at a mixed venous PO2 of 15 mm Hg. DMO2, muscle diffusing capacity for O2. (Modified from West JB: Respir Physiol 52:265–279, 1983, with permission.)

muscle cells may be inadequate. Another concept is that increased cerebral hypoxia from exercise-induced desaturation is the limiting factor.75,211 Mountaineers, for example, become lightheaded and their vision dims when they move too quickly at extreme altitude (Fig. 1-8).466

Training at High Altitude Optimal training for increased performance at high altitude depends on the altitude of residence and the athletic event. For aerobic activities (events lasting more than 3 or 4 minutes) at altitudes above 2000 m, acclimatization for 10 to 20 days is necessary to maximize performance.88 For events occurring above 4000 m, acclimatization at an intermediate altitude is recommended. Highly anaerobic events at intermediate altitudes require only arrival at the time of the event, although mountain sickness may become a problem. The benefits of training at high altitude for subsequent performance at or near sea level depend on choosing a training altitude that maximizes the benefits and minimizes the “detraining” inevitable when maximal oxygen uptake is limited (altitude greater than 1500 to 2000 m). Hence, data from training above 2400 m have shown no increase in subsequent sea level performance. Also, intermittent exposures to hypoxia seem to have no benefit.221,445 Runners returning to sea level after 10 days’ training at 2000 m had faster running times and an increase in aerobic power, plasma volume, and hemoglobin concentration.14 More recent work suggests training benefits from training at low altitude while sleeping at high altitude—the “live

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PART ONE: MOUNTAIN MEDICINE

high, train low” approach.258,429 Coaches and endurance athletes from around the world are convinced of the benefits of training and/or sleeping at moderate altitude to improve sea level performance. The benefit appears due to enhanced erythropoietin production and increased red cell mass, which requires adequate iron stores and thus usually iron supplementation.279,374,428 Some individuals do not respond to “live high, train low,” perhaps because of an inability to increase erythropoietin levels sufficient to raise red cell mass and thus increase oxygen carrying capacity.68,217


HIGH-ALTITUDE SYNDROMES High-altitude syndromes are illnesses attributed directly to hypobaric hypoxia, even if exact mechanisms are unclear. Clinically and pathophysiologically, these syndromes overlap. Rapidity of onset of hypoxia is crucial; for example, sudden exposure to extreme altitude may result in death from acute hypoxia (asphyxia), whereas more gradual ascent to the same altitude may result in AMS or no illness at all. Where symptoms of acute hypoxia end and AMS begins is vague, as reflected in the classic experiments of Bert.49 In terms of altitude illness, the general concept of a spectrum of illness with a common underlying pathogenesis is well accepted and provides a useful framework for discussion. For the neurologic syndromes, the spectrum progresses from high-altitude headache to AMS to high-altitude cerebral edema (HACE). In the lung, the spectrum includes pulmonary hypertension, interstitial edema, and HAPE. These problems all occur within the first few days of ascent to a higher altitude, have many common features, and respond to descent or oxygen. Longer-term problems of altitude exposure include high-altitude deterioration and chronic mountain sickness.

Neurologic Syndromes Neurologic syndromes at high altitude reflect both the nervous system’s sensitivity to hypoxia and the effects of compensatory mechanisms. Although brain ATP production and metabolism remain intact during hypoxia, neurotransmitter synthesis is sensitive to hypoxia, and impaired synthesis of neurotransmitters accounts for symptoms of acute cerebral hypoxia as well as cognitive defects at high altitude. The compensatory cerebral vasodilation at altitude appears to play a role in causing altitude headache, and it also contributes to development of AMS and HACE. However, much of the pathophysiology of AMS and HACE remains a mystery. Focal neurologic deficits without cerebral edema are also difficult to explain; cerebral artery spasm and watershed hypoxia have both been invoked. The understanding of the exact etiology of these neurologic syndromes due to hypoxia will parallel advances in neuroscience; the emphasis in altitude illness is finally and appropriately on the brain.368

Acute Cerebral Hypoxia Acute, profound hypoxia, although of greatest interest in aviation medicine, may also occur on terra firma when ascent is too rapid or when hypoxia abruptly worsens. Carbon monoxide poisoning, pulmonary edema, sudden overexertion, sleep apnea, or a failed oxygen delivery system may rapidly exaggerate hypoxemia. In an unacclimatized person, loss of consciousness from acute hypoxia occurs at an Sao2 of 40% to 60% or at an arterial Po2 of less than about 30 mm Hg. Tissandier, the sole

survivor of the flight of the balloon Zenith in 1875, gave a graphic description of the effects of acute hypoxia: But soon I was keeping absolutely motionless, without suspecting that perhaps I had already lost use of my movements. Towards 7,500 m, the numbness one experiences is extraordinary. The body and the mind weakens little by little, gradually, unconsciously, without one’s knowledge. One does not suffer at all; on the contrary. One experiences inner joy, as if it were an effect of the inundating flood of light. One becomes indifferent; one no longer thinks of the perilous situation or of the danger; one rises and is happy to rise. Vertigo of the lofty regions is not a vain word. But as far as I can judge by my personal impression, this vertigo appears at the last moment; it immediately precedes annihilation—sudden, unexpected, irresistible. I wanted to seize the oxygen tube, but could not raise my arm. My mind, however, was still very lucid. I was still looking at the barometer; my eyes were fixed on the needle which soon reached the pressure number of 280, beyond which it passed. I wanted to cry out “We are at 8,000 meters.” But my tongue was paralyzed. Suddenly I closed my eyes and fell inert, completely losing consciousness.49 The ascent to over 8000 m took 3 hours, and the descent less than 1 hour. When the balloon landed, Tissandier’s two companions were dead. The prodigious work that Paul Bert conducted in an altitude chamber during the 1870s showed that lack of oxygen, ratherthan an effect of isolated hypobaria, explained the symptoms experienced during rapid ascent to extreme altitude. There exists a parallelism to the smallest details between two animals, one of which is subjected in normal air to a progressive diminution of pressure to the point of death, while the other breathes, also to the point of death, under normal pressure, an air that grows weaker and weaker in oxygen. Both will die after having presented the same symptoms.49 Bert goes on to describe the symptoms of acute exposure to hypoxia: It is the nervous system which reacts first. The sensation of fatigue, the weakening of the sense perceptions, the cerebral symptoms, vertigo, sleepiness, hallucinations, buzzing in the ears, dizziness, pricklings . . . are the signs of insufficient oxygenation of central and peripheral nervous organs. . . . The symptoms . . . disappear very quickly when the balloon descends from the higher altitudes, very quickly also . . . the normal proportion of oxygen reappears in the blood. There is an unfailing connection here.49 Bert was also able to both prevent and immediately resolve symptoms by breathing oxygen. Modern studies of acute hypoxic exposure in simulated altitude chambers use the measurement of time of useful consciousness; that is, the time until a subject can no longer take corrective measures, such as putting on an oxygen mask. With exposure to 8500 m (28,000 feet), that time is 60 seconds during moderate activity and 90 seconds at rest. Acute hypoxia can be quickly reversed by immediate administration of oxygen, rapid pressurization or descent, or correc-

Chapter 1: High-Altitude Medicine tion of an underlying cause, such as relief of apnea, removal of a carbon monoxide source, repair of an oxygen delivery system, or cessation of overexertion. Hyperventilation increases time of useful consciousness during severe hypoxia.

High-Altitude Headache Headache is generally the first unpleasant symptom consequent to altitude exposure and is sometimes the only symptom.183 It may or may not be the harbinger of AMS, which is defined as the presence of headache plus at least one of four other symptoms, in the setting of an acute altitude gain.365 One could even argue that it is the headache itself that causes other symptoms such as anorexia, nausea, lassitude, and insomnia, as is commonly seen in migraine or tension headaches, and that mild AMS is essentially due to headache. The International Headache Society (IHS) has defined high-altitude headache as “a headache that develops within 24 hours after sudden ascent to altitudes above 3,000m” and that is “associated with at least one other symptom typical of high altitude, including (a) Cheyne-Stokes respiration at night, (b) a desire to overbreathe and (c) exertional dyspnea.” This definition is problematic in that many experience altitude headache between 2000 and 3000 m, and the other symptoms have no demonstrated association with headache. Recent studies have attempted to characterize the clinical features and incidence of headache at altitude. Silber and colleagues found that 50 of 60 trekkers (83%) in Nepal up to 5100 m developed at least one headache when over 3000 m.416 Older persons were less susceptible; women and those with headaches in daily life had more severe headaches but not more headaches than others. Of those with headache, 52% did not have AMS by the Lake Louise criteria; 44% did not have one of the symptoms in the IHS definition, indicating its ineffectiveness. Various medications alleviated the headache 70% of the time, especially when it was mild. The clinical features were widely variable. In general, the headaches were bilateral, generalized, dull, and exacerbated by exertion or movement, and they often occurred at night and resolved within 24 hours. Thus,

11

the headaches had some features of increased intracranial pressure. Persons with history of migraine did not have a higher incidence of headache. The term high altitude headache (HAH) has been used in the literature for decades, and studies directed toward the pathophysiology and treatment of HAH have been reported. Obviously, these are, to an extent, studies of AMS as well. Headache lends itself to investigation better than some other symptoms do, as headache scores have been well validated.214 In general, the literature suggests that HAH can be prevented by the use of nonsteroidal anti-inflammatory drugs57,61 and acetaminophen172 as well as the drugs commonly used for prophylaxis of AMS, acetazolamide and dexamethasone. Some agents appear more effective than others, with ibuprofen and aspirin apparently superior to naproxen.57,58,62 A serotonin agonist (sumatriptan, a 5-HT1 [serotonin type 1] receptor agonist) was reported to be effective for HAH prevention or treatment in some studies59,448 but not in others.23 Flunarizine, a specific calcium antagonist used for treatment of migraine, was not effective in one study.40 Interestingly, oxygen is often immediately effective for HAH (within 10 minutes) in subjects with and without AMS, indicating a rapidly reversible mechanism of the headache.21,158 The response to many different agents might reflect multiple components of the pathophysiology or merely the nonspecific nature of analgesics. As Sanchez del Rio and Moskowitz have pointed out, different inciting factors for headache may result in a final common pathway, such that the response to different therapies is not necessarily related to the initial cause of the headache.392 They recently provided a useful multifactorial concept of the pathogenesis of HAH, based on current understanding of headaches in general.392 They suggest that the trigeminovascular system is activated at altitude by both mechanical and chemical stimuli (vasodilation, nitric oxide, and other noxious agents), and in addition, the threshold for pain is quite likely altered at high altitude (Fig. 1-9).392 If AMS and especially HACE ensue, altered intracranial dynamics may also play a role, via compression or distention of pain-sensitive

Hypothalamus Brainstem

Autonomic response

CNS processing

High-altitude headache

Lower threshold for pain

Hypoxia

Trigeminovascular system activation

eNOS upregulation

↑ NO

Figure 1-9. Proposed pathophysiology of high-altitude headache. CNS, central nervous system; eNOS, endothelial nitric oxide synthase; NO, nitric oxide. (Modified from Sanchez del Rio M, Moskowitz MA: High altitude headache. In Roach RC,Wagner PD, Hackett PH [eds]: Hypoxia: Into the Next Millennium. New York, Plenum/Kluwer Academic, 1999, pp 145–153, with permission.)

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structures. The near future may bring a better understanding of the pathophysiology of these often debilitating headaches and new treatments as well.

Acute Mountain Sickness Epidemiology and Risk Factors Although the syndrome of AMS has been recognized for centuries, modern rapid transport and proliferation of participants in mountain sports have increased the number of victims and therefore public awareness (see Table 1-1). The incidence and severity of AMS depend on the rate of ascent and the altitude attained (especially the sleeping altitude), duration of altitude exposure, level of exertion, recent altitude exposure, and inherent physiologic (genetic) susceptibility.155,370,401 For example, AMS is more common on Mt. Rainier because of the rapid ascent, whereas high-altitude pulmonary or cerebral edema is uncommon because of the short stay (less than 36 hours). People with a demonstrated susceptibility to AMS had twice the incidence of AMS compared to nonsusceptible people, and this was independent of rate of ascent.401 The basis for inherent susceptibility is still unknown; clearly it depends on genetic factors. Recent altitude exposure can be protective; 5 days or more in the previous 2 months above 3000 m reduced susceptibility to AMS on ascent to 4559 m by one half, which was as effective as slow ascent401 (Fig. 1-10). Compared with persons living at a lower altitude, residence at 900 m or above reduced the incidence of AMS from 27% to 8% when ascending to between 2000 and 3000 m in Colorado.183 Age has an influence on incidence,155 with those older than 50 years somewhat less vulner-

able.369,416 In a large study in Colorado, those older than 60 years had an incidence of AMS that was half that seen in those younger than 60. In contrast, a study of 827 mountaineers in Europe showed no influence of age on susceptibility.401 Perhaps the different populations and physical activity explain the different results. No study has ever shown the older ages to be more susceptible. Children from 3 months to puberty studied in Colorado had the same incidence as young adults.440,489 A small study of tourists in Chile, however, found lower oxygen saturation and higher AMS in the 6- to 48-month age group at 4440 m. The largest study of children to date, of Han Chinese after ascent to Tibet, showed essentially the same incidence of AMS in 464 children as in 5335 adults, 34% and 38%, respectively.481 Women apparently have the same371,401 or a slightly greater incidence of AMS155,183,451 but may be less susceptible to pulmonary edema.83,424 There appears to be no relationship between AMS and the menstrual cycle.355 Most studies show no relationship between physical fitness and susceptibility to AMS. However, obesity seems to increase the odds of developing AMS.124,183 Smoking does not increase risk of AMS,183,225 and neither does use of oral contraceptives.225,330 In summary, the most important variables related to AMS susceptibility are genetic predisposition, altitude of residence, rate of ascent, and prior recent altitude exposure.

Diagnosis The diagnosis of AMS is based on the setting, symptoms, physical findings, and exclusion of other illnesses. The setting is generally rapid ascent of unacclimatized persons to 2500 m or

70%

60%

Nonsusceptible Susceptible

Prevalence of AMS

50%

40%

30%

20%

10%

0% Ascent 3 days and pre-exposure 5 days

Either ascent 3 days or pre-exposure 5 days

Ascent 4 days and pre-exposure 5 days

Rate of ascent and pre-exposure

Figure 1-10. The prevalence of acute mountain sickness (AMS) and 95% confidence intervals in nonsusceptible (blue bars) and susceptible (red bars) mountaineers in relationship to the state of acclimatization defined as slow ascent (more than 3 days), fast ascent (3 days or less), pre-exposed (5 days or more above 3000 m in the preceding 2 months), and not pre-exposed (4 days or less above 3000 m in the preceding 2 months). From Schneider M, Bernasch D,Weymann J, et al: Med Sci Sports Exerc 34:1886–1891, 2002, with permission.)

Chapter 1: High-Altitude Medicine higher from altitudes below 1500 m. For partially acclimatized persons, abrupt ascent to a higher altitude, overexertion, use of respiratory depressants, and perhaps onset of infectious illness321 are common contributing factors. The cardinal symptom of early AMS is headache, followed in incidence by fatigue, dizziness, and anorexia.155,183,421 The headache is usually throbbing, bitemporal, worse during the night and on awakening, and made worse by Valsalva’s maneuver or stooping over (see High-Altitude Headache). A good appetite is distinctly uncommon; nausea is common. These initial symptoms are strikingly similar to an alcohol hangover. Frequent awakening may fragment sleep, and periodic breathing often produces a feeling of suffocation. Although sleep disorder is nearly universal at high altitude, also affecting those without AMS, these symptoms may be exaggerated during AMS. Affected persons commonly complain of a deep inner chill, unlike mere exposure to cold temperature, accompanied by facial pallor. Other symptoms may include vomiting, dyspnea on exertion, and irritability. Lassitude can be disabling, with the victim too apathetic to contribute to his or her own basic needs. Pulmonary symptoms vary considerably. Everyone experiences dyspnea on exertion at high altitude; it may be difficult to distinguish normal from abnormal. Dyspnea at rest is distinctly abnormal, however, and presages HAPE rather than AMS. Cough is also extremely common at high altitude, and not particularly associated with AMS. Recent work suggests that altitude hypoxia actually lowers the cough threshold, as measured with an inhaled citric acid stimulus.283 However, any pulmonary symptom mandates careful examination for pulmonary edema. Specific physical findings are lacking in mild AMS. A higher heart rate has been noted in those with AMS,29,330 but Singh

13

and associates421 noted bradycardia (heart rate less than 66 beats/min) in two thirds of 1975 soldiers with AMS. Blood pressure is normal, but postural hypotension may be present. Occasionally, localized rales are present,273 but this has also been observed in those without AMS.153 A slightly increased body temperature with AMS may be present but is not diagnostic.271 Peripheral oxygen saturation as measured by pulse oximetry correlated poorly with presence of AMS during rapid ascent330,369,380 but was related to AMS during trekking.34 Sao2 at altitude on Denali was predictive of developing AMS on further ascent.366 Overall, pulse oximetry is of limited usefulness in diagnosis of AMS. Funduscopic examination reveals venous tortuosity and dilation. Retinal hemorrhages may or may not be present and are not diagnostic; they are more common in AMS than non-AMS individuals at 4243 m.153 Absence of the normal altitude diuresis, evidenced by lack of increased urine output and retention of fluid, is an early finding in AMS, although not always present.30,154,373,421,435 More obvious physical findings develop if AMS progresses to HACE. Typically, with onset of HACE, the victim wants to be left alone, lassitude progresses to inability to perform perfunctory activities such as eating and dressing, ataxia develops, and, finally, changes in consciousness appear, with confusion, disorientation, and impaired judgment. Coma may ensue within 24 hours of the onset of ataxia. Ataxia and confusion are the most useful signs for recognizing the progression from AMS to HACE; all persons proceeding to high altitudes should be aware of this fact. It is clinically useful to classify AMS as mild or as moderate to severe on the basis of symptoms (Table 1-4). Importantly, AMS can herald the beginning of life-threatening cerebral edema.

TABLE 1-4. Clinical Classifications of Acute Mountain Sickness (AMS) HIGH-ALTITUDE HEADACHE (HAH)

MILD AMS

Symptoms

Headache only

Headache, plus one more symptom (nausea/vomiting; fatigue/lassitude; dizziness or difficulty sleeping) All symptoms of mild intensity

LL-AMS score* Physical signs

1–3, headache only None

2–4 None

Findings

None

None

Pathophysiology

Unknown; cerebral vasodilatation, trigeminovascular system†?

Unknown; same as HAH?

MODERATE TO SEVERE AMS Headache, plus one or more symptoms (nausea/vomiting; fatigue/lassitude; dizziness or difficulty sleeping) Symptoms of moderate to severe intensity 5–15 None Antidiuresis Slightly increased body temperature Slight desaturation Widened A-a gradient Elevated ICP White matter edema (CT, MRI) Vasogenic edema

*The self-report Lake Louise AMS score. † See Figure 1-11. CT, computed tomography; HAPE, high-altitude pulmonary edema; ICP, intracranial pressure; MRI, magnetic resonance imaging.

HIGH-ALTITUDE CEREBRAL EDEMA (HACE) ±Headache Worsening of symptoms seen in moderate to severe AMS — Ataxia Altered mental status HAPE common: positive chest film, rales, dyspnea at rest Elevated ICP White matter edema (CT, MRI) Advanced vasogenic cerebral edema

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Box 1-3. Differential Diagnosis of High-Altitude Illnesses Acute mountain sickness and high-altitude cerebral edema

High-altitude pulmonary edema

Dehydration; exhaustion; viral or bacterial infection; alcohol hangover; hypothermia; carbon monoxide poisoning; migraine; hyponatremia; hypoglycemia; diabetic ketoacidosis; CNS infection; transient ischemic attack; arteriovenous malformation; stroke; seizures; brain tumors; ingestion of toxins, drugs, and alcohol; acute psychosis Asthma, bronchitis, pneumonia, mucus plugging (secondary to previous), hyperventilation syndrome, pulmonary embolus, heart failure, myocardial infarction

Differential Diagnosis Given the nonspecific nature of the symptoms, AMS is commonly confused with other conditions. Box 1-3 lists conditions that the authors have seen confused with AMS and HACE. AMS is most commonly misdiagnosed as a viral flulike illness, hangover, exhaustion, dehydration, or medication or drug effect. Unlike an infectious illness, uncomplicated AMS is not associated with fever and myalgia. Hangover is excluded by the history. Exhaustion may cause lassitude, weakness, irritability, and headache and may therefore be difficult to distinguish from AMS. Dehydration, which causes weakness, decreased urine output, headache, and nausea, is commonly confused with AMS. Response to fluids helps to differentiate the two. AMS is not improved by fluid administration alone, and body hydration does not influence susceptibility to AMS (contrary to conventional wisdom).9 Hypothermia may manifest as ataxia and mental changes. Sleeping medication can cause ataxia and mental changes, but soporifics may also precipitate high-altitude illness because of increased hypoxemia during sleep. Migraine may be very difficult to distinguish from AMS. A trial of oxygen breathing or descent can be helpful to discriminate these other conditions from AMS.

Carbon Monoxide Carbon monoxide poisoning is a danger at high altitude, where field shelters are designed to be small and windproof. Cooking inside closed tents and snow shelters during storms is a particular hazard.116,228,255,441,447 The effects of carbon monoxide and high-altitude hypoxia are additive. A reduction in oxyhemoglobin caused by carbon monoxide increases hypoxic stress, rendering a person at a physiologically higher altitude, which may precipitate AMS. Because of preexisting hypoxemia, smaller amounts of carboxyhemoglobin produce symptoms of carbon monoxide poisoning. These two problems may coexist. Immediate removal of the victim from the source of carbon monoxide and forced hyperventilation, preferably with supplemental oxygen, rapidly reverse carbon monoxide poisoning.

Pathophysiology The basic cause of AMS is hypoxemia (Fig. 1-11), but the syndrome is different from acute hypoxia. Because symptoms are somewhat worse with hypobaric hypoxia than with normobaric hypoxia, hypobaria apparently also plays a minor role, most likely through its effect on fluid retention.266,372 Because of a time lag in onset of symptoms after ascent and lack of immediate or complete reversal of all symptoms with oxygen, AMS is thought to be secondary to the body’s responses to modest hypoxia. In addition, even though an altitude of 2500 to 2700 m presents only a minor decrement in arterial oxygen transport (Sao2 is still above 90%), AMS is common and some individuals may become desperately ill. An acceptable explanation of pathophysiology must therefore address lag time, individual susceptibility to even modest hypoxia, and how acclimatization prevents the illness. Findings documented in mild to moderate AMS include relative hypoventilation,288,313 impaired gas exchange (interstitial edema),138,250 fluid retention and redistribution,30,373,435 and increased sympathetic drive.26,29 In mild to moderate AMS, limited data show that neither intracranial pressure (ICP) nor cerebrospinal fluid (CSF) pressure is elevated.13,173,480 In contrast, increased ICP and cerebral edema are documented in moderate to severe AMS, reflecting the continuum from advanced AMS to HACE.190,241,287,421,474 Relative hypoventilation may be due primarily to decreased drive to breathe (low hypoxic ventilatory response) or may be secondary to ventilatory depression associated with AMS.313,363 Persons with quite low hypoxic ventilatory response are more likely to suffer AMS than are those with a high ventilatory drive.180,288,313 For persons with intermediate hypoxic ventilatory response values (the majority of people), ventilatory drive has no predictive value.300,363 The protective role of a high hypoxic ventilatory response most likely results from overall increased oxygen transport, especially during sleep and exercise. Pulmonary dysfunction in AMS includes decreased vital capacity and peak expiratory flow rate,421 increased alveolar–arterial oxygen difference,138,181 decreased transthoracic impedance,213 and occasionally rales.273 These findings are compatible with interstitial edema—that is, increased extravascular lung water, most likely related to fluid retention and an increased interstitial water compartment. That exercise can contribute to interstitial edema at altitude was recently confirmed.7 Whether this can be considered a mild form of HAPE is unclear. The fact that nifedipine effectively prevents HAPE but does not prevent AMS or the increased alveolar–arterial oxygen gradient observed in AMS181 speaks against the increased lung water of AMS being related to HAPE. In addition, in contrast to the results in HAPE, alveolar lavage analysis in persons with AMS was normal. The mechanism of fluid retention may be multifactorial. Renal responses to hypoxia are variable and depend on plasma arginine vasopressin (AVP) concentration and sympathetic tone.176,435 Persons with AMS had elevated plasma or urine AVP levels in some studies,26,421 but cause and effect could not be established. Other studies showed no AVP elevation.30 The usual decrease in aldosterone on ascent to altitude does not occur in persons with AMS, and this may contribute to the antidiuresis.30 The renin-angiotensin system, although suppressed compared with its activity at sea level in both AMS and non-AMS groups, was more active in persons with AMS.29 Atrial natriuretic peptide (ANP) is elevated in AMS. Although this is most

Chapter 1: High-Altitude Medicine

15

Altitude hypoxia Leukocytes

↓ HVR, sleep, and exercise ↓ PaO2

↑ Sympathetic activity

Endothelial activation ↑ CBF ↑ CBV

↑ Cytokines, VEGF ↑ iNOS

Kidney

↑ Pcap ↑ Sodium and/or water retention

↑ BBB permeability Vasogenic edema

Peripheral edema Brain swelling

Adequate cerebrospinal compliance?

Yes

No AMS

No

AMS/HACE

Figure 1-11. Proposed pathophysiology of acute mountain sickness (AMS). BBB, blood–brain barrier; CBF, cerebral blood flow; CBV, cerebral blood volume; HACE, high-altitude cerebral edema; HVR, hypoxic ventilatory response; iNOS, inducible nitric oxide synthase; Pcap, capillary pressure;VEGF, vascular endothelial growth factor.

likely compensatory, elevated plasma ANP levels may contribute to vasodilation and increased microvascular permeability.29,472 One factor that can explain many of these changes is increased sympathetic activity, which reduces renal blood flow, glomerular filtration rate, and urine output, and suppresses renin.435 Increased sympathetic nervous system activity is also consistent with the greater rise in norepinephrine noted in subjects with AMS.26 See Krasney237 for a discussion of the critical role of central sympathetic activation on the kidney and its role in the pathophysiology of AMS. Whatever the exact mechanism, it seems that renal water handling switches from net loss or no change to net gain of water as persons become ill with AMS. The effectiveness of diuretics in treating AMS also supports a pivotal role for fluid retention and fluid shifts in the pathology of AMS.138,421 Persons with moderate to severe AMS or HACE display white matter edema on brain imaging and elevated intracranial pressure, whereas those with mild AMS do not.13,164,190,241,259,287,421 Possible mechanisms include cytotoxic edema with a shift of

fluid into the cells, or vasogenic edema from increased permeability of the blood–brain barrier (BBB), or both. The classic view that hypoxia causes failure of the ATP-dependent sodium pump and subsequent intracellular edema188 is untenable, given the newer understanding of brain energetics; ATP levels are maintained even in severe hypoxemia.415 The evidence now favors vasogenic brain edema as the cause of advanced AMS or HACE.164 The fact that dexamethasone is so effective for AMS also suggests vasogenic edema, as this is the only steroidresponsive brain edema. In addition, a model of AMS in conscious sheep exposed to 10% oxygen for several days supports the vasogenic brain-swelling hypothesis.239 The pathophysiology may be similar to that of hypertensive encephalopathy, another type of hyperperfusion encephalopathy407 in which loss of vascular autoregulation results in increased pressures transmitted to the capillaries with resultant white matter edema.251,252 Supporting this notion, Van Osta and colleagues showed that cerebral autoregulation was impaired the most in those with more severe AMS.450 Because prolonged cerebral vasodilation

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by itself, however, is not sufficient to induce vasogenic edema, Hackett148 and Krasney238 have proposed the additional factor of increased BBB permeability in the pathophysiology of AMS. Possible mechanisms of altered BBB permeability in AMS/HACE include vascular endothelial growth factor (VEGF), inflammatory cytokines, products of lipid peroxidation, reactive oxygen species, endothelium-derived products such as nitric oxide, and direct neural and humoral factors known to affect the BBB. The study by Schoch and colleagues provided impressive evidence for a role for VEGF.402 Mice on hypoxic exposure developed brain edema associated with elevated brain levels of VEGF; when given an antibody to VEGF, mice developed no cerebral edema.402 A recent study testing the hypothesis of a leaky BBB due to reactive oxygen species found evidence of free radical generation in subjects with AMS, but no evidence of altered BBB permeability despite the presence of mild brain swelling.13 Although the free radicals were not associated with BBB leak, their role in causing symptoms of AMS by another mechanism could not be excluded. The question of whether mild AMS, especially headache alone, is due to vasogenic cerebral edema is not yet answered (see High-Altitude Headache). Magnetic resonance imaging (MRI) studies demonstrated brain swelling in all subjects ascending rapidly to moderate altitude, regardless of the presence of AMS.114,210,322 The change in brain volume was greater than that expected from increased cerebral blood volume alone (due to vasodilation), but the individual components of blood and brain parenchyma could not be determined with MRI. Therefore, whether edema was present was not established. Regardless, the changes in the ill and the well groups were similar. Interestingly, Kilgore and colleagues did show a small but significant increase in T2 signal of the corpus callosum, hinting that vasogenic edema was starting, and the increase in the AMS group was twice that of the non-AMS group, though not quite statistically significant.231 Although it is still very much an open question, the literature to date does not confirm that mild AMS or headache alone is related to brain edema. To summarize, moderate to severe AMS and HACE represent a continuum from mild to severe vasogenic cerebral edema. Headache alone, or the earliest stages of AMS, might be related to edema or could be related to other factors, such as cerebral vasodilation or a migraine mechanism; further research is needed to clarify this issue.

Individual Susceptibility and Intracranial Dynamics. What might explain individual susceptibility to AMS? Correlation of AMS with HVR, ventilation, fluid status, lung function, and physical fitness has been weak at best. Ross hypothesized in 1985 that the apparently random nature of susceptibility might be explained by random anatomic differences.386 Specifically, he suggested that persons with smaller intracranial and intraspinal CSF capacity would be disposed to develop AMS, because they would not tolerate brain swelling as well as those with more “room” in the craniospinal axis. It is the displacement of CSF through the foramen magnum into the spinal canal that is the first compensatory response to increased brain volume, followed by increased CSF absorption and decreased CSF formation. Studies have shown that the increase in ICP for a given increase in brain volume is directly related to the tightness of the brain in the cranium (the brain volume–to–intracranial volume ratio) and to the volume of the spinal canal.413 Thus, the greater the initial CSF volume, the more accommodation

that can take place in response to brain edema. Increases in volume are buffered by CSF dynamics. In light of our present understanding of increased brain volume on ascent to altitude, Ross’s hypothesis is very attractive. Preliminary data that showed a relationship of pre-ascent ventricular size or brain volume–to–cranial vault ratios and susceptibility to AMS support this hypothesis, and the idea deserves further study.148,490 Figure 1-11 incorporates this concept into the pathophysiology.

Natural Course of Acute Mountain Sickness The natural history of AMS varies with initial altitude, rate of ascent, and clinical severity. Symptoms can start within as little as 2 hours after arrival, and rarely if ever start after 36 hours at a given altitude. AMS usually resolves over the next 24 to 48 hours. The more rapid the ascent, and the higher the altitude, the more likely it is that the symptoms will appear sooner and be worse. Singh and associates421 followed the illness in soldiers airlifted to altitudes of 3300 to 5500 m. Incapacitating illness lasted 2 to 5 days, but 40% still had symptoms after 1 week and 13% after 1 month. Nine soldiers failed to acclimatize in 6 months and were considered unfit for duty at high altitude.421 Chinese investigators report that a percentage of lowland Han Chinese stationed on the Tibet Plateau cannot tolerate the altitude because of persistent symptoms and must be relocated to the plains.483 Persistent anorexia, nausea, and headache may afflict climbers at extreme altitude for weeks and can be considered a form of persistent AMS. The natural history of AMS in tourists who sleep at more moderate altitudes is much more benign. Duration of symptoms at 2700 m was 15 hours, with a range of 6 to 94 hours.309 Most individuals treat or tolerate their symptoms, as the illness resolves over 1 to 3 days while acclimatization improves, but some people with AMS seek medical treatment or are forced to descend if symptoms persist. A small percentage of those with AMS (8% at 4243 m)155 go on to develop cerebral edema, especially if ascent continues in spite of illness.

Treatment The proper management of AMS is based on the severity of illness at presentation, and often depends on logistics, terrain, and experience of the caregiver. Early diagnosis is the key, as treatment in the early stages of illness is easier and more successful (Box 1-4). Proceeding to a higher sleeping altitude in the presence of symptoms is contraindicated. The victim must be carefully monitored for progression of illness. If symptoms worsen despite an extra 24 hours of acclimatization or treatment, descent is indicated. The two indications for immediate descent are neurologic findings (ataxia or change in consciousness) and pulmonary edema. Mild AMS can be treated by halting the ascent and waiting for acclimatization to improve, which can take from 12 hours to 3 or 4 days. Acetazolamide (250 mg twice a day orally, or as a single dose) speeds acclimatization and thus terminates the illness if given early.138,276 Symptomatic therapy includes analgesics such as aspirin (500 mg or 650 mg), acetaminophen (650 to 1000 mg), ibuprofen57 or other nonsteroidal antiinflammatory drugs, or codeine (30 mg) for headache. Promethazine (Phenergan, 25 to 50 mg by suppository or ingestion) is useful for nausea and vomiting. Persons with AMS should avoid alcohol and other respiratory depressants because of the danger of exaggerated hypoxemia during sleep.

Chapter 1: High-Altitude Medicine

17

BOX 1-4. Field Treatment of High-Altitude Illness HIGH-ALTITUDE HEADACHE AND MILD ACUTE MOUNTAIN SICKNESS

Stop ascent, rest, and acclimatize at same altitude Acetazolamide, 125 to 250 mg bid, to speed acclimatization Symptomatic treatment as necessary with analgesics and antiemetics OR descend 500 m or more MODERATE TO SEVERE ACUTE MOUNTAIN SICKNESS

Low-flow oxygen, if available Acetazolamide, 125 to 250 mg bid, with or without dexamethasone, 4 mg PO, IM, or IV q6h Hyperbaric therapy OR immediate descent HIGH-ALTITUDE CEREBRAL EDEMA

Immediate descent or evacuation Oxygen, 2 to 4 L/min Dexamethasone, 4 mg PO, IM, or IV q6h Hyperbaric therapy HIGH-ALTITUDE PULMONARY EDEMA

Minimize exertion and keep warm Oxygen, 4 to 6 L/min until improving, then 2 to 4 L/min If oxygen is not available: Nifedipine, 10 mg PO q4h by titration to response, or 10 mg PO once, followed by 30 mg extended release q12 to 24h Inhaled beta-agonist Consider sildenafil 50 mg every 8 hrs Hyperbaric therapy OR immediate descent PERIODIC BREATHING

Acetazolamide, 62.5 to 125 mg at bedtime as needed

Descent to an altitude lower than where symptoms began effectively reverses AMS. Although the person should descend as far as necessary for improvement, descending 500 to 1000 m is usually sufficient. Exertion should be minimized. Oxygen, if available, is particularly effective (and supply is conserved) if given in low flow (0.5 to 1 L/min by mask or cannula) during the night. Hyperbaric chambers, which simulate descent, have been used to treat AMS and aid acclimatization. They are effective and require no supplemental oxygen. Lightweight (less than 7 kg) fabric pressure bags inflated by manual air pumps are now being used on mountaineering expeditions and in mountain clinics (Fig. 1-12). An inflation of 2 pounds per square inch (PSI) is roughly equivalent to a drop in altitude of 1600 m; the exact equivalent depends on the initial altitude.223,361 A few hours of pressurization results in symptomatic improvement and can be an effective temporizing measure while awaiting descent or the benefit of medical therapy.223,320,336,375,439 Long-term (12 hours or more) use of these portable devices is necessary to resolve AMS completely. Acetazolamide is of unquestionable prophylactic value and is now commonly and successfully used to treat AMS as well,

Figure 1-12. Gamow bag used to treat a patient with high altitude pulmonary edema at Everest Base Camp Medical Clinic (5350 m). (Photo courtesy Luanne Freer, MD.)

although data supporting this are minimal.138,276 Singh and colleagues successfully used furosemide (80 mg twice a day for 2 days) to treat 446 soldiers with all degrees of AMS; it has not since been studied for treatment.421 Furosemide induced brisk diuresis, relieved pulmonary congestion, and improved headache and other neurologic symptoms. Spironolactone, hydrochlorothiazide, and other diuretics have not yet been evaluated for treatment. The steroid betamethasone was initially reported by Singh and colleagues421 to improve symptoms of soldiers with severe AMS. Subsequently, studies have found dexamethasone to be effective for treatment of all degrees of AMS.113,163,227 Hackett and colleagues163 used 4 mg orally or intramuscularly every 6 hours, and Ferrazinni and associates113 gave 8 mg initially, followed by 4 mg every 6 hours. Both studies reported marked improvement within 12 hours, with no significant side effects. Symptoms increased when dexamethasone was discontinued after 24 hours.163 Clinicians debate whether the use of dexamethasone should also require descent. Is it safe to continue on after treatment with dexamethasone, or while taking the medication? In reality, people do, and problems seem to be few. In the authors’ opinion, dexamethasone use should be limited to less than 48 hours, to minimize side effects. This is generally sufficient time to descend, or to better acclimatize, with or without acetazolamide. The mechanism of action of dexamethasone is unknown; it does not affect oxygen saturation, fluid balance, or periodic breathing.259 The drug blocks the action of VEGF,402 diminishes the interaction of endothelium and leukocytes (thus reducing inflammation),134 and may also reduce cerebral blood flow.220 Dexamethasone seems to not improve acclimatization, as symptoms recur when the drug is withdrawn. Therefore, an argument could be made for using dexamethasone to relieve symptoms and acetazolamide to speed acclimatization.48

Prevention Graded ascent is the surest and safest method of prevention, although particularly susceptible individuals may still become ill. Current recommendations for people without altitude

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experience are to avoid abrupt ascent to sleeping altitudes greater than 3000 m and to spend 2 to 3 nights at 2500 to 3000 m before going higher, with an extra night for acclimatization every 600 to 900 m if continuing ascent. Abrupt increases of more than 600 m in sleeping altitude should be avoided when over 2500 m. However, a recent study on Aconcagua reinforced the notion that individual susceptibility is a key factor; those who are resistant to AMS can safely proceed much more quickly on the mountain.341 Day trips to higher altitude, with a return to lower altitude for sleep, aid acclimatization. Alcohol and sedative-hypnotics are best avoided on the first 2 nights at high altitude. Whether a diet high in carbohydrates reduces AMS symptoms is controversial.80,171,437 Exertion early in altitude exposure contributes to altitude illness,370 whereas limited exercise seems to aid acclimatization. Because altitude exposure in the previous weeks is protective, a faster rate of ascent may then be possible.

Acetazolamide Prophylaxis. Acetazolamide is the drug of choice for prophylaxis of AMS. A carbonic anhydrase (CA) inhibitor, acetazolamide slows the hydration of carbon dioxide: CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3− CA CA The effects are protean, involving particularly the red blood cells, brain, lungs, and kidneys. By inhibiting renal CA, acetazolamide reduces reabsorption of bicarbonate and sodium and thus causes bicarbonate diuresis and metabolic acidosis starting within 1 hour after ingestion. This rapidly enhances ventilatory acclimatization, increasing oxygenation. Importantly, the drug maintains oxygenation during sleep and prevents periods of extreme hypoxemia (see Figure 1-5).159,433,436 Because of acetazolamide’s diuretic action, it counteracts the fluid retention of AMS. It also diminishes nocturnal antidiuretic hormone (ADH) secretion72 and decreases CSF production and volume and possibly CSF pressure.410 Which of these effects is most important in preventing AMS is unclear. Numerous studies taken together indicate that acetazolamide is approximately 75% effective in preventing AMS in persons rapidly transported to altitudes of 3000 to 4500 m.110 Indications for acetazolamide prophylaxis include rapid ascent (in 1 day or less) to altitudes over 3000 m; a rapid gain in sleeping altitude, for example, moving camp from 4000 to 5000 m in a day; and a past history of AMS or HAPE. The ideal dosage of acetazolamide for prevention is debated. Many studies have shown that 250 mg twice a day or three times a day was effective, as well as 500 mg in sustained action capsule taken every 24 hours.70,126,137,152,250,353,476 To reduce the side effects, especially paresthesias, clinicians have more recently been using smaller dosages (125 mg twice a day)298; two studies so far support this,32,254 whereas one does not.66 Renal carbonic anhydrase is blocked at a dosage of 5 mg/kg/day. As this seems to be the important effect for preventing AMS, this is probably the ideal dosage, both in children and adults. Thus, adjusting the dosage for body weight might provide the best effect with the fewest side effects. Duration of medication use varies; the standard advice is to start 24 hours before ascent. Most authors recommend continuing for at least the first 2 days at high altitude, and longer if there is a continuing gain in altitude. Acetazolamide can also be taken episodically, to speed

acclimatization at any point while gaining altitude, or to treat mild AMS. There is no rebound when discontinued. Although the danger of altitude illness passes after a few days of acclimatization, acetazolamide may still be useful for sleep. Acetazolamide has side effects, most notably peripheral paresthesias and polyuria, and less commonly nausea, drowsiness, impotence, and myopia. Because it inhibits the instant hydration of carbon dioxide on the tongue, acetazolamide allows carbon dioxide to be tasted and can ruin the flavor of carbonated beverages, including beer. As a nonantibiotic sulfonamide drug, acetazolamide is usually tolerated well by people with a history of sulfa antibiotic allergy; approximately 10% may have an allergic reaction.430 In those without a history of allergy to sulfa antibiotic, the incidence of hypersensitivity reaction to a sulfonamide nonantibiotic was 1.6%.430 The same analysis concluded that people who are penicillin allergic are in fact more likely to react to drugs such as acetazolamide than are people who are sulfa allergic. Nonetheless, it is wise to be cautious for those with a history of allergy, especially anaphylaxis to either sulfa or penicillin. Many experts recommend a trial dose of the medication well before the altitude sojourn, to determine if the drug is tolerated well. Although the usual allergic reaction is a rash starting a few days after ingestion, anaphylaxis to acetazolamide does rarely happen.

Dexamethasone Prophylaxis. Dexamethasone effectively prevents AMS. A dosage of 2 mg every 6 hours or 4 mg every 12 hours was sufficient for sedentary subjects,220 but for exercising subjects at or above 4000 m, this was insufficient,47,163,377 and 4 mg every 6 hours was necessary to prevent AMS.378 The initial chamber study in 1984 was with sedentary subjects.220 The drug reduced the incidence of AMS from 78% to 20%, comparable to previous studies with acetazolamide. Dexamethasone was not as effective in exercising subjects on Pike’s Peak,377 but subsequent work has shown effectiveness comparable to that of acetazolamide.37,110,259,308,491 The combination of acetazolamide and dexamethasone proved superior to dexamethasone alone.491 Because of potential serious side effects and the rebound phenomenon, dexamethasone is best reserved for treatment rather than for prevention of AMS, or used for prophylaxis when necessary in persons intolerant of or allergic to acetazolamide. Other Agents for AMS Prevention. Studies with Ginkgo biloba have had inconsistent results. Four studies had positive results, ranging from 100% to 50% reduction in AMS when given either 5 days or 1 day before ascent.127,269,315,381 Three studies were negative, two of which were follow-up studies by investigators with positive results previously.70,126,254 Conflicting results can possibly be explained by differences in dosing, duration of pretreatment, and varying rates of ascent, but most likely they result from differences in preparations of ginkgo. Ginkgo biloba is a complicated plant extract whose active ingredient in terms of preventing AMS is unknown. Even in the “standardized” preparations (24% flavonoids and 6% terpene ginkolides), the amounts of specific chemicals can vary considerably. Until the active ingredient is discovered and standardized, results with ginkgo will continue to be mixed. Meanwhile, as the product is very safe and inexpensive, does not require a prescription, and can be helpful, it is reasonable to

Chapter 1: High-Altitude Medicine consider its use. Acetazolamide, however, is probably the superior agent. Spironolactone,215,249 naproxen, calcium channel blockers, antacids, and medroxyprogesterone acetate have shown ineffectiveness for AMS prevention. Bailey and Davies tested an antioxidant cocktail for prevention of AMS.12 They reasoned that free-radical–mediated damage to the BBB might play a role in the pathophysiology. They preloaded nine subjects with daily l-ascorbic acid, dl-α-tocopherol acetate, and α-lipoic acid, and nine subjects with placebo for 3 weeks, and then maintained dosing during a 10-day trek to Everest base camp. Those on antioxidants had a slightly lower AMS score, higher arterial oxygen saturation, and better appetite.12 Although these results were of marginal clinical value, the use of antioxidants certainly deserves further study. See Bärtsch and colleagues for a detailed discussion of the antioxidant hypothesis.20

High-Altitude Cerebral Edema High-altitude cerebral edema is an uncommon but deadly condition, usually occurring in those with AMS or HAPE. Although HACE is most common over 3000 m, it has been reported as low as 2100 m.96 Reliable estimates of incidence range from 0.5% to 1% in unselected high-altitude visitors,28,152 but it was 3.4% in those who had developed AMS.152 HACE occurs in 13% to 20% of persons with HAPE,123,179,203 and in up to 50% of those who die from HAPE. In addition, HAPE is very common in those diagnosed with HACE; one series from Colorado reported that 11 of 13 with a primary diagnosis of HACE also had HAPE. Pure cerebral edema, without pulmonary edema, appears to be uncommon. The mean altitude of onset was 4730 m in one survey but was lower (3920 m) when there was an association with HAPE.204 Data are insufficient to draw any conclusions regarding effects of sex, age, preexisting illness, or genetics on susceptibility to HACE. Clinically and pathophysiologically, advanced AMS and HACE are similar, so a distinction between them is inherently blurred. See a recent review for a more complete discussion.156 HACE is an encephalopathy, whereas AMS is not. The hallmarks of HACE are ataxic gait, severe lassitude, and altered consciousness, including confusion, impaired mentation, drowsiness, stupor, and coma. Headache, nausea, and vomiting are frequent but not always present. Hallucinations, cranial nerve palsy, hemiparesis, hemiplegia, seizures, and focal neurologic signs have also been reported.99,167,190,421 Seizures are distinctly uncommon. Retinal hemorrhages are common but not diagnostic. The progression from mild AMS to unconsciousness may be as fast as 12 hours but usually requires 1 to 3 days; HACE can develop more quickly in those with HAPE. An arterial blood gas study or pulse oximetry often reveals exaggerated hypoxemia. Clinical examination and chest radiography may reveal pulmonary edema. Laboratory studies and lumbar puncture are useful only to rule out other conditions. Computerized tomography (CT) may show compression of sulci and flattening of gyri, and attenuation of signal more in the white matter than gray matter. MRI is more revealing, with a characteristic high T2 signal in the white matter, especially the splenium of the corpus callosum, and most evident on diffusion-weighted images.164,479 The following case report from Mt. McKinley illustrates a typical clinical course of HACE in conjunction with HAPE.

19

Clinical Presentation H.E. was a 26-year-old German lumberjack with extensive mountaineering experience. He ascended to 5200 m from 2000 m in 4 days and attempted the summit (6194 m) on the fifth day. At 5800 m he turned back because of severe fatigue, headache, and malaise. He returned alone to 5200 m, stumbling on the way because of loss of coordination. He had no appetite and crawled into his sleeping bag too weak, tired, and disoriented to undress. He recalled no pulmonary symptoms. In the morning H.E. was unarousable, slightly cyanotic, and noted to have CheyneStokes respirations. After 10 minutes on high-flow oxygen, H.E. began to regain consciousness, although he was completely disoriented and unable to move. A rescue team lowered him down a steep slope, and on arrival at 4400 m 4 hours later he was conscious but still disoriented, able to move extremities but unable to stand. Respiratory rate was 60 breaths/min and heart rate was 112 beats/min. Papilledema and a few rales were present. Sao2% was 54% on room air (normal is 85% to 90%). On a nonrebreathing oxygen mask with 14 L/min oxygen, the Sao2% increased to 88% and the respiratory rate decreased to 40 breaths/min. Eight milligrams of dexamethasone were administered intramuscularly at 4:20 pm and continued orally, 4 mg every 6 hours. At 5:20 pm, H.E. began to respond to commands. The next morning he was still ataxic but was able to stand, take fluids, and eat heartily. He was evacuated by air to Anchorage (sea level) at 12:00 pm. On admission to the hospital at 3:30 pm, roughly 36 hours after regaining consciousness, H.E. was somewhat confused and mildly ataxic. Arterial blood gas studies on room air showed a Po2 of 58 mm Hg, pH of 7.5, and Pco2 of 27 mm Hg. Bilateral pulmonary infiltrates were present on the chest radiograph. Magnetic resonance imaging of the brain revealed white matter edema, primarily of the corpus callosum (Fig. 1-13). On discharge the next morning H.E. was oriented, bright, and cheerful and had very minor ataxia and clear lung fields.

Pathophysiology The pathophysiology of HACE is a progression of the same mechanism seen in advanced AMS (see Acute Mountain Sickness, Pathophysiology; also see Figure 1-11), and appears to be vasogenic edema. In cases similar to this, lumbar punctures have revealed elevated CSF pressures, often more than 300 mm H2O,190,474 evidence of cerebral edema on CT scans and MR images,164,236 and gross cerebral edema on necropsy.98,99 Small petechial hemorrhages were also consistently found on autopsy, and venous sinus thromboses were occasionally seen.98,99 Welldocumented cases have often included pulmonary edema that was not clinically apparent. Whereas the brain edema of reversible HACE is most likely vasogenic, as the spectrum shifts to severe, end-stage HACE, then gray matter (presumably cytotoxic) edema develops as well, culminating in brain herniation and death. As Klatzo235 has pointed out, as vasogenic edema progresses, the distance between brain cells and their capillaries increases, so that nutrients and oxygen eventually fail to diffuse and the cells are rendered ischemic, leading to intracellular (cytotoxic) edema. Raised intracranial pressure produces many of its effects by decreasing cerebral blood flow, and brain tissue becomes

20

PART ONE: MOUNTAIN MEDICINE response to steroids and oxygen seems excellent if they are given early in the course of the illness and disappointing if they are not started until the victim is unconscious. Coma may persist for days, even after evacuation to low altitude, but other causes of coma must be considered and ruled out by appropriate evaluation.190 The average duration of hospital stay in one series of patients with severe HACE was 5.6 days, and average time to full recovery was 2.4 weeks, with a range of 1 day to 6 weeks.164 Two patients of the 44 in the series by Dickinson remained in coma for 3 weeks.99 Sequelae lasting weeks are common164,190; longer-term follow-up has been limited, but presumed permanent impairment has been reported.156,190 Prevention of HACE is the same as for AMS and HAPE.

Focal Neurologic Conditions without AMS or Cerebral Edema

Figure 1-13. Magnetic resonance image of a patient with high-altitude cerebral edema. Increased T2 signal in splenium of corpus callosum (arrow) indicates edema.

ischemic on this basis also.294 Focal neurologic signs caused by brainstem distortion and by extra-axial compression, as in third and sixth cranial nerve palsies, may develop,382 making cerebral edema difficult to differentiate from primary cerebrovascular events. The most common clinical presentation, however, is change in consciousness associated with ataxia, without focal signs.487

Treatment Given the sporadic nature and generally remote location of this disorder, it is not surprising there are no controlled trials regarding treatment of HACE. All experts agree that successful treatment requires early recognition. At the first sign of ataxia or change in consciousness, descent should be started, dexamethasone (4 to 8 mg intravenously, intramuscularly, or orally initially, followed by 4 mg every 6 hours) administered, and oxygen (2 to 4 L/min by vented mask or nasal cannula) applied if available (see Box 1-4). Oxygen can be titrated to maintain Sao2 at greater than 90% if oximetry is available. Comatose patients require additional airway management and bladder drainage. Attempting to decrease intracranial pressure by intubation and hyperventilation is a reasonable approach, although these patients are already alkalotic, and over-hyperventilation could result in disastrous cerebral ischemia. Loop diuretics such as furosemide (40 to 80 mg) or bumetanide (1 to 2 mg) may reduce brain hydration, and have been used successfully,97,421 but an adequate intravascular volume to maintain perfusion pressure is critical. Hypertonic solutions of saline, mannitol, or oral glycerol have been suggested but are rarely used in the field. Controlled studies are lacking, but empirically the

Various localizing neurologic signs, transient in nature and not necessarily occurring in the setting of AMS, suggest migraine, cerebrovascular spasm, transient ischemic attack, local hypoxia without loss of perfusion (watershed effect), or focal edema. Cortical blindness is one such condition. Hackett and colleagues161 reported six cases of transient blindness in climbers or trekkers with intact pupillary reflexes, which indicated that the condition was due to a cortical process. Treatment with breathing of either carbon dioxide (a potent cerebral vasodilator) or oxygen resulted in prompt relief, suggesting that the blindness was due to inadequate regional circulation or oxygenation. Descent effected relief more slowly. Other conditions that could be attributed to spasm or transient ischemic attack (TIA) have included transient hemiplegia or hemiparesis, transient global amnesia, unilateral paresthesias, aphasia, and scotoma.31,36,52,67,262,477,493 The true mechanism of these focal findings is unknown, and it may be multifactorial. Young, healthy altitude sojourners are unlikely to have TIA syndrome from cerebrovascular disease. The occurrence of stroke in a young, fit person at high altitude is uncommon but tragic. A number of case reports have described climbers with resultant permanent dysfunction.71,189,423 Indian soldiers at extreme altitude have a high incidence of stroke.219 Cerebral venous thrombosis presents more insidiously, and diagnosis is often delayed.143,222,389,423,443,493 Factors contributing to stroke may include polycythemia, dehydration, patent foramen ovale, and increased intracranial pressure if AMS is present, increased cerebrovenous pressure, cerebrovascular spasm, and, in certain episodes, coagulation abnormalities.33 Stroke may be confused with HACE. Neurologic symptoms, especially focal abnormalities without AMS or HAPE that persist despite treatment with oxygen, steroids, and descent, suggest a cerebrovascular event and mandate careful evaluation with a complete neurologic workup.

Clinical Presentation E.H., a 42-year-old male climber on a Mt. Everest expedition, awoke at 8000 m with dense paralysis of the right arm and weakness of the right leg. On descent the paresis cleared, but at base camp (5000 m) severe vertigo developed, along with extreme ataxia and weakness. Neurologic consultation on return to the United States resulted in a diagnosis of multiple small cerebral infarcts, but none was visible on CT scan of the brain. The hematocrit value 3

Chapter 1: High-Altitude Medicine weeks after descent from the mountain was 70%. Over the next 4 years, signs gradually improved, but mild ataxia, nystagmus, and dyslexia persist. The focal and persistent nature of the cerebral symptoms and signs, although multiple, indicates an etiology related to cerebrovascular effects rather than intracranial pressure. The hematocrit value on the mountain was greater than 70%, high enough for increased viscosity and microcirculatory sludging to contribute to ischemia and infarction. No familial thrombophilia was detected. Treatment of stroke is supportive. Oxygen and steroids may be worthwhile to treat any AMS or HACE component. Immediate evacuation to a hospital is indicated. Persons with transient ischemic attacks at high altitude should probably be started on aspirin therapy and proceed to a lower altitude. Oxygen may quickly abort cerebrovascular spasms and will improve watershed hypoxic events. When oxygen is not available, rebreathing to raise alveolar Pco2 may be helpful through increasing cerebral blood flow.

Cognitive Changes at High Altitude If cerebral oxygen consumption is constant, what causes the well-documented, albeit mild, cognitive changes at high altitude? The cognitive changes may be related to specific neurotransmitters that are affected by mild hypoxia. For example, tryptophan hydroxylase in the serotonin synthesis pathway has a high requirement for oxygen (Km = 37 mm Hg).79,129 Tyrosine hydroxylase, in the dopamine pathway, is also oxygen sensitive. Gibson and Blass suggested that a decrease in acetylcholine activity during hypoxia might explain the lassitude.129 In a fascinating study, Banderet and Lieberman showed that increased dietary tyrosine reduced mood changes and symptoms of environmental stress in subjects at simulated altitude.16 Further work with neurotransmitter agonists and antagonists will help shed light on their role in cognitive dysfunction at altitude and could lead to new pharmacologic approaches to improve neurologic function.

High-Altitude Pulmonary Edema The most common cause of death related to high altitude, HAPE is completely and easily reversed if recognized early and treated properly. Undoubtedly, HAPE was misdiagnosed for centuries, as evidenced by frequent reports of young, vigorous men suddenly dying of “pneumonia” within days of arriving at high altitude. The death of Dr. Jacottet, “a robust, broadshouldered young man,” on Mt. Blanc in 1891 (he refused descent so that he could “observe the acclimatization process” in himself) may have provided the first autopsy of HAPE. Angelo Mosso wrote, From Dr. Wizard’s post-mortem examination . . . the more immediate cause of death was therefore probably a suffocative catarrh accompanied by acute edema of the lungs. . . . I have gone into the particulars of this sorrowful incident because a case of inflammation of the lungs also occurred during our expedition, on the summit of Monte Rosa, from which, however, the sufferer fortunately recovered.319 On an expedition to K2 (Karakoram Range, Pakistan) in 1902, Alistair Crowley85 described a climber “suffering from edema of both lungs and his mind was gone.” In the Andes, physicians were familiar with pulmonary edema peculiar to high

21

altitude,209,264 but it was not until Houston187 and Hultgren and Spickard197 that the English-speaking world became aware of high altitude pulmonary edema (see Rennie354 for a review). Hultgren and colleagues208 then published hemodynamic measurements in persons with HAPE, demonstrating that it was a noncardiogenic edema. Since that time, many studies and reviews have been published, and HAPE is still the subject of intense investigation. The reader is referred to recent reviews.19,27,145,403,468 Individual susceptibility, rate of ascent, altitude reached, degree of cold,351 physical exertion and certain underlying medical conditions are all factors determining the prevalence of HAPE. The incidence varies from less than 1 in 10,000 skiers at moderate altitude in Colorado to 1 in 50 climbers on Mt. McKinley (6194 m) and up to 6% of mountaineers in the Alps ascending rapidly to 4559 m.24 Hultgren and colleagues reported 150 cases of HAPE over 39 months at a Colorado ski resort at 2928 m.206 Some regiments in the Indian Army had a much higher incidence of HAPE (15%) because of very rapid deployment to the extreme altitude of 5500 m422 (see Table 1-1). Persons who had a previous episode of HAPE had a 60% attack rate when they went to 4559 m in 36 hours; however, with a slower ascent, some of the same individuals were able to climb over 7000 m without developing HAPE.19,25 Although HAPE occurs in both sexes, it is perhaps less common in women.83,203,424 Whether all persons are capable of developing HAPE (with a very rapid ascent to a sufficiently high altitude and with heavy exercise) is arguable.27 With a sudden push to a higher altitude, even well-acclimatized individuals can succumb to HAPE, and some studies suggest that HAPE is a spectrum, with many persons contracting subclinical extravascular lung water.84 Nonetheless, a population of HAPEsusceptible persons with unique physiologic characteristics has been described (see HAPE Susceptibility). These individuals represent the small percentage of people who develop HAPE when others in the same circumstances do not.

Clinical Presentation D.L., a 34-year-old man, was in excellent physical condition and had been on numerous high-altitude backpacking trips, occasionally suffering mild symptoms of AMS. He drove from sea level to the trailhead and hiked to a 3050 m sleeping altitude the first night of his trip in the Sierra Nevada. He proceeded to 3700 m the next day, noticing more dyspnea on exertion when walking uphill, a longer time than usual to recover when he rested, and a dry cough. He complained of headache, shivering, dyspnea, and insomnia the second night. The third day the group descended to 3500 m and rested, primarily for D.L.’s benefit. That night D.L. was unable to eat, noted severe dyspnea, and suffered coughing spasms and headache. On the fourth morning, D.L. was too exhausted and weak to get out of his sleeping bag. His companions noted that he was breathless, cyanotic, and ataxic but had clear mental status. A few hours later he was transported by helicopter to a hospital at 1200 m. On admission he was cyanotic, oral temperature was 37.8° C (100° F), blood pressure 130/76 mm Hg, heart rate 96 beats/min, and respiratory frequency 20 breaths/min. Bilateral basilar rales were noted up to the scapulae. Findings of the cardiac examination

22

PART ONE: MOUNTAIN MEDICINE

TABLE 1-5. Severity Classification of High-Altitude Pulmonary Edema GRADE 1 Mild 2 Moderate 3 Severe

SYMPTOMS

SIGNS

CHEST FILM

Dyspnea on exertion, dry cough, fatigue while moving uphill (if any) Dyspnea, weakness, fatigue on level walking; raspy cough; headache; anorexia Dyspnea at rest, productive cough, orthopnea, extreme weakness

HR (rest) < 90–100; RR (rest) < 20; dusky nail beds; localized rales HR 90–100; RR 16–30; cyanotic nail beds; rales present; ataxia may be present Bilateral rales; HR > 110; RR > 30; facial and nail-bed cyanosis; ataxia; stupor; coma; blood-tinged sputum

Minor exudate involving less than 25% of one lung field Some infiltrates involving 50% of one lung or smaller area of both lungs Bilateral infiltrates > 50% of each lung

HR, heart rate; RR, respiratory rate. Modified from Hultgren HN: In Staub NC (ed): New York, Dekker, 1978, pp 437–469.

were reported as normal. Romberg and finger-to-nose tests revealed 1+ ataxia. Arterial blood gas studies on room air revealed Po2 24 mm Hg, Pco2 28 mm Hg, and pH 7.45. The chest radiograph showed extensive bilateral patchy infiltrates (Fig. 1-14C). D.L. was treated with bed rest and supplemental oxygen. On discharge to his sea level home 3 days later, his pulmonary infiltrates and rales had cleared, although his blood gas values were still abnormal: Po2 76 mm Hg, Pco2 30 mm Hg, and pH 7.45. He had an uneventful, complete recovery at home. D.L. was advised to ascend more slowly in the future, staging his ascent with nights spent at 1500 m and at 2500 m. He was taught the early signs and symptoms of HAPE and was advised about pharmacologic prophylaxis. This case illustrates a number of typical aspects of HAPE. Victims are frequently young, fit men who ascend rapidly from sea level and may not have previously suffered HAPE even with repeated altitude exposures; this ascent may have been faster than previous ascents. HAPE usually occurs within the first 2 to 4 days of ascent to higher altitudes (above 2500 m), most commonly on the second night.146 Decreased exercise performance and increased recovery time from exercise are the earliest indications of HAPE. The victim usually notices fatigue, weakness, and dyspnea on exertion, especially when trying to walk uphill; he or she often ascribes these nonspecific symptoms to various other causes. Signs of AMS, such as headache, anorexia, and lassitude, are present about 50% of the time.203 A persistent dry cough develops. Nail beds and lips become cyanotic. The condition typically worsens at night, and tachycardia and tachypnea develop at rest. Dyspnea at rest and audible congestion in the chest herald the development of a serious condition. In contrast to the usual 1- to 3-day gradual onset, HAPE may strike abruptly, especially in a sedentary person who may not notice the early stages.455 Orthopnea is uncommon (7%). Pink or blood-tinged, frothy sputum is a very late finding. Hemoptysis was present in 6% in one series.206 Severe hypoxemia may produce cerebral edema with mental changes, ataxia, decreased level of consciousness, and coma. Hultgren and colleagues reported an incidence of HACE of 14% in those with HAPE at ski resorts.206 On admission to the hospital, the victim does not generally appear as ill as would be expected on the basis of arterial blood gas and radiographic findings. Elevated temperature of up to

38.5° C (101.3° F) is common. Tachycardia correlates with respiratory rate and severity of illness (Table 1-5).208 Rales may be unilateral or bilateral and usually originate from the right middle lobe. Concomitant respiratory infection is sometimes present. Patients with pulmonary edema sometimes present with predominantly neurologic manifestations and minimal pulmonary symptoms and findings. Cerebral edema, especially with coma, may obscure the diagnosis of HAPE.157 Pulse oximetry or chest radiography confirms the diagnosis. The differential diagnosis includes pneumonia, bronchitis, mucus plugging, pulmonary embolism or infarct, heart failure, acute myocardial infarction, and sometimes asthma (see Box 1-3). Complications include infection, cerebral edema, pulmonary embolism or thrombosis, and such injuries as frostbite or trauma secondary to incapacitation.19,157,204

Hemodynamics Hemodynamic measurements show elevated pulmonary artery pressure and pulmonary vascular resistance, low to normal pulmonary wedge pressure, and low to normal cardiac output and systemic arterial blood pressure (Table 1-6).205,339 Echocardiography demonstrates high pulmonary artery pressure, tricuspid regurgitation, normal left ventricular systolic function, somewhat abnormal diastolic function,5 and variable rightsided heart findings of increased atrial and ventricular size.160,333 The electrocardiogram usually reveals sinus tachycardia. Changes consistent with acute pulmonary hypertension have been described, such as right axis deviation, right bundle branch block, voltage for right ventricular hypertrophy, and P wave abnormalities.19,203 Atrial flutter has been reported, but ventricular arrhythmias have not.

Laboratory Studies

Kobayashi and colleagues236 reported clinical laboratory values in 27 patients with HAPE that showed mild elevations of hematocrit and hemoglobin, probably secondary to intravascular volume depletion and perhaps plasma leakage into the lung. Elevation of the peripheral white blood cell count is common, but rarely is it greater than 14,000 cells/mL3. The serum concentration of creatine phosphokinase (CPK) is increased. Most of the rise in CPK has been attributed to skeletal muscle damage, although in two patients, CPK isoenzymes showed brain fraction levels of 1% of the total, which may have indicated brain

Chapter 1: High-Altitude Medicine

TABLE 1-6. Hemodynamic Measurements during High-Altitude Pulmonary Edema (HAPE) and after Recovery in Two Subjects and in a Group of 31 Control Subjects MEASUREMENT Sao2% Mean pulmonary artery pressure (mm Hg) Wedge pressure (mm Hg) Cardiac index (L/m2) Pulmonary vascular resistance (dyne/cm−5) Mean arterial blood pressure (mm Hg)

RECOVERY*

CONTROLS†

58.0 63.0

84.0 18.0

89.0 21.3

1.5

3.5

7.1

2.5 1210.0

4.4 169.0

4.1 169.0

—

96.0

HAPE*

82.0

*HAPE and recovery values from Penaloza D, Sime F: Am J Cardiol 23:369–378, 1969. † Mean values from 31 normal subjects studied at 3700 m; from Hultgren HN, Grover RF: Ann Rev Med 19:119–152, 1968.

damage.236 BNP values in patients with HAPE may be normal or elevated. Arterial blood gas studies consistently reveal respiratory alkalosis and marked hypoxemia more severe than expected for the patient’s clinical condition. Because respiratory or metabolic acidosis has not been reported, arterial blood gas studies are unnecessary if noninvasive pulse oximetry is available to measure arterial oxygenation. At 4200 m on Mt. McKinley, the mean value of arterial Po2 in HAPE was 28 ± 4 mm Hg. Values as low as 24 mm Hg in HAPE are not unusual. Arterial oxygen saturation values in HAPE subjects at 4300 m ranged from 40% to 70%, with a mean of 56% ± 8%,406 and at 2928 m, mean Sao2 was 74%.206 Arterial acid–base values may be misleading in patients taking acetazolamide, because this drug produces significant metabolic acidosis.

Radiographic Findings The radiographic findings in HAPE have been described in original reports.208,281,457,458 Findings are consistent with noncardiogenic pulmonary edema, with generally normal heart size and left atrial size and no evidence of pulmonary venous prominence, such as Kerley lines. The pulmonary arteries increase in diameter.458 Infiltrates are commonly described as fluffy and patchy with areas of aeration between them and in a peripheral location rather than central. Infiltrates may be unilateral or bilateral, with a predilection for the right middle lung field, which corresponds to the usual area of rales. Pleural effusion is rare. The radiographic findings generally correlate with the severity of the illness and degree of hypoxemia. A small right hemithorax, absence of pulmonary vascular markings on the right, and edema confined to the left lung are criteria for diagnosis of unilateral absent pulmonary artery.151 Radiographic findings of HAPE are presented in Figure 1-14. Clearing of infiltrates is generally rapid once treatment is initiated. Depending on severity, complete clearing may take from 1 day to several days. Infiltrates are likely to persist longer if

23

the patient remains at high altitude, even if confined to bed and receiving oxygen therapy. Radiographs taken within 24 to 48 hours of return to low altitude may still be able to confirm the diagnosis of HAPE.

Pathologic Findings More than 20 autopsy reports of persons who died of HAPE have been published.10,98,324,421,422,474 Of those whose cranium was opened, more than half had cerebral edema. All lungs showed extensive and severe edema, with bloody, foamy fluid in the airways. Lung weights were 2 to 4 times normal. The left side of the heart was normal. The right atrium and main pulmonary artery were often distended. Proteinaceous exudate with hyaline membranes was characteristic. All lungs had areas of inflammation with neutrophil accumulation. The diagnosis of bronchopneumonia was common, although bacteria were not noted. Pulmonary veins, the left ventricle, and the left atrium were generally not dilated, in contrast to the right ventricle and atrium. Most reports mention capillary and arteriolar thrombi and alveolar fibrin deposits, as well as microvascular and gross pulmonary hemorrhage and infarcts. The autopsy findings thus suggest a protein-rich, permeability-type edema, with thrombi or emboli. Confirmation of HAPE as a permeability edema was obtained by analysis of alveolar lavage fluid by Schoene and associates.404,406 These authors found a 100-fold increase in lavage fluid protein levels in patients with HAPE compared with well control subjects and patients with AMS.406 The lavage fluid also had a low percentage of neutrophils, in contrast to findings in adult respiratory distress syndrome. Further evidence for a permeability edema was a 1 : 1 ratio of aspirated edema fluid protein to plasma protein level found by Hackett and colleagues.150 In addition, the lavage fluid contained vasoactive eicosanoids and complement proteins, indicative of endothelium–leukocyte interactions. More recent research using repeated bronchoalveolar lavage as HAPE was developing found that inflammation was absent early on, suggesting that inflammation is a response to the alveolar damage rather than an initiating event.438

Mechanisms of High-Altitude Pulmonary Edema An acceptable explanation for HAPE must take into account three well-established facts: excessive pulmonary hypertension, high-protein permeability leak, and normal function of the left side of the heart. A mechanism consistent with these facts is failure of capillaries secondary to overperfusion and capillary hypertension (Fig. 1-15).

Role of Pulmonary Hypertension. Excessive pulmonary artery pressure (PAP) is the sine qua non of HAPE; no cases of HAPE have been reported without pulmonary hypertension. All persons ascending to high altitudes or otherwise enduring hypoxia, however, have some elevation of PAP. The hypoxic pulmonary vasoconstrictor response (HPVR) is thought to be useful in humans at sea level because it helps match perfusion with ventilation. When local areas of the lung are poorly ventilated because of infection or atelectasis, for example, the HPVR directs blood away from those areas to well-ventilated regions. In the setting of global hypoxia, as occurs with ascent to high altitude, HPVR is presumably diffuse and all areas of the lung constrict, causing a restricted vascular bed and an increase in PAP, which is of little if any value for ventilation–

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A

B

C

D

Figure 1-14. A, Typical radiograph of high-altitude pulmonary edema (HAPE) in 29-year-old female skier at 2450 m. B, Same patient 1 day after descent and oxygen administration, showing rapid clearing. C, Bilateral pulmonary infiltrates on radiograph of a patient with severe HAPE after descent (case presented in text). D, Ventilation and perfusion scans in person with congenital absence of right pulmonary artery after recovery from HAPE.

Chapter 1: High-Altitude Medicine

25

Altitude hypoxia HVR, sleep, and exercise ↓ PaO2

↑ Sympathetic activity

Uneven HPV Pulmonary and peripheral venous constriction

Exercise PHTN

Overperfusion

↑ Pulmonary blood volume

↑ Pcap

Capillary stress failure ↓ Alveolar Na and H2O clearance Capillary leak

High-altitude pulmonary edema

Figure 1-15. Proposed pathophysiology of high-altitude pulmonary edema. HPV, hypoxic pulmonary vasoconstriction; HVR, hypoxic ventilatory response; Pcap, capillary pressure; PHTN, pulmonary hypertension.

perfusion matching at high altitude. The degree of HPVR varies widely among individuals (as well as among species) and is most likely an inherent trait. Persons who are HAPE susceptible have a greater increase in PAP than those who are not (see HAPE Susceptibility). Although other factors, such as the vigor of the ventilatory response and the subsequent alveolar Po2 value, may help determine the ultimate degree of pulmonary hypertension, HPVR appears to be the dominant factor. Because all persons with HAPE have excessive pulmonary hypertension, but not all those with excessive pulmonary hypertension have HAPE, it appears that pulmonary hypertension is a necessary factor but in itself is not the cause of HAPE.

Overperfusion and Capillary Leak. To explain how pulmonary hypertension might lead to edema, Hultgren suggested that in those who develop HAPE, the hypoxic pulmonary vasoconstriction is uneven and the delicate microcirculation in an unconstricted (relatively dilated) area is subjected to high pressure and flow, leading to leakage (edema). The unevenness could be due to anatomic characteristics, such as distribution of muscularized arterioles, or to functional factors, such as loss of HPVR in severely hypoxic regions.198 Uneven perfusion is suggested clinically by the typical patchy radiographic appearance and is supported by lung scans and MRI during acute hypox-

ia that show uneven perfusion in persons with a history of HAPE.184,456 Persons born without a right pulmonary artery are highly susceptible to HAPE (see Figure 1-14D),151 supporting the concept of overperfusion of a restricted vascular bed as a cause of edema, since the entire cardiac output flows into one lung. Other causes of overperfusion of the pulmonary circulation include left-to-right shunts, such as atrial septal defect (ASD), ventricular septal defect (VSD), and patent ductus arteriosus (PDA). The rapid reversibility of the illness and the response to vasodilators are also consistent with this mechanism. When the hydrostatic pressure is reduced, the alveolar fluid is quickly reabsorbed. Other factors contributing to increased hydrostatic pressure, such as exercise or a high salt load with subsequent hypervolemia, also may play a role in HAPE. In fact, the authors have several times observed onset of HAPE after a large salt intake. Some studies have also suggested a role for pulmonary venous constriction, which would contribute to increased capillary hydrostatic pressure.160,275 The end result of overperfusion and increased capillary pressure275 is distention, increased filtration of fluid, and even rupture of the capillary–alveolar membrane, termed “stress failure,”470,471 with subsequent leakage of cells and proteins.

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Alveolar Fluid Balance. Fluid filtration into the interstitial and alveolar space, reabsorption back across the epithelial membrane, and clearance of interstitial fluid by lymph result in a dynamic balance that generally prevents alveolar flooding. On ascent to altitude, the hydrostatic pressure gradient for filtration is increased. As might be expected, multiple lines of evidence suggest that extravascular lung water is increased at altitude.84,136,460 Despite this, very few people develop frank alveolar flooding. This may well be because of differences in hydrostatic pressure in those resistant and susceptible to HAPE. However, persons who contract HAPE appear to also have an impaired ability to clear alveolar fluid. On a constitutive (genetic) basis, HAPE subjects have lower activity of the epithelial sodium channel (ENaC) and therefore reduced ability to transport sodium across the epithelium back into the interstitial space.280,394,395 (It is the sodium gradient across the epithelium that determines movement of water from the alveolus.) In addition, epithelial sodium transport is diminished by hypoxia per se, so that those with already impaired function become more impaired at altitude. To what extent HAPE may be due to failure of reabsorption of alveolar fluid will require more research185 (see Figure 1-15). Control of Ventilation. As in AMS, control of ventilation may play a role in the pathophysiology of HAPE. Those with HAPE had a lower HVR than persons who acclimatized well,162,285 but not all persons with a low HVR become ill. Thus, low HVR appears to play a permissive, rather than causative, role in the development of HAPE. A brisk HVR, and therefore a large increase in ventilation, appears to be protective. Persons who tend to hypoventilate are more hypoxemic and presumably suffer greater pulmonary hypertension. Possibly more important, a low HVR may permit episodes of extreme hypoxemia during sleep (see Figure 1-6). Supporting this concept is the frequency with which the onset of HAPE occurs during sleep, especially in persons who have ingested sleep medications.146,162 In addition, a HAPE victim with a low HVR does not mount an adequate ventilatory response to the severe hypoxemia of the illness and may suffer further ventilatory depression through central nervous system (CNS) suppression (hypoxic ventilatory depression). Such persons, when given oxygen, show a paradoxical increase in ventilation.162 Despite the correlation of HAPE with low HVR, its value as a sea-level predictor is poor.93

HAPE Susceptibility Persons susceptible to HAPE (HAPE-s) show at sea level an abnormal rise of pulmonary artery pressure and pulmonary vascular resistance during a hypoxic challenge at rest and during exercise, and even during exercise in normoxia, suggesting overreactivity of the pulmonary circulation to both hypoxia and exercise.109,141,224 Part of this reactivity may be related to greater alveolar hypoxemia secondary to lower HVR,162,182,286 but other factors have been uncovered. Microneurographic recordings from the peroneal nerve during hypoxia established a direct link in HAPE-s between the rise in PAP and greater sympathetic activation,106 indicating that sympathetic overactivation might contribute to HAPE. Smaller and less distensible lungs have been noted in HAPE-s, which might limit the ability to accommodate increased flow by vascular recruitment and thus result in higher vascular resistance.109,182,426 Another characteristic of HAPE-s is abnormal endothelial function, as evidenced by reduced nitric oxide (NO) synthesis during hypoxia46,63,400 and during

Nitric oxide - overview

Hypoxia

eNOS

NO

cGMP

L-arginine

Vascular muscle relaxation

Degradation by PDE-5

Figure 1-16. The nitric oxide pathway and action of PDE-5 inhibitors.In the presence of a PDE5 inhibitor, cGMP, the second messenger of NO, is not degraded and vasodilation is therefore enhanced. eNOS, endothelial nitric oxide synthase; NO, nitric oxide; cGMP, cyclic guanosine monophosphate; PDE-5, phosphodiesterase 5.

HAPE,105 and higher levels of endothelin, a potent pulmonary vasoconstrictor.397,427 The importance of reduced NO is reinforced by studies showing improvement in pulmonary hemodynamics when either NO or a phosphodiesterase (PDE)-5 inhibitor, sildenafil or tadalafil, was given to HAPE subjects6,128,272,400 (Fig. 1-16). As mentioned previously, HAPE-s subjects are also characterized by impairment of respiratory transepithelial sodium and water transport, making it harder to reabsorb alveolar fluid396,399 (see Figure 1-15).

Genetics of HAPE The first major genetic studies in lowlanders visiting high altitudes have focused on HAPE because it is the most fully understood pathophysiologic process occurring in lowlanders visiting high altitudes. Although many of the characteristics of HAPEsusceptible persons are apparently genetically determined, actual genetic studies are conflicting and difficult to interpret. Good evidence for a genetic component to HAPE susceptibility comes from study of major human leukocyte antigen (HLA) alleles in 28 male and 2 female subjects with a history of HAPE compared with HLA alleles in 100 healthy volunteers.168 The HLA-DR6 and HLA-DQ4 antigens were associated with HAPE, and HLA-DR6 with pulmonary hypertension. These findings suggest that immunogenetic susceptibility may underlie the development of HAPE, at least in some cases. Given the importance of endothelial function in HAPE, investigators have looked at gene polymorphisms for endothelial nitric oxide synthase (eNOS). Two recent studies have established a link between HAPE-s and the Glu298Asp alleles of the eNOS gene in Japanese and Indian subjects.1,103 An additional study of NOS3-related gene polymorphisms that could explain decreased NO synthesis found no relation to HAPE-s.465 This may be explained by racial differences, or by the specific processes encoded by the different gene fragments. The insertion-deletion polymorphism of the angiotensin-converting enzyme (ACE) gene has also garnered attention, because the renin-aldosterone-angiotensin system (RAAS) is known to be activated in HAPE,29 and the ACE gene has also been linked to performance at altitude.310 The I/D polymorphism was not associated with HAPE susceptibility in populations of Indians, Japanese, and whites.94,186,245 However, one variant of the angiotensin receptor gene was correlated with HAPE susceptibility in Japanese people.186

Chapter 1: High-Altitude Medicine

27

In summary, gene polymorphisms coding for the angiotensin receptor and endothelial nitric oxide distinguish HAPE-sensitive from HAPE-resistant subjects. In the near future, single nucleotide polymorphism scanning techniques, as well as RNA gene expression techniques, will be used to explore genetic contributions to high-altitude physiology and pathophysiology. The search for a genetic basis of HAPE susceptibility continues.102,318

Treatment Treatment choices for HAPE depend on severity of illness and logistics. Early recognition is the key to successful outcome, as with all high-altitude illnesses (see Box 1-4). In the wilderness, where oxygen and medical expertise may be unavailable, persons with HAPE need to be urgently evacuated to lower altitude. However, because of augmented pulmonary hypertension and greater hypoxemia with exercise, exertion must be minimized. If HAPE is diagnosed early, recovery is rapid with a descent of only 500 to 1000 m and the victim may be able to re-ascend slowly 2 or 3 days later. In high-altitude locations with oxygen supplies, bed rest with supplemental oxygen may suffice, but severe HAPE may require high-flow oxygen (4 L/min or greater) for more than 24 hours. Hyperbaric therapy with the fabric pressure bag is equivalent to low-flow oxygen and can help conserve oxygen supplies.361 Oxygen immediately increases arterial oxygenation and reduces pulmonary artery pressure, heart rate, respiratory rate, and symptoms. When descent is not possible, oxygen (or a hyperbaric bag) can be lifesaving. Rescue groups should make delivery of oxygen to the victim, by airdrop if necessary, the highest priority if descent is slow or delayed. If oxygen is not available, immediate descent is lifesaving. Waiting for a helicopter or rescue team has too often proved fatal. Since cold stress elevates PAP, the victim should be kept warm.69 The use of a mask providing pressure (resistance) on expiration (EPAP) was shown to improve gas exchange in HAPE, and this may be useful as a temporizing measure.405 The same is accomplished with pursed-lip breathing. An unusual case report suggested that a climber may have saved his partner’s life by postural drainage to expel airway fluid.50 Drugs are of limited necessity in HAPE, because oxygen and descent are so effective. Medications that reduce pulmonary blood volume, PAP, and pulmonary vascular resistance are physiologically rational to use when oxygen is not available or descent is delayed. Singh and associates421 reported good results with furosemide (80 mg every 12 hours), and greater diuresis and clinical improvement occurred when 15 mg parenteral morphine was given with the first dose of furosemide. Their use, however, has been eclipsed by recent results with vasodilators. The calcium channel blocker nifedipine (30 mg slow release every 12 to 24 hours or 10 mg orally repeated as necessary) was effective in reducing pulmonary vascular resistance and PAP during HAPE, and it slightly improved arterial oxygenation.25 Clinical improvement, however, was not dramatic. Nifedipine is well tolerated and unlikely to cause significant hypotension in healthy persons, and it avoids the danger of CNS depression from morphine and possible hypovolemia from diuretics. Clinical improvement is much better, however, with oxygen and descent than with any medication. Nitric oxide is a potent pulmonary vasodilator and improves hemodynamics in HAPE, but it is rarely available, and in any event it is usually given with oxygen. The PDE-5 inhibitors, which increase cyclic guanosine

Figure 1-17. Chest radiograph of severe HAPE in a 4-year-old girl with a small, previously undiagnosed patent ductus arteriosus that predisposed her to HAPE.

monophosphate (cGMP) to produce pulmonary vasodilation during hypoxia128,356,357 (see Figure 1-16), have shown value for prevention of HAPE272 but have not yet been studied for treatment. Whether these agents will prove to be more effective than nifedipine for treatment is unknown. A theoretical advantage is that the PDE-5 inhibitors produce less systemic vasodilation. Nifedipine, and perhaps other vasodilators, might be useful as adjunctive therapy but are no substitute for definitive treatment (see Box 1-4).144 After evacuation of the victim to a lower altitude, hospitalization may be warranted for severe cases. Treatment consists of bed rest and oxygen (sufficient to maintain Sao2% greater than 90%). Rapid recovery is the rule. A rare instance of progression to adult respiratory distress syndrome has been reported, but it was impossible to exclude other diagnoses completely.495 Antibiotics are indicated for infection when present. Occasionally, pulmonary artery catheterization or Doppler echocardiography is necessary to differentiate cardiogenic from high-altitude pulmonary edema. Endotracheal intubation and mechanical ventilation are rarely needed. A HAPE victim demonstrating unusual susceptibility, such as onset of HAPE despite adequate acclimatization, or onset below 2750 m, might require further investigation, such as echocardiography, to rule out an intracardiac shunt. In children, undiagnosed congenital heart disease is worth considering (Fig. 1-17). Hospitalization until blood gases are completely normal is not warranted; all persons returning from high altitude are at least partially acclimatized to hypoxemia, and hypocapnic alkalosis persists for days after descent. Distinct clinical improvement, radiographic improvement over 24 to 48 hours, and an arterial Po2 of 60 mm Hg or a Sao2% greater than 90% are adequate discharge criteria. Patients are advised to resume normal activities gradually and are warned that they may require up to 2 weeks to recover complete strength. Physicians should recommend preventive measures, including graded ascent with adequate time for acclimatization, and should provide instruction on the use of acetazolamide, nifedipine, or PDE-5 inhibitors for future

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ascents. An episode of HAPE is not a contraindication to subsequent high-altitude exposure, but education to ensure proper preventive measures and recognition of early symptoms is critical.

Prevention The preventive measures previously described for AMS also apply to HAPE: graded ascent, time for acclimatization, low sleeping altitudes, and avoidance of alcohol and sleeping pills (see Box 1-4). Exertion may contribute to onset of HAPE, especially at moderate altitude. Reports from North America at 2500 to 3800 m have included hikers, climbers, and skiers, all of whom were exercising vigorously. Menon296 clearly showed that sedentary men taken abruptly to higher altitude were just as likely to become victims of HAPE. Prudence dictates not overexerting for the first 2 days at altitude. Considerable clinical experience suggests that acetazolamide prevents HAPE in persons with a history of recurrent episodes. Recent work showing that acetazolamide blocks hypoxic pulmonary hypertension supports this practice.45,240 Nifedipine (20 mg slow release every 8 hours) prevented HAPE in subjects with a history of repeated episodes.25 The drug should be carried by such individuals and started at the first signs of HAPE or, for an abrupt ascent, started when leaving low altitude. The PDE-5 inhibitors sildenafil and tadalafil effectively block hypoxic pulmonary hypertension and will also prevent HAPE.272 The optimal dosage has not been established; regimens for sildenafil have varied from a single dose of 50 or 100 mg just prior to exposure for acute studies,128,356 to 40 mg three times a day for 2 to 6 days at altitude,340,357 and for tadalafil, 10 mg every 12 to 24 hours.115,272 Most recently, and rather surprisingly, dexamethasone was found effective in preventing HAPE in susceptible subjects. Maggiorini and colleagues gave 8 mg dexamethasone every 12 hours, starting 2 days prior to exposure, and found it as effective as tadalafil in reducing PAP and preventing HAPE.272 Dexamethasone has many actions in the lung, and which action might be responsible for this observed effect is unknown.27 As evidenced by this list of therapies, any agent that blocks hypoxic pulmonary hypertension will block onset of HAPE, reinforcing the concept of pulmonary hypertension as the sine qua non of high-altitude pulmonary edema.

Reentry Pulmonary Edema In some persons who have lived for years at high altitude, HAPE develops on re-ascent from a trip to low altitude.107 Authors have suggested that the incidence of HAPE on re-ascent may be higher than that during initial ascent by flatlanders,29,200 but data on true incidence are difficult to obtain. Children and adolescents are more susceptible than adults.107 Hultgren199 found a prevalence of HAPE in Peruvian natives of 6.4 per 100 exposures in the 1- to 20-year age group, and 0.4 per 100 exposures in persons over 21 years. The phenomenon has been observed most often in Peru, where high-altitude residents can return from sea level to high altitude quite rapidly. Cases have also been reported in Leadville, Colorado,408 but reports are conspicuously rare from Nepal and Tibet,482 perhaps because such rapid return back to high altitude is not readily available.485 Severinghaus411 has postulated that the increased muscularization of pulmonary arterioles that develops with chronic highaltitude exposure generates an inordinately high pulmonary artery pressure on re-ascent, causing the edema.


OTHER MEDICAL CONCERNS AT HIGH ALTITUDE

High-Altitude Deterioration The world’s highest human habitation is at approximately 5500 m, and above this altitude, deterioration outstrips the ability to acclimatize.229 The deterioration is more rapid the higher one goes above the maximum point of acclimatization. Above 8000 m, deterioration is so rapid that without supplemental oxygen, death can occur in a matter of days.461 Lifepreserving tasks such as melting snow for water may become too difficult, and death may result from dehydration, starvation, hypothermia, and especially neurologic and psychiatric dysfunction.387 Loss of body weight is a prominent feature of high-altitude deterioration. Body weight is progressively lost because of anorexia and malabsorption during expeditions to extreme high altitude. Pugh345 reported a 14 to 20 kg body weight loss in climbers on the 1953 British Mt. Everest Expedition. Nearly 30 years later, with improvement in food and cooking techniques, climbers on the American Medical Research Expedition to Mt. Everest still lost an average of 6 kg.54 This was due in part to a 49% decrease in fat absorption and a 24% decrease in carbohydrate absorption. During OEII, in which the “climbers” were allowed to eat foods of their choosing ad libitum, they still suffered large weight losses: 8 kg overall, including 3 kg of fat and 5 kg of lean body weight (muscle).191,384 At 4300 m, weight loss was attenuated by adjusting caloric intake to match caloric expenditure.64 Thus, significant weight loss with prolonged exposure to high altitude may be overcome with adequate caloric intake, but decreased appetite is a problem.226,446 At very high altitudes, an increase in caloric intake may not be sufficient to completely counteract the severe anorexia and weight loss, as other mechanisms may come into play. At extreme altitude, Ryn387 reported an incidence of acute organic brain syndrome in 35% of climbers going above 7000 m, in association with high altitude deterioration. This syndrome, with its features of frank psychosis and impaired judgment, could directly threaten survival.

Children at High Altitude Children born at high altitude in North America appear to have a higher incidence of complications in the neonatal period than do their lower altitude counterparts.329 In populations better adapted to high altitude over many generations, neonatal transition has not been as well scrutinized, but there does appear to be some morbidity.473 High-altitude residence does not clearly impact eventual stature, but growth and development are slowed.92,314 In the developing world, confounding factors such as nutrition and socioeconomic status make these issues difficult to assess.195 Children residing at high altitude are more likely to develop pulmonary edema on return to their homes from a low-altitude sojourn than are lowland children on induction to high altitude. Some of these children may have preexisting pulmonary hypertension of various causes.90 Lowland children traveling to high altitude are just as likely to suffer AMS as are adults.344 No data indicate that children are more susceptible to altitude illness, although diagnosis can be more difficult in preverbal children.489 Despite this somewhat reassuring fact, very conservative recommendations are made regarding taking children to high altitude; it should be made

Chapter 1: High-Altitude Medicine clear that these opinions are not based on science.35,343 Durmowicz and colleagues showed that children with respiratory infections were more susceptible to HAPE.107 Children can be given acetazolamide or dexamethasone as necessary for AMS or HACE. The dosage of acetazolamide for prevention or treatment of AMS in children is 5 mg/kg/day in divided doses. See Pollard and colleagues for an excellent consensus document on children at altitude.344

High-Altitude Syncope Syncope within the first 24 hours of arrival occurs occasionally at moderate altitude325,326 but is not observed in mountaineers at higher altitudes; it is a problem of acute induction to altitude. The mechanism is an unstable cardiovascular control system, and it is considered a form of neurohumoral (or neurocardiogenic) syncope.119 An unstable state of cerebral autoregulation may also play a role.492 These events appear to be random and seldom occur a second time. Preexisting cardiovascular disease is not a factor in most cases. Postprandial state and alcohol ingestion seem to be contributing factors. Altitude syncope has no direct relationship to high-altitude illness.36

Alcohol at High Altitude Two questions regarding alcohol are frequently asked: (1) does alcohol affect acclimatization, and (2) does altitude potentiate the effects of alcohol? Epidemiologic research indicated that 64% of tourists ingested alcohol during the first few days at 2800 m.183 The effect of alcohol on altitude tolerance and acclimatization might therefore be of considerable relevance. Roeggla and colleagues determined blood gases 1 hour after ingestion of 50 g of alcohol (equivalent to 1 L of beer) at 171 m and again after 4 hours at 3000 m. A placebo-controlled, double-blinded, paired design was used. For the 10 subjects, alcohol had no effect on ventilation at the low altitude, but at the high altitude it depressed ventilation, as gauged by a decreased arterial Po2 (from 69 to 64 mm Hg) and increased Pco2 (from 32.5 to 34 mm Hg).379 Whether this degree of ventilatory depression would contribute to AMS and whether repeated doses would have greater effect were not tested. Nonetheless, the authors argue that alcohol might impede ventilatory acclimatization and should be used with caution at high altitude. Conventional wisdom proffers an additive effect of altitude and alcohol on brain function. McFarland, who was concerned about the interaction in aviators, wrote, “The alcohol in two or three cocktails would have the physiological action of four or five drinks at altitudes of approximately 10,000 to 12,000 feet.”291 Also, “Airmen should be informed that the effects of alcohol are similar to those of oxygen want and that the combined effects on the brain and the CNS are significant at altitudes even as low as 8,000 to 10,000 feet.”291 His original observations were made on two subjects in the Andes in 1936. He found that blood alcohol levels rose more rapidly and reached higher values at altitude, but he noted no interactive effect of alcohol and altitudes of 3810 and 5335 m.292 Most subsequent studies refuted the increased blood alcohol concentration data except at the highest altitudes, over 5450 m. Higgins and colleagues, in a series of chamber studies,177,178 found blood alcohol levels were similar at 392 m and at 3660 m, and they noted no synergistic effects of alcohol and altitude. Lategola and colleagues253 found that blood alcohol uptake curves were the

29

same at sea level and at 3660 m, and performance on math tests showed no interaction between alcohol and altitude. In another study of 25 men, performance scores were similar at sea level and at a simulated 3810-m altitude, with a blood alcohol level of 88 mg%.77 Performance was not affected by hypoxia, only by alcohol, and older subjects were more affected. When more demanding tasks were tested, Collins found that a blood alcohol level of 91 mg% affected performance, as did an altitude of 3660 m during night sessions when the subjects were sleep deprived, but there was no significant interaction between altitude and alcohol.76 In the one study in which Collins and colleagues were able to discern some altitude effect, there was a simple additive interaction of altitude (hypoxic gas breathing) and alcohol.78 He concluded that performance decrements due to alcohol might be increased by altitudes of 3660 m (12,000 feet) if subjects are negatively affected by that altitude without alcohol. All of these aviation-oriented studies used acute hypoxia equivalent to no more than 3500 m. Perhaps the highest altitude (without supplemental oxygen) at which alcohol was studied was 4350 m, on the summit of Mt. Evans in Colorado. Freedman and colleagues found that alcohol affected auditory evoked potentials to the same extent as that seen in Denver—that is, no influence of altitude was detectable.118 In summary, the limited data on blood gases at altitude after alcohol ingestion support the popular notion that alcohol could slow ventilatory acclimatization and therefore might contribute to AMS. Considerable data at least up to 3660 m, however, refute the belief that altitude potentiates the effect of alcohol. How altitude and alcohol might interact during various stages of acclimatization in individuals at higher altitudes is still unknown.

Thrombosis: Coagulation and Platelet Changes After deaths due to altitude illness, autopsy findings of widespread thrombi in the brain and lungs, as well as the impression that thrombosis is greater at altitude,219 have led to many investigations of the clotting mechanism at high altitude. For a review, see Grover and Bärtsch.139 Although changes in platelets and coagulation have been observed in rabbits, mice, rats, calves, and humans on ascent to high altitude,174 these generally occur with very rapid ascent. In vivo studies using more realistic ascent profiles up to 4500 m in the mountains, and higher in chambers, have generally not found changes in coagulation and fibrinolysis.139 Although the increased incidence of thrombosis in soldiers and others at extreme altitude can be attributed to dehydration, polycythemia, and forced inactivity, there is some evidence of enhanced fibrin formation with a stay of a few weeks above 5000 m.379 As for thrombosis in HAPE, Singh and colleagues419 reported increased fibrinogen levels and prolonged clot lysis times during HAPE, attributed to a breakdown of fibrinolysis. These authors also reported thrombotic, occlusive hypertensive pulmonary vascular disease in soldiers who had recently arrived at extreme altitude.418 A series of experiments by Bärtsch and colleagues, however, carefully examined this issue in well subjects and in those with AMS and HAPE.22,139 They concluded that HAPE is not preceded by a prothrombotic state and that only in “advanced HAPE” is there fibrin generation, which abates rapidly with oxygen treatment. They considered the coagulation and platelet activation as an epiphenomenon rather than as an inciting pathophysiologic factor, and most likely due to

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inflammation from the structural damage to the capillaries or the extreme hypoxemia. A difficult clinical question is whether ascent to altitude might result in thrombosis in persons with familial thrombophilia, such as factor V Leiden, a common anomaly, or protein C deficiency, antiphospholipid syndrome, or others. Such cases have been reported,33,53 but cause and effect cannot be established. In addition, persons with a past history of deep vein thrombosis or pulmonary embolism wonder if they are at increased risk at high altitude, as do women on hormonal contraceptives. Unfortunately, the literature does not help provide guidance for these individuals. Some experts empirically recommend an aspirin a day during altitude exposure for such patients, and this seems to be a safe suggestion. Others have raised the possibility that aspirin therapy might cause or exacerbate retinal hemorrhages at high altitude. Although no study has investigated this at altitude, research from patients with diabetic retinopathy has shown no danger of increased hemorrhages from aspirin.17 In addition, a retinal hemorrhage in a climber was treated with aspirin, and the hemorrhage resolved.248

Peripheral Edema Edema of the face, hands, and ankles at high altitude is common, especially in females. Incidence of edema in at least one area of the body in trekkers at 4200 m was 18% overall, 28% in women, 14% in men, 7% in asymptomatic trekkers, and 27% in those with AMS.153 Although not a serious clinical problem, edema can be bothersome. The presence of peripheral edema demands an examination for pulmonary and cerebral edema. In the absence of AMS, peripheral edema is effectively treated with a diuretic. Treatment of accompanying AMS by descent or medical therapy also results in diuresis and resolution of peripheral edema. The mechanism is presumably similar to fluid retention in AMS, but it may also be merely due to exercise.299

Immunosuppression Mountaineers have observed that infections are common at high altitude, slow to resolve, and often resistant to antibiotics.321 On the American Medical Research Expedition to Mt. Everest in 1981, serious skin and soft tissue infections developed. “Nearly every accidental wound, no matter how small, suppurated for a period of time and subsequently healed slowly.”393 A suppurative hand wound and septic olecranon bursitis did not respond to antibiotics but did respond to descent to 4300 m from the 5300-m base camp. Nine of 21 persons had significant infections not related to the respiratory tract. Most highaltitude expeditions report similar problems. Data from OEII indicated that healthy individuals are more susceptible to infections at high altitude because of impaired Tlymphocyte function; this is consistent with previous Russian studies in humans and animals.295 In contrast, B cells and active immunity are not impaired. Therefore, resistance to viruses may not be impaired, whereas susceptibility to bacterial infection is increased. The degree of immunosuppression is similar to that seen with trauma, burns, emotional depression, and space flight. The mechanism may be related, at least in part, to release of adrenocorticotropic hormone, cortisone, and beta-endorphins, all of which modulate the immune response. Intense ultraviolet exposure has also been shown to impair immunity. Persons with serious infections at high altitude may need oxygen or descent for effective treatment. Impaired immunity because of altitude

should be anticipated in situations where infection could be a complication, such as trauma, burns, and surgical and invasive procedures.

High-Altitude Pharyngitis and Bronchitis Sore throat, chronic cough, and bronchitis are nearly universal in persons who spend more than 2 weeks at an extreme altitude (over 5500 m).263,283 All 21 members of the 1981 American Medical Research Expedition to Mt. Everest suffered these problems.393 Only two of eight subjects in OEII (where the temperature was greater than 21° C [70° F] and relative humidity was greater than 80%) developed cough, and only above 6500 m. Only four had sore throat. Acute hypoxia directly lowers the cough threshold, thus exacerbating high-altitude cough.283 But other factors are at play. In the field, these problems usually appear without fever or chills, myalgia, lymphadenopathy, exudate, or other signs of infection. The increase in ventilation, especially with exercise, forces obligate mouth breathing at altitude, bypassing the warming and moisturizing action of the nasal mucous membranes and sinuses. Movement of large volumes of dry, cold air across the pharyngeal mucosa can cause marked dehydration, irritation, and pain, similar to pharyngitis. Vasomotor rhinitis, quite common in cold temperatures, aggravates this condition by necessitating mouth breathing during sleep. For this reason, decongestant nasal spray is one of the most coveted items in an expedition medical kit. Other countermeasures include forced hydration, hard candies, lozenges, and steam inhalation. High-altitude bronchitis can be disabling because of severe coughing spasms. Cough fractures of one or more ribs are not rare.263 Purulent sputum is common. Response to antibiotics is poor; most victims resign themselves to taking medications such as codeine and do not expect a cure until descent. Bronchitis developed in 13 of 19 climbers above 4300 m on Aconcagua.347 Mean sputum production was 6 teaspoons per day. All reported that onset was after a period of excessive hyperventilation associated with strenuous activity. Although an infectious etiology is possible, experimental evidence suggests that respiratory heat loss results in purulent sputum and in sufficient airway irritation to cause persistent cough.290 This is supported by the beneficial effect of steam inhalation and lack of response to antibiotics. Many climbers find that a thin balaclava, porous enough for breathing, traps some moisture and heat and effectively prevents or ameliorates the problem.

Chronic Mountain Sickness In 1928 Carlos Monge307 described a syndrome in Andean highaltitude natives that was characterized by headaches, insomnia, lethargy, plethoric appearance, and polycythemia greater than expected for the altitude. Known variously as Monge’s disease, chronic mountain polycythemia, and chronic mountain sickness (CMS), the condition has now been recognized in all highaltitude areas of the world.244,306,338 Both lowlanders who relocate to high altitude and native residents are susceptible. Chinese investigators reported that 13% of lowland Chinese males and 1.6% of females who had relocated to Tibet developed excessive polycythemia (hemoglobin level greater than 20 g/dL blood).486 The incidence in Leadville, Colorado, is also high in men over age 40 and distinctly low in women.243 The increased hematopoiesis is apparently related to greater hypoxic stress, which may have a number of causes, such as lung disease, sleep apnea syndromes, and idiopathic hypoventilation. A diag-

Chapter 1: High-Altitude Medicine nosis of “pure” chronic mountain polycythemia excludes lung disease and is characterized by relative alveolar hypoventilation, excessive nocturnal hypoxemia, and respiratory insensitivity to hypoxia.257,306 Some studies suggest that even for the degree of hypoxemia, the red blood cell mass is excessive, implying excessive amounts or overactivity of erythropoietin.475 The new international guidelines propose a hemoglobin value greater than 21 g/dL for men and 19 g/dL for women as essential for the diagnosis, as well as residence above 2500 m and absence of lung disease.257 The reader is referred to recent reviews for in-depth information.305,350,352,484 In addition, an international consensus group has recently published their papers on definition and scoring of CMS.256,257 Therapy of CMS is routinely successful. Descent to a lower altitude is the definitive treatment. The syndrome reappears after returning to high altitude. Supplemental oxygen during sleep is valuable. Phlebotomy is a common practice and provides subjective improvement, although without significant objective changes.475 The respiratory stimulants medroxyprogesterone acetate (20 to 60 mg/day)242 and acetazolamide (250 or 500 mg/day)359 have also been shown to reduce the hematocrit value by improving oxygenation. Acetazolamide (250 mg) increased nocturnal Sao2 by 5%, decreased mean nocturnal heart rate by 11% and the number of apnea/hypopnea episodes during sleep by 74%, and decreased hematocrit by 7%.359 The response to acetazolamide emphasizes the contribution of hypoventilation and nocturnal desaturation to CMS. Another approach was based on the knowledge that ACE inhibitors blunt hypoxia-mediated erythropoietin release. Plata and colleagues showed that 5 mg/day of enalapril for 2 years reduced hemoglobin concentration, packed cell volume, and proteinuria, and reduced the need for phlebotomy.342 Pulmonary hypertension and right heart failure may also occur in those with CMS.

High-Altitude Pulmonary Hypertension High-altitude pulmonary hypertension (HAPH) is a syndrome occurring in children and adults living over 2500 m. It is characterized by a mean pulmonary artery pressure greater than 30 mm Hg or a systolic pressure greater than 50 mm Hg, measured at the altitude of residence; it is associated with right ventricular hypertrophy and heart failure, and the absence of CMS.257 Historical terms for this condition include subacute adult and subacute infantile mountain sickness, and highaltitude heart disease. Symptoms include cough, cyanosis, dyspnea, and signs of right heart failure. Treatment is similar to that for CMS, with relocation to a low altitude the best solution. Other but inferior therapies include supplemental oxygen, and pulmonary vasodilators such as calcium channel blockers, PDE5 inhibitors, and nitric oxide and prostaglandin inhibitors.257

High-Altitude Retinopathy and Ultraviolet Keratitis

Box 1-5. Advisability of Exposure to High and Very High Altitude for Common Conditions (without Supplemental Oxygen) PROBABLY NO EXTRA RISK

Young and old Fit and unfit Mild obesity Diabetes Previous coronary artery bypass grafting (without angina) Mild chronic obstructive pulmonary disease (COPD) Asthma Low-risk pregnancy Controlled hypertension Controlled seizure disorder Psychiatric disorders Neoplastic diseases Inflammatory conditions CAUTION

Moderate COPD Asymptomatic pulmonary hypertension Compensated congestive heart failure (CHF) Morbid obesity Sleep apnea syndromes Troublesome arrhythmias Stable angina or coronary artery disease High-risk pregnancy Sickle cell trait Cerebrovascular diseases Any cause of restricted pulmonary circulation Seizure disorder (not on medication) Radial keratotomy CONTRAINDICATED

Sickle cell anemia (with history of crises) Severe COPD Symptomatic pulmonary hypertension Uncompensated CHF

populations also require special consideration, such as the very young, the pregnant, and older adults. This section presents an overview of current knowledge regarding these issues. Despite the importance of the interaction of altitude and common medical conditions, research has so far been limited. See the review by Hackett for a more complete discussion.149 Conditions that can be aggravated by high-altitude exposure are listed in Box 1-5.

See Chapter 25.

Respiratory Diseases


COMMON MEDICAL CONDITIONS

Chronic Lung Disease

AND HIGH ALTITUDE

Persons with certain preexisting illnesses might be at risk for adverse effects on ascent to high altitude, either because of exacerbation of their illnesses or because these illnesses might impact acclimatization and susceptibility to altitude illness. Certain

31

While oxygen saturation remains above 90% in a normally acclimatizing, healthy, awake person until over 3000 m (see Figure 1-1), persons with hypoxemic lung disease reach this threshold at a lower altitude that depends on the baseline blood oxygen values. As a result, these persons might have altituderelated problems at lower altitudes than would healthy individuals. In terms of their lung disease, improved airflow will

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result from decreased air density at high altitude, but hypoxemia, pulmonary hypertension, disordered control of ventilation, and sleep-disordered breathing could all become worse. Unfortunately, few data are available to guide the clinician advising such a person undertaking a trip to altitude.74 Hypoxic gas breathing at sea level can predict oxygenation at high altitude, but this does not always correlate with symptoms, and it is not convenient. Sea level Po2 values of 68 and 72 mm Hg successfully classified more than 90% of the subjects with a Pao2 greater than 55 mm Hg at simulated altitudes of 1525 m and 2440 m, respectively.132,133 Such predictions have been further refined with the addition of spirometry.101 A Pao2 of 55 mm Hg results in a saturation of 90% at high altitude, where there is slight alkalosis. These data suggested that persons with Pao2 values lower than these at sea level might require supplemental oxygen at modest altitudes. However, in the only clinical studies to date, patients with moderate chronic obstructive pulmonary disease (COPD) did quite well at altitude.135,289 Graham and Houston found that eight subjects with COPD taken to 1920 m had only minor symptoms on ascent, despite the fact that mean Pao2 declined from 66 mm Hg at sea level to 51 mm Hg while at rest, and from 63 to 47 mm Hg with exercise. The patients did acclimatize, with a drop in Pco2 and a corresponding increase in Pao2 over 4 days, the same response as seen in healthy persons. Matthys and colleagues studied 10 patients at a simulated altitude of 2500 m. Mean PAP increased from 21 to 25 mm Hg, Pao2 decreased from 68 to 51 mm Hg at rest, and the only symptom was an increase in fatigue.289 The authors concluded that travel to this moderate altitude is safe for such patients. They speculated that these persons might have been partially acclimatized because of their hypoxic lung disease, and they were therefore less likely to develop AMS. Unfortunately, no further investigations with sicker patients or at higher altitudes have yet been reported. Persons with COPD who become uncomfortable at altitude should be treated with oxygen therapy. Oxygen should also be considered for those predicted to become severely hypoxemic.43 To adjust oxygen therapy at altitude for persons already on supplemental oxygen, the fractional concentration of O2 in inspired gas (Fio2) is increased by the ratio of higher to lower barometric pressure (see Table 1-2). Oxygen also improved hemodynamics (lowered blood pressure) and decreased pulsus paradoxus and pulse pressure in patients with COPD at a simulated altitude of 2438 m.44 With the advent of simple and inexpensive pulse oximetry, patients can be counseled to monitor their oxygen saturation, determine the need for oxygen, and titrate their own oxygen use. Interestingly, reports of patients with COPD developing altitude illness are absent from the literature. On the other hand, the issue has not been specifically addressed. Any degree of pulmonary hypertension might be expected to increase the likelihood of HAPE, and although this has been clearly demonstrated in other conditions (see High-Altitude Pulmonary Edema), it has not yet been reported with pulmonary hypertension associated with COPD. No research has yet addressed the use of medications such as acetazolamide or medroxyprogesterone in these patients, to determine if respiratory stimulants might improve altitude tolerance.

Cystic Fibrosis Children with cystic fibrosis have been reported to do poorly at high altitude,425 and hypoxic testing has also tried to predict the

need for supplemental oxygen on ascent in this condition.331,383 As with COPD, such tests are not particularly useful and tend to underestimate the oxygen requirements, as they are done only during rest and while awake. Supplemental oxygen should be available for these children, and oxygen saturation monitoring might be desirable in certain circumstances. The physician should be liberal with the use of antibiotics and adjunctive therapy for exacerbations at high altitude, given the likely danger of greater hypoxemia and the greater difficulty of treating infections at high altitude. Cystic fibrosis encompasses a wide range of pulmonary impairment; one patient with mild disease was able to hike to 5600 m.74

Asthma The available literature suggests that people with asthma, both residents and sojourners, do well at moderate altitude, primarily because of decreased allergens and pollution.51,417,452 Indeed, high altitude as a treatment for asthma has been popular in Europe for many decades. The effect is comparable to that seen with high dosages of inhaled steroids.74 However, because altitude exposure often includes exercise (and cold), people with asthma who have exercise-induced bronchospasm, rather than allergic asthma, might have problems at altitude. Matsuda and colleagues284 investigated the effect of altitude on 20 asthmatic children with exercise-induced bronchospasm in a hypobaric chamber simulating 1500 m, but with the temperature and humidity held constant. Except for the increased respiratory rate during exercise, as expected, all other physiologic variables were unchanged compared with those at sea level. The authors concluded that the modest altitude of 1500 m does not exacerbate exercise-induced asthma. Golan and colleagues screened travelers and found 147 people with asthma who trekked to high altitude. Risk factors for an asthma attack at altitude were use of inhaled bronchodilators more than three times a week prior to travel, and intensive physical exertion during the trek.130 A small but careful study was done with 11 people with asthma who were in stable condition with normal respiratory function at sea level. Cogo and her colleagues tested both methacholine challenge and hyperosmolar aerosol at sea level and multiple altitudes up to 5050 m. At no altitude was there an increase in bronchial responsiveness, and at the highest altitude there was a decrease.73 They concluded that the positive aspects of high altitude prevailed over potential negative factors for people with asthma, and they attributed the benefit to the increase in circulating catecholamines found in their subjects. In the presence of bronchoconstriction at high altitude, however, hypoxemia is likely to be greater than at low altitude, and for this reason there could be an association between asthma and HAPE or AMS. Reassuringly, no such relationship has yet been reported. Mirrakhimov and colleagues investigated the effect of acetazolamide in 16 asthmatic patients taken to 3200 m. Taking acetazolamide resulted in these patients’ having the same benefits as people without asthma, with higher oxygen saturation and fewer AMS symptoms compared with the placebo control group.303 Seven of the eight asthmatic patients in the control group developed symptoms of AMS, a rather high incidence, but there was no nonasthmatic control group for comparison. Whether this incidence was abnormal is unknown. Persons with asthma ascending to high altitude should be advised to be at maximal function before ascent, to continue on their usual medications, including steroids, and to have steroids

Chapter 1: High-Altitude Medicine and bronchodilators with them in the event of an exacerbation. Because airway heat loss can be a trigger for bronchospasm, the use of an airway warming mask might be helpful, but this is unproven.385 In summary, the available data, although limited, suggest that high altitude does not exacerbate asthma, and that it actually improves allergic asthma. Further work needs to determine if asthma might have any influence on susceptibility to AMS and HAPE; anecdotally, this does not seem to be the case. Although it seems likely that a severe asthma attack at high altitude would be more dangerous than at low altitude, no data are available to answer this question. Although caution and adequate preparation are necessary, asthma is not a contraindication to high-altitude travel.

Pulmonary Vascular Disorders Because of the danger of HAPE, pulmonary hypertension (of any etiology) is at least a relative contraindication to highaltitude exposure. In addition, hypoxic pulmonary vasoconstriction will most likely exaggerate preexisting pulmonary hypertension and could lead to more significant symptoms in those with congenital cardiac defects, primary pulmonary hypertension (PPH), and related disorders. This caution also applies to unilateral absent pulmonary artery, granulomatous mediastinitis, and restrictive lung diseases, all of which have been associated with HAPE.151,361,444 As Hultgren has observed, however, some patients with PPH are able to tolerate high altitude, and hypoxic gas breathing can be used to identify an individual’s response to hypoxia if clinically indicated. Persons with PPH who must travel to high altitude might benefit from calcium channel blockers, isoproterenol, and/or low flow oxygen.202 A report by Naeije and colleagues highlighted the increased susceptibility to HAPE in those with pulmonary hypertension: a lowland woman with pulmonary hypertension secondary to fenfluramine developed two episodes of HAPE.323 The first episode was at 2300 m, and the second one at only 1850 m, with skiing up to 2350 m. Other conditions warranting caution include bronchopulmonary dysplasia, recurrent pulmonary emboli, mitral stenosis, kyphoscoliosis, and scleroderma. Whether pulmonary hypertension is primary or secondary, patients should be made aware of the potential hazards of high altitude, including right heart failure and HAPE. A mean PAP of greater than 30 mm Hg is a useful threshold for caution (or oxygen) on ascent to altitude.74

Sleep Apnea, Sleep-Disordered Breathing Persons with snoring, sleep apnea syndrome, and sleepdisordered breathing (SDB) who become mildly hypoxemic at sea level may become severely hypoxemic at high altitude. This could contribute to high-altitude illness and aggravate attendant problems such as polycythemia, pulmonary hypertension, cardiac arrhythmia, or insomnia. On the other hand, changes in ventilatory control and breathing secondary to altitude hypoxia might conceivably improve certain apnea syndromes. In general, the scant research available has shown that obstructive sleep apnea tends to improve at altitude, whereas central apnea can become worse.57a Patients with SDB being treated with continuous positive airway pressure (CPAP) should be aware that the hypobaria of high altitude decreases the delivered pressure of CPAP machines that do not have pressurecompensating features. They therefore might need to adjust their machines. The error is greater at higher altitude and higher initial pressure setting.120 For those not being treated with CPAP

33

but who exhibit hypoxemia during sleep at low altitude, the physician might want to consider supplemental nocturnal oxygen during an altitude sojourn.

Cardiovascular Conditions Hypertension In healthy persons rapidly ascending to high altitude, the change in blood pressure, if any, is variable, depending on the magnitude of hypoxic stress, cold, diet, exercise, and genetic factors. Most studies report a slight increase in blood pressure, associated with increased catecholamine activity and increased sympathetic activity.348 One well-controlled study showed an increase in blood pressure at 3500 m from a mean of 105/66 mm Hg at sea level to 119/77 mm Hg at 3 days, 111/75 mm Hg at 3 weeks, and back to 102/65 mm Hg on return to sea level.282 Pugh reported transient increases in blood pressure in athletes at the Olympics in Mexico City.346 Certain individuals, however, appear to have a pathologic response on induction to high altitude. For example, arterial hypertension develops in 10% of lowland Chinese who move to Tibet.414 The authors consider this a form of altitude maladaptation and treat the condition by returning the affected individuals to low altitude. After a period of at least 2 months, however, downregulation of adrenergic receptors results in attenuation of the initial blood pressure response. This mechanism is thought to be the reason that longterm residents of high altitude have lower blood pressure than do their sea level counterparts.201,376 Apparently for the same reason, chronic altitude exposure has also been shown to inhibit progression of hypertension.302 As for the effect of short-term altitude exposure on preexisting hypertension, studies have generated mixed results. In general, the response in patients with hypertension is similar to that in those without hypertension—that is, a small increase in blood pressure, with an exaggerated response in some individuals. The greater the hypoxic stress (the higher the altitude), the greater is the change in blood pressure. Altitudes less than 3000 m seem to result in little if any change.369 Palatini and colleagues studied 12 normotensive patients and 12 untreated mild hypertensive patients with 24-hour ambulatory blood pressure monitoring at sea level, after 12 hours at 1210 m and after 1.5 to 3 hours at 3000 m.335 The authors concluded that the increase of blood pressure in both normotensive and hypertensive patients was not important at 1200 m but could become so at 3000 m. However, individual variability was great; the maximal change was 17.4 mm Hg for systolic and 16.3 for diastolic blood pressure. Two other studies were able to demonstrate a slightly greater blood pressure response in hypertensive compared with normotensive patients on ascent to 2572 and 3460 m.89,398 Again, these authors also noted important individual variation, with some subjects increasing their systolic blood pressure by as much as 25 mm Hg at rest and 40 mm Hg during exercise, compared with sea level measurements. The important question of whether the blood pressure would continue to increase over the first 2 weeks at high altitude, as it does in normotensive patients, has not yet been addressed. At a more modest altitude, Halhuber and coworkers claimed a significant reduction in the blood pressure of 593 persons with hypertension after 14 days at 1700 to 2000 m in the Alps.166 A similar study of hypertensive patients at higher altitude is needed. Patients receiving antihypertensive treatment should continue their medications while at high altitude. Because some persons

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may unpredictably become markedly hypertensive acutely,202 blood pressure monitoring should be considered, especially in those with labile hypertension or those who become symptomatic at altitude. Hypertension in short-term high-altitude sojourners for the most part should be considered transient and should not be treated, as it rarely reaches dangerously high levels and will resolve on descent. Given the large number of hypertensive patients visiting ski resorts and trekking at high altitude, however, the occasional person with an exaggerated response will require treatment.202 Because the mechanism appears to be increased alpha-adrenergic activity, an alphablocker might be the best choice of therapy for these individuals. A preliminary report also suggested that nifedipine might be useful, and superior to atenolol.95 The best medication, dosage, and duration still need to be determined. There is no evidence to date to suggest that hypertensive patients are more likely to develop high-altitude illnesses. Although it requires some caution, hypertension does not seem to be a contraindication to high-altitude exposure.

Arteriosclerotic Heart Disease Life-long residence at high altitude appears to offer some protection from coronary artery disease and the attendant acute coronary artery events,301 perhaps in part because of increased myocardial vascularity. Other factors that might explain this finding, such as genetics, fitness, and diet, have not been adequately evaluated. The effect on the healthy heart of acute, transient exposure to high altitude also appears to be benign. Various avenues of research have indicated that the healthy heart tolerates even extreme hypoxia quite well, all the way to the summit of Mt. Everest (Pao2 less than 30 mm Hg). Numerous electrocardiograms (ECGs), echocardiograms, heart catheterizations, and exercise tests have failed to demonstrate any evidence of cardiac ischemia or cardiac dysfunction in healthy persons at high altitudes. This could partly result from the marked reduction in maximal exercise with increasing altitude, which reduces maximal heart rate and myocardial oxygen demand, and also from the increased coronary blood flow. A person with coronary artery disease (CAD), however, may not have the same adaptive capacities. For example, diseased coronary arteries might have limited ability to vasodilate and might actually constrict, because of unopposed sympathetic activation.261 What, then, are the risks, and what should be the advice to those with CAD considering a visit to high altitude? Surprisingly little literature is available to help the physician advise such persons. Does high altitude provoke acute coronary events or sudden death? In the United States, no evidence from state or county mortality statistics suggests an increased prevalence of acute coronary events in visitors to high-altitude locations. In Europe, Halhuber and colleagues reported an incidence of only 0.2% for myocardial infarction in 434 patients with CAD taken to altitudes between 1700 and 3200 m for 4 weeks in the Alps.166 He also reported a very low incidence of sudden death in 151,000 vacationers in the Alps, 69,000 of who were over age 40. In contrast are data from Austria claiming a higher rate of sudden cardiac death in the mountains, compared with the overall risk of sudden cardiac death.60 However, the altitudes were rather low (1000 to 2100 m), and no increased risk was evident in men who participated regularly in sports. The authors suggested that abrupt onset of exercise in sedentary men combined with altitude stress might induce cardiac sudden death, but whether altitude contributed at all is unclear.

In summary, limited data suggest no increased risk for sudden cardiac death or myocardial infarction at altitudes up to 2500 m. Another important question is whether altitude will exacerbate stable ischemia. The slight increase in heart rate and blood pressure on initial ascent to altitude might exacerbate angina in those with coronary artery disease, as described by Hultgren.202 One study evaluated nine men with stable exercise-induced angina by exercise treadmill test at 1600 m (Denver), and within the first hour of arrival at 3100 m.316 Cardiac work was slightly higher for a given workload at high altitude compared with low altitude, and as a result, the onset of angina was at a slightly lower workload. The authors found that a heart rate of 70% to 85% of the rate that produced ischemia at low altitude was associated with angina-free exercise at 3100 m, and they suggested that angina patients at altitude adjust their activity level on the basis of heart rate, at least on the day of arrival.316 Brammel and colleagues reported similar results and suggested that those with angina need to reduce their activity at high altitude to avoid angina episodes.56 In a more recent study, Levine and colleagues investigated 20 men who were much older than those in the previous investigations (mean age, 68 ± 3 years), and they performed symptom-limited exercise tests.261 With acute exposure to 2500 m, the double product (heart rate times systolic blood pressure) required to induce 1 mm ST depression was decreased about 5%, but after 5 days of acclimatization at 2500 m, this value was unchanged from sea level. The degree of ischemia (maximal ST-segment depression) was the same at sea level, with acute altitude exposure, and after 5 days at 2500 m. Also, no new wall motion abnormalities on echocardiography were seen at high altitude. Only one subject exhibited increased angina at altitude, and one person with severe coronary artery disease developed a myocardial infarction after maximal exercise at 2500 m. The authors concluded that patients with CAD who are well compensated at sea level do well at a moderate altitude after a few days of acclimatization, but that acutely, the angina threshold may be lower and activity should be reduced.261 Finally, a study of 97 older adults visiting 2500 m, many with CAD and abnormal ECGs, found no new ECG changes and no events suggestive of ischemia. In contrast to the Levine study, these subjects did not do exhaustive exercise tests but merely their usual activities, which included walking in the mountains.369 Taken altogether, these various investigations indicate that those with CAD, including older adults, generally do well at the modest altitude of 2500 m, but that reducing their activities the first few days at altitude is wise. To address the question of whether altitude might provoke cardiac arrhythmia, Levine and colleagues, in their study mentioned previously,261 found that premature ventricular contractions (PVCs) increased 63% on acute ascent but returned to baseline after 5 days of acclimatization. A simultaneous rise in urine norepinephrine in these subjects indicated that sympathetic activation was the cause of the increased ectopy. They observed no increase in higher-grade ectopy, however, and no changes in signal-averaged ECG suggestive of a change in fibrillation threshold; in other words, the PVCs appeared benign. Halhuber and coworkers also found increased ectopy in their subjects, and also no serious adverse events.166 In addition, Alexander described asymptomatic PVCs and ventricular bigeminy in himself while trekking to 5900 m. Subsequent evaluation found no evidence of heart disease, and the event prompted him to thoroughly review the subject of altitude, age,

Chapter 1: High-Altitude Medicine and arrhythmia.4 Although no dangerous arrhythmias have ever been reported in high-altitude studies, persons with troublesome or high-grade arrhythmia have not been evaluated on ascent to high altitude. The available evidence suggests that patients whose arrhythmias are well controlled on medication should continue the medication at altitude, whereas those with poorly controlled arrhythmias might do better to avoid visiting high altitude. In terms of advising persons with CAD or high likelihood of CAD about altitude exposure, the stress of high altitude on the coronary circulation appears to be minimal at rest but significant in conjunction with exercise. Ideally, no one with known CAD or even risk factors for CAD should undertake unaccustomed exercise at any altitude, and especially at high altitude. Therefore, advising an exercise program at sea level prior to exercising at altitude is prudent. The same technique of risk stratification that is commonly used at sea level can be applied for providing advice for high altitude.196 Using the standard recommendations, asymptomatic men over age 50 with no risk factors require no testing. For asymptomatic men over age 50 with risk factors, an exercise test is recommended to determine risk status prior to exercising at high altitude, and then further evaluation as indicated. Patients with previous myocardial infarction, bypass surgery, or angioplasty are considered at high risk only if they have a strongly positive exercise treadmill test. Patients with multiple-vessel bypass grafts who were asymptomatic, and who had normal exercise test results at sea level, have successfully visited altitudes over 5000 m. High-risk patients may require coronary angiography to establish appropriate management. Alexander has proposed different criteria for those with CAD at high risk at altitude: an ejection fraction less than 35% at rest, a fall in exercise systolic blood pressure, ST-segment depression greater than 2 mm at peak heart rate, and high-grade ventricular ectopy.3 For these persons, he recommends ascent to no more than 2500 m, and proximity to medical care. Both sets of recommendations, while reasonable, need to be validated with outcome studies.

Heart Failure Although information on the effect of high altitude on heart failure is scant, physicians in resort areas have noted a tendency toward acute decompensation within 24 hours of arrival in those with a history of heart failure. Those with CAD and low ejection fractions (less than 45%), but without active heart failure, actually did quite well, as gauged by exercise tests during acute exposure to 2500 m.112 Compared with 23 control subjects, the decrement in exercise performance was similar, and no complications or signs of ischemia developed. Although these results are encouraging for such patients, observations were not made past the first few hours at altitude. One concern is that those with heart failure might be more likely to retain fluid at altitude, especially if AMS were to develop, and that this could aggravate failure. Supporting this notion, Alexander found that ejection fraction declined at altitude during an exercise study in patients with angina, with an increase in enddiastolic and systolic volume as measured by two-dimensional echocardiogram.3 Ventricular contractility was not depressed, however, and these changes were attributed to fluid overload. Patients with heart failure need to be informed about possible consequences of high-altitude exposure. In particular, they need to avoid AMS (which is associated with fluid retention), continue their regular medications, and be prepared to increase

35

their diuretic should symptoms of failure exacerbate. Acetazolamide prophylaxis may be useful to consider for speeding acclimatization, inducing diuresis, and preventing AMS, but its efficacy in these patients remains untested.

Obesity The interaction of obesity and altitude has not received much attention. A small study suggested a slight increased susceptibility to AMS in mildly obese men,124 possibly due to lower nocturnal oxygen saturation that was present despite greater than normal hypoxic and hypercapnic chemosensitivity.125 Another, larger study examined men with metabolic syndrome (obesity, hypertension, diabetes, and hyperlipidemia) with a 3-week stay at 1700 m and found normal altitude responses and a loss of body fat.142 In fact, altitude has been suggested as a treatment for obesity. Obese men and women (mean body mass index, 47.1) who were permanent residents at a mean altitude of 2448 m, however, had a 96% incidence of systolic pulmonary artery hypertension (>30 mm Hg), which was related to alveolar hypoventilation.449

Sickle Cell Disease Sickle cell (SC) crisis is a well-recognized complication of highaltitude exposure.117 Even the modest altitude of a pressurized aircraft (1500 to 2000 m) causes 20% of persons with hemoglobin SC and sickle-thalassemia genetic configuration to have a vaso-occlusive crisis.278 High-altitude exposure may precipitate the first vaso-occlusive crisis in persons previously unaware of their condition. Persons with sickle cell anemia and a history of vaso-occlusive crises are advised to avoid altitudes over 1800 m unless they are taking supplemental oxygen. Persons with sickle cell disease who live at high altitude in Saudi Arabia have twice the incidence of crises, hospitalizations, and complications as do Saudis at low altitude. Splenic infarction syndrome has been reported more commonly in those with sickle cell trait than in those with sickle cell anemia, probably because sickle cell disease produces autosplenectomy early in life. Frequent reports in the literature emphasize the need to consider splenic syndrome caused by sickle cell trait in any person with left upper quadrant pain, even at an altitude of only 1500 m.247,278 A number of authors have suggested that nonblack persons with the trait may be at greater risk for splenic syndrome at high altitude than are black persons.247 Treatment of splenic syndrome consists of intravenous hydration, oxygen, and removal to a lower altitude.442 The overall incidence of problems in persons with the trait is low, however, and no special precaution other than recognition of the splenic syndrome is recommended. The U.S. Army, for example, does not consider soldiers with the trait unfit for duty at high altitude.100

Pregnancy In high-altitude natives, pregnancy-associated hypertension is 4 times more common than in low-altitude pregnancies, preeclampsia is more common, and full-term infants are small for gestational age.311,314 These problems raise the issue of whether short-term altitude exposure may also pose a risk. So far, there is no evidence that these problems, or others such as spontaneous abortion, abruptio placentae, or placenta previa, can result from a sojourn at high altitude.328 Unfortunately, however, few data exist on the influence of a high-altitude visit during pregnancy on the mother and the fetus. For moderate

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altitude, the research to date has been reassuring.193,194 Artal and colleagues studied seven sedentary women at 34 weeks gestation. Maximal and submaximal exercise tests were completed at sea level and 6000 feet (1830 m) after 2 to 4 days of acclimatization.11 They reported the expected decrease in maximal aerobic work but found no difference from sea level in fetal heart rate responses, or in maternal lactate, epinephrine, and norepinephrine levels. In a small number of subjects, the authors considered it safe for third-trimester women to engage in brief bouts of exercise at moderate altitude. A similar conclusion was reached in a study of 12 pregnant women who exercised after ascent to 2225 m. The authors found no abnormal fetal heart rate responses and considered the exercise at altitude benign for both mother and fetus.38 Huch also concluded that short-term exposure, with exercise, was safe during pregnancy.193 In summary, the available data, though limited, indicate that shortterm exposure to altitudes up to 2500 m, with exercise, is safe for a lowland woman with a normal pregnancy. Another avenue of research has been alteration of blood gases during pregnancy. Human and animal studies with acute hypoxic challenge, as well as oxygen-breathing studies, have drawn two conclusions: (1) that a compromised placental–fetal circulation could be unmasked at high altitude, and (2) that a fetus with a normal placental–fetal circulation seems to tolerate a level of acute hypoxia far exceeding a moderate altitude exposure.18,81,362 On the basis of the available research, it seems prudent to recommend that only women with normal, low risk pregnancy

2

undertake a sojourn at high altitude. For these women, exposure to an altitude at which Sao2 will remain above 85% most of the time (up to 3000 m altitude) appears to pose no risk of harm, but further study is needed to place these recommendations on a more solid scientific footing. An ultrasound or other assessment may be useful to rule out the more common complications prior to travel. Of course, it is not the altitude per se that determines whether the fetus becomes stressed but rather the maternal (and fetal) arterial oxygen transport. A woman with high-altitude pulmonary edema at 2500 m, for example, is much more hypoxemic than a healthy woman at 5000 m. Therefore, a strategy for preventing altitude illness, especially pulmonary edema, must be explained and implemented. Similarly, elevated carboxyhemoglobin from smoking, lung disease, and other problems of oxygen transport will render the pregnant patient at altitude more hypoxemic, and physiologically comparable to a higher altitude. Consideration of a high-altitude sojourn in the developing world, or in a wilderness setting, raises other issues that may be more important than the modest hypoxia. These include remoteness from medical care should a problem arise, quality of available medical care, use of medications for such important things as malaria and traveler’s diarrhea (many of which are contraindicated in pregnancy), and risks for trauma.

The references for this chapter can be found on the accompanying DVD-ROM.

Avalanches Knox Williams, Dale Atkins, and Colin K. Grissom

An avalanche is a mass of snow that slides down a mountainside. In the United States, approximately 100,000 avalanches occur annually, of which about 100 cause injury, death, or destruction of property. Based on a database of reported incidents, about 200 people a year are caught in avalanches (that is, they are bodily involved in the moving snow or its effects). Of these, 84 are partly or wholly buried, 30 sustain injury, and 30 are killed. Average annual property damage varies tremendously depending on the winter. In the last 10 years, damages have ranged from as low as $30,000 to a high of $13.5 million; the median is $298,000. This chapter describes the properties of the mountain snowpack that contribute to avalanche formation and describes avalanche safety techniques.


PROPERTIES OF SNOW Physical Properties Although snow cover appears to be nothing more than a thick, homogeneous blanket covering the ground, it is in fact one of the most complex materials found in nature. It is highly variable and goes through significant changes in relatively short periods. In nature, snow cover is variable on both the broad geographic scale (Antarctic snow is quite different from snow found in the Cascade Mountains of North America) and on the microscale (where snow conditions may vary greatly from one side of a rock or tree to the other). All snow crystals are made

Chapter 2: Avalanches of the same substance, the water molecule, but local environmental conditions control the type and character of snow found at a given location. At a single site, the snow cover varies from top to bottom, resulting in a complex, layered structure. Individual layers may be quite thick or very thin. In general, thicker layers represent consistent conditions during one storm, when new snow crystals falling are of the same type, wind speed and direction vary little, and temperature and precipitation are fairly constant. Thinner layers, perhaps only millimeters in thickness, often reflect conditions between storms, such as the formation during fair weather of a melt–freeze crust, a period of strong winds creating a wind crust, or the occurrence of surface hoar, the winter equivalent of dew. Delicate feathershaped crystals of surface hoar deposited from the moist atmosphere onto the cold snow surface overnight offer a beautiful glistening sight as they reflect the sun of the following day. However, they are very fragile and weak, and once buried by subsequent snowfalls, they may be major contributors to avalanche formation. One property of snow is strength, or hardness, which is of great importance in terms of avalanche formation. Snow can vary from light and fluffy, easy to shovel, and especially delightful to ski through, to heavy and dense, impossible to penetrate with a shovel, and hard enough to make it very difficult for a skier to carve a turn, even with sharp metal edges. The arrangement of the ice skeleton and the changing density (mass per unit volume) produce this wide range of conditions. In the case of snow, density is determined by the volume mixture of ice crystals and air. The denser the snow layer, the harder and stronger it becomes, as long as it is not melting. The density of new snow can have a wide range of values. This depends on how closely the new snow crystals pack together, which is controlled by the shape of the crystals. The initial crystals have a variety of shapes, and some pack more closely together than others (Fig. 2-1). For example, needles pack more closely than stellars and as a consequence may possess a density 3 to 4 times that of stellars. Wind can alter the shape of new snow crystals, breaking them into much smaller pieces that pack very closely together to form wind slabs. These in turn may possess a density 5 to 10 times that of new stellars falling in the absence of wind. Because these processes occur at different times and locations at the surface of the snow cover and are buried by subsequent snowfalls, a varied, nonhomogeneous layered structure results. Therefore, what may seem to the casual observer to be minor variations in atmospheric conditions can have an important influence on the properties of snow. After snow has been deposited on the ground, the density increases as the snow layer settles vertically or shrinks in thickness. Because an increase in density equals an increase in strength, the rate at which this change occurs is important with respect to avalanche potential. Snow can settle simply because of its own weight. It is highly compressible because it is composed mostly of empty air pockets within an ice skeleton of snow crystals. In a typical layer of new snow, 85% to 95% of the volume is empty air pockets. Individual ice crystals can move and slide past each other, and because the force of gravity causes them to move slowly downward, the layer shrinks. The heavier the snow above is and the warmer the temperature, the faster this settlement proceeds. At the same time, the complex, intricate shapes that characterize the new snow crystals begin to change. They become

37

Figure 2-1. International classification of solid precipitation. (From the International Association of Scientific Hydrology, with permission.)

rounded and suitable for closer packing. Intricate crystals change because they possess a shape that is naturally unstable. New snow crystals have a large surface area-to-volume ratio and are composed of crystalline solid close to its melting point. In this aspect, snow crystals are almost unique among materials found in nature. Surface energy physics dictates that this unstable condition will change; the warmer the temperature is, the faster the change. Under very cold conditions, the original shapes of the snow crystals are recognizable after they have been in the snow cover for several days or even a week or two. As temperatures warm and approach the melting point, such shapes disappear within a few hours to a day. Changes in the shape or texture of snow crystals are examples of initial metamorphism. The geologic term metamorphism defines changes that result from the effects of temperature and pressure. As the crystal shapes simplify, they can pack more closely together, enhancing further settlement (Fig. 2-2). The changes generally occur within hours to a few days. The structure of snow cover changes over a period of weeks to months via other processes. Settlement, which may initially have been rapid, continues at a much slower rate. Other factors begin to exert dominant influences on metamorphism. These factors include the difference in temperature measured upward or downward in the snow layer, called the temperature gradient.

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Kinetic metamorphism

Ice grain

Densification and strengthening of snowpack

Figure 2-2. Settlement. As the crystal shapes become more rounded, the crystals can pack more closely together, and the layer settles or shrinks in thickness.

Water vapor Ice grain

Low temperature

Heat flow High temperature

Temperature gradient Temperature °C 0° –5° –10° 150

Energy exchange with atmosphere

Figure 2-4. In the temperature gradient process, ice sublimates from the top of one grain, moves upward as water vapor, and then is deposited on the bottom surface of the grain above. If conditions allow this process to continue long enough, all of the original grains are lost as the recrystallization produces a layer of new crystals.

100 Snow height cm 50

Temperature profile

0 Heat supply from earth

Figure 2-3. When an insulating layer of snow separates the warm ground from the cold air, a temperature gradient develops across the snow layer.

Averaged over 24 hours, snow temperatures generally are coldest near the surface and warmest near the ground at the base of the snow cover, creating a temperature gradient across a snow layer sandwiched between cold winter air and relatively warm ground (Fig. 2-3). The temperature gradient crosses both ice and large void spaces filled with air. Within the ice skeleton, the temperature adjacent to the ground is warmer than that of the snow layer just above, and this pattern continues through the snow cover in the direction of the colder surface. Warm air contains more water vapor than cold air; this holds true for the air trapped within the snow cover. The greater the amount of water vapor, the greater the pressure. Therefore, both a pressure gradient and a temperature gradient exist through the snow cover. When a pressure difference exists, the difference naturally tends to equalize, just as adjacent high and low atmospheric pressure centers cause movement of air masses. Pressure differences within snow cause vapor to move upward through the snow layers. The air within the layers of the snow cover is saturated with water vapor, with a relative humidity of 100%. When air moves upward to a colder layer, the amount of water vapor that can be supported in the air pocket diminishes. Some vapor changes to ice and is deposited on the surrounding ice grains. We witness a similar process when warm, moist air in a heated room comes in contact with a cold win-

dowpane. The invisible water vapor is cooled to its ice point, and some of the vapor changes state and is deposited as frost on the window. Figure 2-4 shows how the texture of the snow layer changes during this temperature-gradient process. Water molecules sublimate from the upper surfaces of a grain. The vapor moves upward along the temperature (and vapor) gradient and is deposited as a solid ice molecule on the underside of a colder grain above. If this process continues long enough (it continues as long as a strong temperature gradient exists), all grains in the snow layer are transformed from solid to vapor and back to solid again; that is, they recrystallize. New crystals are completely different in texture from their initial form. They become large, coarse grains with facets and sharp angles and may eventually evolve into a hollow cup form. Examples of these crystals are shown in Figure 2-5. The process is called temperature-gradient metamorphism, or kinetic metamorphism, and well-developed crystals are commonly known as depth hoar. Depth hoar is of particular importance to avalanche formation. It is very weak because there is little or no cohesion or bonding at the grain contacts. Depth hoar or temperaturegradient snow layers can be compared to dry sand. Each grain may possess significant strength, but a layer composed of grains is very weak and friable because the grains lack connections. Thus depth hoar is commonly called “sugar snow.” Depth hoar usually develops whenever the temperature gradient is equal to or greater than about 10º C (18° F) per meter. In the cold, shallow snow covers of a continental climate, such as that of the Rocky Mountains, a gradient of this magnitude is common within the first snow layers of the season. Therefore, a layer of depth hoar is frequently found at the bottom of the snow cover, and the resulting low strength becomes a significant factor for future avalanches. In the absence of a strong temperature gradient, a totally different type of snow texture develops. When the gradient is less

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Equilibrium metamorphism Convex high vapor pressure H2O transfer

H2O transfer

Concave low vapor pressure

A Figure 2-6. In the equilibrium metamorphism process, ice molecules sublimate from crystal points (convexities) and redeposit on flat or concave areas of the crystal.

Equilibrium metamorphism

B Figure 2-5. A, Mature depth hoar grains. Facets and angles are visible. Grain size, 3 to 5 mm. B, Advanced temperature-gradient grains attain a hollow cup-shaped form. Size, 4 mm. (Polarized-light photos by Doug Driskell.)

Sharp concave regions

Necks form—sintering

Figure 2-7. Equitemperature grain growth. In the presence of weak temperature gradients, bonds grow at the grain contacts.

than about 10º C (18° F) per meter, there is still a vapor pressure difference, but upward movement of vapor through the snow layers is at a much slower rate. As a result, water vapor deposited on a colder grain tends to cover the total grain in a more homogeneous manner, rather than showing the preferential deposition characteristic of depth hoar. This process produces a grain with a smooth surface of more rounded or oblong shape. Over time, vapor is deposited at the grain contacts (concavities), as well as over the remaining surface of the grain (convexity) (Fig. 2-6). Connecting bonds formed at the grain contacts give the snow layer strength over time (Fig. 2-7). Bond growth, called sintering, yields a cohesive texture, in complete contrast to the cohesionless texture of depth hoar. This type of grain has been referred to by various terms (destructive metamorphism, equitemperature metamorphism, and equilibrium metamorphism) but can generally be described as fine-grained or well-sintered (bonded) snow. Bonded and interconnected grains are shown in Figure 2-8. The preceding paragraphs describe the big picture in terms of what happens to snow layers after they have been buried by

Figure 2-8. Bonded or sintered grains resulting from equitemperature metamorphism. Grain size, 0.5 to 1 mm. (Polarized-light photo by Doug Driskell.)

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subsequent snowfalls. If the layer is subfreezing (i.e., if no melt is taking place), one of the two processes described previously is occurring, or perhaps a transition exists between the two. Within the total snow cover, these processes may occur simultaneously, but only one can take place within a given layer at a given time. Both processes accelerate with warmer snow temperature because more water vapor is involved. The temperature gradient across the layer determines whether the process involves the growth of weak depth hoar crystals or the development of a stronger snow layer with a sintered, interconnected texture.

Slab Avalanche Formation There are two basic types of avalanche release. The first is a point-release, or loose snow, avalanche (Fig. 2-9). A loose snow avalanche involves cohesionless snow and is initiated at a point, spreading out laterally as it moves down the slope to form a characteristic inverted V shape. A single grain or a clump of grains slips out of place and dislodges those below on the slope, which in turn dislodge others. The avalanche continues as long as the snow is cohesionless and the slope is steep enough. This type of avalanche usually involves only small amounts of nearsurface snow. The second type of avalanche, the slab avalanche, requires a cohesive snow layer poorly anchored to the snow below because of the presence of a weak layer. The cohesive blanket of snow breaks away simultaneously over a broad area (Fig. 2-10). A slab release can involve a range of snow thicknesses, from the near-surface layers to the entire snow cover down to the ground. In contrast to a loose snow avalanche, a slab avalanche has the potential to involve very large amounts of snow. To understand the conditions in snow cover that contribute to slab avalanche formation, it is essential to reemphasize that snow cover develops layer by layer. Although a layered structure can develop by metamorphic processes, distinct layers develop in numerous other ways, most of which have some influence on avalanche formation. The layered structure is directly tied to the two ingredients essential to the formation of slab avalanches: the cohesive layer of snow and the weak layer beneath. If the snow cover is homogeneous from the ground to the surface, there is no danger of slab avalanches, regardless of the snow type. If the entire snow layer is sintered, dense, and strong, stability is very high. Even if the entire snow cover is composed of a very weak layer of depth hoar, there is still no hazard from slab avalanches because the cohesionless character does not allow propagation of the cracks necessary for slab avalanches to form. However, the combination of a basal layer of depth hoar with a cohesive layer above, for example, provides exactly the ingredients for slab avalanche danger. For successful evaluation of slab avalanche potential, information is needed about the entire snowpack, not just the surface. A hard wind slab at the surface may seem strong and safe to the uninitiated, but when it rests on a weaker layer, which may be well below the surface, it may fail under the weight of a skier and be released as a slab avalanche. Many snow structure combinations can contribute to slab formation. One scenario involves thick layers of weak snow, which result from the development of depth hoar early in the season. The typical combination of climatic factors that produce these layers is early winter snowfalls followed by several weeks of clear, cold weather. Even at higher elevations in the moun-

Figure 2-9. Loose snow or point-release avalanche. (Photo courtesy USDA Forest Service.)

tains, snow cover on the slopes with a southerly aspect may melt off during a period of fair weather. However, in October and early November, the sun angle is low enough that steep slopes with a northerly aspect receive little or no direct heating from the sun. Snow remains on the ground but not without change. Snow on north-facing slopes experiences optimal conditions for depth hoar formation: a thin, low-density snow cover (maximum opportunity for vapor flow) is sandwiched between

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Figure 2-10. Slab avalanche. (From USDA Forest Service:Williams K, Armstrong B:The Snowy Torrents. Jackson,WY,Teton Bookshop, 1984, with permission. Photo by Alexis Kelner.)

Figure 2-11. Snow layer combinations that often contribute to avalanche formation.

the warm ground, still retaining much of its summer heat, and the cold air above. This snow layer recrystallizes over a period of weeks. When the first large storm of winter arrives in November, cohesive layers of wind-deposited snow accumulate on a very weak base, setting the scene for a widespread avalanche cycle. Figure 2-11 describes other combinations that result in brittle or cohesive layers of snow on a weak layer.

Mechanical Properties: How Snow Deforms on a Slope Almost all physical properties of snow can be easily seen or measured. A snowpit provides a wealth of information regarding these properties, layer by layer, throughout the thickness of the snow cover. However, even detailed knowledge of these

properties does not provide all the information necessary to evaluate avalanche potential. The current mechanical state of the snow cover must be considered. Unfortunately, for the average person these properties are virtually impossible to measure directly. Mechanical deformation occurs within the snow cover just before its failure and the start of a slab avalanche. Snow cover has a tendency to settle simply from its own weight. When this occurs on level ground, the settlement is perpendicular to the ground and the snow layer increases in density and gains in strength. The situation is not so simple when snow rests on a slope. The force of gravity is divided into two components, one

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Figure 2-12. Depending on prevailing conditions, snow may deform and stretch in a viscous or flowing manner, or it may respond more like a solid, and fracture.

tending to cause the snow layer to shrink in thickness, and a new component acting parallel to the slope, which tends to pull the snow down the slope. Down-slope movement within the snow cover occurs at all times, even on gentle slopes. The speed of movement is slow, generally on the order of a few millimeters per day up to millimeters per hour within new snow on steep slopes. The evidence of these forces is often clearly visible in the bending of trees and damage to structures built on snow-covered slopes. Although the movement is slow, when deep snow pushes against a rigid structure, the forces are significant, and even large buildings can be pushed off their foundations. Snow deforms in a highly variable fashion. It is generally described as a viscoelastic material. Sometimes it deforms as if it were a liquid (viscous) and at other times it responds more like a solid (elastic). Viscous deformation implies continuous and irreversible flow. Elastic deformation implies that once the force causing the deformation is removed, some small part of the initial deformation is recovered. The elasticity of snow is not so obvious, primarily because the amount of rebound is very small compared with that of more familiar materials. In regard to avalanche formation, it is important to know when snow acts primarily as an elastic material and when it responds more like a viscous substance. These conditions are shown in Figure 2-12. Laboratory experiments have shown that conditions of warm temperatures and slow application of force favor viscous deformation. We see examples of this as snow slowly deforms and bends over the edge of a roof or sags from a tree branch. In such cases, the snow deforms but does not crack or break. In contrast, when temperatures are very cold or when force is applied rapidly, snow reacts like an elastic material. If enough force is applied, it fractures. We think of such a substance as brittle; the release of stored elastic energy causes fractures to move through the material. In the case of snow cover on a steep slope, forces associated with accumulating snow or the weight of a skier may increase until the snow fails. At that point, stored elastic energy is released and is available to drive brittle fractures over great distances through the snow slab.

Figure 2-13. The consistent 90-degree angle between crown face and bed surface of the avalanche shows that slab avalanches result from an elastic fracture. (Photo by A. Judson.)

The slab avalanche provides the best example of elastic deformation in snow cover. Although the deformation cannot actually be seen, evidence of the resultant brittle failure is clearly present in the form of the sharp, linear fracture line and crown face of the slab release (Fig. 2-13). The crown face is almost always perpendicular to the bed surface, evidence that snow has failed in a brittle manner. To fully understand the slab avalanche condition or the stability of the snow cover, its mechanical state must be considered. Snow is always deforming down-slope, but throughout most of the winter the strength of the snow is sufficient to prevent an avalanche. The snow cover is layered, and some layers are weaker than others. During periods of snowfall, blowing snow, or both, an additional load, or weight, is being applied to the snow in the starting zone, the snow is creeping faster, and these new stresses are beginning to approach the strength of the weakest layers. The weakest layer has a weakest point somewhere within its continuous structure. If the stresses caused by the load of the new snow or the weight of a skier reach the level at which they equal the strength of the weakest point, the snow fails completely at that point (Fig. 2-14). This means that the strength at that point immediately goes to zero. This is analogous to what would happen if someone on a tugof-war team were to let go of the rope. If the remainder of the team was strong enough to make up for the lost member, not much would change immediately. The same situation exists with the snow cover. If the surrounding snow has sufficient strength to make up for the fact that the strength at the weakest point has now gone to zero, nothing happens beyond perhaps a local movement or settlement in the snow. If, however, the surrounding snow is not capable of doing this, the area of snow next to the initial weak point fails, and then the area next to it, and the chain reaction begins. As the initial crack forms in the now unstable snow, the elastic energy is released, which in turn drives the crack further, releasing more elastic energy, and so forth. The ability of snow to store elastic energy is essentially what allows large slab avalanches to occur. As long as the snow properties are similar across the avalanche starting zone, the crack will continue to

A

B Figure 2-14. Slab avalanche released by a skier. (Photo by R. Ludwig.)

C

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propagate, allowing entire basins, many acres in area, to be set in motion within a few seconds.


AVALANCHE DYNAMICS The topic of avalanche dynamics includes how avalanches move, how fast they move, and how far and with how much destructive power they travel. The science of avalanche dynamics is not well advanced, although much has been learned in the past few decades. Measured data for avalanche velocity and impact pressure are still lacking. Although any environmental measurement presents its own set of problems, it is clear that opportunities for making measurements inside a moving avalanche are extremely limited. Although avalanche paths exist in a variety of sizes and shapes, they all have three distinct parts

with respect to dynamics (Fig. 2-15). In the starting zone, usually the steepest part of the path, the avalanche breaks away, accelerates down the slope, and picks up additional snow. From the starting zone, the avalanche proceeds to the track, where it remains essentially constant and picks up little or no additional snow as it moves; the average slope angle has become less steep and frequently the snow cover is more stable than in the starting zone. (However, a study by Sovilla and colleagues19a from Switzerland in 2000 showed that a significant amount of snow could be entrained into the avalanche from the track.) Small avalanches often stop in the track. After traveling down the track, the avalanche reaches the runout zone. Here the avalanche motion ends, either slowly as it decelerates across a gradual slope, such as an alluvial fan, or abruptly as it crashes into the bottom of a gorge or ravine. As a general rule, the slope angle of starting zones is 30 to 45 degrees, of the track it

Starting zone

Track

Runout zone

Figure 2-15. The three parts of an avalanche path: starting zone, track, and runout zone. (Photo by B. Armstrong.)

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is 20 to 30 degrees, and of the runout zone it is less than 20 degrees. Few actual measurements of avalanche velocities have been made, but enough data have been obtained to provide some typical values for the various avalanche types. For the highly turbulent dry-powder avalanches, the velocities are commonly in the range of 75 to 100 mph (34 to 45 m/s), with rare examples in the range of 150 to 200 mph (67 to 89 m/s). Such speeds are possible for powder avalanches because large amounts of air in the moving snow greatly reduce the forces resulting from internal friction. As snow in the starting zone becomes dense, wetter, or both, movement becomes less turbulent and a more flowing type of motion reduces typical velocities to the range of 50 to 75 mph (22 to 34 m/s). During spring conditions when the snow contains large amounts of liquid water, speeds may reach only about 25 mph (11 m/s) (Fig. 2-16). In most cases, the avalanche simply follows a path down the steepest route on the slope while being guided or channeled by terrain features. However, the higher-speed avalanche may deviate from this path. Terrain features, such as the side walls of a gully, which would normally direct the flow of the avalanche around a bend, may be overridden by a high-velocity powder avalanche (Fig. 2-17). The slower-moving avalanches, which travel near the ground, tend to follow terrain features, giving them somewhat predictable courses. Because avalanches can travel at very high speeds, the resultant impact pressures can be significant. Smaller and mediumsize events (impact pressures of 1 to 15 kilopascals [kPa]) have the potential to heavily damage wood-frame structures. Extremely large avalanches (impact pressures of more than 150 kPa) possess the force to uproot mature forests and even destroy structures built of concrete. Some reports of avalanche damage describe circumstances that cannot be easily explained simply by the impact of large amounts of fast-moving dense snow. Some observers have noted that as an avalanche passed, some buildings actually exploded, perhaps from some form of vacuum created by the fast-moving snow. Other reports indicate that a structure was destroyed by the “air blast” preceding the avalanche because there was no evidence of large amounts of avalanche debris in the area. However, this is more likely to be damage resulting from the powder cloud, which may be composed of only a few inches of settled snow yet it contributes significantly to the total impact force. The presence of snow crystals can increase the air density by a factor of 3 or more. A powder cloud traveling at a moderate dry-avalanche speed of 60 mph (27 m/s) could have the impact force of a 180-mph (80 m/s) wind, well beyond the destructive capacity of a hurricane.


IDENTIFYING AVALANCHE PATH CHARACTERISTICS

Characteristics such as elevation, slope profiles, and weather determine whether a mountain can produce avalanches. The ingredients of an avalanche, snow and a steep-enough slope, are such that any mountain can produce an avalanche if conditions are exactly right. To be a consistent producer of avalanches, a mountain and its weather must work in harmony.

Elevation Mountains must be at high-enough latitudes or must be high enough in elevation to build and sustain a winter snow cover

Figure 2-16. A dry-snow avalanche may have a slowing motion and travel near the surface or, with lower density snow and higher velocities,the turbulent dust cloud of the powder avalanche develops.

before their slopes can become avalanche threats. Temperature drops steadily with elevation. This has the obvious effect of allowing snow to build up deeper and remain longer at higher elevations before melting depletes the snow cover. A less obvious effect of the temperature and elevation relationship on avalanche formation is the demarcation called the treeline.

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PART ONE: MOUNTAIN MEDICINE only 10 degrees, but the avalanche was big enough to kill seven skiers. This extreme applies only to a water-saturated snowpack, which behaves more like a liquid than a solid. A more realistic slope is 22 degrees, the “angle of repose” for granular substances, such as sand and dry, unbonded snow. Round grains will not stack up in a pile having sides much steeper than 22 degrees before gravity rearranges the pile. Drysnow avalanches have occurred on slopes of 22 to 25 degrees; these are rare because snow grains are seldom round and seldom touch without forming bonds. A useful minimum steepness for producing avalanches is 30 degrees. Avalanches occur with the greatest frequency on slopes of 30 to 45 degrees. These are the angles in which the balance between strength (the bonding of the snow trying to hold it in place) and stress (the force of gravity trying to pull it loose) is most critical. On even steeper slopes, the force of gravity wins; snow continually rolls or sloughs off, preventing buildup of deep snowpacks. Exceptions exist, such as damp snow plastered to a steep slope by strong winds.

Orientation

Figure 2-17. The large powder cloud associated with a fast-moving dry-snow avalanche. (Photo by R. Armstrong.)

This is the level above which the combined effects of low temperature, strong winds, and heavy snowfall prevent tree growth. The treeline can be quite variable in any mountain range, depending on the microclimates. On a single mountain, treeline is generally higher on south slopes than on north slopes (in the northern hemisphere), because more sunshine leads to warmer average temperatures on southern exposures. Latitudinal variation in the elevation of treeline ranges from sea level in northern Alaska to almost 3658 m (12,000 feet) in the Sierras of southern California and the Rockies of New Mexico. Mountains that rise above treeline are more likely to produce avalanches. Dense timber anchors the snowpack, so avalanches can seldom start. Below treeline, avalanches can start on slopes having no trees or only scattered trees, a circumstance arising either from natural conditions, such as a streambed or rockslide area, or from human-made conditions, such as clearcuts. Above treeline, avalanches are free to start, and once set in motion, they can easily cut a swath through the trees below. The classic avalanche path is one having a steep bowl above treeline to catch the snow and a track extending below treeline. Avalanches run repeatedly down the track and ravage whatever vegetation grows there, leaving a scar of small or stunted trees that cuts through larger trees on either side.

Slope Angle In snow that is thoroughly saturated with water, so that a slush mixture is formed, the slope needs only to have a slight tilt to produce an avalanche. For example, a wet-snow avalanche in Japan occurred on a beginner slope at a ski area. The slope was

Avalanches occur on slopes facing every point of the compass. Steep slopes are equally likely to face east or west, north or south. There are factors, however, that cause more avalanches to fall on slopes facing north, northeast, and east than on those facing south through west. These relate to slope orientation with respect to sun and wind. The sun angle in northern hemisphere winters causes south slopes to get much more sunshine and heating than north slopes, which frequently leads to radically different snow covers. North slopes have deeper and colder snow covers, often with a substantial layer of depth hoar near the ground. South slopes usually carry a shallower and warmer snow cover, laced with multiple ice layers formed on warm days between storms. Most ski areas are built on predominantly north-facing slopes to take advantage of deeper and longerlasting snow cover. At high latitudes, such as in Alaska, the winter sun is so low on the horizon and heat input to south slopes is so small that there are few differences in the snow covers of north and south slopes. The effect of the prevailing west wind at midlatitudes is important. Storms most often move west to east, and storm winds are most frequently from the western quadrant: southwest, west, or northwest. The effect is to pick up fallen snow and redeposit it on slopes facing away from the wind—that is, onto northeast, east, and southeast slopes. These are the slopes most often overburdened with wind-drifted snow. The net effect of sun and wind is to cause more avalanches on north- through east-facing slopes.

Avalanche Terrain The frequency with which a path produces avalanches depends on a number of factors, with slope steepness a major one. The easiest way to create high stress is to increase the slope angle; gravity works that much harder to stretch the snow out and rip it from its underpinnings. A slope of 45 degrees produces many more avalanches than one of 30 degrees. However, specific terrain features are also important. Broad slopes that are curved into a bowl shape and narrow slopes that are confined to a gully efficiently collect snow. Those having a curved horizontal profile, such as a bowl or gully, trap blowing snow coming from several directions; the snow drifts over the top and settles as a deep pillow. On the other hand,

Chapter 2: Avalanches the plane-surfaced slope collects snow efficiently only if it is being blown directly from behind. A side wind scours the slope more than loads it. The surface conditions of a starting zone often dictate the size and type of avalanche. A particularly rough ground surface, such as a boulder field, does not usually produce avalanches early in the winter, as it takes considerable snowfall to cover the ground anchors. Once most of the rocks are covered, avalanches pull out in sections, the area between two exposed rocks running one time, and the area between two other rocks running another. A smooth rock face or grassy slope provides a surface that is too slick for snow to grip. Therefore, full-depth avalanches are distinctly possible; if the avalanche does not run during the winter, it is likely to run to ground in the spring, once melt water percolates through the snow and lubricates the ground surface. Vegetation has a mixed effect on avalanche releases. Bushes provide anchoring support until they become totally covered; at that point they may provide weak points in the snow cover, because air circulates well around the bush, providing an ideal habitat for the growth of depth hoar. It is common to see that the fracture line of an avalanche has run from a rock to a tree to a bush, all places of healthy depth hoar growth. A dense stand of trees can easily provide enough anchors to prevent avalanches. Reforestation of slopes devoid of trees because of logging, fire, or avalanche is an effective means of avalanche control. Scattered trees on a gladed slope offer little if any support to hold snow in place. Isolated trees may do more harm than good by providing concentrated weak points on the slope.


FACTORS CONTRIBUTING TO AVALANCHE FORMATION

The factors that contribute to avalanche release are terrain, weather, and snowpack. Terrain factors are fixed; however, the states of the weather and of the snowpack change daily, even hourly. Precipitation, wind, temperature, snow depth, snow surface, weak layers, and settlement are all factors determining whether an avalanche will occur.

Snowfall New snowfall is the event that leads to most avalanches: more than 80% of all avalanches fall during or just after a storm. Fresh snowfall adds weight to existing snow cover. If the snow cover is not strong enough to absorb this extra weight, avalanche releases occur. The size of the avalanche is usually related to the amount of new snow. Snowfalls of less than 6 inches (15 cm) seldom produce avalanches. Snows of 6 to 12 inches (15 to 30 cm) usually produce a few small slides, and some of these harm skiers who release them. Snows of 1 to 2 feet (30 to 60 cm) produce avalanches of larger size that present a considerable threat to skiers and pose closure problems for highways and railways. Snows of 2 to 4 feet (60 to 120 cm) are much more dangerous, and snowfalls greater than 4 feet produce major avalanches capable of large-scale destruction. These figures are guidelines based on data and experience and must be considered with other factors to arrive at the true hazard. For example, a snowfall of 10 inches (25 cm) whipped by strong winds may be serious; a fall of 2 feet of feather-light snow in the absence of wind may produce no avalanches.

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Snowfall Intensity The rate at which snowfall accumulates is almost as important as the amount of snow. A snowfall of 3 feet (90 cm) in 1 day is far more hazardous than 3 feet in 3 days. As a viscoelastic material, snow can absorb slow loading by deforming or compressing. Under a rapid load, the snow cannot deform quickly enough and is more likely to crack, which is how slab avalanches begin. A snowfall rate of 1 inch per hour or greater sustained for 10 hours or more is generally a red flag indicating danger. The danger worsens if snowfall is accompanied by wind.

Rain Light rain falling on a cold snowpack invariably freezes into an ice crust, which adds strength to the snow cover. At a later time, the smooth crust could become a sliding layer beneath the new fall of snow. Heavy rain (usually an inch or more) greatly weakens the snow cover. First, it adds weight. An inch of rain is the equivalent in weight to 10 to 12 inches (25 to 30 cm) of snow. Second, it adds no internal strength of its own (in the form of a skeleton of ice, as new snow would), while it dissolves bonds between snow grains as it percolates through the top snow layers, reducing strength even further.

New Snow Density and Crystal Type A layer of fresh snow contains only a small amount of solid material (ice); the large majority of the volume is occupied by air. It is convenient to refer to snow density as a percentage of the volume occupied by ice. New snow densities usually range from 7% to 12%. In the high elevations of Colorado, 7% is an average value; in the more maritime climates of the Sierras and Cascades, 12% is a typical value. Density becomes an important factor in avalanche formation when it varies from average values. Wet snowfalls or falls of heavily rimed crystals, such as graupel, may have densities of 20% or greater. (Graupel is a snowflake that has been transformed into a pellet of soft ice because of riming inside a cloud.) A layer of heavier-thannormal snow presents a danger because of excess weight. Snowfall that is much lighter than normal, 2% to 4% for example, can also present a dangerous situation. If the low-density layer quickly becomes buried by snowfall of normal or high density, a weak layer has been introduced into the snowpack. By virtue of low density, the weak layer has marginal ability to withstand the weight of layers above, making it susceptible to collapse. Storms that begin with low temperatures but then warm up produce a layer of weak snow beneath a stronger, heavier layer. Density is closely linked to crystal type. Snowfalls consisting of graupel, fine needles, and columns can accumulate at high densities. Snowfalls of plates, stellars, and dendritic forms account for most of the lower densities.

Wind Speed and Direction Wind drives fallen snow into drifts and cornices from which avalanches begin. Winds pick up snow from exposed, windward slopes and drive it onto adjacent, leeward slopes, where it is deposited into sheltered hollows and gullies. A speed of 15 mph (7 m/s) is sufficient to pick up freshly fallen snow. Higher speeds are required to dislodge older snow. Speeds of 20 to 50 mph (9 to 22 m/s) are the most efficient in transporting snow into avalanche starting zones. Speeds greater than 50 mph can create spectacular banners of snow streaming from high peaks, but much of this snow is lost to evaporation in the

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air or is deposited far down the slope away from the avalanche starting zone. Winds play a dual role in increasing avalanche potential. First, wind scours snow from a large area (of a windward slope) and deposits it in a smaller area (of a starting zone). Wind can thus turn a 1-foot snowfall into a 3-foot drift in a starting zone. The rate at which blowing snow collects in bowls and gullies can be impressive. In one test at Berthoud Pass, Colorado, the wind deposited snow in a gully at a rate of 18 inches (45 cm) per hour. Another wind effect is that blowing snow is denser after deposit than before. This is because snow grains are subjected to harsh treatment in their travels; each collision with another grain knocks off arms and sharp angles, reducing size and allowing the pieces to settle into a denser layer. The net result of wind is to fill avalanche starting zones with more and heavier snow than if the wind had not blown.

Temperature The role of temperature in snow metamorphism is played over a period of days, weeks, and even months. The influence of temperature on the mechanical state of the snow cover is more acute, with changes occurring in minutes to hours. The actual effect of temperature is not always easy to interpret: whereas an increase in temperature may contribute to stabilization of the snow cover in one situation, it might at another time lead to avalanche activity. In several situations, an increase in temperature clearly produces an increase in avalanche potential. In general, these include a rise in temperature during a storm or immediately after a storm, or a prolonged period of warm, fair weather such as occurs with spring conditions. In the first example, the temperature at the beginning of a snowfall may be well below freezing, but as the storm progresses, the temperature increases. As a result, the initial layers of new snow are light, fluffy, low density, and relatively low in strength, whereas the later layers are warmer, denser, and stiffer. Thus, the essential ingredients for a slab avalanche are provided within the new snow layers of the storm: a cohesive slab resting on a weak layer. If the temperature continues to rise, the falling snow turns to rain, a situation not uncommon in lower-elevation, coastal mountain ranges. Once this happens, avalanches are almost certain because as the rain falls, additional weight is added to the avalanche slope, but no additional strength is provided as it is whenever a layer of snow accumulates. The second example may occur after an overnight snowstorm that does not produce an avalanche on the slope of interest. By morning, the precipitation stops and clear skies allow the morning sun to shine directly on the slopes. The sun rapidly warms the cold, low-density new snow, which begins to deform and creep down-slope. The new snow layer settles, becomes denser, and gains strength. At the same time, it is stretched downhill and some of the bonds between the grains are pulled apart; thus, the snow layer becomes weaker. If more bonds are broken by stretching than are formed by settlement, there is not enough strength to hold the snow on the slope and an avalanche occurs. In these first two examples, the complete snow cover generally remains at temperatures below freezing. A third example occurs when a substantial amount of the winter’s snow cover is warmed to the melting point. During winter, sun angles are low, days are short, and air temperatures are cold enough that the small amount of heat gained by the snow cover during the

day is lost during the long cold night. As spring approaches, this pattern changes, and eventually enough heat is available at the snow surface during the day to cause some melt. This melt layer refreezes again that night, but the next day more heat may be available, so that eventually a substantial amount of melting occurs and melt water begins to move down through the snow cover. As melt water percolates slowly downward, it melts the bonds that attach the snow grains, and the strength of the layers decreases. At first the near-surface layers are affected, with the midday melt reaching only as far as the uppermost few inches, with little or no increase in avalanche hazard. If warm weather continues, the melt layer becomes thicker and the potential for wet snow avalanches increases. The conditions most favorable for wet slab avalanches occur when the snow structure provides the necessary layering. When melt water encounters an ice layer or impermeable crust, or in some cases a layer of weak depth hoar, wet slab avalanches are likely to occur.

Depth of Snow Cover Of the snowpack factors contributing to avalanche formation, depth of snow cover is the most basic. When the early-winter snowpack covers natural anchors, such as rocks and bushes, the start of the avalanche season is at hand. North-facing slopes are usually covered before other slopes. A scan of the terrain usually suffices to weigh this clue, but another method can be used to determine the time of the first significant avalanches. Long-term studies show a relationship between snow depth at a study site and avalanche activity. For example, along Red Mountain Pass, Colorado, it is unlikely that an avalanche large enough to reach the highway will run until close to 3 feet (90 cm) of snow covers the ground at the University of Colorado’s snow study site. At Alta, Utah, once 52 inches (130 cm) of snowpack has built up, the first avalanche to cover the road leading from Salt Lake City can be expected.

Nature of the Snow Surface How well new snow bonds to the old snow surface is a key factor in determining whether an avalanche will release within the layer of new snow or deeper in the snowpack. A poor bond, usually new snow resting on a smooth, cold surface with snowfalls of 1 foot (30 cm) or more, almost always produces a new-snow avalanche. A strong bond, usually onto a warm, soft, or rough surface, may produce nothing at all, or if weaknesses lie at deeper layers of the snow cover, a large snowfall will cause avalanches to pull out older layers of snow in addition to the new snow layer. These avalanches have more potential for destruction. A cold, hard snow surface offers little grip to fresh, cold snow. Ice crusts are commonly observed to be avalanche-sliding surfaces. The crust could be a sun crust, a rain crust, or a hardened layer of firm snow that has survived the summer. Firm layers are especially dangerous in early winter when first snows fall.

Weak Layers Any layer susceptible to collapse or failure because of the weight of the overburden is a weak link. Of the snowpack contributory factors, this is the most important, because a weak layer is essential to every avalanche. The weak layer releases along what is called the failure plane, sliding surface, or bed surface. One common weak layer is an old snow surface that offers a poor bond for new snow. Another weak layer that forms on

Chapter 2: Avalanches the snow surface is hoar frost, or surface hoar (see Physical Properties, earlier). On clear, calm nights, it forms a layer of feathery, sparkling flakes that grow on the snow surface. The layer can be a major contributor to avalanche formation when buried by a snowfall. Many avalanches have been known to release on a buried layer of surface hoar, sometimes a layer more than 1 month old and 6 feet (180 cm) or more below the surface. A weak layer that is almost always found in the snowpacks that blanket the Rocky Mountains and occasionally the Cascades and Sierra Nevadas is temperature-gradient snow, or depth hoar. The way to decide whether a temperature-gradient layer is near its collapse point is to test the strength of the overlying layers and the support provided around the edges of the slope. This is no easy task. One method is to try jumping on your skis while standing on a shallow slope. Collapse is a good indication that similar snow cover on a steeper slope will produce an avalanche. Often, skiers and climbers cause inadvertent collapses while skiing or walking on a depth hoar–riddled snowpack. The resulting “whoomf” sound is a warning of weak snow below. Finally, a weak layer can be created within the snow cover when surface melting or rain causes water to percolate into the snow and then fan out on an impermeable layer, thereby lubricating that layer and destroying its shear strength. Combining the contributory factors on a day-by-day basis is the avalanche forecaster’s art. Every avalanche must have a weak layer to release on, so knowledge of snow stratigraphy, or layering, and what sort of applied load will cause a layer to fail is the essence of forecasting.


SAFE TRAVEL IN

AVALANCHE TERRAIN

The first major decision often faced in backcountry situations is whether to avoid or confront a potential avalanche hazard. A group touring with no particular goal in mind will probably not challenge avalanches. For this group, education to recognize and avoid avalanche terrain is sufficient. In the other extreme, mountaineering expeditions that have specific goals and are willing to wait out dangerous periods or take severe risks to succeed need considerably more information. Traveling safely in avalanche terrain requires special preparations, including education and possession of safety and rescue equipment. The group should have the skills required to anticipate and react to an avalanche.

Identifying Avalanche Terrain Because most avalanches release on slopes of 30 to 45 degrees, judging angle is a prime skill for recognizing potential avalanche areas. An inclinometer can be used to measure slope angles. Some compasses are also equipped for this purpose; a second needle and a graduated scale in degrees can be used to measure slope angles. A ski pole may be used to judge approximate slope angle. When dangled by its strap, the pole becomes a plumb line from which the slope angle can be “eyeballed.” Evidence of fresh avalanche activity—the presence of fracture lines and the rubble of avalanche snow on the slope or at the bottom—identifies avalanche slopes. Other clues are swaths of missing trees or trees that are bent downhill or damaged, especially with the uphill branches removed. Above treeline, steep

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bowls and gullies are almost always capable of producing avalanches.

Route Finding Good route-finding techniques are necessary for safe travel in avalanche terrain (Fig. 2-18). The object of a good route in avalanche country is more than avoiding avalanches. It should also be efficient and take into account the abilities and desires of the group to choose a route that is not overly technical, tiresome, or time consuming. The safest way to avoid avalanches is to travel above or below and well away from them. When taking the high route, the traveler should choose a ridgeline that is above the avalanche starting zones. It is safest to travel the windward side of the ridge. The snow cover is usually thinner and windpacked, with rocks sticking through—not the most pleasant skiing, but safe. Cornice collapses present a very real hazard; they should be avoided by staying on the roughened snow more to windward. Skiers taking the low route in the valley should not linger in the runouts of avalanche paths. Even though it is unlikely that a skier traveling along the valley could trigger an avalanche high up on the slope, the skier should not boost the odds of getting caught in an avalanche released by natural forces far above. Slopes of 30 degrees or more should be avoided. By climbing, descending, and traversing only in gentle terrain, avalanche terrain can be avoided.

Stability Evaluation Tests Skiers can perform several tests of stability. On a small slope that is not too steep (and therefore will not avalanche), the skier can try a ski test by skiing along a shallow traverse and then setting the ski edges in a hard check. Any cracks or settlement noises indicate that the same slope, if steeper, would have probably avalanched, and on the steeper slope it would have taken less weight or jolt to cause the avalanche. Another test is to push a ski pole into the snow, handle end first. This helps to feel the major layering of the snowpack. For example, the skier may feel the layer of new snow, midpack stronger layers, and depth hoar layers, if the pole is long enough. Hard-snow layers and ice lenses resist penetration altogether. This test reveals only the gross layers; thin weak layers, such as buried surface hoar or a poor bond between any two layers, cannot be detected. Thus, the ski pole test has limited value. A much better way to directly observe and test snowpack layers is to dig a hasty snowpit. (This is an excellent use of the shovel that, in the next section, we recommend the skier carry.) In a spot as near as possible to a suspected avalanche slope without putting the traveler at risk, a pit 4 to 5 feet (120 to 150 cm) deep and 3 feet (90 cm) wide should be dug. With the shovel, the uphill wall is shaved until it is smooth and vertical. Now the layers of snow can be observed and felt. The tester can see where the new snow touches the layer beneath, poke the pit wall with a finger to test hardness, and brush the pit wall with a paintbrush to see which layers are soft and fall away and which are hard and stay in place after being brushed. By grabbing a handful of depth hoar, the skier can see how large the grains are and how poorly they stick together. The shovel shear test gauges the shear strength between layers and thus locates weak layers. First a column of snow is isolated from the vertical pit wall. Both sides and the back of the column are cut with the shovel or a ski, so that the column is free

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Poor route

Poor route

Good route

Good route

Gentle slopes te

d oo

rou

G

Poor route Poor route

Steep slopes

Good route

Figure 2-18. Four ski-touring areas showing the safer routes (green dashed lines) and the more hazardous routes (red dotted lines). Arrows indicate areas of wind loading. (From USDA Forest Service: Avalanche Handbook, Agricultural Handbook 489, with permission. Photo by Alexis Kelner.)

Chapter 2: Avalanches

A

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B

Figure 2-19. A, A small-size Avalanche ABS backpack with deployed airbags. The airbags are stowed in outside pockets of the backpack. B, Integrated into a backpack, the Avalanche ABS is deployed by pulling the white “T” handle. (Courtesy Peter Aschauer, GmbH.)

standing. The dimensions are a shovel’s width on all sides. The tester inserts the shovel blade at the back of the column and gently pulls forward on the handle. An unstable slab will shear loose on the weak layer, making a clean break; the poorer the bond, the easier the shear. A five-point scale is used to rate the shear: “very easy” if it breaks as the column is being cut or the shovel is being inserted; “easy” if a gentle pull on the shovel does the job; “moderate” if a slightly stronger shovel-pry is required; “hard” if a solid tug is required; “very hard” if a major effort is needed to break the snow. Generally, “very easy” and “easy” shears indicate unconditionally unstable snow, “moderate” means conditionally unstable, and “hard” and “very hard” mean stable. The value of the shovel shear test is that it can find thin weak layers undetectable by any other method. Its shortcoming is that it is not a true test of stability, as it does not indicate the amount of weight required to cause shear failure. A test that does a better job of indicating actual stability is the Rutschblock, or shear block, test. This test is calibrated to the skier’s weight and the stress he or she would put on the snow. Again, a snowpit is dug with a vertical uphill wall, but the pit must be about 8 feet (240 cm) wide. By cutting into the pit wall, the skier isolates a block of snow that is about 7 feet (210 cm) wide (a ski length) and goes back 4 feet (120 cm) (a ski pole length) into the pit wall. Both sides and the back are cut with a shovel or ski so that the block is free standing. Wearing skis, the skier climbs around and well uphill from the isolated block and carefully approaches it from above. With skis across the fall line, the skier gently steps onto the block, first with the downhill ski and then the uphill ski, so that he or she is standing on the isolated block of snow. If the slab of snow has not yet failed, gently flexing the knees applies a little more pressure. Next some gentle jumps are tried. The stress should be increased by jumping harder until the block eventually shears loose or crumbles apart. The results are interpreted as “extremely unstable” if the block fails while the skier is cutting it, approaching it from

above, or merely standing on it; “unstable” if it fails with a knee flex or one gentle jump; “moderately stable” if it fails after repeated jumps; and “very stable” if it never fails but merely crumbles. These are objective results that help answer the bigger question—will it slide?—and help the mountain traveler decide how much risk to take.

Avalanche Rescue Equipment Shovel The first piece of safety equipment the skier or climber should own is a shovel. It can be used to dig snowpits for stability evaluation, and snow caves for overnight shelter. A shovel is also needed for digging in avalanche debris, as such snow is far too hard for digging with the hands or skis. The shovel should be sturdy and strong enough to dig in avalanche debris, yet light and small enough to fit into a pack. There is no excuse for not carrying a shovel. Shovels are made of aluminum or high-strength plastic and can be collapsible. Many good types are available in mountaineering stores.

Probe Several pieces of equipment are designed specifically for finding buried avalanche victims. The first is a collapsible probe pole. Organized rescue teams keep rigid poles in 10- or 12-foot (3 to 4 m) lengths as part of their rescue caches. The recreationist can buy probe poles of tubular aluminum or carbon fiber that come in 18-inch (45-cm) sections that fit together to make a fulllength probe. Ski poles with removable grips and baskets can be screwed together to make an avalanche probe. Survivors of an accident use probes to search for buried victims.

Avalanche Rescue Beacon Avalanche rescue beacons, or transceivers, have become the most-used personal rescue device worldwide. When used properly, they are a fast and effective way to locate buried avalanche victims. In the United States, these have become standard issue

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for ski area patrollers involved in avalanche work and for helicopter-skiing guides and clients. They are also commonly used by highway departments, search and rescue teams, and an increasing number of winter recreationists. Since beacons were introduced in the United States, they have saved at least 55 lives. Beacons save at least three or four lives per winter. All transceivers act as transmitters that emit a signal on a world-standard frequency of 457 kHz. A buried victim’s unit emits this signal, and the rescuers’ units receive the signal. The signal carries 30 to 46 m (100 to 150 feet) and, once picked up, guides searchers specifically to the buried unit. Beacon technology is evolving rapidly and the beacons on the market are improving. Two types of beacon have emerged: analog, which processes the signal in the traditional way to allow for a stronger (louder) signal as the receiving beacon approaches the sending beacon, and digital, which uses a computer chip to process the signal, displaying a digital readout of the distance and the general direction to the buried unit. Transceivers are not radio devices but are audio-magnetic-induction devices, so the directional arrows point only along a flux line of the sending unit’s magnetic field. Likewise, the displayed distance is the distance along a flux line rather than a direct distance to the sending unit. Both the analog and the digital types operate on the same frequency and therefore are compatible with one another. However, slightly different search techniques may be necessary to use each type most efficiently, and special training and practice are required before the user attains proficiency. The main brands available in the United States are ARVA, Barryvox, Ortovox, Pieps, Tracker, and SOS. Merely possessing a beacon does not ensure its lifesaving capability. Frequent practice is required to master a beaconguided search, which may not be straightforward. Skilled practitioners can find a buried unit in less than 5 minutes once they pick up the signal. Because speed is of the essence in avalanche rescue, beacons are certainly lifesavers. The best-proven rescue equipment is a beacon for a quick find, a collapsible probe pole to confirm and pinpoint the spot, and a shovel for a quick recovery (Box 2-1).

Avalanche Airbag In 1995, a new rescue device made in Germany was introduced in Europe. The ABS Avalanche Airbag System (Fig. 2-19) was originally designed specifically for guides and ski patrollers but today can be used by anyone venturing into avalanche terrain. Since 1995, the system has undergone continued and significant improvements. The airbag works because of inverse segregation. An avalanche in motion is composed of many different-sized particles of snow. Because of gravity, granular flows segregate, with smaller particles sinking to the lower portion of the flow and larger particles rising to the surface. The process of inverse segregation depends primarily on the relative sizes of the particles in a granular flow. A person is already a large particle and the airbag makes the user an even larger particle, making the separation effect even greater. The airbag is integrated into a special backpack, and the user deploys it by pulling a ripcord-like handle. This releases a cartridge of nitrogen gas that escapes at high velocity and draws in outside air through jets that inflate two 75-L airbags in 2 seconds. By 2004, there had been about 70 documented uses of the ABS Avalanche Airbag System, with three deaths. In one case

the airbag failed to work, and in the second case the user did not or could not deploy the airbag. The third incident involved a user who successfully deployed the airbag, only to be completely buried by a second avalanche moments later. Despite these failures, Brugger and Falk in an expanded study found that the ABS reduces the likelihood of burial from 39% to 16.2%.5 The ABS system is the most effective piece of equipment for saving lives in avalanche terrain. Brugger and Falk showed that it reduces mortality significantly, from 23% to 2.5% compared with the 75.9% to 66.2% reduction for avalanche rescue transceivers.5 This dramatic reduction in mortality occurs because the ABS system prevents burial, and very few partly buried or not buried victims (about 4% to 5%) die in avalanches. Commercial sales of ABS system in the United States have been delayed because of problems obtaining certification for the nitrogen-gas cartridges. The German company hopes to have U.S. Department of Transportation approval in 2007.

AvaLung In 1996, Dr. Thomas Crowley received a patent for an emergency breathing device to extract air from the snow surrounding a buried avalanche victim. The AvaLung functions as an artificial air pocket whose goal is to prolong survival time for the buried victim. Black Diamond Equipment, Ltd. (Salt Lake City, Utah) secured distribution rights in 2000 and redesigned the device in 2002. Called the AvaLung 2, it is worn outside the clothing like a bandoleer. If buried, the victim can breathe through a mouthpiece and inhale air from the surrounding snow. The carbon dioxide (CO2)-rich exhaled air is redirected into another area of the snow, reducing re-inhalation of CO2 (see Avalanche Victim Physiology and Medical Treatment after Rescue, later). The AvaLung system has been proven in numerous simulated burials, allowing subjects to breathe for 1 hour in tightly packed snow, including dense, wet snow. As of 2004, there were three known uses in avalanches. In two cases, the burials were very short, but in a third case a helicopter skier survived a 4-foot (120-cm) burial of 35 to 45 minutes. The ABS Avalanche Airbag and the AvaLung are designed to help avalanche victims and are an adjunct to the basic companion rescue equipment of transceiver, probe, and shovel. These devices should never be used to justify taking additional risks. Because surviving any avalanche is uncertain, this equipment should never replace good judgment.

Crossing Avalanche Slopes Travel through avalanche country always involves risk, but certain travel techniques can minimize that risk. Proper travel techniques might not prevent an avalanche release but can improve the odds of surviving. The timing of a trip has a lot to do with safety. Most avalanches occur during and just after storms. Waiting a full day after a storm has ended can allow the snowpack to react to the new snow load and gain strength. Before crossing a potential avalanche slope, the skier or hiker should get personal gear in order by tightening up clothing, zipping up zippers, and putting on hat, gloves, and goggles. Clothing should be padded and insulating. If a heavy mountaineering pack is carried, the straps should be loosened or slung over one shoulder only, so that the pack can be easily discarded if the person is knocked down. A heavy pack makes a person

Chapter 2: Avalanches

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Box 2-1. Avalanche Transceiver Search INITIAL SEARCH

Grid Search

1. Have everyone switch their transceivers to “receive” and turn the volume to “high.” 2. If enough people are available, post a lookout to warn others of further slides. 3. Should a second slide occur, have rescuers immediately switch their transceivers to “transmit.” 4. Have rescuers space themselves no more than 30 m (100 feet) apart and walk abreast along the slope. 5. For a single rescuer searching within a wide path, zigzag across the rescue zone. Limit the distance between crossings to 30 m (100 feet). 6. For multiple victims, when a signal is picked up, have one or two rescuers continue to focus on that victim while the remainder of the group carries out the search for additional victims. 7. For a single victim, when a signal is picked up, have one or two rescuers continue to locate the victim while the remainder of the group prepares shovels, probes, and medical supplies for the rescue.

1. When a signal is picked up, stand and rotate the transceiver, which is held horizontally (parallel with the ground), to obtain the maximum signal (loudest volume). Maintain the transceiver in this orientation during the remainder of the search. 2. Turn the volume control down until you can just hear the signal. Walk in a straight line, down the fall line from where the signal was first detected. (If the signal fades immediately, walk up the fall line.) If you are headed in the right direction, the signal will increase; turn the volume control down until the signal fades. Take an extra couple of steps to be sure the signal truly fades. If the signal increases, continue until it fades. 3. When the signal fades, mark the point and turn 180 degrees and walk back toward the starting position. The signal will increase in volume and then fade again; take two additional steps to confirm the fade. Walk back to the middle of the two fade points, this spot may or may not be the point of loudest volume/maximum signal. If you experience two maximum signals, go to the midpoint between the two maximums. 4. At this point, turn 90 degrees in one direction or the other. From that position, reorient the transceiver (held parallel with the ground) to locate the maximum signal. After orienting the transceiver to the maximum signal, reduce the volume, and begin walking forward. If the signal fades, turn around 180 degrees and begin walking again. 5. As the signal volume increases, repeat steps 3 and 4 until you have reached the lowest volume control setting on the transceiver. (Be sure to always take an extra step or two to confirm the fade point.) This time, when you return to the middle of the fade points, you should be very close to the buried victim and can now begin pinpointing him or her. a. While stationary, orient the transceiver to receive the maximum signal (loudest volume). At this point, turn the volume control all the way down. b. With the transceiver just above the surface of the snow, continue doing the grid search pattern two to four more times. Always sweep the transceiver a couple of feet beyond the fade point to confirm the fade point. c. Find the signal position halfway between fade points (i.e., at the loudest signal). At this point, you should be very close to the victim’s position and can begin to mechanically probe. Speed is essential. With practice, the transceiver will be accurate to less than one fourth of the burial depth. A 4-foot burial should result in about a 1-foot square at the surface. d. Pinpointing with a digital transceiver: Depending on the brand, pinpointing with a digital transceiver will use a slight variation or combination of the induction line and grid techniques. Be sure to study the owner’s manual.

LOCATING THE VICTIM

With practice, the induction line search is more efficient than the conventional grid search for getting close to the sending beacon, but the conventional grid search is still necessary to pinpoint the buried victim. The induction line search is very similar to the flux line search used by digital transceivers. Users should always study the owner’s manual to learn the best techniques for the specific brand of avalanche rescue beacon. Induction Line Search (Preferred Method)

When an induction line search is used, the rescuer may initially follow a line that leads away from the victim (Fig. 2-30). Remember to lower transceiver volume if it is too loud, because the ear detects signal strength variations better at lower volume settings. 1. After picking up a signal during the initial search, hold the transceiver horizontally (parallel with the ground), with the front of the transceiver pointing forward (see Figure 2-30A). 2. Holding the transceiver in this position, turn until the signal is maximal (maximum volume), then walk five to seven steps (about 5 m), stop, and turn again to locate the maximum signal (see Figure 2-30B). When locating the maximum signal, do not turn yourself (or the transceiver) more than 90 degrees in either direction. If you rotate more than 90 degrees to locate the maximum signal, you will become turned around and follow the induction line in the reverse direction. 3. Walk another five steps, as just described, and then stop and orient the transceiver toward the maximum signal. Reduce the volume. 4. Continue repeating these steps. You should be walking in a curved path along the “induction line” toward the victim (see Figure 2-30C). 5. When the signal is loud at minimum volume setting, you should be very close to the victim and can begin the pinpoint search (see next).

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PART ONE: MOUNTAIN MEDICINE

top-heavy, making it difficult to swim with the avalanche. The skier should remove pole wrist straps and ski runaway straps, because poles and skis attached to the victim hinder swimming motions and only serve to drag the victim under. Finally, a person wearing a rescue beacon should be certain it is transmitting. If possible, the person should cross low on the slope, near the bottom or in the runout zone. Crossing rarely causes a release in the starting zone far above. The greater risk is getting hit by an untimely natural release from above. If crossing high without reaching the safety of the ridge is necessary, the starting zone should be traversed as high as possible and close to rocks, cliff, or cornice. Should the slope fracture, most of the sliding snow will be below and the chance of staying on the surface of the moving avalanche will be better. Invariably, the person highest on the slope runs the least risk of being buried. A person who must climb or descend an avalanche path should keep close to its sides. Should the slope fracture, escaping to the side improves the chance of surviving. Only one person at a time should cross, climb, or descend an avalanche slope; all other members should watch from a safe location. Two commonsense principles lie behind this advice. First, only one group member is exposed to the hazard, leaving the others available as rescuers. Second, less weight is put on the snow. All persons should traverse in the same track. This not only reduces the amount of work required but also disturbs less snow, which lowers the chance of avalanche release. Skiers and climbers should never drop their guard on an avalanche slope. They should not stop in the middle of a slope, but only at the edge or beneath a point of protection, such as a rock outcropping. It is possible for the second, third, or even tenth person traversing or skiing down a slope to trigger the avalanche. Trouble should always be anticipated, and an escape route, such as getting to the side or grabbing a tree, should be kept in mind.

Avalanche Rescue Self Rescue Escaping to the Side. The moment the snow begins to move around the person, there is a split second in which to make a decision or make a move. The person should shout to alert companions and then close the mouth and breathe through the nose to prevent inhalation of a mouthful of snow. Whether on foot, skis, or snowmobile, the person should first try to escape to the side of the avalanche or try to grab onto a tree. Staying on one’s feet or snow machine gives some control and keeps the head up. Escaping to the side gets the person out altogether or to a place where the forces and speeds are less. Turning skis or the snow machine downhill in an effort to outrun the avalanche is a bad move: the avalanche invariably overtakes its victims. Swimming. For years, the command to swim if caught in an avalanche was dogma. However, in recent years the effectiveness of swimming is being called into question. It is the process of inverse segregation (see Avalanche Airbag, earlier) rather than swimming that keeps the victim on or near the surface. The most important thing to do when caught and being tumbled is to get a hand or both hands in front of the face to create an air pocket. Cumbersome or heavy gear should be discarded. Ski poles should be tossed away; with luck, the avalanche will strip

away the skis. Skiers should try to discard gear, but snowmobile riders should try to stay on their snow machine. Once off their machine, riders are twice as likely to be buried as are their machines. Human-triggered avalanches tend to stop abruptly and almost instantly lock the person in place. There is no further chance to move hands to the face to create an air pocket, and without an air pocket, very few buried victims survive.

Reaching the Surface. Anyone caught in an avalanche should fight for his or her life. Creating an air pocket is the key to survival, but some victims, sensing themselves to be near the surface, have thrust out a hand or a foot. Any clue on the surface that gives the rescuers something to see greatly improves the odds of survival.

Companion Rescue Marking the Last-Seen Area. A companion or eyewitness to an accident needs to act quickly and positively. The rescuer’s actions over the next several minutes may mean the difference between life and death for the victim. First, the victim’s lastseen spot should be fixed and marked with a piece of equipment, clothing, a tree branch, or anything that can be seen from a distance down-slope. It is usually safe to move out onto the bed surface of an avalanche that has recently run. It is dangerous when the fracture line has broken at midslope, leaving a large mass of snow still hanging above the fracture. Searching for Clues. The fall line should be searched below the last-seen area for any clues of the victim. The snow should be scuffed by kicking and turning over loose chunks to look for anything that might be attached to the victim or that will reveal the victim’s trajectory and thus narrow the search area. Shallow probes should be made into likely burial spots with an avalanche probe, ski, ski pole, or tree limb. Likely spots are the uphill sides of trees and rocks, and benches or bends in the slope where snow avalanche debris piles up. The toe of the debris should be searched thoroughly; many victims are found in this area. Rescue Beacons. If the group was using beacons, all companions must immediately switch their units to receive mode. While making the fast scuff-search for visual clues, companions should at the same time search the debris, listening for the beeping sound from the buried beacon. When they detect a signal, companions must narrow the search area quickly. If skilled with a transceiver, companions can pinpoint the burial site in a few minutes. Going for Help. A difficult question in rescues is when to seek outside help. If the accident occurs in or near a ski area and there are several companions, one person can be sent to notify the ski patrol immediately. If only one companion is present, the correct choice is harder. The best advice is to search the surface quickly but thoroughly for clues before leaving to notify the patrol. If a patrol phone is close, the companion should notify the patrol and wait to accompany the patroller back to the avalanche. If the avalanche occurs in the backcountry far from any organized rescue team, all companions should remain at the site. The guiding principle in backcountry rescues is that companions search until they cannot or should not continue. When

Chapter 2: Avalanches

55

Organized Rescue Three-Stage Rescue. A full-scale avalanche search-and-rescue operation is divided into three stages. The goal of stage I is to find and extricate the buried victim or victims. Teams of rescuers dispatched to the avalanche are known as columns. The first team—known as the hasty search team—should consist of skilled and swift-traveling rescuers competent in not only avalanche rescue but also route finding and hazard evaluation. Basic rescue tools for stage I are probes, shovels, avalanche rescue dogs, the RECCO system (see later), and basic first-aid equipment. The hasty team performs the initial search, looking for clues with hopes of making a quick find. If unlucky, the team determines the most likely burial areas. The person reporting the avalanche should meet rescuers at the accident site, or the reporting person should be returned to the same vantage point from where they witnessed the accident to best guide rescuers to locate last-seen areas. Arriving rescuers continue the hasty search until sufficient clues can steer rescuers to positioning probe lines. The goal of stage II is to provide emergency medical care and evacuation. This stage consists of one or two small teams to transport resuscitation and medical equipment along with sleeping bags and rescue sleds to the site. Ideally, stage II should begin 10 to 15 minutes after the start of stage I to ensure that necessary medical and evacuation equipment reach the site. Stage I often continues long after stage II has been deployed. Stage III provides support for stages I and II when the rescue is prolonged. This support may include additional rescuers to take over for cold and tired searchers, hot food and drink, tents, warm clothing, and perhaps lights for nighttime searching. Probing. Probing avalanche debris is a simple but slow method of searching for buried victims. For more than 40 years, the traditional probe line used by rescue teams was composed of about a dozen rescuers standing elbow to elbow with a probe pole 3 to 3.5 m (about 10 to 12 ft) long. The rescuers would probe once between their feet—each probe entering the snow about 75 cm (30 inches) from the neighbors on either side—and then advance 70 cm (about 30 inches) and probe again. The probability of detection (POD) was thought to be about 70% to 76%. If the probe line missed on the first pass—which tended to happen—the area was probed again and again. Behind the probe line, shovelers stood ready to check out any possible strike. The line did not stop in such an event but continued to march forward with a methodical “down, up, step” cadence. Canadian avalanche workers modified this traditional probe line method in the late 1990s when they found it more efficient to probe three times per step rather than one time per step and slightly tightened the probe-grid spacing. However, experience showed that for all probe lines, the PODs were much less than described in the literature. In 2004, Ballard and colleagues developed a computer program that simulated a human body in an avalanche and compared the probabilities of detection for any probe-grid spacing.1 The results showed the POD for the traditional probe line to be 59% rather than the 70% believed earlier. As probe-grid spacings were reduced, the POD increased, but the search times also increased. Rescuers must balance the speed of the search with the length of time of the

50cm

deciding when to stop searching, the safety of the companions must be weighed against the decreasing survival chances of the buried victim.

50cm

50cm

Figure 2-20. Three-probe spacing for 50 × 50-cm three-hole-per-step probe method.

search. At a grid spacing of less than 50 cm, the search time increased faster than the POD. Thus, a grid spacing of 50 by 50 cm (20 by 20 inches) was optimal, yielding the best combination of POD and search time. For a three-hole-per-step (3HPS) probe, probers stand with arms out, wrist to wrist. Probers first probe between their feet and then probe 50 cm to the right and then 50 cm to the left (Fig. 2-20). At a command from the leader, the line advances 50 cm (one step). This method gives an 88% chance of finding the victim on the first pass with an estimated time to discovery that is nearly identical to the traditional spacing. Ski patrols and mountain rescue teams that have adopted the 3HPS with a 50 × 50-cm grid have been pleased with the improved efficiency and effectiveness of the probe line. Because rescuers insert more probes per rescuer, it is possible to have fewer rescuers on a probe line, and short probe lines are easier to manage and faster than long probe lines. Five rescuers doing 3HPS at 50-cm intervals form a slightly longer probe line than nine rescuers using the traditional method. To ensure proper spacing, it is most helpful to use a guidon cord with marked 50-cm intervals. Suspended between two rescuers, the lightweight guidon cord positions rescuers and probes to the right spots, allowing the line to move smoothly and efficiently without interruption. When a guidon cord is not used, the probe line must be frequently stopped and reassessed to ensure proper spacing. Rescuers managing the guidon cord should also place red flags every 3 to 5 m to mark the edge of the searched area. If the victim is missed on the first pass, the second pass can be offset by 25 cm (10 inches) in each direction and the area researched. The second pass increases the POD to 99%. Rescue teams use probe lines to find most avalanche victims not equipped with transceivers, RECCO reflectors, or when an avalanche rescue dog fails to locate the victim. However, these search methods should all be used concurrently. Because probe lines are time intensive, few victims are found alive by this technique alone (see Table 2-2).

RECCO. RECCO (RECCO AB, Sweden, www.recco.com) is an electronic rescue system that enables organized rescue teams to find victims who are equipped with a reflector (Fig. 2-21). The system consists of two parts: a detector used by the rescue teams (either on the ground or from helicopters) and the reflector worn by the recreationist. About the size and weight of a notebook computer, the detector is easily transported to the accident site. The detector transmits a directional radar signal. When it hits the reflector, the signal’s frequency is doubled and reflected back to the detector, and the rescuer can follow the

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PART ONE: MOUNTAIN MEDICINE

A

B

Figure 2-21. A, The RECCO reflector is a thin circuit card covered in soft plastic. It does not need batteries and does not need to be turned on or off.The reflector can be attached to jackets, pants, boots, and helmets. B, The RECCO detector consists of a transmitter and a receiver. It can also be used from a helicopter. (Courtesy RECCO AB, Sweden.)

25 20 15 10 5

2000-01 to 2003-04

1995-96 to 1999-00

1990-91 to 1994-95

1985-86 to 1989-90

1980-81 to 1984-85

1975-76 to 1979-80

1970-71 to 1974-75

1965-66 to 1969-70

0 1960-61 to 1964-65

Avalanche deaths have increased in the United States each decade since 1950. Figure 2-22 shows annual deaths averaged over 5-year periods. From 1950 to 2004, 716 people have died in avalanches. Of these, 566 (79%) were men and 63 (9%) were women. (Interestingly, not all accident reports list the sex of the victim.) The average age of all victims is 30 years. The youngest was 6; the oldest, 67. Figure 2-23 shows the activity groups for the victims. Most victims (86%) were pursuing some form of recreation at the time of the accident, with climbers, backcountry skiers, and snowmobilers heading the list. The backcountry-skiers category also includes ski mountaineers, helicopter skiers, and snowcat skiers. The distinction between backcountry skiers and lift skiers is that lift skiers pursue their sport in and around devel-

30

1955-56 to 1959-60


THE MODERN AVALANCHE VICTIM

35

1950-51 to 1954-55

Avalanche Guard. If the threat of a second avalanche exists, one person should stand in a safe location to shout out a warning. This gives the searchers a few seconds to flee to safety. Rescues are often carried out under dangerous conditions, and self-preservation should be a major consideration.

U.S. Avalanche Fatalities 1950-2004

Average fatalities

signal to the buried person. The reflectors are small, passive (no batteries) electronic transponders that are fitted into outerwear, ski and snowboard boots, and helmets. The system will detect some electronic equipment (with diminished range) such as cell phones, electronic cameras, radios, and even turned-off avalanche rescue beacons, so RECCO should be used by rescue teams together with avalanche rescue dogs, rescue beacons, and probers in the first response to any avalanche rescue. In North America, more than 120 ski areas, mountain rescue teams, and National Parks have detectors. Worldwide, more than 500 ski resorts and helicopter rescue teams have them.

5-year period

Figure 2-22. Avalanche fatalities in the United States averaged by five-winter periods, 1950–51 to 2003–04.

oped ski areas and rely on lifts to get them up the hill. Outof-bounds lift skiers are skiers who leave the ski area boundary or ski into “closed” areas within the ski area. In-area skiers are those caught and killed on open terrain within the ski area boundary; it should be noted that only three deaths have occurred on open runs in the last 30 years. Miscellaneous recreation includes sledders and persons playing in the snow,

Chapter 2: Avalanches

U.S. Avalanche Fatalities by Activity 1950-2004

57

220 200 Number of Fatalities 1950-2004

Climber Ski tourers Snowmobilers Snowboarders Out-of-bounds skiers In-area skiers Snowshoers and hikers Miscellaneous

180 160 140 120 100 80 60 40

Motorists and highway workers

20

Residents

0 CO AK WA UT MT WY ID CA NH NV OR NM NY ME AZ

Others at work Ski patrolers

State

Miners

Figure 2-24. Avalanche fatalities in the United States from 1950–51 to 2003–04 by state.

Rescuers 0

50

100

150

200

Number of fatalities TOTAL = 716

Figure 2-23. Avalanche fatalities in the United States from 1950–51 to 2003–04 by activity categories.

campers, and even a most unlucky ski kayaker. Among nonrecreation groups, avalanches strike houses (residents), highways (motorists and plow drivers), and the workplace (ski patrollers and others whose job puts them at risk). Since 1950, 15 states have registered avalanche fatalities (Fig. 2-24).

Statistics of Avalanche Burials Numerous factors affect a buried victim’s chances for survival: time buried, depth buried, clues on the surface, rescue equipment, injury, ability to fight the avalanche, body position, snow density, presence and size of air pocket, and luck. A victim who is uninjured and able to fight on the downhill ride usually has a better chance of being only partly buried, or, if completely buried, a better chance of creating an air pocket for breathing. A victim who is severely injured or knocked unconscious is like a rag doll being rolled, flipped, and twisted. Being trapped in an avalanche is a life-and-death struggle, with the upper hand going to those who fight the hardest. Avalanches kill in two ways. First, serious injury is always possible in a tumble down an avalanche path. Trees, rocks, cliffs, and the wrenching action of snow in motion can do horrible things to the human body. About one quarter of all avalanche deaths are caused by trauma, especially to the head and neck. Second, snow burial causes asphyxiation (either obstructed airway or hypercapnia) in three quarters of avalanche deaths, and a very small percentage of avalanche victims succumb to hypothermia (see Avalanche Victim Physiology and Medical Treatment after Rescue, later). The problem of breathing in an avalanche does not start with being buried. A victim

swept down in the churning maelstrom of snow has an extraordinarily hard time breathing. Inhaled snow clogs the mouth and nose; asphyxiation occurs quickly if the victim is buried with the airway already blocked. Snow that was light and airy when a skier carved turns in it becomes viselike in its new form. Where the snow might have been 80% air to begin with, it might be less than 50% air after an avalanche, and it is much less permeable to airflow, making it harder for the victim to breathe (but see AvaLung, earlier.) Snow sets up hard and solid after an avalanche. It is almost impossible for victims to dig themselves out, even if buried less than a foot deep. Hard debris also makes recovery very difficult in the absence of a sturdy shovel. The pressure of the snow in a burial of several feet is sometimes so great that the victim is unable to expand the chest to draw a breath. Warm exhaled breath freezes on the snow around the face, eventually forming an ice lens that cuts off all airflow. This takes longer than snowclogged airways, but the result is still death by asphyxiation. Another factor that affects survival is the position of the victim’s head—that is, whether the person is buried face up or face down. Data from a limited number of burials show the victim is twice as likely to survive if buried face up. In the faceup position, an air pocket forms around the face as the back of the head melts into the snow; in the face-down position, an air pocket cannot form as the face melts into the snow. The statistics on survival are derived from a large number of avalanche burials (Figs. 2-25 and 2-26). In compiling these figures, the authors have included only persons who were totally buried in direct contact with the snow. Victims buried in the wreckage of buildings or vehicles are not included, as they can be shielded from the snow and can find sizable air pockets. Under such favorable circumstances, some victims have been able to live for days. In 1982, Anna Conrad lived for 5 days at Alpine Meadows, California, in the rubble of a demolished building, the longest survival on record in the United States. A completely buried victim has a poor chance of survival, which is related to both time and depth of burial, as shown in

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PART ONE: MOUNTAIN MEDICINE

100

Alive Dead % Survival

90 80 70

TABLE 2-1. Rescue Results as a Function of Rescuer, 1950–2004

Found alive Found dead

60 50

SELFRESCUE

COMPANIONS

RESCUE TEAMS

TOTAL

48 (14%) —

198 (60%) 116 (23%)

87 (26%) 383 (77%)

333 499

Type of rescue for buried avalanche victims in direct contact with snow, based on a sample of 832 burials in the United States from 1950–51 to 2003–04.

40 30 20

TABLE 2-2. Rescue Results as a Function of Locating Method, 1950–2004

10

7. 0 

6. 9

5. 9

6. 0-

5. 0-

4. 9 4. 0-

3. 9

2. 9

3. 0-

2. 0-

1. 9 1. 0-

0. 1-

0. 9

0

Feet

Figure 2-25. Percent survival versus depth of burial for U.S. avalanche fatalities and survivors in direct contact with the snow (not in a structure or vehicle) from 1950–51 through 2003–04.

Survival probability (%)

100 Swiss Data 1981 to 1998 (N = 638)4 Swiss Data 1981 to 1991 (N = 422)9

80

Attached object or body part visible Hasty search or spot probe Coarse or fine probe Transceiver Avalanche dog Voice Other (e.g., digging, bulldozer) Found after a long time Not found, not recovered Not known Inside vehicle Inside structure Totals

ALIVE

DEAD

TOTAL

140 26 23 55 6 30 20 0 0 19 30 23 372

54 46 163 83 60 1 14 42 35* 34 10 30 572

194 72 186 138 66 31 34 42 35 53 40 53 944

60 Method of locating (first contact) buried avalanche victims, based on a sample of 944 avalanche burials in the United States from 1950–51 to 2003–04. *Eleven climbers died in an ice avalanche on Mt. Rainier (June, 1981); bodies not recovered.

40 20 0 0

20 40 60 80 100 120 140 160 180 200 220 240 Time buried under avalanche (min)

Figure 2-26. The solid blue line indicates data from Switzerland for survival probability for completely buried avalanche victims in open areas from 1981 to 1998 (N = 638) in relation to time (minutes) buried under the snow.Median extrication time was 37 minutes.The dashed red line represents survival probability for completely buried avalanche victims in open areas (N = 422) based on the Swiss data for 1981 to 1991 as calculated by Falk and colleagues.9 (From Brugger H, Durrer B, Adler-Kastner L, et al: Resuscitation 51:7–15, 2001, with permission.)

Figure 2-25. Survival probabilities diminish with increasing burial depth, partly because it takes longer to uncover the more deeply buried victim. To date, no one in the United States who has been buried deeper than 2.1 m (7 feet) has been recovered alive; however, in Europe, two victims survived burials of 6 to 7 m (20 to 23 ft).7,23 As important as burial depth may be in survival, time is the true enemy of the buried victim. Survival statistics in the United States are very similar to those in Europe. Figure 2-26 presents the European survival probability function, showing decreasing survival with increasing burial time. In the first 15 minutes, more persons are found alive (>90%) than dead. At 30 minutes, an equal number are found

dead and alive. After 30 minutes, more are found dead than alive, and the survival rate continues to diminish with increasing time. Speed is essential in the search. Because under favorable circumstances, buried victims can live for several hours beneath the snow, rescuers should never abandon a search prematurely. A miner in Colorado buried by an avalanche near a mine portal was able to dig himself free from nearly 1.8 m (6 feet) of debris after approximately 22 hours. In 2003, two snowshoe hikers caught near Washington’s Mt. Baker survived burials of 22 and 24 hours. Such long survival times are a reminder that no rescue should be abandoned prematurely on the assumption that the victim is dead.

Rescue Statistics A buried victim’s chance of survival directly relates not only to depth and length of time of burial but also to the type of rescue. Table 2-1 shows the statistics on survival as a function of the rescuer. Buried victims rescued by companions or groups nearby have a much better chance of survival than those rescued by organized rescue teams, time being the major influencing factor. Of those found alive, 60% were rescued by companions and 26% by an organized rescue team. Table 2-2 compares the results of rescue by different techniques. Seventy-two percent of victims (140 of 194) who were

Chapter 2: Avalanches buried with a body part (such as a hand) or an attached object (such as a ski tip) protruding from the snow were found alive. In most cases, this was simply good luck, but in some cases it was the result of actively fighting with the avalanche or of thrusting a hand upward when the avalanche stopped. Either way, this statistic shows the advantages of a shallow burial: less time required to search, shorter digging time, and the possibility of attached objects or body parts being visible on the debris. Of the fatalities in this category, many were skiing or snowboarding alone with no companion to spot the hand or ski tip and provide rescue. Organized probe lines have found more victims than any other method, but because of the time required, most victims (88%) are recovered dead. Only 23 people were found alive by this method, with 163 recovered dead. Rescue transceivers are an efficient technique for locating victims, but two problems have limited the number of survivors even among those wearing them. First, few beacon wearers are well practiced in using the beacon instantly and efficiently, and second, even after a quick pinpointing of the burial location, extricating the victim from deep burials may take too long to save the life. To recover a victim buried 1 m (3 ft) deep, companions have to remove at least 1.5 tons of snow. Since the first transceiver rescue in 1974, only 40% (55 of 138) of buried victims found with transceivers have been recovered alive. As dismal as this statistic is, there is a bright spot within the data. Prior to 2000, only 30% of transceiver users survived, but since 2000, 57% have survived burials (P = .003). The year 2000 marks the beginning of widespread use of digital avalanche rescue transceivers, which most people find easier to use. However, transceivers still do not guarantee a live rescue, which requires regular practice and training along with a dose of good luck. Despite the sound-insulating properties of snow, 31 victims who were shallowly buried were able to yell and be heard by rescuers (voice contact). An unfortunate case was the man whose moans were heard but who was dead when uncovered 20 minutes later. Trained search dogs are capable of locating buried victims very quickly, but because they are often brought to the scene only after extended periods of burial, there have been few live rescues. In the March 1982 avalanche disaster at Alpine Meadows, California, a dog made the first live recovery of an avalanche victim in the United States. Since then, dogs have made five additional live recoveries. Search and rescue teams and law enforcement agencies work closely with search dog handlers, and trained avalanche dogs are becoming common fixtures at ski areas in the western United States. A trained avalanche dog can search more effectively than 30 searchers. It moves rapidly over avalanche debris using its sensitive nose to scan for human scent diffusing up through the snowpack. Dogs are not 100% effective, however: they have found bodies buried 10 m deep but have also passed over some buried only 2 m (6 ft) deep. These statistics point out the extreme importance of rescue skills. Organized rescue teams, such as ski patrollers and mountain rescuers, must be highly practiced. They must have adequate training, manpower, and equipment to perform a hasty search and probe the likely burial areas in a minimal time. For backcountry rescues, a buried victim’s best hope for survival is to be found by the companions. The need to seek outside rescue units practically ensures a body recovery mission.

59

Avalanche Victim Physiology and Medical Treatment after Rescue Avalanche Victim Morbidity and Mortality Asphyxiation is the most common cause of death during avalanche burial. About 75% of avalanche deaths result from asphyxiation, about 25% from trauma, and very few from hypothermia.13,16,22,24 Because asphyxiation is the major cause of death during avalanche burial, time to extrication is a major determinant of survival. Fully buried avalanche victims have a greater than 90% chance of survival if extricated within 15 minutes, but only 30% after about 35 minutes (see Figure 2-26),4,9 emphasizing the need for companion rescue at the avalanche site. Survival beyond 30 minutes of burial requires an air pocket for breathing, and if the air pocket is large enough, avalanche victims may survive for hours and develop severe hypothermia. Traumatic injury to avalanche victims depends on the terrain where the avalanche occurred. If the victim is carried through trees or over rock bands, then traumatic injury is more likely and may result in death. Grossman and colleagues, using data that included both partial and complete burials in Utah and Europe, reported that traumatic injuries occurred in 25% of survivors of avalanche accidents13 (Table 2-3). The most common traumatic injuries were major orthopedic, soft tissue, and craniofacial injuries. Johnson and colleagues reviewed autopsy reports from 28 avalanche deaths in Utah over a 7-year period. Among 22 avalanche victims who died from asphyxiation, half had mild or moderate traumatic brain injury, which the authors argued could cause a depressed level of consciousness and contribute to death from asphyxiation.14 All six of the avalanche deaths that were due to trauma had severe traumatic brain injury.

Respiratory Physiology of Avalanche Burial Asphyxiation occurs during avalanche burial because inhaled snow occludes the upper airway or because expired air is rebreathed. Acute upper airway obstruction resulting in asphyxiation is one of the causes of early asphyxiation—that is, during the first 15 to 30 minutes of avalanche burial. Asphyxiation due to rebreathing expired air may also occur during this time if

TABLE 2-3. Injuries in Survivors of Avalanche Burial (Partial and Total)

Total Injuries Major orthopedic Hypothermia requiring treatment at hospital arrival Skin/soft tissue Craniofacial Chest Abdominal

UTAH

EUROPE

9 (Total, 91 avalanche accidents) 3 (33%) 2 (22%)

351 (Total, 1447 avalanche accidents) 95 (27%) 74 (21%)

1 (11%) — 3 (33%) —

84 (25%) 83 (24%) 7 (2%) 4 (1%)

From Grossman MD, Saffle JR, Thomas F, Tremper B: J Trauma 29:1705–1709, 1989.

PART ONE: MOUNTAIN MEDICINE

100

SpO2 (%)

25

20 80

60 10

FIO2 (%)

15 A

8

6

4

10

B

5

0

FICO2 (%)

there is no air pocket for breathing, or it may be delayed if an air pocket is present. Inspired air contains 21% oxygen (O2) and less than 0.03% CO2, whereas expired air contains about 16% O2 and 5% CO2. Rebreathing expired air in an enclosed space results in progressive hypoxia and hypercapnia that will eventually result in death from asphyxiation. The larger the air pocket, the greater is the surface area for diffusion of expired air into the snowpack and for diffusion of ambient air from the snowpack into the air pocket, and thus the longer is the survival time before death occurs from asphyxiation. An ice mask is formed when water in the warm, humid expired air freezes on the snow surface in front of the face. Because this barrier is impermeable to air, it accelerates asphyxiation by preventing diffusion of expired air away from the air pocket in front of the mouth. The physiology of asphyxiation from breathing with an air pocket in the snow was demonstrated in a study by Brugger and colleagues.6 Subjects sat outside a snow mound and breathed through an air-tight mask connected by respiratory tubing to 1or 2-L (0.9- to 1.8-quart) air pockets in snow. The snow had a density similar to that of avalanche debris (i.e., 150 to 600 kg/m3, or 15% to 60% water). The initial fraction of inspired oxygen (Fio2) in the air pocket was 21%, and the initial fraction of inspired CO2 (Fico2) was near 0%. As expired air was rebreathed in the air pocket, Fio2 decreased to about 10% and Fico2 increased to about 6% over 30 minutes (Fig. 2-27). These changes in O2 and CO2 in the air pocket resulted in a decreased arterial O2 saturation as measured by a pulse oximeter (Spo2%) and an increased end-tidal CO2 (ETco2) partial pressure. Most subjects were not able to complete the entire 30 minutes of the study and had to stop secondary to dyspnea, hypercapnia, and hypoxia. Hypoxemia and hypercapnia occur as expired air is rebreathed. A smaller air pocket or denser snow causes a more rapid development of hypoxia and hypercapnia. Larger air pockets and less-dense snow allow more mixing of expired air with ambient air in the snowpack and result in longer survival before hypoxia and hypercapnia become severe enough to cause death from asphyxiation. Brugger and colleagues suggest that an equilibrium may occur where the Fio2 and Fico2 in an air pocket reach a plateau within a physiologically tolerable range, and the avalanche victim may survive prolonged burial. This may occur even with small air pockets, as has been observed in the extrication of survivors of avalanche burials of up to 2 hours in duration.4 Radwin and colleagues18 demonstrated that there is sufficient ambient air in densely packed snow to permit normal oxygenation and ventilation as long as all expired air is diverted out of the snowpack. They studied subjects totally buried in dense snow who inhaled air directly from the snowpack (density, 300 to 680 kg/m3, or 30% to 68% water) through a two-way nonrebreathing valve attached to respiratory tubing that diverted all expired air to the snow surface. Subjects maintained normal oxygenation and ventilation for up to 90 minutes. This study demonstrated that there is sufficient air for breathing in snow with a density similar to that of avalanche debris, as long as expired air is not rebreathed. This is the principle behind the AvaLung (see Avalanche Rescue Equipment, earlier), designed to prolong survival during avalanche burial. Figure 2-28 describes its operation. Although the device prevents ice mask formation, the expired air permeates around the buried person’s body and through the snow and eventually contaminates inspired air. Grissom and colleagues11 compared

ETCO2 (kPa)

60

0 0

5

10

15 20 Time (min)

25

30

Figure 2-27. Curves of individual respiratory parameters in subjects breathing with a tightfitting face mask connected to respiratory tubing running into 1- or 2-L air pockets in dense snow (N = 28).The x-axis represents time in minutes. Some subjects did not complete the 30minute study because of dyspnea or hypoxia. A, Arterial oxygen saturation (SpO2%) as measured by a digital pulse oximeter on the left y-axis (red lines), and fraction of inspired oxygen (FIO2%) on the right y-axis (blue lines). B, Partial pressure of end-tidal CO2 (ETCO2) (kPa) on the left y-axis (red lines) and fraction of inspired CO2 (FICO2%) on the right y-axis (blue lines). (From Brugger H, Sumann G, Meister R, et al: Resuscitation 58:81–88, 2003, with permission.)

breathing with this device while buried in dense snow, and breathing without the device but with a 500-cc (0.45-quart) air pocket in the snow. Mean burial time was 58 minutes when breathing with the device, and 10 minutes when breathing with a 500-cc air pocket in the snow. Development of hypoxia and hypercapnia were significantly delayed by breathing with the device. The AvaLung has resulted in survival from actual avalanche burials.17

Medical Treatment and Resuscitation of Avalanche Burial Victims The key points regarding assessment and treatment of an extricated avalanche burial victim are presented in an algorithm in Figure 2-29. An initial impression of the level of consciousness is made as the head is exposed and cleared of snow. Opening the airway and ensuring adequate breathing are the primary medical interventions. Every effort should be made to clear the

Chapter 2: Avalanches

61

A

B

C d

iam

on

D ck Bla

Figure 2-28. The AvaLung 2 (Black Diamond Equipment,Ltd.,Salt Lake City,UT),a breathing device intended to prolong survival during avalanche burial by diverting expired air away from inspired air drawn from the snowpack, is worn over all other clothing. White arrows show flow of inspiratory air, and red arrows show flow of expiratory air. The subject breathes in and out through the mouthpiece (A). Inhaled air enters from the snowpack through the one-way inspiratory valve on the side of the housing inside the mesh-protected harness on the chest (B). Expired air leaves the lungs via the mouthpiece and travels down the respiratory tubing to the housing and then passes through an expiratory one-way valve located at the bottom of the housing (B) and travels via respiratory tubing inside the harness around to the back (C). (AvaLung photo courtesy Black Diamond Equipment, Ltd.)

airway of snow as soon as possible and to provide assisted ventilation if the breathing is absent or ineffective. These measures should not wait until the entire body is extricated. If traumatic injury to the spinal column is suspected, or if there is evidence of head or facial trauma, then the spinal column is immobilized as the airway is opened, adequate breathing ensured, and oxygen provided. When the avalanche burial victim is unconscious, maintenance of the airway may be challenging because of the space limitations of the snow hole. If endotracheal intubation is required for the unconscious apneic patient not yet fully extricated from snow burial, then the inverse intubation technique19 may be required. In this technique, the laryngoscope is held in the right hand while straddling the patient’s body and facing the head and face. While facing the patient, insert the laryngoscope blade into the oropharynx with the right hand so that the larynx and cords can be visualized by leaning over and looking into the patient’s mouth; the endotracheal tube is then passed through the cords with the left hand. After an adequate airway and breathing are established and supplemental oxygen is provided, the circulation is assessed. The conscious patient is assumed to have a perfusing rhythm, and further treatment is directed at treating mild hypothermia and traumatic injuries. A patient found unconscious but with a pulse may have moderate or severe hypothermia and should be handled gently to avoid precipitating ventricular fibrillation (VF). Medical treatment of this patient is focused on ensuring adequate oxygenation and ventilation, either noninvasively

with a bag-valve-mask device or by endotracheal intubation if clinically indicated, and on immobilizing the spinal column for transport and treating any obvious signs of trauma. Intravenous access may be obtained and warmed isotonic fluids infused. The treatment of hypothermia is described later. If a pulse is not present after opening the airway and ventilating the patient, cardiopulmonary resuscitation (CPR) is begun. Before CPR is initiated, however, careful evaluation for the presence of a pulse should occur. Avalanche burial victims are hypothermic, which causes peripheral vasoconstriction and makes the pulse difficult to palpate. In addition, moderate to severe hypothermia causes depression of respiration and bradycardia. Before initiating CPR, palpation for a pulse should be done for a period of 30 to 45 seconds after the airway is opened and assisted ventilations are begun. CPR initiated on a severely hypothermic patient who actually has a perfusing rhythm may cause VF. If electrocardiographic monitoring is available, the cardiac rhythm is assessed, or alternatively an automatic external defibrillator may be applied. If the patient has VF, up to three defibrillations are attempted in the moderate or severely hypothermic patient with a core body temperature less than 30° C (86° F).8 If these are unsuccessful, further attempts at defibrillation are done only after rewarming. Drugs usually administered as part of advanced cardiac life support (ACLS) are not effective below a core body temperature of about 30° C, and they may accumulate to toxic levels with a rebound effect as rewarming occurs.8 If the patient is hypothermic but

62

PART ONE: MOUNTAIN MEDICINE

Extrication from avalanche burial

Conscious?

Treat for Hypothermia I (core temperature 32° C or 90° F) or Hypothermia II (28° to 32° C or 82° to 90° F): Clear the airway; provide oxygen, dry warm insulation, hot drink containing sugar if awake, and medical transport to closest appropriate facility.

Yes

No Breathing?

Treat for Hypothermia II (core temperature 28° to 32° C or 82° to 90° F) or Hypothermia III (24° to 28° C or 75° to 82° F): Clear the airway; provide oxygen, assist ventilations, consider intubation and ventilation with heated and humidified oxygen, provide dry warm insulation, infuse heated IV fluid, and provide medical transport to tertiary care facility.

Yes

No Obvious fatal injuries? No

Yes

Cease efforts

Clear the airway, assist ventilations, provide oxygen, intubate, infuse warm IV fluids, and handle gently. Check for pulse after ventilating and oxygenating. If no pulse, start CPR. Check ECG.

Heart monitor asystole?

No

If rhythm is VF, defibrillate a maximum of 3 times if core temperature 30° C or 86° F and hold ACLS drugs until rewarmed. Treat for hypothermia III or IV as below.

No

Death from asphyxiation likely; cease efforts when clinically indicated. May continue resuscitation and transport to the nearest appropriate medical facility. A K of greater than 12 mEq/liter suggests that resuscitation may be futile and that death has occurred from asphyxiation.

Yes Burial 1 hour Yes Core temperature 30° C or 86° F?

No

Yes Air pocket and free airway?

No

Yes Treat for hypothermia III or IV (core temperature 28° C or 82° F): Endotracheal intubation, assisted ventilation with warmed humidified oxygen, monitor ECG, begin CPR, infuse warmed IV fluids, provide dry insulation, provide medical transport to a facility capable of extracorporeal rewarming.

Figure 2-29. Assessment and medical care of extricated avalanche burial victims.

has a core body temperature greater than 30° C, the standard ACLS protocol is followed with longer intervals between administrations of drugs. The likelihood of successful resuscitation of an avalanche burial victim who is in cardiac arrest at the time of extrication depends on whether cardiac arrest occurred from asphyxiation or from hypothermia. In burials of less than 1 or 2 hours with a core body temperature of greater than 30° C, resuscitation is unlikely to be successful because death has most likely occurred from asphyxiation. Avalanche victims extricated from burials of greater than 1 or 2 hours who have no signs of life but who are severely hypothermic (core temperature kidney, quadriceps muscle > brain.163 In rat brain, lung, and skin, HSP-70 concentration peaked at 1 hour and returned to baseline at 3 hours after the stress. In liver, however, HSP-70 peaked 6 hours after the stress.48 The

Chapter 10: Pathophysiology of Heat-Related Illnesses

255

determination of HSP-72 may be useful as a diagnostic probe of recent heat injury, as an enzyme-linked immunosorbent assay (ELISA) for HSP-72 determination has become commercially available (Stress-Gen, Vancouver).65 Most studies on HSPs have been carried out in isolated cells and in rodent models. In humans, the minimal conditions of threshold Tc and duration for a single heat shock to induce HSPs is not certain. Some cells can survive very brief exposures (1 second) to temperatures as high as 60° C (140° F), because they induce HSPs that render them thermotolerant.62 After a single heat shock in human peripheral blood mononuclear cells, HSP72 concentration is unchanged for 1 to 2 hours, then rises rapidly to plateau at 4 hours. It gradually falls after 12 to 18 hours but remains above baseline at 24 hours.184 Overall, however, on a single supra-threshold stress, HSPs in many or most tissues rise within an hour or two of the stress and remain elevated for 12 to 48 hours and possibly for as long as a week.224 During sports activities or exercise in summer, however, Tc can become elevated several times over a few hours. Such stimuli may have profound effects on the time course of HSP elevation and protection, but this has not been well studied.247,313 This temporary thermoprotection by HSPs to heat and exercise is not long-term acclimatization. Long-term acclimatization is a different process, although it may in part involve HSPs. It develops over a period of several days in response to several periods of moderate heat and may persist for weeks. In the work of Horowitz,247 acclimatization involves alterations in autonomic, cellular, and molecular responses to heat, varying in their intensities and interrelationships over time. Some studies suggest that increased HSP-72 during rigorous exercise is one of the adaptive mechanisms to cope with 249,328 increased stress. Rats run on a treadmill for 30 minutes per . day at 75% Vo2max showed increases in HSP-72 within 10 weeks.123 Endurance exercise–trained rats had higher levels of HSP-72, as well as lower levels of lipid peroxidation, in their ventricles and could develop higher systolic pressures.122,414 During exercise of an unacclimatized individual in moderate and warm temperatures or at rest in tropical or desert heat, Tc may rise to levels that severely decrement performance or may lead to heatstroke, collapse, and even death. Therefore, the presence of HSPs is extremely important. A better understanding of the role of HSPs may ultimately lead to methods for faster acclimatization to heat. The ability to produce HSPs may depend on diet, because vitamin D–deficient animals showed reduced HSP production.281

swine and improved the course of hemodynamic variables; it decreased peak pulmonary arterial pressure and pulmonary vascular resistance index values, increased systemic arterial pressure and systemic vascular resistance index values, and favorably altered hypodynamic/hyperdynamic CO.296 Elevated HSP-70 (by heat shock) protected rat intestine against toxin (ricin)-induced acute intestinal inflammation, with reduced generation of leukotriene B4 and neutrophilic infiltrate in their ileums.493 Monocytes and granulocytes constitutively express more HSP-70 and are more heat resistant than lymphocytes. LPS raises HSP-70 content even more and may be the reason that those cells can survive and function in hostile inflammatory microenvironments.161 Not only does raising HSP levels protect against heat, but reducing them is damaging during stress. For example, reducing HSP-72 induction by 40% (by a specific toxin) rendered cardiac myocytes more susceptible to hypoxic injury.377 In principle, it may be possible in humans and experimental models to elevate HSPs by one stress (e.g., temporary hypoxia) to render athletes more tolerant to heat, cold, or toxins. This would be expected to benefit not only athletes but also soldiers deployed to hot climates and patients soon to undergo surgery.

Protection. In a number of different systems, HSP levels elevated by a variety of stresses (heat shock, brief cyanide exposure, arsenite, peroxide, hypoxia, and toxins) were beneficial to membranes, cells, tissue, and organs. HSP-70 protected cells and their ultrastructure against these or other stressors.7,51,291,523 They protected against membrane damage caused by toxins (ionomycin) and cytokines.211,316 Well-healing wounds show high levels of hsp70mRNA, whereas poorly healing wounds have lower levels.392 Overexpression of HSP-70 in transgenic mice rendered their hearts more resistant to ischemic injury.344 Human cell types (proximal tubular epithelia) that normally exhibit great resistance to hypoxia also contain high basal levels of HSP-70.512 Elevated HSP-72 (by heat shock or arsenite) protected rats against heatstroke morbidity and mortality.551 Elevated HSP-72 blunted liberation of inflammatory mediators (interleukin-6 and thromboxane B2) in LPS-challenged

Training. Long-term exercise training in the heat induced HSPs. In one study of rat brains, HSP-70 content rose only if the exercising rats became hyperthermic, whereas exercise alone did not induce central HSP-70 expression.523 On the other hand, in another study in rats, in spleen cells, peripheral lymphocytes, and soleus muscles, exercise alone induced HSP-60, HSP-70, HSP-90, and HSP-100.336 In male rowers in training, the HSP70 content in an active muscle rose each week (181%, 405%, 456%, and 363%) with maximal HSP production at the end of the second training week.536 In humans walking 30 minutes on a treadmill at their individual anaerobic thresholds, mRNA for HSP-70 rose but not the HSP-70 protein itself. That is, a single bout of exercise in humans may not be sufficient to induce HSP70 protein.416 Combined stressors may be additive or synergistic in their effects. Exposure of cells to either a moderately elevated tem-

Age. In normal adult rats, heat and exercise can each induce HSP-72. However, in aged rats, only exercise could induce HSP72.314 That is, aging caused them to lose their ability to induce HSPs by heat. Among humans, older adults have lower levels of HSP-70 in their peripheral blood mononuclear cells (PBMCs) than do the young.116 This loss of HSP protection may in part account for increased susceptibility of the aged to classic heatstroke, as is seen in heat waves. Race. HSP production may be race related. In one study, heatinduced HSP levels were very intense in cells isolated from native Turkmen men living in Turkmenistan, the hot desert of middle Asia, but very weak in Russians living in moderate climatic regions of European Russia. At the same time, cells isolated from Turkmen men better survived heat stress.264 Not surprisingly, organisms living many generations in hot climates become better adapted to it over time. No large-scale systematic study of racial influences on HSPs has been reported. However, one report indicates a difference in basal and heat induced levels of HSP-70 between Europeans and nonEuropeans in South Africa, and it suggests that there may be different susceptibilities to stress and disease.55

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perature or to a low level of ethanol does not induce HSPs. However, when the two stresses were applied at the same time, the cells induced large amounts of HSPs. Thus hyperthermia and ethanol acted synergistically to increase HSP gene expression.431 Practically, this implies that HSPs may be induced by overlapping periods of exercise, heat, hypoxia, and sleep deprivation.

Consequences of Elevated HSP-70. There is a downside to the production of HSPs during stress injury. While HSPs are being synthesized, the cell ceases or slows production of many other proteins. As a result, in cells at normal temperatures, synthesis of HSPs (induced by a short heat stress) retards cell growth,157 even as it protects against subsequent heat injury. Not only is growth retarded but heat-shocked immune cells secreted reduced amounts of cytokines in response to LPS.422 Therefore, persons with elevated HSPs may have reduced or inappropriately altered immune function. This was clear in immune gene activities shown in a recent genomics study.486 Clearly, the potential benefits of deliberately inducing HSPs, with presumed improved resistance to heat, hypoxia, and certain chemicals and toxins, must be weighed against a potentially decreased ability to resist infections.

Thyroid Hormone and Protein Isoforms Thyroid gland function is an important component of heat acclimation. IL-1 inhibits release of thyroid hormone from the thyroid gland.113,138 Because IL-1 becomes elevated in response to heat and many other stresses (see Figure 10-5),182 its ability to inhibit thyroid hormone release may be part of the overall protective mechanisms and responses to stress.278 A reduction in thyroid hormone concentration has a number of biochemical and physiologic consequences. Deficiency of thyroid hormone has a negative cardiac chronotropic effect, reducing cardiac contractility and increasing systemic vascular resistance.66 Basal metabolic rate (BMR) falls with thyroxine deficiency, and because its secretion rate is lower in summer and higher in winter, there is corresponding seasonal alteration in BMR and all other processes influenced by thyroxine concentrations.245 One component of heat acclimatization is reduction in BMR.245 Chronic heat stress decreases blood flow to the thyroid gland217 and reduces the rate of thyroid hormone production, leading to decreased food intake, growth rate, oxygen consumption, and BMR.435 Deficiency in thyroid hormone during acute stress may be fatal. A young woman was discovered unconscious in a sauna and later died with a diagnosis of heatstroke. On autopsy, she was found to have preexisting Hashimoto’s thyroiditis.473 Muscle contains characteristic isoforms of myosin, each with different intrinsic metabolic activities, such as the rate of its actin-activated ATPases. Myosin molecules are composed of heavy and light subunits that associate in a specific manner, each of which is specific to muscle type during development and maturation; that is, ventricular myosin in a fetal heart is different from that of an adult heart.89 In some muscles, acclimation leads to a higher proportion of “slow” myosin ATPase isoforms, such as the replacement of myosin heavy chain type IIb (MHCIIb) with type Iix.133,250 The hearts of heat-acclimated rats become more efficient (amount of oxygen required per unit force time per gram of tissue)246 as a result of the presence of altered isoforms of contractile proteins. Thirty to 90 minutes of daily exercise for 10 weeks reduced the percentage of MHCIIb fibers in

rat hind-limb muscles and increased the slower, but more efficient, MHCIIa fibers. That is, increasing the training duration increases the fast-to-slow shift in myosin isoforms.121 Excess thyroid hormone increases the amount of myosin isozyme VI, with its high rate of ATPase and contractile speed, at the expense of the normal V3 isozyme, leading to greater speed and strength but reduced efficiency. In the case of sweat secretion, on acclimation there is an intrinsically higher rate of sweat secretion because of isoform alterations along the secretory tubules. Administration of thyroid hormone to neonatal rats rapidly replaces fetal cardiac ventricular myosin with its adult isoform. On the other hand, if the synthesis of thyroid hormone is suppressed, then the slower, fetal isoform predominates.66 Thyroid hormone concentration regulates protein isoforms, activities, and therefore the output of metabolic heat.253 The speed and extent of contractility of heart muscle depend on the number of Ca release channels in the sarcoplasmic reticulum (SR) (more channels permit faster Ca2+ entry into the cytoplasm and faster contraction) and on the rate of Ca uptake by the SR (faster Ca2+ uptake means faster relaxation). In ventricles, low thyroid hormone levels reduce the number of Ca release channels, which depresses contractility. In the atria, low thyroid hormone also increases the density of muscarinic receptors, rendering them more sensitive to negative chronotropic agents. In summary, low thyroid hormone levels depress cardiac function and render the heart more sensitive to agents that decrease atrial contraction, and less sensitive to agents that increase HR and contraction.15,295,312,432 Acclimation occurs under conditions of relative or actual hypothyroidism. As a result, the acclimated heart shows altered myosin isoforms and increased phospholamban content but lowered contractile velocity, rate of Ca uptake by the SR, and relative oxygen consumption. These changes increase overall efficiency of the heart at the expense of contractile velocity.79,360 Thyroid hormone increases the number of Na+,K+-ATPase pumps97 and decreases the density of voltage-dependent calcium channels on plasma membranes (leading to reduced intracellular Ca2+ content).159 Thyroid hormone and sustained aldosterone, such as from excess sweat loss and elevated plasma Na+, also alter metabolic processes and electrical activity of cells by regulating intracellular Na+ and K+ concentrations. In the short term, they increase the number of functional Na+,K+-ATPase pumps by recruiting preformed but inactive pumps and their subunits to the plasma membrane. In the long term, they induce synthesis of new pump subunits.97,155 Therefore, the prolonged and reduced levels of thyroid hormone seen during acclimatization decrease the number of those pumps, hence reducing metabolic activity.463 Almost any traumatic insult to the body alters hormonal level by elevating corticotropin releasing hormone, in turn decreasing thyroid hormone, growth hormone (GH), gonadotropinreleasing hormone, luteinizing hormone, follicle-stimulating hormone, and gonadal steroid concentrations, while increasing ACTH, cortisol, and prolactin levels (see Figure 10-5).46 Reduction in thyroid hormone concentration commences within a few hours, may be maximal after 1 to 4 days, and persists for the duration of the illness.338 Among heatstroke victims, decreases in serum thyroid hormone correlated with severity of heatstroke, according to peak Tc.91 That is, severity of heatstroke was related to depression of thyroid function. After the patients

Chapter 10: Pathophysiology of Heat-Related Illnesses completely recovered, thyroid function tests returned to normal. The hypothyroid state may protect by preventing undesirable catabolic effects. Therefore, thyroid replacement therapy is not currently recommended.91 In summary, long-term acclimatization to heat and exercise involves changes on a molecular level, involving alterations in intracellular HSP concentrations, increased IL-1, reduced thyroid hormone, increased aldosterone, increased number of Na+,K+-ATPase membrane pumps, and alterations in protein isoforms, altogether contributing to the physiologic adaptations in organ function.246


IMMUNE SYSTEM In the processes of digestion and absorption of ingested food, chyme remains in the intestines for hours to days. Although we absorb a large share of the nutrients, bacteria present in the gut lumen also utilize nutrients from the chyme and reproduce rapidly, reaching concentrations of 109 to 1012 organisms per gram.168 Dead gram-negative bacteria slough off into their milieu large amounts of the highly toxic cell wall component LPS, which may reach concentrations of 1 mg/g in the feces, a million times the lethal concentration if it were in plasma. As long as LPS remains within the intestines, it is not harmful. Small amounts that leak into the circulation are rapidly inactivated by several mechanisms. Some LPS is phagocytosed by bound Kupffer cells within the liver reticuloendothelial system (RES), where it is partly detoxified and then bound by hepatocytes for further degrading509; some LPS binds to circulating antilipopolysaccharide antibodies176; some binds to high-density lipoprotein (HDL)513; and some binds to LPS-binding protein (LBP).544 If large amounts of LPS rapidly enter the circulation, it could overwhelm the protective systems, allowing LPS to express its toxic effects rapidly. At plasma concentrations between approximately 10 and 100 pg/mL, LPS initiates a cascade of molecular events, leading to nausea, vomiting, diarrhea, fever, and headache.44 Higher concentrations can lead to conditions identical to those of gram-negative bacteremia, including vascular collapse, shock, and death.80 In fact, during gram-negative bacteremia, normal immune mechanisms may destroy all viable circulating bacteria so that at the time of death there may be zero live bacteria in the plasma. The circulating LPS appears to be the immediate cause of septic shock.534

Intestinal Ischemia and Lipopolysaccharide Release During exercise, blood flow to muscle may rise from a resting value of 1 to 2 mL/100 g/min to as high as 300 mL/100 g/min to deliver oxygen and nutrients. As Tc rises, blood flow to the skin also rises to provide cooling. This strains the cardiovascular system’s ability to maintain blood flow to the heart, brain, and liver.304,350 During heavy exercise, it is important that blood flow to the liver be substantially maintained to remove lactate and other metabolites from the blood and to provide glucose for energy.304 To maintain blood pressure under still more intense exercise and thermal stress, blood flow is reduced to those organs less immediately critical—that is, the intestines and kidneys. If splanchnic blood flow drops sufficiently, reduced delivery of oxygen leads to regions of local ischemia and transitory damage

257

to the barrier function of the gut wall. If this is prolonged, there may be permanent ischemic injury to the gut wall.415,418 Occurrence of several transitory bouts of local hypoxia and metabolic stress in splanchnic tissues may, during reperfusion, generate free radicals, exacerbating the ischemic injury.221 Exercise at . 80% Vo2max for 30 minutes at 22° C (71° F) increased permeability of human intestines to small molecules.401 Ischemic injury of the intestines causes the diarrhea or water intoxication occasionally encountered during a marathon run as a consequence of the inability to reabsorb water ingested during the race.304 For example, in one extreme case, after winning a marathon in 1979, Derek Clayton stated that “two hours later . . . I was urinating quite large clots of blood, and I was vomiting black mucus and had a lot of black diarrhea.”166 Another athlete, Dr. Peter Rogers, stated that during training for two Olympiads (gymnastics, 1972, 1976) and one world championship, many of the athletes developed bloody diarrhea after long periods of intense training (personal communication, 2005). Intense and prolonged running is a common cause of gastrointestinal bleeding; up to 85% of ultramarathoners demonstrate guaiacpositive stools from a 100-km (62.1-mile) race.29 Endotoxemia, the ultimate consequences of reduced intestinal blood flow, may be severe. Because of the high LPS gradient across the gut wall, almost any insult to the integrity of the gut wall leads to a rise in plasma LPS. Severe hemorrhage reduces splanchnic blood flow and oxygen delivery to the walls of the stomach, small intestine, and sigmoid colon.128 This has led to local elevations in the permeability barrier of the gut wall and caused endotoxemia.181 In a swine model, blood flow through the superior mesenteric artery was progressively occluded, leading to progressive tissue hypoxia and a local shift to anaerobic metabolism, producing lactate and a fall in the pH of the gut wall.162 At about the same time, LPS entered the circulation. This may lead to an ominous positive-feedback loop, because infusing LPS itself causes hypotension, reduced splanchnic blood flow, and an increase in gut permeability so severe that whole bacteria can be translocated into the circulation.162,529 The size of putative holes in the gut wall accounting for the rise in LPS permeability depends on the duration of the ischemia. When the superior mesenteric artery of canines was occluded, LPS (molecular or micellar) leaked out into the circulation within 20 minutes, but whole live bacteria (several orders of magnitude larger) required 6 hours of occlusion.406 In other species, these times may be much shorter.117 In a different model, nonhuman primates breathed a hypoxic gas mixture for an hour.17 The resultant hypoxemia rapidly initiated a reflex response designed to maintain oxygenation of the heart and brain at the expense of the rest of the body. This reflex caused intestinal blood flow to fall and was so intense that it resulted in transient ischemic injury to the gut wall and translocation of LPS into the circulation within only 5 to 10 minutes of breathing the hypoxic gas mixture. When the immune system was suppressed by whole-body ionizing radiation, the same hypoxic stress caused LPS to rise to higher levels and persist in the blood for a longer period. On the other hand, when the gut flora had been reduced three to four orders of magnitude by administration of nonabsorbable antibiotics for a week, there was no detectable translocation of LPS and bacteria by hypoxia.117,168 There is a fitness component to alterations in splanchnic blood flow. When experimental animals (as compared with

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30 Anti-LPS 20 LPS (ng/mL)

0.3

Hep. portal v. 10

Femoral a. 0.2 Hep. portal v.

0

LPS

0.1

Femoral a. 0 37

38

39

40

41

42

43

44

Rectal temperature (°C)

Figure 10-13. Effect of heating on villus structure. Representative light micrographs of rat small intestinal tissue over a 60-minute course at 41.5° to 42° C. Note the generally normal appearing villi at 15 minutes (slight subepithelial space at villous tips), compared with initial sloughing of epithelia from villous tips at 30 minutes, massive lifting of epithelial lining at top and sides of villi at 45 minutes, and completely denuded villi at 60 minutes. Bars represent 100 µM. (From Lambert GP, Gisolfi CV, Berg DJ, et al: J Appl Physiol 92:1750–1761, 2002, with permission.)

sedentary animals) were heat stressed, the fit ones with their greater cardiovascular capacity better maintained BFspl, they had reduced amounts of ischemic damage to the gut wall, and reduced quantities of LPS translocated into the circulation.444 That is, fitness may reduce the LPS load during intense exercise. Such studies show that the permeability barrier in the gut wall is rapidly damaged by hypotension, reduced blood flow, and hypoxia, thus permitting LPS to enter the portal and systemic circulations at a high rate. It has been reported that after heatstroke patients are cooled, they may develop secondary fever and infection carrying a high death rate.470 The susceptibility of such patients to infections470 may result from a combination of changes in lymphocyte subpopulations, together with the increase in gut wall permeability to LPS and bacteria caused by hyperthermia and associated hypotension.117

Role of Lipopolysaccharide in Heatstroke Pathophysiology Heatstroke temperatures greater than 43° C (109.4° F) cause a large increase in permeability of isolated rat intestinal walls to LPS that persists even after the temperature is reduced to 37° C (98.6° F).384 This suggests that heat causes major direct thermal injury of the gut wall at approximately 42° to 43° C (107.6° to 109.4° F) (Fig. 10-13).318 The time course of the movement of LPS through the intestinal wall into the circulation resulting from hypoxia, ischemia, and ionizing radiation was determined in nonhuman primates125 and compared with hyperthermia (Tamb = 41° C [105.8° F], RH = 100%, 3 to 4 hours).327 As Tc rose, plasma LPS concentration remained low until 42° to 43° C (107.6° to 109.4° F) (Fig. 10-14). At this temperature, there was a sudden rise in LPS concentration, first in the portal

Figure 10-14. Endotoxemia caused by heatstroke in anesthetized nonhuman primates. At Tre of 42° to 43° C (107.6° to 109.4° F), plasma lipopolysaccharide (LPS) concentration rose first in the hepatic portal vein,and 10 to 15 minutes later in the systemic circulation.However,a decline in consumed anti-LPS antibodies occurred at temperatures as low as 39° to 40° C (102.2° to 104° F). (Modified from Gathiram P, Wells MT, Brock-Utne JG, Gaffin SL: Circ Shock 25:223–230, 1988, with permission.)

vein, and 10 to 15 minutes later in the systemic circulation. This sequence appears to be the main route of LPS: out of the lumen of the intestines, through the portal vein to the liver, and into the vena cava and systemic circulation as a result of heatstroke and intestinal ischemia.192 In a previous study of infection by injecting live gramnegative bacteria, Gaffin and coworkers534 noted that when the concentration of live gram-negative bacteria or LPS rose, the concentration of measurable circulating LPS-specific antibodies fell because they became bound to circulating LPS and thus were no longer detectable by an immunoassay.534 It had been expected therefore that in the heatstroke experiments, the concentration of natural (i.e., background) anti-LPS antibodies would also immediately fall at 42° to 43° C (107.6° to 109.4° F). Contrary to expectations, natural anti-LPS began to decline at temperatures as low as 39° to 40° C (102.2° to 104° F) (see Figure 10-14).192 This suggests that as Tc rose to only 39° to 40° C, LPS actually began to leak into the circulation at a slow rate, gradually consuming the anti-LPS antibodies. As Tc continued to rise, at a certain point massive damage to the gut wall occurred, leading to rapid leakage of LPS into the portal vein. It is not clear how much of this damage is caused by reduced oxygen delivery from reduced intestinal blood flow, how much by direct thermal damage of the gut wall, and how much by other causes. Anti-LPS antibodies were protective against heatstroke in vervet monkeys up to a Tc of 43.5° C (110.3° F), but no higher.191 This suggests that LPS-induced toxicity is important in the pathophysiology of heatstroke death only up to 43.5° C (108.5° F). Above this temperature, other mechanisms are more important, such as direct thermal damage to nervous tissue. LPS had previously been implicated as a factor in heatstroke death by indirect observations. Injection of very low doses of LPS leads to rapid tolerance to ordinarily lethal doses of LPS.136,208 Administration of low doses of LPS protected rats against subsequent heatstroke. When activity of the reticuloen-

Chapter 10: Pathophysiology of Heat-Related Illnesses dothelial system (the main mechanism for removal of LPS from the circulation) was reduced, the mortality of heatstroke increased.137 Ryan and colleagues441 found the inverse effect. Rats were heated to a Tc of 42.5° C (108.5° F) and then were passively cooled. The next day they were challenged with a lethal dose of LPS, and mortality rate dropped from 71% in the control rats to zero in the previously heat-stressed rats. The importance of LPS in fatal heatstroke death was confirmed in a canine model of heatstroke.232 Tc was raised to 42° C (107.6° F) for 3 hours and then cooled to 38° C (100.4° F). Deaths occurred only in the animals with rises in plasma LPS concentration.

Exertional Heatstroke Several studies support the idea that the immune system and LPS are involved in the pathophysiology of heatstroke. Leukocytosis is a general response to most forms of stress, including muscular activity,190 administration of epinephrine or glucocorticoid, and excitement. Prolonged or severe exercise initiates mobilization and activation of neutrophils and causes proteolysis of skeletal muscle and production of acute phase proteins by the liver.76 Exercise leads to local disruption of tissues and sloughing of tissue fragments that circulate and activate the complement system. This activation primes monocytes for further activation by LPS or by fragments of tissue subsequently damaged.78 Severe exercise causes reduction in splanchnic blood flow and impaired renal function, with an increase in urinary excretion of proteins so profound (>100-fold) that it led to an actual depletion of circulating proteins.33,415 To understand the relationship between splanchnic shutdown and heatstroke pathophysiology, it is necessary to consider the contents of the intestinal lumen and the likely results of their leakage into the systemic circulation. Many of the clinical signs in a heatstroke victim, including blood-clotting disturbances, are similar to those seen in septic shock cases.202 LPS activates a blood factor leading to disseminated intravascular coagulation,39,555 a common complication of septic shock. It was suggested that LPS participates in the pathophysiology of heatstroke. Similarities between heatstroke and septic shock are described in Box 10-5. Because core temperatures of long-distance runners may rise above 40° C (104° F), a study of runners who collapsed during an ultramarathon (89.5 km [55.6 mi]) run on a warm day was conducted.68 Those runners reached or were carried into the medical tent at the finish line, where blood samples were taken from 98 of them before initiating volume therapy (Fig. 10-15). Eighty of 98 runners had plasma LPS levels above normal values, including two in the lethal range. It should be noted that the body can tolerate short periods of high LPS concentrations.534 Although hypovolemia and hemoconcentration resulting from sweating may have caused a few high normals to cross into the elevated range, this was not the case for the majority. Of those who finished the race, the smaller group with normal, low LPS levels finished faster. Furthermore, this normal group had higher levels of natural anti-LPS in their plasma. That is, the presence of high levels of anti-LPS antibodies correlated with low levels of LPS and better performance. This high antiLPS antibody and low LPS group also had reduced indexes of nausea, vomiting, and headache and recovered faster (within 2 hours) than did the larger high-LPS and low-anti-LPS group (up to 2 days).

259

Box 10-5. Common Factors in Heat Illnesses and Sepsis CLINICAL

Neurologic symptoms Fatigue, weakness, confusion, delirium, stupor, coma, dizziness, paralysis, amnesia Tachycardia Nausea, vomiting, diarrhea Headache Myalgia Hypotension Spasm, rigors Oliguria, renal failure Hyperventilation Organ failure Shock LABORATORY

Metabolic acidosis Hematocrit elevated Urea elevated Lactate elevated Disseminated intravascular coagulation Cytokines elevated Hepatic dysfunction Lipopolysaccharides elevated

In triathlon participants, concentrations of LPS rose and of anti-LPS antibodies fell at the end of the third race.54 Some athletes were found to have higher levels of natural anti-LPS antibodies than others. When individuals were questioned about their training regimen, it became clear that those who trained the hardest (miles swum, bicycled, and run the 3 weeks before the triathlon) had the highest levels of anti-LPS antibodies. It may be that one component of the benefit of physical training is increased levels of natural anti-LPS antibodies. We proposed that as a result of severe training, temporary periods of intestinal ischemia occurred, leading to entry of low to moderate levels of LPS into the circulation, which was enough to stimulate the immune system and induce anti-LPS antibodies. When a marathon was run on a cold day, no elevations in plasma LPS were seen (T. Noakes and S. Gaffin, 1988, unpublished observations). It is not clear what combinations of heat load and exertional factors are required to decrease BFspl sufficiently to damage the gut wall for translocation of LPS into the circulation.

Classic Heatstroke Survival of hospitalized heatstroke patients depends in large part on the rapidity of cooling on entry to a hospital intensive care unit. This time factor may be important because of the time required for the production of cytokines, which is in the range of minutes to hours. Seventeen Hadj patients with classic (nonexertional) heatstroke were admitted to a hospital an average of 2 hours after the onset of heatstroke.59 Each victim’s Tc was greater than 40.1° C (104.2° F). They suffered from delirium, convulsions, and coma. Plasma LPS concentrations ranged from 8 to 12 ng/mL, extremely high and in the potentially lethal range.524 Furthermore, TNF and IL-1 concentrations were also

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0.4

TABLE 10-3. Elevated Cytokines Due to Heatstroke in 17 Military Recruits Who Developed Exertional Heatstroke*

Plasma LPS (ng/mL)

P⬍0.025

EXERTIONAL HEAT STROKED

0.3 Rectal temperature‡ IL-1β‡ TNF-α‡ IL-6‡ IFN-γ‡ IL-2r‡ IL-4 IL-10 IL-8‡ Monocyte chemoattractant protein 1‡ RANTES‡

0.2

0.1

0 ⬍8

⬎8

Time to completion of race (h) Plasma LPS Nausea, vomiting, diarrhea 100 80

0.3

60 0.2 40

N, V, D (%)

Plasma LPS (ng/mL)

0.4

0.1 20 0

0 0.1 ng/mL normal

⬎0.1 ng/mL high

Plasma LPS (ng/mL)

Figure 10-15. Role of lipopolysaccharide (LPS) and anti-LPS IgG in long-distance races. The Comrades’ Marathon is an 89.5-km race between Pietermaritzburg and Durban, Republic of South Africa, run on a warm day. Blood samples were obtained from collapsed runners prior to treatment. On examination, they all looked the same. However, of 89 samples analyzed, 80% had elevated levels (>0.1 ng/mL) of LPS, and 20% had normal low levels. Top: Those with low levels of circulating LPS ran the double marathon significantly faster before they collapsed. Bottom: Those with low levels of circulating LPS had higher morbidity indexes of nausea,vomiting, and diarrhea and all recovered within 2 hours.Those with elevated levels of LPS had more serious symptoms and required up to two days to recover.(Redrawn from Brock-Utne JG, Gaffin SL,Wells MT, et al: S Afr Med J 73:533–536, 1988.)

41.2 (99.7 3.1 4.9 15.8 7.3 1568 2.5 12.9 84.2 959

± ± ± ± ± ± ± ± ± ± ±

1.2° C 1.4° F) 1.5 pg/mL 4.1 pg/mL 3.2 pg/mL 4.9 pg/mL 643 pg/mL 1.2 pg/mL 9.4 pg/mL 79.9 pg/mL 589 pg/mL

12,464 ± 10,505 pg/mL

CONTROLS† 37.6 (106.2 1.2 1.2 1.2 2.4 610 1.2 2.5 10.4 158

± ± ± ± ± ± ± ± ± ± ±

0.8° C 2.1° F) 0.8 pg/mL 2.4 pg/mL 1.2 pg/mL 4.1 pg/mL 214 pg/mL 0.8 pg/mL 4.9 pg/mL 3.2 pg/mL 217 pg/mL

5570 ± 2894 pg/mL

*The severity of exertional heatstroke was evaluated using a simplified acute physiology (SAP) score. Interleukin (IL)-6, interferon-gamma (IFN)-γ, and IL-2 receptor positively correlated with the SAP score. Among chemokines, only serum monocyte chemoattractant protein 1 was positively correlated with the SAP score (r = .78, P < .001). There was no correlation between either cytokines or chemokines and body temperature. † Controls were 17 military recruits undergoing exercise who did not develop heatstroke. ‡ Conclusions: Proinflammatory cytokines IL-1β, tumor necrosis factor (TNF)-α, IL-6; Th1 cytokines INF-γ and IL-2 receptor; and chemokines IL-8, monocyte chemoattractant protein 1, and RANTES (regulated on activation, normal T cell expressed and secreted) are increased in patients with exertional heatstroke. Helper T-2 cytokines may play a role as anti-inflammatory cytokines. From Lu KC, Wang JY, Lin SH, et al: Crit Care Med 32:399–403, 2004.

cytosis increased with increasing Tc. There were also substantial decreases in helper T cells (CD4) and B cells (CD19) as a result of heatstroke. Heatstroke is known to elevate catecholamine levels.84 Because epinephrine causes leukocytosis with an increase in NK and T suppressor/cytotoxic cells, these authors suggested that heatstroke raised catecholamines, which in turn altered lymphocyte subpopulations. On the other hand, hyperthermia causes elevated cortisol,276 which causes the opposite effect, lymphocytopenia.58 In the preceding study, two of the 11 heatstroke patients had a decreased number of lymphocytes. To account for the reduction in lymphocytes, the authors suggested that in those two patients the effects of cortisol, rather than of catecholamines, were dominant. That is, changes in subpopulations of lymphocytes in heatstroke may depend (on an individual basis) on the relative rises in concentration of catecholamines and cortisol, as well as on individual sensitivities to them. However, this is not yet clearly established.

Adaptation and the Immune System Cytokines and Shock

very high. The authors suggested that these cytokines exacerbated the hyperthermia of heatstroke through induction of prostaglandins. Nine of 11 heatstroke patients showed marked leukocytosis resulting from a large increase in the number of T suppressor cytotoxic cells (CD8) and NK cells (CD16/CD56).58 This leuko-

Cytokines are a class of protein cell regulators produced by a wide variety of cell types throughout the body. They control timing, amplitude, and duration of the immune response.99 They are relatively low molecular weight proteins (40° C [104° F]) that it should be considered a subgroup of EHS. Neuroleptic seizures and overdose of recreational drugs share with EHS the features of massive muscle contractions (with consequent overuse of high-energy compounds) and rhabdomyolysis.303 Because the use of recreational drugs is not expected to decline and the number of persons using neuroleptic drugs is probably on the increase, the involvement of heatstroke pathophysiology should be considered in treating those cases. In an unusual situation during mountaineering in summer, two persons died of heatstroke and acute rhabdomyolysis. Both patients had received treatment with antipsychotic drugs, including a phenothiazine.306 Ergogenic aids are also a problem. A highly trained, heat-acclimatized infantry soldier suffered from exertional heatstroke during a 12-mile road march shortly after taking an ephedra-based supplement. Because there are no clear ergogenic benefits in using ephedra alone, clinicians and military commanders should strongly discourage the use of ephedra-containing substances in active duty soldiers undergoing strenuous exercise.395 In summary, heatstroke in a summertime vacation area might be complicated by the use of therapeutic or recreational drugs or ergogenic aids.

Malignant Hyperthermia Malignant hyperthermia is a rare life-threatening disorder involving hypermetabolism, rapid rise in body temperature, and rigidity of skeletal muscle. It is induced by exposure to volatile anesthetics during surgical procedures in affected patients. In about half these patients, mutations were seen in the gene for the Ca2+ release channel (RyR).107,213,323 The anesthetic binds to RyR and activates the Ca2+ release channel, causing massive calcium entry into the cytoplasm. This activates contractile proteins, calmodulin, and a variety of calcium-sensitive enzymes, which leads to muscle rigidity, hypercatabolism, fulminating hyperthermia, and metabolic acidosis.107 Rhabdomyolysis, hyperkalemia, and myoglobinemia458 are commonly associated with malignant hyperthermia, with plasma K+ rising as high as 10 mmol/L.357 Underlying illnesses in five cases of rhabdomyolysis included heatstroke, high fever, and grand mal seizures with associated hyperthermia. Nevertheless, there were multiple factors responsible for rhabdomyolysis in each case, such as hypokalemia, hypophosphatemia, shock, and arteriosclerosis.378 A 41-year-old man susceptible to malignant hyperthermia developed an infection and selfmedicated with a cold medicine. He presented with high fever, dysarthria, dysphagia, and progressive weakness of his muscles and developed massive rhabdomyolysis with acute renal failure.279

Neuroleptic Seizure Treatment of psychiatric patients with neuroleptic drugs, as well as with antidepressants, antiemetics, and others,141 may lead to

Chapter 10: Pathophysiology of Heat-Related Illnesses the uncommon but often fatal neuroleptic malignant syndrome, characterized by hyperthermia as high as 42° C (107.6° F), “lead pipe” (skeletal muscle) rigidity, dyspnea, coma, extrapyramidal syndrome, rhabdomyolysis, severe metabolic acidosis, leukocytosis, and elevated creatine kinase.104,234,270 A number of factors predispose to neuroleptic seizure, including dehydration, exhaustion, aggression, and restraints265; high environmental temperature; high doses of neuroleptics; abrupt discontinuation of antiparkinsonism agents; and administration of lithium.141 Successful treatment of these cases includes immediate withdrawal of the drug, administration of dantrolene, and either oral bromocriptine or the combination of levodopa and carbidopa.141

Drug Overdose Although the toxicity of drug overdose is well recognized, it is not often appreciated that the hyperthermia attained can be in the range reported for heatstroke. Such hyperthermia has been induced with cocaine130 and amphetamine derivatives, such as 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy) and 3,4-methylenedioxyethamphetamine (MDEA, Eve).504 Other components of this syndrome include hyperkalemia, rhabdomyolysis,475 sympathetic hyperactivity, convulsions, rectorrhagia, psychosis, disseminated intravascular coagulation in the absence of positive blood cultures, and acute renal failure.237

Susceptibility to Heatstroke There may be an inherited susceptibility to EHS. Muscle biopsy specimens taken from two men in military service who had recovered from EHS had abnormal responses to halothane, a well-known cause of malignant hyperthermia.213 Furthermore, muscles from members of their families had abnormal responses to halothane or ryanodine, a drug that binds to the Ca2+ release channels of the sarcoplasmic reticulum.8 A ryanodine contracture test has been proposed as an in vitro diagnostic test to screen for surgical patients susceptible to malignant hyperthermia.8 This test might be useful in identifying, retrospectively, a possible subgroup of patients with EHS.

Changes in Cognitive Function Changes in cognitive function appear to occur before development of physical symptoms associated with heat stress.82 Typically, heat stress causes distortion of the sense of time,36,37,112 memory impairment,540 deterioration in attention, and decreased ability to calculate mathematical problems.92,209,539 Health care personnel should be trained to recognize that confusion, changes in affect, and impaired ability to function in the work environment can be early signs of heat injury under heat stress conditions.82

Vasovagal Syncope Syncope is the cause of about 3% of emergency department visits and 6% of hospital admissions.193 Vasovagal syncope is responsible for 28% to 38% of syncopal episodes in patients 35 to 39 years old.115,274,348 Benign presyncope or syncope may result from diminished venous return to the heart because of blood pooling in the peripheral circulation. Syncope encompasses psychological disturbances activating an autonomic vasodilation response; reflex syncope caused by heavy coughing, micturition, or pressure on an irritable carotid sinus; and reduced vasomotor tone caused by hypotensive drugs or alcohol.144

263

The frequency of vasovagal syncope is greater in the young than in older adults, whereas orthostatic hypotension is more common in older persons.334 Propranolol does not prevent the vasovagal reaction in response to head-up tilt.334 Therefore, after the age of 40, presyncope may suggest a more serious condition, such as gastrointestinal bleeding, myocardial or valvular heart disease, or severe anemia. Cardiovascular syncope resulting from arrhythmia carries a 1-year mortality rate of about 30%.275

Hyperventilation Dizziness A slight but prolonged increase in respiratory rate or tidal volume may accompany an increase in anxiety.144 This can lead to increased blood oxygen content and decreased Pco2, with accompanying alkalosis. Altogether, these lead to generalized cerebrovascular vasoconstriction with ischemia and dizziness.

Heat-Induced Syncope The associated clinical syndromes vary in severity depending on the cause of hyperthermia and, therefore, so does the duration of central nervous system (CNS) dysfunction. Transient or temporary loss of consciousness associated with a mild form of heat syncope has its origins primarily in the cardiovascular system. It is a consequence of a reduced effective blood volume rather than an actual loss of volume. In an upright and stationary person, blood volume is displaced into the dependent limbs by gravity. If that person is also heat stressed, more blood is displaced into the peripheral circulation to support heat transfer at the body surface. These combined reductions in effective blood volume can temporarily compromise venous return, cardiac output, and cerebral perfusion. Patients are usually erect at the outset and sometimes report prodromal symptoms of restlessness, nausea, sighing, yawning, and dysphoria.293 Hypotension results predominantly from vasodilation and bradycardia. This systemic disorder is self-limited because when the person faints and assumes a horizontal position, central blood volume is restored, cardiac filling rises, blood pressure is restored, and the problem is remedied. Transient loss of consciousness in syncope has a metabolic basis within ischemic cells of the brain. Despite this, the effects, although startling to onlookers and frightening to the patient, appear to be readily reversible. There is no risk of direct thermal injury to brain cells complicating the circulatory origin of this sudden decline in effective arterial volume. The incidence of syncopal attacks falls rapidly with increasing days of work in the heat (see Figure 10-10), suggesting the importance of salt and water retention in preventing this disorder (Table 10-4). Individuals medicated with diuretics would be at high risk. Furthermore, potassium depletion and hypokalemia may lower blood pressure and blunt cardiovascular responsiveness.305 In stark contrast to simple syncope is the profound CNS dysfunction dominating the early course of heatstroke. Thus, if a person faints in a setting where hyperthermia is possible and does not rapidly return to consciousness, heatstroke should be suspected, cooling measures instituted, and body temperature monitored.

Exertion-Induced Syncope, Cramps, and Respiratory Alkalosis During basic military training, a cluster of 17 syncopal episodes was associated with a seldom-described form of heat exhaus-

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TABLE 10-4. Signs and Symptoms of Salt and Water Depletion Heat Exhaustion SIGNS AND SYMPTOMS Recent weight gain Thirst Muscle cramps Nausea Vomiting Muscle fatigue or weakness Loss of skin turgor Mental dullness, apathy Orthostatic rise in pulse rate Tachycardia Dry mucous membranes Increased rectal temperature Urine Na+/Cl− Plasma Na+/Cl−

SALT DEPLETION HEAT EXHAUSTION

WATER DEPLETION HEAT EXHAUSTION

DILUTIONAL HYPONATREMIA

No Not prominent In most cases Yes In most cases Yes Yes Yes Yes Yes Yes Yes Negligible Below average

No Yes No Yes No Yes Yes Yes Yes Yes Yes In most cases Normal Above average

Yes Sometimes Sometimes Usually Usually No No Yes No No No No Low Below average

*Data from Armstrong LE, Curtis WC, Hubbard RW, et al: Med Sci Sports Exerc 25:543–549, 1993; Shopes E: Water intoxication: Experience from the Grand Canyon (abstract). Presented at the 10th Annual Meeting of the Wilderness Medical Society, August 1994, Squaw Valley, Idaho, p 265.

TABLE 10-5. Clinical Data for 17 Patients with Heat Exhaustion CASE NO. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

AGE

Activity

SYNCOPE

CRAMPS

Tre (°F)

RR (bpm)

Na+ (mEq/L)

pH

Pco2 (mmHg)

19 20 20 21 21 22 20 20 20 18 19 18 20 19 23 18 17

Marching Running mile Rifle range Marching/running Marching Marching Rifle range Marching Marching Marching Marching Marching Marching Marching Rifle range Marching Marching

Yes Yes No Yes No No No Yes No Yes Yes Yes No Yes Yes Yes Yes

Abd Legs/abd No Hands Severe abd/legs Legs Mild Abd/legs Abd Chest Tetany Severe Mild Abd/legs Abd/legs Chest/legs Abd

99.6 98.4 99.4 100.4 102.4 100.0 100.0 100.8 101.4 100.8 101.5 100.6 98.6 100.7 101.0 101.2 101.6

24 30 24 22 35 22 22 30 24 18 30 30 26 30 32 28 22

142 145 143 162 141 152 140 145 — 140 160 130 141 145 148 148 146

— — — 7.47 7.50 7.70 — 7.52 7.69 7.56 7.44 7.71 7.77 7.76 7.66 7.78 7.53

— — — 34.0 32.4 14.8 — 28.8 19.8 29.4 34.2 17.2 15.2 16.3 19.7 14.7 28.4

Abd, abdomen; RR, respiratory rate; Tre, rectal temperature. From Boyd AE, Beller GA: Acid-base changes in heat exhaustion during basic training. Proc Army Sci Conf 1:114, 1972.

tion (Table 10-5).260 This heat exhaustion, in contrast to hypovolemic salt depletion, was characterized by hyperventilation, respiratory alkalosis, syncope, and tetany. Most victims also experienced abdominal cramps, yet this was independent of lactic acidosis and hyponatremia. These descriptions were unique in that the heat syncope episodes were not those classically described as the venous pooling or postural hypotension variety.32,387 The incapacitated trainees arrived at a heat ward within 10 to 30 minutes of the onset of symptoms, and blood samples were drawn immediately on admission. They exhibited moderate to marked respiratory alkalosis, but only two appeared to be severely dehydrated; nearly all (16 of 17 patients) had severe cramps of the abdominal or extremity muscles.

Clinical data recorded on admission are shown in Table 10-5. Almost all the casualties occurred in the afternoon during July, 1971, at Fort Polk, Louisiana. All were diagnosed with heat exhaustion resulting from training in the field (12 of 17 while speed marching). Rectal temperatures on admission were elevated, even though most of the victims had been doused with water before evacuation from the field. Serum electrolytes were in the normal range in the majority of victims. However, hemoconcentration with elevated serum sodium level was observed in four patients. One of 17 patients had a low serum sodium level and also experienced severe muscle cramps. The majority of these patients were not water or salt depleted, and 15 of the 16 remaining patients with cramps had normal to elevated serum sodium and chloride levels. The mean arte-

Chapter 10: Pathophysiology of Heat-Related Illnesses

265

TABLE 10-6. Protective Effect of Hypertonic 10% Albumin versus Saline on Experimental Heatstroke-Induced Cerebral Ischemia-Hypoxia Injury in Amelioration of Rises in Glutamate, Glycerol, Lactate, and Free Radicals in Brain

Mean arterial pressure Intracranial pressure Cerebral perfusion pressure Cerebral blood flow Brain Po2 Striatal glutamate Striatal glycerol Striatal lactate/pyruvate ratio Striatal hydroxyl radicals Striatal neuronal damage score

SALINE

10% ALBUMIN

42 ± 3 mm Hg 33 ± 3 mm Hg 9 ± 3 mm Hg 109 ± 20 blood perfusion units 6 ± 1 mm Hg 51 ± 7 nM 24 ± 3 nM 124 ± 32 694 ± 22% rise 2.25 ± 0.05

64 ± 6 mm Hg 10 ± 2 mm Hg 54 ± 5 mm Hg 452 ± 75 blood perfusion units 15 ± 2 mm Hg 3 ± 2 nM 4 ± 2 nM 7±3 119 ± 7% rise 0.38 ± 0.05

Adapted from Chang CK, Chiu WT, Chang CP, Lin MT: Clin Sci (Lond) 106:501–509, 2004.

rial pH for this group of patients was 7.62 ± 0.03 (SEM), and five had a pH of 7.67 or greater. Arterial Pco2 was reduced to a mean value of 23.5 ± 2 mm Hg. Thus, all patients had moderate to marked respiratory alkalosis, and nine had obvious tetany with carpopedal spasm.64 The presence of carpopedal spasm and paresthesias in the distal extremities and perioral area helps distinguish this form of cramps from the classic variety. These data associate exertion-induced heat exhaustion with a form of respiratory alkalosis characterized by syncope, tetany, and muscle cramps and may possibly be the result of “an exaggeration of the normal physiologic ventilatory response to thermal extremes.”64 Hyperventilation with its resulting decrease in cerebral blood flow288,471,525 could account for a significant number of cases of exercise-induced heat syncope. Recumbency, rest, and oral replacement of fluid and electrolyte deficits are usual recommendations. Rebreathing of expired air is directed at alleviating carpopedal spasm, but it should be done with extreme caution because of its hypoxemic effect. Classic syncope is usually associated with postural hypotension, whereas heat exhaustion and heat cramps are usually associated with water and electrolyte imbalance. Most literature suggests that unacclimated workers have higher salt losses in the heat than those who are acclimated.317,325 Thus this series is a good example of the real world with a mixed bag of heat illness symptoms. To explain these clinical results, one should recall that acclimated individuals have higher sweat rates (2.5 L/hr versus 1.5 L/hr) than unacclimated persons, but they also have increased tolerance to exercise. If both groups voluntarily work at maximal sweat rates for any given task, those who are heat acclimated could produce higher salt losses despite their reduced sweat sodium concentrations. In such a scenario, the acclimated individuals would be predicted to be the more prone to heat cramps.10 However, Table 10-6 indicates that there are higher salt losses for unacclimated individuals at any given sweat rate or volume of sweat lost. The differential diagnosis of heat cramps should also include exercise-induced peritonitis.500

Heat-Induced Tetany In excessively hot environments, men at rest hyperventilate.216 Adolph and Fulton2 described dyspnea and tingling in the hands

and feet of men being dehydrated in the heat. In 1941, during a voyage through the intense heat of the Persian Gulf, a ship’s engineer was reported to experience spontaneous hyperventilation and attacks of tetany.541 He could reproduce these symptoms simply by deliberately overbreathing. This appeared to be the first clinical description of heat-induced hyperventilation tetany. The exposure of male test subjects to hot, wet conditions led to physiologic changes and the onset of symptoms ranging from slight tingling of the hands and feet to more severe carpopedal spasm.260,261 The frequency and severity of symptoms were apparently not related to the absolute change in the four measured parameters (Pco2, CO2, pH, and Tre) but rather to the rate of change. When the subject’s tolerance time was short, changes occurred rapidly and the incidence of symptoms was high; conversely, when the tolerance time was long, the same degree of change occurred but the incidence of symptoms was low. It was suggested that rapid changes of the four parameters lead to imbalance between intracellular and extracellular compartments and that this imbalance may be one of the factors inducing symptoms. Again, treatment consists of rest, cooling, and rebreathing expired air.

Heat Cramps Heat cramps typically occur in conditioned athletes who compete for hours in the sun. They can be prevented by increasing dietary salt and staying hydrated.147 Heat cramps are brief, intermittent, and often excruciating; muscle contractions are a frequent complication of heat exhaustion and occurred in about 60% of 969 cases of heat exhaustion.102,325,495 The term heat cramps is a misnomer because heat itself does not cause them; rather, they occur in muscles subjected to intense activity and fatigue. The victim with salt depletion at the time of heat exhaustion is clearly ill and has numerous symptoms other than cramps. Furthermore, fatigue, giddiness, nausea, and vomiting are common and may occur before and more prominently than cramps. Sometimes, heat cramps occur as the only complaint, with minimal systemic symptoms. Furthermore, there is a difficulty in distinguishing abdominal heat cramps from gastrointestinal upset.

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During the 1930s, steel workers, coal miners, sugar cane cutters, and boiler operators were among the most common victims of classic heat cramps.502 Three factors common to most reports are that cramps are preceded by several hours of sustained effort, they are accompanied by heavy sweating in hot surroundings, and they are combined with ingestion of large volumes of water. A fourth factor (see later discussion) may be cooling of the muscles. Serum Na+ levels ranged from 121 to 140 mEq/L (normal, 135 to 145 mEq/L).502 In an industrial setting, heat cramps occur most commonly late in the day, after physical activity has ceased; they sometimes occur while a person is showering and occasionally occur in the evening.325 Hyponatremia and hypochloremia are diagnostic of heat cramps that might be due to salt deficit or some degree of water intoxication.305 If overdrinking causes gastric distention, nausea420 could trigger vasopressin release and contribute to renal water retention. Classic heat cramps are distinguished from hyperventilationinduced tetany in that they are not generalized but are limited to contractions of voluntary skeletal muscles subjected to prior exertion, and they usually affect only a few muscle bundles at a time. Nevertheless, the pain can be excruciating in severe cases. As one bundle relaxes, an adjacent bundle contracts for 1 to 3 minutes. The cramp thus appears to wander over the affected muscle. Three precipitating conditions (exhaustive work, hemodilution, and cooling the muscle) can each depolarize muscle cells.305 This could explain the association of cramps with showering in cool water, because cooling slows the Na+,K+-ATPase pumps and depolarizes the cell, which may thus reach excitation threshold.477 Heat cramps do not occur at the same frequency in all populations. For example, the Indian Armed Forces has a very low incidence340 and Shibolet observed no cases within Israeli Defense Forces.472 These data suggest that heat-acclimated individuals are less likely to experience them. This is consistent with the observation that the incidence was greatest during the first few days of a heat wave.502 Heat cramps generally respond rapidly to sodium chloride solutions. Mild cases may be treated orally with 0.1% to 0.2% NaCl solutions (two to four 10-grain salt tablets [56 to 112 mEq] or 1/4 to 1/2 teaspoon of table salt dissolved in a quart of water). Cooling and flavoring enhance palatability. Oral salt tablets are gastric irritants and not recommended. In severe cases, IV isotonic saline (0.9% NaCl) or small amounts of hypertonic saline (3% NaCl) are administered by physicians for rapid relief.

Heat Exhaustion Classic heat exhaustion is a manifestation of cardiovascular strain resulting from maintaining normothermia in the heat. Symptoms of heat exhaustion include various combinations of headache, dizziness, fatigue, hyperirritability, anxiety, piloerection, chills, nausea, vomiting, heat cramps, and heat sensations in the head and upper torso.20,21,256 Clinical descriptions include tachycardia, hyperventilation, hypotension, and syncope. Although the boundary between heat exhaustion and heatstroke is usually defined as 39.4° to 40° C (102.9° to 104° F), the differential diagnosis is often tenuous229 or even considered artificial.472 The victim may collapse with either a normal or an elevated temperature (severe cases, around 40° C), usually with profuse sweating. Spontaneous body cooling can occur, which is not prominent in severe heatstroke. The clinical determination of heat exhaustion is primarily a diagnosis of exclusion.

Classic heat exhaustion, like classic heatstroke, tends to develop over several days or longer and presents ample opportunity for development of imbalances in electrolytes and water. The hyponatremia and hypochloremia of patients with either heat cramps or salt-depletion heat exhaustion often develops over 3 to 5 days324 and usually in the unacclimatized individual who has not fully developed salt-conserving mechanisms.482,483 In salt-depletion heat exhaustion, muscle cramps, nausea, and vomiting may be intense, but victims do not feel very thirsty.14,256 The major cause of fluid and electrolyte imbalance (salt depletion, water depletion, water intoxication) involved in a particular case of heat exhaustion can be discovered from the history of events surrounding collapse.75,305,325,516 Other forms of heat exhaustion are characterized by the type of fluid or electrolyte deficit (primarily pure water or salt deficiency), their underlying causes (prolonged heat exposure versus intense, short-term exertion), the intensity of hyperthermia, and the absence or form of CNS disturbance. If external cooling does not rapidly lower Tc to normal or, in fact, precipitates severe shivering, intercurrent illness is suspected. Anecdotal experience in the field suggests that approximately 20% of persons with suspected heat exhaustion have some form of viral or bacterial gastroenteritis. This is especially likely if nondisinfected water or ice has been consumed. At any given loss of body weight, the decrement in plasma volume increases with the salt content of sweat. This would be the case for relatively unacclimated individuals. On the other hand, the more dilute the sweat (approaching a pure water deficit) and therefore the greater the retention of salt, the greater the increase in osmolality, plasma sodium, and thirst. Table 10-4 compares and contrasts the signs and symptoms of salt and water depletion heat exhaustion with dilutional hyponatremia. It is clear that at some point both syndromes share many symptoms. Vomiting and cramps appear to signal a significant sodium deficit, in addition to some degree of water deficit.

Heat Illness and Coexistent Disease Coexistent illness or infection predisposes an individual to heatstroke.195 In one study of heat illnesses, 11.2% of patients537 also had gastrointestinal (choleraic) illness.537 The reverse is also true: heat waves produce excess deaths of people with all categories of disease. For example, in one heat wave week in New York in the late summer of 1948, deaths from cardiovascular diseases and diabetes more than doubled (1364 versus 585), and pneumonia deaths tripled.151 Infection predisposes to heat illness, and heat stress exacerbates infections, leading to greater morbidity and mortality.329 Relatively few studies have been reported on the susceptibility to infection during heat exposure, or the influence of infection on heat tolerance; there is need for further research into the effects of diseases on thermoregulation.286


POSSIBLE NEW THERAPIES IL-1 Receptor Antagonist Heatstroke of rats causes hypotension that may be related to the production of inflammatory cytokines such as IL-1. Therefore, interference with the IL-1 pathways by blocking the IL-1 receptor appeared to be a promising means of improving heatstroke symptoms and survival. A single injection of IL-1 recep-

Chapter 10: Pathophysiology of Heat-Related Illnesses tor antagonist (IL-1ra) immediately after the onset of heatstroke in rats blunted the hypotension response to heat, and the rats survived much longer (91 minutes versus 17 minutes) than controls.94 With continuous perfusion of IL-1ra, the survival time increased to 10 hours from the onset of heatstroke. Because heatstroke may lead to a time-dependent shift of Th1 to Th2 cytokine production, timing of such a therapy would be critical, and difficult to perform safely in the field. Currently, the beneficial effects of IL-1ra have not been proven in humans, and the authors do not recommend such therapy. However, if clinical trials should prove its effectiveness, then after initiating cooling procedures and volume therapy, and after transportation to a hospital, administration of IL-1ra may be become part of heatstroke therapy.94

Insulin Rats were rendered diabetic (by streptozotocin) and then heatstroked by exposure to a Tamb of 43° C (109.4° F) for 60 min. Administration of insulin to the diabetic rats attenuated the high core temperature and heart rate, and improved cerebral blood flow and hypotension.388

Free Radical Scavengers Part of the pathophysiology of heatstroke involves production of highly toxic free radicals, or reactive oxygen species. Therefore, administration of scavengers of free radicals seems an obvious choice for therapy.550 Magnolol, obtained from the plant Magnolia officinalis, is a potent free radical scavenger that is 1000-fold more active than α-tocopherol in inhibiting lipid peroxidation in rat mitochondria. In rats heatstroked by exposure to a Tamb of 42° C (107.6° F), magnolol (20 mg/kg, IV) attenuated the pathophysiology associated with heatstroke.87 This pharmaceutical is not recommended for therapy until it undergoes clinical trials and has been proven successful in humans.

Hypertonic Albumin Heatstroked rats were treated with either 10% albumin or an equal volume of saline, and cooled by exposure to a Tamb of 24° C (75.2° F) for 12 min. As seen in Table 10-6, hypertonic albumin had a neuroprotective effect compared with saline controls in reducing elevations of glutamate, glycerol, lactate, and free radicals in the brain.86 The mechanism for this is not understood. It is somewhat counterintuitive, as a rat would normally be expected to be rendered hyperosmotic by heatstroke.

w-3 Fatty Acids At the biochemical level, binding of IL-1 to its specific membrane receptor activates G proteins, which increase intracellular concentration of cyclic adenosine monophosphate (cAMP), which in turn activates membrane phospholipases. Activation of the phospholipases produces arachidonic acid, leukotrienes, prostaglandins, and thromboxanes, ultimately leading to cell damage and organism pathophysiology.88,199 The phospholipases hydrolyze phospholipid esters of fatty acids, which in western diets are largely ω-6 fatty acids.263,321 The ω-6 fatty acids are hydrolyzed into the key metabolite, arachidonic acid. Cells contain two major enzyme classes that can act on arachidonic acid: lipoxygenases and cyclooxygenases. Lipoxygenase acts on arachidonic acid to enter a pathway that results in the formation of 5-hydroperoxyeicosatetraenoic acid (5HPETE) and a series of toxic leukotrienes. Of these, LTB4,

267

LTC4, and LTD4 are the most important. LTB4 induces inflammation, increases capillary leakage, and causes leukocytes to aggregate. LTC4 and LTD4 are potent bronchoconstrictors involved in asthma.105,223 Cyclooxygenase converts arachidonic acid into prostaglandin G2 (PGG2), which is converted into PGH2 with the formation of toxic free radicals. PGH2 is a central metabolite on which a variety of enzymes act to form mainly toxic products, such as thromboxane A2 (TxA2) and many different prostaglandins, including the toxic PGD2. TxA2 causes platelets to aggregate, is a strong vasoconstrictor, and increases capillary leakage. To a person in shock or with another circulatory disorder, such agents could convert a severe but treatable condition into a lethal one. In summary, eating a normal Western diet results in the presence of large amounts of ω-6 fatty acids in phospholipid cell membranes, predisposing to the formation of arachidonic acid and a large number of its toxic metabolites. For a review of prostaglandin and thromboxane biochemistry, see references.57,371,391 In fish-enriched diets laden with ω-3 fatty acids, a high proportion of the ω-6 fatty acids in plasma membranes are replaced by the ω-3 fatty acids, phospholipases hydrolyze the phospholipids into eicosapentaenoic acid, and no arachidonic acid is produced. Therefore, no strongly toxic thromboxanes, prostaglandins, and leukotrienes are produced. Instead, only slightly toxic leukotriene B5 is formed. A diet enriched in fish oil (rich in ω-3 fatty acids) dramatically downregulates key immunoregulatory cytokines involved in autoimmune disease.267 Mice fed fish oil for 6 weeks showed reduced fever and weight loss caused by LPS injection and did not have the rise in PGE2 that normally results from LPS activity. These changes suggest that the pathophysiology induced by toxic arachidonic acid metabolites can be reduced or prevented by dietary replacement of ω-6 fatty acids with ω-3 fatty acids.310 However, there was an exaggerated rise in TNFα, a toxin in itself, possibly because of the lack of the negative feedback from PGE2. Therefore, although these studies appear promising, they must be interpreted with extreme caution and are not recommended to guide prophylaxis for heatstroke. There has not yet appeared a clinical study showing that injection or ingestion of ω-3 fatty acids protects humans against heat illnesses. However, supplementing a normal Western diet with fish oil capsules replaces a significant proportion of ω-6 fatty acids by ω-3 fatty acids in human cell membranes within 6 weeks, and possibly much sooner.153

Cyclooxygenase Inhibitors Fever, in contrast to exercise hyperthermia, represents a physiologic state in which the hypothalamic thermostat has been reset above 37° C (98.6° F) by exogenous pyrogens released from bacteria or viruses131 or by IL-1,150,270,372 IL-2, or interferon-α and interferon-β.50 Cytokines may be responsible in part for other clinical symptoms of fever, including fatigue, malaise, and edema. αMelanocyte-stimulating hormone inhibits IL-1-induced fever and the acute phase response.335 Neutralizing antibodies to IL1 and TNF have been found in the sera of both normal and sick individuals and may play a role in their regulation.501 Current evidence suggests that aspirin-like cyclooxygenase inhibitors interfere with IL-1-induced fever or shock responses by inhibiting prostaglandin synthesis.397 Nevertheless, in an experimental model of heatstroke, rats were pretreated with aspirin and survived longer than did controls.254

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Defervation Circulating LPS reaches the thermoregulatory control center in the anterior hypothalamus, activates cyclooxygenase, and induces prostaglandins.244,358 LPS is also bound by the liver, where it stimulates the vagus nerve to signal the hypothalamus to produce prostaglandins.433 At the onset of fever, a patient often feels chilled and shivers to elevate Tc by additional metabolic heat. A new, higher, preferred ambient temperature is behaviorally established.393 The physiologic change is even more important. Once this new set point temperature is established, the thermoregulatory center uses all available thermoregulatory mechanisms to maintain it. As a result, attempts at whole-body cooling are met with sensations of extreme discomfort and violent shivering. When unsuccessful attempts to cool patients who have suspected heat illness result in chills and violent shivering, coexistent infection or disease is suggested. This prostaglandin-mediated pathway may be responsible for fever, normal circadian temperature variation, pathologic temperature elevations, and temperature elevations related to stress.41,298 Although there may be pyrogens that do not act via prostaglandins,113,262 treatment, if necessary, should be directed at agents that block the action of the pyrogen at the hypothalamic receptor sites. External application of cold to reduce true fever may be counterproductive497 and is often ineffective, even after antipyretic therapy.27,385 The body defends the higher temperature set point against environmental cooling. Therapy for fever that uses agents to block the causative molecular interaction is the most rational and clinically effective approach. Aspirin and other antipyretic agents, such as acetaminophen, indomethacin, ibuprofen, and other newer nonsteroidal anti-inflammatory compounds, are effective and act either directly or indirectly

11

through inhibition of the prostaglandin mechanism.114,372 The normal febrile response is generally self-limited in both magnitude and duration.533 Vasopressin521 and melanotropin382 appear to act centrally to suppress temperature elevation and may be important in preventing extreme hyperthermia.

Should Antipyretic Therapy Be Routine? High temperatures enhance resistance to viral and bacterial infections in experimental animals.38,81,174 For example, replication of DNA viruses is inhibited by mild hyperthermia,194,242,337 and measles virus membrane protein is selectively blocked by heating cultures to 39° C (102.2° F).394 Some host defense functions438,518 that become more effective at 40° C (104° F) than at 37° C (98.6° F) level off or diminish at 42° or 43° C (107.6° or 109.4° F).497 Although fever has long been recognized as a manifestation of disease24 and may be identified as a debilitating problem even in the absence of other signs or symptoms,527 antipyretic therapy should not be instituted routinely for every febrile episode.165,206 Furthermore, although administration of aspirin lowers fever by altering the thermoregulatory set point in the hypothalamus, it also leads to a greater rise in Tc in response to a standardized heat stress and therefore is not a universal temperature-lowering agent.156 In summary, at Tc up to approximately 40° C (104° F), the febrile process has a role in host defense, and routine antipyretic therapy for fever is generally unnecessary and may be harmful,497 especially because of the link between aspirin and Reye’s syndrome.497 Instead, treatment should be based on evaluation of relative risks.49,139,297 The references for this chapter can be found on the accompanying DVD-ROM.

Clinical Management of Heat-Related Illnesses Daniel S. Moran and Stephen L. Gaffin

This chapter discusses clinical observations of heatstroke victims and management of heat-related illnesses. In heatstroke, the most severe heat illness associated with excess body heat, early clinical signs are nonspecific. A common picture of heatstroke is sudden collapse of an individual during physical activity in a warm environment. This is usually followed by loss of consciousness with elevated core temperature (Tc) greater than 40° C (104° F), rapid heart rate (HR), tachypnea, hypotension, and, possibly, shock. Severity of heat illness depends on the

degree of elevation in Tc and its duration. Heatstroke is an extreme medical emergency that can be fatal if not diagnosed and treated promptly. Therefore, to prevent and minimize complications and save lives, proper management and clinical care are essential. This chapter focuses on the three different phases of heatstroke (acute, hematologic and enzymatic, and late), problems with recognition of heat illnesses, diagnosis and complications of heatstroke, treatment, and awareness of risk factors.

Chapter 11: Clinical Management of Heat-Related Illnesses

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TABLE 11-1. Comparison of Classic and Exertional Heatstroke CHARACTERISTICS

CLASSIC

EXERTIONAL

Age group Health status Concurrent activity Drug use

Older adults Chronically ill Sedentary Diuretics, antidepressants, antihypertensives, anticholinergics, antipsychotics May be absent Usually absent; poor prognosis if present Usually absent Uncommon Uncommon Mildly elevated Unusual Mild 39° C

no

Flushed skin HR >120 bpm

yes no DD

yes

Known cause

yes

yes

no yes

Heat exhaustion, suspected heatstroke

Tre > 40° C

• Cooling • IV fluids

• Cooling • IV fluids

Evacuation

Not heatstroke/ heat exhaustion

yes

Tre > 40° C

Exertional heatstroke

no

no Suspected heatstroke

Recovery

yes

Hospitalization

Follow up 24 hr

Figure 11-3. Flow chart for on-site emergency medical treatment of exertional heat illnesses. CPR, cardiopulmonary resuscitation; DD, differential diagnosis; HR, heart rate; IV, intravenous; Tre , rectal temperature. (Modified from Shapiro Y, Seidman DS: Med Sci Sports Exerc 22:6, 1990.)

tance that these measures only barely delay evacuation of the victim to a hospital or the closest medical facility. In a comatose victim, airway control should be established by insertion of a cuffed endotracheal tube. When available, administration of supplemental oxygen may help meet increased metabolic demands and treat the hypoxia commonly associated with aspiration, pulmonary hemorrhage, pulmonary infarction, pneumonitis, or pulmonary edema.56,122 Positive-pressure ventilation is indicated if hypoxia persists despite supplemental oxygen administration (Fig. 11-3).

As discussed previously, resuscitative measures may rapidly lower body temperature. Monitoring and recording Tre on site may be important for the correct diagnosis of heatstroke. Vital signs should be monitored, with attention to blood pressure and pulse. Although normotension should not be taken as a reassuring sign, hypotension should be recognized for the ominous sign it always represents. If possible, urine and blood samples should be obtained for electrolyte evaluation, especially Na+ to avoid hyponatremia, before fluid infusion.

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Vascular access should be established without delay by insertion of a large-gauge IV catheter. Administration of normal saline or lactated Ringer’s solution should be started. Recommendations regarding the rate of administration of fluids vary. Some authors advise a rate of 1200 mL (1.26 qt) over 4 hours,136 but we consider this to be too conservative. Others encourage a 2-L (2.11-qt) bolus over the first hour and an additional liter of fluid per hour for the next 3 hours.160 Vigorous fluid resuscitation may precipitate development of pulmonary edema, so careful monitoring is indicated. Ideally, 1 to 2 L (1.05 to 2.11 qt) of fluid should be administered during the first hour after collapse and additional fluids administered according to the level of hydration.61 Cooling measures should be initiated immediately. However, cooling techniques are ineffective when the victim suffers seizures that increase storage of body heat. Therefore, convulsions should be controlled by IV administration of 5 to 10 mg of diazepam, as necessary. As a result of drastic cooling, Tsk may decrease enough to cause shivering. IV administration of chlorpromazine (50 mg)97 or diazepam (5 mg) is effective to suppress shivering and prevent an additional rise in body temperature from metabolic heat production.

Heat-Induced Syncope In an upright and stationary person, blood volume is displaced into the dependent limbs by gravity. If that person is also heat stressed, more blood is displaced into the peripheral circulation to support heat transfer at the body surface. These combined reductions in effective blood volume can temporarily compromise venous return, cardiac output, and cerebral perfusion. Fainting is usually brief and responds to horizontal positioning and improved venous return. The patient should be allowed to rest in cooler, shadier surroundings (as the solar heat load can be >200 kcal/hr) and should be offered cool water. The patient should be cautioned against protracted standing in hot environments, advised to flex leg muscles repeatedly while standing to enhance venous return, and warned to assume a sitting or horizontal position at the onset of warning signs or symptoms, such as vertigo, nausea, or weakness. Normally, muscles in the legs act as a “second heart” and, in concert with venous valves, promote venous return, thereby counteracting orthostatic pooling and the predisposition to syncope. Consistent with this, nonfainters have higher intramuscular pressure than do fainters. In stark contrast to simple syncope is the profound CNS dysfunction dominating the early course of heatstroke. Thus, if a person faints in a setting where hyperthermia is possible and does not rapidly return to consciousness, heatstroke should be suspected, cooling measures instituted, and body temperature monitored.

Cooling Methods Much debate exists in the literature regarding the best approach to cooling heatstroke victims.37,45,75,165,180,181 Morbidity and mortality are directly related to duration and intensity of elevated Tc. Therefore, the rate at which any given method lowers body temperature is extremely important. Another consideration in choosing a cooling modality is the need for access to the victim for continuous monitoring. Proulx and colleagues142 used cooling water immersion at 2° C (35.6° F) to achieve a cooling body rate of 0.35° C/min. At water temperatures of 8, 14, and 20° C (46.4°, 57.2°, and

68° F), cooling rate was 0.19°, 0.15°, and 0.19° C/min, respectively. Shivering was seldom observed during the 20° C water immersion. In contrast, Clements and coworkers35 found no significant differences between the cooling rates of water immersion at 5.2° C and at 14° C (41.4° and 57.2° F). According to these two studies and others,78 a clear recommendation regarding optimal water temperature for cooling cannot be stated. Khogali and coworkers180 developed a body cooling unit designed to maximize evaporative cooling by maintaining cutaneous vasodilation and minimizing shivering. The patient is suspended on a net and sprayed from all sides with water at 15° C (59° F). Warm (45° to 48° C [113° to 118.4° F]) air is blown over the victim. Cooling rates of 0.06° C/min (0.11° F/min) have been obtained. Although this method is widely recommended as the treatment of choice, the rate of cooling is actually much less than that accomplished by icewater immersion. Although not always available, ice-water or cold-water immersion is an effective and easily available method of rapidly lowering core body temperature. However, its use is one of the more hotly debated topics in the heatstroke literature. In most cases, increased thermal conductivity of water results in reduction of Tc to less than 39° C (102.2° F) in 10 to 40 minutes.46 This reflects a mean rate of cooling of 0.13° C/min (0.23° F/ min)—that is, twice the rate of the body cooling unit. Use of cold water rather than ice water resulted in the same rate of cooling—0.13° C/min.136 Cold-water immersion is less uncomfortable for the victim than is immersion in ice water. In several hundred EHS victims in a military population, there were no fatalities or permanent sequelae after treatment with ice-water immersion and massage.46,136 Although other cooling methods reduce the rate of mortality, none has been as successful as ice water–soaked sheets or immersion.67 Poulton and Walker141 treated heatstroke patients by using a light helicopter as a large powerful fan to provide surface cooling and enhance evaporation of water sprayed over the patients. These authors found the method to be an efficient cooling concept. However, the helicopter rotary blade downdraft carries potential risks for the patient and medical staff attendants. In discussing an alternative cooling method, Khogali101,180 summarizes the most commonly offered criticisms of ice-water immersion: • Exposure to severely cold temperatures may cause peripheral vasoconstriction with shunting of blood away from the skin, resulting in a paradoxical rise in core temperature. • Induction of shivering (in response to the cold) may cause additional elevation in temperature. • Exposure to ice water causes marked patient discomfort. • Working in ice water is uncomfortable for medical attendants. • Accessing the patient to monitor vital signs or administer cardiopulmonary resuscitation is more difficult. • It is difficult to maintain sanitary conditions if vomiting or diarrhea develops. Although the first two criticisms may appear physiologically appropriate, review of the medical literature fails to provide documentation that a rise in body temperature after ice-water immersion or shivering is a problem.46 In fact, vascular resistance decreased during ice bath cooling and persisted until normothermia was achieved.136 This is an expected observation. The hypothalamic set point for temperature regulation is not

Chapter 11: Clinical Management of Heat-Related Illnesses raised during heatstroke (unlike during febrile illness), and brain temperature accounts for approximately 90% of the thermoregulatory response, compared with the skin’s 10%.152 The shivering response should occur only if body temperature is allowed to fall below normal. When shivering occurred, IV chlorpromazine treatment (25 to 50 mg) was effective.90 Heatstroke victims rarely require cardiopulmonary resuscitation, so this concern should not preclude use of ice baths to treat heatstroke. The documented efficacy of ice-water immersion in rapidly reducing body temperature, and therefore morbidity and mortality, overrides any consideration of transient personal discomfort for the patient or medical attendants. If other methods are used initially, any victim whose Tc does not reach 38.9° C (102.2° F) within 30 minutes after beginning treatment should be placed in a tub containing ice water or on a stretcher above the tub and covered with ice water–drenched sheets and massaged.67 The tub should be deep enough for submersion of the neck and torso. Rapidly falling Tc may not be accurately reflected by measured Tre,36 so, with any cooling technique, active cooling should be discontinued when core body temperature falls to 39° C (102.2° F) to prevent inducing hypothermia. Ducharme and colleagues,143 however, suggested that to avoid hypothermia, the cooling of body core temperatures of hyperthermic individuals should not go below 38.5° C (101.3° F)—that is, it is not necessary to eliminate all of the heat gained. In summary, ice-water treatment cools EHS patients fastest, can be easily set up with little training, is available in most hospitals without purchasing capital equipment, and may also be used on classic heatstroke victims. However, when treating older adults with classic heatstroke, a case-by-case decision should be made that balances the risk of a theoretical, but never shown, harmful stress by ice-water treatment, against the clear benefit of rapid cooling. Otherwise, cold-water or ice-water cooling is the method of choice. Various ancillary modalities have been proposed to facilitate cooling, including administration of cold IV fluids, gastric lavage with cold fluids, and inhaling cooled air. Although these therapies lower body temperature, their effects are minimal compared with ice-water immersion. Cooling blankets are ineffective for inducing the rapid lowering of body temperature required in treatment of heatstroke. Use of antipyretics is inappropriate and potentially harmful in heatstroke victims. Aspirin and acetaminophen lower temperature by normalizing the elevated hypothalamic set point caused by pyrogens; in heatstroke, the set point is normal, with temperature elevation reflecting failure of normal cooling mechanisms. Furthermore, acetaminophen may induce additional hepatic damage, and administration of aspirin may aggravate bleeding tendencies. Alcohol sponge baths are inappropriate under any circumstances, because absorption of alcohol may lead to poisoning and coma.


HOSPITAL EMERGENCY MEDICAL TREATMENT

If airway control was not previously established, a cuffed endotracheal tube should be inserted to protect against aspiration of oral secretions (Fig. 11-4). Supplemental oxygen and, when necessary, positive-pressure ventilation should be provided. Temperature should be monitored at 5-minute intervals by

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means of an esophageal or rectal probe. Cooling measures should be maintained for Tc greater than 38° C (100.4° F). IV access should be obtained as quickly as possible. In the emergency department, IV fluid should be administered to EHS victims as a bolus of 1 L (1.05 qt). Administration of additional fluid should be based on the clinical situation after laboratory results are obtained; the object is to support the circulatory system without risk of inducing pulmonary or cerebral edema. Most heatstroke victims arrive with high cardiac index, low peripheral vascular resistance, and mild right-sided heart failure with elevated central venous pressure. Only moderate fluid replacement is indicated if effective cooling results in vasoconstriction and increased blood pressure. A Swan-Ganz pulmonary artery catheter may be necessary to assess appropriate fluid supplementation. Some victims have low cardiac index, hypotension, and elevated central venous pressure. These persons have been successfully treated with an isoproterenol drip (1 mg/min).136 Patients with low cardiac index, low central venous pressure, hypotension, and low pulmonary capillary wedge pressure should receive fluid. Cardiac monitoring should be maintained during at least the first 24 hours of hospitalization. Use of norepinephrine and other α-adrenergic drugs should be avoided because they cause vasoconstriction, thereby reducing heat exchange through the skin. Anticholinergic drugs that inhibit sweating, such as atropine, should also be avoided. As previously discussed, chlorpromazine may be used to treat uncontrollable shivering that might lead to rising body temperature. However, chlorpromazine should be used advisedly because it may cause hypotension or seizures, and its anticholinergic effects may interfere with sweating. For these reasons, some physicians prefer to use diazepam to control shivering. A Foley catheter should be placed to monitor urine output. Myoglobinuria and hyperuricemia can be prevented by promoting renal blood flow by administering IV mannitol (0.25 mg/kg) or furosemide (1 mg/kg).160 Early dialysis should be reconsidered if anuria, uremia, or hyperkalemia develops. Cooling and hydration usually correct any acid–base abnormality; however, serum electrolytes should be monitored and appropriate modifications of IV fluids made. Glucose should be monitored repeatedly because either hypoglycemia or hyperglycemia may occur after heatstroke.156 Oral and gastric secretions are evacuated via a nasogastric tube connected to continuous low suction. Although antacids and histamine-2 blockers have been used to prevent gastrointestinal bleeding, no studies to date demonstrate their efficacy in heatstroke victims. As previously discussed, clotting disturbances peak 18 to 36 hours after onset of heat injury.164 Coagulation tests (platelet count, prothrombin time, fibrinogen levels, fibrin split products) should be obtained on admission and after 24 hours. DIC may develop 24 to 72 hours after admission and is marked by acute onset of bleeding from venipuncture sites, gingivae, nasal mucosae, lungs, or the gastrointestinal tract. DIC is best prevented by rapid cooling of initial hyperthermia and replacement of clotting factors and platelets by transfusion of fresh frozen plasma and platelets. Acute hepatic dysfunction is exhibited by elevated levels of aminotransferases and bilirubin. Peak levels are seen 36 to 72 hours after collapse. These high levels may last for several days.61,125,162 Muscle damage is displayed primarily by marked elevation of serum CPK activity levels, which peak 24 to 48

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PART TWO: COLD AND HEAT

Hospitalization

CPR if required

IV Diazepam 5-10 mg

yes Seizures? no

no

Seizures controlled?

Tre > 38.5° C ?

no

yes

yes

Heatstroke

CONTROL Fluid/electrolytes balance Acid-base balance Coagulation disturbances Renal insufficiency Other disturbances

Figure 11-4. Flow chart for hospital medical treatment of exertional heat illnesses;CPR,cardiopulmonary resuscitation;IV, intravenous; Tre, rectal temperature. (Modified from Shapiro Y, Seidman DS: Med Sci Sports Exerc 22:6, 1990.)

Cooling rehydration (IV)

yes

Impaired biochemistry?

no

Follow up 48 hr

On admission and periodically CHECK Acid-base balance Electrolytes Glucose Serum enzymes Liver function tests Renal function tests Coagulation factors

hours after collapse and usually return to normal spontaneously within 5 days. Muscle and liver enzymes and bilirubin values should be carefully followed, but drastic intervention (e.g., liver transplant) is rarely necessary.

Prognosis The combination of rapid reduction of body temperature, control of seizures, proper rehydration, and prompt evacuation to an emergency medical facility results in a 90% to 95% survival rate in heatstroke victims, with morbidity directly related to duration of hyperthermia.159 A poor prognosis is associated with a Tc of greater than 41° C (105.8° F), prolonged duration of hyperthermia, hyperkalemia, acute renal failure, and elevated serum levels of liver enzymes. Therefore, misdiagnosis, early inefficient treatment, and delay in evacuation are the major

causes of deterioration in the patient’s condition. Full recovery without evidence of neurologic impairment has been achieved even after coma of 24 hours’ duration and subsequent seizures.162 Persistence of coma after return to normothermia is a poor prognostic sign.164 Neurologic deficits may persist, but usually for a limited period of 12 to 24 months, and only rarely for longer. One recent study of classic heatstroke reported that 33% of patients left the hospital with some neurologic impairment.48

Dantrolene No drug has been found to have a significant effect in reducing body temperature. Antipyretics are ineffective because the thermoregulatory set point is not affected in heatstroke. Furthermore, antipyretics might be harmful, as they cannot be readily

Chapter 11: Clinical Management of Heat-Related Illnesses metabolized in the heat-affected liver. However, dantrolene has been used quite successfully in the treatment of several hypercatabolic syndromes, such as malignant hyperthermia, neuroleptic malignant syndrome, and other conditions characterized by muscular rigidity or spasticity.171,179 Dantrolene stabilizes the Ca2+ release channel in muscle cells, reducing the amount of Ca2+ released from cellular calcium stores. This lowers intracellular Ca2+ concentrations, muscle metabolic activity, and muscle tone, and thus heat production.32,134 In some studies, dantrolene was claimed to be effective in treating heatstroke, but in others it improved neither the rate of cooling nor survival.30,49,121,173 In six rhabdomyolysis patients, intramuscular Ca2+ concentrations were 11 times higher than in controls, and dantrolene successfully lowered this elevated Ca2+.118 Collectively, the limited data available are at best inconsistent. In spite of growing evidence for a possible benefit of dantrolene treatment in heatstroke, justification for its routine use in such cases is not proved, although future clinical trials may change this assessment.9,22,116,144 Moran and colleagues126 studied dantrolene in a hyperthermic rat model. They found it effective as a prophylactic agent in sedentary animals only. Dantrolene induced more rapid cooling by depressing Ca2+ entry into the sarcoplasm. This led to relaxation of peripheral blood vessels with attenuated production of metabolic heat. Dantrolene also may be effective in treating heatstroke by increasing the cooling rate. However, in other animal models, dantrolene was not superior to conventional cooling methods.185

Neuroleptic Seizure Psychiatric patients treated with high doses of neuroleptic drugs, antidepressants, antiemetics, and other drugs52 may develop fatal neuroleptic malignant syndrome, characterized by hyperthermia as high as 42° C (107.6° F), “lead pipe” (skeletal muscle) rigidity, dyspnea, coma, extrapyramidal syndrome, rhabdomyolysis, severe metabolic acidosis, leukocytosis, and elevated creatine kinase.39,84,91 Successful treatment of these cases includes immediate withdrawal of the offending drug, administration of dantrolene, and either oral bromocriptine or the combination of levodopa and carbidopa.52


PREVENTION Prevention of heat illness relies on awareness of host risk factors, altering behavior and physical activity to match these risk factors and environmental conditions, and a requirement for appropriate hydration during physical exercise in the heat. More aggressive educational activity of the media explaining heat illness and its prevention to the public is to be strongly promoted. Primary care physicians should incorporate this information in the anticipatory guidance of routine health assessment. Despite a wealth of medical literature on heat injury, some athletic coaches continue to use physical or psychological methods to force athletes to compete or run under intolerably hot conditions. This practice should be viewed as irresponsible, dangerous, and possibly criminally negligent.

Awareness of Host Risk Factors Any underlying condition that causes dehydration or increased heat production, or that causes decreased dissipation of heat, interferes with normal thermoregulatory mechanisms and predisposes an individual to heat injury. Older individuals are less

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heat tolerant than are younger persons to EHI, and are more susceptible to classic heatstroke because of decreased secretory ability of sweat glands and decreased ability of the cardiovascular system to increase blood flow to the skin. When healthy young adults exercise strenuously in the heat, EHS may occur despite the absence of host risk factors. In particular, persons with type II muscle fiber predominance are more susceptible to EHS because these fibers are “faster” but less efficient than are other fiber types.89 In principle, because women have a thicker subcutaneous fat layer and a Tc that is 0.4° to 0.5° C (0.7° to 0.9° F) higher during the luteal phase than in the follicular phase, they may be at greater risk for heat injury during the luteal phase, but this has not been documented in controlled studies.169 Elite and professional athletes, the general public, and the military have widely used ergogenic aids, such as the herb ephedra (ma huang) containing ephedrine, to improve performance and lose weight. Because ephedra increases metabolic rate, it has caused numerous cases of heat illnesses and deaths worldwide and is banned. Because there are no clear ergogenic benefits in using ephedra alone, use of ephedra-containing substances should be discouraged.137 In children, the ratio of basal metabolic rate to surface area is higher than it is in adults. As a result, the child’s Tsk is higher. Although the secretory rates of sweat glands are lower in children, they have greater numbers of active sweat glands per area of skin than do adults and overall greater sweat rates per unit area.88 Any reduction in sweat rates would therefore put children especially at risk. Endocrine abnormalities, such as hyperthyroidism and pheochromocytoma, cause a marked increase in heat production. Acute febrile illness, by virtue of the elevated hypothalamic set point caused by pyrogens, also leads to increased heat production. Muscular activity associated with uncontrolled gross motor seizures or delirium tremens also releases significant metabolic heat. The primary means of heat dissipation is production and evaporation of sweat. Any condition that reduces this process places the individual at risk for thermal injury. Poor physical conditioning, fatigue, sleep deprivation, cardiovascular disease, and lack of acclimation all limit the cardiovascular response to heat stress. Obesity places an individual at risk from reduced cardiac output, increased energy cost of moving extra mass, increased thermal insulation, and altered distribution of heatactivated sweat glands.128 Older adults and the young show decreased efficiency of thermoregulatory functions and increased risk of heat injury. Several congenital or acquired abnormalities affect sweat production and evaporation. Ectodermal dysplasia is the most common form of congenital anhidrosis. Widespread psoriasis, scleroderma, miliaria rubra (“prickly heat,” caused by plugging of the sweat ducts with keratin), or deep burns may also limit sweat production. Dehydration affects both central thermoregulation and sweating. A mere 2% decrease in body mass through fluid loss produces an increase in HR, an increase in Tc, and a decrease in PV. In an otherwise healthy adult, gastrointestinal infection with vomiting and diarrhea may cause sufficient dehydration to place the individual at risk for EHS. Chronic conditions that may contribute to dehydration include diabetes mellitus, diabetes insipidus, eating disorders (especially bulimia), and mental retardation. Alcoholism and illicit drug use are among the 10

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Box 11-3. Drugs That Interfere with Thermoregulation DRUGS THAT INCREASE HEAT PRODUCTION

• • • •

Thyroid hormone Amphetamines Tricyclic antidepressants Lysergic acid diethylamide (LSD)

DRUGS THAT DECREASE THIRST

• Haloperidol

Clothing Different regions of the body are not equivalent in their sweat production.87 The face and scalp account for 50% of total sweat production, whereas the lower extremities contribute only 25%. When exercising under conditions of high heat load, maximal evaporation of sweat is facilitated by maximal exposure of skin. Clothing should be lightweight and absorbent. Although significant improvement has been made in the fabrication of athletic uniforms, the uniforms and protective gear required by certain branches of the military and public safety officers continue to add to the risk of heat injury. Development of protective clothing that permits more effective heat dissipation is indicated.

DRUGS THAT DECREASE SWEATING

• • • •

Antihistamines (diphenhydramine) Anticholinergics Phenothiazines Benztropine mesylate

From references 16, 46, 81, 108, 162, 164.

major risk factors for heatstroke in the general population.104 An important effect of alcohol consumption is inhibition of ADH secretion, leading to relative dehydration. Despite evidence that hypohydration limits physical performance, voluntary dehydration continues to be routine in certain athletic arenas.9,13,28,174 Wrestlers, jockeys, boxers, and bodybuilders commonly lose 3% to 5% of their body mass 1 to 2 days before competition. In addition to restricting fluid and food, they use other pathogenic weight control measures, such as self-induced vomiting, laxatives and diuretics, and exposure to heat (saunas, hot tubs, and “sauna suits”). Athletes undergoing rapid dehydration are at risk not only for heat injury but also for other serious medical conditions, such as pulmonary embolism.47 Box 11-3 highlights common medications that interfere with thermoregulation. Special attention should be paid to the role of antihistamines in reducing sweating. This class of medications is commonly obtained over the counter, and the general population should be warned of the dangers of exercising in the heat when taking antihistamines. Although it has been widely believed that sustaining an episode of heatstroke predisposes the individual to future heat injury, this has been refuted in a recent study of heatstroke victims.14 Ten heatstroke patients were tested for their ability to acclimate to heat; by definition, the ability to acclimate to heat indicates heat tolerance. Nine of these patients demonstrated heat tolerance within 3 months after the heatstroke episode; the remaining patient acclimated to heat a year after his heat injury. In no case was heat intolerance permanent. Although individuals may show transient heat intolerance after thermal injury, evidence for permanent susceptibility to thermal injury is lacking.

Adaptation to Environmental Conditions Appropriate adaptation to hot environmental conditions encompasses many forms of behavior, including modification of clothing, degree of physical activity, searching for shade, anticipatory enhancement of physical conditioning, acclimation to heat stress, and attention to hydration.

Activity Behavioral actions can effectively minimize the occurrence of classic heatstroke. Lack of residential air conditioning places indigent persons at risk during heat waves. By sitting in a cool or tepid bath periodically throughout the day, the individual can decrease the heat stress and thereby prevent heat injury. The more than 10,000 deaths in the 2003 heat wave in Europe could have been reduced by simple announcements by public health officials of exactly this preventive measure. Modification of physical activity should not be based solely on any individual parameter of Tamb, wet bulb temperature or relative humidity, or solar radiation, as all of these contribute to heat load. The wet bulb globe temperature (WBGT) is an index of heat stress that incorporates all three factors. This value may be calculated (see Table 11-2) or obtained directly from portable heat stress monitors that measure all three parameters simultaneously to compute the WBGT. Alternatively, the heat index may be obtained from national weather stations. Current recommendations from the American College of Sports Medicine (ACSM) for prevention of thermal injuries during distance running are based on the WBGT.8 It is stated that “distance races (≥16 km or 10 miles) should not be conducted when the WBGT exceeds 28° C (82.4° F). During periods of the year when the daylight Tamb often exceeds 27° C (80° F), distance races should be conducted in the early morning or in the evening to minimize the heat load from Tamb and solar radiation.”8 In the British Army, the strenuous Combat Fitness Test (CFT) occasionally leads to heat casualties. To prevent a mean rise in Tc of 0.7° C (1.26° F) and to minimize heat illnesses, calculations indicate that the CFT should not be undertaken when the end WBGT is expected to be greater than 25° C (77° F).26 Table 11-3 presents a suggested modification of sports activity that is also based on the WBGT. Although ACSM guidelines for summer indicate that vigorous physical activity should be scheduled in the mornings or in the evenings, it should be cautioned that the highest humidity of the day is usually during early morning. In 1999, Montain and coworkers124 updated the replacement guidelines for warm weather training (see Chapter 64, Table 64-7). It is important to note that compliance with these recommendations does not remove all risk of heat injury. Developing another index of heat stress that provides a better basis for prevention of EHS is indicated. Recently, a new, userfriendly, miniaturized 5.1 × 2.5 × 1.3 cm (2- × 1- × 0.5-inch) device based on measuring Tamb and RH with microsensors was developed for assessment of heat stress.129 However, further miniaturization and evaluations of this device are required.3

Chapter 11: Clinical Management of Heat-Related Illnesses

TABLE 11-3. Modification of Sports Activity on the Basis of Wet Bulb Globe Temperature (WBGT) INDEX (°F) 2,000 —

— >25,000

— —

— —

— —

>65,200

>53,840

53,090 289,470

28,000

89,340

VOLCANO Merapi Kelut Vesuvius Etna Merapi Awu Oshima Cotopaxi Makian Papadajan Laki Asama Unzen Mayon Tambora Galunggung Nevado del Ruiz Awu Cotopaxi Krakatau Awu La Soufriere Montagne Pelée Santa María Taal Kelut Merapi Lamington Hibok-Hibok Agung Mount St. Helens El Chichón Nevado del Ruiz

Totals: GRAND TOTAL From Tilling RI: Rev Geophys 27:239, 1989.

TABLE 15-3. Fatalities from Volcanic Eruptions, 1783–2000 FATALITIES VOLCANIC HAZARD Post-eruption famine and disease epidemics Pyroclastic flows Lahars Volcanogenic tsunamis Debris avalanches Air fall Volcanic gases Lava flows TOTAL

No.

%

75,000 67,500 42,500 42,500 10,000 10,000 1,750 750 250,000

30 27 17 17 4 4 400 mg/24 hr; reduce dosage in older adults; patients with cirrhosis, 50 mg every 12 hr

COX-2, cyclooxygenase-2. From Burnham T, et al (eds): Drug Facts and Comparisons. St. Louis, Facts and Comparisons, 1999; Emermann CL, Spenetta J: Pain management in the emergency department. Emerg Med Rep 23:53–67, 2002; and Lawrence R, Rosch P, Plowden J: Magnet Therapy: The Pain Cure Alternative. Rocklin, CA, Prima, 1998.


PHARMACOLOGIC TREATMENT OF PAIN

Analgesics See Tables 17-1 and 17-2 for oral and parenteral dosage recommendations.

Opioid Analgesics Opium emerged as the first widely used narcotic analgesic by the time of the Renaissance, generally in the form of a powder or sticky gum. It was often combined with alcohol to form laudanum. Prussian pharmacist Frederich Sertürner isolated morphine from opium in the 19th century. Development of the hypodermic needle and syringe by Rynd in Ireland and Pravaz in France greatly enhanced morphine’s clinical utility in pain management.38 Narcotic agonists affect the mu (µ), kappa (κ), and delta (δ) opiate receptors in the central nervous system (CNS) and

periphery.44 Morphine and other opioids are administered orally, intranasally,48 sublingually, transdermally, subcutaneously, intramuscularly, intravenously, and rectally. Morphine is metabolized primarily in the liver; approximately 10% is excreted through the kidneys. Hepatic and renal damage impact the recipient’s response, so tolerance for a given dosage must not be presumed with these conditions. Bioavailability depends on tissue perfusion. Morphine is a potent analgesic with sedative and euphoric effects that also depresses the CNS and respiratory drive. Critical patient assessment is always required when using narcotic analgesics to detect respiratory depression and hypotension. This is particularly true in situations of hypoxia, such as occur at high altitude. Other opioid agonists include codeine, which is a controlled substance in the United States but available over the counter in many other countries, and meperidine, methadone, propoxyphene, and hydromorphone. Semisynthetic narcotics that exhibit much shorter durations of action include fentanyl and sufentanyl.

Chapter 17: Principles of Pain Management

417

TABLE 17-2. Common Parenteral Analgesics: Dosage Recommendations in 70-kg Adults DRUG

DOSAGE (mg)

INTERVAL (hr)

RISKS, PRECAUTIONS

Narcotic Agonists Codeine Fentanyl Hydromorphone Levorphanol Morphine Meperidine

15–75 IM 50–100 µg 1–2 IM 4 10–20 IM, 2.5 IV 50–100 IM, 25–50 IV

4–6 0.5–1 3–4 6–8 3–5 2–4

Oxymorphone

1

3–4

Narcotic side effects Narcotic side effects, wide range of dosages Narcotic side effects, choice over morphine in hepatic impairment Narcotic side effects Narcotic side effects Narcotic side effects, active metabolite accumulates in renal impairment and may cause seizures Narcotic side effects

Narcotic Agonists/Antagonists Buprenorphine 0.3–0.6 IM Butorphanol 2–4 IM Dezocine 5–20 IM, 5–10 IV Nalbuphine 10–20 IM, 1–5 IV

6–8 3–4 2–4 3–6

May May May May

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) Ketorolac 15–30 IM, 2–5 IV

4–6

Similar to aspirin

Dissociative Analgesic/Anesthetic Ketamine 50–75 IM, 15–30 IV

2–4

Increased intracranial pressure

precipitate precipitate precipitate precipitate

narcotic narcotic narcotic narcotic

withdrawal withdrawal withdrawal withdrawal

IM, intramuscularly; IV, intravenously. From Burnham T, et al (eds): Drug Facts and Comparisons. St. Louis, Facts and Comparisons, 1999; Emermann CL, Spenetta J: Pain management in the emergency department. Emerg Med Rep 23:53–67, 2002; and Lawrence R, Rosch P, Plowden J: Magnet Therapy: The Pain Cure Alternative. Rocklin, CA, Prima, 1998.

Potential adverse side effects may include obtundation, sedation, anaphylaxis, nausea, vomiting, rash, respiratory depression, and hypotension. Narcotic antagonists such as naloxone and other emergency resuscitative medications should be available when using opioids in the wilderness, just as in the contemporary clinical setting. Potent opioid analgesics should be given with care to victims with suspected head injury or neurologic illness.57 Narcan (Naloxone) is an opioid antagonist that may reverse narcotic effects. Doses of 0.2 mg intravenously (IV), or 0.4 mg IV, intramuscularly (IM), or subcutaneously, may be given and repeated every 2 to 5 minutes until CNS, respiratory, or hypotensive narcotic symptoms are reversed, to a maximum dosage of 10 mg. Nalmefene is a similar narcotic antagonist but with a longer duration of action. Intravenous dosages of 0.25 µg every 2 to 5 minutes to a total dosage of 1 mg (four doses) may be given.6 Continuous monitoring of blood pressure, mental status, and respiratory status is critical, with possible repeat doses necessary in 1 to 2 hours. Pain may return with narcotic reversal; a balance between pain alleviation and physiologic stability is desired. Additionally, narcotic antagonists may lead to acute narcotic withdrawal symptoms in persons with a tolerance to and dependence on narcotics. Narcotic agonist-antagonist combinations first became popular with pentazocine, which causes less euphoria, but it is abused and so has addictive potential. These agents in general cause less addiction but may depress the brain and respiration,39 which may have special significance in a high-altitude setting where impaired cerebral and pulmonary function may occur. These medications do not provide the narcotic agonist effects needed in narcotic-dependent persons, so they may experience withdrawal symptoms without narcotic agonists. Familiar drugs in this class include buprenorphine, butorphanol, and nalbuphine.

Non-narcotic Analgesics Salicylates. Non-narcotic analgesics provide mild to moderate pain relief and are generally safer than narcotics. Acetylsalicylic acid (aspirin) is a mild analgesic that reduces fever, inhibits platelet function, and diminishes inflammation. It has significant GI effects including gastric irritability, erosion, and bleeding ulcers, so it is often better tolerated in an enteric-coated formulation. Persons who have a history of GI ulcers or severe indigestion should avoid aspirin. Dosage should not exceed 650 mg orally every 4 hours. Other salicylate analgesics include diflunisal, choline magnesium trisalicylate, and salsalate. The latter two have minimal GI toxicity and antiplatelet effects. Salicylates are contraindicated in persons with known allergy to the class of drugs, and in children (less than age 15 years) with viral respiratory illnesses, because their use has been linked to Reye’s syndrome.1 Para-Aminophenols. Acetaminophen is a para-aminophenol that is a mild analgesic and antipyretic.11 It has no antiplatelet, anti-inflammatory, or antiprostaglandin effect, and it is less likely than aspirin to cause serious gastric irritation. The dosage should not exceed 650 mg every 4 hours. Ingestion of more than 10 g over 24 hours may lead to severe hepatic damage; the drug should be used with extreme caution in anyone with preexisting liver disease. Many over-the-counter medications contain acetaminophen, so these should not be used in combination with pure acetaminophen or in persons with liver disease.

Nonsteroidal Anti-inflammatory Drugs Nonsteroidal anti-inflammatory drugs (NSAIDs) are effective for mild to moderate pain and may provide ample clinical benefit without concern for the respiratory depression seen with narcotic analgesics. The mechanism of action is most likely a result of inhibition of prostaglandin-mediated amplification of

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chemical and mechanical irritant effects on the sensory pathways.37 NSAIDs undergo rapid absorption after oral or rectal administration, followed by hepatic metabolism and renal excretion of their conjugated metabolites. Injectable forms of various NSAIDs, such as ketorolac, have also been developed in recent years. This nonsteroidal class of medications includes chemically unrelated compounds that are grouped together because of their therapeutic actions. These include acetic acid, propionic acid, oxicam, and pyrazolone derivatives. Adverse effects of NSAIDs include GI distress and bleeding, CNS disturbances (vertigo, drowsiness), renal dysfunction, and prolonged bleeding from platelet function inhibition. In certain circumstances, NSAID-induced immunosuppression increases propensity to bacterial infection. Indomethacin is an indoleacetic acid derivative with analgesic, antipyretic, and anti-inflammatory (antiprostaglandin) effects. Both rectal and oral administrations lead to rapid absorption. Reasonable caution should be used in persons with hepatic or renal dysfunction. Gastrointestinal toxicity has been reported with its use, including gastric ulceration and perforation, as well as bone marrow suppression. Other acetic acid derivatives include sulindac, tolmetin, ketorolac, and diclofenac. Ibuprofen is a nonsteroidal propionic acid derivative antiinflammatory agent with prostaglandin antagonist activities. It has analgesic and antipyretic properties similar to those of aspirin and acetaminophen, but it may be better for women with dysmenorrhea because its antiprostaglandin effects somewhat relax the uterus. Its anti-inflammatory properties may be very useful for arthritis and acute injuries. Like aspirin, ibuprofen can be a gastric irritant and should be avoided in persons with a history of GI ulcer, indigestion, or hiatal hernia. Oral and rectal administrations lead to rapid absorption. Ibuprofen has been reported to cause nonspecific fluid retention. Although not studied in wilderness medicine research to this point, its potential to aggravate high-altitude illnesses, from acute mountain sickness to high-altitude pulmonary or cerebral edema, should be considered. The usual dosage is 400 to 600 mg every 4 to 6 hours. Other propionic acid derivatives include naproxen, fenoprofen, ketoprofen, and flurbiprofen.11 A newer class of NSAID medications available in the United States is the cyclooxygenase-2 (COX-2) inhibitor group, consisting of celecoxib (Celebrex) and valdecoxib (Bextra), as well as the recently withdrawn medication rofecoxib (Vioxx). Rofecoxib was withdrawn in 2004 as a result of studies showing significant increases in adverse cardiovascular events in patients taking the medication continuously for 18 months.69 These medications inhibit inflammation and also demonstrate analgesic and antipyretic properties. The analgesia offered by COX2 inhibitors is similar to that of other NSAID medications, but the COX-2 inhibitors have less GI toxicity.47 The mechanism of action is believed to be through inhibition of prostaglandin synthesis via inhibition of cyclooxygenase-2. These medications may be taken orally once per day, but they are not cleared for patients younger than 18 years or for patients with advanced renal disease. Elimination is primarily via hepatic metabolism, with little of the drug recovered in the urine. Side effects primarily include GI distress, hypertension, skin rashes, and peripheral edema. The recommended dosage for rofecoxib is 12.5 to 25 mg once daily. Celecoxib may be given either 100 mg twice a day or 200 mg daily (neither method has a clinical advantage over the other). The recent demonstration of adverse

cardiac events shown in patients who are given high dosages of COX-2 may become extended to naproxen and other classes of pain medications as more data are evaluated. Dexketoprofen (Keral) is a recently developed stereoisomer of the NSAID ketoprofen. It is currently available in most of Europe and Central America, and it is being considered for inclusion in the pharmacopoeia of Africa and Asian countries, although it was removed from the market in the United Kingdom in March 2004.7,66 It is a rapidly acting analgesic with fewer GI distress symptoms than most NSAID medications. The eutomer has been separated and the inactive isomer (distomer) has been discarded to potentially reduce unwanted side effects. These changes have resulted in halving the dosage relative to ketoprofen, with similar clinical effects. The usual dosage is 25 mg three times a day, which has been tolerated on an empty stomach. Taking the medication 30 minutes prior to eating may further speed its onset of action.50,65

Dissociative Analgesia Ketamine is a dissociative anesthetic agent that has been demonstrated to provide significant analgesia. Its mechanism of action is probably related to its agonist effects on the glutamate receptor of the N-methyl-d-aspartate (NMDA) subtype.45 NMDA is thought to affect central or peripheral neuropathic pain transmission more than it does nociceptive transmission in tactile or thermal modalities.3,28 Ketamine is believed to activate µ-opioid receptors responsible for analgesia and δ-opioid receptors for dysphoria.21 As a consideration in wilderness settings where respiratory depression may be a significant concern, ketamine may provide significant analgesia, and its dissociative state, with less respiratory depression or loss of glossopharyngeal reflexes. Ketamine possesses sympathomimetic activity that may prove useful in injured persons with depressed cardiac function or shock, and it may also provide bronchodilation for victims with reactive airway disease. It is contraindicated with head injury because it increases intracranial pressure,27 which is caused by increased cerebral blood flow and direct cerebral vasodilation. Cerebral metabolic oxygen requirements increase as well.4 Ketamine is ideally administered by a trained physician with adequate monitoring capability. An intravenous dose of 0.2 to 0.4 mg/kg of ketamine provides analgesia, and 1 to 2 mg/kg IV or 2 to 4 mg/kg IM leads to profound analgesia and a dissociative state. A quiet and calm setting will diminish unpleasant dissociative experiences for the recipient.

Novel Nonopioid, Noncyclooxygenase Inhibitor Analgesics Capsaicin, the crystalline alkaloid in chili peppers (Capsicum species) that causes the heat sensation, has been used increasingly in recent decades for pain management. This odorless, colorless, tasteless alkaloid retains its potency despite time, cooking, or freezing. Capsaicin was discovered by Bucholtz in 1816 and was first synthesized by Spath and Darling in 1930.64 In fact, capsaicin refers to a complex of one synthetic and six naturally occurring and related compounds known as capsaicinoids. These compounds range in potency from mild to extremely hot to the taste or with stimulation of the mucous membranes, potentially producing severe irritation and a numbing sensation. One milligram of pure capsaicin can blister the skin and can give the feeling that a burning hot metal probe has been placed on the skin. On ingestion, the alkaloids are

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Chapter 17: Principles of Pain Management quickly metabolized in the liver and are excreted in the urine within a few hours.64 Sensory neuron depolarization occurs following topical application of capsaicin to the skin, with binding to the vanilloid receptor subtype 1 (VR-1) and a deluge of calcium ions entering the neuron. With continuous application, substance P is depleted at the nerve ending. Thus, although the first topical application of capsaicin usually produces a burning sensation, repeated applications become better tolerated, and analgesia ensues. This commonly requires a day or two of being applied four times per day until the burning sensation ceases. Some find using lower concentrations of the commercial applications allows a more tolerable process until the analgesia is established. Once established, it is important that the patient continue the daily use of capsaicin preparations to maintain the analgesia. If the application is not tolerable, a true detergent or rubbing alcohol is generally needed to remove the cream or gel preparation from the skin.61 Clinical research and practice have shown usefulness of capsaicin product creams and gels for many painful conditions including postherpetic neuralgia, trigeminal neuralgia, atypical facial pain, diabetic neuropathy, arthritis pain, postmastectomy pain, psoriasis, and epicondylitis. Wilderness medical practitioners may encounter travelers using the product on an ongoing basis for these or other conditions or may consider its use for various painful conditions experienced on an expedition. Commercial preparations are commonly found in concentrations of 0.025%, 0.05%, and 0.075%. Contact of these products with mucous membranes should be avoided. Neurotropin is an oral nonopioid, noncyclooxygenase inhibitor analgesic developed in Japan. The preparation contains an extract that is isolated from the inflamed cutaneous tissue of rabbits injected with vaccinia virus. Each tablet contains four neurotropin units of extract; the recommended dosage is one tablet twice daily.29,32 The parenteral preparation has been available in Japan for 50 years, and the oral tablets have been available for 15 years. Although it is not currently available in the United States, it is increasingly marketed and available in other countries and is a viable option for analgesia in patients engaged in wilderness and travel activities in these countries. Neurotropin is indicated in chronic and acute pain, including low back pain, neck-shoulder-arm syndrome, and postherpetic neuralgia. The most common side effects include rash and GI distress, nausea, vomiting, and anorexia. Studies have shown this medication to compare favorably in analgesic quality to ketoprofen. Its mechanism of action is thought to be inhibition of bradykinin release, as well as through the descending pain inhibitory system with effects on serotonergic 5-HT3 and noradrenergic a2 receptors in the spinal dorsal horn. It has demonstrated an increased skin temperature effect in peripheral tissues, but the mechanism of action of this effect is as yet unknown.32

Local Anesthetics Local Anesthetic Pharmacology For centuries, indigenous healers have used coca shrub leaves native to the mountains of the Andes to create a mouthnumbing effect. Gaedicke extracted the alkaloid erythroxylin in 1855, from which Niemann isolated cocaine in 1860.9 Carl Koller first reported using ophthalmic cocaine anesthesia in 1884. Subsequent enthusiasm led to the use of cocaine for anes-

TABLE 17-3. Comparable Anesthetic Dosages* for Peripheral Blocks and Local Infiltration DOSAGE (mg/kg) Amide Anesthetics Lidocaine Prilocaine Etidocaine Mepivicaine Bupivacaine Ester Anesthetics Procaine Tetracaine 2-Chloroprocaine

5 5 4 5 2 5 1–2 5

*No epinephrine included.

thesia of the nasopharynx and oropharynx for surgery of the ear, nose, and throat. Erdtman of Sweden synthesized lidocaine in 1943.9 Local anesthetics (Table 17-3) bind to sodium channels on sensory, motor, and sympathetic fibers and block nerve conduction through sodium-blocking properties in free nerve endings, peripheral nerves, spinal roots, and autonomic ganglia. Normally, the cell’s sodium-potassium pump constantly pumps sodium out of and potassium into the cell to restore membrane ionic gradients. The anesthetic renders the membrane impermeable to the influx of sodium during depolarization, and the nerve cell thus remains polarized. Anesthetic drug binding occurs within the sodium channel after the drug enters the channel from the intracellular side of the nerve membrane.12 Variables such as nerve length, rate of nerve impulse transmission, myelination, and the concentration and volume of local anesthetic determine the rate of onset and extent of therapeutic effect. Anesthetic potency and onset and duration of action depend on factors that include volume, perfusion, edema, lipid solubility, protein binding, and ionization. In general, the S stereoisomer has less toxicity and greater duration than does the R stereoisomer. Anesthetic metabolism and elimination are functions of the specific anesthetic’s chemical structure.12 Lidocaine was the first of the amino amide class of local anesthetics. It is metabolized by hepatic microsomal enzymes. Since its metabolites do not include para-aminobenzoic acid (PABA), allergic reactions are rare. Procaine is a synthetic amino ester local anesthetic. This class of anesthetic is hydrolyzed by cholinesterase to form PABA, which is responsible for the allergic reactions seen with ester anesthetics. Because the esters are relatively unstable, they do not tolerate repeated autoclaving for sterilization.8 Although no studies have specifically addressed the effects of temperature extremes on supplies in wilderness settings, it is prudent to protect these medications from heat as much as is reasonably possible. A local anesthetic may provide relief in a topical application prior to more invasive cleansing and debridement. TAC, a mixture of tetracaine (0.5%), adrenaline (1:2000), and cocaine (11.8%) in saline, may be soaked into a sterile bandage and placed directly over a wound. This combination may provide good analgesia and moderate vasoconstriction.42 However, pediatric deaths and morbidity resulting from cocaine absorption from the aqueous mixture of the original 11.8% cocaine

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solution have been reported, especially when there was mucosal absorption of the mixture. Subsequent studies demonstrated that a 5.9% cocaine mixture was also effective, and further, that a viscous preparation may decrease the likelihood of inadvertent mucosal contact. Vinci and colleagues demonstrated that the 5.9% viscous preparation was safe in 25 pediatric emergency patients when contact with mucosal surfaces was avoided .53 EMLA (the acronym for eutectic mixture of local anesthetics) is a mixture of 2.5% lidocaine and 2.5% prilocaine. After this cream is applied to intact skin under a nonabsorbent dressing for at least 45 minutes, an invasive procedure such as intravenous needle insertion or suturing of a small laceration may be more easily tolerated. EMLA is now available in 5- and 30-g tubes and as a 1-g anesthetic disc for single application.63

Anesthetic Toxicity The blood level of anesthetic after tissue injection depends on absorption, dosage, metabolism, and elimination. Increased tissue vascularity and vasoactivity of the anesthetic greatly affects blood concentration after injection. Infiltration into a highly vascular site, such as around an intercostal nerve and pleura, leads to a more rapid escalation of the blood level than injection into the less vascular subcutaneous tissues. A mixture of anesthetic and epinephrine leads to slower absorption, but this must be avoided when injecting distal extremities and digits, where epinephrine-induced vasoconstriction may lead to acute ischemic injury. Because of the possibility of unintentional direct intravascular injection, all local and regional anesthetic infiltrations should be made after negative aspiration for blood and in small aliquots between aspiration attempts. As anesthetic toxicity levels are approached, common early symptoms include circumoral numbness, tinnitus, and cephalgia. CNS toxicity in the form of seizures occurs at lower anesthetic blood levels than does cardiotoxicity in the form of ventricular arrhythmias and cardiovascular collapse. The CNS effects of lidocaine on the brain are paradoxical. At blood concentrations of 3 to 5 µg/mL, lidocaine is an anticonvulsant, whereas blood concentrations of 10 to 12 µg/mL are associated with seizures. Generally, cardiotoxicity is achieved at approximately 150% of the blood level concentration required for anesthetic CNS toxicity. Bupivacaine has demonstrated increased cardiotoxicity, out of proportion to its increased potency relative to lidocaine.12 Anesthetic allergy per se is uncommon. It is estimated that perhaps 99% of all adverse anesthetic reactions are related to pharmacologic toxicity of the anesthetic or to epinephrine mixed with the agent.12 Ester anesthetic allergies are related to PABA metabolites; therefore, intolerance to PABA-containing sunscreens may indicate allergic tendency to ester anesthetics, although this is somewhat controversial. Allergies to amide anesthetics in preservative-free vials are rare. There is no known evidence of cross-sensitivity between amide and ester anesthetic classes.

Anesthetic Infiltration Techniques and Nerve Blocks Soft tissue analgesia may be accomplished with local injection of 1% lidocaine. Generally, the maximal injectable dosage for lidocaine is 4 mg/kg. Care should be taken to inject from the wound periphery toward the center of the wound to decrease the chance of spreading bacteria or foreign matter to adjacent

tissue.42 In larger wounds, injections should proceed from an area that is previously anesthetized to lessen the discomfort of subsequent injections. Local anesthetic injection typically causes temporary pain because of the pH of the solution. Buffered solutions are available or may be created by the addition of sodium bicarbonate. Sodium bicarbonate (1 mEq/mL) is added to lidocaine or other anesthetic in a bicarbonate to anesthetic ratio of 1:10. Tolerance to the injection will also be improved by gentle and slow injection, which also allows the physician to be prudent with the total dosage of anesthetic. The addition of epinephrine is not generally recommended for soft tissue, although it may provide useful hemostasis, especially in lacerations of the head and scalp. Epinephrine should be avoided on nose tips, ear lobes, distal extremities, and digits to avoid ischemic injury and even subsequent necrosis. Many central and regional nerve blocks require special training, including a thorough knowledge of anatomy and management of potential complications. However, several blocks may be appropriate in a wilderness setting if the physician is cautious and limits the amount of anesthetic injected. All infiltrations should be made after aseptic preparation of the skin whenever possible.

Digital Nerve Block Anesthesia to the digits is easily accomplished with a lowvolume field block to the medial and lateral aspects of the digit at the base of the respective phalanx (Fig. 17-1). The digital nerves should be approached from the dorsum of the hand or foot rather than from the palm or sole. The dorsal digital nerves and proper digital nerves course along the medial and lateral aspects of the digits roughly at the 10 and 2, and at the 4 and 8 o’clock positions, respectively, in a sagittal section of the finger. A volume of 3 to 5 mL lidocaine (0.5% to1.0%) injected as a field block with a 25-gauge (or 27-gauge) needle to the medial and lateral aspects of the proximal digit will give a satisfactory digital block. An epinephrine-containing anesthetic should not be used, as this could lead to circulatory compromise and possible necrosis of the digit.

Wrist Block The entire hand may be anesthetized by blocking the three main nerves at the wrist (Fig. 17-2). The radial nerve at the wrist supplies the cutaneous branches of the dorsum of the hand, the dorsal and palmar aspects of the thumb, and distally to the dorsal aspects of the distal interphalangeal joint of the index finger, the long finger, and the radial aspect of the ring finger. Median nerve sensory distribution includes the palmar surface of the hand, the ulnar aspect of the thumb, and the palmar aspects of the index finger, the long finger, and the radial portion of the ring finger. Median nerve innervation extends dorsally over the index, long, and ring fingers to the distal interphalangeal joint. The ulnar nerve gives sensation to the palmar and dorsal surfaces of the lateral hand, the fifth finger, and the ulnar half of the ring finger.5 To perform this block, a 25-gauge needle is used to inject 2 to 4 mL of 1% lidocaine into the subcutaneous tissue overlying the radial artery. A superficial subcutaneous injection from this point and over the radial styloid will anesthetize cutaneous branches that have emerged from the proximal forearm and that extend into the hand. The median nerve is blocked with 2 to 4 mL of 1% lidocaine just proximal to the palmar wrist crease

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Site of median nerve block

Fourth digital block; Ulnar aspect

Site of radial nerve block

Radial aspect

Flexor carpi radialis tendon

A Flexor carpi ulnaris tendon

Site of ulnar nerve ring block

Figure 17-2. Landmarks for wrist block. (Photo by Bryan L. Frank, MD.) Needle entry sites

to the ulnar artery, which is radial to the flexor carpi ulnaris tendon at the level of the ulnar styloid. Again, a superficial subcutaneous injection from this site and over the ulnar styloid will block cutaneous branches that have emerged more proximal in the forearm and that extend to the hand.46

Ankle Block

Dorsal digital nerve Palmar digital nerve

B Figure 17-1. A, Site of digital nerve block. B, Digital nerve anatomy. (A, photo by Bryan L. Frank, MD.)

between the tendons of the palmaris longus and the flexor carpi radialis muscles. Injection is made deep to the volar fascia. If a paresthesia is elicited (as a result of contact with the nerve), the needle is withdrawn slightly prior to injection. The ulnar nerve is blocked with 2 to 4 mL of 1% lidocaine injected just lateral

Anesthesia of the foot is easily accomplished with blocks of the sensory nerves at the ankle (Fig. 17-3). Using a 25-gauge needle, the deep peroneal nerve, providing sensation between the great and second toes, is blocked with 5 mL of 1% lidocaine between the tendons of the tibialis anterior and the extensor hallucis longus at the level of the medial and lateral malleoli. The needle may be passed to the bone just lateral to the dorsalis pedis artery. The superficial peroneal nerve is injected with 5 mL of 1% lidocaine with a superficial ring block between the injection of the deep peroneal nerve and the medial malleolus. This will block sensation to the medial and dorsal aspects of the foot. The posterior tibial nerve is injected with 5 mL of 1% lidocaine just posterior to the medial malleolus, adjacent to the posterior tibial artery. As the needle is slowly advanced toward the nerve, eliciting a paresthesia by slightly contacting the nerve with the needle will increase the likelihood of success of the block.31 Posterior tibial nerve distribution includes the heel and plantar foot surface. Paresthesias are followed with a slight withdrawal of the needle prior to injection. The sural nerve, providing sensation to the posterolateral foot, is blocked with 5 mL of 1% lidocaine between the lateral malleolus and the Achilles tendon, followed by a subcutaneous infiltration originating from this site and over the lateral malleolus.46

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Site for sural nerve block

Site for superficial peroneal nerve block

A Site for superficial peroneal nerve block

Site for saphenous nerve block

trigger point deactivation may be accomplished with a 27-gauge needle. Injection of a trigger zone is typically performed directly into the painful myofascial point and in a four-quadrant zone from the center of the trigger point. As the needle is advanced in the central point, 0.5 mL of anesthetic is injected and then the needle is withdrawn to where the needle tip is just subcutaneous, and it is then advanced 1 to 2 cm into the adjacent tissue at a 45° to 60° angle from the skin surface in each quadrant from the center point, with 0.5 mL of anesthetic injected at each quadrant. Muscle twitches or fasciculations may accompany the injections, but they need not be sought. A volume of 2 to 3 mL of 1% lidocaine is usually ample for each trigger zone. There is no benefit to adding corticosteroids to the anesthetic. Using an acupuncture needle (or a 27- or 30-gauge needle) may deactivate the trigger zones nicely using a similar four-quadrant pecking of the myofascial zone, without injection of anesthetic. In this technique, the acupuncture needle is simply advanced centrally into the trigger zone and then briskly advanced and retracted several times. Then, as with the injection technique, the needle is partially withdrawn so that the needle tip is just subcutaneous, and then it is redirected to each of the four quadrants around the central point, briskly pecking in each quadrant as at the central point. A 1- to 11/2-inch needle may be used to peck briskly several times in each direction, and also at a 45° to 60° angle from the center of the trigger zone. Depth of insertion is typically 1 to 2 cm. Soiled skin should be prepared as for an intramuscular injection.

Intravenous Regional Anesthesia by Bier Block

B Figure 17-3. Landmarks for ankle block. (Photo by Bryan L. Frank, MD.)

Trigger Point Injections Persons who suffer from neck and shoulder or lower back strain may benefit greatly from deactivation of myofascial trigger zones (Fig. 17-4). The pain relief may be profound and may enable an adventure to continue without disruption. Travell and Simons have extensively described primary and secondary painful points and their referral patterns. Myofascial pain may be intense and may be referred to a large zone of the body.51 Successful deactivation of trigger zones may be accomplished with either dry needling (acupuncture) or injection of 1% lidocaine. In the absence of anesthetic or acupuncture needles,

The Bier block may provide sufficient anesthesia for a physician unfamiliar with the anatomy and technique of a more sophisticated proximal nerve block to stabilize an arm or a leg fracture (Fig. 17-5). Because a tourniquet is necessary, a Bier block should not be used for longer than 60 minutes. A vein of the hand or foot on the extremity to be blocked is cannulated with a 20- to 22-gauge intravenous or butterfly catheter, which is then capped and taped in place. The extremity is then raised above the level of the heart for 1 to 2 minutes to diminish the volume of blood in the distal limb. If tolerated, an Esmarch (rubber) or elastic bandage is wrapped from the hand or foot toward the proximal arm or leg to exsanguinate the limb. If a compression bandage is not tolerated, adequate exsanguination may occur by elevating the extremity for 5 to 10 minutes, or by applying an inflatable splint. A tourniquet is applied and the pressure is held at 50 to 100 mm Hg above systolic blood pressure. In the wilderness, a blood pressure cuff would be an effective tourniquet, or a strap, rope, or tubing may be used. The limb is then placed horizontally for the injection, using 25 mL of 1% lidocaine for the upper extremity and 35 mL for the lower extremity. The anesthetic is slowly infused through the previously inserted intravenous or butterfly catheter at a rate of approximately 0.5 mL/sec. Caution should be taken to avoid extravasation of the anesthetic into the surrounding tissues. Anesthesia will ensue over the first 10 to 15 minutes as the lidocaine diffuses from the intravascular space and binds to the soft tissue. It is important to discontinue the injection if the tourniquet pressure is not maintained during the injection to prevent anesthetic toxicity from an unrestricted intravenous bolus injection. The tourniquet should remain inflated for 60

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4-Quadrant injection technique

Syringe/needle

Figure 17-4. Trigger point injections. Trigger point surface location

Trigger point

Skin

Skin surface view

Subcutaneous tissue Muscle Lateral view

ary amine tricyclic drugs, such as amitriptyline, imipramine, doxepin, and clomipramine, are commonly used for pain problems. Antidepressant medications are presumably effective for treating chronic pain problems because they block presynaptic reuptake of serotonin and/or norepinephrine by the amine pump.2 The drugs are rapidly absorbed after oral administration, although this may be decreased by antimuscarinic effects. They are highly protein bound and have half-lives of 1 to 4 days. They are generally oxidized by the hepatic microsomal system and conjugated with glucuronic acid. Elimination occurs via urine and feces.25 Side effects may include dry mouth, urinary retention, constipation, and hyperactivity.20 Photosensitivity may place wilderness travelers at risk for sunburn, and orthostatic hypotension may lead to falls. Patients with overdoses present with excessive sedation, anticholinergic effects on the cardiac conduction system, significant hypotension, respiratory depression, arrhythmias, and coma. Figure 17-5. Preparation for intravenous regional block using field supplies. (Photo by Bryan L. Frank, MD.)

minutes maximum, at which time most of the anesthetic should be protein bound in the soft tissues. The tourniquet may then be released on a single occasion, whereupon the anesthetic effect will diminish within 5 to 10 minutes.

Adjuvant Pharmaceuticals Pharmaceutical agents other than analgesics and local anesthetics may offer significant relief and may avoid or decrease the potential adverse effects of analgesics and anesthetics.

Antidepressants Wilderness travelers may be taking antidepressant medications for chronic pain or psycho-emotional dysfunction. Continuation of these medications is important to avoid intensification of pain or psycho-emotional lability. Chronic pain conditions that may benefit from antidepressants include migraine cephalgia, postherpetic neuralgia, and diabetic neuropathy. The terti-

Anticonvulsants Of the heterogeneous group of drugs classified as anticonvulsants, nine have been useful as adjuvant medications in pain management: phenytoin, valproic acid, topiramate, levetiracetam, lamotrigene, neurontin, pregabalin, carbamazepine, and clonazepam. Their chemical structures bear little relationship to each other. Serum levels have not been clearly established as useful parameters in pain management. The mechanism of action of each of these drugs is unique and varies from altering sodium, calcium, and potassium flux, to enhancing GABA activity or binding.25 Side effects vary but may include nausea, vomiting, and CNS effects such as drowsiness, ataxia, and confusion. It is important to rule out drug effects as a factor in wilderness-related illnesses. It is not recommended that these drugs be used for acute management of pain in the wilderness.

Antihistamines Antihistamines may be useful as adjuvants in a wilderness travel setting. Specifically, hydroxyzine seems to provide an additive

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TABLE 17-4. Skeletal Muscle Relaxants DRUG Baclofen

DOSAGE (mg)

INTERVAL (hr)

Carisoprodol

3–5 start, increase 8 5 mg every 3 days 350 4–6

Chlorphenesin

400

6–8

Chlorzoxazone Cyclobenzaprine

250–750 10

4–6 12–24

Diazepam

2–10

6–8, variable

Metaxalone Methocarbamol Orphenadrine

800 1000–1500 100

6–8 4–6 8–12

RISKS, PRECAUTIONS Dizziness, ataxia, confusion, severe abrupt withdrawal Dizziness, ataxia, headache, tremor, syncope, severe abrupt withdrawal, contraindicated with acute intermittent porphyria Confusion, headache, dizziness (8 weeks or less); avoid in patients with hepatic disease Dizziness, paradoxical stimulation, rare severe hepatotoxicity Anticholinergic; may cause hypotension, arrhythmias; avoid with MAOI use and in patients with hypertension, CHF, arrhythmia, glaucoma, urinary retention, severe depression, or suicide attempts Dizziness, paradoxical stimulation, cardiopulmonary depression; use only in patients with severe anxiety Hepatic impairment, rash, dizziness, headache; avoid with drug-induced anemia Dizziness, headache, rash Anticholinergic; headache, dizziness

CHF, congestive heart failure; MAOI, monoamine oxidase inhibitors.

analgesic effect in combination with narcotic analgesics, while also lending antiemetic and sedative properties. Hydroxyzine may cause ataxia and disinhibition, and it has, rarely, been associated with convulsions in high dosages.25 A dosage of 50 to 100 mg IM may improve clinical pain management. Similarly, oral antihistamines, such as diphenhydramine 25 to 50 mg, may provide useful adjuvant effects.

Muscle Relaxants Muscle relaxants (Table 17-4) are a diverse group of drugs with similar clinical effects but different pharmacologic properties. They are not true skeletal muscle relaxants in the sense of blocking neuromuscular transmission. Rather, they act by depressing reflexes in a general fashion in the CNS. They are indicated for the relief of muscle spasm related to acute, painful, musculoskeletal injuries. Side effects of these centrally acting muscle relaxants include decreased alertness, motor coordination, and physical dexterity, as well as nausea, vomiting, and abdominal pain. Recent studies have shown muscle relaxants to be effective in the management of low back pain. Efficacy is probably increased when muscle relaxants and NSAID analgesics are used in combination.17 Common centrally acting muscle relaxants include carisoprodol (Soma, 350 mg PO three times a day to four times a day), metaxalone (Skelaxin, 800 mg per os [PO] three times a day to four times a day), and methocarbamol (Robaxin, 1.5 g PO four times a day for the first 48 to 72 hours, then 1 g PO four times a day). The specific mechanism of action of these agents in humans is unknown, but it appears to be related to centrally acting sedation. Cyclobenzaprine (Flexeril, 10 to 20 mg PO three times a day) is structurally related to the tricyclic antidepressant medications. Diazepam (Valium, 2 to 10 mg PO, IM, or IV) is a benzodiazepine that induces calm and anxiolysis via effects on the thalamus and hypothalamus.6 Tizanidine (Zanaflex, 8 mg three times a day) is an α-2 agonist with musclerelaxing properties.

Intra-articular Injections of Hyaluronan Substances Travelers with degenerative osteoarthritis (OA) of the knees may find hiking, trekking, and other wilderness activities very

painful, reducing their ability to participate in these activities. However, some may engage in these activities and experience exacerbation of their symptoms while in a remote or wilderness setting. These exacerbated symptoms may impact the pleasure and safety of the travelers and their companions. OA is felt to be related to decrease in the amount or quality of hyaluronan. Synvisc is a gel-like mixture of hylan A and hylan B polymers (derived from the hyaluronan of chicken combs) and saline. Injection of this “drug-free” hylan complex has proved to be useful to many sufferers of OA, with significant reductions in oral analgesic use. Studies have not demonstrated efficacy in less than a series of three weekly injections; thus, immediate response to injection in the wilderness setting should not be expected.66


HIV/AIDS—SPECIAL WILDERNESS CLINICAL CONSIDERATIONS

With advances in treatment of patients with acquired immunodeficiency syndrome (AIDS) and human immunodeficiency virus (HIV) infection, many are pursuing more activities and living healthier lives than a decade ago. These activities include travel into wilderness and remote locations. For many of these travelers, HIV/AIDS is undertreated and misdiagnosed. An estimated 85% of HIV/AIDS patients receive inadequate therapy, which can significantly reduce their quality of life and options for wilderness travel.68 Patients with HIV/AIDS commonly experience pain, which may include headaches, oropharyngeal pain and odynophagia, earaches, abdominal and chest pain, myalgias, and arthralgias. New or unexplained pains should initiate a medical investigation so that pain therapeutic agents do not mask emerging associated illnesses. Associated diseases that may lead to pain in these patients include neuropathies, postherpetic neuralgia, avascular necrosis of the hip, osteopenia, myopathies, renal calculi, herpes simplex, candida esophagitis, and pancreatitis. Additionally, various diagnostic and therapeutic procedures may initiate or increase pain for these patients. As seen in the peripheral neuropathies of patients with HIV/AIDS, the virus may attack the nerve endings in the extremities, with resulting

Chapter 17: Principles of Pain Management burning, numbness, and dysesthesias. This is often referred to as distal symmetrical polyneuropathy (DSP), and it may prevent or complicate these patients’ wilderness endeavors. Additionally, therapeutic medications may also lead to pain in patients with HIV/AIDS, as is seen with didanosine, dicalcitabine, isoniazid, Videx (ddI), and Zerit (d4T).67,68 Treatment of pain in patients with HIV/AIDS commonly includes oral non-narcotic and narcotic medications. Aspirin, acetaminophen, and NSAIDs are commonly utilized for mild to moderate pain, whereas opioids are the primary therapeutics for severe pain. Many physicians are reluctant to prescribe narcotics to patients because of potential addiction, studies show the risk for addiction in patients with HIV/AIDS to be small. Longer-acting medications, including methadone and timerelease morphine, may offer greater pain management and allow increased wilderness activities. The fentanyl patch transdermal system providing medication release over three days may significantly help those who poorly tolerate oral administration. Adjuvant medications, including caffeine, antihistamines, anticonvulsants, and antidepressants, should be considered so that significant pain relief can be obtained with lower narcotic dosages and thus lower opioid side effects. Persons with a narcotic addiction either prior to or subsequent to narcotic pain management will need to have very strict limits and guidelines set by a specialist in addiction medicine. Drug interactions are of concern, as various anti-HIV medications may interfere with narcotic medications. Ritonavir (Norvin) increases levels of meperidine, propoxyphene, and fentanyl, and efavirenz and nevirapine lower the methadone level. Phenytoin lowers the methadone level and NSAIDs increase the lithium level. These medication interactions are also important to consider for over-the-counter medications, for botanical and herbal remedies, and for illicit drugs as well. Tobacco smoking shortens the half-life of NSAIDs and increases the metabolism of meperidine, morphine, and propoxyphene. Cannabis is known to increase the effect of morphine, ritonavir increases the level of MDMA (methylenedioxymethamphetamine; Ecstasy) and alcohol increases the abacavir (Ziagen) level.67




COMPLEMENTARY AND ALTERNATIVE MEDICINE THERAPIES

425

Figure 17-6. Typical acupuncture needle placement for lateral ankle strain.(Photo by Bryan L. Frank, MD)

Figure 17-7. Typical acupuncture needle placement around injured knee. (Photo by Bryan L. Frank, MD.)

Complementary and alternative are terms used to denote therapies and modalities that may not be supported by Westerndesigned prospective, randomized studies, that are not commonly taught in U.S. medical colleges, or that are not generally covered by traditional health insurance plans.55 Some of these therapies can provide a significant contribution to the management of pain in the wilderness.

Acupuncture Acupuncture developed over the past 3 to 5 millennia in Asia, and it has been practiced over the past several hundred years in the Western world. In many cases, acupuncture developed in geographic areas and under social conditions very similar to the primitive or undeveloped conditions familiar to wilderness travelers. The use of acupuncture by physicians to treat trauma and illness in wilderness settings has been described recently in medical literature.22,24 Properly administered, acupuncture should have a very low risk of morbidity and may be extremely

Figure 17-8. Patient with auricular needles in place. (Photo by Bryan L. Frank, MD.)

effective in alleviating pain and even restoring function to an injured wilderness traveler (Fig. 17-6 through Fig. 17-9). Stux and Pomeranz, and others, have demonstrated endorphin, enkephalin, monamine, and adrenocorticotropic hormone (ACTH) release with acupuncture stimulation.49 Furthermore,

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Tendinomuscular meridian treatment lateral ankle sprain

Box 17-3. Pain Management First Aid Kit* BASICS

Esmarch bandage, 3 × 36 inches Tourniquet Hot and cold gel packs SI 18 Gathering point

ORAL MEDICATIONS

Acetylsalicylic acid (ASA), 500 mg Acetaminophen, 500 mg Carisoprodol (Soma), 350 mg, or metaxalone (Skelaxin), 500 mg Diazepam (Valium), 5-mg tabs Hydrocodone, 5-mg tabs INJECTABLE MEDICATIONS

Local points

Naloxone, two ampules, 0.4 mg each Ketamine, 50 mg/mL, 5 to 10 mL Lidocaine 1%, 30 mL Procaine 1%, 30 mL Midazolam (Versed), 5 mg/mL, 5-mL vial Morphine, 5 mg/mL, 5 mL Meperidine (Demerol), 50 mg/mL, 5 mL TOPICAL THERAPIES

Jing-well (opening) points BL 67, GB 44 (rt)

Figure 17-9. Tendinomuscular meridian treatment for lateral ankle sprain. (From Frank BL: Medical acupuncture in wilderness and Third World settings.Wilderness Med Lett 14:1, 1997.)

the gate theory of pain modulation and altered sympathetic activity33 may apply as well. Clinically, improved microvascular circulation may lead to decreases in tissue edema, which in turn may diminish pain and aid in restoring function. Release of ACTH leads to increased circulating corticosteroids; decreased inflammation may contribute to decreased pain and improved healing.30 Contemporary medical acupuncturists are typically trained in a variety of styles or traditions. Many physicians utilize a combined approach of acupuncture point selections based on neuroanatomy and those that are felt to have energetic effects in the body. Additionally, acupuncture microsystems are often employed, in which the entire body is represented in a small area such as the ear, scalp, or hand. These microsystems are often quite beneficial for acute pain relief (see Figure 17-8).24 Sterile acupuncture needles are compact, lightweight, and easy to include in a daypack or first-aid kit (Box 17-3). Integration of acupuncture into the biomedical care of wilderness trauma, pain, and illness may dramatically enhance patient comfort and facilitate extrication from a remote setting. For example, a common clinical case that often responds to acupuncture is a sprained ankle. An energetic style of acupuncture that is especially useful for common trauma utilizes the tendinomuscular meridians (TMMs) of the acupuncture energetic subsystems. The indications for activation of the TMMs treatment include acute strains, sprains, abrasions, and hematomas. The method of activation for this style of treatment is to place a needle in the “Jing-well” or “Ting” point of one

Arnica cream, 5-mL tube Capsaicin ointment, 2-g tube TAC (mixture of tetracaine [0.5%], adrenaline [1 : 2000], and cocaine [11.8%] in saline), 10 mL† Biomagnets (200 to 800 gauss), two to four small ADDITIONAL SUPPLIES

Intravenous (IV) cannula, 20-gauge, three IV cannula, 18-gauge, three IV tubing, two Normal saline, 500 mL IV D5LR (5% dextrose in lactated Ringer’s), 500 mL Acupuncture needles, 50 *Items subject to training and scope of practice. This pain kit is in addition to regular first-aid kit. † EMLA (2.5% lidocaine and 2.5% prilocaine) should be used if there is a concern for cocaine toxicity.

to three of the meridians involved in the lesion. This is followed by placing a needle in the “gathering point” for the meridians, then by placement of needles around the area of induration, swelling, or bruising, approximately 1 cm out from the edge. All needles in this treatment are placed only 2 to 3 mm deep and are left in place for 20 to 45 minutes. Commonly, a lateral ankle sprain involves both the gallbladder and bladder TMM zones. The Ting (Jing-well) points for these meridians are at GB 44 and BL 67 on the lateral angles of the fourth and fifth toes, respectively. The gathering point for these meridians is at SI 18, just below the zygoma in line with the lateral canthus. Locally, four to six needles are typically placed around the swelling or ecchymosis of the ankle sprain (see Figure 17-9). Recovery from the sprain may proceed much more rapidly with this acupuncture input than with the conventional therapies of rest, ice, compression, and elevation (RICE) alone. Failure to achieve 70% to 85% or greater decrease in pain over 24 to 48 hours may alert the medical

Chapter 17: Principles of Pain Management acupuncturist that an injury is more serious than initially appreciated. Most acupuncture treatment requires substantial training to be responsibly integrated with conventional Western therapies. National and international standards of training have been established for Western-trained physicians who desire to incorporate acupuncture into their traditional medical practices. The American Academy of Medical Acupuncture (AAMA) is the professional organization representing U.S. physician acupuncturists whose training meets or exceeds standards established by the World Health Organization’s affiliate, the World Federation of Acupuncture and Moxibustion Societies. Physicians interested in learning acupuncture may contact the AAMA (www.medicalacupuncture.org) for information on training programs designed specifically for physicians. The National Commission for Certification of Acupuncture and Oriental Medicine provides testing and resources primarily for U.S. nonphysician acupuncturists.23 The International Council of Medical Acupuncture and Related Techniques (ICMART) is composed of approximately 84 physician acupuncture organizations from around the world and provides international educational congresses and symposia.

Herbal and Botanical Remedies The term herb is broadly defined as a nonwoody plant that dies down to the ground after flowering. The term botanical is a more general description of flora, although common interpretation describes any plant used for medicinal therapy (see Chapter 60), nutritional value, or food seasoning or dyeing (coloring).14 The use of botanicals, like the use of acupuncture, may be encountered in wilderness travels as a part of the indigenous culture and medical care. Botanicals are often prepared as infusions, with the plant’s soft portions placed in a pot and covered by boiling water to create a supernate. Herbal decoctions are traditionally prepared in special earthen crocks or in containers of stainless steel, ceramic, or enamel by contemporary practitioners, specifically avoiding aluminum and alloyed metal pots. The herb is placed in the container and covered with cold water that is then boiled, covered, and simmered. Travelers may encounter an herbal remedy intended to be applied to the skin, dispensed as a poultice, a botanical liniment, an ointment, or an oil. Alternatively, many modern herbalists utilize capsule forms of herbs for ease of administration. Combinations of several herbs are often more effective than a single herb, and common formulas have been recorded worldwide for centuries.33 Appropriate application or prescription of botanical products rarely leads to toxicity or adverse reactions, although such are possible if botanicals are used excessively or carelessly. Botanical products that have been used for pain include morphine, isolated from the opium poppy, and cocaine, from coca leaves (Erythroxylum coca). Often used as a seasoning or food, oregano (Origanum vulgare) has been reported to be beneficial for rheumatic pain.33 Sunflower (Helianthus annuus) is a source of phenylalanine, useful for general pain. Turmeric (Curcuma longa) contains curcumin, an anti-inflammatory substance that is beneficial for rheumatoid arthritis, and ginger (Zingiber officinale) is beneficial for rheumatoid arthritis, osteoarthritis, and fibromyalgia. Clove (Syzygium aromaticum) is endorsed by the German botanical resource, Commission E, topically for dental pain, and red peppers (Capsicum species) contain substance P–depleting capsaicin and also salicylates. Often taken as an infusion or decoction, kava kava (Piper methysticum) contains

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both dihydrokavain and dihydromethysticin, which have analgesic effectiveness similar to that of aspirin. Evening primrose (Oenothera biennis) is a great source of tryptophan and has been demonstrated to relieve pain associated with diabetic neuropathy. Lavender (Lavandula species) contains linalool and linalyl aldehyde, which appear to be useful, in topical and aromatherapy form, for pain of burns and other injuries.14 Willow (Salix species), which has been used to treat pain since 500 bc, contains salicin and other salicylate compounds. Commission E has recognized willow as an effective pain reliever for headaches, arthritis, and many other pains. Other salicylate-containing plants include wintergreen and birch bark. All botanicals containing salicylates should be avoided in persons who are sensitive or allergic to aspirin products. Furthermore, children who have viral infections such as a cold or influenza should avoid these products, as salicylates have been implicated in the development of Reye’s syndrome.14 Chamomile (Matricaria chamomilla) contains chamazulene, which is reportedly beneficial for abdominal pain related to GI spasm or colic. As an antihistaminic, it has mild calming or sedative properties. It is used in Europe to treat leg ulcers and may be beneficial for painful, irritated bites and stings.14 Plantain major (Plantago major) is also commonly useful for bites and stings, poison ivy discomfort, and toothache, and it has been used traditionally by Native Americans as a wound dressing. Aloe gel (Aloe vera) has been used since ancient times to treat burns and sunburn and to promote wound healing. Especially useful for sprains and strains is the mountain daisy or arnica (Arnica montana), which is also endorsed by the German Commission E. Arnica was in the U.S. Pharmacopoeia from the early 1800s to the 1960s, and it has long been used by Native Americans and others for relieving back pain and other myofascial pains and bruising. It is used topically or internally, often in homeopathic form. Comfrey (Symphytum officinale) has been used since ancient Grecian times for skin problems.15 It contains alloin, which is anti-inflammatory, and is endorsed by Commission E to topically treat bruises, dislocations, and sprains. Comfrey has experienced a controversial safety record because oral ingestion of its pyrrolizidine alkaloids has been associated with hepatotoxicity and carcinogenicity.14 For this reason, only topical use of comfrey is recommended.

Magnet Therapy Magnet therapy has been described for approximately 4000 years in the Hindu Vedas and the Chinese acupuncture classic, Huang Te Nei Ching. The application of magnetic stones, or lodestones, is said in ancient legends of Cleopatra and others to have decreased pain and preserved youth. Early Romans used the discharge of the electric eel to treat arthritis and gout.35 Danish physicist Oerstad proved in 1820 that an electric current flowing through a wire had its own magnetic field. (In modern medicine, the most familiar use of magnetic energy is in magnetic resonance imaging.) There are various theories about the effectiveness of permanent magnets for use in pain and healing. Lawrence and coworkers reported increased blood circulation and increased macrophage activity,35 and others have hypothesized effects on peripheral nerves, including blockage or modification of sensory neuron action potentials and enhanced regeneration of peripheral nerves.36,40,43,54 Most permanent magnets marketed at this time for management of pain are approximately 200 to 1200 gauss in strength. At this level, there is little, if any, risk in trying a magnet for

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pain reduction, assuming the patient is properly evaluated to provide other care when appropriate. This author has seen the benefits of magnets in his pain medicine practice over many years. Many patients report significant pain reduction within hours; others report relief after wearing the magnets for a week or more. In wilderness travel, it is reasonable to carry a few therapeutic magnets, as they are usually lightweight, compact, and unbreakable. Magnets marketed for pain therapy range in size from a 2-inch (5 cm) circle to a 6- by 12-inch (15–30 cm) rectangular pad. Most are only a few millimeters thick, and they

18

are often flexible. These are becoming more readily available through multilevel marketing, television infomercials, health food stores, and the internet. Some people have also experienced pain relief with simple, small magnets such as those used to place notes and photographs on a refrigerator. The magnet should be placed directly over the area of pain, and it can be held in place with tape, clothing, or straps. The references for this chapter can be found on the accompanying DVD-ROM.

Bandaging and Taping Daniel Garza

Taping and bandaging are both useful skills in wilderness medicine. Taping can be used to support injured joints and soft tissues; bandaging is most often used to secure a wound dressing (Fig. 18-1). Bandaging with an elastic wrap is an alternative to taping and, over larger joints, such as the knee, is often preferable. In general, taping requires practice, but some simple techniques can be easily mastered. It is most often utilized in mild to moderate sprains and strains, where some functional capacity such as weightbearing and lifting are maintained. Although taping offers dynamic support, it is in no way comparable to splinting, which can immobilize an extremity. The most common tape applied is white athletic (or adhesive) tape, often used by trainers in organized sports. Athletic tape may be applied to skin, although it may lose adhesion if the body part is not shaved and tape adhesive not applied. Some keys to successful taping include the following: • Avoid leaving any gaps in the tape because these will lead to blisters. • Avoid excessive tension on tape strips that serve to fill these gaps. • Apply tape in a manner that follows the skin contour to avoid wrinkles. • Try to overlap a half-width on successive strips. Bandaging is accomplished by either elastic wraps or gauze rolls of various widths. Once a dressing is applied to a wound, appropriate bandaging allows the patient to feel confident that it will remain secure throughout reasonable amounts of activity. Regardless of the method used, it is important to remember that taping and bandaging, especially when circumferential, should not be so tight as to limit circulation. Signs and symptoms of overly tight application are similar to a mild compartment syndrome, classically characterized by the five P’s:

Pain Pallor Paralysis Pulselessness Paresthesias


TAPING Types of Tape Athletic tape is composed of fibers woven into strips that are coated with zinc oxide, an adhesive compound. Although most commonly colored white, athletic tape is available in a variety of colors. This is the most commonly used tape in athletics and first aid for support and prevention of injury. It is available in a variety of widths. Although the major advantage of athletic tape is versatility, its major disadvantage is the tendency of zinc oxide to lose adhesive properties with heat and moisture, thus resulting in loss of support when the patient sweats. There are a variety of techniques used to increase the durability of athletic tape under these conditions, described later in this section. Elastic tape (e.g., Elastikon by Johnson & Johnson) is cotton elastic cloth tape with a rubber-based adhesive. The elasticity of the tape allows for greater flexibility and is particularly useful for large joints such as the knees or shoulders.

Skin Preparation Skin preparation involves measures meant to increase longevity of tape adhesion and patient comfort. If tape is to be applied directly to the skin, the area is usually shaved to remove hair that may interfere with direct contact. Care must be taken to avoid small abrasions in the skin when shaving because these can serve as sites of infection. If the area cannot be shaved in a clean and deliberate manner, it may be advisable to avoid. Any

Chapter 18: Bandaging and Taping obvious abrasion should be covered with a thin layer of gauze or small adhesive strip before taping. There are a variety of commercially available skin adhesives in aerosolized form. These preparations use benzoin as the adhesive. One example is Cramer’s Tuf-Skin. Skin adhesives are applied after the skin has been shaved and abrasions dressed. If the area is not shaved, a foam underwrap or prewrap is used to protect body hair. Prewrap is generally supplied in 3-inch rolls in a variety of colors. After applying a topical skin adherent, such as Tuf-Skin, prewrap is applied over the part to be taped in a simple, continuous circular wrap. The prewrap is sufficiently self-adherent that it does not need to be taped down. Heel-and-lace pads and foam pads are used to provide greater comfort by relieving potential pressure points. When tape is

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applied over bony prominences, it can create tension on the skin surface that leads to blistering. Heel-and-lace pads are prefabricated pieces of white foam that are stuck together with petroleum jelly and then applied to the anterior and posterior aspects of the talus when the ankle is taped. Pads of foam can be cut to size to fit over painful areas that need to be taped, as in medial tibial stress syndrome, or to be used for support in special cases, such as taping for patellar subluxation.

Ankle Taping The most common injury to the lower extremity while hiking is a sprained ankle. It is usually the result of inverting the ankle on an unstable surface. Pain and swelling linger for several days, and taping can help offer support if the patient is able to bear weight. Because most injuries occur to the lateral ligaments, taping supports the lateral surface by restricting inversion. In general, taping of the ankle consists of anchor strips on the lower leg and foot, stirrups that run in a medial to lateral direction underneath the calcaneus, and support from either a figure8 or heel-lock technique (Fig. 18-2). The heel lock requires some expertise to perform, so most operators are more comfortable with the figure-8 initially.

Toe Taping Taping toes that are sprained or fractured is simple and effective. This treatment involves “buddy-taping” to the adjacent toe with one or two pieces of tape to provide support. A piece of gauze, cotton, or cloth can be placed between the toes to avoid skin breakdown. A sprain of the first metatarsophalangeal joint, also known as “turf toe,” can be a chronic and painful condition. Taping for turf toe attempts to support and stabilize the joint and is described in Figure 18-3.

Lower Leg Taping Figure 18-1. Athletic tape (front row) and elastic bandages (back row) come in various sizes.

A

Medial tibial stress syndrome, commonly referred to as “shin splints,” can be taped for support and comfort. Tape is brought

B

Figure 18-2. Ankle taping. A, (1) Ankle at 90 degrees;(2) apply anchors of 1.5-inch tape at the lower leg and distal foot. B, (3) Apply 3 stirrups from medial to lateral in a slight fan-like projection.

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C

D

E

F

G

H

Figure 18-2, cont’d. C, (4) Fill in gaps with horizontal strips. D, (5) Begin figure 8. Apply tape across front of ankle in left-to-right direction. E, (6) Continue under the foot to the opposite side and cross back over the top of the foot.F, (7) Complete by wrapping around the leg and end at the anterior aspect of ankle.G, (8) Apply heel locks for both feet (omit if not familiar with this technique). Start in left-to-right direction and apply tape across front of joint. H, (9) Wrap around the heel (bottom margin of tape should be above the superior edge of the calcaneus) to form the first heel lock.

Chapter 18: Bandaging and Taping

I

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J

Figure 18-2, cont’d. I, (10) Continue under the foot to the opposite side and cross back over the top of the foot.J, (11) The tape is then brought back around the superior margin of the calcaneus and down and around the heel. K, (12) Finish by wrapping around the ankle. Repeat figure 8 or heel lock as desired.

K

from a lateral to medial direction, and a small foam pad can be cut to cover the area of tenderness. Underwrap should be used over a foam pad to secure it in place (Fig. 18-4).

piece of foam into taping the knee can help relieve symptoms. As with all taping around the knee, underwrap should not be used (Fig. 18-6).

Knee Taping

Finger Taping

Because it is a large joint, taping the knee requires expertise and special consideration. Underwrap should not be used because adequate traction to support the joint can only be achieved by taping directly to the skin. The patient’s knee should be shaved 6 inches above and below the joint line. In addition, standard athletic tape should not be used because it cannot provide enough support. Three-inch elastic tape provides the foundation. Taping for injuries to the medial aspect of the knee is described in Figure 18-5.

Patella Taping Subluxation of the patella is exacerbated by the stress of walking long distances across uneven terrain. Incorporating a

Injuries to the fingers are common in a variety of outdoor settings. Both simple fractures and sprains can be initially treated by taping. The most common scenarios involve fingers that are hyperextended or that are “jammed.” Injuries in this scenario are often to the palmar ligaments and tendons. Patients may find it difficult to flex the finger against the resistance of an examiner’s finger or may demonstrate tenderness over the palmar aspect of the finger. Swelling is almost always present and may be difficult to localize. This presentation is also seen after reduction of a dorsal dislocation of the proximal interphalangeal joint. In all these cases, it is always best to splint or tape the finger in slight flexion to avoid further injury to the flexor apparatus.

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1. Apply two anchors: First anchor around IP joint of first toe with 1-inch tape. Second anchor around midfoot with 11/2-inch tape. 2. Apply strip of 1-inch tape from distal to proximal anchor along medial aspect.

3. Continue with a strip of 1-inch tape from lateral edge of distal anchor along plantar aspect of first MTP joint to medial aspect of proximal anchor.

4. Cross with a strip of 1-inch tape extending from the medial aspect of the toe to the plantar aspect of the proximal anchor.

5. Begin dorsal strips by applying 1-inch tape from medial aspect of distal anchor across the dorsal aspect of the MTP joint to the proximal anchor.

6. Cross over the previous strip by applying 1-inch tape from lateral aspect of distal anchor to medial aspect of proximal anchor.

7. Close with 1-inch strips around the toe and 11/2-inch tape around the forefoot.

Figure 18-3. Toe taping.

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1. (Optional) Underwrap is applied over a foam pad.

Figure 18-4. Lower leg taping. 2. With the patient placing his or her heel on a rock or roll of tape, begin applying 11/2-inch tape from the superior margin of the malleoli to the calf.

Fingers are buddy-taped to the adjacent finger as a natural splint (Fig. 18-7). The second and third fingers and fourth and fifth fingers are always paired. If the third and fourth fingers are paired, this makes injury to the second and fifth fingers more likely with subsequent activity. A small piece of gauze, cotton, or cloth should be placed between the fingers to avoid blistering or pressure on a tender joint. Strips of tape should be applied around fingers but not over the joints. Although not as common, injuries to the extensor tendons can occur. Typically these occur with hyperflexion, but they can also occur with hyperextension and axial loading.1 A mallet finger results from fracture of the base of the distal phalange, the site of attachment for the extensor tendon. The resulting inability of the distal phalange to extend fully results in a partially flexed “mallet” finger. Injuries in which the extensor mechanism is clearly disrupted should be treated with the finger taped in full extension. Often a straight splint, such as a tongue blade or smooth stick, can be placed on the dorsal surface and the finger taped to it for additional extensor support (Fig. 18-8). Any injury to the fingers or hands should always be evaluated by a physician, who can determine whether radiographs are necessary. Given the importance of maintaining optimal function of the hands for one’s personal and professional activities, this point cannot be overemphasized.

Thumb Taping The thumb is frequently injured when placed in extreme extension or abduction, such as occurs when it is caught in the strap of a ski pole when falling. Taping can prevent reproducing the mechanism of injury, particularly when grasping an object (Fig. 18-9).

Wrist Taping Wrist sprains generally occur during falls and initially can be difficult to distinguish from fractures. Although splinting is initially the most desirable treatment, there are two basic taping approaches that can be used, depending on the nature of the injury. As with the finger, the most important factor is whether the injury occurred in hyperextension or hyperflexion. Anchors are placed around the palm and distal wrist, whereas support strips to prevent undesirable movements are placed on the palmar aspect for hyperextension injuries or dorsal aspect for hyperflexion injuries (Fig. 18-10).

Elbow Taping The two most common soft tissue injuries to the elbow result from hyperextension and from excessive valgus force. Each of these injuries can result in significant ligament and tendon injury. Taping techniques are meant to prevent reproducing painful movements while maintaining function. Because these techniques allow for substantial joint movement, underwrap

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1. The patient maintains the knee in slight flexion (10 –15 degrees) by placing the heel on a small stone or cap of a spray can.

2. Apply two anchor strips of 3-inch elastic tape 6 inches above and below the joint line.

3. Apply a strip of 3-inch elastic tape from the anterolateral aspect of the lower leg, across the knee joint and up to the posteromedial aspect of the thigh.

4. Apply a second strip from posterior calf to anterior thigh, forming an X.

Figure 18-5. Knee taping.

5. Repeat steps 3 and 4 twice.

6. Apply two additional anchor strips of 3-inch elastic tape 6 inches above and below the joint for closure.

7. (Optional) Wrap a 6-inch elastic bandage from mid-calf to mid-thigh to cover the tape and provide additional support.

Chapter 18: Bandaging and Taping

1. Cut a piece of foam into a C shape, measured to encircle half of the patient’s patella.

2. The patient maintains the knee in slight flexion (10–15 degrees) by placing the heel on a small stone or cap of a spray can.

3. Apply two anchor strips of 3-inch elastic tape 4 inches above and below the patella.

Figure 18-6. Patella taping. 4. Apply the foam pad cut to fit the patient’s patella. Elastic tape (3-inch) is applied in a manner that reproduces the curvature of the foam pad.

5. Starting from the medial aspect of the lower leg anchors, bring the elastic tape around the lateral aspect of the patella and back to the medial aspect of the upper leg anchors.

6. (Optional) Wrap a 6-inch elastic bandage from mid-calf to mid-thigh to cover the taping and provide additional support.

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Figure 18-7. Buddy-taping of fingers.

A

B A

C B Figure 18-8. A and B, Extension taping of finger with small splint.

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Figure 18-9. Thumb taping. A, (1) Using 1.5-inch athletic tape, wrap an anchor strip around the wrist.B, (2) Using 0.75-inch tape,start at volar aspect and continue along the dorsal aspect of the thumb towards the first web space.C, (3) Allow the patient to crimp the tape as it comes across the web space and continue around base of thumb.

Chapter 18: Bandaging and Taping

D

E

F

G

H

I

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Figure 18-9, cont’d. D, (4) Bring the tape around to the volar aspect of the wrist and tape at that point.To complete a thumb spica, apply several more strips in succession.To reinforce, rather than repeating a series of strips, continue as follows. E, (5) Apply an anchor strip from volar to dorsal aspects of wrist through the first web space (note crimping). F, (6) Apply strip from dorsal to volar aspect of anchor strip. G, (7) Apply successive strips until at wrist. H, (8) Add a finishing anchor strip through first web space. I, (9) Complete with anchor strip at wrist.

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A

B

C

D

Figure 18-10. Wrist taping. A, (1) With the hand wide-open, apply one anchor across the palm of the hand and two to three anchors across the distal forearm. B, (2) Measure out the distance between the two anchors and construct a fan of three strips at varying angles on a smooth surface. C, (3) For hyperextension injuries, apply these support strips to the palmar aspect. For hyperflexion injuries, apply them to the dorsal aspect. D, (4) Apply another set of anchors over the support strips.

should not be used, and tape should be applied directly to skin to allow for maximal adhesion. Taping for a hyperextension injury employs a fan of elastic or tape, similar to that used in the wrist, to prevent excessive extension (Fig. 18-11). Individuals who have suffered a valgus stress injury require reinforcement from elastic tape placed on the medial aspect of the elbow (Fig. 18-12).

Injuries to the acromioclavicular joint most commonly occur when a patient falls on the lateral aspect of the shoulder. Enough force is transmitted through the acromioclavicular ligament to stretch or tear it, resulting in a sprain, or “separated shoulder.” Tape must be applied directly to the skin (Fig. 18-13).

Shoulder Taping


BANDAGING

Taping the glenohumeral joint is rarely done, primarily because it results in so significant a restriction of movement that the patient cannot function effectively. As such, taping offers little advantage over a sling. Taping of the acromioclavicular joint, however, can be effective in reducing pain and maintaining adequate function at the glenohumeral joint.

Bandaging may be used to wrap and support an injury or to help dress a wound. Many of the techniques described in the section on taping, such as figure-8 patterns, are used in bandaging.

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1. The arm is supinated and extended just short of where pain is experienced. Apply anchors with 3-inch elastic tape 4 inches above and below the elbow.

2. Apply 3-inch elastic tape from distal to proximal anchors that form an X over the antecubital fossa. A total of four strips should be applied.

Figure 18-11. Elbow taping. 3. Apply closure strips above and below the elbow over the original anchors.

4. (Optional) Apply a 4- or 6-inch elastic bandage from distal to proximal to secure the taping.

Types of Bandages The type of bandage used depends on its purpose. Elastic bandages (e.g., Ace wrap) come in a variety of widths and are used to wrap injuries such as sprains and strains. These bandages generally come with separate clips or clips built into the bandage to secure it. Of note is the double-length 6-inch elastic bandage that is useful for wrapping large joints such as the knee and shoulder. Bandaging wounds generally involves rolled gauze or cottonbased wraps that secure a dressing in place. These wraps are more desirable than elastic bandages in wound care because they do not place as much tension on the wound dressing. A triangular bandage, which is often used to create a sling, can be folded two to three times into a strap, called a cravat (Fig. 18-14). Cravat dressings are useful for applying pressure to a wound that is bleeding to promote hemostasis.

In the discussion of bandaging different parts of the body later in this chapter, the method for using an elastic bandage is described. When securing a wound dressing, the same methods may be used, except that rolled gauze or cotton bandages should be substituted. If there is a special technique for wound care, it will be described separately.

Securing Bandages Because bandages are not adhesive, they must be secured with tape or clips, or by tying them to the body. Two techniques for tying off a bandage are as follows: 1. As you are finishing wrapping with a bandage, bend the free end backward over your fingers, creating a loop. Now double back around the body part and tie the remaining free end to the loop to secure the bandage2 (Fig. 18-15).

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1. The arm is supinated and flexed to approximately 30 degrees. Apply anchors with 3-inch elastic tape 4 inches above and below the elbow.

2. Apply 3-inch elastic tape that forms an X over the medial joint line. The first strip begins at the posterior aspect of the proximal anchor and crosses to the anterior aspect of the distal anchor. The second strip begins at the anterior aspect of the proximal anchor and crosses to the posterior aspect of the distal anchor.

Figure 18-12. Elbow taping (valgus stretch injury).

Apply a total of four strips. 3. Apply closure strips above and below the elbow over the original anchors.

4. (Optional) Apply a 4- or 6-inch elastic bandage from distal to proximal to secure the taping.

2. As you are finishing wrapping, tear or cut the remaining portion of bandage lengthwise down the middle. Double back with one of the resulting strips and tie off.

Ankle and Foot Bandaging Ankle bandaging with a 2- to 3-inch elastic wrap can be used to support a sprain. The bandage can be applied over a sock or directly to the skin. It is usually simplest to use a series of figure8 wraps, or, if preferable, a series of heel locks as described in the section on ankle taping. Anchors and stirrups are not used. When bandaging the foot, the same technique should be carried out to the metatarsophalangeal (MTP) joint. Circumferentially bandaging the foot by itself will result in the bandage slipping, as opposed to bandaging the ankle as well.

Knee Bandaging A double-length 6-inch elastic bandage can provide support to the knee. Ask the patient to hold the knee in slight flexion by placing his heel on a small stone or piece of wood (Fig. 18-16A). The elastic wrap is then applied circumferentially from midquadriceps to mid-calf (see Fig. 18-16B). If using gauze to secure a dressing or a smaller elastic wrap, then a series of figure-8 wraps can be applied, leaving the patella exposed.

Thigh and Groin Bandaging Quadriceps, hamstring, and hip adductor (“groin”) strains can all be treated with an elastic bandage in a hip spica. The bandage is modified slightly for the groin strain (Fig. 18-17).

Chapter 18: Bandaging and Taping

1. Apply three anchor strips with 3-inch elastic tape. Place the first anchor around the midhumerus. Place the second anchor beginning inferior to the nipple anteriorly and around to the inferior tip of the scapula in the posterior. Apply the third anchor from the anterior portion of the second anchor, over the trapezius and extending to the posterior portion of the second anchor. Note that a 3-inch gauze pad is incorporated into this anchor to protect the nipple. 2. Apply a longitudinal strip of 3-inch elastic tape from the anterior aspect of the first anchor, over the acromioclavicular joint and ending on the posterior aspect of the third anchor.

Figure 18-13. Shoulder taping.

3. Apply the next strip overlapping two thirds of the third anchor laterally. It should extend from posterior to anterior portions of the second anchor and cross over the acromioclavicular joint.

4. Apply the next strip from the posterior aspect of the first anchor, over the acromioclavicular joint and ending at the anterior aspect of the third anchor.

5. Repeat steps 2 through 4 two more times. (Optional) Wrap a 6-inch elastic bandage in a shoulder spica for additional support. (See Bandaging section.)

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A Figure 18-14. Making a cravat from a triangular bandage. (Redrawn from Auerbach PS: Medicine for the Outdoors, 4th ed. Guilford, CT, Lyons Press, 2003. p 262.)

A

B

Figure 18-15. A and B, Securing a bandage. (Redrawn from Donelan S: That’s a wrap: Wound bandaging made easy. Ski Patrol Magazine 2005;Winter: 63.)

Although the quadriceps and hamstring can be supported by wrapping only the leg with a 6-inch elastic bandage, the hip spica helps prevent slipping and provides additional support.

Wrist and Hand Bandaging Support to the wrist can be supplied by a 2- to 3-inch elastic wrap using a continuous technique (Fig. 18-18). This same technique can be used with gauze to secure a dressing to a wound that can occur when falling on an outstretched hand. A hand cravat bandage can be used for wounds that continue to bleed despite manual pressure2 (Fig. 18-19).

Finger Bandaging Finger wounds are generally easily treated with adhesive bandages. However, if size or degree of bleeding necessitates a larger dressing, then the following method may be used: Fold a 1-inch rolled gauze back and forth over the tip of the finger to cover and cushion the wound (Fig. 18-20). Then wrap

B Figure 18-16. A, Knee positioned in slight flexion with heel-lift while bandage is applied. B, Completed knee bandage.

the gauze around the finger until the gauze is snug. On the last turn around the finger, pull the gauze over the top of the hand so that it extends beyond the wrist. Split this lengthwise; tie the ends around the wrist to secure the bandage.

Thumb Bandaging Application of a bandage or dressing to the thumb usually involves a thumb spica, as described in the taping section. Rather than apply individual strips, the gauze or elastic bandage is looped continuously.

Shoulder Bandaging A shoulder spica is used to support shoulder sprains, strains, and subluxations (Fig. 18-21). A triangular bandage can be used to dress a shoulder wound (Fig. 18-22).

Chapter 18: Bandaging and Taping

1. Wrap a double-length 6-inch elastic bandage around the mid-thigh in a medial to lateral direction and continue proximally.

2. At the groin crease, continue up and around the waist once to help anchor the bandage.

Figure 18-17. Thigh and groin bandaging. 3. Return to the thigh to complete the figure-ofeight. For quadriceps and hamstring strains, concentrate on wrapping the leg, using an additional figure-of-eight to anchor the wrap. For groin strains, concentrate on supporting the hip adductors by alternating wrapping the leg with figure-of-eight wraps.

4. Finish wrap on the leg.

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A

B

C

D

Figure 18-18. Wrist bandaging. A, (1) Begin by encircling the wrist 2 to 3 times. B, (2) Continue across the dorsum of the hand, through the first web space and around the base of the proximal phalanges. C, (3) Continue down and across the dorsum of the hand. D, (4) Circle the wrist and bring across the dorsum of the hand to form a figure-8. E, (5) Repeat, alternating figure-8 patterns on the dorsum of the hand and secure at the wrist.

E

Chapter 18: Bandaging and Taping

1. After dressing the wound, the patient closes his fist around rolled gauze.

2. Starting from the anterior aspect of the wrist, wrap one end around the dorsum of the hand, over the fingers and back to the wrist.

3. With tension, wrap the other end around the dorsum of the hand, over the fingers and back to the wrist, creating an X.

Figure 18-19. Hand cravat bandage. (Redrawn from Donelan S:That’s a wrap:Wound bandaging made easy. Ski Patrol Magazine 2005;Winter: 66.) 4. Cross both ends around the wrist.

5. Tie the ends to secure the dressing.

Figure 18-20. To begin a finger bandage, place layers of gauze over the fingertip. (Redrawn from Auerbach PS: Medicine for the Outdoors, 4th ed. Guilford, CT: Lyons Press, 2003, p 263.)

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1. Begin by encircling the mid-humerus with a double-length 6-inch elastic bandage and continue proximally while wrapping. Once near the axilla, wrap over the acromioclavicular joint and around the posterior thorax.

2. Continue under the opposite axilla, across the chest and bring down over the acromioclavicular joint and onto the upper arm.

Figure 18-21. Shoulder bandaging.

3. Repeat the figure-of-eight pattern as the length of the bandage allows and finish on the upper arm.

1. Lay the base of the bandage over the shoulder with the apex pointed toward the arm. Tie the two free ends just anterior to the axilla.

Figure 18-22. Shoulder bandaging (triangular bandage). (Redrawn from Auerbach PS: Medicine for the Outdoors, 4th ed. Guilford, CT: Lyons Press, 2003, p 264.)

2. Roll the apex up the arm to the desired point of coverage and tie off.

Scalp Bandaging

Ear Bandaging

Wounds to the scalp often require a dressing placed over hair, making adhesion very difficult. The dressing can be secured with a triangular bandage in a method that allows for considerable tension should pressure be necessary to stop bleeding (Fig. 18-23).

A wound to the pinna may require a compression dressing. If so, gauze should be placed both anterior and posterior to the ear to allow it to maintain its natural curvature. A cravat is used to secure the dressing (Fig. 18-24). This method may be used for wounds anywhere along the side of the head or under the chin.

Chapter 18: Bandaging and Taping

1. Drape a triangular bandage just over the eyes and fold the edge 1 inch under to form a hem. Allow the apex to drop over the back of the neck.

2. Cross the free ends over the back of the head and tie in a half-knot.

Figure 18-23. Scalp bandaging. (Redrawn from Auerbach PS: Medicine for the Outdoors, 4th ed. Guilford, CT: Lyons Press, 2003, p 265.)

3. Bring the free ends to the front of the head and tie a complete knot. At the posterior aspect of the head, tuck the apex into the half-knot.

1. Place the cravat over the wound at the cravat’s midpoint. Wrap one end over the head and the other under the chin.

2. Cross the cravat just above ear level and wrap ends in opposite directions.

Figure 18-24. Ear bandaging. (Redrawn from Auerbach PS:Medicine for the Outdoors,4th ed. Guilford, CT: Lyons Press, 2003, p 266.)

3. Tie off the ends.

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Figure 18-25. Bandage for the injured eye. A cravat or cloth is rolled and wrapped to make a doughnut-shaped shield, which is fixed in place over the eye. (Redrawn from Auerbach PS: Medicine for the Outdoors, 4th ed. Guilford, CT: Lyons Press, 2003, p 175.) Figure 18-26. Holding an eye patch in place with a cravat. Hang a cloth strip over the uninjured eye. Hold the patch in place with the cravat. Tie the cloth strip to lift the cravat off the uninjured eye (Redrawn from Auerbach PS:Medicine for the Outdoors,4th ed.Guilford,CT:Lyons Press, 2003, p 262.)

Eye Bandaging When bandaging an eye, a shield is placed over the eye socket to protect the globe, followed by application of a bandage over the shield. The shield may be commercially available sterile pads, cut foam or felt, stacked gauze, or a shirt or cravat fashioned into a doughnut shape (Fig. 18-25). The bandage is fashioned from a cravat and a spare piece of 15-inch cloth or shirt. The spare cloth is placed over the top of the head from posterior to anterior such that the anterior portion lies over the

19

unaffected eye. A cravat is then applied horizontally to hold the shield over the injured eye. To expose the uninjured eye, pull up both ends of the spare cloth and tie at the top of the head (Fig. 18-26). The references for this chapter can be found on the accompanying DVD-ROM.

Emergency Airway Management Swaminatha V. Mahadevan

Emergency airway management encompasses the assessment, establishment, and protection of the airway in combination with effective oxygenation and ventilation. Timely, effective airway management can literally mean the difference between life and death, taking precedence over all other clinical considerations. Airway management in the wilderness must often be provided in austere or unusual environments under less than ideal circumstances. Many of the resources and equipment readily available in a hospital or emergency department setting are not accessible in the wilderness. As with other aspects of wilderness medicine, improvisation may prove invaluable.


AIRWAY ANATOMY A full understanding of airway anatomy is essential for airway evaluation and management. Internally, the airway is made up of

many structures and well-defined spaces, and originates at the nasal and oral cavities (Fig. 19-1). The nasal cavity extends from the nostrils to the posterior nares or choanae. Resistance to airflow through the nose is almost twice that of the mouth, explaining why patients mouth-breathe when they require high flow rates (e.g., with exercise). The nasopharynx extends from the end of the nasal cavity to the level of the soft palate. The tonsillar lymphoid structures are the principal impediments to airflow through the nasopharynx. The oral cavity is bounded by the teeth anteriorly, hard and soft palate above, and tongue below. The oropharynx, which communicates with the oral cavity and nasopharynx, extends from the soft palate to the tip of the epiglottis. The tongue is the principal source of obstruction in the oropharynx. This obstruction results in part from decreased muscle tone of the genioglossus muscle, which contracts to move the tongue forward during inspiration and dilate the pharynx. The oropharynx continues as the laryngopharynx (hypopharynx), which extends from the epiglottis to the upper border of

Chapter 19: Emergency Airway Management

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Nasal cavity Nasopharynx

Figure 19-1. Lateral airway anatomy. (Redrawn from Mahadevan SV, Garmel GM [eds]: An Introduction to Clinical Emergency Medicine: Guide for Practitioners in the Emergency Department. Cambridge, UK, Cambridge University Press, 2005. © Chris Gralapp, www.biolumina.com.)

Oral cavity

Oropharynx Vallecula

Epiglottis

Laryngeal inlet Laryngopharynx Larynx Glottis

the cricoid cartilage (at the level of the C6 vertebral body). The larynx, which lies between the laryngopharynx and trachea, serves as an organ of phonation and a valve to protect the lower airway from aspiration. The larynx is made up of muscles, ligaments, and cartilages, including the thyroid, cricoid, arytenoids, corniculates, and epiglottis. The flexible epiglottis, which originates from the hyoid bone and base of the tongue, covers the glottis during swallowing and provides protection from aspiration. During laryngoscopy, the epiglottis is as an important landmark for airway identification and laryngoscopic positioning. The vallecula is the space at the base of the tongue formed posteriorly by the epiglottis and anteriorly by the anterior pharyngeal wall. The laryngeal inlet is the opening to the larynx bounded by the epiglottis, aryepiglottic folds, and arytenoid cartilages. The glottis is the vocal apparatus including the true and false vocal cords and the glottic opening. The triangular fissure between these vocal cords is the glottic opening, the narrowest segment of the larynx in adults. Externally identifiable landmarks are also important to airway assessment and management (Fig. 19-2). The mentum is the anterior aspect of the mandible, forming the tip of the chin. The hyoid bone forms the base of the floor of the mouth. The thyroid cartilage forms the laryngeal prominence (“Adam’s apple”) and thyroid notch. The cricoid cartilage, lying inferior to the thyroid cartilage, forms a complete ring that provides structural support to the lower airway. The cricothyroid membrane lies between the thyroid and cricoid cartilage and serves as an important site for surgical airway management.

Knowledge of the anatomic differences between adults and children is integral to effective pediatric airway management. These important differences are summarized in Table 19-1 and Figure 19-3.


ASSESSMENT OF THE AIRWAY

AND RECOGNITION OF AIRWAY COMPROMISE

Assessment of the airway begins with evaluation of airway patency and respiratory function. The goal of this assessment is to determine whether the airway is patent and protected, and whether breathing is present and adequate. This is accomplished by inspection, auscultation, and palpation, commonly known as the “look, listen, and feel” approach. Visual signs of airway compromise include agitation, obtundation, and cyanosis. Blue, gray, or ashen skin, especially around the eyes, lips, and nail beds, is a worrisome finding. Significant airway compromise may present without cyanosis, such as an allergic reaction with upper airway edema and vasodilation (causing flushed red skin), or unconsciousness resulting from carbon monoxide poisoning. Bradypnea, tachypnea, or irregular respirations may be a sign of impending respiratory compromise. Breathing that is shallow, deep, or labored may indicate respiratory insufficiency. Respiratory muscle fatigue may result in recruitment of the accessory muscles of respiration, clinically manifested

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Hyoid bone Thyroid membrane Thyroid notch Laryngeal prominence Thyroid cartilage Cricothyroid membrane

Figure 19-2. External airway anatomy. (Redrawn from Mahadevan SV, Garmel GM [eds]: An Introduction to Clinical Emergency Medicine: Guide for Practitioners in the Emergency Department. Cambridge, UK, Cambridge University Press, 2005. © Chris Gralapp, www.biolumina. com.)

Cricoid cartilage Tracheal rings Thyroid gland

TABLE 19-1. Anatomic Airway Differences between Children and Adults ANATOMY Large intraoral tongue occupying relatively large portion of the oral cavity High tracheal opening: C1 in infancy versus C3–4 at age 7, C4–5 in adults Large occiput that may cause flexion of the airway; large tongue that easily collapses against the posterior pharynx Cricoid ring narrowest portion of the trachea as compared with the vocal cords in adults Consistent anatomic variations with age, with fewer abnormal variations related to body habitus, arthritis, chronic disease Large tonsils and adenoids may bleed. More acute angle between epiglottis and laryngeal opening results in nasotracheal intubation attempt failures. Small cricothyroid membrane

CLINICAL SIGNIFICANCE 1. High anterior airway position of the glottic opening compared with that in adults 2. Straight blade preferred over curved to push distensible anatomy out of the way to visualize the larynx Sniffing position is preferred. The large occiput actually elevates the head into the sniffing position in most infants and children. A towel may be required under shoulders to elevate torso relative to head in small infants. 1. Uncuffed tubes provide adequate seal as they fit snugly at the level of the cricoid ring. 2. Correct tube size is essential because variable expansion cuffed tubes are not used. 8 years, small adult Blind nasotracheal intubation not indicated in children Nasotracheal intubation failure

Needle cricothyroidotomy difficult and surgical cricothyroidotomy impossible in infants and small children

From Walls RM, Murphy MF, Luten RC, Schneider RE (eds): Manual of Emergency Airway Management, 2nd ed. Philadelphia: Lippincott Williams & Wilkins, 2004.

as suprasternal, supraclavicular, or intercostal retractions. Traumatic injury to the chest (e.g., flail chest) or an aspirated foreign body may result in paradoxical or discordant chest wall movement. In children, visual signs of airway compromise and respiratory distress include tachypnea, cyanosis, drooling, nasal

flaring, and intercostal retractions. A child with severe upper airway obstruction may sit upright with the head tilted back (“sniffing” position) to straighten the airway and reduce occlusion. A child with severe lower airway obstruction may sit up and lean forward on outstretched arms (“tripod” position) to augment accessory muscle function.

Chapter 19: Emergency Airway Management

Figure 19-3. Anatomic airway differences between children and adults.The anatomic differences particular to children include:1.Higher, more anterior position for the glottic opening. (Note the relationship of the vocal cords to the chin–neck junction.) 2.Relatively larger tongue in the infant, lying between the mouth and the glottic opening. 3. Relatively larger and more floppy epiglottis in the child.4.Cricoid ring is the narrowest portion of the pediatric airway; in adults, the narrowest portion is the vocal cords. 5. Position and size of the cricothyroid membrane in the infant. 6. Sharper, more difficult angle for blind nasotracheal intubation. 7. Larger relative size of the occiput in the infant. (Redrawn from Walls RM, Murphy MF, Luten RC, Schneider RE [eds]: Manual of Emergency Airway Management, 2nd ed. Philadelphia: Lippincott Williams & Wilkins, 2004.)

Tongue

Vocal cords

Epiglottis

Cricoid membrane

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Cricoid ring

Junction of chin and neck Infant

Tongue

Vocal cords

Epiglottis

Cricoid membrane Cricoid ring

Junction of chin and neck

Adult

Under most circumstances, hearing the victim speak with a normal voice suggests that the airway is adequate for the moment. Unusual sounds or noisy respirations may be present with partial airway obstruction. Snoring indicates partial airway obstruction at the pharyngeal level; gurgling may be heard with blood or secretions in the airway; stridor may be associated with partial airway obstruction at the level of the larynx (inspiratory stridor) or the level of the trachea (expiratory stridor); hoarseness suggests a laryngeal process. The central face and mandible should be assessed for structural integrity because injuries to these structures may lead to airway distortion and compromise. The anterior neck should be carefully inspected for penetrating wounds, asymmetry, or swelling that may herald impending airway compromise. Palpation of subcutaneous air suggests direct airway injury. In the unconscious victim, feel for air movement at the mouth and nose. Open the mouth to inspect the upper airway, taking care not to extend or rotate the neck. Identify and remove any vomitus, blood, or other foreign bodies. Look for swelling, bleeding, or other abnormalities of the oropharynx. The gentle use of a tongue blade may facilitate this task. The victim’s ability to spontaneously swallow and handle secretions is an important indicator of intact airway protective mechanisms. In the unconscious victim, absence of a gag reflex has traditionally been linked to loss of protective airway reflexes. Auscultation of the lung fields should demonstrate clear and equal breath sounds. Diminished breath sounds may result from a pneumothorax, hemothorax, or pleural effusion. Wheezing and dyspnea are often associated with lower airway obstruction.


OPENING THE AIRWAY Opening the airway and ensuring airway patency are essential for adequate oxygenation and ventilation. These are the first priorities in airway management. The conscious victim uses the musculature of the upper airway and protective reflexes to maintain a patent airway and protect against aspiration of foreign substances, gastric contents, or secretions. In the severely ill, compromised, or unconscious victim, these protective airway mechanisms may be impaired or absent. Upper airway obstruction in the unconscious victim is most commonly the result of posterior displacement of the tongue and epiglottis at the level of the pharynx and larynx. This occlusion results directly from the loss of tonicity of the submandibular muscles, which provide direct support to the tongue and indirect support to the epiglottis. Upper airway obstruction may be alleviated by head positioning, manual airway techniques, and mechanical airway adjuncts.

Head Positioning If the mechanism of injury or physical examination suggest possible of cervical spine injury, the head should be placed in the neutral position, and efforts to stabilize the neck and head should be initiated. Care should be taken not to flex, extend, or rotate the victim’s head. After cervical spine immobilization, the airway should be reevaluated for obstruction. The optimal head position for airway alignment and patency varies with age. For an infant in the supine position, the large

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PART FOUR: INJURIES AND MEDICAL INTERVENTIONS victim’s head. Then, grasp the angles of the mandible with both hands and lift, displacing the jaw forward while tilting the head back.

Jaw Thrust without Head Tilt A

Infant

Small child

Older child/adult

If a cervical spine injury is suspected or cannot be excluded, the jaw thrust without head tilt (Fig. 19-6) can be performed while maintaining neutral cervical spine alignment. In this maneuver, the jaw thrust is performed without extending or rotating the neck.

Tongue Traction If the patient is unconscious or in extremis, the airway may be opened temporarily by attaching the anterior aspect of the victim’s tongue to the lower lip with two safety pins (Fig. 19-7). An alternative to piercing the lower lip is to pass a string through the safety pins and exert traction on the tongue by securing the end of the string to the victim’s shirt button or jacket zipper (Fig. 19-8).

B Figure 19-4. A, Clinical determination of optimal airway alignment using a line passing through the external auditory canal and anterior to the shoulder (see text for details).B, Application of the line to determine optimal position.In this small child the occiput obviates the need for head support,yet the occiput is not so large as to require support of the shoulders.Note that the line traversing the external auditory canal passes anterior to the shoulders.With only slight extension of the head on the atlanto-occipital joint, the sniffing position is achieved. (Redrawn from Walls RM, Murphy MF, Luten RC, Schneider RE [eds]: Manual of Emergency Airway Management, 2nd ed. Philadelphia: Lippincott Williams & Wilkins, 2004.)

occiput contributes to flexion of the head and neck and resultant airway obstruction. This may be alleviated by elevating the shoulders with a small towel (Fig. 19-4). In children, slightly extending the head into the sniffing position helps relieve airway obstruction. In adults, placing a folded towel or article of clothing under the occiput, which flexes the neck at the torso, followed by gentle hyperextension of the head at the atlanto-occipital joint, provides optimal alignment of the air-way axes.

Manual Airway Techniques Although the following manual airway techniques are effective, they often require continuous involvement by a single provider to maintain airway patency.

Head Tilt with Chin Lift The head tilt with chin lift (Fig. 19-5) is a simple, effective technique for opening the airway. This maneuver is accomplished by placing the palm of one hand on the victim’s forehead and then applying firm backward pressure to tilt the head back. Simultaneously, the fingers of the other hand are then placed under the bony part of the chin and lifted, bringing the chin forward. These fingers support the jaw and maintain the headtilt position. This maneuver extends the neck; therefore, it should not be used if there is concern about a cervical spine injury.

Jaw Thrust with Head Tilt If a cervical spine injury is not suspected, the jaw thrust with head tilt maneuver may be used to gain additional forward displacement of the mandible. Position yourself at the top of the

Mechanical Airway Adjuncts Several airway adjuncts are available to maintain airway patency while freeing up the health care provider to perform other duties.

Oropharyngeal Airway The oropharyngeal airway (OPA) is an S-shaped device designed to hold the tongue off the posterior pharyngeal wall (Fig. 19-9). When properly placed, it prevents the tongue from obstructing the glottis. It also provides an air channel and suction conduit through the mouth. These devices are most effective in unconscious and semiconscious victims who lack a gag reflex or cough. The use of an OPA in a victim with a gag reflex or cough is contraindicated because it may stimulate retching, vomiting, or laryngospasm. The OPA is made of disposable plastic and comes in various sizes to accommodate children and adults. The size is based on the distance (in millimeters) from the flange to the distal tip. The proper OPA size is estimated by placing the OPA’s flange at the corner of the mouth so that the bite block segment is parallel to the victim’s hard palate; the distal tip of the airway should reach the angle of the jaw. Two types of OPAs are commonly employed. The Guedel uses a tubular design, whereas the Berman is distinguished by airway channels on each side. Technique for Insertion: 1. First, open the mouth and clear the pharynx of any secretions, blood, or vomitus. Remove dentures or partial plates if present. 2. In an adult or older child, insert the OPA upside down or at a 90-degree angle to avoid pushing the tongue posteriorly during insertion. Slide it gently along the roof of the mouth. As the oral airway is inserted past the uvula or crest of the tongue, rotate it so that the tip points down the victim’s throat. 3. In a child, grasp the tongue and gently pull it forward or use a tongue blade to displace the tongue inferiorly and anteriorly. Then, insert the OPA with the tip pointing toward the tongue and throat (i.e., the intended position following placement). 4. The flange should rest against the victim’s lips, and the distal portion should rest on the posterior pharyngeal wall. If the OPA is too short, it may displace the tongue

Chapter 19: Emergency Airway Management

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Figure 19-5. Head tilt with chin lift. (Redrawn from Mahadevan SV, Garmel GM [eds]: An Introduction to Clinical Emergency Medicine: Guide for Practitioners in the Emergency Department. Cambridge, UK, Cambridge University Press, 2005. © Chris Gralapp, www.biolumina.com.)

into the hypopharynx and occlude the airway. If the OPA is too long, it may displace the epiglottis and result in an airway obstruction.

Nasopharyngeal Airway The nasopharyngeal airway (NPA) is an uncuffed trumpet-like tube that provides a conduit for airflow between the nares and pharynx (Fig. 19-10). The NPA is inserted through the nose rather than the mouth. It has a flange at the outer end to prevent displacement or slippage beyond the nostril. These devices are better tolerated than OPAs and are commonly used in intoxicated or semiconscious victims. They are also effective when trauma, trismus (“clenched teeth”), or other obstacles (e.g., wiring of the teeth) preclude placement of an oropharyngeal airway. NPAs are contraindicated in victims with basilar skull or facial fractures because inadvertent intracranial placement may occur. The NPA is made of soft, pliable rubber or plastic and comes in various sizes to accommodate children and adults. Sizes (internal diameter) vary from 12 to 36 French. Proper NPA length is determined by measuring the distance from the tip of the nose to the tragus of the ear. Technique for Insertion: 1. Lubricate the nasopharyngeal airway with a watersoluble lubricant to minimize resistance in the nasal cavity.

Do not use petroleum jelly or a non–water-based lubricant. 2. If the NPA has a beveled (angled) edge, place the airway in the nostril with the bevel directed toward the nasal septum. 3. Gently insert the NPA straight back along the floor of the nasal passage (perpendicular to the coronal plane of the face). 4. If you meet resistance, rotate the tube slightly, reattempt insertion through the other nostril, or try a smallerdiameter tube. Do not force the tube because injury to the nasal mucosa can result in bleeding. 5. Following insertion, the flange should rest on the victim’s nostril, and the distal portion of the airway should rest in the posterior pharynx, behind the tongue. Any flexible tube of appropriate diameter and length can be used as an improvisational substitute for the NPA. Examples include a Foley catheter, radiator hose, solar shower hose, siphon tubing, or inflation hose from a kayak flotation bag or sport pouch. An endotracheal tube (ETT) can be shortened and softened in warm water to substitute for a commercial nasal trumpet. The flange can be improvised using a safety pin through the nostril end of the tube (Fig. 19-11). Although OPAs and NPAs help to establish artificial airways, they do not provide definitive airway protection from aspiration.

Figure 19-6. Jaw thrust without head tilt.(Redrawn from Mahadevan SV,Garmel GM [eds]:An Introduction to Clinical Emergency Medicine:Guide for Practitioners in the Emergency Department. Cambridge, UK, Cambridge University Press, 2005. © Chris Gralapp, www.biolumina.com.)

Figure 19-7. Tongue traction.The airway may be opened temporarily by attaching the anterior aspect of the victim’s tongue to the lower lip with two safety pins. Figure 19-8. Tongue traction.An alternative to piercing the lower lip is to pass a string through the safety pins and exert traction on the tongue by securing the end of the string to the victim’s shirt button or jacket zipper.

Chapter 19: Emergency Airway Management

Figure 19-9. Oropharyngeal airway. (Redrawn from Mahadevan SV, Garmel GM [eds]: An Introduction to Clinical Emergency Medicine: Guide for Practitioners in the Emergency Department. Cambridge, UK, Cambridge University Press, 2005. © Chris Gralapp, www.biolumina.com.)

Figure 19-10. Nasopharyngeal airway. (Redrawn from Mahadevan SV,Garmel GM [eds]:An Introduction to Clinical Emergency Medicine: Guide for Practitioners in the Emergency Department. Cambridge, UK, Cambridge University Press, 2005. © Chris Gralapp, www.biolumina. com.)

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Recovery Position In the spontaneously breathing, unconscious victim who is not at risk for cervical spine injury, placement in the recovery position (Fig. 19-12) assists with maintaining a clear airway and reduces the risk for aspiration. In the recovery position, the tongue is less likely to fall back and occlude the airway, and vomitus is more likely to be expelled than inhaled. Even a diminutive rescuer can place a large person in the recovery position if the proper technique is employed.


FOREIGN-BODY AIRWAY OBSTRUCTION

Figure 19-11. Improvised nasal trumpet.

Foreign bodies, most commonly meat, may cause partial or complete airway obstruction. A victim with partial airway obstruction can usually phonate or produce a forceful cough in an attempt to expel the foreign body. When encountering a victim with a partially-obstructed airway, if air exchange is adequate, do not interfere with the person’s attempts to clear the airway. Encourage forceful coughing and closely monitor the victim’s condition. If the obstruction persists or air exchange worsens or becomes inadequate, the victim should be managed as though a complete airway obstruction exists. Worrisome findings that should prompt immediate management include a weak or ineffective cough, increased respiratory difficulty, decreased air movement, and cyanosis.

Figure 19-12. Recovery position.

Chapter 19: Emergency Airway Management

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TABLE 19-2. Relief of Choking ADULTS AND CHILDREN 2000 >40% >140 Decreased Decreased >35 Negligible Confused, lethargic Crystalloid and blood

Chapter 20: Wilderness Trauma, Surgical Emergencies, and Wound Management

1 finger width 45°-60°

Figure 20-1. Intraosseous resuscitation performed by introducing a needle through the periosteum of the tibia inferior to the tibial tuberosity.

Vascular Access Vascular access must be obtained promptly. The standard method of obtaining access is by insertion of two large-bore (16gauge or larger) catheters, preferably into peripheral veins of the upper extremity. Alternatives include using lower extremity veins and obtaining central venous access. If peripheral access cannot be secured, the femoral vein should be the next site attempted. Advantages of femoral vein access include ease of cannulation relative to jugular and subclavian access, and fewer complications.96 Depending on expertise, the internal jugular and subclavian veins may be accessed. Despite a higher incidence of complications compared with peripheral access, central access complication rates in trauma centers have been demonstrated to be less than 5% in most studies.96 If peripheral access is inadequate or unobtainable, it is clear that the next site attempted should be determined by the provider’s level of confidence and expertise. As a last resort, venous cutdown may be considered. Despite fewer complications than central access, cutdowns are experience and equipment dependent and not recommended in the wilderness environment. Children in the wilderness younger than 6 years of age in whom venous access cannot be obtained should undergo intraosseous resuscitation. This is accomplished by introducing a needle through the periosteum of the tibia just inferior to the tibial tuberosity (Fig. 20-1). Needles that are 18- to 20-gauge are preferable, but any needle strong enough to penetrate the periosteum without bending can be used. Of the resuscitative therapies that potentially may be initiated in a well-prepared expedition, volume resuscitation deserves considerable attention. Fluid resuscitation in trauma has been a contentious topic, perhaps overly so, relative to fluid type and amounts used. A number of recent studies focusing on the prehospital administration of fluids in trauma victims not only rehashed the fluid composition debate but called into question the efficacy of prehospital resuscitation.75 Although further

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prospective trials are needed relative to fluid type and prehospital use, an impressive compilation of data has been amassed looking at resuscitative fluids in the trauma victim. Past studies have not only compared colloids with crystalloids91 but explored the use of blood and plasma substitutes, and hypertonic saline. An analysis of the details of such studies is beyond the scope of this chapter, but a summary of fluid recommendations is in order. In small volumes, hypertonic saline has been shown to be an effective resuscitative fluid, and its efficacy in closed head injury is under evaluation. Currently, no improvement in survival has been demonstrated using hypertonic saline compared with crystalloid, and its use has been associated with hypokalemia, pulmonary edema, and dramatic increases in serum sodium and osmolarity.6 The significance of these reported complications in trained hands is questionable, and hypertonic fluids may have a future role in resuscitation. Further study is warranted on the use of hypertonic saline, but its use in the wilderness setting is not recommended at this time. Artificial blood products, such as perfluorocarbons and diaspirin cross-linked hemoglobin, have been shown to be efficient resuscitative fluids in animal studies.20,80,89 However, they are expensive and not yet available for humans. Based on the current literature, it is clear that both colloids (including hetastarches and albumin) and crystalloids are efficient volume expanders.82 Larger volumes of crystalloids than colloids are needed to achieve similar resuscitative end points, usually in a ratio of 3 to 1. However, no benefit in survival using colloids has been demonstrated, and recent studies indicate that their use in critically ill patients may increase mortality.19,72 In addition, no proven detriment, including increased extravascular lung water, impaired wound healing, or decreased tissue oxygen diffusion, has been demonstrated with the use of large volumes of crystalloids. Crystalloids are safe, nonantigenic, easily stored and transported, effective, and inexpensive. Most experts in trauma care agree that crystalloid is preferable to colloid infusion in the prehospital, early resuscitative phase of trauma care. Accordingly, the resuscitative fluid recommended by ATLS protocol is normal saline. Several animal studies and recent human clinical trials in trauma victims have found that treatment with IV fluids before control of hemorrhage resulted in increased mortality rates.9,59 Although these data are compelling, they have been accumulated in victims with penetrating injuries and short prehospital times, and the definition of prehospital resuscitation in these studies comprised widely varying volumes. Prehospital resuscitative protocols remain in evolution. However, application of these data to the wilderness setting at the current time is dangerous for a number of reasons. First, the leading cause of death in wilderness trauma is head injury. Many multiple trauma victims have a head injury, and it may be impossible to discern whether an intracranial lesion is present. Although under continued study, the current approach to management of head injury is aggressive maintenance of cerebral perfusion pressure to control intracranial pressure (ICP). Under-resuscitation in the context of an intracranial injury could be catastrophic. Second, the multisystem-injured victim frequently presents with associated orthopedic injuries. A victim with closed extremity fractures with significant contained hemorrhage benefits from fluid resuscitation. Third, a victim with significant external hemorrhage that can be controlled before evacuation benefits from intravascular repletion.

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In summary, resuscitation with IV fluids should be initiated in the field, particularly in victims with head injury and unquantified multiple trauma. Victims should have vascular access secured and resuscitative fluids given in the form of normal saline as dictated by severity of injuries and hemodynamics.

Secondary Survey The secondary survey is an extension of the primary survey and should not be undertaken until the primary survey is complete and the victim has been stabilized. In addition, resuscitative regimens, if available, should have been initiated. The secondary survey is a head-to-toe assessment of the victim, including history and physical examination. The face, neck, chest, abdomen, pelvis, extremities, and skin should be examined in sequence. A more detailed neurologic examination should be completed, including reassessment of the GCS. The neck should be examined independently of the thoracolumbar spinal cord. Examination of the pelvis should not include the traditional “rocking” to determine stability because in the presence of pelvic fractures, this action may exacerbate existing comminution. The detailed secondary survey should not delay evacuation packaging. As in the nonwilderness setting, it is imperative to repeat the primary survey as the victim’s condition warrants. Specific examinations are discussed in the sections covering regional injuries.

History The victim’s history should be assessed during the secondary survey. Knowledge of the mechanism of injury and any comorbid medical conditions or allergies may enhance understanding the victim’s physiologic state. The ATLS “AMPLE” history is a useful and rapid mnemonic for this purpose: Allergies Medications currently used Past medical history/Pregnancy Last meal Event or Environment related to the injury

Adjuncts Resuscitation should be initiated simultaneously with the primary survey. The degree of resuscitation depends on available resources, experience of the rescuer(s), and environmental conditions. Under the best circumstances, initial management of the wilderness trauma victim provides for airway control, adequate oxygenation and ventilation, appropriate fluid resuscitation, and stabilization of cardiac function while continuing to monitor and reassess the patient’s vital signs. As adjuncts to the secondary survey, it also includes placement of a urinary catheter and nasogastric (NG) tube. This degree of resuscitation will be almost universally unavailable in the wilderness setting. Here, resuscitation may be limited to oral administration of warm, high-calorie fluids and maintenance of victim comfort and body temperature. An NG tube and indwelling urinary (Foley) catheter should be placed if available and appropriate. Aspiration of gastric contents can be catastrophic in terms of patient survival after trauma. Gastric decompression with an NG tube may help prevent this type of adverse event in patients with a depressed level of consciousness. It should be remembered that children can exhibit significant hemodynamic consequences secondary

to massive gastric distention. In this setting, decompression becomes critical. If possible, NG tubes should be placed in persons who are endotracheally intubated in the field. The tube can be aspirated sequentially with a syringe or left open to gravity drainage. Any suspicion of facial fracture should deter attempts to place an NG tube, and orogastric decompression should be chosen instead. A Foley catheter can assist in volume assessment and hemodynamic status determination in a critically injured victim. Hourly urine output typically does not decrease until the onset of class III hemorrhagic shock, with loss of 30% to 40% of blood volume. Contraindications to urinary catheter placement in the field are blood at the urethral meatus, high-riding prostate, scrotal hematoma, and personnel not experienced in placement.

Pneumatic Antishock Garment. The pneumatic antishock garment (PASG) is a noninvasive device inflated around the lower extremities and abdomen to augment peripheral vascular resistance and increase blood pressure. It was widely instituted as a treatment for shock in the 1980s, largely based on anecdotal data. Prospective data relevant to penetrating chest and abdominal trauma44,60 and retrospective data in blunt trauma7 indicate an increase in mortality with its use. Hemodynamically unstable pelvic fractures can be stabilized using a simple sheet wrap. Use of the PASG is not indicated in the wilderness setting.75 A new device for stabilization of a pelvic fracture in a wilderness setting is the SAM Sling (SAM Products, Newport, OR).

Injuries to the Head, Face, and Neck The secondary survey begins with examination of the entire head and scalp for evidence of skull or facial fractures, ocular trauma, lacerations, and contusions. The scalp is thoroughly palpated for tenderness, depressions, and lacerations. The bones of the face, including the zygomatic arch, maxilla, and mandible, are palpated for fractures. Detailed discussion of orofacial and eye injuries is presented in Chapters 25 and 26). Elements of the GCS are repeated. The wilderness eye is discussed in detail in Chapter 25, but general examination principles are simple. Significant periorbital edema may preclude examination of the globe, so assessment should be carried out early. The globe should be evaluated for visual acuity, pupillary size, conjunctival hemorrhage, lens dislocation, and entrapment. Persons with significant facial trauma have a high incidence of associated ocular or orbital injuries.78 Recent studies of ocular injuries in trauma victims have emphasized underappreciation by many disciplines involved in the victim’s care of ocular and periocular signs indicative of significant underlying injury.74

Head Injuries Approximately 500,000 to 2 million cases of head injury occur in the United States yearly.35 Of these, approximately 10% result in the patient’s death before reaching a hospital.5 Longterm disability associated with head injury is significant, with more than 100,000 persons suffering varying degrees of permanent impairment. Because of the high-risk nature of traumatic brain injury (TBI) and the impact of initial management on disability and survival, clinical management objectives must address both immediate survival and long-term outcome. Management guidelines for head injuries in a wilderness do not exist,

Chapter 20: Wilderness Trauma, Surgical Emergencies, and Wound Management

Anatomy The scalp comprises five layers of tissue that cover the calvaria: skin, connective tissue, galea aponeurotica, loose areolar tissue, and periosteum of the skull. The galea is a fibrous tissue layer with important ramifications in closure of scalp wounds, discussed later in this chapter. Loose areolar tissue beneath the galea represents the site of accumulation of blood in scalp hematomas. A rich vascular network located between the dermis and the galea supplies the scalp. When lacerated, these vessels can be a significant source of hemorrhage, which may be important if evacuation is impossible or delayed. The skull is composed of two groups of bones that form the face and cranium. Cranial bones are divided into the calvaria and skull base. The calvaria is composed of frontal, ethmoid, sphenoid, parietal, and occipital bones. Within the skull, the brain is covered by three membranous layers that may be of pathophysiologic importance after injury. However, in the wilderness environment, these layers have little clinical relevance (except in terms of defining an open versus closed brain injury).

Pathophysiology of Traumatic Brain Injury Traumatic brain injury can be divided into primary and secondary brain injury. Primary injury consists of the physical or mechanical insult at the moment of impact, and the immediate and permanent damage to brain tissue. Little can be done in the wilderness setting relative to primary brain injury. Secondary brain injury is the biochemical and cellular response to the initial mechanical trauma and includes physiologic derangements that may exacerbate effects of the primary trauma. Such pathophysiologic alterations include hypoxia, hypotension, and hypothermia. Compounding these pathophysiologic alterations is elevation of ICP after TBI. Increased ICP increases cerebral ischemia and exacerbates secondary brain injury.

Volume-Pressure Curve Herniation

60 55 50 45 ICP (mm Hg)

and a wide range of clinical approaches are used in hospital settings.35 However, the literature suggests that morbidity and mortality can be reduced by means of a protocol that includes early airway control with optimization of ventilation,40 prompt cardiopulmonary resuscitation, and rapid evacuation to a trauma care facility. Initial management of head injury in the wilderness should follow established ATLS protocols. Prompt attention must then be given to victim triage, evacuation strategies, and ongoing resuscitative needs to prevent or minimize secondary brain injury. Expeditious evacuation to a neurosurgery-capable trauma center is essential. Multiple clinical and experimental studies have demonstrated the detrimental effects of hypoxia on the injured brain. A definitive airway should be established if any degree of neurologic or respiratory compromise exists. Cervical spine injuries are common in patients with TBI. Therefore, cervical spine immobilization is paramount in prevention of further devastating neurologic injury. After immobilization, attention is directed to prevention of secondary brain injury. The purpose of the wilderness head injury protocol is to allow individuals with widely varying levels of experience and expertise to identify signs of significant head injury, begin proper resuscitation in the context of prevention of secondary brain injury through airway maintenance and hemodynamic support, and evacuate appropriately.

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40 35 30 25 20 15 10

Point of hemodynamic decompensation

5 Volume of mass

Figure 20-2. Critical time period between decompensation and brainstem herniation after traumatic brain injury.

Many forms of head injury result in elevated ICP, the duration of which is significantly correlated with poor outcome. The Monro-Kellie doctrine states that the volume of intracranial contents must remain constant because the cranium is a rigid container. The normal compensatory response to increased intracranial volume is to decrease venous blood and cerebrospinal fluid (CSF) volume within the brain. If this normal response is overwhelmed, small increases in intracranial volume result in exponential increases in ICP. A rigid bony cranium cannot expand to accommodate increases in brain volume and the resultant increase in ICP. Brain parenchyma becomes compressed and eventually displaced from its anatomic location. In the most devastating circumstances, the brain parenchyma herniates toward the brainstem through the largest cranial opening (the foramen magnum) and death rapidly follows. The volume–pressure curve in Figure 20-2 relates the small, but critical, time period between neurologic symptoms, hemodynamic decompensation, and brainstem herniation. Elevation in ICP directly correlates with secondary brain injury. Therefore, the field provider must attempt to minimize ICP of head-injured patients to the greatest extent possible. The most important priority in minimizing secondary brain injury in the field is optimizing cerebral perfusion pressure (CPP). CPP is related to ICP and mean arterial pressure (MAP) as follows: CPP = MAP − ICP A CPP less than 70 mm Hg after head injury correlates with increased morbidity and mortality.5,39 Cerebral blood flow (CBF) should be maintained at approximately 50 mL/100 g brain tissue per minute.57 At 5 mL/100 g per minute, irreversible damage and potential cell death occur.5 Study data have shown a correlation between low CBF and poor outcome.57 At a MAP between 50 and 160 mm Hg, cerebral autoregulation maintains

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CBF at relatively constant levels. Not only is autoregulation disturbed in injured regions of the brain, but a precipitous fall in MAP can further impair autoregulatory function, decreasing CBF and exacerbating ischemia-induced secondary injury. The field provider is able to combat a rise in ICP by simply optimizing MAP through aggressive IV fluid resuscitation.

Diagnosis The three useful descriptions of head injury that may be applied to field recognition are history, severity, and morphology. History includes mechanism of injury, timing of the event, and related circumstances. This knowledge assists in the decisionmaking process with regard to resuscitation and evacuation.5 Mechanism of injury is identified as blunt or penetrating trauma. The anatomic demarcation between blunt and penetrating injury is traditionally defined by violation of the outer covering of the brain (dura mater). Blunt injuries in the wilderness setting most often result from falls, falling objects, or assaults. Penetrating injuries are most commonly gunshot, or other projectile, wounds. Severity of injury can be estimated by quantifying the GCS and pupillary response. The generally accepted definition of coma is a GCS score of less than or equal to 8; these patients often require endotracheal intubation. Although GCS score does not directly correlate with a need for intubation, it is essential that all head-injured patients be provided a stable, secure airway by the most appropriate means available. It is important to note the TBI victim’s best initial motor response because this is most predictive of long-term neurologic outcome. Any victim with a GCS score less than 15 who has sustained a head injury should be evacuated, if possible. A low or declining GCS score suggests increasing ICP. Abnormal pupil size or asymmetric pupillary responses suggest increased ICP. These clinical deteriorations demand the rapid attention of rescue or evacuation personnel to optimize MAP and CCP, minimize secondary brain injury, and prevent brainstem herniation. Injury morphology may be difficult to assess in the wilderness setting and relies on level of suspicion and clinical signs and symptoms. After attention to the primary survey, including airway provision and spinal immobilization, the physical examination of the secondary survey is imperative and can provide information about the presence of a TBI.

Injury Classification Intracranial injuries range from concussion to massive subdural hematoma. Subdural hematomas are more common than epidural hematomas, comprising 20% to 30% of mass lesions. “Subdurals” result from torn bridging veins between the cerebral cortex and draining venous sinuses. Their prognosis is worse than that of “epidurals,” although prompt recognition and drainage improves patient outcome. Epidermal hematomas

are most commonly located in the temporal region and result from injury to the middle meningeal artery, often associated with a fracture. These patients may present with loss of consciousness followed by a lucid interval and subsequent rapid neurologic deterioration. This sequence, however, is not frequently observed. Hemorrhagic contusion is also quite frequent, constituting 35% of traumatic injuries, and has the propensity to increase ICP significantly. Diffuse axonal injury (DAI) is the term used to describe prolonged post-traumatic coma not resulting from a mass lesion or ischemic insult. Similar to hemorrhagic contusion, DAI may result in elevated ICP.

Physical Examination After the primary survey and initial attempts to resuscitate the victim, a more complete physical examination should be done. However, this examination should not delay patient evacuation. A hallmark of TBI is altered level of consciousness. Determination of the GCS score aids in recognition of TBI and should be regularly reassessed to provide a mechanism for quantifying neurologic deterioration. Physical signs that may denote underlying brain injury include significant scalp lacerations or hematomas, contusions, facial trauma, and signs of skull fracture. Findings specific for basilar skull fracture include ecchymosis behind the ears (Battle’s sign) and periorbital ecchymosis (raccoon eyes). Blood behind the tympanic membrane on otoscopic examination (hemotympanum), frank bleeding from the ears, and CSF rhinorrhea/otorrhea also suggest skull fracture and underlying TBI. The pupillary examination may provide valuable data in assessment of underlying TBI. Herniation of the temporal lobe of the brain may be heralded by mild dilation of the ipsilateral pupil with sluggish response to light. Further dilation of the pupil followed by ptosis (drooping of the upper eyelid below its normal level), or paresis of the medial rectus or other ocular muscle, may indicate third cranial nerve compression by a mass lesion or herniation. Table 20-2 relates pupillary examinations to possible underlying brain lesions. Most dilated pupils (mydriasis) are on the ipsilateral side to the mass lesion. With direct globe injury, traumatic mydriasis may result, making evaluation of TBI more difficult. In addition, 5% to 10% of the population has congenital anisocoria (a normal difference in pupillary size between the eyes). Casual inspection may overlook a prosthetic eye, which is mistaken for a fixed pupil. Neither direct trauma nor congenital anisocoria should be assumed in a headinjured victim exhibiting mental status change in the wilderness. After quantification of GCS score, pupillary examination, and examination of the head and face for signs of external trauma, a concise neurologic examination should be performed. The goal of the field neurologic examination is to identify motor or sensory focal deficits suggestive of intracranial injury. Sensory

TABLE 20-2. Interpretation of Pupillary Findings in Head-Injured Victims PUPIL SIZE Unilaterally dilated Bilaterally dilated Unilaterally dilated or equal Bilaterally constricted Bilaterally constricted

LIGHT RESPONSE Sluggish or fixed Sluggish or fixed Cross-reactive (Marcus-Gunn) Difficult to determine; pontine lesion Preserved

INTERPRETATION Third nerve compression secondary to tentorial herniation Inadequate brain perfusion; bilateral third nerve palsy Optic nerve injury Opiates Injured sympathetic pathway

Chapter 20: Wilderness Trauma, Surgical Emergencies, and Wound Management deficits follow general dermatome patterns shown in Figure 20-3. Unilateral hemiplegia may signify uncal herniation resulting from mass effect in the contralateral cortex because of compression of the corticospinal tract in the midbrain. Ipsilateral pupillary dilation associated with contralateral hemiplegia is a classic and ominous sign of tentorial herniation. Reflex changes in the absence of altered mental status are not indicative of TBI. Detailed evaluation of brainstem function cannot be undertaken in the wilderness setting. Performance of gag and corneal reflex evaluations may provide some information helpful in

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triage and evacuation planning, but their presence would not automatically obviate the need for prompt evacuation.

Resuscitation Resources and circumstances permitting, resuscitation should be initiated as an adjunct to the primary survey. The primary focus for the head-injured victim, similar to any traumatized victim, is the airway. During the primary survey and performance of the ABCDE sequence, IV access should be established. If IV resuscitation is impossible, it is not advisable to adminis-

Figure 20-3. Dermatome pattern, showing the skin area stimulated by spinal cord elements. Sensory deficits follow general dermatome patterns.

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ter fluids orally to the victim with head injury because of the likelihood of vomiting, airway compromise, and aspiration. Individuals sustaining head trauma have a high incidence of concomitant injuries. Up to 32% of persons with severe head injury have a long bone or pelvic fracture, 20% to 25% a chest injury, and 10% an abdominal injury. A victim who does not have a palpable femoral pulse or manifests other signs of hypotension in the context of suspected head injury must not be assumed to have a neurogenic etiology of shock, so other etiologies must be thoroughly and aggressively investigated. Resuscitation is critical in the setting of head injury for multiple reasons. Management of a head injury should be secondary to other life-threatening injuries, which, if not addressed, may preclude survival. As previously discussed, maintenance of MAP (and thus CPP) is critical in preventing secondary brain injury. The type of resuscitative fluid administered to trauma victims continues to be controversial. Previously, recommendations warned of the dangers of overhydration in head injury leading to recommendations restricting fluids. Restriction of fluid has not been shown to reduce ICP or edema formation in laboratory models of TBI. Theories of limiting cortical free water content in TBI by using hypotonic IV solutions have not been borne out in animal studies.90 The need for resuscitation and intravascular volume support has been well established. Possible resuscitative fluids include isotonic crystalloids, hypertonic crystalloids, or colloid solutions. There is convincing evidence that hypotonic fluids are not appropriate in TBI secondary to an increase in whole-brain water content and subsequent elevation in ICP. Recent data from animal studies of TBI suggest that colloid solutions offer no advantage over isotonic crystalloids, such as lactated Ringer’s solution, in terms of augmenting CBF or preventing cerebral edema.101 As previously noted, no clear prospective trial has documented any advantage of colloid over crystalloid administration in the victim with multiple systemic injuries. Evidence is accumulating that hypertonic solutions, particularly hypertonic saline, may be beneficial in TBI.92,97 However, an advantage has not been demonstrated in trauma victims overall, and expertise is necessary for their use. The recommended resuscitative fluid for the head-injured victim in the wilderness setting is isotonic crystalloid, with a target MAP of 85 to 95 mm Hg based on cuff blood pressure determinations or extrapolation from distal pulses evaluation.

Further Management Numerous adjuncts exist in the management of the head-injured victim, few of which are applicable in the wilderness setting. Once the primary and secondary surveys are complete, the airway is secured, resuscitation has been initiated, and spine immobilization has been achieved, the victim should be placed in a 30-degree head-up position. This position assists in control of ICP, and thus CPP, through augmentation of venous outflow. This maneuver should not be attempted if the spine cannot be adequately immobilized. If endotracheal intubation is possible, ventilation should be optimized without hyperventilating the victim. Hyperventilation has been used aggressively in the past to promote hypocarbia-induced cerebral vasoconstriction, theoretically to decrease brain swelling. However, if the Paco2 falls below 25 mm Hg, severe vasoconstriction ensues, effectively reducing CBF, promoting ischemia, and possibly augmenting secondary brain injury. Studies have demonstrated worse outcomes in victims with severe head injury who were hyperventilated.68 The

inability to measure or titrate Paco2 in the wilderness mandates that respiration be controlled to approximate near-normal minute ventilation. All bleeding from the scalp or face should be controlled with direct pressure. Scalp hematomas, regardless of size, should not be decompressed. Open wounds, particularly skull fractures, should be irrigated and covered with the most sterile dressing available. Fragments of displaced cranium overlying exposed brain tissue should not be replaced. If signs of skull fracture are present, immunization against tetanus and broad-spectrum antibiotic prophylaxis are recommended as soon as possible. Although diuretics have been widely used in the intensive care management of intracranial hypertension, no rationale exists for their use in the field. The wilderness trauma victim may have many injuries that are impossible to evaluate fully in the field. In this setting, particularly in the presence of hemorrhagic shock, attempts to induce osmotic diuresis to decrease ICP may be life-threatening. Diuretics such as furosemide or mannitol may exacerbate hypotension, cause metabolic alkalosis, and induce renal complications in the absence of physiologic monitoring.4 Steroids have no role in head injury in the field or intensive care unit. Studies have documented no beneficial impact on ICP or survival. Attempts at brain preservation by slowing metabolic rate and oxygen consumption have no role in the wilderness setting. Barbiturates have been used for elevated ICP refractory to other measures, but may induce hypotension, depress myocardial function, and confound the neurologic examination.4 Compared with minimizing ICP, these interventions offer no significant benefit.39 Approximately 15% of persons with severe head injury experience post-traumatic seizures. Phenytoin, if available, can be safely administered in the field, but only after a witnessed seizure. Prophylactic administration has not been shown to decrease long-term seizure activity.

Skull Fracture Skull fracture in the wilderness mandates evacuation. Therapeutic options in the field are few, with intervention limited to identifying the injury and arranging rapid transport. Skull fractures may be open or closed, linear or stellate, and may occur in the vault or skull base. These fractures are associated with a high incidence of underlying intracranial injury. In an awake and alert victim with a skull fracture, the chance of brain injury is increased 400-fold.5 Skull fractures with depression greater than the thickness of the skull may require elevation. No attempt at elevation should be made in the field. Any exposed brain surface should quickly be covered with the most sterile covering available, preferably moistened with crystalloid solution. Loose bone or brain fragments should not be manipulated. If a broad-spectrum antibiotic is available, it should be administered. After attention to the wound and stabilization of associated injuries, the victim should be rapidly evacuated.

Penetrating Head Injuries The majority of penetrating head injuries in the wilderness are gunshot wounds, although knives and arrows may penetrate the cranium. Such penetrating injuries are usually catastrophic. However, examples of survival exist with small-caliber, lowvelocity injuries and tangential wounds.58 As with closed head injury, management priorities consist of maintenance of airway, prevention of secondary brain injury, and rapid evacuation. If the cranium has been violated, the victim should receive antibi-

Chapter 20: Wilderness Trauma, Surgical Emergencies, and Wound Management otics and tetanus immunization in the same manner as for open skull fracture. In the rare instance that the projectile is embedded in the skull, no attempt at removal should be undertaken. If the length of the projectile makes immobilization or transport cumbersome, excess length may be removed, but only if this can be done easily and without displacement of the intracranial segment.

Evacuation Survival and outcome of head injury in the wilderness correlate directly with rapidity of evacuation. Certain situations dictate immediate evacuation. Any person with evidence of an open or closed skull fracture should be evacuated. The incidence of TBI associated with skull fracture is variable but significant throughout the literature. Recent data predict that 30% to 90% of persons with raccoon eyes or Battle’s sign will show abnormalities on computed tomography (CT) scan.11,18 Similarly, any person who sustains a penetrating injury should be evacuated. Decisions concerning evacuation of victims who have sustained closed head injuries can be simplified by dividing the victims into three groups based on probability of injury. A high-risk group, defined as patients with GCS score of 13 or less, focal neurologic signs, or evidence of decreasing level of consciousness, requires evacuation. The low-risk group includes persons who have suffered a blow to the head but are asymptomatic, did not lose consciousness, and complain only of mild headache or dizziness. Data from recent studies suggest that persons who meet low-risk criteria (including GCS of 15, no loss of consciousness, minimal symptomatology, and unlikely mechanism) have a minimal chance of having significant TBI and may be closely observed.11,18 The group for which the evacuation decision is most difficult is the moderate-risk group. These persons have a history of brief loss of consciousness or change in consciousness at the time of injury, or a history of progressive headache, vomiting, or posttraumatic amnesia. If any of these signs is present in the face of concurrent systemic injury, the victim should be evacuated immediately. Studies associating clinical variables and abnormal results on CT scan have demonstrated the significance of decreased GCS score, symptoms, and loss of consciousness. If these signs are present in isolation and the evacuation can be completed in less than 12 hours, the evacuation should proceed. If the evacuation is impossible or will require longer than 12 hours, the victim should be closely observed for 4 to 6 hours. If the examination improves to normality during the observation period, it is reasonable to continue observation.

Neck Injuries Blunt Neck Injuries Injuries to the neck may be classified as blunt or penetrating. Significant blunt injuries include cervical spine injuries and laryngotracheal injuries. Seventy-five percent of injuries to the trachea are confined to the cervical region.73 Fracture of the larynx and disruption of the trachea usually require surgical intervention unavailable in the wilderness. The sooner laryngeal repair is accomplished, the better the outcome with respect to phonation.21 Victims present with a history of a significant blow to the anterior neck. Physical examination findings include difficulty with phonation, subcutaneous emphysema that may extend as far inferiorly as the abdominal wall, stridor, odynophagia, and, often, acute respiratory distress.

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Treatment is focused on establishing and maintaining an airway until evacuation can occur. Frequently, the airway is in jeopardy. Because of the propensity for injuries of this type to result in significant and progressive edema, endotracheal or nasotracheal intubation is often necessary. If these options are unavailable, airway maintenance techniques as described in the Primary Survey section should be used. In the event of intubation failure or lack of availability with impending hypoxic death, a surgical cricothyrotomy may be necessitated. A recent study of prehospital cricothyrotomy demonstrated that success rates were high regardless of medical specialty as long as previous training had been instituted.54 For further descriptions of airway management, refer to Chapter 19.

Background. Vertebral column injury, with or without neurologic deficits, must be identified in any wilderness multiple trauma victim. Approximately 2.6% of victims of major trauma suffer acute injury of the spinal cord.16 Fifteen percent of victims sustaining an injury above the clavicles and 5% to 10% of persons with a significant head injury have a cervical spine injury. In addition, 55% of spinal injuries occur in the cervical region.58 In the wilderness setting, fractures or dislocations of the cervical spine are a result of falls from significant heights, or of high-velocity ski or vehicular injuries. Twenty-eight percent of persons with cervical spine fractures have fractures elsewhere in the spine.10 Anatomy. The cervical spine consists of seven vertebrae. The anteriorly placed vertebral bodies form the weight-bearing structure of the column. The bodies are separated by intervertebral discs and held in place anteriorly and posteriorly by longitudinal ligaments. The paraspinal muscles, facet joints, and interspinous ligaments contribute as a whole to the stability of the spine. The cervical spine, based on its anatomy, is more susceptible to injury than are the thoracic and lumbar spine. The cervical canal is wide from the foramen magnum to C2, with only 33% of the canal comprised by the spinal cord itself. The clinically relevant tracts in the spinal cord include the corticospinal tract, spinothalamic tract, and posterior columns. Classification and Recognition. Fractures of the cervical spine may result in neurologic deficit, with total loss of function below the level of injury.52 Resultant spinal cord injuries should be classified according to level, severity of neurologic deficit, and spinal cord syndrome. Fractures of the C1-C2 complex generally result from axial loading (a C1 ring fracture, or Jefferson’s fracture) or an acute flexion injury (a C2 posterior element fracture, or hangman’s fracture). Approximately 40% of atlas fractures have an associated fracture of the axis. The atlas fracture, if survived, is rarely associated with cord injury but is unstable and requires strict immobilization. Usually, a complete neurologic injury at this level is unsurvivable owing to paralysis of respiratory muscle function. One third of victims sustaining an upper cervical spine injury die at the scene. The most common mechanism of injury is flexion, and the most common level of injury is C5-C6.10 Fractures and dislocations may result in partial or complete neurologic injury distal to the fracture or in no neurologic injury at all. Partial injuries to the spinal cord result from typical patterns of injury. Because flexion injuries are the most common type of injury to the cervical spine, the anterior cord syndrome (see later) is the most commonly seen serious neurologic picture.

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A careful neurologic examination in the field to grade motor strength and document sensory response to light touch and pinprick yields important information that should be documented and reported to the treating physician at the definitive care facility. The presence or absence of Babinski’s reflex should be noted, as well. When appropriate resources are available, a rectal examination should be performed. Complete lack of tone and failure of the sphincter muscles to contract when pulling on the penis or clitoris (the bulbocavernosus reflex) indicate the presence of spinal cord injury. When individuals with cervical spine fractures or dislocations are transported, the neck must be stabilized to prevent further injury to the spinal cord or nerve roots at the level of the fracture or dislocation. Approximately 28% of persons with cervical spine fractures have fractures elsewhere in the spine10; therefore, the entire spine must be protected during transport. Occasionally, a pure flexion event can result in dislocation of one or both of the posterior facets without fracture or neurologic injury. The victim may complain only of neck pain and limitation of motion. If so, the victim should be transported with the neck rigidly immobilized. With this injury, posterior instability is present (because the interspinous ligament is ruptured), and any further flexion stress could produce a spinal cord injury.

Physical Examination. A thorough neurologic examination should be performed. Initial documentation of deficits and frequent repeat examinations are critical to follow-up care. The classification of injury in the field begins with determination of the level of injury. Knowledge of sensory dermatomes (see Fig. 20-3) and motor myotomes is invaluable. The sensory level is the lowest dermatome with normal sensation and may differ on each side of the body. C1 to C4 are variable in their cutaneous distribution, so assessment should begin at C5. The examiner should not be confused by the occasional innervation of the pectoral skin by C1 to C4, known as the “cervical cape.” Light touch and pinprick should be assessed. Motor function should be assessed by the myotomal distribution listed in Box 20-2. Each muscle should be graded on a six-point scale: 0—Total paralysis 1—Palpable or visible contraction 2—Full range of motion without gravity 3—Full range of motion against gravity 4—Full range of motion with decreased strength 5—Normal strength Each muscle must be tested bilaterally and documented. The reflexes alluded to in the classification section must be tested, as well as anal sphincter tone.

Syndromes. There are three clinically useful spinal cord syndromes: Central cord syndrome is characterized by a disproportionate loss of motor power between the upper and lower extremities, with greater strength retained in the lower extremities. Sensory loss is variable. The mechanism of injury usually involves a forward fall with facial impact and hyperextension of the spine. Anterior cord syndrome is characterized by paraplegia and loss of pain and temperature sensation. It is the most

Box 20-2. Sensory and Motor Deficit Assessment SENSORY

C5: Area over deltoid C6: Thumb C7: Middle finger C8: Little finger T4: Nipple T8: Xiphisternum T10: Umbilicus T12: Symphysis L3: Medial aspect of thigh L4: Medial aspect of leg L5: First toe web space S1: Lateral foot S4 and S5: Perianal skin MOTOR

C5: Deltoid C6: Wrist extensors C7: Elbow extensors C8: Finger flexors, middle finger T1: Small finger abductors L2: Hip flexors L3: Knee extensors L4: Ankle dorsiflexors L5: Great toe extensors S1: Plantar flexors

common presenting syndrome caused by cervical spine injury and carries a poor prognosis. Brown-Séquard syndrome results from hemisection of the cord. It consists of ipsilateral motor loss and position sense with contralateral sensory loss two levels below the level of injury. It is usually secondary to penetrating injury.

Immobilization. After identification of injury, the caregiver faces a critical decision with important ramifications—whether to immobilize.32 Victims who would as a matter of course be immobilized in an urban setting might not be appropriate candidates for immobilization in the wilderness. The decision to immobilize converts an otherwise ambulatory victim who can actively participate in his or her own evacuation to one requiring more involved evacuation procedures. The subsequent evacuation can be dangerous to the victim and rescuers and demands significant expense and resource utilization. Risk criteria for cervical spine injury and the need for immobilization have been defined.42,56 All criteria for the exclusion of immobilization must be satisfied. These include normal mental status without chemical influence; lack of distracting injury; normal neurologic examination; and a reliable neck examination without midline neck pain, deformity, or tenderness. Figure 20-4 presents an evidence-based algorithm for determining need for immobilization. Although the need for immobilization poses hazards for the evacuation process, if criteria are met, immobilization takes precedence over ease of evacuation.62 A difficult balance must be struck in the wilderness between the likelihood of true injury and the danger to the expedition members and rescuers that may ensue when the victim is immobilized.

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Mechanism of injury suggestive of cervical spine injury? Yes/unknown Alert and oriented, no distracting injury, not intoxicated? Yes Tenderness, pain spontaneously or with movement? No Normal neurologic exam? Yes Immobilization unnecessary?

Figure 20-4. Clinical assessment of cervical spine stability. Failure of any criterion suggests need for immobilization.

If a rigid litter is not available, the victim should be maintained on the flattest surface possible. A rigid cervical collar should be placed. All collars allow some degree of movement, particularly rotation. Soft collars offer the least immobilization.30 The Philadelphia collar has been shown to allow 44% of normal rotation and 66% of normal lateral bending.58 To achieve 95% immobilization, a halo and vest are necessary. Any number of materials may be used to improvise an immobilizing device (see Chapter 21). Restriction of flexion, extension, and rotation must be achieved to the greatest degree possible. Optimal immobilization consists of a long spine board or litter, rigid collar, bolsters to the sides of the head, and tape or straps restricting movement (Fig. 20-5).

Treatment. The issue of pharmacotherapy for spinal cord injury is under continuous study. Currently, based on data accumulated by the National Acute Spinal Cord Injury Study Group, documented blunt spinal cord injury should be treated with a bolus of 30 mg/kg of methylprednisolone within 8 hours of injury followed by a continuous infusion of 5.4 mg/kg/hr over the next 23 hours.14 Steroids are not recommended in the field unless a victim clearly manifests a spinal cord injury in the absence of head injury. Because little definitive treatment for cervical spine injury can be accomplished in the field, survival and outcome depend on speed of transport and maintenance of airway. This is particularly true considering the association of cervical spine injury with head injury and major systemic trauma. Transport all victims with proven or suspected cervical spine injury to a definitive care facility.

Penetrating Neck Injuries Similar to penetrating head injury, penetrating neck injury is usually due to gun or knife wounds. Most penetrating injuries do not confer bony instability; however, stability should not be assumed. Neurologic deficits, if present, can progress with further movement of an unstable spine. Projectiles should not be removed if embedded in the neck. Penetrating injuries to the neck may not directly injure the spine, but neurologic sequelae

Figure 20-5. Proper spine immobilization.

III

II I

Figure 20-6. Zones in penetrating neck trauma (see text).

may result from blast effect. The same immobilization criteria should be implemented as when dealing with blunt injuries. Penetrating injuries to the neck are classified according to anatomic zones of injury (Fig. 20-6). Zone I injuries extend from the clavicles to the cricoid cartilage. Zone II injuries occur between the cricoid and the angle of the mandible. Zone III injuries occur superior to the angle of the mandible. Historically, treatment has been based on penetration of the platysma muscle. In the wilderness setting, if the examiner is

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confident that platysmal penetration has not occurred, the victim may be observed and the wound considered a laceration. Much debate has occurred over management of platysmal penetration within respective topographic zones, with treatment arms consisting of surgical exploration versus radiographic evaluation. In the wilderness setting, such considerations remain relevant. A penetrating injury violating the platysma muscle indicates the possibility of significant neurovascular, esophageal, or tracheal injuries, so the victim should be evacuated with close attention to the airway.

Injuries to the Thorax Background The mortality rate from thoracic trauma is approximately 10%. Approximately 25% of all trauma deaths in the United States are attributable to chest injury.5 However, only 15% of persons with penetrating thoracic trauma require thoracotomy. In the wilderness environment, blunt thoracic injuries usually result from falls or direct blows to the chest. Penetrating injuries result from gun, knife, or arrow wounds, or from impalement after a fall. Immediate, life-threatening thoracic injuries include airway obstruction, tension pneumothorax, flail chest, and cardiac tamponade.

Pathophysiology Chest injuries often result in hypoxia, hypercarbia, and acidosis. The tissue hypoxia of thoracic trauma can be multifactorial. Inadequate delivery of oxygen can be from hemorrhagic shock, direct lung injury with ventilation–perfusion mismatch (pulmonary contusion, atelectasis, hematoma), or changes in normal intrathoracic pressure dynamics (tension or open pneumothorax). Hemodynamic instability and inadequate oxygen delivery may also result from cardiac tamponade or contusion.

Physical Examination Thorough physical examination begins with visualization and inspection of the chest. Exposure of the chest should be completed in the primary survey. The airway is assessed for patency and air exchange, and the pattern of breathing is noted. In the immediate postinjury period, most trauma victims are tachypneic, partly from pain and anxiety. Dyspnea, cyanosis, the use of accessory muscles of respiration, and intercostal muscular retraction are abnormal and may give clues to the underlying injury. Chest wall movement during respiration should be symmetrical. Paradoxical chest wall movement is associated with flail chest. The chest wall should be inspected for contusions and abrasions, which may herald underlying bony or visceral injury. Distention of the external veins in a person who has just suffered thoracic trauma and is hypotensive or tachycardic (heart rate greater than 130 beats per minute) suggests impaired venous return to the heart. This finding may be seen in situations of increased intrathoracic or intrapericardial pressure and is associated with tension pneumothorax and pericardial tamponade. In tension pneumothorax, deviation of the trachea is in a direction opposite the lesion. Significant sternal bruising may herald fracture or cardiac contusion. The thorax should be palpated systematically for bony tenderness, starting at the distal clavicles and working medially toward the sternum. The sternum is divided into the manubrium, gladiolus (body), and xiphoid cartilage. The

manubrium is joined to the gladiolus by fibrocartilage, but mobility at this joint is minimal. Each rib should be palpated individually. Ribs 1 to 7 are vertebrosternal; their costal cartilages join the sternum. Ribs 8 through 10 are vertebrochondral, with each costal cartilage commonly joining the cartilage of the rib above. Ribs 11 and 12 are vertebral ribs without attachment to the sternum. Point tenderness over a rib can be associated with contusion or fracture. Displaced fractures can be palpated; occasionally, bone grating can be palpated during respiration. Subcutaneous emphysema may extend up into the neck and down to the level of the inguinal ligaments. In the trauma situation, subcutaneous emphysema is invariably associated with pneumothorax. Vocal fremitus describes palpation of vibrations transmitted through the chest wall. During speech, the victim’s vocal cords emit vibrations in the bronchial air column that are conducted to the chest wall. Diminished vocal fremitus is associated with pneumothorax or hemothorax. To test for vocal fremitus, the examiner applies the palmar arch of the examining hand against the person’s anterior chest wall. The person is asked to repeat “one, two, three” using the same pitch and intensity of voice with each repetition. If the vibrations are not well perceived, the patient is asked to lower the pitch of the voice. The chest should be symmetrical, left to right. Percussion is used to detect changes in the normal density of an organ. Percussion of the chest is performed by placing the examining fingertips on the chest wall and sequentially striking the fingertips with the tip of the index or middle finger of the other hand. In the trauma victim, dullness replacing resonance in the lower lung suggests hemothorax. Hyperresonance or tympani replacing resonance occurs only with a large pneumothorax or tension pneumothorax. If a stethoscope is not available, primitive chest auscultation can be performed using a rolled piece of cardboard or paper. Any cylinder that can transmit sound through a column of air accentuates breath sounds when placed against the chest wall. The absence of sounds normally produced by the tracheobronchial air column indicates blockage in the airways or abnormal filtering of sound by fluid in the pleural cavity. In the trauma victim, this is invariably associated with pneumothorax or hemothorax.

Blunt Chest Trauma Blunt chest trauma in the wilderness is most often associated with either a direct blow or a deceleration injury. The mechanism usually relates to a fall from a height. Compression of the chest wall by moving or falling debris may also contribute to intrathoracic injuries, as may be seen in traumatic asphyxia associated with burial in an avalanche or earthquake.

Rib Fractures. Rib fractures range in severity from an isolated nondisplaced single fracture, which causes only minor discomfort, to a major flail segment, which can be associated with an underlying hemopneumothorax and pulmonary contusion. Rib fractures are characterized by painful respiration, most severe on inspiration. Victims often breathe in a characteristically rapid, shallow pattern. Point tenderness is palpated over the fracture, and displacement can occasionally be detected. Rib fractures are detected with a compression test, in which pressure is exerted on the sternum while the victim lies supine. This will elicit pain over the fracture site.

Chapter 20: Wilderness Trauma, Surgical Emergencies, and Wound Management Most patients with rib fractures can be managed with oral analgesics and rest. Thoracic taping and splinting are contraindicated. Multiple rib fractures are significant because of the potential seriousness of associated injuries and increased pain. However, if extreme and compromising respirations, this pain responds well to an intercostal nerve block. Victims with multiple rib fractures need to be evacuated as conditions permit. After administration of an intercostal block, a person may regain the ability to hike out of the wilderness. The morbidity of rib fractures relates to decreased inspiratory tidal volume secondary to pain and splinting. In the wilderness setting, management must focus on pain control and pulmonary toilet. If oral analgesia is insufficient to control pain, an intercostal block is ideal. Depending on the anesthetic used, varying durations of analgesia can be attained, perhaps allowing transient ambulation for evacuation. Deep breathing should be encouraged 10 times hourly to help prevent atelectasis.

Costochondral Separation. It is difficult to distinguish between a rib fracture and costochondral separation. With the latter, pain is more likely to be predominantly anterior over the costochondral junction. Pain increases with inspiration and worsens with direct palpation. Costochondral separation also responds to intercostal nerve block and oral and IV analgesics. Sternal Fracture. A sternal fracture is usually associated with a direct blow to the anterior chest wall. The injury is characterized by severe, constant chest pain that worsens with direct palpation. Sternal instability is unusual and can be associated with a significant underlying visceral injury, including pulmonary or myocardial contusion. If the sternum is unstable, the victim should immediately be evacuated by litter or helicopter. Pneumothorax. Simple pneumothorax can occur from an injury that allows air to enter through the thoracic wall or, more frequently, from an injury to the lung that permits air to escape into the pleural space. Symptoms include tachypnea, dyspnea, resonant hemithorax, absence of breath sounds, and tactile fremitus. A person with chest pain after a blunt blow to the chest, particularly with accompanying rib fracture, should be suspected of having a pneumothorax. Treatment of pneumothorax involves decompression of the pleural space. In the wilderness environment, tube thoracostomy is rarely possible. Fortunately, although victims with isolated pneumothorax may complain of chest pain or dyspnea, they are not completely disabled. With analgesia to control pain, ambulation facilitates evacuation. It may be easier and more prudent to set a slow pace with frequent rest periods than to perform an unnecessary litter evacuation. If resources and expertise allow placement of a thoracostomy tube, it should be performed only when clinically indicated. Considering possible morbidity in a remote area, prophylactic decompression should never be undertaken. Suspicion of a pneumothorax alone on physical examination does not warrant a catheter or chest tube. When a high index of clinical suspicion is accompanied by incapacitating symptoms, such as shortness of breath, decompression should be considered. The key to saving a victim’s life is understanding that a condition exists that can rapidly progress from a nondisabling condition to a life-threatening condition. Once the diagnosis of pneumothorax is entertained, vigilant observation and a high index of clinical

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suspicion are necessary in the event of progression to a tension pneumothorax. Symptoms should be closely monitored and frequent repeat examinations should be performed.

Tension Pneumothorax. A tension pneumothorax develops when a one-way air leak follows lung rupture or chest wall penetration. Air is forced into the thoracic cavity with no means of escape, and pressure mounts within the hemithorax. With sufficient increases in intrathoracic pressure, the mediastinum is shifted to the contralateral side, which impedes venous return from both the superior and inferior venae cavae. Cardiac output is diminished and the victim soon exhibits signs and symptoms of shock. Victims with tension pneumothorax manifest distended neck veins and tracheal deviation away from the side of the lesion. There is unilateral absence of breath sounds, and the hemithorax is hyperresonant or tympanitic. Respiratory distress, cyanosis, and frank cardiovascular collapse may occur. Tension pneumothorax is life-threatening and frequently associated with additional serious injuries. It mandates rapid chest decompression, followed by evacuation to a medical facility. Decompression is performed by inserting a needle or catheter into the chest and converting the tension into an open pneumothorax. Ideally, a 14-gauge catheter is inserted percutaneously over the second rib in the midclavicular or anterior axillary line (Fig. 20-7). Once the rib is identified with the tip of the needle, the needle is marched over the anterior superior surface of the rib and inserted through the intercostal muscles and pleura into the thoracic cavity. As the pressure within the hemithorax is released, a distinct rush of air is heard. The plastic catheter is advanced over the tip of the needle, the needle withdrawn, and the catheter left in place to ensure continued decompression. The needle should not be reintroduced into the catheter because it may damage or sever the catheter. Because tension pneumothorax is commonly associated with severe injury, the victim should be evacuated to a medical facility as rapidly as possible. A rubber glove or a finger cot can be attached to the external catheter opening to create a unidirectional flutter valve that allows egress of air from the pleural space. If resources are limited and treatment is needed, any number of devices can be used to decompress the chest. A sharp instrument and hollow tube sterilized as well as possible are all that is needed. Rapid cleansing of the skin surface is accomplished with antiseptic, alcohol, or water. A Heimlich valve kit is ideal for decompression and represents a valuable addition to the expedition first aid arsenal. If resources permit placement of a thoracostomy tube, adequate anesthesia and expertise are required. The skin should be sterilized if possible, and local anesthesia should be infiltrated into the skin and periosteum of the rib. Insertion is most effectively accomplished through the fifth intercostal space at the anterior axillary line. A small incision is made and the subcutaneous tissue bluntly separated with a finger or clamp. A blunt instrument, preferably a clamp, is forcefully inserted into the pleural space closely adhering to the superior surface of the rib to avoid the inferiorly located intercostal neurovascular bundle. Once the pleural space is entered, a tube (36 fr or greater in size) is inserted apically and posteriorly. The tube should then be secured with suture or tape and 10 to 20 cm H2O suction or underwater seal applied. A tube open

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Figure 20-7. Needle decompression of tension pneumothorax. This procedure is performed only for tension pneumothorax in patients with hemodynamic instability.

to the atmosphere can accomplish decompression. The end of the tube can be covered with a rubber glove, finger cot, or plastic bag. One-way flow evacuating the chest is the goal. This procedure is not without morbidity and should be used only by trained personnel under optimal conditions. Antibiotics with gram-positive coverage should be initiated if the pleural space is penetrated with an indwelling catheter or tube.

Hemothorax. Hemothorax is usually associated with multiple rib fractures resulting from a direct blow to the chest. The primary cause of a hemothorax is laceration of the lung, intercostal vessel, or internal mammary artery. The victim complains of chest pain, tenderness associated with rib fractures, inspiratory pain, and dyspnea. Vocal fremitus is absent, percussion may be flat or dull, and breath sounds are diminished or absent. A chest tube for hemothorax is rarely required in the wilderness setting, but may be placed if proper equipment is available, the patient is symptomatic, and evacuation will be prolonged. Needle aspiration of a hemothorax is unnecessary in the immediate postinjury period and may precipitate a pneumothorax. Flail Chest. When a series of three or more ribs is fractured in both the anterior and posterior plane, a portion of the chest

wall may be mechanically unstable. As negative intrathoracic pressure develops during inspiration, the unstable segment paradoxically moves inward and inhibits ventilation. A flail segment indicates a severe direct blow to the chest wall with associated multiple rib fractures and decreased tidal volumes, often with associated underlying pulmonary contusion. The contusion can be expected progressively to impair ventilation and oxygenation over the succeeding 48 hours. Victims often tolerate a flail segment for the first 24 to 48 hours, after which they require mechanical ventilation. Any victim with a flail segment should be rapidly evacuated. Because the victim is usually incapable of participating in evacuation, a litter should be prepared or aeromedical evacuation considered. Intercostal nerve block may assist in short-term management of pain and pulmonary toilet. Restrictive (to chest wall expansion during inhalation) external chest wall supports, including taping or extensive stabilization with sandbags, are contraindicated. These measures hinder chest wall movement, decrease vital capacity, and are less effective than intercostal nerve block in pain control. However, focal stabilization or cushioning of the flail segment only to control unnecessary motion and pain may provide minimal relief from the discomfort.

Chapter 20: Wilderness Trauma, Surgical Emergencies, and Wound Management Blunt Cardiac Injuries. Blunt cardiac injuries leading to pericardial tamponade or cardiac contusion are rare. Pericardial tamponade is life-threatening. The pericardial sac is fibrous and expands little. A small amount of intrapericardial blood can severely restrict diastolic function. Blunt injury resulting in tamponade is usually from chamber rupture and rarely survivable, particularly in a remote setting. The diagnosis of tamponade can be difficult, particularly in the wilderness. Beck’s triad, which consists of distended neck veins, hypotension, and muffled heart sounds, is present in less than 33% of cases of tamponade and is particularly difficult to ascertain under nonoptimal conditions. Pulsus paradoxus, an increase in the normal physiologic decrease in blood pressure with inspiration, may be indicative of tamponade. Kussmaul’s sign, or a rise in venous pressure with spontaneous inspiration, is possible to assess outdoors. Once pericardial tamponade is diagnosed, immediate evacuation is required. Treatment consists of median sternotomy in a hospital operating room. The only temporizing measure pending evacuation is pericardiocentesis. This procedure can be lifesaving, particularly if a cardiac injury with a slow leak exists. However, its application in the wilderness setting should occur only if there is a high index of suspicion, coupled with shock and impending death unresponsive to resuscitative efforts. A long (approximately 15 cm [6 in]), 16- to 18-gauge needle with an overlying catheter is introduced through the skin 1 to 2 cm (0.5 to 0.75 in) below and to the left of the xiphoid. The needle is advanced at a 45-degree angle with the tip directed at the tip of the left scapula. When the pericardial sac is entered, aspiration with a syringe follows. The catheter is left in place and secured for possible repeat aspirations as the victim’s condition warrants. Immediate evacuation should follow. Cardiac contusion is a rare condition resulting from a severe blow to the precordium. An overlying sternal contusion or fracture may be present. The diagnosis should be suspected in an isolated high-velocity blow to the precordium with unexplained evidence of increased venous pressure, arrhythmias, and hemodynamic instability. Chest pain is invariably present, usually resulting from musculoskeletal contusion. Morbidity results from ensuing arrhythmias. Diagnosis can be definitively made only at autopsy. Electrocardiographic abnormalities after injury have correlated with subsequent arrhythmias.55 In the wilderness setting, any person who is unstable or symptomatic from an arrhythmia should be evacuated. If evacuation is not possible, it is noteworthy that fatal arrhythmia potential decreases significantly after 24 hours. Traumatic Asphyxia. Traumatic asphyxia is a rare syndrome of craniocervical cyanosis, facial edema, petechiae, subconjunctival hemorrhage, and occasional hypoxemia-related neurologic symptoms that results from severe thoracic crush injury. In the wilderness environment, it is associated with land or mudslides, avalanches, or falling debris. Any significant blunt compressive force to the thorax can result in the syndrome. Children are particularly susceptible because of high compliance of the chest wall.16 Traumatic asphyxia is not a benign condition, as a result of a high incidence of serious associated injuries,71 and the mortality rate in natural disasters is consequently high.33 A number of studies have documented the severity of associated injuries, with the syndrome useful as an indicator of potentially lethal injury.24 As documented in natural disasters, a significant crush injury component may accompany traumatic asphyxia.33 Crush

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Figure 20-8. Typical clinical facial appearance of traumatic asphyxia.

injuries and rhabdomyolysis are discussed later in the Extremity Trauma section of this chapter. The pathophysiology of traumatic asphyxia involves two elements. The crush injury results in acute increases in intrathoracic pressure and thus inferior and superior vena caval pressures. Venous flow is reversed in the veins of the head, which contain no valves. Venous hypertension leads to capillary rupture and the characteristic facial edema and petechiae. Recognition of the physical findings is imperative in diagnosing the syndrome and identifying concomitant injuries (Fig. 20-8). Treatment consists of carefully extracting and, if necessary, immobilizing the victim. Rapid extrication is the single most important factor in improving survival. Establishment and maintenance of an airway is critical because significant facial and laryngeal edema may rapidly develop. Associated injuries should then be addressed in the primary survey. Subsequent care is supportive, consisting of airway control, administration of oxygen, head elevation of 30 degrees, treatment of associated injuries, and possible evacuation. The mortality rate is low in civilian environments but higher in wilderness disaster settings. Mortality is due to pulmonary dysfunction and associated injuries. Morbidity is secondary to neurologic damage; however, the majority of neurologic sequelae clear within 24 to 48 hours. If the victim survives, long-term sequelae are rare.

Penetrating Chest Trauma Penetrating chest trauma above the nipple line is associated with hemopneumothorax and may also be associated with significant visceral injury. A victim with penetrating chest trauma below the nipple line often has intra-abdominal penetration in addition to possible thoracic injury. Such a victim requires immediate rapid evacuation. The open (“sucking”) chest wound produces profound intrathoracic physiologic alterations. Normal chest expansion creates negative intrathoracic pressure, which pulls air into the trachea and allows the lungs to expand. When the diaphragm and chest wall relax, positive pressure creates expiration. If the chest wall sustains an injury approximately two thirds the tracheal diameter, negative intrathoracic pressure for inspiration is lost, the ipsilateral lung collapses, and loss of negative

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Diagnosis. Although much progress has been made in the last decade to evaluate for the presence of blunt intra-abdominal injury, modalities such as CT, ultrasonography, and diagnostic peritoneal lavage are irrelevant in the wilderness setting. The wilderness physician must have a high index of suspicion and perform a superlative history and physical examination.

Figure 20-9. Treatment of a sucking chest wound. Sealing the wound with a gel defibrillator pad works best because this pad adheres to wet or dry skin. Petrolatum gauze or Saran Wrap also works well. Note that one side is not sealed to allow egress of air.

intrathoracic pressure affects the good lung. Consequently, it is important rapidly to reconstruct chest wall integrity. Initially, this is most easily done by placing a hand over the sucking chest wound. Field treatment includes placing petrolatum gauze on top of the wound, covering it with a 4 × 4 gauze pad, and taping it on three sides (Fig. 20-9). The untaped fourth side serves as a relief mechanism to prevent tension pneumothorax. Persons with sucking chest wounds should be rapidly evacuated to sophisticated medical care.

Injuries to the Abdomen Intra-abdominal injuries in the wilderness setting are difficult to recognize. However, if recognized, all intra-abdominal injuries require rapid resuscitation and immediate evacuation. The abdomen represents the most frequent site of life-threatening hemorrhagic shock; however, in the wilderness setting, few diagnostic and treatment options exist.

Blunt Abdominal Trauma Blunt intra-abdominal injury is commonly associated with falls. Abdominal injuries are often associated with fractures or closed head injuries. Often, the decision for evacuation is made on the basis of other injuries; however, the wilderness physician must be attuned to the potential for intra-abdominal hemorrhage as an occult injury.

Anatomy. For descriptive purposes, the abdomen may be divided into thoracic, true, and retroperitoneal compartments. The thoracic abdomen contains the liver, spleen, stomach, and diaphragm. The liver, spleen, and, more rarely, stomach may be injured by direct blows to the ribs or sternum. Twenty percent of persons with multiple left lower rib fractures have a ruptured spleen. A direct blow to the epigastrium may result in increased intra-abdominal pressure with subsequent rupture of the liver or diaphragm. The true abdomen contains the small bowel, large bowel, and bladder. Isolated bowel injuries are rare in the wilderness setting. Blunt bladder or rectal injury usually occurs in conjunction with severe pelvic fracture and carries high mortality. The retroperitoneal abdomen contains the kidneys, ureters, pancreas, and great vessels. It is notoriously difficult to

Physical Examination. The physician should look for signs of early shock: tachycardia, tachypnea, delayed capillary refill, weak or thready pulse, and cool or clammy skin. Physical examination of the abdomen begins with visualization and inspection. Contusions and abrasions may be the only harbingers of occult visceral injury. Periumbilical ecchymosis associated with abdominal hemorrhage (Cullen’s sign) is virtually never present in a victim with acute abdominal trauma. Abdominal distention secondary to hemorrhage is a very late sign and never present before shock and cardiovascular collapse. Abdominal inspection should survey the flanks, lower chest, and back. Inspection of the back should follow palpation of the spine while the victim is supine. The victim should be very carefully logrolled if there is any suspicion of spinal injury. Looking for muscle guarding, the examiner gently palpates the abdomen in all four quadrants. Any persistent guarding or tenderness after wilderness trauma mandates rapid evacuation. Percussion tenderness is an indicator of peritoneal irritation, also mandating evacuation. The presence or absence of bowel sounds has little prognostic significance. Bowel sounds may be present in the face of significant intra-abdominal hemorrhage or, conversely, absent in victims when extra-abdominal injuries induce ileus. Referred pain to the left shoulder (Kerr’s sign) strongly suggests the presence of a ruptured spleen. This pain is often exaggerated by placing the victim in Trendelenburg’s position, increasing the amount of left upper quadrant blood irritating the diaphragm. Pain from the retroperitoneal abdomen associated with injuries to the kidney or pancreas may be referred to the back. However, referred pain is usually a late finding and not helpful in the evaluation of acute trauma. Gross hematuria that does not clear immediately or is coupled with an associated injury, such as pelvic fracture or abdominal or back pain, requires immediate evacuation. To minimize blood loss, the victim should be kept stationary and the evacuation team brought as close to the victim as possible. In a wilderness setting, rectal and vaginal examination adds little to the evacuation decision when evaluating for abdominal trauma. The unstable pelvic fracture associated with rectal and vaginal injuries is usually the determinant for evacuation.

Penetrating Abdominal Trauma Penetrating intra-abdominal injuries may result from gunshot, stab, or arrow wounds. The social context in which these injuries occur (accidental, intentional, or self-inflicted) makes little difference in the wilderness setting. Recrimination, guilt, and blame only interfere with the paramount goal of immediate evacuation.

Gunshot Wounds. Low-caliber gunshot injuries often present with small entrance and no exit wounds. High-caliber, high-

Chapter 20: Wilderness Trauma, Surgical Emergencies, and Wound Management velocity gunshot injuries may have relatively innocuous entrance wounds but may be associated with large, disfiguring exit wounds and extensive internal injuries. No matter what the caliber or trajectory and no matter where the entrance and exit, all gunshot wounds from the nipple line to the inguinal ligament should be presumed to have penetrated the abdominal cavity and created an intra-abdominal injury. These injuries mandate immediate surgical intervention. A victim of gunshot wounds to the head, neck, chest, abdomen, or groin should undergo immediate evacuation accompanied by the administration of a single-agent broad-spectrum antibiotic, such as an oral fluoroquinolone (e.g., ciprofloxacin, 750 mg PO bid). Hunting injuries are discussed in Chapter 22.

Shotgun Injuries. Shotgun injuries to the torso are managed in the same manner as gunshot wounds. Shotgun injuries have a potentially lower incidence of underlying visceral injury than gunshot wounds, but there is often extensive soft tissue damage requiring surgical debridement. The potential exists for delayed development of peritonitis from a single penetrating pellet to the viscera. Consequently, shotgun injuries should also be treated with emergency evacuation and a broad-spectrum antibiotic, as recommended previously for gunshot wounds. Occasionally, a close-range shotgun blast results in a soft tissue defect large enough for the injured bowel to extrude through the wound. The injured bowel should not be placed back into the abdomen. Injured bowel displaced from the abdominal cavity conceptually should be treated as though it were an enterocutaneous fistula. Because evacuation is often delayed in the wilderness, it is better to have fecal contents outside, rather than inside, the peritoneal cavity. The exteriorized bowel should be kept moist and covered at all times. Uncovered bowel outside the peritoneal cavity rapidly desiccates and becomes nonviable, mandating later surgical resection. Exposed bowel should be covered with an abdominal pack or cloth moistened with sterile saline at best, or at worst with potable water. The dressing should be checked and remoistened at least every 2 hours. Stab Wounds. The penetrating object is usually a knife but may be as varied as a piton, ski pole, or tree limb. Any deep skin laceration from the nipple line to the groin should be considered to have damaged an intra-abdominal organ. Whereas the odds of an abdominal gunshot wound injuring a visceral organ exceed 85%, the odds of a stab wound injuring a visceral organ are less than 50%. In certain urban hospitals, the high incidence of negative surgical explorations for stab wounds had led to a more selective approach toward patients with abdominal stab wounds.69 This approach uses local wound exploration and frequent physical examination. Although there are no data addressing the management of stab wounds in the wilderness environment, the following approach is practical and reasonable. If the wound extends into the subcutaneous tissue, the evacuation decision depends on local wound exploration. This procedure is simple to perform, even in the wilderness environment. The skin and subcutaneous tissue are infiltrated with local anesthetic, and the laceration is extended several centimeters to clearly visualize the underlying anterior fascia. It is helpful to use lidocaine (Xylocaine) 1% with epinephrine to minimize slight but annoying bleeding that

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can impair visualization. The wound should never be probed with any instruments, particularly if overlying the ribs. Wound exploration is confined to the area from the costal margin to the inguinal ligament. Local wound exploration is contraindicated in wounds that extend above the costal margin, because it is possible for such exploration to communicate with a small pneumothorax, potentially exacerbating respiratory distress. If thorough exploration of the wound shows no evidence of anterior fascial penetration, and if the victim demonstrates no evidence of peritoneal irritation, the wound can be closed with tape (Steri-Strips) or adhesive bandages, dressed, and the evacuation process delayed. Physical examination should be performed every few hours for the next 24 hours. If no peritoneal signs develop and the victim feels constitutionally strong, a remote expedition may resume with caution and an eye to evacuation should the victim become ill. In the wilderness environment, it is prudent to have a low threshold for evacuation because of technical difficulties in performing wound exploration, such as insufficient light and inadequate instruments. Persons who have been impaled by long objects, such as tree limbs or ski poles, should have the object left in place and carefully shortened, if possible, to facilitate transport.

Pelvic Trauma In the wilderness setting, fractures of the pelvis are generally associated with falls from significant heights, high-velocity ski accidents, or vehicular trauma. Pelvic fractures can be lethal. With opening of the pelvic ring, there may be hemorrhage from the posterior pelvic venous complex and occasionally from branches of the internal iliac artery. For hemodynamically unstable victims with severe pelvic fracture, resuscitative efforts should be instituted. In addition, simple techniques to reduce any increased pelvic volume through the application of sheets or slings may slow bleeding. The key factor in initial management of pelvic fractures is identification of posterior injury to the pelvic ring. Posterior ring fractures or dislocations are associated with a greater incidence of significant hemorrhage, neurologic injury, and mortality than are other pelvic fractures. The diagnosis of a posterior ring fracture is based on instability of the pelvis associated with posterior pain, swelling, ecchymosis, and motion. Persons with posterior ring fractures must be immediately evacuated on backboards, with care taken to minimize leg and torso motion. The flank, scrotum, and perianal area should be inspected for blood at the urethral meatus, swelling or bruising, or a laceration in the perineum, vagina, rectum, or buttocks suggestive of an open pelvic fracture. The pelvis should be examined carefully once, without any aggressive rocking motion. The first indication of mechanical disruption is leg length discrepancy or rotational deformity in the absence of an obvious leg fracture or hip location. For more information on pelvic fracture, see Chapter 24.

Extremity Trauma The majority of wilderness-related extremity injuries involve fractures and sprains, which are discussed in Chapter 24. This section focuses on the general field management of significant extremity vascular injury, traumatic amputation, and recognition and treatment of rhabdomyolysis.

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PART FOUR: INJURIES AND MEDICAL INTERVENTIONS

Vascular Injuries Injury to the major vessels supplying the limbs can occur with penetrating or blunt trauma. Fractures can produce injury to the vessels by direct laceration (rarely) or by stretching, which produces intimal flaps. Penetrating injuries can be devastating if transection of a vessel occurs. Significant vascular injuries, from both penetrating and blunt causes, can result in multiple vessel injury subtypes, each of which may be limb-threatening. Injury subtypes include laceration, transection, contusion with spasm, thrombosis, or aneurysm formation (true and false), external compression, and arteriovenous fistula. An accurate history, expeditious physical examination, and swift evacuation are the keys to life and limb salvage.

History. A complete history of the time and mechanism of injury is invaluable in planning further management. Although no absolute ischemia time has been established, a goal of less than 6 hours to reperfusion is prudent.30 The amount of blood present at the scene should be quantified. A history of bright pulsatile blood that abates is suggestive of arterial injury. Thirty-three percent of victims with arterial injuries have intact distal pulses. Physical Examination. Vascular examination in the field can be highly variable. Hypovolemia, hypothermia, and hostile conditions make an accurate examination challenging. Skin color and extremity warmth should be assessed first. Distal pallor and asymmetric hypothermia are suggestive of a vascular injury. Pulses should be palpated. In the upper extremity, the axillary, brachial, radial, and ulnar arteries should be assessed. In the lower extremity, the femoral, popliteal, posterior tibial, and dorsalis pedis pulses should be assessed. Location and direction of the wound should be determined, hemorrhage quantified, and the presence of hematomas or a palpable thrill noted. A good neurologic examination that quantifies motor and sensory deficits is critical. Because of the high metabolic demands of peripheral nerves, disruption of oxygen delivery makes neuronal cells highly susceptible to ischemic death. Conversely, skeletal muscle is relatively resistant to ischemia. Loss of sensation or limb paralysis is an alarming sign of impending anoxic necrosis. Treatment of Vascular Injuries. Significant hemorrhage should be identified and controlled in the primary survey. All hemorrhage should be controlled with direct pressure at the site of injury. Tourniquets should be applied only when direct pressure fails to control bleeding. Tourniquets should be released every 5 to 10 minutes to prevent further ischemia. Hematomas should never be explored or manually expressed. Attempts to clamp or ligate vessels are not recommended. Frequent repeat neurovascular examinations are mandatory. Once bleeding is controlled and the wound is covered with a sterile but noncompressive dressing, completion of the primary survey, identification and stabilization of associated injuries, and appropriate resuscitation with normal saline should follow. The extremity should be splinted to prevent further movement. The need for evacuation depends directly on the results of the physical examination. Examination results can be grouped into “hard signs,” indicative of ischemia or continued hemorrhage, and “soft signs” that are suggestive but not indicative of ischemia (Boxes 20-3 and 20-4).

Box 20-3. Vascular “Hard Signs” Pulsatile bleeding Palpable thrill Audible bruit Expanding hematoma Six “P’s” of regional ischemia Pain Pulselessness Pallor Paralysis Paresthesia Poikilothermia

Box 20-4. Vascular “Soft Signs” Injury in proximity to major vessel Diminished but palpable pulses Isolated peripheral nerve deficit History of minimal hemorrhage All victims with hard signs should be evacuated emergently. Based on current data, an isolated soft sign may warrant observation alone, depending on the remoteness of the expedition and the risks of evacuation. The data for observation of soft signs have emerged from hospital settings and must be applied with great caution in the wilderness. If soft signs are present, clinical suspicion is high, and evacuation can be accomplished safely, the victim should be transported and observed in a medical facility.

Traumatic Amputation In the wilderness environment, amputation victims require immediate evacuation. Hemorrhage is controlled during the primary survey with direct pressure, and resuscitation is instituted. Tourniquets are rarely required. The victim should be kept warm and calm. Reassurance and analgesics should be administered. Amputations should be completed only if minimal tissue bridges exist and it is clear that the neurovascular supply has been interrupted. Amputation of a mangled extremity, defined as an extremity with high-grade open fracture and soft tissue injury, should not be carried out in the wilderness except to free a trapped victim in order to avoid further severe injury or even death, or in the case of uncontrollable hemorrhage threatening the life of the victim, and then only by experienced surgical personnel. All other severely injured extremities should be wrapped in available sterile materials, splinted, and kept moist. Amputated extremities should be cooled if possible, optimally in a plastic bag in ice or ice water. Avoid placing the extremity in direct contact with ice. Without cooling, the amputated extremity remains viable for only 4 to 6 hours; with cooling, viability may extend to 18 hours. The amputated extremity should accompany the victim throughout the course of the evacuation.

Crush Injuries and Rhabdomyolysis Rhabdomyolysis is a potentially fatal syndrome that results from lysis of skeletal muscle cells. In its fulminant form, rhabdomyolysis can affect multiple organ systems. Compartment

Chapter 20: Wilderness Trauma, Surgical Emergencies, and Wound Management syndrome, renal failure, and cardiac arrest represent the major complications. Any condition resulting in significant acute or subacute striated muscle damage can precipitate rhabdomyolysis. Crush injuries of the extremities and pelvis, revascularization of ischemic tissue, ischemic extremities, animal bite and snakebite,17,23 frostbite, and traumatic asphyxia33 can all result in rhabdomyolysis in a wilderness setting. Crush injuries are frequently a result of avalanches, falls from heights, or rock slides. The pathophysiology of rhabdomyolysis remains controversial. The exact mechanism of muscle injury appears not to be simple direct force or isolated ischemia and is probably multifactorial.33 The common cellular derangement is interference of the normal function of muscle cell membrane sodium-potassium adenosine triphosphatase (ATPase) with intracellular calcium influx and cell death.77 After cell death, multiple intracellular constituents, including myoglobin, creatine kinase, potassium, calcium, and phosphate, are released into the systemic circulation. The metabolic derangements of rhabdomyolysis depend directly on release of intracellular muscle constituents. Myoglobinemia, hypercalcemia, hyperphosphatemia, hyperkalemia, hyperuricemia, metabolic acidosis, coagulation defects, and contracted intravascular volume result. The clinical presentation of rhabdomyolysis may include muscle weakness, malaise, fever, tachycardia, abdominal pain, nausea and vomiting, or encephalopathy. Symptoms may mimic those of persons with spinal cord injury.8 The danger of the syndrome lies in the cardiovascular effects of electrolyte disturbances and renal failure70 secondary to changes in renal perfusion and direct toxicity of myoglobin to tubular cells. Successful treatment relies on prompt diagnosis based on clinical signs and urinalysis, aggressive hydration, and forced diuresis. Myoglobin turns urine tea-colored, which is an important indicator of significant muscle death and need for aggressive treatment. Normal saline should be administered IV at 1 to 2 L/hr to achieve a urine output of 100 to 300 mL/hr. Victims who are trapped in rubble should have resuscitation initiated before extrication, if possible. The addition of agents to alkalinize the urine and promote diuresis has been shown to improve clearance of myoglobin but not to alter survival. In addition, diuretics may be detrimental in multisystem trauma victims who are hypovolemic. All victims demonstrating myoglobinuria should be evacuated.

Injuries to the Skin and Wilderness Wound Management The goals of wilderness wound management are to minimize wound complications and promote healing. Treatment should begin with an approach to the victim as a trauma patient. Within the context of the primary survey, hemorrhage should be controlled. Then, the victim should be examined and the wound inspected. Steps to minimize infection should be undertaken, incorporating anesthesia, assessment of need for tetanus immunization and antibiotics, irrigation, and debridement. After attempts to minimize infection, a definitive plan should be established, including the need for evacuation (Box 20-5).

Wound Morphology Major lacerations are often the most obvious sign of trauma; however, injuries to the integument are rarely life-threatening.

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Box 20-5. Guidelines for Wilderness Wound Management 1. 2. 3. 4.

Identify and stabilize associated traumatic injuries Control hemorrhage Examine wound Minimize infection a. Tetanus immunization as indicated b. Antibiotics for high-risk wounds c. Irrigation d. Debridement 5. Implement definitive care

Contusions, abrasions, and lacerations should force the examiner to focus on areas of potential occult injury. Contusions often overlie extremity fractures or, when present on the torso, suggest the potential for underlying visceral injury. Extremity lacerations may be associated with fractures or may extend into the joint space. The four basic types of skin injuries are lacerations, crush injuries, stretch injuries, and puncture wounds. Lacerations rarely require closure in the wilderness environment. Commonly, multiple wound morphologies are present in the same injury, and an array of wound presentations is possible. Crush injuries may be associated with significant tissue necrosis, impaired healing, increased rates of infection, and underlying muscle damage with subsequent rhabdomyolysis. Fortunately, they are rare in the wilderness. Stretch injuries produce a split in the skin but, more important, may be associated with underlying nerve or tendon damage. Puncture wounds often appear innocuous but have a high propensity for infection. Animal bite wounds, discussed in detail in Chapters 51 and 52, can manifest any of these wound morphologies alone or in combination.

Primary Survey Many skin and soft tissue wounds encountered in the wilderness setting accompany significant injuries. Therefore, the wound must never distract the physician from associated lifethreatening injuries. The ATLS primary survey should be performed in the usual fashion.

Control of Hemorrhage The vast majority of bleeding is controlled with direct pressure, applying the most sterile covering available. Applying pressure over major arterial pressure points is discouraged, as is the use of tourniquets. In the event of bleeding not controlled by direct pressure, tourniquets may be applied with the knowledge that limb sacrifice is possible. If applied, tourniquets should be released every 5 to 10 minutes if possible to restore perfusion transiently and to assess if they are still necessary. Clamping bleeding vessels is not advised because this may cause unnecessary neurovascular injury.

Physical Examination Wound inspection and physical examination are critical in any setting. This phase of treatment may need to be abbreviated and should not delay packaging and evacuation. Although it is important to assess the extent of injury, including tissue loss and

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underlying musculoskeletal and neurovascular injury, aggressive wound exploration may worsen existing injuries. Detailed knowledge of regional anatomy is useful. The detailed neurovascular examination should be documented before anesthesia and definitive care, including assessment of pulses and regional perfusion. The neurologic examination should quantify sensory and motor function, with particular attention to functional assessment of muscle groups traversing the injured region. Two-point discrimination should be assessed in wounds involving the hands or fingers. Wounds over joints and tendons should be put through full range of motion.

Anesthesia Pain management in the wilderness is discussed in Chapter 17. Administration of anesthesia occurs before mechanical wound cleansing and definitive care. The three methods of anesthetic administration briefly discussed here are topical, local, and regional. Topical anesthesia was originally introduced for mucosal lacerations but has been shown to be effective for skin wounds. TAC (sterile tetracaine 0.5%, adrenalin [epinephrine] 1 : 2000, and cocaine 11.8% in saline) has been used with success as a topical anesthetic. Complications have included seizures and death.93 An alternative preparation consisting of lidocaine, adrenalin, and tetracaine (LAT) has been shown to be as effective as TAC without the associated complications.29 Topical anesthetics may be soaked into a sterile gauze and placed on the wound surface for 7 to 10 minutes. Disadvantages of topical anesthetics include potential for a slightly increased risk of infection and less versatility than locally injected lidocaine. Local anesthesia is the standard method for achieving soft tissue analgesia. Typically, 1% lidocaine without epinephrine is used. In adults, the maximum injectable dose of lidocaine is 4 mg/kg. Lidocaine should not be injected directly from within the wound to the periphery because this increases the chance of introducing bacteria deeper into the soft tissue.64 The injection should proceed from the periphery of the wound, with each successive needle stick entering the skin through a previously anesthetized area. Local anesthesia can be administered with relatively little discomfort using a 25-gauge needle and a 1-mL tuberculin syringe. Although using a small syringe increases the time to anesthetize a larger wound, this method minimizes both the anesthetic dose and distortion of soft tissue planes, facilitating tissue repair. Pain associated with administration of local anesthesia is due to the acidity and stretching of nerve endings within the dermis and subcutaneous tissue. Burning sensation associated with lidocaine injection is directly proportional to the rate of administration. Warming the local anesthetic,46 buffering the solution with sodium bicarbonate to a concentration of 1%, and administering anesthetic slowly in small doses all minimize pain. Regional anesthesia, defined as sensory nerve blockade proximal to the wound, is an excellent mode of anesthetizing wounds of the upper and lower extremities. Two types are regional nerve block and Bier block. Regional nerve blocks require skill and a detailed knowledge of regional anatomy. They are not suitable for the first-time user in the wilderness environment. The Bier block is reasonable to administer and is possible in the wilderness setting. It involves injection of local anesthetic

into a cannulated hand or foot vein, with concurrent control of venous outflow using a tourniquet.

Irrigation Once the wound is anesthetized, irrigation, debridement, and closure can proceed. Irrigation removes dirt, debris, foreign bodies, and bacteria from the wound. Irrigation has been extensively studied in traumatic wounds and clearly results in a decreased incidence of infection, reducing infection rates as much as 20-fold when proper technique is used. The type of irrigation fluid and the technique used are resource dependent in the wilderness setting. The cleanest fluid available should be used. Wilderness fresh water sources that are not grossly contaminated can be boiled or filtered.32 Any concentration of sterile crystalloid solution can be used, although normal saline remains the most readily available, economical, and cost-effective irrigation solution. Recent data suggest that tap water may be as effective as normal saline.66 The amount of irrigation necessary is difficult to quantify. Some authors use 60 mL (2 ounces) of irrigation solution per centimeter wound length as a guide,46 but in the wilderness setting where precision is more difficult to attain, irrigation should be continued in amounts and time intervals sufficient to remove visible debris from the wound. Many bactericidal and bacteriostatic irrigation solutions, including commercial soaps, ethyl alcohol, iodine solutions, and hydrogen peroxide, are available in wilderness first-aid kits. Many of these agents have been shown to result in significant microcellular destruction of tissues15 and, when used in high concentrations, may impair wound healing. They offer no advantage over copious irrigation with sterile water or crystalloid. Although addition of antibiotics to irrigation solutions is an attractive concept, they are costly, difficult to store, and offer no advantage over irrigation with sterile water alone. The method of wound irrigation, as well as the pressures used, have been studied extensively. The goals of irrigation are to remove bacteria, assist in the mechanical debridement of necrotic tissue, and remove foreign bodies that can impair subsequent wound healing. Optimal irrigation pressures are 5 to 8 psi, delivered through a syringe with a 16- to 20-gauge needle. A splash shield attached to the syringe should be used if available. In summary, irrigation consisting of normal saline or sterilized potable water should be delivered in a continuous fashion by the most sterile implement available at a pressure sufficient to dislodge debris but not overtly damage tissue.

Debridement Like irrigation, debridement has been shown to decrease the incidence of wound infection. In addition, debridement has the potential to improve long-term cosmesis. Debridement should be carried out sharply. Scrubbing the wound with abrasive materials does not improve infection rates and may cause damage to healthy tissue. Similarly, soaking the wound has never been shown to improve outcome. Hair removal should be undertaken only if it impairs visualization and inspection of the wound,93 or if tape is to be used as a method of temporary closure. The goal of debridement in the wilderness should be to remove grossly contaminated or devitalized tissue and to remove foreign bodies and bacteria embedded in such tissue.

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TABLE 20-3. Tetanus Prophylaxis CLEAN MINOR WOUNDS HISTORY OF IMMUNIZATION (DOSES) Unknown None to one Two Three or more Last booster within 5 years Last booster within 10 years Last booster more than 10 years ago

DIRTY MAJOR WOUNDS

TOXOID*

TIG†

TOXOID

TIG

Yes Yes Yes

No No No

Yes Yes Yes

Yes Yes No (unless wound older than 25 hr)

No No Yes

No No No

No Yes Yes

No Yes Yes

*Toxoid: Adult: 0.5 mL dT intramuscularly (IM). Child less than 5 years old: 0.5 mL DPT IM. Child older than 5 years: 0.5 mL DT IM. † Tetanus immune globulin (TIG): 250–500 units IM in limb contralateral to toxoid.

The extent of tissue removal should be based on the experience and training of the caregiver.

Tetanus Prophylaxis Spores of Clostridium tetani are ubiquitous in the environment in such places as soil, animal teeth, and saliva. Any animal bite that penetrates the skin can be responsible for a tetanus infection. The majority of cases of tetanus infection in the United States follow failure to attain adequate immunization.79 This fact accentuates the preventable nature of tetanus infections and essential role of proper immunization. If available in the wilderness setting, tetanus prophylaxis should be administered as outlined in Table 20-3.

Definitive Care of Lacerations “Definitive” care may have many definitions, depending on the setting. The planned approach to management of wounds in the wilderness is determined by a combination of morphology of the wound, infection risk factors, available resources, level of expertise, and type of expedition. Major lacerations or those associated with significant injury should be evacuated. If wound management cannot acceptably minimize infection risk factors, the victim should be evacuated. In general, wounds that can be closed or managed open and that do not impose excessive infection risk factors and do not immobilize the expedition member or group can be treated definitively in the wilderness. The wound must not impair physical ability in a way that the victim risks further injury or jeopardizes group safety.

Wound Closure. Lacerations can be closed if they are small to intermediate in size; have minimal infection risk factors; are on well-vascularized regions, such as the scalp and face; are less than 6 hours old; and have no anatomic contraindications. Closure may be accomplished with suture, staples, tape and similar bandages, or adhesives. Tape and, less frequently, adhesives are viable alternatives to sutures. Healing and cosmetic outcome depend directly on dermal apposition, which is the goal of any closure method. Advantages of sutures include meticulous closure and high wound tensile strength. The primary disadvantage is the skill

necessary to place them. The suture selected is dictated by morphology of the wound. To simplify selection in the wilderness environment, absorbable sutures, such as chromic gut and polyglactin (Vicryl), should be used to close deep layers and for subcuticular closures. Nonabsorbable sutures, such as nylon (Ethilon) and polypropylene (Prolene), should be used on the skin. Silk is reactive, has poor tensile strength, and should be avoided. No wound should be sutured by an individual who is inexperienced in basic surgical technique. In addition, no wound incurred in the wilderness is truly risk-free regarding infection. In general, the safest management strategy for lacerations in the wilderness setting is open management or closure with nonsuture alternatives. Surgical staples are easily placed, are nonreactive, have lower infection rates than sutures, and minimize time of closure.93 They should be avoided on areas of cosmetic importance, such as the face. Tapes and adhesives offer a preferable alternative to sutures. Tape and adhesive strips (e.g., Steri-Strips) are easily applied and require little technical ability. If a wound is appropriate for closure, tape offers a rapid, safe, painless, and inexpensive alternative to sutures and staples.27 The only requirement of tape use is conformity to principles of dermal apposition. Disadvantages of tape include need for adhesive solutions, such as benzoin; low tensile strength; and lack of applicability over any region of tension.93 A critical limiting factor in wilderness use of tape closure is the need for the wound to remain dry. Tissue adhesives in wound closure have been studied for 20 years.26 Recently, octylcyanoacrylate and similar synthetic agents have been shown to be equal in strength and cosmesis to sutures at 1 year.81 Advantages of adhesives include ease of application, safety, patient comfort, and low cost.94 Similar to tape, immediate tensile strength is poor and dehiscence is more likely compared with sutures.93 If closure is possible and other means are unavailable or impractical, adhesives may be used.

Scalp Lacerations. The extent and severity of scalp lacerations are often initially obscured by surrounding hair that is matted with blood. Hydrogen peroxide and water effectively remove blood from hair, although hydrogen peroxide should not be

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used to irrigate the wound. Interestingly, and most likely owing to the vascularity of the scalp, irrigation did not alter outcome in clean lacerations in one study.43 Hair surrounding the laceration is removed using a safety razor only if absolutely necessary to clean the wound. Hair removal should be limited to the immediate area of the laceration because the surrounding hair can later be twisted into strands and used to approximate the wound edges if necessary. Once wound margins have been identified, anesthetic should be applied. The key to examination of the scalp is determining the integrity of the galea. Significant degloving injury or galeal laceration may mandate evacuation. The scalp is highly vascularized. An extensive scalp laceration bleeds freely, and if it follows a fall or direct blow to the head, may be associated with an underlying skull fracture. Superficial scalp lacerations often bleed freely and may require pressure dressings to achieve hemostasis. Minor scalp lacerations can be effectively treated in the wilderness setting, after following the aforementioned infectionminimizing steps. Of note, debridement of scalp wounds should be kept to a minimum because it may be difficult to mobilize wound edges to cover the resulting soft tissue defect. In addition, cosmesis is not a significant concern on the hair-covered scalp. Acceptable closure of a minor scalp laceration can be performed using strands of hair to approximate wound edges. The hair on either side of the wound can be twisted into a thick bundle. The opposing bundles are then pulled together and crossed. They can be secured with a drop of tissue glue or tied together if glue is not available (see Figure 21-45). This method minimizes shaving.

Facial Lacerations. Facial lacerations are relatively simple to manage because they rarely damage underlying structures and are well vascularized. If suspicion exists regarding damage to cranial nerves or the parotid duct, the wound should be managed in an open fashion. Debridement should be limited to obviously necrotic tissue. Because of vascularity of the face, infection is rare, and most wounds can be closed. For small wounds, tape is a useful closure technique. Torso Lacerations. Torso lacerations require evaluation for fascial penetration. Anterior fascial penetration in the torso converts the wound from a skin wound to one requiring management of underlying chest or abdominal structures. Tissue debridement may be more aggressive over the torso because surrounding tissue planes can be mobilized for closure. Adipose tissue should not be approximated with sutures, and subdermal dead space should be obliterated with deep, nonadipose approximating sutures.

Hand Injuries Severe contusions to the hand commonly occur with crush or rope injuries. The hand should be carefully protected if marked swelling and pain with motion are present. If no joint instability or fracture is identified, a bulky hand dressing should be applied with the wrist dorsiflexed 10 degrees, the thumb abducted, and the metacarpophalangeal joints flexed 90 degrees, known as the position of function. Cotton wadding or bandages can be placed in the palm and between the fingers, and an elastic bandage can be used as an overwrap. A volar

splint allows this position to be maintained until definitive care is reached. Lacerations of the finger flexor or extensor tendons occur with accidents involving knives or other sharp objects. A flexor tendon laceration, partial or complete, can be a serious problem if not repaired early. The open wound should be cleansed and loosely taped closed if no infection risk factors are present, and the finger should be splinted in slight flexion at the interphalangeal joints and in 90 degrees of flexion at the metacarpophalangeal joint. To achieve optimal results, this injury should be managed by a hand surgeon within the first 3 to 5 days. For an extensor tendon, the open wound should be cleansed and taped closed, and a splint should be applied with the metacarpophalangeal joint in slight flexion and the interphalangeal joint extended. The victim should be seen by an orthopedic surgeon within 7 days. The nerves most commonly injured by laceration include the superficial radial nerve at the wrist, ulnar nerve at the elbow or wrist, and median nerve at the wrist. Digital nerves are commonly lacerated in accidents with knives. In general, the wound should be cleansed and taped loosely and a splint should be applied to the wrist and hand. The victim should see a hand surgeon within 7 days.

Puncture Wounds Puncture wounds carry significant infection risk where organic contamination is frequent. Significant puncture wounds to the torso should be treated according to the guidelines outlined in the section on penetrating trauma to the chest and abdomen. Puncture wounds to the extremities should be unroofed if they are proximal to the wrist or ankle. The unroofed wound should be irrigated as previously described and then packed open with sterile gauze. Delayed primary closure with tape can occur at 48 to 96 hours. Puncture wounds to the hands and feet should not be explored in the absence of detailed knowledge of anatomy. If this expertise is not available, the wound should be cleaned and the victim started on antibiotics, such as cephalexin (Keflex) 500 mg PO q6h. If the skin is punctured with a fishhook, the skin surrounding the entry point should be cleansed with soap and water. Fishhook removal techniques are discussed in Chapter 22.

Antibiotic Use and Infectious Complications The use of prophylactic antibiotics for wounds incurred in the wilderness is not recommended. Antibiotic treatment usually begins after the injury has occurred and therefore is never truly “prophylactic.” The use of antibiotics in lacerations and bite wounds should be confined to victims with significant infection risk factors, such as animal bites, heavily contaminated wounds, or comorbid medical conditions. This includes high-risk wounds, such as puncture wounds and those occurring on the hands. Debridement and irrigation are far more important than antibiotics in eliminating infection and remain the mainstay of risk reduction in any wound incurred in the wilderness. If antibiotics are indicated, selection should be tailored by available resources and coverage of likely contaminating organisms. Many single-agent broad-spectrum oral antibiotics are available. If any sign of infection develops in a wound, closed or open, including pain, discharge, erythema, edema, or fever, antibiotics should be administered. In an infected closed wound, the adhesive or sutures should be removed and the wound

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TABLE 20-4. Differential Diagnostic Features of Abdominal Pain LOCATION OF PAIN AND PRIOR ATTACKS

DISEASE Acute appendicitis

MODE OF ONSET AND TYPE OF PAIN

ASSOCIATED GASTROINTESTINAL PROBLEMS

Periumbilical or localized generally to right lower abdominal quadrant Diffuse

Insidious to acute and persistent

Anorexia common; nausea and vomiting in some

Sudden; crampy

Vomiting common

Epigastric; history of ulcer in many Left lower quadrant; history of previous attacks

Abrupt; steady

Anorexia; nausea and vomiting Diarrhea common

Insidious to acute

Anorexia; nausea and vomiting

Acute pancreatitis Acute salpingitis

Epigastric or right upper quadrant; may be referred to right shoulder Costovertebral or along course of ureter Epigastric penetrating to back Bilateral adnexal; later, may be generalized

Sudden; severe and sharp Acute; persistent, dull, severe Gradually becomes worse

Frequently nausea and vomiting Anorexia; nausea and vomiting common Nausea and vomiting may be present

Ectopic pregnancy

Unilateral early; may have shoulder pain after rupture

Sudden or intermittently vague to sharp

Frequently none

Intestinal obstruction Perforated duodenal ulcer Diverticulitis Acute cholecystitis Renal colic

Gradual; steady or crampy

irrigated. Wet-to-dry dressings with normal saline should be started and the wound closely observed. Elevation and splinting may assist in relieving pain.

Management of Animal Attacks and Bite Wounds See Chapters 51 to 53.


WILDERNESS SURGICAL EMERGENCIES

The Acute Abdomen In the wilderness, the critical distinction between the surgical and nonsurgical abdomen determines whether the victim should be evacuated. A myriad of nonsurgical conditions mimic a surgical abdomen. It has been extensively reported that the bite of the black widow spider Latrodectus mactans can induce abdominal pain indistinguishable from a surgical acute abdomen,51 and mushroom ingestion can cause severe gastroenteritis.85 Pain, anorexia, nausea, vomiting, and fever are characteristic manifestations of an acute abdominal disorder. Tenderness and guarding are the hallmarks of peritoneal irritation and suggest that operation is indicated. The approach to someone with abdominal pain begins with a detailed history that includes age, sex, systemic symptoms, and past medical history. This information provides a framework for more detailed questioning about the character of the pain, its mode and time of onset, severity, and precipitating and palliating factors. In persons 15 to 40 years of age, women are more likely to have abdominal pain, but men have a higher incidence of

PHYSICAL EXAMINATION Low-grade fever; epigastric tenderness initially; later, right lower quadrant Abdominal distention; highpitched rushes Epigastric tenderness; involuntary guarding Fever common; mass and tenderness in left lower quadrant Right upper quadrant pain Flank tenderness Epigastric tenderness Cervical motion elicits tenderness; mass if tuboovarian abscess is present Adnexal mass; tenderness

surgical disease. Common genitourinary causes for abdominal pain in men include epididymitis, renal colic, urinary retention, and testicular torsion. Common causes in women include pelvic inflammatory disease (PID), urinary tract infection, dysmenorrhea, ruptured ovarian cyst, and ectopic pregnancy. Pain is the hallmark of a surgical abdomen (Table 20-4). It can be characterized by nature of onset, severity, location, and precipitating factors. The onset of abdominal pain can be explosive, rapid, or gradual. The person who is suddenly seized with explosive, agonizing pain is most likely to have rupture of a hollow viscus into the free peritoneal cavity. Colic of renal or biliary origin may also be sudden in onset, but seldom causes pain severe enough to prostrate the victim. If someone has rapid onset of pain that quickly worsens, acute pancreatitis, mesenteric thrombosis, or small bowel strangulation should be suspected. The person with gradual onset of pain is likely to have peritoneal inflammation, such as that accompanying appendicitis or diverticulitis. Severity of the pain may be characterized as excruciating, severe, dull, or colicky. Excruciating pain unresponsive to narcotics suggests an acute vascular lesion, such as rupture of an abdominal aneurysm or intestinal infarction. Both conditions are unusual in the wilderness environment. Severe pain readily controlled by medication is characteristic of peritonitis from a ruptured viscus or acute pancreatitis. Dull, vague, and poorly localized pain suggests an inflammatory process and is a common initial presentation of appendicitis. Colicky pain characterized as cramps and rushes is suggestive of gastroenteritis. The pain from mechanical small bowel obstruction is also colicky but has a rhythmic pattern, with pain-free intervals alternating with severe colic. The peristaltic rushes associated with gastroenteritis are not necessarily coordinated with colicky pain.

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Physical examination of the abdomen is initiated by inspection. Valuable clues to the underlying condition that may be obtained in this manner include stigmata of cirrhosis, distention, hyperperistalsis, or incarcerated hernia. The victim may not be able lie still, which is indicative of renal or biliary colic. Persons lying perfectly still frequently have peritoneal inflammation. Auscultation is helpful if the classic “rushes and tinkles” of small bowel obstruction are present. Palpation in the wilderness setting is most helpful in documenting the presence or absence of peritoneal signs. Shake or percussive tenderness, particularly in the context of fever, nausea, and or vomiting, indicates a need for evacuation. Rectal and vaginal examinations should be performed as dictated by the clinical presentation and setting.

General Field Treatment Principles When evaluating someone with a possible emergent surgical condition in the wilderness, correctly identifying the etiology of a given condition is less important than identifying peritoneal inflammation and the need for operation. When dealing with a surgical abdomen or other condition requiring evacuation, adjuncts to definitive hospital treatment can be initiated in the field. Dehydration and intravascular volume depletion accompany many surgical conditions, particularly when the disease process has progressed and evacuation is delayed. Crystalloid resuscitation in the field is beneficial for patients who have developed or have the potential to develop septic or hypovolemic shock. Dehydration is common in the wilderness, and frank hypovolemia can result from vomiting associated with gastroenteritis, appendicitis, renal colic, and small bowel obstruction. Perforated viscus, pancreatitis, cholecystitis, small bowel obstruction, PID, and necrotizing soft tissue infections all may feature volume depletion. The goal in the wilderness setting is to recognize the signs of hypovolemia and initiate resuscitation to decrease perioperative morbidity. Nasogastric tube decompression of the stomach may help alleviate emesis secondary to abdominal pain or obstruction. Large-bore (i.e., 18-fr) catheters are best and can be easily aspirated with a syringe. Placement should be confirmed by aspiration of gastric contents or auscultation of gastric air upon insufflation of the stomach. Foley catheters are becoming increasingly more available in wilderness first-aid kits. Recording urine output provides an effective estimate of intravascular volume status. Foley catheter placement should never hinder the possibility of ambulatory evacuation.

Appendicitis Acute appendicitis is the most common cause of a surgical abdomen in persons younger than 30 years of age. Acute appendicitis is really more than a single disease entity. In terms of physical signs and symptoms, appendicitis proceeds from inflammation to obstruction to ischemia to perforation, all within approximately 36 hours. Symptoms reflect the stage of the disease. Unfortunately, the time frame for the progression of clinical events is highly variable. Differential diagnosis of appendicitis includes gastroenteritis and mesenteric adenitis, the most common inflammatory disorders in adults. The first symptom of gastroenteritis is typically vomiting, which precedes the onset of pain and is often associated with diarrhea; it is rarely associated with localizing signs

or muscular spasm. Bowel sounds are usually hyperactive. A rectal examination rarely shows abnormalities in gastroenteritis but frequently does in adults with appendicitis. Mesenteric adenitis is often preceded by an upper respiratory infection and is associated with vague abdominal discomfort that often begins in the right lower quadrant. Abdominal examination reveals only mild right lower quadrant tenderness that is often poorly localized. The incidence of PID in young women with abdominal pain confounds the diagnosis of appendicitis. Some clinicians have documented a relationship between menses and onset of pain. If abdominal pain occurs within 7 days of menses, the incidence of PID is twice that of appendicitis. If onset of pain occurs greater than 8 days from menses, appendicitis is twice as likely as PID. This history with a pelvic examination may enable the examiner to differentiate between the two entities. Acute appendicitis mandates evacuation because untreated perforation is associated with significant mortality. Broadspectrum antibiotics (if IV capability, cefotetan [Cefotan] 2 g IV q12h, or as an alternative, piperacillin/tazobactam [Zosyn] 3.375 g IV q6h; if only oral antibiotic capabilities, a fluoroquinolone, such as ciprofloxacin [Cipro] 750 mg PO bid) should be initiated, attempting coverage against gram-negative and anaerobic organisms. IV crystalloid resuscitation should be initiated, particularly if the victim is older or perforation is suspected, and the victim should be placed at bowel rest.

Acute Cholecystitis and Biliary Colic Biliary colic refers to pain induced by obstruction of the cystic duct, usually by gallstones. The label of this condition as “colic” is a misnomer because the pain is usually constant. The condition is rarely seen before adulthood and is several times more common in women than in men. A sufferer often relates a past history of gallstones and previous episodes of similar pain, which is described as constant right upper quadrant or epigastric pain, radiating to the right scapula and back. Onset ranges from insidious to acute and frequently follows a meal. The episode usually lasts 15 minutes to 1 hour and then abates.67 If pain is severe, nausea and vomiting may be present (60% to 70%). Acute cholecystitis is an infection of the gallbladder secondary to cystic duct obstruction, usually from gallstones. In the wilderness setting, it is useful to think of these interrelated conditions as a continuum of one unified disease process. Both biliary colic and cholecystitis present with right upper quadrant pain; however, biliary colic has the potential to be self-limiting and may not require evacuation. Not all persons with biliary colic develop cholecystitis, and signs of infection should be excluded. Cholecystitis symptoms typically escalate in severity. Pain that persists more than 1 to 2 hours is suspect for cholecystitis, particularly when accompanied by fever, more significant nausea and vomiting, and right upper quadrant tenderness. Studies have shown that fever may be an unreliable predictor of severity of infection.38 Acute cholecystitis mandates hospitalization, and evacuation plans should be instituted. The disease can progress to gangrenous changes in the gallbladder wall, leading to perforation and death if untreated. The definitive treatment of cholecystitis is cholecystectomy. In the field, IV antibiotics (ampicillin/sulbactam [Unasyn] 3 g IV q6h) or an oral alternative (ciprofloxacin [Cipro] 750 mg PO

Chapter 20: Wilderness Trauma, Surgical Emergencies, and Wound Management bid) should be given, directed at common biliary organisms, including Escherichia coli and Klebsiella, Bacteroides, Enterobacter, Streptococcus, and Proteus species. Oral antibiotics with optimal bioavailability should be initiated in the absence of parenteral forms, ensuring the broadest spectrum of coverage available. As with most abdominal infections, IV hydration should be started in the field. If significant nausea and vomiting are present, NG decompression may improve comfort and prevent aspiration.

Peptic Ulcer Disease The incidence of peptic ulcer disease (PUD) is decreasing in the United States. With the advent of treatment of Helicobacter pylori infections and the variety of acid-reducing agents available, PUD is now rarely seen by surgeons. The exception is perforation of a gastric or duodenal ulcer, which should be considered in the differential diagnosis of acute abdomen in the wilderness. Victims frequently relate a history of PUD and need for medication. This history, in combination with acute onset of unrelenting epigastric pain radiating to the back, is suspect for perforation of an ulcer. The physical examination greatly assists in differentiation between simple ulcer disease symptoms and perforation. Pain may be severe. Gastric secretions are caustic to the peritoneum and, as a result, the abdomen frequently displays a rigid, boardlike character with associated diffuse peritoneal signs. History and examination consistent with gastric or duodenal perforation mandate evacuation. Dehydration may be significant. IV resuscitation should be started and the victim placed on bowel rest.

Diverticulitis Diverticulitis is localized infection of a colonic diverticulum. Impacted material in the diverticulum, usually feces, leads to a localized inflammatory process that can lead to abscess formation and perforation. Diverticulitis presents over a wide range of severity, from mild, localized infection to intra-abdominal catastrophe. It is more common in middle age; one third of the population older than 45 years of age has diverticula, 20% of whom will develop diverticulitis.89 Victims often relate a history of previous attacks. Pain is typically described as gradual in onset and localized in the left lower quadrant of the abdomen, although right-sided diverticulitis can occur. Diarrhea and fever are frequently associated complaints. Examination findings range from mild left lower quadrant abdominal tenderness to frank peritonitis, depending on the severity of the underlying infection. Treatment in the wilderness setting consists of hydration, bowel rest, antibiotics, and evacuation. If evacuation is impossible or significantly delayed, oral broad-spectrum antibiotics may be effective. Mild cases of diverticulitis are frequently treated on an outpatient basis with broad-spectrum oral antibiotics,83 such as ciprofloxacin 750 mg PO bid. Antibiotic therapy is directed primarily at gram-negative aerobic and anaerobic bacteria, and single-agent therapy covering these organisms has been demonstrated to be as effective as multiple-agent regimens.50 Because of unpredictability of response to antibiotic treatment, evacuation is indicated.

Mechanical Small Bowel Obstruction Small bowel obstruction is a true emergency in the wilderness. When the obstruction is complete, expedient surgery is the only

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treatment. Small bowel obstruction in the United States is almost invariably the result of adhesions from previous laparotomy or incarceration of abdominal hernias, and the history often makes the diagnosis. Victims complain of sudden onset of diffuse, crampy abdominal pain associated with vomiting and obstipation. With progression of the process to strangulation and infarction of bowel, fever and tachycardia develop. Late physical examination findings reveal a distended, tympanitic abdomen. Although variable, high-pitched tinkling bowel sounds suggest obstruction. A thorough inspection for hernias should be performed. Progression of examination findings to frank peritonitis is alarming and suggests ischemic bowel. The adage, “Don’t let the sun set on a small bowel obstruction,” is sound advice in the wilderness setting. All persons suspected of having a small bowel obstruction should be evacuated immediately. In the interim, the stomach should be decompressed with an NG tube to relieve vomiting and abdominal distention, and aggressive IV hydration should be started.

Incarcerated Abdominal Wall Hernias Abdominal wall hernias are common; groin herniorrhaphy is the most common major general surgical operation performed in the United States.63 Hernias can become incarcerated or strangulated, which constitutes a surgical emergency. Seventyfive percent of hernias occur in the groin86; the majority of incarcerated hernias presenting in the wilderness setting are inguinal hernias. Other common hernias with the capacity for incarceration are incisional and umbilical hernias. Many people live with bulging asymptomatic hernias. Others manually reduce symptomatic hernias. New painful hernias or known hernias that can no longer be reduced are concerning. The pain of inguinal hernias is usually intermittent. A description of constant pain is suspect for incarceration. Associated symptoms of fever, tachycardia, nausea, and vomiting are indicative of possible incarceration or strangulation. On physical examination, a mass should be sought along the course of the spermatic cord. Masses may present from the external inguinal ring to the scrotum. The differential diagnosis for painful inguinal or scrotal masses includes lymphadenopathy, testicular torsion, and epididymitis. Associated tenderness of the spermatic cord may be present. A painful mass at the umbilicus, a previous incision site, or below the inguinal ring could represent an incarcerated umbilical, incisional, or femoral hernia, respectively. Bowel within an incarcerated hernia sac can become gangrenous in as little as 4 to 5 hours63; therefore, it is important to determine the time of incarceration. The decision to evacuate is influenced by the presence of contraindications to manual reduction (see later), which are essentially physical signs that suggest progression to strangulation. Femoral hernias should not be reduced. The danger is en masse reduction of compromised or gangrenous bowel. Contraindications to reduction include associated signs of toxicity, such as fever, tachycardia, or evidence of bowel obstruction in association with a painful, irreducible mass. If the hernia itself is exquisitely tender to palpation and the overlying skin is erythematous and warm, the hernia should not be reduced. Victims with incarcerated hernias with signs of systemic or local toxicity should be evacuated. Similarly, victims with irreducible hernias—which require emergent surgery—should be evacuated.

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A newly incarcerated hernia without contraindications to reduction may be reduced by personnel experienced in such techniques. Gentle pressure is exerted on the hernia mass toward the inguinal ring, optimally with the victim flat and hips elevated. Analgesia and sedation may aid in reduction. Gangrenous bowel can rarely be reduced by this method.93 If successful, the victim should be closely observed for signs of recurrence or abdominal pain.

Urologic Emergencies Renal colic describes a symptom complex resulting from acute obstruction of the urinary tract secondary to calculus formation. The goal of the wilderness physician is to recognize the symptom complex and institute treatment. After obstruction of the urinary tract, the pain crescendo of renal colic begins in the flank. The pain progresses anteriorly over the abdomen and radiates to the groin and testes in men and the labia in women. Because the autonomic nervous system transmits visceral pain, many abdominal complaints may manifest. Nausea and vomiting are common. With severe colic, the victim writhes in pain and is unable to find a comfortable position. Physical findings are less revealing than is the review of systems. Tenderness to deep palpation of the region of obstruction or to percussion of the flank is present. Diagnosis in the wilderness is assisted by the presence of gross hematuria. Management of ureteral colic is pain control. Although almost universally deployed, forced diuresis may reduce ureteral peristalsis. Thus, forced oral fluids or aggressive IV hydration are of questionable benefit.100 The majority of calculi pass spontaneously in 4 to 6 hours. The goal of management is to control pain until passage of the stone has occurred. A number of pharmacologic approaches may be used. Nonsteroidal antiinflammatory drugs, such as ibuprofen and ketorolac, have been shown to be effective in the management of renal colic.100 For symptoms uncontrolled by anti-inflammatory agents, narcotics may be added. Narcotic analgesics are most effective given parenterally; however, agents such as meperidine (Demerol), codeine, and hydromorphone (Dilaudid) may be given orally. Anti-inflammatory agents and analgesics can be combined. An antiemetic may be added to relieve nausea. When administering pain medication in the field, particular attention should be given to airway maintenance and induced nausea and vomiting. Any person whose symptom complex cannot be controlled must be evacuated. Additional indications for evacuation include calculus anuria and evidence of obstruction-induced infection.

Urinary Retention Urinary retention is a painful experience that requires immediate medical, and often surgical, intervention.13 The etiology of urinary retention ranges from prostatism48 in men to atonic bladder in women. In general, causes have been broadly divided into four groups: obstructive, neurologic, pharmacologic, and psychogenic.99 Twenty-five percent of men reaching 80 years of age will experience acute retention,13 which has been shown to increase prostate surgery perioperative mortality rates.76 Acute urinary retention can lead to incapacitating symptoms in the wilderness; prompt recognition and intervention are necessary. Principal symptoms are bladder distention and pain that may mimic acute abdomen, overflow incontinence, dribbling, and hesitancy. Physical examination findings include prostatic enlargement in men and lower midline abdominal tenderness and distention. If painful distention of the bladder is present, decompression should be undertaken.

A

B Figure 20-10. A, OPTION-vf (female) catheter. B, OPTION-vm (male) catheter. (Courtesy Opticon Medical, Dublin, OH)

Bladder decompression should be initially attempted with a standard Foley catheter. In men with prostatic hypertrophy, passage of the catheter may be challenging, and a large catheter or coudé catheter should be used if a standard Foley catheter cannot be passed. Instrumentation of the urethra with hemostats or dilators is dangerous and should not be attempted in the field. Recently introduced are the OPTION-vf (female; Fig. 20-10A) and OPTION-vm (male; see Fig. 20-10B) (Option Medical, Dublin, Ohio), which are valved urinary catheters that eliminate the need for urine drainage bags and connecting tubes normally required with Foley catheters. These catheters incorporate a manually activated valve at the end of the catheter that allows the patient to store urine in the bladder and to mimic normal voiding behavior. The catheters may be used with a continuous drainage adapter when appropriate, so that a bag may be placed and urination rate and volume assessed. If multiple attempts are unsuccessful and symptoms are severe, needle decompression is indicated. The skin of the suprapubic region should be anesthetized, if possible. The distended bladder is palpated to guide aspiration. A 22-gauge needle attached to a syringe is introduced through the skin of the lower abdomen two finger breadths above the pubic symphysis and directed at the anus. The needle is advanced with simultaneous aspiration of the syringe until free-flowing urine is visualized. Palpation of the bladder in combination with adherence to this technique should lead to successful decompression. Complications related to decompression can occur.84 Drainage of greater than 300 mL/hr can induce mucosal hemorrhage. In addition, 10% of victims develop postobstructive

Chapter 20: Wilderness Trauma, Surgical Emergencies, and Wound Management diuresis that may lead to dehydration, in which case aggressive oral hydration or crystalloid repletion should be undertaken. Finally, it must be recognized that surgical decompression is temporizing and retention will recur. Treatment may need to be continued or repeated. Drainage of the bladder acutely relieves symptoms and may allow ambulatory evacuation, but the underlying etiology must be addressed in a medical facility.

The Acute Scrotum Acute onset of scrotal pain and swelling requires immediate attention. Etiologies are multiple, but incarcerated hernia and testicular torsion are the most clinically significant in the field. Although any one aspect of the history and physical examination may not be diagnostic, when taken as a whole, they frequently suggest the etiology of the scrotal pathology.49 Testicular torsion can occur at any age, but it is more likely near puberty. The likelihood of testicular salvage is inversely proportional to elapsed time from torsion; this is a true surgical emergency. Acute onset of severe testicular pain is the hallmark. Mild to moderate pain is more suggestive of torsion of a testicular appendage or epididymitis. It has been stated that victims who can ambulate with minimal pain are less likely to have testicular torsion. In addition, nausea and vomiting may accompany torsion, whereas fever, dysuria, and frequency are associated with epididymitis. Physical examination reveals a patient in extreme discomfort with a swollen scrotum and a tender testicle; the affected testicle may be higher than normal and have a horizontal lie.49 Scrotal skin may be edematous and discolored. Unilateral scrotal swelling without skin changes is more indicative of a hernia or hydrocele. In testicular torsion, the affected testis is often larger than the unaffected side. Testicular torsion can be somewhat differentiated from acute epididymitis by Prehn’s sign,88 which is relief of pain accomplished by elevation of the testicle. Because torsion twists the spermatic cord and elevates the testicle, pain is not relieved by elevation (negative Prehn’s sign). Conversely, pain is relieved in epididymitis with elevation (positive Prehn’s sign). This maneuver has low sensitivity in distinguishing the two conditions, but may be helpful in conjunction with other findings.88 Treatment consists of surgical detorsion, which should be accomplished within 12 hours of torsion.49 Manual detorsion is not the treatment of choice; however, remoteness of the wilderness environment may mandate manual attempts. Studies of manual detorsion are scant and the cohorts small.41 If manual detorsion is necessitated, the victim should be placed supine. Because testicular torsion typically occurs in the medial direction, detorsion is initially attempted with outward rotation of the testis (toward the ipsilateral thigh). Simultaneous rotation in the caudal to cranial direction may be necessary to release the cremasteric muscle.31 The surgical treatment of testicular torsion includes pexis of the testis to prevent recurrent torsion. Thus, although detorsion may temporize an acute situation in the field, all victims must be evacuated for definitive treatment.

Prostatitis Fifty percent of men experience prostatic symptoms in their adult life.77 A number of forms of prostatitis have been defined, including viral, bacterial (5%), nonbacterial (65%), and chronic forms, as well as prostatodynia.79 The acute bacterial form may potentially lead to severe infection.

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Bacterial prostatitis is an infection of the prostate caused primarily by gram-negative bacteria, with 80% attributable to E. coli. It is an acute, febrile illness characterized by perineal pain radiating to the low back, chills, malaise, and voiding symptoms, such as urgency, frequency, and dysuria. Urinary retention is common, and cystitis frequently accompanies the infection. On rectal examination, the prostate gland is usually boggy, warm, and tender and enlargement is variable. In an ideal situation, treatment is individualized to the cause, which may be difficult to discern in the wilderness. The infection may respond to an oral antibiotic such as ciprofloxacin (750 mg PO bid), ampicillin (500 mg PO qid), or trimethoprim (80 mg with sulfamethoxazole 400 mg PO bid). Penetration of prostatic secretions has been shown to be best achieved by trimethoprim/sulfamethoxazole (TMP/SMX). The chosen antibiotic should be administered for 30 days. If retention is present, catheterization or suprapubic aspiration should be undertaken. Acute bacterial prostatitis can escalate in severity to systemic toxicity. Persons with evidence of systemic toxicity unresponsive to a trial of oral or parenteral antibiotic therapy should be evacuated.

Urinary Tract Infection Urinary tract infections (UTIs) are extremely common and include episodes of acute cystitis and pyelonephritis occurring in otherwise healthy individuals. These infections predominate in women; approximately 25% to 35% of women 20 to 40 years of age report having had a UTI.45 Conversely, men between the ages of 15 and 50 years rarely develop a UTI. Despite the striking difference in prevalence, symptoms are similar between men and women. The symptoms may represent urethritis, cystitis, or an upper UTI; the distinction is often difficult. Common symptoms include frequency, urgency, dysuria, suprapubic pain, flank pain, and hematuria. Flank pain with tenderness to percussion suggests pyelonephritis. On urinalysis, pyuria is nearly invariably present and hematuria may assist in the diagnosis. Definitive diagnosis is based on significant bacteriuria. The leukocyte esterase test has a screening sensitivity of 75% to 96% and a specificity of 94% to 98% in detecting greater than 10 leukocytes per high-power field.45 Treatment in the wilderness setting for both men and women should be directed at the most common causative agents, although 50% to 70% of cases resolve spontaneously if untreated. Causative bacteria include E. coli (70% to 95%); Staphylococcus species (5% to 20%); and, less frequently, Klebsiella, Proteus, and Enterococcus. Fortunately, oral antibiotics are highly effective. Although resistant E. coli strains are being reported, TMP/SMX (Bactrim DS) is an excellent first-line drug. Alternative regimens include nitrofurantoin, a fluoroquinolone, or a third-generation cephalosporin. A 3-day course of therapy has been shown to be more effective than single-dose therapy.45 For pyelonephritis, a similar antibiotic in a 10- to 14-day course is acceptable initial treatment. Evacuation should be reserved for systemic toxicity unresponsive to oral antibiotics.

Gynecologic Emergencies See Chapter 88.

Skin and Soft Tissue Infections Poor hygiene, superficial skin wounds, blisters, dermatologically significant plants, and insect bites contribute to disruption of the skin barrier. Most often seen are superficial pyodermas

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that do not extend beyond the level of the skin. These include erysipelas, impetigo, folliculitis, furunculosis, and carbunculosis. The majority of superficial skin infections are self-limited. However, with less than optimal hygiene and limited resources, skin infections may progress to deep soft tissue infections.

Cellulitis Cellulitis is acute infection of the skin involving subcutaneous tissue. The superficial form of cellulitis, erysipelas, is identified by well-demarcated, warm, and erythematous plaques with raised borders. The face, scalp, hands, and lower extremities are most often affected. Cellulitis is frequently preceded by a superficial wound. In the wilderness setting, there are ongoing infection risk factors. Members of expeditions may be physically stressed and nutritionally depleted. High altitude is associated with immunosuppression. Clostridium species and other pathogens are ubiquitous in the soil, and proper initial wound care may be suboptimal. Under such conditions, cellulitis can progress to abscess formation and tissue necrosis, leading to septicemia. Wounds that develop erythematous, warm, and boggy margins should be treated with antibiotics and closely observed. The margins of erythema should be marked to gauge progression. Treatment consists of proper wound hygiene and antibiotic therapy. Local wound measures include elevation, application of moist heat every 4 to 6 hours, and immobilization. Antibiotic therapy is directed at common causative pathogens. Group A streptococci and Staphylococcus aureus are most commonly implicated. If complications occur and the cellulitis appears to be progressing, a mixed infection is likely. Because Gram’s stain and culture-directed therapy are not possible, the most broad-spectrum antibiotic available should be administered. Parenteral antibiotics are indicated for serious or mixed infections. Penicillin G (1 to 2 million units q2–3h) is recommended, with first-generation cephalosporins as an alternative. Because oral antibiotics may be the only available therapy, they should be initiated early in the field. Suggested agents include erythromycin (for the penicillin-allergic victim); cephalexin; a macrolide, such as clarithromycin; or a fluoroquinolone, such as ciprofloxacin or levofloxacin.

purulent fluid has amassed below the dermis and rupture is impending. Warm soaks and observation are recommended by some clinicians, particularly if the presence of drainable pus is uncertain. However, the definitive treatment is drainage. Antibiotics are recommended if significant associated cellulitis is present, but penetration may be poor. Local anesthesia should be administered before incision. The lesion should be incised in line with tissue planes over the point of maximum fluctuance. The value of cruciate incisions over linear incisions is debatable; the important feature is assurance of adequate drainage to prevent recurrence. If drainage is undertaken, the incision must be large enough to adequately drain the cavity. All purulent material should be evacuated and the cavity copiously irrigated with saline or water. Packing is unnecessary if continued drainage is ensured. The wound should be covered with a sterile dressing, changed two to three times per day with concurrent irrigation, and closely observed for reaccumulation of purulence.

Necrotizing Infections

Abscess Formation

Necrotizing skin and soft tissue infections are life-threatening conditions caused by virulent, toxin-producing bacteria. Depth of tissue involvement is variable and may involve skin, fascia, or muscle. The etiology of necrotizing infections is related to breaks in normal cutaneous defenses associated with some form of injury. Although rare, such infections are of importance to the wilderness physician because of the array of documented inciting injuries and the reduction in mortality possible if diagnosis and treatment are rapid.28 Necrotizing infections have developed after innocuous-appearing injuries, including simple scratches, insect bites, ankle sprains, and sore throats.37 The incidence of necrotizing soft tissue infections is unknown, and there is no age or sex predilection. They most commonly occur on the extremities, abdominal wall, and perineum, within 1 week of the inciting event. Common pathogens include Streptococcus species, Staphylococcus, Vibrio species, Clostridium, Pseudomonas, Aeromonas, Enterobacter, and fungi. Many infections become polymicrobial. The clinical manifestations can be subtle. An area of cellulitis is commonly the first indication of infection. Pain is often excruciating, and fever is usually present. The infection then progresses to spreading erythema, induration, blue-black discoloration, and blister formation. Necrosis of skin, subcutaneous fat, muscle, or fascia follows, depending on the organism involved. Necrotic tissue exudes a foul-smelling, watery “dishwater” fluid. Subcutaneous emphysema may be present, particularly with clostridial infections, although enteric organisms may also produce air in tissues. Unfortunately, treatment is limited in the wilderness environment. Debridement of infected tissue should be carried out to the greatest degree humanely possible, but further debridement in a hospital setting is invariably necessary. The extent of debridement necessary is often striking. After debridement, parenteral antibiotics are necessary. Vancomycin and gentamicin are appropriate first-line agents. The most broad-spectrum oral antibiotic available should be initiated, and the victim expeditiously evacuated. Time is of the essence because the infection can be halted only by aggressive surgical intervention.

When untreated, many superficial skin infections convert to abscesses. Development of a raised, fluctuant mass with overlying warmth and erythema should raise suspicion that surgical drainage is necessary. Frequently, the lesion will “point” when

The references for this chapter can be found on the accompanying DVD-ROM.

Lymphangitis Acute lymphangitis is an infectious process involving subcutaneous lymphatic channels. Its recognition in the wilderness setting is important relative to its propensity to follow puncture wounds, hand wounds, infected blisters, and animal bite wounds. Clinical presentation involves linear erythematous streaks that originate in the lymphatic drainage basin of the wound and “point” to the draining nodal group. Causative agents are similar to those common for cellulitis, with the addition of Pasteurella multocida from animal bite wounds. Treatment consists of antibiotics, warm, moist soaks every 4 to 6 hours, and immobilization and elevation of the extremity. Optimal treatment consists of parenteral antibiotics, but as with cellulitis, oral agents should be initiated if parenteral drugs are not available. Broad-spectrum agents with good oral bioavailability and gram-positive coverage are recommended.87

Chapter 21: Improvisation in the Wilderness

Improvisation in the Wilderness

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21

Eric A. Weiss and Howard J. Donner

At the heart of wilderness medicine is improvisation, a creative amalgam of formal medical science and common sense problem solving. Defined as “to fabricate out of what is conveniently at hand,” improvisation encompasses many variations, is governed by few absolute rights and wrongs, and is limited more often by imagination than by personnel or equipment.


GENERAL GUIDELINES When working with an improvised system, test the creation on a noninjured person (“work out the bugs”) before applying it to a victim. Include materials that lend themselves to improvisation in the wilderness survival kit to enhance efficiency. Creativity is needed when searching for improvisational materials. The victim’s gear can provide needed items (e.g., backpacks can be dismantled to obtain foam pads and straps). When possible, practice constructing improvised systems before they are required in an actual rescue.


IMPROVISED AIRWAY MANAGEMENT

Airway obstruction in the semiconscious or unconscious victim is usually caused by relaxation of the oropharyngeal muscles, which allows the tongue to slide back and obstruct the airway. If only one rescuer is present, maintaining a patent airway with the jaw-thrust or chin-lift technique precludes further first-aid management. You can improvise a nasal trumpet type of airway from a Foley catheter, radiator hose, solar shower hose, siphon tubing, or inflation hose from a kayak flotation bag or sport pouch. Establish a temporary airway by attaching the anterior aspect of the victim’s tongue to the lower lip with two safety pins (Fig. 21-1). An alternative to puncturing the lower lip is to pass a string through the safety pins and hold traction on the tongue by securing the other end to the victim’s shirt button or jacket zipper.

Surgical Airway (Cricothyrotomy) Cricothyrotomy—establishment of an opening in the cricothyroid membrane—is indicated to relieve life-threatening upper airway obstruction when a victim cannot be ventilated effectively from the mouth or nose and endotracheal intubation is

not feasible. This may occur in a victim with severe laryngeal edema or with trauma to the face and upper larynx. Cricothyrotomy may also be useful when the person’s upper airway is obstructed by a foreign body that cannot be extracted by a Heimlich maneuver or direct laryngoscopy. In the wilderness, you can perform cricothyrotomy by cutting a hole in the thin cricothyroid membrane and placing a hollow object into the trachea to allow ventilation (Box 21-1). Locate the cricothyroid membrane by palpating the victim’s neck, beginning at the top. The first and largest prominence felt is the thyroid cartilage (“Adam’s apple”); the second prominence (below the thyroid cartilage) is the cricoid cartilage. The small space between these two, noted by a small depression, is the cricothyroid membrane (see Figure 21-4). With the victim lying on his or her back, cleanse the neck around the cricothyroid membrane with an antiseptic if one is readily available. Put on protective gloves. Make a vertical 1-inch (2.54 cm) incision through the skin with a knife over the membrane (go a little bit above and below the membrane) while using the fingers of your other hand to pry the skin edges apart. Anticipate bleeding from the wound. After the skin is cut apart, puncture the membrane by stabbing it with your knife or other sharp, penetrating object (see Figure 21-5A). Stabilize the larynx between the fingers of one hand, and insert the improvised cricothyrotomy tube through the membrane with your other hand (see Figure 215B). Secure the object in place with tape. Complications associated with this procedure include hemorrhage at the insertion site, subcutaneous or mediastinal emphysema resulting from faulty placement of the tube into the subcutaneous tissues rather than into the trachea, and perforation through the posterior wall of the trachea with placement of the tube in the esophagus.

Improvised Barrier for Mouth-to-Mouth Rescue Breathing A glove can be modified and used as a barrier shield for performing rescue breathing. Cut the middle finger of the glove at its halfway point and insert it into the victim’s mouth. Stretch the glove across the victim’s mouth and nose and blow into the glove as you would to inflate a balloon. After each breath, remove the part of the glove covering the nose to allow the victim to exhale. The slit creates a one-way valve, preventing backflow of the victim’s saliva (see Figure 21-6).

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Figure 21-1. Safety pins on tongue to open airway.

Box 21-1. Improvised Cricothyrotomy Tubes 1. IV administration set drip chamber: Cut the plastic drip chamber of a macro drip (15 drops/mL) IV administration set at its halfway point with a knife or scissors. Remove the end protector from the piercing spike and insert the spike through the cricothyroid membrane. The plastic drip chamber is nearly the same size as a 15-mm endotracheal tube adapter and fits snugly in the valve fitting of a bag-valve device (Fig. 21-2). 2. Syringe barrel: Cut the barrel of a 1- or 3-mL syringe with the plunger removed at a 45-degree angle at its midpoint to create an improvised cricothyroid airway device. The proximal phalange of the syringe barrel helps secure the device to the neck and prevents it from being aspirated (Fig. 21-3). 3. Any small hollow object: Examples include a small flashlight or penlight casing, pen casing, small pill bottle, and large-bore needle or IV catheter. Several commercial devices are small and lightweight enough to be included in the first-aid kit.

of the gauze remain outside the nasal cavity (Fig. 21-7). This prevents the victim from inadvertently aspirating the nasal packing.42 Complete packing of the nasal cavity of an adult victim requires a minimum of 1 m (3 feet) of packing to fill the nasal cavity and tamponade the bleeding site.7 Expandable packing material, such as Weimert Epistaxis Packing, Rapid Rhino (ArthroCare Corporation, Sunnyvale, CA), or the Rhino Rocket (Shippert Medical Technologies, Centennial, CO), is available commercially. A tampon or balloon tip from a Foley catheter can also be used as improvised packing.42 Anterior nasal packing blocks sinus drainage and predisposes to sinusitis. Prophylactic antibiotics are usually recommended until the pack is removed in 48 hours.42 If the bleeding site is located posteriorly, use a 14- to 16-Fr Foley catheter with a 30-mL balloon to tamponade the site.14 Prelubricate the catheter with either petroleum jelly (Vaseline) or a water-based lubricant, then insert it through the nasal cavity into the posterior pharynx. Inflate the balloon with 10 to 15 mL of water and gently withdraw it back into the posterior nasopharynx until resistance is met. Secure the catheter firmly to the victim’s forehead with several strips of tape. Pack the anterior nose in front of the catheter balloon as described earlier.

Esophageal Foreign Bodies


EAR, NOSE, AND THROAT EMERGENCIES

Epistaxis Epistaxis is a common problem in travelers. Reduced humidity in airplanes, cold climates, and high-altitude environments can produce drying and erosion of the nasal mucosa. Other etiologic factors include facial trauma, infections, and inflammatory rhinitis. Although most cases of epistaxis are minor, some present life-threatening emergencies (see Chapter 26).42 Anterior epistaxis from one side of the nasal cavity occurs in 90% of cases.11 If pinching the nostrils against the septum for a full 10 minutes does not control the bleeding, nasal packing may be needed. Soak a piece of cotton or gauze with a vasoconstrictor, such as oxymetazoline (Afrin) nasal spray, and insert it into the nose, leaving it in place for 5 to 10 minutes. Petroleum jelly–impregnated gauze or strips of a nonadherent dressing can then be packed into the nose so that both ends

Esophageal foreign bodies may cause significant morbidity. Respiratory compromise caused by tracheal compression or by aspiration of secretions can occur. Mediastinitis, pleural effusion, pneumothorax, and abscess may be seen with perforations of the esophagus from sharp objects or pressure necrosis caused by large objects.28 The use of a Foley balloon-tipped catheter can be a safe method for removing blunt esophageal foreign bodies.5,6,17 Success rates of 98% have been cited.5 Associated complications include laryngospasm, epistaxis, pain, esophageal perforation, and tracheal aspiration of the dislodged foreign body.28 Sharp, ragged foreign bodies or an uncooperative victim precludes use of this technique (Fig. 21-8).37 Lubricate a 12- to 16-Fr Foley catheter and place it orally into the esophagus while the victim is seated. After placing the victim in Trendelenburg’s position, pass the catheter beyond the foreign body and inflate the balloon with water. Withdraw the catheter with steady traction until the foreign body can be removed from the hypopharynx or is expelled by coughing.

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C Figure 21-2. Improvised cricothyrotomy tube. A, Cut plastic drip chamber at halfway point. B, Insert spike from drip chamber into the cricothyroid membrane. C, Bag-valve device will fit over the chamber for ventilation.

Adam’s apple

Cricothyroid membrane

Figure 21-3. Improvised cricothyroid airway device can be created by cutting barrel of syringe at a 45-degree angle at its midway point.

Figure 21-4. Cricothyroid membrane is found in the depression between the Adam’s apple (thyroid cartilage) and the cricoid cartilage.

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Adam’s apple (thyroid cartilage)

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B Figure 21-5. Cricothyrotomy.A, Locate cricothyroid membrane and make a vertical 1-inch incision through the skin. B, Insert pointed end of improvised cricothyrotomy tube through the membrane.

Take care to avoid lodging the foreign body in the nasopharynx. Any significant impedance to withdrawal should terminate the attempt.37 Use of this technique is recommended only in extreme wilderness settings or when endoscopy is not available.


TENSION PNEUMOTHORAX Overview Signs and symptoms of a tension pneumothorax include distended neck veins, tracheal deviation away from the side of the pneumothorax, unilateral absent breath sounds, hyperresonant hemithorax to percussion, subcutaneous emphysema, respiratory distress, cyanosis, and cardiovascular collapse. Tension pneumothorax mandates rapid pleural decompression if the victim appears to be dying. Possible complications of pleural decompression include infection; profound bleeding from puncture of the heart, lung, or a major blood vessel; or even laceration of the liver or spleen.

Figure 21-6. Improvised cardiopulmonary resuscitation (CPR) barrier is created using a latex or nitrile glove. Make a slit in the middle finger of the glove.

Improvised Pleural Decompression Technique Swab the entire chest with povidone-iodine or another antiseptic. If sterile gloves are available, put them on after washing your hands. If local anesthesia is available, infiltrate the puncture site down to the rib and over its upper border. Insert a large-bore intravenous (IV) catheter, needle, or any pointed, sharp object that is available into the chest just above

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Figure 21-7. Anterior epistaxis from one side of the nasal cavity can be treated using nasal packing soaked in a vasoconstrictor. Petroleum jelly–impregnated gauze or strips of nonadherent dressing can be packed in the nose so that both ends of the gauze remain outside the nasal cavity.

Box 21-2. Improvised Pleural Decompression Devices 1. Large-bore (12- or 14-gauge) IV catheter or needle 2. Endotracheal tube 3. Foley catheter with a rigid support (“stylet”), such as a clothes hanger, placed into the lumen 4. Section of a tent pole 5. Hose from a hydration pouch

the third rib in the midclavicular line (midway between the top of the shoulder and the nipple in a line with the nipple approximates this location) (Box 21-2). If you hit the rib, move the needle or knife upward slightly until it passes over the top of the rib, thus avoiding the intercostal blood vessels that course along the lower edge of every rib. The chest wall is 11/2 to 21/2 inches (4–6 cm) thick, depending on the individual’s muscularity and amount of fat present. A gush of air signals that you have entered the pleural space; do not push in the penetrating object further. Releasing the tension converts the tension pneumothorax into an open pneumothorax. Leave the needle or catheter in place, and use a rubber glove to make a flutter valve. Cut out a finger portion from a rubber glove, making a tiny slit cut at the tip. Place this over the external opening to create a unidirectional flutter valve that allows continuous egress of air from the pleural space (Fig. 21-9). To create a one-way flutter valve, cut a finger portion of a latex glove off at the proximal end of the finger and insert the needle

Figure 21-8. Packing the back of the nose.Insert a Foley catheter into the nose and gently pass it back until it enters the back of the throat.After the tip of the catheter is in the victim’s throat, carefully inflate the balloon with 10 to 12 mL of air or water from a syringe. Inflation should be done slowly and should be stopped if painful. After the balloon is inflated, gently pull the catheter back out until resistance is met.

or catheter into the open end of the glove finger and through the tip as shown (see Figure 21-9A). The cut-out finger portion of the glove creates a unidirectional flutter valve that allows egress of air from the pleural space during expiration, but collapses to prevent air entry on inspiration (see Figure 21-9B, C).

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with both a rigid or semirigid cervical collar and long-board immobilization. Historically, dogma about cervical spine injuries has specified a “splint ’em as they lie” approach. Transporting a victim who is not in anatomic position is arduous in the backcountry. It is uncomfortable for the victim, difficult for the rescuers, and increases the risk of further injury. In general, gentle axial traction back to anatomic position is indicated unless (1) return to anatomic position significantly increases pain or focal neurologic deficit or (2) movement of the head and neck results in any noticeable mechanical resistance.24 All cervical spine injuries (or suspected injuries) warrant full long-board immobilization. Movement of the pelvis and hips laterally is potentially more dangerous than anterior–posterior movement; therefore it is appropriate during extended transport to allow gentle flexion at the hip with immobilization in that position if the victim is more comfortable. Soft pads behind the knees and small of the back also add to the victim’s comfort during a long transport.9

Improvised Cervical Collars

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Figure 21-9. A, Finger of glove is attached to needle or catheter to create flutter valve. B, Flutter valve allows air to escape. C, Flutter valve collapses to prevent air entry.


OPEN (“SUCKING”) CHEST WOUND

Penetrating trauma to the chest can produce a chest wound that allows air to be sucked into the pleura on inspiration. Place a piece of plastic food wrap, aluminum foil, or one side of a plastic sandwich bag on top of the wound and tape it on three sides. The untaped fourth side serves as a relief valve to prevent formation of a tension pneumothorax.


SPLINTING AND TRACTION*

Cervical collars are always adjuncts to full spinal immobilization; they should never be used alone. The improvised cervical collar is used in conjunction with manual cervical spine stabilization followed by complete immobilization of the victim on a spine board. A properly applied and fitted collar is a primary defense against axial loading of the cervical spine, particularly in an evacuation that involves tilting the victim’s body uphill or downhill. Improvised cervical collars have had a bad reputation, and textbooks continue to depict them made from a simple cravat wrapped around the neck. This type of system is no more effective than are the soft cervical collars often used by urban plaintiffs trying to impress a jury (i.e., not effective at all). An improvised cervical collar works effectively only if it has the following features: 1. It is rigid or semirigid. 2. It fits properly (many improvised designs are too small). 3. It does not choke the victim. 4. It allows the victim’s mouth to open if vomiting occurs. Improvisational approaches to cervical collars are outlined below.

Closed-Cell Foam System. The best closed-cell foam systems incorporate a full-size or three-quarter-length pad folded longitudinally into thirds and applied centered over the back of the victim’s neck and wrapped forward. The pad is crossed under the chin, contoured underneath opposite axillae, and secured. If the pad is not long enough, you can tape or tie on extensions. This system also works well with blankets, beach towels, or even a rolled plastic tarp. Avoid small flexible cervical collars that do not optimally extend the chin-to-chest distance.

Because of its mobility, the cervical spine is the spinal column area most commonly injured in trauma. Any obvious or suspected cervical spine injury demands full spinal immobilization

Padded Hip Belt. A padded hip belt or fanny pack removed from a large internal or external frame backpack can sometimes be modified to work perfectly. Wider is usually better. Take up excess circumference by overlapping the belt, and secure the excess material with duct tape (Fig. 21-10).

*Specific aspects of fracture care are covered in detail in other chapters. This chapter focuses on improvised systems, not on definitive orthopedic management. Improvised systems rarely provide the same degree of protection as commercial systems. Good judgment is needed.

Clothing. Bulky clothing, such as a fiber pile or fleece jacket, can be rolled and then wrapped around the victim’s neck to make a cervical collar. The extended sleeves can be used to secure the collar. Prewrapping a wide elasticized (Ace) wrap

Cervical Spine Injuries

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Hip belt of inverted backpack

Cervical stabilizer Fanny pack as cervical collar

Figure 21-10. Inverted pack used as spine board.

around the jacket compresses the material to make it more rigid and supportive.

Malleable Aluminum Splint. A well-padded, aluminum splint (e.g., SAM Splint) can be adjusted to fit almost any size neck (Fig. 21-11).

Improvised Spinal Immobilization As noted, the improvised cervical collar is only an adjunct to full spinal immobilization. Two immobilization systems are (1) short-board immobilization, which is useful for short-duration transport (that is, getting the victim out of immediate danger) or when used in conjunction with a long board; and (2) longboard immobilization, used for definitive immobilization during extensive transport. Use either of these systems in conjunction with a rigid or semirigid cervical collar, as described previously. Improvised lateral “towel rolls” are often added to these systems for additional head and neck support. These rolls can be improvised from small sections of closed-cell foam (e.g., Ensolite [Armacell LLC, Mebane, NC]) sleeping pads. Alternatively, a U-shaped head support, or “horse collar,” can be made from any rolled garment, blanket, tarp, or tent fly; this is placed over the victim’s head in an inverted U and used with the improvised cervical collar and spine board. Hiking socks or stuff bags filled with dirt, sand, or gravel also work well for this purpose. Stuff bags filled with snow for support should never be used because the snow can melt during transport, which will cause excessive head and neck motion. However, snow-filled stuff bags can act as temporary support while more definitive systems are being constructed.

Improvised Short-Board Immobilization Internal Frame Pack and Snow Shovel System. Some internal frame backpacks can be easily modified by inserting a snow shovel through the centerline attachment points (the shovel handgrip may need to be removed first). The victim’s head is taped to the lightly padded shovel (Fig. 21-12); in this context, the shovel blade serves as a head bed. This system incorporates

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the remainder of the pack suspension as designed (i.e., shoulder and sternum straps with hip belt) and works well with other long-board designs, such as the continuous loop system (see Continuous Loop System section). Always assess the amount of flexion or extension the system will create on the cervical spine; if it is unacceptable, the system must be modified appropriately.

Inverted Pack System. An efficient short board can be made using an inverted internal or external frame backpack. The padded hip belt provides a head bed, and the frame is used as a short board in conjunction with a rigid or semirigid cervical collar (Fig. 21-13). Turn the pack upside down, and lash the victim’s shoulders and torso to the pack. Fasten the waist belt around the victim’s head, as in the top section of a Kendrick extrication device. The hip belt is typically too large, but excess circumference can be eliminated with bilateral Ensolite rolls. Unlike the snow shovel system, this system requires that the victim be lashed to the splint. Snowshoe System. A snowshoe can be made into a fairly reliable short spine board (Fig. 21-14). Pad the snowshoe and rig it for attachment to the victim as shown.19

Improvised Long-Board Immobilization Continuous Loop System (also known as the daisy chain, cocoon wrap, or mummy litter). In the authors’ opinion, this is the only improvised system that is adequate for immobilizing and transporting a patient with potential spine injuries. To construct the continuous loop system, the following items are needed: 1. Long climbing or rescue rope 2. Large tarp (or tent fly) 3. Sleeping pads (Ensolite or Therm-a-Rest [Cascade Designs, Inc., Seattle]) 4. Stiffeners (such as skis, poles, snowshoes, canoe paddles, or tree branches) Lay the rope out with even U-shaped loops as shown in Figure 21-15A. The midsection should be slightly wider to conform to the victim’s width. Tie a small loop at the foot end of the rope and place a tarp on the rope loops. On top of the tarp, lay foam pads the full length of the system (the pads can be overlapped to add length). Then, lay stiffeners on top of the pads in the same axis as the victim (see Fig. 21-15B). Add multiple foam pads on top of the stiffeners, followed optionally with a sleeping bag (see Fig. 21-15C). Place the victim on the pads. To form the daisy chain, bring a single loop through the pre-tied loop, pulling loops toward the center, and feeding through the loops brought up from the opposite side. It is important to take up rope slack continuously. When the victim’s armpits are reached, bring a loop over each shoulder and tie it off (or clip it off with a carabiner) (see Fig. 21-15D). One excellent modification involves adding an inverted internal frame backpack. This can be incorporated with the padding and secured with the head end of the rope. The pack adds rigidity and padding, and the padded hip belt serves as a very efficient head and neck immobilizer (see Figures 21-10 and 21-13). If the victim vomits during transport, the entire unit can be turned on its side or even partially inverted. Backpack Frame Litters. Functional litters can be constructed from external frame backpacks. Traditionally, two frames are

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B D Figure 21-11. Padded aluminum splint cervical collar. A, Place a vertical bend in the malleable aluminum splint approximately 6 inches from one end to form a vertical pillar.Then, add bilateral flares to make the splint comfortable for the victim where it rides against the lower mandible. B, Place the anterior pillar securely beneath the victim’s chin and wrap the remaining length of the splint around the victim’s neck. C, Side view of cervical collar fashioned from a SAM Splint. Note the formation of lateral, and if possible, posterior pillars. D, Frontal view.The end is angled inferiorly to provide an adequate chin-to-chest distance. Note the formation of the anterior pillar.

used, but three or four frames (Fig. 21-16) make for a larger, more stable litter. Cable ties or fiberglass strapping tape simplifies this fabrication. These litters can be reinforced with ice axes or ski poles.

Kayak System. Properly modified, the kayak makes an ideal rigid long-board improvised litter. First, remove the seat along with sections of the upper deck if necessary. A serrated river knife (or camp saw) makes this improvisation much easier. Open deck canoes can be used almost as is once the flotation material has been removed. Canoe System. Many rivers have railroad tracks that run parallel to the river canyon. The tracks can be used to slide a canoe

by placing the boat perpendicular to the tracks and pulling on both bow and stern lines.

Improvised Head Bed. A padded aluminum splint can be formed as shown to create a head bed to assist in securing the immobilized head of an injured victim. Tape this head bed to a commercial or improvised backboard (Fig. 21-17).

Pelvic Fractures Overview Unstable pelvic fractures are associated with a high incidence of morbidity and mortality.10,16,25 In one study, pelvic ring disruption in the trauma patient was associated with a mortality

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Figure 21-12. Head immobilized on a padded shovel.

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Figure 21-13. Short board using an inverted pack system.The backpack waist belt can be seen encircling the head.

Figure 21-14. Improvised snowshoe short board.A well-padded snowshoe is prerigged with webbing and attached to the victim as shown.This system can also be used in conjunction with longboard systems, such as the continuous loop system.

rate of 25%.1 Acute and uncontrolled hemorrhage and its complications are the leading causes of death in these patients.22 Hemorrhage after pelvic injury results from fracture surfaces, venous plexuses, and major arteries, usually branches of the internal iliac artery. Pelvic reduction and stabilization in the

early post-traumatic phase are reported to provide the most effective means of controlling venous hemorrhage.9 Pelvic reduction realigns bleeding fracture surfaces and reduces pelvic volume, and pelvic stabilization facilitates clot formation by reducing fracture site motion.23

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D Figure 21-15. Continuous loop, or “mummy,”litter made with a climbing rope.A, Rope is laid out with even U-shaped loops. B, Stiffeners such as skis and poles are placed underneath the victim to add structural rigidity. It is important to pad between the stiffeners and the victim. C, A sleeping bag may be used in addition to the foam pads. D, Loop of rope is brought over each shoulder and tied off (see text).

Circumferential wrapping and compression of the pelvic region with a sheet or strap has been studied as a means to stabilize and reduce open-book pelvic fractures.8,10 In a pair of studies from Oregon, circumferential pelvic compression was evaluated with the use of cadaveric models. Circumferential compression was found to result in significant stabilization of open-book pelvic injuries. Optimal placement of compression was at the level of the greater trochanters and the symphysis pubis, while the desired tension was found to be around 180 N (40 lb).8,10 Vermeulen and colleagues reported application of pelvic straps to 19 patients in Switzerland.40 Each strap was applied at the accident scene by emergency medical technicians (EMTs) upon suspicion of an unstable pelvic fracture. It took only 30

seconds to apply each strap. Application was subsequently found to produce significant reduction in both symphysis diastasis and pelvic inlet area. Routt and coworkers used a large circumferential sheet pulled tightly around the pelvis.33 The sheet remained in place until further stabilization could be achieved with an external fixator. Application of the sheet achieved reduction and stabilization in a safe and time-effective manner and did not interfere with resuscitation efforts. The American College of Surgeons Advanced Trauma Life Support (ATLS) course now includes a protocol for emergent management of pelvic ring disruptions, advising circumferential application of a pelvic sheet. Circumferential compression with a noninvasive pelvic sling should be considered for any patient with a suspected pelvic

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Figure 21-16. Backpack frame litter.

Figure 21-17. Improvised head bed.

Figure 21-18. Pelvic sling improvised with jacket.

fracture in the wilderness. The SAM Sling (SAM Medical Products, Newport, OR), is a commercial device that provides 150 N (33 lb) of pressure to the pelvis when applied according to the manufacturer’s instructions. It is equipped with an “autostop” buckle, which comprises spring-loaded prongs that lock the buckle in place when the correct amount of force is applied. Clothes, sheets, a sleeping bag, pads, air mattress, tent, or tent fly can be used to improvise a very effective pelvic sling in the backcountry. The object should be wide enough so that it does not cut into the victim when tightened.

2. Very gently slide the improvised sling under the victim’s buttocks and center it under the bony prominences at the outer part of the upper thigh or hips (greater trochanters/symphysis pubis) (Fig. 21-18). Cross the object over the front of the pelvis and tighten the sling by pulling both ends and securing with a knot, clamp, or duct tape. Another tightening technique is to wrap the sling snugly around the pelvis and tie an overhand knot. Place tent poles, a stick, or similar object on the knot and tie another overhand knot. Twist the poles or stick until the sling becomes tight. The sling should be tightened so that it is snug and the pelvis is returned to its normal anatomic position. 3. If a Therm-a-Rest pad or other inflatable sleeping pad is available, fold it in half so that it approximates the size of the pelvis. Gently slide the pad under the victim’s buttocks and center it under the greater trochanters and symphysis pubis. Secure the pad with duct tape, and then inflate the

Applying an Improvised Pelvic Sling 1. Ensure that objects have been removed from the patient’s pockets and that any belt has been removed so that the pressure of the sheet or object doesn’t cause additional pain by pressing items against the pelvis.

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PART FOUR: INJURIES AND MEDICAL INTERVENTIONS nical rescue, or helicopter evacuation is impossible. For example, a full-length ski splint is not compatible with evacuation in a small helicopter.

Femoral Traction Systems Every femoral traction system has six components: 1. Ankle hitch 2. Rigid support that is longer than the leg 3. Traction mechanism 4. Proximal anchor 5. Method for securing the splint to the leg 6. Additional padding

Ankle Hitch. Various techniques are used to anchor the distal extremity to the splint. Many work well, but some are impossible to recall in an emergency. Choose an easy-to-remember technique and practice it. It is best to leave the shoe on the victim’s foot and apply the hitch over it. Cut out the toe section of the shoe to periodically check circulation. Figure 21-19. Pelvic sling improvised with inflatable sleeping pad and duct tape.

pad as you would normally until it produces a snug fit and the pelvis is reduced (Fig. 21-19). 4. Place padding between the legs and gently tie the legs together to further stabilize the fracture in a position that is most comfortable for the victim.

Traction In the backcountry environment, traction is essential for two fundamental reasons: (1) the general inability to provide IV volume expansion and (2) prolonged transport time to definitive care. The primary purpose of backcountry femoral traction is to limit blood loss into the thigh. For a constant surface area, the volume of a sphere is greater than the volume of a cylinder. Pulling (via traction) the thigh compartment back into its natural cylindrical shape limits blood loss into the soft tissue. Although the main objective is to control hemorrhage and prevent shock, enhanced comfort for the victim and decreased potential for neurovascular damage are important secondary benefits. Properly applied improvised femoral traction can save lives in the backcountry, particularly on extended transports where IV fluids are not available.6

General Principles of Traction The potential variety of traction designs is unlimited, but five key design principles should be considered when evaluating any femoral traction system: 1. Does the splint provide inline traction or does it incorrectly pull the leg off to the side or needlessly plantar flex the ankle? 2. Is the splint comfortable? Be sure to ask the victim. 3. Does the splint compromise neurologic or vascular function? Constantly check distal neurovascular function. 4. Is the splint durable, or will it break when subjected to backcountry stresses? As stated earlier, it might help to try the traction design on an uninjured person and then knock the device around a bit to determine its strength. 5. Is the splint cumbersome? Many reasonable splint designs become so bulky and awkward that litter transport, tech-

Single Runner System. Loop a long piece of webbing, shoelace, belt, or rope over itself, bringing one end through the middle to create a stirrup. After rotating it away from the person by 180 degrees, slip the hitch over the shoe and ankle. Double Runner System. In this very straightforward technique, lay two short webbing loops (“runners”) over and under the ankle as shown (Fig. 21-20A). Pass the long loop sides through the short loop on both sides (see Fig. 21-20B) and adjust as needed (see Fig. 21-20C). One advantage of this system is that it is infinitely adjustable, enabling the rescuer to center the pull from any direction. As always, proper padding is essential, especially for long transports. The victim’s boot can distribute pressure over the foot and ankle but will obscure visualization and palpation of the foot. A reasonable compromise is to leave the boot on and cut out the toe section for observation. S-Configuration Hitch. This type of hitch is preferred if the victim also has a foot or ankle injury because traction is pulled from the victim’s calf instead of the ankle. Lay a long piece of webbing or similar material over the upper part of the ankle (lower calf) in an S-shaped configuration. Wrap both ends of the webbing behind the ankle and up through the loop on the other side. Pull the ends down on either side of the arch of the foot to tighten the hitch and tie an overhand knot (Fig. 21-21). Victim’s Boot System. Another efficient system uses the victim’s own boot as the hitch. Cut two holes into the side walls of the boot just above the midsole and in line with the ankle joint. Thread a piece of nylon webbing or cravat through to complete the ankle hitch (Fig. 21-22). Cutting away the toe may be necessary for neurovascular assessment. Buck’s Traction. For extended transport, Buck’s traction can be improvised using a closed-cell foam pad (Fig. 21-23). Wrap the pad around the lower leg as shown and loop a stirrup below the foot from medial calf to lateral calf. Fasten this assembly with a second cravat wrapped circumferentially around the calf over the closed-cell foam (duct tape or nylon webbing can be used instead of cravats). This system greatly increases the surface area over which the stirrup is applied and decreases the

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Figure 21-20. Double runner ankle hitch. A and B, Two webbing loops (runners) are laid over and under the ankle. C, Completed double runner ankle hitch. The beauty of this system is its infinite adjustability. The traction can be easily centered from any angle, ensuring in-line traction.

C

potential for neurovascular complications and dermal ischemia. In addition, improvised Buck’s traction has been used to manage backcountry hip fractures. However, it has been suggested that this technique may have little benefit.1 If Buck’s traction is used for a hip injury, use smaller amounts of traction (roughly ≤5 lb [2.5 kg]).

Rigid Support. The rigid support can be fabricated as a unilateral support (similar to the Sager traction splint or Kendrick traction device) or as a bilateral support, such as the Thomas half ring or Hare traction splint. Unilateral supports tend to be easier to apply than bilateral supports. The following are some ideas for rigid support. Double Ski Pole or Canoe Paddle System. This is fashioned like a Thomas half ring, with the interlocked pole straps slipped under the proximal thigh to form the ischial support. Some

mountain guides carry a prefabricated drilled ski pole section or aluminum bar that can be used to stabilize the distal end of this system (Fig. 21-24).

Single Ski Pole or Canoe-Kayak Paddle. Use a single ski pole or paddle either between the legs, which is ideal for bilateral femur fractures, or lateral to the injured leg. The ultimate rigid support is an adjustable telescoping ski pole used laterally. Adjust the pole to the appropriate length for each victim, making the splint compact for litter work or helicopter evacuation (Fig. 21-25). Tent Poles. This system uses conventional sectioned tent poles. Fit the poles together to create the ideal length rigid support. Because of their flexibility, tent poles must be well secured to the leg to prevent them from flexing out of position. Place a blanket pin or bent tent stake (Fig. 21-26) in the end of the pole

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Figure 21-21. S-configuration hitch for traction splinting.The system should be configured distally over the boot to distribute the forces.

Figure 21-23. Buck’s traction.Duct tape stirrups are added to a small foam pad that is wrapped around the leg. The entire unit is wrapped with an Ace bandage. This system helps distribute the force of the traction over a large surface area.

Figure 21-22. Traction using cut boot and cravat.

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Figure 21-24. A, Double ski pole system with prefabricated cross-bar and webbing belt traction. A prefabricated drilled ski section is used to attach the ends of two ski poles. Traction is applied with a webbing belt and sliding buckle.B, A Fastex-type or cam-lock utility strap makes a very efficient traction device and can be adapted for most systems.

B

A

Figure 21-25. Single ski pole system. An adjustable telescoping ski pole is used as the rigid support. A stirrup is attached to a carabiner placed over the end of the pole.Traction is applied by elongating the ski pole while another rescuer provides manual traction on the victim’s leg. Additional padding and securing follow (not shown).

Figure 21-26. Prefabricated drilled tent pole section and bent tent stake.The ski pole section is used to stabilize the end of a double ski pole traction system.This can be improvised on site if necessary. The bent tent stake serves as a distal traction anchor if a tent pole is used as the rigid support.

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1

2

3

Figure 21-27. A Prusik knot made from a small-diameter cord is used as an adjustable distal traction anchor. Although two wraps are shown in the illustration, an additional wrap adds further security when applied to a smooth surface, such as a kayak paddle.

Figure 21-29. Tent pole traction with trucker’s hitch. A bent tent stake is placed into the end of the tent pole as the distal traction anchor.A simple trucker’s hitch is used to provide traction.

windlass. Although these systems work and look good in the movies, they can be awkward to apply and are often not durable. The windlass can unspin if it is inadvertently jarred and can apply rotational forces to the leg. The amount of traction required may be difficult to estimate. A general rule is to use 10% of body weight or about 10 to 15 lb (4.5–7 kg) for the average victim. Consider practicing with a commercial system, such as a Sager Traction Device (Minto Research & Development, Inc., Redding, CA), ahead of time to get a feeling for what these forces look and feel like. Check the opposite extremity to compare length. After the traction is applied, always recheck distal neurovascular function (circulation, sensation, and movement). Figure 21-28. Two Prusik wraps are shown.Three or four wraps provide additional friction and security. If the Prusik knot slips, it can be easily taped in place.

to provide an anchor for the traction system. Alternately, use a Prusik knot (Fig. 21-27) to secure the system to the end of the tent pole (Fig. 21-28).

Cam Lock or Fastex-Like Slider. This simple, effective system uses straps that have a Fastex-like slider (ITW Fastex, Des Plaines, IL). Such straps are often used as waist belts or to hold items to packs. Alternately, a cam lock with nylon webbing can be used. Attach the belt to the distal portion of the rigid support and then to the ankle hitch. Traction is easily applied by cinching the nylon webbing (see Figure 21-24). Trucker’s Hitch. A windlass can be easily fashioned using smalldiameter line (parachute cord) and a standard trucker’s hitch for additional mechanical advantage (Fig. 21-29).

Miscellaneous. Any suitable object, such as a canoe or kayak paddle (see Figure 21-28), two ice axes taped together at the handles, or a straight branch, can be used to make a rigid support. Although skis immediately come to mind as suitable rigid components, they are too cumbersome to work effectively. Because of their length, skis may extend far beyond the victim’s feet or require placement into the axillae, which is unnecessary and inhibits mobility (e.g., sitting up during transport). Premanufactured canvas pockets, available from the National Ski Patrol System, provide a ski tip and tail attachment grommet for use with the ski system.

Prusik Knot. Almost any system can be rigged with a Prusik knot (see Figure 21-27). Prusiks are ideal for providing traction from rigid supports with few tie-on points (such as a canoe paddle shaft or a tent pole). The Prusik knot can be used to apply the traction (by sliding the knot distally) or simply as an attachment point for one of the traction mechanisms already mentioned.

Traction Mechanism. The first popularized modern improvised traction mechanism was the Boy Scout–style Spanish

Litter Traction. If no rigid support is available and a rigid litter such as a Stokes is being used, apply traction from the rigid bar

Chapter 21: Improvisation in the Wilderness at the foot end of the litter. If this system is used, ensure that the victim is immobilized on the litter with adequate countertraction, such as inguinal straps.

Proximal Anchor. The simplest proximal anchor uses a single proximal thigh strap, which can be made from a piece of climbing webbing or a prefabricated strap, belt, or cam lock (Figs. 21-30 and 21-31). A cloth cravat can be used in a pinch. On the river, a life jacket can be used (Fig. 21-32). When climbing, a climbing harness is ideal. Securing and Padding. Check all potential pressure points to ensure that they are adequately padded. An excellent padding system can be made by first covering the upper and lower leg with a folded length of Ensolite (Fig. 21-33). This is preferred over a circumferential wrap because the folded system allows you to see the extremity. The victim is more comfortable if femoral traction is applied with the knee in slight flexion (padding placed beneath the knee during transport). Secure the splint firmly to the leg. Almost any straplike object will work, but a 4- to 6-inch (10–15 cm) Ace bandage wrapped circumferentially provides a comfortable and secure union. Finally, strap or tie the ankles or feet together (with adequate padding between the legs) to give the system additional stability. Tying the ankles together also prevents the injured leg from excessive external rotation during transport, which might otherwise greatly add to the victim’s discomfort.

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incorporates the joints above and below the fracture. If possible, the splint should be fashioned on the uninjured extremity and then transferred to the injured one. On ski trips, skis and poles can be used as improvised splints. On white-water trips, canoe and kayak paddles can be used in a similar manner. Airbags used as flotation for kayaks and canoes can be converted into pneumatic splints for arm and ankle injuries. The minicell or Ethafoam (Dow, Midland, MI) pillars found in most kayaks can be removed and carved into pieces to provide upper and lower extremity splints. A life jacket can be molded into a cylinder splint for knee immobilization or into a pillow splint for the ankle. The flexible aluminum stays found in internal frame packs can be molded into upper extremity splints. Other improvised

Extremity Splints Splint all fractures before the victim is moved unless his or her life is in immediate danger. In general, make sure the splint

A

Figure 21-30. Proximal anchor using cam lock belt.The belt is applied as shown.The strap is adjusted loosely to allow the belt to ride up to the point of the hip. If the strap is improperly tightened, it can create pressure over the fracture, and it moves the traction point to a less optimal distal position. Padding is helpful, but not always necessary if the victim is wearing pants and the strap is properly adjusted.

B Figure 21-31. A, River dry bag used to create a simple proximal support with a kayak paddle. B, Here a paddle is pushed up against the proximal support strap.It is taped for security but the forces are pushing against the strap, not the tape.

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C Figure 21-31, cont’d. C, A similar technique could be used with a ski pole or other suitable object.

A

Figure 21-32. Life jacket proximal anchor. An inverted life jacket worn like a diaper forms a well-padded proximal anchor.A kayak paddle is rigged to the life jacket’s side adjustment strap.

B splinting material includes sticks or tree limbs, rolled-up magazines, books or newspapers, ice axes, tent poles, and dirt-filled garbage bags or fanny packs. Ideally, a splint should immobilize the fractured bone in a functional position. In general, “functional position” means that the legs should be straight or slightly bent at the knee, the ankle and elbow bent at 90 degrees, the wrists straight, and the fingers flexed in a curve as if the person were attempting to hold a can of soda or a baseball. Splints can be secured in place with strips of clothing, belts, pieces of rope or webbing, pack straps, gauze bandages, or elastic bandage wraps. Padded aluminum can be molded into various configurations to splint extremity injuries. Padded aluminum splints (e.g., SAM

Figure 21-33. Folded Ensolite padding often provides better visualization of the extremity than does a circumferential wrap.

Splint) are built from a thin core of aluminum, sandwiched between two layers of closed-cell foam. When molded into any of several “structural curves,” padded aluminum splints become much more rigid and can be used to immobilize most fractured or injured extremities. If prolonged use (more than a few hours) is anticipated, place absorbent material, such as cotton cloth, between the splint and the skin to prevent skin irritation. Also, to prevent uncomfortable pressure points during prolonged use, place soft padding (such as

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A

B Figure 21-34. Tripod splint for unreduced anterior shoulder dislocation. This splint holds the arm in abduction when adduction is not possible. Additional padding should be added where necessary and the splint secured to the arm with an elastic wrap or other bandaging material.

Figure 21-36. Forearm splint. These splints are used for treatment of wrist or forearm fractures. The sugar-tong splint (A) prevents pronation and supination and has the advantage of greater security and protection than the volar splint (B) because of its anterior-posterior construction.

gauze pads) around all bony prominences (Figs. 21-34 to 21-41).

Functional Splints Although most splints are designed to immobilize an injured extremity completely, in the backcountry a splint may need to allow for a limited range of motion so the victim can facilitate his or her own rescue. Many functional splints can be improvised quickly using nothing more than a closed-cell foam sleeping pad and some tape or elastic wrap. With the advent of inflatable sleeping pads (e.g., Therm-a-Rest), foam pads are not as ubiquitous as they once were in the backcountry. However, many of these splints can be made using a partially inflated Therm-a-Rest. Once applied, these pads can be inflated to provide the necessary support, fit, and comfort (Fig. 21-42).

Other Wraps and Bandages Functional Shoulder Immobilizer (Shoulder Spica Wrap)

Figure 21-35. Humerus splint. Used in conjunction with a sling and swath, this splint adds extra support and protection for a fractured humerus.

After a dislocated shoulder is reduced, standard treatment is to completely immobilize the arm with a sling and swath. This, however, prevents the victim from using the extremity to facilitate his or her own evacuation. A more functional system can be made using a 6-inch (15 cm) elastic wrap. This method allows the victim limited function (e.g., ski poling or kayak

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A

Figure 21-37. Lower leg or ankle splint. A sugar-tong splint can be used to immobilize fractures of the tibia, fibula, or ankle. When used on an adult, two splints should be used. A third splint may be placed posteriorly for additional support.

paddling) while still preventing complete abduction of the arm (Fig. 21-43).

Triangular Bandage One of the most ubiquitous components of first-aid kits and one of the easiest to replace through improvisation is the triangular bandage. The need to carry this bulky item, which is commonly used to construct a sling and swath bandage for shoulder and arm immobilization, can be eliminated by carrying two or three safety pins. Pinning the shirt sleeve of the injured arm to the chest portion of the shirt effectively immobilizes the extremity against the body (Fig. 21-44A). If the victim is wearing a short-sleeved shirt, the bottom of the shirt can be folded up and over the arm to create a pouch. This can be pinned to the sleeve and chest section of the shirt to secure the arm (see Fig. 21-44B).

B Figure 21-38. A and B, Padded aluminum thumb spica.

Triangular bandages are also used for securing splints and constructing pressure wraps. Common items, such as socks, shirts, belts, pack straps, webbing, shoe laces, fanny packs, and underwear, can easily be substituted.


WOUND MANAGEMENT The same principles that govern wound management in the emergency department apply in the wilderness. The main problem faced in the wilderness is access to adequate supplies. In deciding to close a wound primarily or pack it open, take into account the mechanism of injury, age of the wound, site of the wound, degree of contamination, and ability to effectively clean the wound.

A C

B

D

Figure 21-39. Knee immobilizer using two padded aluminum splints.The splints are folded in half, then fanned out (wider at the top for the thigh) and taped.Tape is applied to maintain the fan shape.The splint is then applied bilaterally and secured.

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Cut here

Figure 21-40. Posterior arm splint. This splint is cut from a 5- to 9-gallon (1.3–2.4 L) plastic fuel or water can.When used with appropriate padding,this forms an excellent splint for injured or fractured elbows.

Figure 21-42. Functional knee and lower leg immobilizer. Wrap a sleeping pad around the lower leg from the mid thigh to the foot. Fold the pad so that the top of the leg is not included in the splint.This provides better visualization of the extremity and leaves room for swelling. A full-length pad forms a very bulky splint and may need to be trimmed before rolling. Because of the conical shape of the lower extremity and the effects of gravity, foam-pad lower extremity splints tend to work their way inferiorly when the victim ambulates. A simple solution is to use duct tape “suspenders” to keep the splint from migrating downward.

Wound Irrigation

Figure 21-41. Webbing sling. An 8-foot (2.5 m) length of 1-inch (2.5 cm) tubular or flat webbing is used to form a functional arm sling. A Crazy Creek Chair can be used to improvise both upper and lower extremity splints. Its inherent integral strapping system precludes the need for additional straps or tape.

The primary determinants of infection are bacterial counts and amount of devitalized tissue remaining in the wound.20 Ridding a wound of bacteria and other particulate matter requires more than soaking and gentle washing with a disinfectant.26 Irrigating the wound with a forceful stream is the most effective method of reducing bacterial counts and removing debris and contaminants.29,36 The cleansing capacity of the stream depends on the hydraulic pressure under which the fluid is delivered.19,35 Irrigation is best accomplished by attaching an 18- or 19-gauge catheter to a 35-mL syringe, or a 22-gauge needle to a 12-mL syringe. This creates hydraulic pressure in the range of 7 to 8 lb/in2 and 13 lb/in2 (3 to 3.5 and 6 kg/cm2), respectively.19,31,35 The solution is directed into the wound from a distance of 1 to 2 inches (2.5–5 cm) at an angle perpendicular to the wound surface and as close to the wound as possible. The amount of irrigation fluid varies with the size and contamination of the wound, but should average no less than 250 mL.19 Remember: “the solution to pollution is dilution.” Which irrigation solution is best for open wounds? Those who subscribe to the theory that nothing should enter a wound that could not be instilled safely into the eye believe that normal saline is the best solution.12,21 In a study of 531 patients with traumatic wounds, there was no significant variation in infection rates among sutured wounds irrigated with normal saline, 1% povidone-iodine, or pluronic F68 (Shur-Clens).15

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B

C

D Figure 21-43. A–D, Shoulder spica wrap.

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Box 21-3. Recommended Technique for Wound Irrigation 1. Fill a sandwich or garbage bag with disinfected water. 2. Disinfect the water with iodine tablets, iodine solution, or povidone-iodine or by boiling it. 3. Normal saline can be made by adding 2 teaspoons (9 g) of salt per liter of water. 4. Seal the bag. 5. Puncture the bottom of the bag with an 18-gauge needle, safety pin, fork prong, or knife tip. 6. Squeeze the top of the bag forcefully while holding it just above the wound, directing the stream into the wound. 7. Use caution to ensure that none of the irrigation fluid splashes into your eyes.

A

Box 21-4. Wound Taping Technique

B Figure 21-44. Techniques for pinning the arm to the shirt as an improvised sling. A, With a long-sleeved shirt or jacket, the sleeved arm is simply pinned to the chest portion of the garment.B, With a short-sleeved shirt,the bottom of the shirt is folded up over the injured arm and secured to the sleeve and upper shirt.

Tap water has been found to be as effective for irrigating wounds as sterile saline. In fact, the infection rate was significantly lower after irrigation with tap water, and no infections resulted from the bacteria cultured from the tap water.3 Improvised wound irrigation requires only a container that can be punctured to hold the water, such as a sandwich or garbage bag, and a safety pin or 18-gauge needle (Box 21-3).

Wound Closure Before a wound is closed, remove all foreign material and grossly devitalized tissue. Debridement can be accomplished using scissors, knife, or any other sharp object, and wounds can be closed with sutures, staples, tape, pins, or glue. Although suturing is still the most widely used technique, stapling and gluing are ideal methods for closing wounds in the wilderness.

1. Obtain hemostasis, and dry the wound edges. 2. Apply benzoin or cyanoacrylate glue to the skin adjacent to the wound. Benzoin should be allowed to dry long enough for it to become tacky, but tape should be applied to the glue while the glue is still wet. 3. Tape should be cut to 1/4-inch or 1/2-inch widths (6– 13 mm), depending on the size of the laceration, and to a length that allows for 3/4 to 1 inch (2 to 3 cm) of overlap on each side of the wound. 4. Secure one half of the tape to one side of the wound. Oppose the opposite wound edge with a finger while the tape is secured to the other side. 5. Wound tapes should have gaps of 1/16 to 1/8 inch (2–3 mm) between them to allow for serous drainage. 6. Cross-stays of tape can be placed perpendicular over the tape ends to prevent them from peeling off. 7. Additional glue can be applied to the tape edges every 24 hours to reinforce adhesion.

Clinical studies of the use of staples to close traumatic lacerations have found various advantages of stapling over suturing: wound tensile strength is greater, there is less inflammation, time required for closure is shorter, and fewer instruments are needed.32 Most important, cosmetic outcome is not compromised.18 Staplers are lightweight, presterilized, and easy to use.

Wound Taping Skin Tapes. Skin tapes are useful for shallow, nongaping wounds and have several advantages over suturing, including reduced need for anesthesia, ease of application, decreased incidence of wound infection, and availability. Any strong tape can be used to improvise skin tape strips, but duct tape works especially well (Box 21-4). Puncturing holes in the tape before application helps prevent exudate from building up under the tape. Wipe the skin with a solvent such as acetone to remove oil and sweat. Then, apply benzoin to the skin before the tape to augment adhesion. Wound taping does not work well over joints or on hairy skin surfaces unless the hair is first removed.

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Box 21-5. Technique for Gluing Lacerations

Dental floss

1. Irrigate the wound with copious amounts of disinfected water. 2. Control any bleeding with direct pressure. Place a gauze pad moistened with oxymetazoline (Afrin) nasal spray into the wound to help control bleeding. 3. Once hemostasis is obtained, approximate the wound edges using fingers or forceps. 4. Paint the tissue glue over the apposed wound edges using a very light brushing motion of the applicator tip. Avoid excess pressure of the applicator on the tissue because this could separate the skin edges, forcing glue into the wound. Apply multiple thin layers (at least three), allowing the glue to dry between each application (about 2 minutes). 5. Glue can be removed from unwanted surfaces with acetone, or loosened from skin with petroleum jelly.

Tie floss around crossed hair twists

Figure 21-45. Scalp laceration closed using dental floss.

Hair-Tying a Scalp Laceration. If you are faced with a bleeding scalp laceration and the injured person has a healthy head of hair, you can tie the wound closed using the victim’s own hair and a piece of suture (0-silk works best), dental floss, sewing thread, or thin string. Take the material and lay it on top of and parallel to the wound. Twirl a few strands of hair on each side of the wound and then cross them over the wound in opposite directions so that the force pulls the wound edges together. Have an assistant tie the strands of hair together with the material while you hold the wound closed with the strands of hair. A square knot works best (Fig. 21-45). Repeat this technique as many times as necessary along the length of the wound to close the laceration.

Gluing The concept of gluing wounds is not new; the U.S. Army used a quick-sealing glue to treat battlefield wounds in Vietnam, and Histoacryl (N-butyl-2-cyanoacrylate) tissue adhesive has been used in Europe and Canada for sutureless skin closure for more than a decade.41 The U.S. Food and Drug Administration (FDA) has approved a topical skin adhesive to repair skin lacerations. Dermabond (2-octyl cyanoacrylate) is packaged in a small single-use applicator. Tissue glue is ideal for backcountry use because it precludes the need for topical anesthesia, is easy to use, reduces the risk of needle stick injury, and takes up much less room than a

conventional suture kit. When applied to the skin surface, tissue glue provides strong tissue support and peels off in 4 to 5 days without leaving evidence of its presence.31 It provides a faster and less painful method for closing lacerations than does suturing and has yielded similar cosmetic results in children with facial lacerations (Box 21-5).30 Tissue glue evokes a mild acute inflammatory reaction with no tissue necrosis.39 Dermabond has four times the three-dimensional breaking strength of Histoacryl and forms a more flexible bond, thus providing a stronger and longer bond than its European counterpart. Petroleum-based ointments and salves, including antibiotic ointments, should not be used on the wound after gluing because these substances can weaken the polymerized film and cause wound dehiscence. Tissue glue has also been used successfully to treat superficial painful fissures of the fingertips (“polar hands”), which commonly occur in cold climates and at high elevations.4


IMPROVISED BLISTER MANAGEMENT

To dress blisters without moleskin, molefoam, or other commercial blister dressing, you can improvise one with a piece of duct tape. Duct tape’s smooth outer surface provides protection from friction, while its adhesive side adheres strongly to skin. A sandwich bag can be used to improvise another type of blister dressing. It simulates the Blist-O-Ban, which was developed by SAM Medical Products as an innovative technique (BursaTek technology) to prevent blisters. The smooth, gliding surface of the bag helps to stop friction and reduce development of hot spots and blisters. Cut the corner of the sandwich bag and apply a lubricant between the two surfaces. Secure the piece of bag to the blister site with tape or glue (Fig. 21-46).


RING REMOVAL Rings should always be removed quickly after injury to fingers and trauma to the hands; progressive swelling may cause rings to act as tourniquets. If a ring cannot be removed with soap or lubricating jelly, the string wrap technique can be used. Pass a

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A

B

Figure 21-46. A–C, Blister dressing improvised with plastic sandwich bag.

C

20-inch (51 cm) length of fine string, dental floss, umbilical tape, or thick suture between the ring and the finger. Pull the string so that most of it is on the distal side of the digit. Then wrap it around the swollen finger from proximal to distal, beginning next to the ring and continuing past the proximal interphalangeal joint. Place successive loops of the wrap close enough together to prevent any swollen skin from bulging between the strands. Remove the ring by unwinding the proximal end of the string and forcing the ring over the distal string. If the string is not long enough, the technique may require repeated wraps (Fig. 21-47).


IMPROVISATIONAL TOOLKIT Some people, convinced they could whittle a Swan-Ganz catheter from a tree branch, enter the wilderness with nothing more than a Swiss Army knife. However, a little foresight and preparation make improvisation much easier. Efficiency trans-

lates into speedy preparation and assembly, which ultimately results in better care. The following section lists items that facilitate improvisation in the field.

Knife The knife can be a fairly simple model, but it should have an awl for drilling holes into skis, poles, sticks, and so on. The awl on a Swiss Army knife works quite well for this purpose. This allows one to create well-fitted components during improvisation (e.g., a drilled cross-bar attached to ski tips for an improvised rescue toboggan).

Tape Carry some form of strong, sticky, waterproof tape. This item cannot be improvised. Use either cloth adhesive tape (already in the medical kit) or duct tape. Duct tape is ideal for nearly all tasks, even being useful on skin when needed (e.g., to close wounds, treat blisters, or tape an ankle). Note, however, that some persons may be sensitive to the adhesive. Fiberglass

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Box 21-6. Uses of a Safety Pin Safety pins can be used: • To pin the anterior aspect of the tongue to the lower lip (use two pins) to establish an airway in an unconscious victim whose airway is obstructed (see Figure 21-1) • To replace the lost screw in a pair of eyeglasses to prevent the lens from falling out • To improve glasses: Draw two circles in a piece of duct tape where your eyes would fit. Use a pin to make holes in the circles, then tape this to your face. The pinholes will partially correct myopic vision and protect the eyes from ultraviolet radiation. Slits can also be used for improvised sunglasses. • To perform neurosensory skin testing • To puncture plastic bags for irrigation of wounds • To remove embedded foreign bodies from the skin • To drain an abscess or blister • To relieve a subungual hematoma • As a fishhook • As a finger splint (mallet finger) • As a sewing needle, using dental floss as thread • To hold gaping wounds together • To replace a broken clothing zipper • To hold gloves or mittens to a coat sleeve • To unclog jets in a camping stove • To pin triage notes to multiple victims • To remove a corneal foreign body (with ophthalmic anesthetic) • In a sling and swath for shoulder or arm injuries • To fix a ski binding • To extract the clot from a thrombosed hemorrhoid • To pin a strap or shirt tightly around the chest for rib fracture support • To remove ticks Figure 21-47. String technique for removing a ring from a swollen finger (see text).

strapping tape has greater tensile strength and is ideal for joining rigid components, such as taping two ice axes together. However, it is less sticky than duct tape and not as useful for patching torn items. Extra tape can be carried by wrapping lengths of it around pieces of gear.

Plastic Cable Ties Lightweight cable ties can be used to bind almost anything together (e.g., binding pack frames together for improvised litters or ski poles together for improvised carriers). They are also perfect for repairing many items in the backcountry.

Parachute Cord Parachute cord has hundreds of uses in the backcountry. It can be used for trucker’s hitch traction and for tying complex splints together. Parachute cord is light; carry a good supply.

Safety Pins See Box 21-6 for various uses for safety pins.

Wire Braided picture-hanging wire works well because it is supple and ties like line. Its strength makes it superior for repairing and

improvising components under an extreme load, such as fabricating improvised rescue sleds or repairing broken or detached ski bindings.

Bolts and Wing Nuts Bolts and wing nuts make the job of constructing an improvised rescue sled much easier (see Improvised Rescue Sled or Toboggan section). Bolts are useful only if holes can be created to put them through. Therefore, a knife with an awl is needed for drilling holes through skis, poles, or other improvised items.

Prefabricated Cross-Bar The prefabricated cross-bar can be used for double ski pole traction splint systems. A cross-bar is easily fabricated from a branch or short section of a ski pole, but carrying a prefabricated device, such as a 6-inch (15 cm) predrilled ski pole section, saves time (see Figure 21-24).

Ensolite (Closed-Cell Foam) Pads Since the introduction of Therm-a-Rest types of inflatable pads, closed-cell foam has become increasingly scarce; however, closed-cell foam (Ensolite) is still the ultimate padding for almost any improvised splint or rescue device. The uses for

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closed-cell foam are virtually unlimited. Even die-hard Therma-Rest fans should carry a small amount of closed-cell foam, which is lightweight and doubles as a comfortable seat cushion. Furthermore, unlike inflatable pads, Ensolite will not puncture and deflate. Therm-a-Rest pads also have their place, being useful for padding for long bone splints and immobilizers (e.g., an improvised universal knee immobilizer). An inflatable pad can also be used to cushion pelvic fractures. First, wrap the deflated pad around the pelvis. Then secure the pad with tape and inflate it, creating an improvised substitute for military antishock trousers (MAST device).

Fluorescent Surveyor’s Tape Surveyor’s tape can be used much like Hansel and Gretel’s breadcrumbs to help relocate a route into or out of a rescue scene. It is also ideal for marking shelters in deep snow and can serve as a wind sock during helicopter operations on improvised landing zones. Surveyor’s tape is not biodegradable, so it should always be removed from the site after the rescue is completed.

A

Space Blanket or Lightweight Tarp For improvising hasty shelters in times of emergency, some form of tarp is essential. In the snow, a slit trench shelter can be built in a matter of minutes using a tarp. Otherwise, the complex and time-consuming construction of improvised structures, such as snow caves, igloos, or tree branch shelters, might be necessary. Typically, little time or help is available for this task during emergencies. In addition, tarps are essential for “hypothermia wraps” when managing injured persons in cold or wet conditions. The only advantage of a space blanket over other tarps is its small size, which means there is a good chance it was packed for the trip.


IMPROVISED EYEGLASSES Exposure of unprotected eyes to ultraviolet radiation at high altitudes may produce photokeratitis (snow blindness). Symptoms are delayed, and the victim is often unaware that an eye injury is developing. When sunglasses are lost at 14,000 ft (4267 m) in the snow, photokeratitis can develop in 20 minutes. One can improvise sunglasses from duct tape, cardboard, or other light-impermeable material that can be cut. Cardboard “glasses” with narrow eye slits can be taped over the eyes for protection. Slits can also be cut into a piece of duct tape that has been folded over on itself with the sticky sides opposing. After a triangular wedge is removed for the nose, apply another piece of tape to secure the glasses to the head. If a sunglass lens is broken or lost, the above technique can be used over the existing frame (Fig. 21-48). Pinhole tape glasses can improve vision in a myopic person whose corrective lenses have been lost. With myopia, parallel light rays from distant objects focus in front of the retina. The pinhole directs entering light to the center of the cornea, where refraction (bending of the light) is unnecessary. Light remains in focus regardless of the refractive error of the eye (Fig. 21-49). Pinhole glasses decrease both illumination and field of vision, so puncture a piece of duct tape or cardboard repeatedly with a safety pin, needle, fork, or other sharp object until enough light can enter to focus on distant objects. Secure the device to the face (Fig. 21-50).

B Figure 21-48. Improvised lens for sunglasses (see text).


IMPROVISED TRANSPORT Carries Two-Hand Seat* Two carriers stand side by side. Each carrier grasps the other carrier’s wrists with opposite hands (e.g., right to left). The victim sits on the rescuers’ joined forearms. The carriers each maintain one free hand to place behind the back of the victim for support (support hands can be joined). This system places great stress on the carriers’ forearms and wrists.

Four-Hand Seat Two carriers stand side by side. Each carrier grasps his or her own right forearm with the left hand, palms facing down. Each *Both the two-hand seat and the four-hand seat are useful only for very short carries over gentle terrain.

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A

Figure 21-49. Pinhole in cardboard to improve vision in person with myopia.

B Figure 21-51. Ski pole seat.A, Ski poles are anchored by the packs.B, The victim is supported by the rescuers.

carrier then grasps the forearm of the other with his or her free hand to form a square “forearm” seat. With the forearm seat, the victim must support himself or herself with a hand around the rescuers’ backs.

Ski Pole or Ice Ax Carry Two carriers with backpacks stand side by side with four ski poles or joined ice ax shafts resting between them and the base of the pack straps (Fig. 21-51). The ski poles or ice ax shafts can be joined with cable ties, adhesive tape, duct tape, wire, or cord. Because the rescuers must walk side by side, this technique requires wide-open, gentle terrain. The victim sits on the padded poles or shaft with his or her arms over the carriers’ shoulders. Figure 21-50. Pinholes in duct tape to improve vision in person with myopia.

Split-Coil Seat (“Tragsitz”) The split-coil seat transport uses a coiled climbing rope to join the rescuer and victim together in a piggyback fashion (Fig. 21-52). The victim must be able to support himself or herself to avoid falling back, or must be tied in.

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A

Figure 21-52. Split-coil seat. A, Rope coil is split. B, Victim climbs through rope. C, Rescuer hoists the sitting victim.

B C

Two-Rescuer Split-Coil Seat The two-rescuer split-coil seat is essentially the same as the splitcoil Tragsitz transport, except that two rescuers split the coil over their shoulders. The victim sits on the low point of the rope between the rescuers (Fig. 21-53). Each rescuer maintains a free hand to help support the victim.

Backpack Carry A large backpack is modified by cutting leg holes at the base. The victim sits in it as would a child in a baby carrier. Some large internal frame packs incorporate a sleeping bag compartment in the lower portion of the pack that includes a compression panel. With this style of pack, the victim can sit on the suspended panel and place his or her legs through the unzipped lower section without damaging the pack, or the victim can simply sit on the internal sleeping bag compression panel without the need to cut holes.

Nylon Webbing Carry Nylon webbing can be used to attach the victim to the rescuer like a backpack (Fig. 21-54). At least 15 to 20 feet (4.6 to

6.1 m) of nylon webbing is needed to construct this transport. The center of the webbing is placed behind the victim and brought forward under the armpits. The webbing is then crossed and brought over the rescuer’s shoulders, then down around the victim’s thighs. The webbing is finally brought forward and tied around the rescuer’s waist. Additional padding is needed for this system, especially around the posterior thighs of the victim.

Three-Person Wheelbarrow Carry This system is extremely efficient and can be used for prolonged periods on relatively rough terrain. The victim places his or her arms over two rescuers’ shoulders (the rescuers stand side by side). The victim’s legs are then placed over a third rescuer’s shoulders. This system equalizes the weight of the victim very efficiently.

Litters (Nonrigid) Many nonrigid litter systems have been developed over the years. These systems are best suited for transporting non– critically injured victims over moderate terrain. They should

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Figure 21-53. Two-rescuer split-coil seat. Balance could be improved by using a longer coil to carry the victim lower.

never be used for trauma victims with potential spine injuries.

Figure 21-54. Webbing carry. Webbing crisscrosses in front of the victim’s chest before passing over the shoulders of the rescuer.

Blanket Litter A simple nonrigid litter can be fabricated from two rigid poles, branches, or skis and a large blanket or tarp. The blanket or tarp is wrapped around the skis or poles as many times as possible and the poles are carried. The blanket or tarp should not be simply draped over the poles. For easier carrying, the poles can be rigged to the base of backpacks. Large external frame packs work best, but internal frame packs can be rigged to do the job. Alternatively, a padded harness to support the litter can be made from a single piece of webbing, in a design similar to a nylon webbing carry.

Tree Pole Litter The tree pole litter is similar to the blanket litter described previously. In the tree pole litter, instead of a blanket or a tarp, the side poles are laced together with webbing or rope and then padded. Again, the poles may be fitted through pack frames to aid carrying. To give this litter more stability and to add tension to the lacing, the rescuer should fabricate a rectangle with rigid cross-bars at both ends before lacing.

Parka Litter Two or more parkas can be used to form a litter (Fig. 21-55). Skis or branches are slipped through the sleeves of heavy parkas, and the parkas are zipped shut with the sleeves inside. Ski edges should be taped first to prevent them from tearing through the parkas.

Internal Frame Pack Litter The internal frame pack litter is constructed from two to three full-size internal frame backpacks, which must have lateral compression straps (day packs are suboptimal). Slide poles or skis through the compression straps; the packs then act as a support surface for the victim.

Life Jacket Litter Life jackets can be placed over paddles or oars to create a makeshift nonrigid litter.

Rope Litter On mountaineering trips, the classic rope litter can be used, but this system offers little back support and should never be used for victims with suspected spine injuries. The rope is uncoiled and staked onto the ground with sixteen 180-degree bends (eight on each side of the rope center). The rope bends should approximate the size of the finished litter. The free rope ends are then used to clove hitch off each bend (leaving 2 inches [5 cm] of bend to the outside of each clove hitch). The leftover rope is threaded through the loops at the outside of each clove hitch. This gives the rescuers a continuous handhold and protects the bends from slipping through the clove hitches. The rope ends are then tied off (Fig. 21-56). The litter is padded with packs, Therm-a-Rest pads, or foam pads. This improvised

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Figure 21-55. Parka litter. On the right, the sleeves are zipped inside to reinforce the litter.

To build an improvised rescue sled or toboggan, the rescuer needs a pair of skis (preferably the victim’s) and two pairs of ski poles; three 2-foot-long (61-cm) sticks (or ski pole sections); 80 feet (24.4 m) of nylon cord; and extra lengths of rope for sled hauling. The skis are placed 2 feet (0.6 m) apart. The first stick is used as the front cross-bar and is lashed to the ski tips. Alternatively, holes can be drilled into the stick and ski tips with an awl, and bolts can be used to fasten them together. The middle stick is lashed to the bindings. One pair of ski poles is placed over the cross-bars (baskets over the ski tips) and lashed down. The second set of poles is lashed to the middle stick with baskets facing back toward the tails. A third rear stick is placed on the tails of the skis and lashed to the poles. The lashings are not wrapped around the skis; the cross-bar simply sits on the tails of the skis under the weight of the victim. Nylon cord is then woven back and forth across the horizontal ski poles. The hauling ropes are passed through the baskets on the front of the sled. The ropes are then brought around the middle cross-bar and back to the front cross-bar. This rigging system reverses the direction of pull on the front cross-bar, making it less likely to slip off the ski tips.38 Another sled design utilizes a predrilled snow shovel incorporated into the front of the sled. A rigid backpack frame can also be used to reinforce the sled. This requires drilling holes into the ski tips and carrying a predrilled shovel. This system holds the skis in a wedge position and may offer slightly greater durability.34 Figure 21-56. Rope litter (see text).

litter is somewhat ungainly and requires six or more rescuers for an evacuation of any distance. A rope litter can be tied to poles or skis to add lateral stability if needed.

Improvised Rescue Sled or Toboggan A sled or toboggan can be constructed from one or more pairs of skis and poles that are lashed, wired, or screwed together. Many designs are possible. Improvised rescue sleds may be clumsy and often bog down hopelessly in deep snow. Nonetheless, they can be useful for transporting a victim over short distances (to a more sheltered camp or to a more appropriate landing zone). They have sometimes been used for more extensive transports, but they do not perform as well as commercial rescue sleds.


A FINAL NOTE Under certain conditions, improvised systems are entirely suboptimal and may not meet standard-of-care criteria. It would, for example, be ill advised to fabricate a litter for transporting a victim with a suspected spine injury when professional rescue is only a few miles away. An improvised litter system might be entirely appropriate, however, if the injured person is 40 miles out and needs transport to a sheltered camp or potential helicopter landing zone. The context of the situation should be considered. At times, persons are obligated to do whatever they can, and a resourceful approach to problem solving combined with a little ingenuity could save a victim’s life.

The references for this chapter can be found on the accompanying DVD-ROM.

Chapter 22: Hunting and Other Weapons Injuries

Hunting and Other Weapons Injuries

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22

Edward J. Otten and David G. Mohler

Even as Nimrod the mighty hunter before the Lord. Genesis 10 : 9 Anthropologists have many theories concerning the origins and importance of hunting in the evolution of the human species. The physical attributes of bipedal locomotion, binocular vision, and an opposable thumb all make humans more efficient hunters. Whether these exist because humans have an innate compulsion to hunt or whether humans are hunters because of these traits is debatable. There is no debate, however, that human social evolution, language, the use of tools, and domestication of animals are directly related to more efficient hunting. In a survival situation, and in some ways with regard to evolution, hunter–gatherer animals have a distinct advantage over strictly vegetarian animals because of the relative food value of meat over plants. Hunters tend to be males. Approximately three fourths of all calories in modern hunter–gatherer groups are derived from plants, and this portion of the food is usually supplied by the women in the group. Even in Eskimo tribes where plants make up little of the diet, the women do most of the fishing while the men hunt. Hominids were at a disadvantage, even in groups, when hunting large animals or driving off other predators from their kills until they began using stones, long bones, and sticks to enhance their relatively weak teeth and claws. Implements for hunting and skinning animals were the earliest tools found by anthropologists. Human cultural evolution followed closely the technological changes in weapons, although sports, business, and war had replaced the need for hunting in most cultures even by the time Nimrod walked the earth. Bows and arrows, slings, spear throwers, nets, harpoons, traps, and firearms were designed to extend the reach and increase the lethality of the human hand. Unfortunately, humans discovered that they could kill each other with these weapons. Since the discovery of gunpowder, the development of weapons technology has surpassed all other forms of human endeavor, including medicine and transportation.6,7,15 Only a few cultures still depend on hunting as their primary food-gathering method. Examples are the Mbuti tribe of the Ituri Forest in Zaire, Andaman Islanders in the Bay of Bengal, and Eskimos. Many cultures, however, use hunting to supplement agriculture, plant gathering, or raising livestock. Most hunting in the United States is done for sport or pleasure, although in some areas of the country hunting and trapping are still the primary source of income for a few people.


HUNTING IN THE UNITED STATES

The total number of hunters and trappers is unknown. Some participate illegally and are not licensed. In 2003, throughout the United States, 14.7 million individuals purchased hunting licenses at a cost of $679.8 million. Although hunting seasons are regulated and relatively short, hunters spent 16 million visitor-days in the national forests. The North American Association of Hunter Safety Coordinators, a division of the New York State Office of Wildlife Management, reported 860 fatal hunting injuries in the United States during the 4-year period of 1983 to 1986, with a total of 6992 injuries from firearms.35a Interestingly, 34% of the total injuries and 89% of the handgun injuries were self-inflicted. Shotguns accounted for 106 of the fatalities and 906 of the total injuries, whereas rifles accounted for 79 fatalities and 465 injuries. The New York State Department of Environmental Conservation reported that the average number of hunting injuries decreased from an average of 137 per year in the decade of the 1960s to only 48 in 2001 and 37 in 2002.24a They credit the institution of hunter safety programs in 1960. In 2001 Colorado reported nine injuries and one death per 500,000 licensed hunters.12a Michigan reported 2 deaths per 2,665,952 hunters in 2003, making hunting one of the lowest injury and fatality rates of any recreational activity.47a The type of hunting also influences the rate of injury. Smith and colleagues reviewed 1345 hunting injuries in Pennsylvania from 1987 to 1999.38 They showed that turkey hunters had the highest rate of injury (7.5 per 100,000 hunters) and grouse hunters the lowest (1.9 per 100,000 hunters). This was attributed to turkey hunters not wearing hunter orange clothing. Deer hunters had the highest casefatality ratio at 10.3%, and pheasant hunters the lowest at 1.3%. This higher fatality rate was largely because most deer hunting injuries were due to wounds caused by rifle bullets. They also noted that younger hunters suffered the highest rate of injuries, and the largest percentage of incidents occurred on opening day. Hunting-related shootings represent a very small portion of the total number of accidental firearm deaths in the United States. Of 131 unintentional firearm deaths in California from 1977 to 1983, only eight were the result of hunting accidents.8,12,27,35,44,47 Hunting injury data may be inaccurate for a number of reasons. Many minor nonfatal injuries may go unreported, and

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most states do not differentiate accidental firearm hunting deaths from deaths that occur during any other activity. Also, automobile and all-terrain vehicle accidents that occur while hunting, or gunshot wounds inflicted while “cleaning a gun” at home, may be classified as hunting or nonhunting injuries.

Types of Injuries Encountered Most injuries to hunters are the same types of injury seen in backpackers, fishermen, and climbers. Frostbite, sprains, burns, and fractures occur with the same frequency in hunters as in others who visit wilderness areas. Prolonged extraction times may increase the risks of hypothermia, wound infection, dehydration, missed medications, and other time-dependent secondary complications. Injuries that are unique to hunters are those caused by their weapons. Most hunting is done with firearms. Shotguns and rifles are more commonly used, although handguns are increasing in popularity. Use of bows and crossbows in hunting is also rapidly increasing. Hunters using these weapons frequently are permitted an extended hunting season that does not overlap with periods for rifle and shotgun hunting. Hunters who use bows and crossbows pose far less danger to people in the hunting area at long range compared with rifles and shotguns. Bow hunting requires more skill, use of camouflage, and stealth because of the short effective ranges of arrows and bolts. These factors place bow hunters at greater risk for being mistaken for a game animal at long ranges, which is why rifle and shotgun seasons rarely run concurrently with bow-hunting activity. Other weapons are used for hunting but are less likely to be encountered. For example, spears, harpoons, and nets are used by some hunters in the Arctic, Australia, and Africa. Spear injuries from gas-powered spearguns or rubber-band powered Hawaiian slings have been associated with fatal injuries, especially when occurring in ocean or lake environments where secondary drowning or shark attack may be an additional hazard. Harpoon and fishing spearheads may separate from the shaft and, depending on the force used, may penetrate the skull or a body cavity. Slingshots are rubber-band–powered devices that use the energy in a stretched piece of rubber to hurl a projectile, often a small rock or ball bearing, at 200 to 300 feet (61 to 91 m) per second. Although this is considered a low-velocity and thus low-energy projectile, injuries to the head and face, especially the eyes, have been reported. Blowguns, while mainly used by aboriginal hunters, have become popular with some recreational hunters of birds and small game. The blowgun varies in length, and a variety of darts can be projected 20 to 50 feet (6 to 15 m) by the exhaled breath. The darts have low energy and do not penetrate very deeply. Modern blowguns rarely cause serious injury unless striking the eye or possibly a blood vessel. To effectively kill small game, the darts generally must carry an immobilizing or poisonous toxin. Darts used by some tribes contain toxins such as curare or batrachotoxin, which can be fatal to humans. Trap injuries may be included in the definition of hunting injuries. Most traps are designed to catch and hold small game. Injuries usually occur when a trapper triggers a spring-loaded trap prematurely. Crush injuries and puncture wounds to the hands are most common. Hikers occasionally tread on unmarked traps, and domestic animals such as dogs are accidentally caught in poachers’ traps. Another problem with traps occurs when an animal (wild or domestic) is caught in a trap and attacks the trapper while being released.

Figure 22-1. The wrong way to use a tree stand.This hunter is not wearing a safety harness, is drinking alcohol, and is pulling his firearm into the tree stand with the muzzle pointing upward.

Many knife lacerations occur when hunters clean game. Lack of familiarity with the process or techniques for field dressing and cleaning game is the likely cause. Failing to wear protective gloves; using the wrong type of knife; working with bloody, slippery material; and having cold hands all contribute to accidents.

Tree Stand Injuries A frequent preventable cause of serious injury and death among hunters is not associated with firearms at all. It is the tree stand injury. Tree stands are small platforms designed to hold hunters high above the ground so they can more easily spot and kill large game while remaining undetected. Whether homemade or of commercial design, the platforms generally are small, portable devices that the hunter attaches to the trunk of a tree near game trails or water holes. The stands may have attached ropes or ladders for access, or the hunter may free-climb the tree for placement of the stand or fasten small climbing steps on the tree (Figs. 22-1 and 22-2). Hunters may fall asleep on the platforms and fall off, or fall while climbing up or down trees. At least half of these injuries could be prevented if all

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Figure 22-2. A commercially produced tree stand can be used to climb the tree and obviates the need for a ladder or steps, which are the cause of many falls.

Figure 22-3. The correct way to bring a firearm or quiver into the tree stand, with the muzzle or arrowheads pointing down and the hunter wearing a safety harness at all times.

hunters wore tree stand safety harnesses (Fig. 22-3). Although most of the injuries are similar to those seen with any type of fall, occasionally a hunter drops a firearm, which discharges, or falls on an arrow or rifle, causing an additional weapons injury. Over 10 years, injuries of this type in Georgia accounted for 36% of reported hunting injuries and 20% of hunting fatalities.9 A study from the University of Rochester, New York, looked at tree-stand injuries from 1996 to 2001.34 The authors noted that 51 injuries occurred, all in men with a mean age of 42. Alcohol was present in 10% of patients and 2 of 3 deaths. Spinal fractures were the most common injury (51%), followed by extremity (41%), head (24%) and lung injuries (22%). Only two patients had been using a safety belt (4%). Sixteen spinal cord injuries were reported from 1987 to 1999 in Oklahoma; the mean height of fall was 16 feet, and 18% were related to alcohol ingestion.41 Ninety percent resulted in paraplegia/ paresis, and 12.5% were fatal.34,41,43

wooden arrows. A number of types of arrowhead are in use, such as field points and target points, but most injuries are due to specially designed hunting arrowheads called broadheads. These razor-sharp metal points come in a variety of sizes and shapes and are designed to kill game by lacerating tissue and blood vessels, causing bleeding and shock. Unlike hunting firearms projectiles, which are designed to kill quickly through massive tissue damage and rapid incapacitating hemorrhage, arrows usually kill more slowly with less tissue damage (Fig. 22-4).4,22,24 Arrows are propelled by a conventional bow, which may be straight, recurved, or compound, or by a crossbow. Crossbow projectiles may be called arrows or bolts and generally are shorter and heavier than arrows fired from a bow. The force used to propel the arrow is usually measured in draw weight, which is the number of foot-pounds necessary to draw a 28-inch (71.1 cm) arrow to its full length. The higher the pound draw, the more powerful the bow and the deeper the penetration the same type of arrow will have. Arrows have a much shorter range than bullets do, and arrows must be more accurately placed to kill the animal quickly; therefore, most shots are taken under 164 feet (50 m).

Arrow Injuries Modern arrows are usually made from aluminum, graphite, or fiberglass, although many beginners still use inexpensive

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PART FOUR: INJURIES AND MEDICAL INTERVENTIONS and colleagues estimated 21,840 injuries in 2000 from nonpowder firearms, with a 4% hospitalization rate.28 There were 39 resultant deaths between 1990 and 2000. Care must be taken not to trivialize these injuries, especially in the pediatric patient where softer, thinner bone may lead to deep penetration of even lightweight projectiles.

Figure 22-4. Types of arrows.Top, Aluminum shaft arrow with hunting broadhead.Middle (left to right), Four field points of various weights: two types of broadheads and small game blunt hunting head with spring claws to prevent arrow loss from burrowing into the ground. Bottom, Fiberglass shaft for interchangeable heads.

Because brush and tree branches can easily deflect an arrow, most shots are taken with a clear field of view. For these reasons, bow hunters rarely mistakenly shoot another hunter they presumed was a game animal. Most arrow injuries occur when hunters fire illegally at night in heavy brush and are not sure of their target. Another common injury occurs when a hunter runs after a wounded animal and falls on an arrow that was to be used for a second shot or falls out of a tree stand onto an arrow. A loaded crossbow is similar to a loaded gun. Hunters have been accidentally shot when dropping the weapon or snagging the trigger on a branch or fence. Hunting arrowheads are quite sharp; self-inflicted injuries may occur when a hunter is sharpening the blades of the broadhead or returning an arrow to the quiver.

Injuries from Firearms Nonpowder Firearms. Although the word firearms technically defines guns that fire projectiles by ignition and burning of a propellant, similar designs referred to as “nonpowder” firearms using springs, compressed air, or compressed gas cartridges are in widespread use among sportsmen and children, and will be considered as firearms in practical use. Whereas traditional firearms discharge a projectile by the contained expanding gases generated in the gun barrel by modern fast-burning powders or old-fashioned black powder, nonpowder firearms use a spring, compressed air, or a carbon dioxide cartridge to accelerate the projectile out the barrel. Although air guns are quite accurate at short distances and can develop muzzle velocities in excess of 1200 feet per second, the small lightweight projectiles cannot usually penetrate skin at distances greater than 328 feet (100 m). Nonpowder firearms are commonly used by children, who cannot legally obtain or use other types of firearms. Uninformed parents buy them as toys, erroneously believing them to be harmless by design. Without supervision and proper training in gun safety, severe injury and death can result. The wounds they cause can be lethal, especially from high-powered air rifles, which can send out pointed projectiles at sufficiently high velocities to penetrate the skull and body cavities. In a recent technical report, Laraque

Powder Firearms. In older style weapons (black powder weapons), gunpowder is loaded directly into the barrel. In modern weapons, gunpowder is contained in a cartridge. Black powder weapons use a centuries-old slow-burning propellant that is ignited with a spark from flint striking steel or a percussion cap. The firearms are usually single shot and are loaded from the muzzle by pouring a measured amount of black powder down the barrel, and then inserting the projectile and tamping it down onto the powder charge. When ignited, the propellant is converted to a gas that expands and pushes the projectile out of the barrel of the weapon. With modern design and manufacturing techniques, these weapons are sufficiently accurate to hunt large game, such as deer and elk. The injuries from black powder weapons are similar to those from modern weapons and are discussed later. The same precautions should be used when hunting with or shooting any type of firearm, whether the propellant is air or gunpowder.29,33,46 The term cartridge is used to refer to the intact, unfired assembly of projectile and propellant loaded into the gun for firing. Rifle and pistol cartridges consist of a metal case that contains the gunpowder propellant and into which the bullet is seated and held by compressing the case around the bullet base at the time of manufacture. The base of the case contains a small metal primer filled with a small amount of high explosive that serves to ignite the fast-burning propellant when it is struck by the firing pin of the gun. The primer is in the center of the base of the case (center-fire ammunition) in all cartridges except in small-caliber .22 cartridges, where it is incorporated into the entire circumference of the cartridge base rim (known as rimfire ammunition). Rifle and pistol cartridges generally contain a single bullet, although some may be loaded with very small shot to increase the probability of hitting small objects at short distances. Shotgun cartridges consist of a center-fire metal base combined with a paper or plastic shell in the form of a closedend tube. Within this tube is placed the propellant and then the projectile(s) along with associated plastic, cotton, or paper materials collectively referred to as wadding. Shotgun projectiles consist of shot ranging in size from 1 mm to 10 mm (Fig. 22-5) or a single solid projectile known as a slug. Shot pellets used to be made of lead. Because of high lead levels in ducks and geese who ingested spent shot while feeding, lead shot for bird hunting was banned in 1991. Approved shot may be made of steel, tin, or various mixtures of tin, bismuth, and up to 15% iron. Steel shot can be identified on radiographs because it retains a perfect round shape, whereas lead and tin shot deforms inside the barrel during firing, resulting in nonspherical shapes. Determining the shot type can help clinicians decide about the safety and utility of MRI scans in the setting of steel projectiles, or the risk of lead toxicity. The wadding is commonly a single plastic cup with a thickened expandable base designed to contain the shot and serve as a seal inside the barrel to contain the expanding gases behind the shot cup for maximal muzzle velocity. Slugs also have a type of wadding known as a sabot, which surrounds the slug inside the barrel of the shotgun. In all cases, the wadding is fired from

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Lead shot sizes:

Pellet diameter (inches) (mm)

Figure 22-5. Standard shot size number and letter system (with corresponding metric measurements) of hunting shotgun shell projectiles. The smaller the shot size, the more pellets loaded in a single shotgun shell. Larger pellets are heavier, lose less velocity per unit of flight time, and penetrate more deeply than smaller pellets.(From Shotgunworld.com.Used with permission.)

12

.05 1.27

9

81/2

8

71/2

.080 2.30

.085 2.16

.090 2.29

.095 2.41

Buck shot sizes:

No. 4

No. 3

No. 2

Pellet diameter (inches) (mm)

.24 6.10

.25 6.35

.27 6.86

Steel shot sizes:

6

Pellet diameter (inches) (mm)

5

.11 .12 2.79 3.05

4

3

6

.110 2.79

No. 1

.30 7.62

2

.13 .14 .15 3.30 3.56 3.81

1

5

4

.120 3.05

.130 3.30

2

BB

.150 3.81

.180 4.57

No. 0

No. 00

No. 000

.32 8.13

.33 8.38

.36 9.14

Air Rifle

.16 .177 4.06 4.49

BB BBB

T

.18 .19 .20 4.57 4.83 5.08

F

.22 5.59

Note: the size of shot, whether lead or steel, is based on American Standard shot sizes. Thus, a steel No. 4 pellet and a lead No. 4 pellet are both .13 inches (3.3 mm) in diameter.

the gun and immediately peels away from the slug or shot. Wadding is commonly found inside close-range wound channels but generally is not involved in wounds at ranges more than 16 to 23 feet (5 to 7 m). Besides the wadding and projectile(s), hot gas and unburned powder also exit the muzzle. In cases of close-proximity wounds, usually under 31/2 feet (∼1 m), powder stippling may appear on clothing or skin. The presence of wadding in a wound or powder stippling may have important forensic applications and should always be noted. With contact wounds where the muzzle is pressed into the skin at the time of firing, the escaping hot gases may enter the wound channel and expand inside the victim, causing burning, organ damage, bursting of the skin, and a stellate laceration around the point of entrance. Figures 22-6 to 22-8 show examples of gunshot wounds. Hundreds of types of cartridges are available for firearms. They may be factory loaded or hand loaded, which adds the variables of propellant amount and type. Rifle and pistol cartridges are initially classified according to caliber, or diameter, of the bullet. For example, .22 caliber means the diameter of the bullet is 0.22 inch (5.6 mm); .45 caliber is 0.45 inch; and so forth. The caliber may be expressed in metric measurement; for

Figure 22-6. Gunshot wound to the face and mandible showing extensive bone and soft tissue injury. Patient was initially able to protect his airway, but later required endotracheal intubation because of edema and bleeding.

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Figure 22-7. Shotgun wound to the upper arm. Initially, the wound looked benign. Both entrance and exit can be seen.

Figure 22-9. Examples of hunting bullets. Left to right, .50 caliber black powder lead bullet, .22 caliber lead bullet, .22 caliber long rifle lead bullet, .44 magnum semijacketed hollowpoint bullet, .44 magnum shotshell, .223 caliber (5.56 mm) full metal jacket bullet, .22/250 caliber semijacketed soft point bullet,.30/30 caliber soft point flat nose bullet,.270 caliber pointed soft point bullet, and .30-06 caliber round nose soft point bullet.

Figure 22-8. Radiograph of the same shotgun wound to the upper arm as seen in Figure 22-7. Extensive bone and soft tissue injury, as well as vascular and nerve damage, can be seen.

example, a 9-mm bullet is 9 mm in diameter, which also happens to be 0.357 inch. However, bullet diameter alone is insufficient to name a cartridge, because bullet length can vary, as do cartridge length and width. The U.S. Army M-16 service rifle fires a .22 caliber bullet weighing 62 grains at 3100 feet (945 m) per second. The common .22 rimfire rifle used by generations of young shooters fires a .22-caliber bullet weighing 40 grains at 1100 feet (335.3 m) per second initial velocity. Obviously, the wounding potential of these two projectiles is vastly different. Nomenclature for a particular cartridge is made more specific by including a measurement of cartridge length, name of the inventor or inventing company, amount of powder in the case, length of the entire cartridge, or the year the cartridge was invented. For instance, the M-16 round is generally referred to as a 5.56 × 45 mm (metric), or a .223 cartridge (English system of measurement), with the third digit differentiating it from the common low power .22 rimfire cartridge. Other common hunting cartridge names illustrating these variations are .45/70 (70 grains of powder), .30-06 (adopted in 1906), and .35 Whelen (the man who developed the round).

Figure 22-10. Examples of shotgun rounds. Left to right, 12-gauge slug round, empty 12gauge plastic round, plastic 12-gauge wadding, and number six shotgun pellets.

The recent introduction of the term magnum refers more to the type and amount of powder than to the size of the bullet used. Magnum cartridges are designed to give hunters the ability to successfully hunt large game with pistols by improving terminal ballistic performance of the bullet. Figure 22-9 shows some examples of different bullets. Shotgun terminology is a little less complicated, based on the number of lead balls, the diameter of the barrel, and how many lead balls it takes to make a pound. For example, a 12-gauge shotgun has a barrel that is the same diameter as a lead ball that weighs 1/12 pound; a 20gauge, 1/20 pound. The higher the gauge number, the smaller the barrel and the smaller the projectile. The only exception is the .410 shotgun, which is caliber .410 or 0.410 inch in diameter. Figure 22-10 shows some examples of shotgun rounds and the shot and wadding within them.

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TABLE 22-1. Comparison of Bullet Caliber,Weight,Velocity, and Muzzle Energy MUZZLE VELOCITY CALIBER .22 .223 .44 magnum .30/60

WEIGHT (GRAINS)

Feet/sec

M/sec

MUZZLE ENERGY (FOOT-POUNDS)

40 55 180 150

1080 3250 1600 2750

329 991 488 838

90 1280 1045 2500

The type and severity of wounds inflicted by a firearm depend on several factors. The most often quoted factor, but the least important, is the amount of energy the bullet (projectile) has when leaving the firearm. The kinetic energy formula, KE = 1 /2 MV2, can be applied to any moving object and can be used to calculate the muzzle energy for a particular type of firearm. Energy increases much more as a function of the velocity of the bullet than as a function of the mass. For this reason, most firearms are classified according to muzzle velocity. The higher the velocity of the bullet, the greater the energy and the greater the potential for injury. Firearms with muzzle velocities greater than 2500 feet (762 m) per second are considered high velocity, 1500 to 2500 feet (457–762 m) per second are medium velocity, and less than 1500 feet per second are low velocity (Table 22-1). Bullets cause damage to tissue by crushing. The energy of a bullet may be transmitted to the tissue in part or in total depending on the surface area the bullet presents to the tissue. Bullets that yaw, expand, or fragment present more surface area than do bullets that stay in one axis and maintain one shape. By international agreement codified in the articles of the Hague Convention IV of 1907, military bullets are not to be designed in a manner to produce “superfluous” wounding effects by features that would encourage the bullets to flatten or expand on impact with tissue. They are typically completely encased in a copper jacket to prevent deformation of the soft lead core. Such rounds generally pass through an individual, leaving a permanent wound tract similar in diameter to that of the bullet. The ammunition is designed to wound a soldier and put him out of combat, but not to kill him. In contrast, hunting ammunition is designed to expand on impact up to 2 or 3 times its diameter, resulting in a much larger wound channel, greater tissue damage and rapid incapacitation and death (Fig. 22-11). This feature of planned deformation also promotes retention of the bullet within the target and reduces the risk of injury to unseen individuals downrange from the game animal. In fact, many states require the use of expanding ammunition for hunting large game, and this may increase the wound severity of hunting injuries compared to military and criminal shootings. In addition to direct tissue destruction by the deforming bullet, fragmentation may occur when a bullet strikes bone and sends bone and bullet fragments in several directions. These secondary missiles cause injuries within the body similar to those from bullet fragments and may even exit the body to injure bystanders. A second injury mechanism of terminal ballistic bullet behavior is temporary cavitation, which occurs at all velocities to some degree but becomes a significant wounding mechanism factor only at high velocities. The temporary

Figure 22-11. The .30-caliber Nosler 180 g Accubond Polymer Tip bullet fired into calibrated 10% ordnance gelatin is typical of the .30 caliber hunting bullets used for .30-06,.308,.300 Win Mag, and other cartridges.This photo shows this bullet fired from a .308 rifle with an 18-inchlong barrel. Muzzle velocity was 2,499 feet (762 m) per second. Penetration depth exceeded 20 inches (51 cm).Temporary cavity maximum width was 4.7 inches (11.99 cm) at a depth between 2.8 inches (7.11 cm) and 8.7 inches (22.1 cm). Diameter of the recovered bullet at the front surface was 0.56 inches.Weight of the recovered bullet was 149.5 g; 17% of the bullet turned into fragments. Terminal performance of this type is suitable for all medium to heavy game encountered in the lower 48 U.S. states, including moose, elk, black bear, pigs, and deer. Tencent coin (dime) is shown for comparison. (Courtesy of Gary K. Roberts, DDS.)

cavity is created by radial dispersion of tissue by the bullet surface as a result of acceleration of tissue away from its path. A permanent cavity occurs when a bullet or fragment crushes tissue. In high-velocity bullet wounds, the temporary cavity may be many times larger than the permanent cavity. This wave is well tolerated by most elastic tissue, such as muscle, bowel, and lung; however, inelastic tissues, such as liver or brain, do not tolerate it and may be severely damaged by the temporary cavity.

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Bullet motion in flight is described by rotation, yaw, and pitch. The rifle grooves cut into the inside of the barrel cause the bullet to spin around its long axis, just like a football thrown in a tight spiral. Yaw and pitch describe bullet motion left or right, or up and down relative to the long axis of the bullet. In wound ballistics, yaw is used to describe both axes of motion. A rifle bullet will usually yaw after striking any object outside the body such as a tree branch, belt, or clothing and when striking skin and other tissue within the body. Yaw can result in complete end-over-end rotation of the bullet within tissue, causing the bullet to increase the area that is crushed as the entire side profile of the bullet passes through the tissue. Bullets with round ends, for example the .45 automatic Colt pistol bullet or round musket balls, routinely do not yaw, and produce wound channels equal to their caliber or expanded caliber. Yaw causes maximum damage at 90 degrees of rotation, when the entire side profile of the bullet crushes tissue. This factor, combined with any bullet expansion, can cause the exiting bullet to produce a much larger wound than when it entered. In order to allow laboratory comparison of projectile designs and to study the effect of velocity and expansion, experimental wounding profiles have been described using ballistic gelatin, which accurately simulates human muscle tissue. These wounding profiles show the various aspects of potential ballistic injury including the cavitation, yaw, and fragmentation (Figs. 22-12 and 22-13).13 The total effect of high energy, fragmentation, expansion, yaw, and temporary cavity formation results in

tissue injury. Although the kinetic energy formula yields the total energy available to cause injury, the physical behavior of the projectile(s) and the transited tissues are the actual determinants of the complete injury pattern. The type of tissue struck is the most important factor. As can be seen from Table 22-1, the .22-caliber long rifle rimfire bullet has a low mass and velocity and thus a low muzzle energy, yet more fatalities have occurred from this round than from any other. It is very inexpensive, can be fired from a number of rifles and handguns, is commonly used to hunt game, and is not thought of as particularly dangerous by inexperienced hunters. For these reasons, more people are shot by this cartridge than any other single bullet type. The bullet is highly lethal when striking the brain, heart, or major blood vessel.1,2,16–20,32,42,45 Rubber or plastic bullets, while generally not used for hunting, may be encountered. These bullets travel at about 200 feet (61 m) per second and will not usually penetrate skin, although at short ranges (under 50 feet [15 m]) can cause fractures, eye trauma, and other blunt injuries.13 Other rare problems associated with firearms are explosions that occur within the firearm itself. These can cause burns or fragment types of injuries. When firearms are loaded with excessive amounts of powder or when the wrong powder is used in reloading bullets, the resultant detonation may cause the frame or cylinder of the firearm to explode. The burning powder or fragments of metal can cause injuries to the shooter. These injuries usually occur to the face and hands; penetrating eye injuries are also common. Obstruction of the barrel of the firearm by snow, mud, or other foreign material may cause a similar explosion.

Trap Injuries

Figure 22-12. Wound profile of a .223 rifle bullet in 10% ballistic gelatin showing the permanent and temporary cavities and the effect of tumbling and fragmentation.

Figure 22-13. The path of a test bullet through ballistic gelatin suggests the amount of tissue damage that a hunting bullet can do inside the human body, even if entrance and exit wounds are small.The data for this bullet are given with Figure 22-11.(Courtesy of Gary K.Roberts,DDS.)

Traps are designed either to kill animals or to capture them alive and uninjured. The latter type poses no risk to humans unless they should happen upon a trap and attempt to free the animal or otherwise approach the trap. The trapped animal often will bite or claw anyone within range. Leghold traps designed to kill or injure an animal may occasionally cause problems for unwary hikers or campers. These traps have a spring-loaded jaw that closes when triggered by something touching the trigger plate, usually involving only 1 to 2 pounds (1/2 to 1 kg) of pressure. Most injuries involve the foot, but any area of the body that can fit between the jaws potentially can be injured. The jaws can be released by compressing the spring controlling the jaws (Fig. 22-14). Very large traps used to trap poachers or to catch large animals, such as tigers or bears, cannot easily be released without help. These traps may also be attached to large weights, such as logs or concrete blocks, to prevent escape. Fortunately, most of these large traps are now collector’s items and not used in the field. Many injuries occur when the person setting the trap inadvertently causes the trap to spring before being set in the ground. This often causes hand and finger injuries, especially with amateur trappers unfamiliar with the type of trap (Fig. 22-15). Unconventional traps, such as snares, deadfalls, and pit traps, may rarely be encountered, but the mechanisms and types of injuries are quite variable. Trap guns are illegal in most areas of the world; injuries are similar to gunshot wounds.

Treatment of Hunting Injuries Treatment of hunting injuries involves standard principles and priorities of trauma care. Airway, breathing, circulation, bleed-

Chapter 22: Hunting and Other Weapons Injuries ing control, immobilization of the spine and fractured extremities, wound care, and stabilization of the victim for transport should be performed in an expedient manner. The victim should always be disarmed to prevent accidental injury to the rescuer or further injury to the victim. Removing the firearm or arrow from

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the vicinity of patient care is usually sufficient, but ideally the firearm should be made safe by removal of the ammunition and opening of the firing chamber. Arrows should be placed in a quiver, or the points may be wrapped in cloth to prevent injury.

A

B

C

D

E Figure 22-14. A, A leghold trap set. B and C, A leghold trap sprung. D and E, To release a trap that has been sprung, stand on each end of the trap and compress the spring.

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Figure 22-16. Arrow wound to the left side of the neck near the mandible. The shape of the wound resembles the blades of the broadhead as shown in Figure 22-4. Figure 22-15. Spring traps must be set carefully to avoid injury to the person setting the trap.

The management of common traumatic injuries and illnesses, such as hypothermia and mountain sickness, is no different except for one important point: always disarm the victim. A victim with a charged weapon and a head injury or change in mental status for any reason presents an immediate danger to a well-meaning rescuer. If the person attempting to offer aid to an injured hunter is not familiar with weapons, it is usually best to move the weapon several feet from the victim and point it in a direction where an accidental discharge will do the least harm.

Arrow Injuries Lacerations from razor-sharp hunting points are not unusual and can be treated like any similar laceration. The wound should be irrigated, any foreign material removed, and the laceration closed primarily. Victims pierced by an arrow should be stabilized, and the arrow should be left in place during transport, if possible. Attempts to remove the arrow by pulling it out or pushing it through the wound may cause significantly more injury and should be avoided. It is acceptable to cut off the shaft of the arrow and leave 3 or 4 inches (8 to 10 cm) protruding from the wound to make transport easier if this can be accomplished with a minimum of arrow movement. A large pair of paramedic-type shears can usually cut through an arrow shaft if it is stabilized during cutting. The portion of the arrow that remains in the wound should be fixed with gauze pads or cloth and tape. A similar approach should be used for spears and knives. The victim should be transferred as quickly as possible to an operating room, where the arrow can be removed under controlled conditions. Radiographs are helpful to identify associated anatomic structures before removal is attempted in the operating room (Fig. 22-16).

Gunshot Wounds Myths about Gunshot Wounds. Many myths associated with the management of gunshot wounds should be repudiated. Myth 1: The size or caliber of the bullet can be determined by the size of the wound. In truth, the skin is quite elastic and has high tensile strength. Although a knife or arrow can cut the skin, a blunt bullet must crush the tissue by stretching. This

stretching occurs until the bullet passes through and then retracts, causing the wound in the skin to be smaller than the caliber of the bullet. Myth 2: The size of the wound determines whether it is an exit or entrance wound. Actually, the bullet usually tumbles or yaws after striking the skin and soft tissue; if the bullet exits while still tumbling, the exit wound may be larger than the entrance. This commonly occurs when a missile strikes an arm or leg where the bullet is in mid-tumble at 90 degrees when exiting. Often the bullet fragments, and only a small portion of the bullet exits, making the exit wound much smaller than the entrance. In addition, pieces of bone or tooth may exit, causing an odd-size wound. Myth 3: The path of the bullet can be determined by connecting the entrance and exit wounds. This myth may lead to inappropriate intervention in gunshot wounds. A case example: A gunshot-wound victim had two wounds about 6 inches (15 cm) apart on his upper thigh, and they were initially thought to be an entrance and exit wound. The patient developed abdominal pain, and on chest x-ray it was noted that there were two bullets in the left chest. Subsequent surgical intervention revealed injury to the colon, spleen, bowel, stomach, diaphragm, lung, and subclavian vessels. So what appeared to be entrance and exit wounds were actually two gunshot wounds sustained while the patient was lying supine. The outcome of most gunshot and blast wounds depends primarily on the body part that has been injured, and secondarily on the environment in which the injury occurred and the quality and timeliness of medical intervention. While knowing the type of weapon and the physics of ballistics and blast can help predict the extent of physical damage, there is no substitute for attention to detail when examining the patient.

Emergency Department Care. Emergency department care of the gunshot wound includes securing the airway, placing two intravenous lines in unaffected extremities, performing cardiac monitoring, and providing oxygen therapy. The patient with a neck wound and expanding hematoma should be endotracheally intubated as soon as possible. If endotracheal intubation is not possible, a needle cricothyrotomy followed by a tube

Chapter 22: Hunting and Other Weapons Injuries cricothyrotomy should be performed. Relief of tension pneumothorax with a needle or tube thoracostomy or occlusion of a sucking chest wound should be done immediately. Any external bleeding should be controlled by direct pressure. In a wilderness situation, a tourniquet may be the best means of controlling significant bleeding in a manner that is less labor intensive. A radiograph should be obtained of the involved area, and where there is a presumed entrance wound without an exit wound, multiple x-ray studies may be needed to find the location of the bullet. On rare occasion, bullets have been observed to embolize from the chest area via the aorta to the lower extremity arteries or to the heart via the vena cava. A type and crossmatch and basic trauma laboratory tests should be performed. Tetanus toxoid and immunoglobulin should be administered as indicated by the victim’s history. Broad-spectrum antibiotics should be administered to cover the wide range of pathogens associated with gunshot wounds, especially with complex wounds to the abdomen and extremities. The bacteriology of gunshot and blast injury wounds is quite complex. There are a number of environmental pathogens, including soil and water bacteria, such as Clostridium, Aeromonas, Staphylococcus, Streptococcus, Bacteroides, and Bacillus. These bacteria and associated bacteria on the victim’s clothing and skin account for the majority of infections in soft tissue. Wounds penetrating the abdomen increase the presence of Pseudomonas, Proteus, E. coli, and other coliforms. Systemic antibiotics should be started as soon as possible and continued for at least 24 hours. Although there is no specific antibiotic that will cover all organisms, selection of antibiotic should be on the basis of probable type of infection. Cellulitis and necrotizing soft-tissue infections can be treated with ceftriaxone plus metronidazole plus gentamicin. Intra-abdominal infections can be treated with the same regimen or cefotetan, and ampicillin– sulbactam can be substituted for ceftriaxone, clindamycin for metronidazole, and ciprofloxacin for gentamicin. There is no substitute for drainage of abscesses and empyemas, excision of devitalized tissue, and removal of foreign debris. Topical antibiotics have not been shown to be useful. Surgical debridement and systemic antibiotics are the mainstay of prevention and treatment of wound infection. Victims in shock should be taken to the operating room immediately to control bleeding. If this is not possible, type Onegative or type-specific blood should be transfused. Autotransfusion, when available, can be an ideal way to replace lost blood in the victim in shock. Starch or other blood substitutes may raise the blood pressure temporarily, but large amounts of crystalloid fluids may cause increased bleeding. Hypotensive resuscitation, which allows the patient to remain relatively hypotensive as long as organ perfusion is adequate, may be the best intervention if an operating room is not readily available. A systolic blood pressure of 80 mmHg may not be “normal,” but it may be sufficient for a supine patient. Increasing the blood pressure to 110 mmHg may seem “normal,” but it may also cause rebleeding and irreversible shock. Military antishock trousers or pneumatic antishock garments have not been shown to be beneficial in the treatment of shock secondary to penetrating trauma.5a Emergency thoracotomy is indicated for victims who have lost vital signs shortly before reaching the emergency department or while in the emergency department. Injuries to the heart or great vessels can be occluded with Foley catheter balloons, pericardial tamponade can be relieved, and the aorta can be cross-clamped. Hypothermia is commonly

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unrecognized in the trauma victim and may lead to coagulopathy, cardiac arrhythmias, or electrolyte disturbances. Rectal temperatures should be obtained and only warmed fluids and blood given to the victim.13 Wounds from high-velocity bullets are similar to other types of wounds, and standard rules of debridement should be followed. Wide debridement of normal-appearing tissue is unnecessary and should not be done. In general, victims of gunshot wounds should be evacuated quickly and stabilized if possible. Most victims (80%) of gunshot wounds to the chest who survive the first 30 minutes can be treated with a thoracostomy tube and observation.26a The amount of blood that is drained from the thoracostomy tube determines whether operative intervention is necessary. Draining > 1500 mL of blood immediately or > 200 mL/hour for over 4 hours is an indication for thoracotomy. Signs of pericardial tamponade are an indication for immediate pericardiocentesis and operative repair. All gunshot wounds to the abdomen should be explored in the operating room. These include all penetrating injuries below the nipples and above the symphysis pubis. Radiographs should be used to identify bullets, bullet fragments, and bony injuries. Extremity wounds can be treated conservatively unless signs of vascular injury are present. Signs of arterial injury include pulsatile bleeding, expanding hematoma, absent pulses, presence of a thrill or bruit, or an ischemic limb. Experience in combat has shown that vascular injuries do best when identified and treated immediately. However, life takes priority over limb, and a tourniquet may be needed to control vascular bleeding that may ultimately lead to loss of the limb. Obviously, major bony injuries and nerve injuries eventually need operative therapy, but immediate intervention is rarely necessary. Most important, the underlying injury cannot be determined by examination of the external wound. Vascular injuries may not be identified during the initial examination; therefore noninvasive, portable, Doppler ultrasound studies can be extremely valuable in the emergency department. Contrast angiography should be performed on any victim with a suspected vascular injury. The removal of the bullet or bullet fragment is not necessary unless the bullet is intravascular, intra-articular, or in contact with nervous tissue, such as the spinal cord or a peripheral nerve. Bullets found during exploratory laparotomy or wound debridement should be removed, but it is unnecessary to explore soft tissue, such as muscle or fat, solely to remove a bullet. Shotgun pellets that have minimal penetration can be removed from the skin with a forceps. Often plastic or cloth wadding is found in superficial shotgun wounds and should be removed. Shotgun blasts may produce large soft tissue defects that need extensive debridement and either skin grafting or surgical flap rotation to maximize coverage. Patients with powder burns should have as much of the powder residue removed as possible with a brush under local anesthesia. The powder will tattoo the skin if it is not removed, and the deep burns may need dermabrasion or surgical debridement (Fig. 22-17).17,32,45 Retained lead bullets and shotgun pellets for the most part are not hazardous; however, when they are within joint spaces or the gastrointestinal tract, significant amounts of lead can be absorbed and toxicity can occur.40

Prevention of Hunting Injuries Most state fish and wildlife agencies have recognized that hunters are at risk for injuries and have tried to develop pro-

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A

B Figure 22-17. A, Close-range 12-gauge shotgun wound to the right side of the upper chest. The large central wound was caused by the plastic wadding, and the pellets have struck at an angle toward the shoulder.The patient was turning to the right when shot.The external appearance of the wound indicates a massive injury to the chest.B, Chest radiograph of the patient in A. No pellets have penetrated the chest, and there was no pneumothorax, pulmonary contusion,or vascular injury.The injury was totally superficial,and the patient was admitted for observation and local wound care.

grams to minimize morbidity and mortality. National organizations such as the Boy Scouts of America and the National Rifle Association have been teaching firearm and hunting safety for decades. The Hunter Education Association and the North American Association of Hunter Safety Coordinators (NAAHSC) have attempted to identify high-risk groups and situations by collecting data on both fatal and nonfatal huntingrelated injuries. NAAHSC-approved Hunter Safety Programs are available in every state, and all states except Alaska, Massachusetts, and South Carolina require the course before issuing a license to hunt. These courses are roughly 12 hours long and cover hunter responsibility, firearms and ammunition, bow hunting, personal safety, game care, and wildlife identification. They stress respect for the wilderness and a rational approach to game management. All hunters, potential hunters, and

Figure 22-18. Hunter wearing bright orange clothing, which is essential to distinguish a human from the background and avoid an accidental shooting.Many accidental shootings have occurred when one hunter’s movement was mistaken by another hunter for the movement of an animal.

persons going into hunting areas should take one of these courses. Approximately 650,000 hunters complete a hunter safety course annually. Since the first course given in Kentucky in 1946, more than 18 million hunters have been certified. Most injuries could probably be prevented by following a few simple rules. Nonhunters should be aware of hunting seasons and designated hunting areas and wear international orange clothing while in hunting areas (Fig. 22-18). Hunters should always be sure of their target before shooting, use safety harnesses in tree stands, and use appropriate technique and tools for cleaning game. Tree stands should be well constructed. Hunters should never consume alcohol or mind-altering drugs that might interfere with their judgment. Eye protection in the form of safety glasses should be worn while hunting or target shooting to prevent injuries from ricocheting fragments and shotgun pellets. High-frequency hearing loss is common in hunters because of the loud report of the firearm. Although earplugs and headsets can protect the hunter, they are impractical for most hunting and are used mainly for target shooting. Some hunters use a single ear plug for the ear closest to the muzzle of the firearm. This protects the ear most likely to be injured but still allows the hunter to hear approaching game

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and other hunters. Bow hunters should always use wrist and finger protection to prevent injuries from the arrow fletching and the bowstring. All arrows should be carried in a quiver until ready for use. The broadhead arrow should always be pointed away from the hunter. These few steps would probably eliminate most hunting injuries.36,37


FISHING INJURIES Sport fishing is associated with a large number of relatively minor injuries compared with hunting. The usual problems associated with outdoor recreation are common among fishermen: sunburn, frostbite, hypothermia, near drowning, sprains, fractures, motion sickness, and heat illness. Lacerations are relatively more common because of the use of knives to cut bait and fishing lines and to clean fish. These lacerations are often contaminated with a variety of marine and freshwater pathogens that may increase the incidence of wound infection. Thorough debridement of the wound and copious irrigation with sterile saline solution are the best initial methods to prevent infection.

Fishhook Injuries Fishhooks are designed to penetrate the skin of fish easily and to hold fast while the fish is played and landed. To perform this dual role, they are extremely sharp at the tip, have a barb just proximal to the tip, and are curved so that the more force applied to the hook, the deeper it penetrates. Fishhooks may be single or in clusters of two, three, or four to increase the chance of catching the fish. Some state fishing laws limit the number of hooks allowed on a single line when fishing for certain game fish to make it more sporting. Unfortunately, the greater the number of hooks on a lure or line means an increased chance of catching a fisherman. The most common fishhook punctures occur when fish are removed from hooks. The combination of sharp hooks, slippery fish, and an inexperienced fisherman leads to puncture wounds or embedded fishhooks. Many fishermen use commercial fishhook removers or large Kelly forceps to remove hooks. Some fishing guides simply cut the hook with a side-cutting pliers; they believe the remaining segment of hook will eventually oxidize in the victim and disintegrate. Often, fishhooks are stepped on with a bare foot or fishermen catch themselves or another person on the backcast. Fishhooks can penetrate skin, muscle, and bone, and they may pierce the eye or the penis. Care must be taken in removing a fishhook so that further damage to underlying structures is avoided. The first step is to remove the portion of the hook that is embedded from any attached lines, fish, bait, or lure. This is best done with a sharp side-cutting pliers. A bolt cutter may be needed for large, hardened hooks. A number of techniques are used for removing embedded fishhooks, but all involve a certain amount of movement of the hook, which causes increased pain. A local anesthetic should be infiltrated around the puncture site to minimize pain and movement of the patient. The following method can be used if the hook is not deeply embedded (Fig. 22-19E). Pressure is applied along the curve of the hook while the hook is pulled away from the point. Because the barb is on the inside of the curve of the hook, this enlarges the entrance hole enough to allow the barb and point to pass through. Sometimes a string looped through the curve of the hook facilitates the process. If the hook is deeply

A

B

D

C

E

Figure 22-19. A to D, Removal of a fishhook that has deeply penetrated a fingertip. E,“Pressand-yank” method of fishhook removal.

embedded, pressure can be applied along the curve of the hook until the point and barb penetrate the skin at another place, and then the barb can be cut off and the remainder of the hook backed out (Fig. 22-19A–D). Fishhooks embedded in the eye should be left in place, the eye covered with a metal patch or cup, and the victim referred to an ophthalmologist for further care. Rarely, hooks become embedded in bone or cartilage; this victim must be taken to the operating room to have the hook removed via a surgical incision.

Fishing Spear Injuries Fishing spears, like fishhooks, are designed to penetrate and hold fish. They may be jabbed, thrown, or propelled by rubber straps or carbon dioxide cartridges. The more force used to propel the spear, the deeper the penetration into tissue. Although arrows are designed to cause bleeding and bullets to cause crushing, fishing spears are designed to hold the fish until it drowns or is otherwise dispatched. Spears may penetrate the human chest or abdominal cavity, skull, or any other anatomic area. Some bleeding may occur, especially if major blood vessels are struck. The victim should be removed from the water as soon as possible and immediate attention given to airway, breathing, and bleeding control. The spear should be stabilized in place, and the victim immediately transported to a medical facility. Penetrating neck and chest injuries may require endotracheal intubation and tube thoracostomy. If a spear is embedded in the victim’s cheek and interferes with the his or her airway, cutting the spear off with a bolt cutter and removing it through the mouth is permitted. Spears in all other locations should be left in place, although they may be cut off to facilitate transportation or improve the victim’s comfort (Fig. 22-20).


UNEXPLODED ORDNANCE There are many areas in the world where unexploded ordnance can be found. Types of ordnance may include aerial bombs, rockets, artillery and mortar shells, grenades, and mines. Any area of the planet where a war has been fought within the past century or so has potential for harboring these items. Crews excavating streets in urban areas of England, France, and Germany often uncover unexploded ordnance from World War

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Main charge

Fire assembly adapter plug

Soft metal plate

Wire

Striker Retaining wall Detonator Detonator adapter plug

Delay-arming mechanism

A Figure 22-21. An example of an antipersonnel mine manufactured by the Soviet Union.

B Figure 22-20. A, Male patient with a multipronged fishing spear through the foot.He said he saw something move and he speared it. B, Same patient with the spear being cut off in the emergency department with a bolt cutter.The patient was taken to the operating room to have the remainder of the spear removed.

I or World War II. Many areas of the United States that have been used for bombing or artillery ranges are adjacent to wilderness regions and, although they are usually well marked as impact areas, still pose a risk for the unwary traveler. Many areas of the shallow ocean accessible to scuba divers have sunken munitions transports and warships that contain massive amounts of unexploded bombs, shells, and torpedoes. Another problem that has arisen is the use of mines and booby traps to protect marijuana and opium fields and illegal drug laboratories throughout the world. Currently, unexploded land mines represent a significant health problem in Southeast Asia, the Balkans, Central America,

Egypt, Iran, and Afghanistan. The International Red Cross estimates that someone is killed or injured by a land mine every 22 minutes. The average number of mines deployed per square mile in Bosnia is 152, in Iran 142, in Croatia 92, and in Egypt 59. There are a total of 23 million mines in Egypt alone.39 Land mines may be commercially manufactured or produced locally from available materials (Fig. 22-21). Commercial land mines currently produced in United States have a limited active life and self-destruct after their active life has expired. Unfortunately, this is not true of older types of mines or mines produced by other countries. Locally produced mines have no standard size, shape, or detonation pattern and may be very difficult to detect and defuse. These types of land mines are used extensively in El Salvador, Malaysia, and Guatemala. Land mines have two primary functions, the first of which is to cause casualties, the so-called antipersonnel mines. These may be blast or fragmentation type. The fragmentation type may be either directional or nondirectional (Fig. 22-22). Antipersonnel mines may cause lethal or nonlethal injuries in several persons. Wounded soldiers require more care than killed soldiers do, and the tactical effect may be the same. The second primary function is to destroy vehicles, such as tanks, so these mines are usually much larger. All mines have three basic components: (1) a triggering device, (2) a detonator, and (3) a main explosive charge. The triggering device differs depending on the type of mine. Blast mines usually involve a pressure-type trigger and occasionally are command detonated, especially for antitank purposes. Many antitank mines will not explode unless a pressure of 300 to 400 pounds (136 to 181 kg) is applied. The M14 blast antipersonnel mine needs only 20 to 30 pounds (9 to 14 kg) of pressure to trigger the detonation. Fragmentation mines are usually triggered by trip wires or similar “touch” devices. The M18A1 fragmentation mine, or “claymore” mine, is designed to be command detonated by an electronic trigger. Booby traps other than land mines may be mechanical, chemical, or explosive. During the Vietnam War, venomous snakes

Chapter 22: Hunting and Other Weapons Injuries

Figure 22-22. Above, A directional type mine used against unarmored vehicles or personnel. Below, An improvised mine, or booby trap, manufactured from a hand grenade and materials at hand.

were used, as well as the notorious sharpened bamboo spikes known as “punji” traps. The distribution of mines usually entails spreading them on the surface of the ground; by air along roads, railways, and defensive positions; or hiding them by burying or camouflage along trails or suspected routes of approach. Injuries from land mines depend on several factors: type of mine (blast vs. fragmentation), position on the ground, method of detonation, whether it explodes above the ground, position of the victim, environment, and type of soil. Four general patterns of injuries occur with land mines. Pattern A injuries occur with small blast mines, such as the U.S. M14 and the Chinese Type 72. These injuries usually involve only the leg below the knee. Complete or partial foot amputations are most common, and trunk or head injuries are rare. Pattern B injuries are caused by larger blast mines, such as the Russian PMN. These mines contain 4 to 6 times as much high explosive material, and the cone of explosion is much larger. The injuries seen with this type of land mine usually involve massive soft tissue injuries to both legs below and above the knee and commonly the pelvis, abdomen, and chest. Pattern C injuries are generally caused by Russian PFM-1, or “butterfly,” mines. These mines are usually distributed by air, and the wings are designed to help spread the mines. They are triggered by pressure applied to the wings; handling the mine commonly does this. Most of the injuries involve amputation of the hand at the wrist, but often the head, neck, and chest are injured also. Unfortunately, the loss of one or both eyes is not uncommon with this mine. Pattern D injuries are caused by fragmentation mines. These may be bounding mines, such as the U.S. M16 or the Russian OZM, or directional mines, such as the U.S. M18A1 or the Russian MON. They are

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designed to spread metallic fragments over a wide area at the height of a person’s waist. The fragments lose their energy much faster than a bullet projectile but at close range can be devastating. The lethal range is usually 82 to 164 feet (25 to 50 m), with casualties occurring out to 656 feet (200 m). The injuries are quite similar to gunshot wounds and are often multiple. Large, unexploded artillery shells or bombs may cause a combination of blast and fragment injuries but on a larger scale, sometimes involving scores of victims. Many military and civilian casualties are caused by improvised explosive devices (IEDs), which may be conventional explosives; improvised from fertilizer, propane, or other unconventional explosives; artillery, mortar or other ordnance; or explosive charges removed from said ordinance. The IEDs are commonly used by terrorist groups, which may detonate the devices either by timing mechanisms or by command, sometimes in suicidal attacks. These devices are usually detonated in crowded areas or near important political or military targets to create the greatest impact. Examples are attacks on the Oklahoma City Federal Building, the Beirut Marine barracks, and multiple incidents in Iraq. The treatment of these injuries can be very complex and involve vascular, orthopedic, soft tissue, abdominal, and craniofacial procedures. The wounds are usually highly contaminated with soil, clothing, and fragments that may be driven deep into tissue proximal to the obvious injuries.48 In most of these injuries, massive debridement is necessary. Rarely, unexploded ordnance may be imbedded in soft tissues and body cavities and must be removed in the operating room, possibly endangering the lives of medical personnel. Most victims who survive never completely regain normal function, especially if the initial treatment was delayed or inadequate. Postsurgical infection of mine injuries is common and greatly increases morbidity and mortality. Initial treatment involves airway control, treating tension pneumothorax, and controlling hemorrhage. Tourniquets are often necessary to control the bleeding from amputated limbs. Splinting the injured extremity and covering the wound to prevent further contamination is necessary. Initial debridement must be done carefully; removal of fragments may cause bleeding to recur. Penetrating injuries of the pelvis and abdomen usually require laparotomy, and soft tissue injuries may require multiple reconstructive procedures. Broad-spectrum antibiotics and tetanus prophylaxis are appropriate in all cases, and fluid resuscitation is usually indicated with extremity injuries. Blast injuries without fragmentation may cause tympanic membrane rupture, blast lung resulting from alveolar rupture, and intestinal rupture, although the latter is more common with underwater mine explosions. The mechanism is production of an overpressure wave that travels through tissue of various densities and causes tear injuries at membrane interfaces. These injuries must be suspected in any victim involved in a blast, whether from a land mine or other explosive device. Scuba divers and swimmers who are involved in underwater explosions may have more serious injuries because of the increased speed of sound in a liquid medium. This can cause more severe tearing of membranes at the fluid–air interface and additional trauma secondary to a “water hammer” effect and spalling. The position of the victim and the number of shock waves caused by reflection of the blast wave off of walls and ground may increase the amount of damage. Victims in contact with solid objects, such as the hull of a ship or vehicle, may have increased injuries because of increased velocity of the blast wave through solids. Burns and translational injuries, whereby

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the victim is thrown by the blast and has injuries similar to a fall or motor vehicle crash, also occur. Generally speaking, the closer the victim is to the blast, the greater the injury. The tympanic membrane will rupture at overpressures of 5 psi. This causes acute hearing loss, pain, and tinnitus. Blast lung is caused by the overpressure wave passing through the chest wall and may involve one or both lungs. Chest pain, dyspnea, and hemoptysis may present immediately or be delayed up to 48 hours. Chest x-ray may show patchy or diffuse infiltrates, pneumothorax, subcutaneous air, and hemothorax. Implosion of air into the vascular system may cause air embolism and sudden death. Abdominal injuries in air blast are uncommon but in water blast may present as abdominal pain, nausea, vomiting, and tenesmus. Sigmoid and transverse colon

23

injuries are most often seen, followed by small bowel and solid organ (such as liver and spleen) injuries from the water hammer effect. Abdominal injuries may have a delayed (up to several days) presentation. The key to therapy is to be suspicious of occult injuries in any victim of a blast, whatever the cause. Most injuries will present within the first hour; however, because injuries may be delayed in presentation, observation and close follow-up are critical. Treatment is generally supportive for ear and lung injuries and operative for abdominal injuries.3,5,10,11,14,21,23,25,26,30,31

The references for this chapter can be found on the accompanying DVD-ROM.

Tactical Medicine and Combat Casualty Care Lawrence E. Heiskell, Bohdan T. Olesnicky, and Lynn E. Welling

Tactical medicine can be defined as both emergent and nonemergent care provided to victims of illness or injury related to law enforcement or military operations, often in a hostile environment.56 Tactical medicine in the early years was often referred to as tactical emergency medical support (TEMS). The emergency medical services (EMS) and prehospital community called it tactical EMS, and the U.S. military coined the phrase combat casualty care. Numerous law enforcement agencies now have tactical medical teams composed of on-call physicians and prehospital care providers. Because many law enforcement agencies and branches of the U.S. military have embraced this concept, it is now commonly known as tactical medicine. Prior to 2001, there was a perception of professional separation between doctors in traditional medical practice and the tactical medicine physicians involved in law enforcement. This was probably related to what might be seen as competing priorities for physicians when dealing with sick or injured patients who are suspects in a police investigation. No other subspecialty in emergency medicine has experienced the growth rate of tactical medicine. In the past 15 years, more than 170 publications addressing tactical medicine issues have been written. Tactical medicine educational programs have trained thousands of emergency medical technicians (EMTs), paramedics, and physicians, who have responded to the call to provide on-scene emergency medical care to members of the law enforcement community or active duty military.51 Tactical medicine is very similar for both military and civilian tactical providers. Techniques, strategies, protocols, and equipment are

all virtually identical, with few differences. The military tactical medical provider must deal with long deployment times, therefore incurring a significant preventative medicine requirement. Although routine medical care and performance enhancement (e.g., conditioning, nutrition, rest) are important for both civilian and military tactical teams, they take on a longer-term function for the military tactical medicine provider. A civilian tactical operation typically takes hours to days. (The Waco and Ruby Ridge incidents were exceptions, more in concert with a military length of engagement). A typical tactical military operation may take days to months, and other aspects—disease and nonbattle injury—become as important as the tactical medical care (Table 23-1). Tactical medicine has been a mainstay of military operations since the beginning of modern warfare. The hospital corpsman, or combat medic, was deployed on the front lines with the warriors to provide basic medical care. This care was provided under fire, sometimes in the harsh environments of the jungle, the desert, high mountains, and underwater. As the science of medicine improved, the need to move higher levels of care further toward the forward edge of the battle area was recognized. Shock trauma platoons, manned by emergency physicians and support staff, were sent to the front lines to provide advanced resuscitative support. These units could be fully operational and seeing patients in less than 30 minutes. Mobile surgical teams and forward resuscitative surgical teams developed the technology to put trauma surgical teams within minutes of the location of a combat casualty. These teams are fully mobile

Chapter 23: Tactical Medicine and Combat Casualty Care

Figure 23-1. Forward resuscitative surgical team. (Courtesy Lynn Welling, MD.)

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Figure 23-2. Patient transport. (Courtesy Lynn Welling, MD.)

TABLE 23-1. Nonbattle Conditions Encountered by Tactical Medical Personnel (Spring 2003)* PRIMARY ICD-9 DISEASE CATEGORY Digestive Symptoms ill defined Mental disorders Musculoskeletal Genitourinary Nervous system sense organs Skin Supplemental Infectious and parasitic Circulatory Endocrine, nutritional Neoplasms Respiratory Pregnancy Congenital Total

n

% OF TOTAL

44 38 29 29 21 17 15 15 10 10 8 6 5 3 3 253

17.4 15.0 11.5 11.5 8.3 6.7 5.9 5.9 4.0 4.0 3.2 2.4 2.0 1.2 1.2 100.0

*Navy/Marines Operation Iraqi Freedom from 21 March to 15 May 2003. ICD, International Classification of Diseases.

Figure 23-3. A high-velocity gunshot wound. (Courtesy Lawrence E. Heiskell, MD.)

and are able to set up or dismantle in 30 minutes, utilize tent shelters or shelters of opportunity within which to perform operations, and provide life-saving damage control surgery to multiple patients under the extreme conditions of modern warfare (Fig. 23-1). Systems are designed so that staff can resuscitate, treat, and transport patients in extreme hot or cold temperatures, over rough terrain and hostile territory, while the patient is paralyzed and intubated, while wounds are still open, and while attempts are made to prevent the hypothermia, dehydration, and coagulopathy inherent in postsurgical patients (Fig. 23-2). Tactical medicine has advanced to anticipate and react to changes in combat strategy. In Operation Iraqi Freedom, the initial injury patterns were primarily high-velocity penetrating wounds—that is, mostly gunshot wounds (Fig. 23-3 and Table

23-2).30 As the war has progressed, the weapon of choice of the insurgents has become the improvised explosive device (IED) (Fig. 23-4).79 This weapon produces significantly more trauma, including shrapnel, blast, and thermal injuries. It has also required a change in protective body armor as the injury patterns have changed to include more devastating extremity and head-and-neck wounds than torso wounds (Fig. 23-5).29 The IED has also continued to cause problems with torso injuries, as the blast patterns cause shrapnel to angle up under traditional body armor and through arm openings. This has promoted development of armor that helps better protect these areas. The terrorist attacks of September 11, 2001, and events such as the 1999 Columbine High School shootings heightened our nation’s awareness of the real threats of terrorism and violence

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on U.S. soil and diminished some of the resistance to medical providers being actively and closely involved in law enforcement special operations.80 Today, hundreds of fire and EMS agencies provide tactical emergency medical support to federal, state, and local law enforcement special operations teams.

Law enforcement special operations, often referred to as SWAT (special weapons and tactics) teams, are intended to deal with a wide range of high-risk criminal problems and threats.69 These include, but are not limited to, hostage rescues, terrorist acts, barricaded suspects, violent and suicidal suspects, takeover bank robberies, high-risk warrant services, and active shooter situations.18,43,45 Patient advocacy, with priorities of ensuring the best possible quality of care and patient confidentiality, can be at cross purposes with a police officer trying to gather important facts in

TABLE 23-2. Battle Conditions Encountered by Tactical Medical Personnel (Spring 2003)* MECHANISM OF INJURY

n

% OF TOTAL

Gunshot wound Shrapnel/fragmentation RPG (handheld antitank grenadelauncher)/grenade Motor vehicle accident Fall Explosion Unknown/not recorded Landmine Blast Mechanical/machinery Other Multiple (NOS [not otherwise specified]) Blunt Debris Total

76 65 39

24.1 20.6 12.4

28 17 16 16 14 11 13 10 4

8.9 5.4 5.1 5.1 4.4 3.5 4.1 3.2 1.3

3 3 315

1.0 1.0 100.0

*Navy/Marines Operation Iraqi Freedom from 21 March to 15 May 2003; wounded in action.

Figure 23-4. An example of an improvised explosive device (IED):a hand grenade wired to the undercarriage of a vehicle. (Courtesy Lawrence E. Heiskell, MD.)

Figure 23-5. Anatomic location of injury (wounded in action [WIA] only). (Courtesy Naval Health Research Center.)

Chapter 23: Tactical Medicine and Combat Casualty Care an investigation to ensure public safety and justice. Tactical medicine must respect both patient rights and mission goals. SWAT teams are found in most midsize and larger law enforcement departments. In some areas, a number of small departments have banded together to form multi-jurisdictional or regional SWAT teams.16 Harsh environmental conditions, including what many regard as wilderness, will increasingly provide a backdrop for incidents requiring tactical efforts.


HISTORY OF COMBAT CASUALTY CARE

Much of the training and tactics of civilian SWAT teams are based on the experience of military special operations teams. Such military teams have their origins in the U.S. Office of Strategic Services and the British Special Air Service during World War II (WWII). Some of the earliest military special operations teams incorporated tactical medical components. German Fallschirmjäger (paratroopers) incorporated a wellorganized medical support team with physicians. Dr. Heinrich Neumann jumped with the unit during the invasion of the island of Crete in 1942.37 During the Normandy Invasion of June 6, 1944, at Pegasus Bridge on the Orne River, the British, led by Major R. J. Howard, landed with medical support accompanied by a physician, Captain J. Vaughan of the Royal Army Medical Corps.2 The U.S. Armed Forces during WWII also incorporated physicians in their assault on fortressed Europe. Dr. Robert Franco and Dr. Daniel B. McIlvoy both parachuted into Sicily with the 82nd Airborne Division in April 1943 and jumped into Normandy in June 1944.26 During the 1950s, the Army Special Forces (77th Special Forces Group) was formed. As U.S. special operations teams evolved, other specialized teams, such as DELTA, America’s elite counter-terrorist force, were formed.36 Each of these special operations units has a plan for tactical medical support. The growth of terrorism in the 1970s resulted in the formation of other special operations groups worldwide. The Germans established a special unit within their border police, later presented to the world as GSG9 (Grenzschutzgruppe-9).99 This unit emerged after the 1972 tragedy at the Olympic Village in Munich, Germany. The French formed the Groupe d’Intervention de la Gendarmerie Nationale in 1974, and many other countries have since developed similar units. Medical providers in the combat environment were traditionally taught to perform with the principles of ATLS (advanced trauma life support). Although this training was instrumental in decreasing the morbidity and mortality of trauma victims in the noncombat scenario, it fell short of providing appropriate care for the patient and the combatant team members on the field of battle. Numerous reviews of past and recent conflicts have noted the inadequacies of this approach to battlefield medical care.6,8,15,104 Ninety percent of battle deaths occur in the field, prior to any medical intervention. Bellamy did a landmark review of wounds and death in battle.7,73 In this study,7 he noted that 31% of battlefield deaths resulted from penetrating head injury, 25% from surgically uncorrectable torso trauma, 10% from potentially correctable torso trauma, 9% from exsanguinating extremity wounds, 7% from mutilating blast trauma, 5% from tension pneumothorax, 1% from airway obstruction, and 12% from various wounds (sepsis and shock off the battlefield) (Fig.

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23-6A). Potentially preventable battlefield causes of deaths include bleeding to death from extremity wounds, tension pneumothorax, and airway obstruction.54 These statistics have proven true in today’s Global War on Terrorism conflicts and in most tactical medical scenarios. They gave rise to questions about the pure application of the basic advanced life support precepts of airway, breathing, and circulation (ABC) for battlefield and tactical situations. In 1993, led by the Naval Special Warfare Command, a multi-agency working group (Committee on Tactical Combat Casualty Care), including special operations physicians, medics, corpsmen, and operators, began a 2-year study of this issue. This led to the guidelines titled Tactical Combat Casualty Care in Special Operations.15 The committee meets regularly and reviews new equipment, practices, and current operations for lessons learned, and then revises the guidelines as appropriate. These guidelines, which evolved from the special operations community, are currently being evaluated and implemented in most combatant units of the U.S. military, and of many other countries.14 The need for civilian SWAT teams in the United States evolved from high-profile criminal acts that resulted in shocking losses of human life. The seminal incident involved a sniper at the University of Texas at Austin. On August 1, 1966, Charles Whitman shot and killed 15 people and wounded 31 others.70 In the midst of this tragedy, it became apparent that the law enforcement agencies called out were ill equipped to deal with the threat, hampered by inadequate weaponry and not trained to respond in a timely and optimal fashion. After this incident, many law enforcement agencies began developing specially trained and equipped tactical units to respond rapidly to such threats to public safety.31 The Los Angeles Police Department and the Los Angeles County Sheriff’s Department were among the first law enforcement agencies in the United States to organize and develop full-time tactical units specifically trained to handle high-risk incidents. Before 1989, there existed great diversity in the ways emergency medical care was provided during law enforcement tactical operations. Early on, most law enforcement agencies relied on regular civilian EMS providers staged at a safe location removed from the area of operation, or they simply called 911. Although this took advantage of an already established prehospital care system, care for injured officers was delayed.103 Other agencies trained full-time SWAT officers as EMTs or paramedics. This concept of getting medical care “close to the fight” was also realized in the Gulf War, and the military put this new concept in place during Operation Iraqi Freedom. Information obtained from interviews with military emergency physicians who served in Iraq has suggested success of the new model of battlefield care.101


PRINCIPLES OF TACTICAL

COMBAT CASUALTY CARE

Tactical combat casualty care (TCCC) varies from ATLS in several distinct ways, primarily because the victim and the medical provider are not in a safe environment. Additionally, medical care of the victim may not be the highest priority, and the team may be hours from higher levels of care and operating in the open under extreme environmental conditions.

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A

Figure 23-6. A, How people die in ground combat.B, Intubation.(A courtesy Col.Ron Bellamy; B courtesy Lawrence E. Heiskell, MD.)

B The premise of TCCC is to do the right things at the right times. Underlying this basic statement is the suggestion that good hospital-based medicine is often not good battlefield medicine,14 as logically follows from these three statements: 1. Good medicine can be bad tactics. 2. Bad tactics can get everyone killed. 3. Bad tactics can cause the mission to fail. The ultimate goals of TCCC are the following: 1. Treat the casualty. 2. Prevent additional casualties. 3. Complete the mission. TCCC is divided into three main stages of care14: care under fire, tactical field care, and combat casualty evacuation care. These are defined in the following paragraphs.

Care under Fire Sometimes care is rendered by the medic or corpsman at the scene of the injury while he is still under effective hostile fire.

The medical equipment available is limited to what the individual operator or the corpsman or medic can carry in the medical pack. The most effective medical care during this stage of TCCC is fire superiority—that is, winning the battle, or at least keeping enemy heads down and weapons ineffective. The medical provider (and the casualty if able) must work to suppress hostile fire and eliminate the threat as directed by the mission commander, and, if possible, to protect the injured fighter from further harm. For many reasons, this is undoubtedly the most difficult phase of TCCC. First, the traditional provider, trained to be a “medic first,” may find it hard to direct attention to the threat and not maneuver to respond to the casualty. Second, this phase usually occurs in the most exposed environment, where the provider cannot use his normal assessment tools. For example, during nighttime he cannot use a light, as it would draw more fire, and listening for lung sounds with a stethoscope in an explosionrocked firefight is useless. In earlier conflicts, it was noted that

Chapter 23: Tactical Medicine and Combat Casualty Care

Figure 23-7. CATS (Combat Application Tourniquet System) tourniquet. (Courtesy Lawrence E. Heiskell, MD.)

many medics and corpsmen who responded to casualties instead of suppressing fire were wounded or killed, and that a significant number of the victims that they were trying to rescue were already dead. The priorities for the provider during this phase of care, therefore, are as follows14: 1. Return fire as directed or required. 2. Try to keep yourself from getting shot. 3. Try to keep the casualty from sustaining additional wounds. 4. Stop any life-threatening external hemorrhage with a tourniquet. 5. Take the casualty with you when you leave. Airway and breathing problems are not addressed during this phase. The key action is to stop exsanguinating hemorrhage. A tourniquet is the primary means to stop the bleeding on an extremity (Figs. 23-7 through 23-10). The tourniquet can be applied and left in place by the injured operator or medic, who can then return fire in support of the team. If a tourniquet cannot be placed because of the location of the wound, then direct pressure and a hemostatic dressing are recommended as the appropriate actions. As soon as possible, the casualty is moved to a safer location, and the next phase of TCCC is instituted. This movement is performed with techniques dictated by the tactical situation. It can be done by, for example, vehicles, pack animals, buddy lifts, or dragging. Another departure from traditional ATLS teaching is that cervical spine protection is not routinely provided in this phase of care. Studies of penetrating neck injuries in Vietnam demonstrated that only 1.4% of patients with penetrating injuries would have benefited from cervical spine immobilization.4 Although not all combat-related injuries are penetrating, the complexities of moving a patient in an environment where the patient and provider are under fire often preclude even rudimentary cervical spine immobilization.

Figure 23-8. Mechanical advantage tourniquet. (Courtesy Lawrence E. Heiskell, MD.)

Figure 23-9. Chitosan hemostatic dressing. (Courtesy Lawrence E. Heiskell, MD.)

Tactical Field Care The tactical field care phase consists of care rendered once the medic or corpsman and the casualty are no longer under effective hostile fire. It also applies to situations in which an injury has occurred on a mission but there has been no hostile fire. Available medical equipment is still limited to that carried into the field by mission personnel. Time prior to evacuation to a medical treatment facility may vary considerably. In this phase, the medic has a short time to evaluate and treat the wounded. The medic assesses injuries, performs medical

Figure 23-10. Emergency bandage. (Courtesy Lawrence E. Heiskell, MD.)

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care as able (equipment still limited to what was carried onto the battlefield), and then informs the mission commander of the findings. The mission commander then determines what action will be taken (evacuation, abort, continue). This again may be a major departure from nontactical medical care, in that the medical provider is not the ultimate authority on patient disposition. The mission commander decides how much time is taken to care for the casualty in any phase of the operation, if and when MedEvac will occur, and what assets will be allocated from the primary mission toward care of the injured. During this phase, the provider must assume not only that hostile fire may occur at any time but also that any injured team member with altered mental status may become a threat. The provider must therefore disarm the team member, an action that most warriors resist. This is the first step in the tactical field care phase. The second step is to address airway compromise. Airway actions are usually rendered as follows: if the victim is unconscious without obstruction, utilize a nasopharyngeal airway (better tolerated and less likely to become dislodged with movement)1 and a rescue position if able. If airway obstruction is present and cannot be alleviated with these maneuvers, the next recommended treatment is to move directly to a surgical cricothyrotomy. Endotracheal intubation is not recommended at this level of care for several reasons: (1) It requires the medic to carry onto the battlefield, equipment that has no other purpose, (2) the medic must practice regularly to maintain his skills, (3) success rates under austere conditions are believed to be significantly less than those done in a controlled or semicontrolled setting, and (4) the laryngoscope light may compromise team safety on the field.84,96,97 Emergency cricothyrotomy is the best option in this phase of TCCC. Because of distorted anatomy, it is the best way to protect the airway of a patient with maxillofacial wounds. Blood and tissue in the airway preclude visualization of the cords and make endotracheal intubation difficult or impossible.14,92 The third step is to treat breathing difficulties. Any severe progressive respiratory distress is assumed to be due to a tension pneumothorax (the number-two cause of preventable battlefield deaths). One cannot wait for the classic signs (which are unreliable at best and most often impossible to ascertain on the battlefield) of diminished breath sounds, hyperresonance, and tracheal deviation to make this diagnosis.76 Therefore, faced with victims in increasing respiratory distress and with unilateral penetrating chest trauma, the medic will go directly to a needle thoracostomy. This is the definitive procedure in this phase. A chest tube is not usually needed, it is difficult to perform on the battlefield, and it would only further complicate patient care, transportation, and mission completion.14 The fourth step is to readdress bleeding. The medic rapidly locates uncontrolled hemorrhage and any wounds where a tourniquet has been placed. If possible, a hemostatic dressing is placed; the tourniquet may be discontinued if the wound and tactical scenario permit. Even if the bleeding appears controlled, further “rough” evacuation may necessitate keeping a tourniquet in place to prevent rebleeding. Each action that the medic takes is designed to save life with minimal further care by the medic. For example, a medic who is holding pressure on a bleeding wound cannot return fire, take care of other casualties, or perform other procedures on this patient. The patient is not optimally prepared for transportation, which may consist of being thrown over someone’s back and carried out. Thus, a

tourniquet that would be a last-ditch effort in a noncombat environment becomes the method of choice in the tactical combat situation. Each operator in the field carries, and knows how to use, at least one tourniquet that can be self-applied. This allows the operator to self-administer life-saving bleeding control and then continue with the fight until treatment by the medic is possible. The fifth step is for the medic to determine whether an intravenous (IV) line or a saline lock is beneficial. The advantages would be that the patient could receive fluid resuscitation and IV antibiotics. Disadvantages include a probable delay in transportation, the additional equipment required (and the bulky apparatus that could become dislodged or tangled during evacuation), and difficulty in placing a line under austere tactical conditions. If an IV is deemed necessary but cannot be expeditiously placed, the intraosseous route is utilized. Several devices can be used to achieve this, including large-bore hypodermic needles, traditional intraosseous needles, and devices such as the FAST-1 (fast access for shock and trauma) and BIG (boneinjection gun), which quickly and accurately place the needle in the sternum or in another appropriate location. The medic’s sixth step is to determine whether fluid resuscitation is required. In general, if the patient is not in shock (the best indicators of shock in the field are altered mental status in the absence of head injury, and weak or absent pulses), then no IV fluids are necessary. If the patient is conscious, oral rehydration is permissible and preferred in many tactical scenarios. If the patient is in shock, the medic can give Hextend67 as a 500mL bolus and reassess after 30 minutes. If the victim is still in shock, the Hextend is repeated once. Usually, no more than 1000 mL of Hextend is given, and further efforts at resuscitation are determined by the tactical scenario. If the patient has a traumatic brain injury and is unconscious and pulseless, fluid resuscitation is given to restore the pulse. This protocol maximizes survivability of the patient and limits the amount of equipment necessary to be carried onto the battlefield. After exsanguinating hemorrhage, airway compromise, and breathing difficulties have been addressed, the seventh step in the tactical field care medical plan is to inspect and dress known wounds. The medic locates and appropriately treats wounds already identified but not yet treated because of tactical considerations and then proceeds with a quick but thorough headto-toe assessment for additional wounds. This is analogous to the secondary survey of ATLS, with a couple of notable exceptions. First, the patient is not exposed. This is because the patient may have to be moved quickly if the tactical situation changes, and because the patient must be kept warm and protected from further injury for a much longer time than in an urban setting. The medic often does this examination by feel in order to avoid using white light, to keep the victim’s body armor as intact as possible, and to avoid cutting off protective clothing that may be required during evacuation. Step eight is to assess for pain control. Analgesia is administered in this phase of care with the following considerations. If the victim is able to fight, non-narcotic preparations are used. These do not affect mental status, allowing the victim to remain armed and responsive. If the victim is unable to fight, morphine and promethazine, IV or intramuscular (IM), are given as needed. Step nine: If not already done, fractures are splinted and neurovascular status is rechecked. Step ten, the early administration of antibiotics for open combat wounds, significantly reduces the rate of infection.12

Chapter 23: Tactical Medicine and Combat Casualty Care Again, oral medication is preferred if the patient is conscious, and gatifloxacin has been shown to be highly effective and with minimal risks. Gatifloxacin is a broad-spectrum fluoroquinolone that is active against gram-positive and gram-negative microbes, aerobes, anaerobes, and fresh and salt water pathogens, is a once-a-day drug, and has a long shelf life. If the victim is unable to take oral medication or has significant abdominal trauma, IV/IM antibiotics are utilized, with cefotetan being the current drug of choice. In many units, the operators are given a “wound pack,” consisting of an antiinflammatory, acetaminophen, and gatifloxacin, and instructed to take the entire pack as soon as possible after being wounded. Step 11 in the tactical care medical plan is to continue to communicate with the victim, giving encouragement, explaining the care given, and giving updates on the tactical scenario if appropriate. Traumatic cardiac arrest is treated on the battlefield just as it is in the civilian setting. If the victim is pulseless, apneic, and has no sign of life, resuscitation is not attempted. After these measures have been taken, or if medical evacuation is now available, the last phase of TCCC, combat casualty evacuation care, is entered.

Combat Casualty Evacuation Care This phase of care is rendered once the casualty (and usually the rest of the mission personnel) has been picked up by an aircraft, land vehicle, or boat. Additional medical personnel and equipment that have been prestaged in these assets should be available at this stage of casualty management. The management plan aligns closely with that of the tactical field care phase, with the addition of more equipment and perhaps higher levels of medical providers. This phase is also the phase most similar to ATLS, although it may occur in the back of a moving conveyance and is still somewhat limited by available equipment and the tactical scenario. The basic medical plan for combat casualty evacuation care is as follows: 1. Airway management: Same as for tactical field care, with the addition of laryngeal mask airway (LMA)/Combitube/endotracheal intubation for definitive airway management prior to cricothyrotomy if the operators are trained and the patient can be intubated (e.g., has no midface injuries). Spinal immobilization is still not deemed necessary for casualties with penetrating trauma for the reasons stated earlier. 2. Breathing: Same initial considerations as for tactical field care. A chest tube can be placed if needle thoracostomy has produced no improvement in breathing, or if long transport is anticipated. Most combat casualties do not require oxygen, but its administration may be of benefit in the following situations: low oxygen saturation by pulse oximetry, injuries associated with impaired oxygenation, unconscious patient, and traumatic brain injury (to maintain oxygen saturation >90%). Sucking chest wounds should be treated with petroleum gauze applied during expiration, covering it with tape or a field dressing, placing the victim in the sitting position, and monitoring for development of a tension pneumothorax. Asherman seals are also ideal for quickly securing chest tubes and for sucking chest wounds. 3. Bleeding: Same as for tactical field care. 4. IV: Same as for tactical field care. 5. Fluid resuscitation: Same as for tactical field care, with blood and/or lactated Ringer’s solution possibly available.

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6. Monitoring, wound care, re-inspection for additional wounds, analgesia, reassessment of fractures, antibiotics: All the same as for tactical field care. The following scenario exemplifies the concepts of TCCC and the various phases of care. Consider a Special Forces team on a night mission. They jump from an aircraft at night into hostile territory. They are then to travel by foot over 4 miles of rocky, mountainous terrain to secure the objective, and then move to the shoreline for a waterborne extraction. On the initial jump, one of the operators sustains an open femur fracture. The medic and the team leader must consider (at a minimum) the following issues: • How to treat the injured member with the equipment they carried in (keeping in mind that a potentially long evacuation wait time precipitates the need to minimize injury, control pain, prevent infection, avoid shock, defend selves, and maintain concealment) • How or whether to continue the mission

Option 1. MedEvac the injured member, breaking operational security and calling for helicopter extraction. Option 2. Commandeering a local vehicle and driving to a pickup site, taking the patient to the planned extraction site, and continuing with the mission. Option 3. Aborting the mission and leaving the injured member and possibly some of the team behind to provide security until they return with help. Thus, a single injury throws a lot of variables into the mission commander’s decision tree. Preplanning for medical situations is essential, and the medical member of the team is essential in the planning and execution of the mission. A main precept of TCCC is to move the medical care from being the sole responsibility of the combat medic, to involve each operator and each level of leadership. Each fighter carries a tourniquet that can be self-placed. Each fighter is trained in basic combat lifesaving skills so that the effects of wounds can be minimized (within defined limits) and fire can be returned until the medic can arrive and perform the appropriate advanced medical care. Each leader, from the squad level up, is trained to evaluate medical concerns as an integral part of the mission execution and is able to decide when to abort the mission, when to continue, and when to alter the plan, based on the mission objective and the issues that the injured team member or members bring to the fight.


PRINCIPLES OF TACTICAL MEDICINE

The tactical environment presents unique challenges to law enforcement officers, and the same is true for personnel providing EMS in that environment. Tactical medical care providers must have an understanding of and consideration for law enforcement tactics and mission-specific objectives when planning and providing medical support (Fig. 23-11).55 Traditional EMS doctrine maintains that rescuer and scene safety are first priorities, and that patient care is a secondary concern.78 The nature of tactical operations requires that law enforcement officers and tactical medical personnel operate in unsecured environments and situations with significant potential for violence and injury (Fig. 23-12).74 Tactical scenes are

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Figure 23-11. Tactical medics placing a suspect under arrest during a tactical operation. (Courtesy Lawrence E. Heiskell, MD.)

Figure 23-12. At the International School of Tactical Medicine,law enforcement tactical medics train for high-risk vehicle assaults. (Courtesy Lawrence E. Heiskell, MD.)

rarely safe from the civilian standpoint, but tactical medical personnel are trained to conduct concise and limited medical evaluations and interventions in potentially threatening areas.85 What sets tactical EMS apart from standard EMS is the ability to render immediate care in an environment that may not be completely secured from threats (Fig. 23-13). When a SWAT team relies on traditional EMS to provide medical care and an operator or civilian is acutely injured during the mission, the EMS unit must wait until either the victim is brought out to the safe (“cold”) zone (Fig. 23-14) or for the entire scene to be secured by law enforcement before moving to the patient. When a tactical medical unit is present, care can generally be rendered to the victim in a timely manner, and when the injuries involve acute airway issues or life-threatening hemorrhage, lives may be saved by faster access to care.

Figure 23-13. Advanced airway management in the tactical environment.(Courtesy Lawrence E. Heiskell, MD.)

Other differences between tactical EMS and conventional EMS include limitations in medical equipment at hand, performing in adverse or austere environments (e.g., while maintaining light or sound discipline), and performing patient assessment from remote locations.90 “Medicine across the barricade” involves remote evaluation and management of patients, such as when a hostage has become ill or injured and the provider attempts to assist the victim by using the eyes, ears, and hands of someone closer to the situation.35 The tactical medical provider must use skills not unlike those of an EMS dispatcher handling an emergency over the radio. In addition, standard EMS medical care performed in specific clinical scenarios may require a different approach when the same situation is encountered under tactical conditions.34 Tactical medicine can be provided by EMTs, paramedics, registered nurses, mid-level providers (physician assistants, nurse practitioners), or physicians who serve on police tactical teams.47 Mid-level providers and physicians traditionally have training in advanced surgical and medical procedures beyond what is normally allowed for traditional EMS personnel.22 The primary goal of tactical medicine is to assist a tactical team in accomplishing its mission. This is achieved through team health management—keeping the tactical team members healthy before, during, and after operations.21,62 A full tactical medicine program encompasses the provision of preventive and acute medical and dental care, and for some teams even canine support veterinary care.50 Ready access to such care has a positive effect on team morale. One of the most important roles of the provider is to create a formal medical threat assessment for each training and operational deployment. This includes consideration of issues such as environmental conditions (heat, cold, wind) (Fig. 23-15),41,42 fatigue (and the possible need for rotating operators), nutritional issues,23 plant and animal threats, and a plan for extrication and transport of patients.11 When operational, this medical plan should include any medical intelligence that can be gathered prior to or during the mission, including issues such as who is involved, ages of those involved, medical history and

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Figure 23-14. The zones-of-care concept of tactical emergency medical services. (Courtesy Bohdan T. Olesnicky, MD.)

Figure 23-15. Tactical operators overcome with heat exhaustion receive cooling measures from a tactical physician. (Courtesy Lawrence E. Heiskell, MD.)

background, preexisting medical conditions, geographic location, and even the weather.20 SWAT teams and their tactical medical teams are important community resources not only for their response to major emergencies (e.g., weapons of mass destruction) but also in planning for them. Tactical medical operators, in conjunction with local medical control, EMS, and public health officials, should take a leadership role to ensure that aggressive, proactive planning

for these future threats is completed before the resources are needed.17,105 Although no one doubts that some terrorists, outlaw states, and even organized criminals have the capability to produce or access chemical and biological agents, the question is whether they will use them.39 The use of explosive devices is on the rise worldwide. The potential for terrorist acts against the United States is immeasurable. As a result, domestic preparedness and proper training for blast injuries is essential.27,32,38,75,98 It is advantageous to have more than one provider as a part of a tactical team. In the event of a serious injury or when multiple casualties are involved (e.g., in a raid on a clandestine drug laboratory),48,61 one of the team’s responsibilities is to lessen the agency’s liability exposure with adequate written, photographic, diagrammatic, or video documentation.66 Another benefit of having multiple providers is the ability to send a provider to the hospital with an officer who becomes ill or injured during a mission. This provider can serve as a concerned advocate for the officer and as a go-between with hospital personnel, which provides significant reassurance to the entire tactical team.44,46,71

Team Health Management Tactical medical providers ensure that everyone on the team is healthy and optimally fit for duty.49 The team’s medical officer is responsible for the team’s physical fitness, diet, exercise, sleep, stress management, and preventive medicine. The tactical unit can be viewed as a group of elite operators who are “occupational athletes.” Strength training for many tactical operators consists of traditional bodybuilding exercises. However, this type of physical conditioning does not duplicate the actions needed to perform as a tactical operator. A SWAT team member never does a bench press on a tactical entry. Tactical operators, like professional

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athletes, need a broad-based program of training and physical conditioning tailored to the specific actions they will perform. The team’s medical officer should stress regular physical conditioning. A comprehensive plan of proper nutrition and exercise must be established and maintained. This should include a balance of aerobic and anaerobic exercises and stretching. Cardiovascular fitness workouts, such as running or swimming, are excellent for the tactical team. Full-body or resistance circuit weight training is excellent for strength training, but it must be a total body workout. Training some parts of the body but ignoring others can lead to costly injuries and a lower level of fitness than desirable.93 Flexibility training is one of the best ways to prevent injuries in the field. Unfortunately, it is frequently ignored. Regular stretching or yoga has been long recognized as beneficial in athletic physical conditioning. In this respect, the tactical unit is no different from any other group of athletes. When the physical conditioning program encompasses all these points, the team operates at its peak potential with fewer injuries. A sound diet should be stressed and maintained, but diet is often a controversial topic. In response to the obesity problem in the United States, the Food and Drug Administration (FDA) and many other researchers have looked at diets worldwide and their effects on the human body. Randomized clinical trials studying the risks and benefits of various individual diets are only recent works.10,28,83,102 The FDA studied the traditional food pyramid (based on four food groups and no longer considered a valid nutritional program72), and Mediterranean, high-carbohydrate, high-fat, high-protein, low-fat, lowcarbohydrate, Atkins, Zone, Weight Watchers, Ornish, and South Beach diets.25 They revised their food pyramid to a more balanced program designed for variations in age, sex, and level of physical activity, and containing five food groups: grains, vegetables, fruits, milk, and meat and beans. Fats, sugars, sodium, and total caloric intake are restricted. The FDA has an interactive website for the new food pyramid (www.foodpyramid.gov). Although our knowledge of diet and exercise is improved, data continue to be gathered, and the perfect dietary program for the tactical operator is not yet known. Nonetheless, fast foods and simple sugars should be deemphasized or eliminated from the tactical operator’s diet. The team medical officer essentially becomes the family physician for the tactical unit and should be prepared for this role. Regardless of the level of training, the team physician will be viewed as the medical advisor to the tactical unit. It is this relationship that fosters better team health overall, and better performance of the unit as a result. Preventive medicine should be stressed with regular physical examinations and treatment where appropriate. Smoking cessation, alcohol and drug counseling, and stress management are the responsibility of the team medical officer.

A

B Figure 23-16. A, Blackhawk Products Group Special Operations medical backpack. B, Ballistic vest,level IIIa,showing trauma plate worn for tactical operations.(Courtesy Lawrence E.Heiskell, MD.)

Tactical Medical Equipment In general, tactical EMS equipment comes from other areas of emergency medicine and law enforcement and is combined into field-expedient, multifunction toolkits. Looking at the gear as a whole, a modular approach may be most helpful (Fig. 23-16A). The gear differs depending on the roles of the providers and the tactical unit.33 Basic equipment for the operator includes essential items. Typically, an operator has a duty uniform consisting of a battle dress uniform or jumpsuit.95 The uniform may undergo appropriate modifications depending on weather con-

ditions. As with other areas of outdoor activity, it is wise to use a system of appropriate layers that can be easily adjusted to changing weather conditions. Waterproof and breathable outer layers may be a consideration, as are wicking underlayers. In addition to the standard duty uniform, a Nomex balaclava and gloves are worn to protect from exposure to pyrotechnic devices on many entries. Because this is an environment where gunfire may be encountered, ballistic protection is needed. For the tactical medical

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TABLE 23-3. U.S. Department of Justice Rating of Body Armor TEST VARIABLES

ARMOR TYPE I

TEST ROUND

TEST AMMUNITION

1

38 Special RN Lead 22 LRHV Lead 357 Magnum JSP 9 mm FMJ 357 Magnum JSP 9 mm FMJ 44 Magnum Lead SWC Gas Checked 9 mm FMJ 7.62 mm (308 Winchester) FMJ 30–06 AP *

2 II-A

1 2

II

1 2

III-A

1 2

III

—

IV

—

Special requirement

—

PERFORMANCE REQUIREMENTS REQUIRED FAIR HITS PER ARMOR PART AT 0° ANGLE OF INCIDENCE

NOMINAL BULLET MASS

MINIMUM REQUIRED BULLET VELOCITY

10.2 g 158 gr 2.6 g 40 gr 10.2 g 158 gr 8.0 g 124 gr 10.2 g 158 gr 8.0 g 124 gr 15.55 g 240 gr

259 m/sec (850 ft/sec) 320 m/sec (1050 ft/sec) 381 m/sec (1250 ft/sec) 332 m/sec (1090 ft/sec) 425 m/sec (1395 ft/sec) 358 m/sec (1175 ft/sec) 426 m/sec (1400 ft/sec)

8.0 g 124 gr 9.7 g 150 gr

426 m/sec (1400 ft/sec) 838 m/sec (2750 ft/sec)

4

10.8 g 166 gr *

868 m/sec (2850 ft/sec) *

1

4 4 4 4 4 4 4

6

*

MAXIMUM DEPTH OF DEFORMATION

REQUIRED FAIR HITS PER ARMOR PART AT 30° ANGLE OF INCIDENCE

44 mm (1.73 in) 44 mm (1.73 in) 44 mm (1.73 in) 44 mm (1.73 in) 44 mm (1.73 in) 44 mm (1.73 in) 44 mm (1.73 in)

2 2 2 2 2 2 2

44 mm (1.73 in) 44 mm (1.73 in)

2

44 mm (1.73 in) 44 mm (1.73 in)

0

0

*

*See section 2.2.7 of reference. g, grams; gr, grains. From U.S. Department of Justice National Institute of Justice: Ballistic Resistance of Police Body Armor. NIJ Standard 0101.03; 5.2.1, April 1987.

provider, levels I and IIa are not advised. Level II is the bare minimum if the body armor is concealed under a shirt or uniform, but levels IIIa to IV are better (Table 23-3, and see Figure 23-16B). These levels of protection have a good balance of bullet stopping power and ability to absorb blunt trauma. Many tactical operators combine body armor with ballistic plates made of metal or ceramic, which stop high-velocity rifle bullets. Body armor is chosen by the agency from a vast array of different types and styles produced by a host of manufacturers. Some tactical physicians also carry a Kevlar blanket or ballistic shield, which can be used to cover a patient in harm’s way or can be used as a mobile source of cover when providing care or extracting a downed victim. These blankets, although effective, are extremely heavy and bulky. The weight and bulk of all nonmedical tactical equipment hinders the ability to carry large amounts of additional material. The medic needs to decide how much can be carried and whether to wear a backpack or a load-bearing vest, or neither. In general, the tactical medical provider must be able to effectively carry equipment and operate in a tactical situation without hindering the rest of the team. Of the two general sets of medical equipment, one is carried for immediate care, typi-

cally worn in a small backpack or load-bearing vest, and the second is carried in a larger backpack or duffel bag in the support vehicle. The latter is used for more extensive treatment, multiple casualties, and prolonged transports.59

Communication Communication between team members and members outside the area of the operation is often essential. Radios with throat microphones and headsets are fairly standard on most tactical units. Radios tend to be on secure channels to ensure the security of a mission. Some communications may even be encrypted. Simple communication between members may involve standard or specialized sign language.

Entry and Breaching Tools Specialized entry tools are used to gain access to barricaded subjects or closed doors. Typical items, familiar to firefighters and EMS personnel, include pry bars, battering rams, sledge hammers, hooks on chains or rope, stop blocks, and halligan tools (Fig. 23-17). Ladders may be needed to gain access to an elevated or depressed point. In extreme cases, a variety of explo-

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Figure 23-17. Entry tools: two rakes, a halligan tool, a ram, and a sledge hammer are shown. (Courtesy Bohdan T. Olesnicky, MD.)

sive devices are available to trained explosive experts in the tactical unit to gain entry to an area.

Figure 23-18. At the International School of Tactical Medicine, law enforcement tactical medics train with the HK MP5 submachine gun. (Courtesy Lawrence E. Heiskell, MD.)

Weapons Systems Whether a team medic should be a sworn law enforcement officer or an armed civilian has been a subject of much debate. Regardless, a provider must be familiar with the unit’s weapons systems. For offensive or defensive purposes, weapons systems are constantly encountered in the tactical arena. A provider who is a sworn officer has a primary role as an operator on the unit and a secondary role as a medical provider.77,81 However, a provider who is first a medical officer would still have to protect himself in a hostile situation and therefore would be armed defensively. In another scenario, the provider may be unarmed but may have to take charge of an officer’s weapon in a medical or tactical situation. An armed officer who is disoriented may become a danger to the team, so the provider would need to take charge of all of the officer’s weapons and render them safe. In the worst case, the provider may have to defend a downed officer using the officer’s weapon. Weapons system familiarity is paramount for the tactical medicine provider. A provider should be familiar with every handgun, shotgun, rifle, submachine gun, assault rifle, and smoke or chemical agent gun used by the team. All tactical team members, whether providers or not, should be able to use any weapon a team member carries and render it safe.91 The provider should not be exempt from this requirement (Fig. 23-18). Different weapons systems use different ammunitions (see Chapter 22). Typically, there is a duty handgun, which shoots low-velocity handgun ammunition. This same ammunition may be used by a submachine gun, such as the Heckler and Koch (HK) MP5 UMP 40, or UMP 45. Calibers of the handgun and submachine gun should be matched to avoid the wrong caliber ammunition going into the wrong weapon, causing malfunction in a crisis situation. Assault rifles, such as the Colt AR 15 or Colt M16, shoot .223-caliber high-velocity cartridges. The provider may be exposed to shotgun ammunition, typically 00 buckshot. The team may have a sniper, who shoots with a .308 high-velocity

rifle that is bolt action for precision shots. The flight characteristics and ballistics of shotgun, rifle, and handgun ammunition vary depending on the weight, shape, and velocity of the ammunition. The provider should be familiar with the effects in order to treat field wounds appropriately. In addition to traditional ammunition, the provider may be faced with the use of distraction devices, chemical munitions, and less lethal munitions. Chemical munitions deliver a chemical agent to an intended target to disorient or incapacitate and facilitate capture or surrender without loss of life. Typical chemical agents used in tactical operations are tear gas or a derivative of pepper spray. Less lethal munitions are also fired to incapacitate and facilitate capture. Unfortunately, with this use of force, injury is common, so the provider should be familiar with the injuries and their treatments. These munitions are low-velocity projectiles of wood, hard rubber, foam rubber, plastic, or bean bags. They have enough force to cause pain and usually make an assailant stop aggressive action on contact. They usually cause minor blunt trauma, but they may achieve enough force and velocity to penetrate into body cavities, causing penetrating injures (Figs. 23-19 through 23-21). Explosive breaching techniques and distraction devices, such as “flash-bangs,” are often deployed during tactical operations. The small explosives used to gain entry into an area can create injuries that the medic must be prepared to recognize and to treat effectively.68 For example, the flash-bang is a device that is hand thrown into an area to deliberately disorient a suspect and divert attention toward the device and away from the entry team. These devices usually have a nonexploding canister and a small explosive charge. The device is activated and thrown much like a military hand grenade, but it causes a brilliant flash of light (6 to 8 million candlepower) and a thunderous noise (175 decibels). This is accomplished by venting explosive gases through multiple holes in the canister (Fig. 23-22). Medical problems caused by flash-bangs and explosive entries include the following:

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• Burns, both minor and major • Smoke causing bronchospasm • Vestibular dysfunction • Transient visual disorientation • Emotional upset and anxiety Of note, in general use, the flash-bang has not been reported to cause ear drum rupture. Explosive breaching is the role of the team’s explosives expert, with whom the medic should consult, as part of the medical threat assessment, about the types of explosives planned and the blast forces that may be encountered.

Vision Figure 23-19. A 37-mm less-lethal munitions launcher. (Courtesy Lawrence E. Heiskell, MD.)

Covert operations and low-light situations dictate the use of visual adjuncts. Binoculars, tactical mirrors, spotlights, periscopes, strobe lights, chemical lights, and headlamps are often deployed in a low-light tactical environment (Fig. 23-23). Proper training and discipline are required for use of these devices in the tactical environment, as they may give away one’s position and alert a hostile opponent to the team’s position. Similarly, electronic night vision equipment, which operates outside of the range of visible light, is also extensively used.


MEDICAL PERSONAL

PROTECTIVE EQUIPMENT

Universal precautions against infectious diseases must be deployed; tactical medicine is no different from any other venue in this respect. Medical personal protective equipment (PPE) includes masks, eye protection, gloves, and perhaps gowns. In remote locations, surgical treatment may be provided prior to transport to a tertiary care center. The basics for protection should be carried on the provider’s person in a readily accessible location. Some don surgical gloves underneath their shooting gloves prior to an operation so they will be ready if the need arises. Although not sterile, they provide protection from blood and body fluid–borne pathogens.

Personal Supply Module To reduce the amount of equipment carried by the medic and to help team members help themselves, each member of the tactical unit should carry a personal supply module (PSM), or “self-help kit,” with medical supplies. A team member can thus provide self-help or aid another member, and the medic may not have to be summoned until the scene is more secure. A typical PSM should be vacuum sealed and contain supplies for basic trauma care and for IV access (Table 23-4 and Fig. 23-24). Vacuum sealing these contents provides protection from the elements and makes them last longer. It also cuts down greatly on bulk, but it adds some weight.

Basic Medical Module

Figure 23-20. The stinger grenade has a small explosive charge that disperses many small rubber balls in a spherical blast pattern, causing compliance through pain. (Courtesy Lawrence E. Heiskell, MD.)

In addition to a PSM, a basic medical module (BMM) should be carried by team medics. Because every team member in a tactical unit should have at least basic EMT certification, a BMM could be used by any team member to provide initial care to a victim. The BMM should have basic splinting material and dressing material (Table 23-5). Basic airway tools, such as nasal airways and pocket mask, should be included. A bag-valve-mask or a more compact alternative is advisable in the tactical environment. A simple bagvalve-mask alternative device (BVMAD) can be constructed out

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Figure 23-21. Target areas for direct-fire or skipfire less-lethal projectiles. The orange areas are nontargets, the green areas are preferred targets, and the yellow areas should be targeted with caution only. (Courtesy Armor Holdings, Inc.)

Figure 23-23. A Surefire headlamp setup can use white light or LED light in low-light tactical situations. (Courtesy Lawrence E. Heiskell, MD.)

Figure 23-22. The Def Tec 25 flash-bang device. (Courtesy Lawrence E. Heiskell, MD.)

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Figure 23-24. Saline bullets remove the most common injury: foreign bodies in the eyes. (Courtesy Bohdan T. Olesnicky, MD.) Figure 23-25. The bag-valve-mask alternative device (BVMAD) as it is stored,with the mouthpiece (red arrow) over the exhaust port. (Courtesy Bohdan T. Olesnicky, MD.)

TABLE 23-4. Sample Contents of Personal Supply Module (PSM) Trauma dressing IV start kit Minor dressings Saline bullets

Medicines

Other wound items

Bandages such as the Israeli bandage can be easily self-administered by the victim on most extremity wounds. 100 mL IV fluid, an alcohol wipe, tourniquet, IV catheter (3), IV tubing, tape, flush and saline lock Adhesive bandages should be carried by all team members. Foreign bodies in the eyes are very common on entries, and a bottle of eye drops (saline bullets) may allow an operator to continue on a mission (see Figure 23-24). Pain: acetaminophen, ibuprofen, narcotic analgesics Antibiotics: ciprofloxacin, metronidazole, cephalexin Surgical staples or liquid tissue adhesive

TABLE 23-5. Sample Contents of Basic Medical Module (BMM) Splints Airway Litter Wound care Other

Two SAM splints Pocket mask, bag-valve-mask (BVM) or BVM alternative device, oral and nasal airways Fold-up stretcher Various trauma dressings Elastic (ACE) wraps and cravats

of respiratory supplies from a one-way valve, flexible tubing, and a mouthpiece (Fig. 23-25).5 This is the preferred ventilatory device in the tactical environment, as it allows a rescuer to provide ventilation without unnecessary bulk. Oxygen is rarely useful in the immediate tactical environment, so O2 cylinders are left in the support vehicle with a regular bag-valve-mask and retrieved when necessary. An automated external defibrillator (AED) should be carried in the support vehicle.3 A small collapsible litter for extrication of a downed person should be a part of every BMM.

Intermediate Medical Module An intermediate medical module (IMM) is intended to be used by paramedics and registered nurses. Unlike the BMM, it con-

TABLE 23-6. Sample Contents of Intermediate Medical Module (IMM) Airway Medications

Endotracheal tubes, laryngoscope, stylette, bougie, bag-valve-mask alternative device (BVMAD) IV setup and tubing, pain medication, rapid sequence intubation medications, antibiotics (see Figures 23-26 and 23-27)

tains equipment and supplies suitable for advanced life support (ALS). Under standing orders from a team physician, ALS providers may provide advanced cardiac life support to a victim. An IMM is much more extensive than a BMM. It contains medications, IV tubing, IV fluids, an endotracheal tube, a Combitube, a laryngoscope, a light wand, and, if protocol allows, a cricothyrotomy kit (Table 23-6 and Figs. 23-26 and 23-27). These facilitate placement of a definitive airway prior to transport, which, when used with a BVMAD, permits hands-free ventilation of a patient, allowing extrication by one or two team members. Proficiency with the airway toolkit is of high priority, as conditions in the tactical environment are difficult at best.

Advanced Medical Module The most complex module is the advanced medical module (AMM), intended for independent practitioners, such as nurse practitioners, physician assistants, and physicians. These practitioners can perform advanced surgical procedures and medical interventions that can make the difference between life and death on a long transport. Transport to definitive care should not be delayed unless medically necessary. However, if advanced care in the field is indicated, it can be provided by an independent practitioner with an AMM.

Major Trauma Module Lengthy surgical interventions in the field are not advised and have extremely poor prognoses. Although rapid transport to a trauma center should not be delayed, some surgical procedures may be of benefit when performed in the field: laceration repair to stop bleeding or facilitate evacuation, cricothyrotomy, and,

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Figure 23-28. A vacuum-sealed minor-surgery tray. Many procedures can be accomplished with a minimum of equipment. (Courtesy Bohdan T. Olesnicky, MD.)

TABLE 23-7. Sample Contents of Major Trauma Module (MTM) Figure 23-26. Vacuum-sealed intravenous start kit. (Courtesy Bohdan T. Olesnicky, MD.)

Israeli dressing Combine dressings Gauze pads Antibiotic packs Tourniquet

Figure 23-27. A well-stocked and functional intermediate medical module (IMM) airway kit, containing a laryngoscope, a bag-valve-mask alternative device (BVMAD), oral airways, a bougie, a stylette, endotracheal tubes, tape, and a surgical airway kit. (Courtesy Bohdan T. Olesnicky, MD.)

Wound closures Minor-surgery tray ACE wraps Splinting material IV fluids

Supplies

in critical situations, chest tube insertion. These types of procedures can usually be performed using only the essential equipment found in a vacuum-sealed minor-surgery tray (Fig. 23-28), which can be one component of the major trauma module (MTM) for advanced providers (Table 23-7). Many users include hemostatic dressings in trauma kits, but their use is not yet well studied.60,86 The efficacy versus the potential harm of hemostatic dressings is a subject of debate. Direct pressure with a sterile dressing is the initial approach to hemorrhage control. The traditional and time-tested approaches of pressure-point compression and tourniquets are useful adjuncts to any bleeding problem, so these materials should be included in the MTM. A set of combine dressings, gauze, petrolatum gauze, and Israeli dressings should also be carried.

Other

May be self-administered by the patient with one hand; combines an ACE wrap, combine dressing, and tourniquet in one device To control heavy bleeding or cover eviscerated bowel and open fractures Multiple uses Pre-prepared medication packs for major trauma, containing pain medication and antibiotics Several excellent devices are available for tactical use Sutures, staples, and wound adhesives For performing surgical procedures that cannot wait for extrication or transport Strains, sprains, and fractures are common SAM splint or a short sealed roll of fiberglass casting material. Bullet wounds frequently fracture long bones For infusion of medication and management of shock as needed. Also used for wound irrigation and eye irrigation. Several IV start kits should also be on hand Gloves, tape, trauma shears, tweezers, adhesive bandages, roll gauze, cravats, nasal airways, 60-mL syringes, headlamp Duct tape, biohazard bags, medical record sheets, and trauma tags for multiple casualties

Support Vehicle Module Additional supplies and equipment are kept in the support vehicle module (SVM). Consumable items should be kept in the SVM, so that other modules can be restocked from it (Table 23-8). The SVM contains equipment such as O2 cylinders, an AED, airway adjunct devices, fiberoptic scopes, nebulizers, surgical trays, chest tubes, cervical collars, backboards, peroxide, povidone-iodine, liter bags of crystalloid IV fluid, replacement filters for gas masks, and fiberglass splinting material.

Chapter 23: Tactical Medicine and Combat Casualty Care

TABLE 23-8. Sample Contents of Support Vehicle Module (SVM) Biohazard container Saline eye flush Elastic (ACE) wraps Splinting material

IV fluids

Ice packs

Wound dressings Advanced airway tools Spare uniforms

Oxygen cylinders Bag-valve-mask (BVM) Automated external defibrillator (AED)

Disposal container for used sharps and medical waste Foreign bodies in the eyes are common on entries Strains, sprains, and fractures are common Fairly bulky and difficult to carry in the medical pack. C-collars are frequently kept here and may be retrieved when needed For prolonged transport or massive hemorrhage, more IV fluid should be kept in the SVM and not carried on entries. Multiple IV start packs for use when necessary Ice packs are commonly used, as ice is not always available in the field. If the location has a freezer, bags should be kept to use existing ice Additional adhesive bandages, Israeli dressings, combine dressings, ABD pads, and burn dressings Difficult-airway tools may be needed in the cold zone prior to transport, to secure a definitive airway If decontamination is needed, the victim will need to be reclothed in a clean, dry uniform, particularly in cold or wet environments Best left in the support vehicle because of their weight Replaces the BVM alternative device when hooked up to oxygen in the cold zone The AED is proven to save lives but is too bulky to carry on entry

Field care is limited only by the equipment that can be transported and the training of the providers. Items carried by advanced providers include the following: • Central line • Tracheotomy set • Retrograde intubation set • Laryngeal mask airway • Chest tube set • Fiberoptic intubation set • Blood products or blood substitutes

CBRN Specialty Modules Depending on the role of the tactical unit, chemical, biologic, radiologic, or nuclear (CBRN) threats may be encountered. These incidents require tactical emergency medical care because they involve large crime scenes with casualties. Individuals trained in tactical emergency medicine are much more familiar with evidence collection and preservation, and they usually already have necessary security clearance to enter such an area. Until the scene is cleared, the tactical physician may be the only one who can provide medical care to victims inside. The chemical and biologic environments are specialized depending on the agent released. Various civilian and military protective gear and respirators or supplied air sources may need

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to be worn. Operating in CBRN protective gear requires extensive training in addition to regular tactical training. Antibiotic prophylaxis with ciprofloxacin, as well as agent detection equipment, may be carried by the medic in this case. Several biologic and chemical diagnostic kits and meters are available but costly. Radiologic incidents involve the dispersal of a radiologic agent with conventional explosives, the combination often referred to as a dirty bomb. Nuclear detonations refer to the splitting of a radioisotope and the resultant massive energy release from a nuclear bomb. Geiger counters are available for radiologic and nuclear situations. These situations require a great deal of additional training, but they are not beyond the realm of tactical emergency medicine. Hazardous material (hazmat) situations are frequently seen in civilian law enforcement raids on clandestine drug laboratories. Level A, B, or C protective suits with gas masks or supplied air may be required in these situations as well. Hazmat and CBRN situations are highly specialized in their nature and require extensive training, beyond the scope of this text.

Medical Threat Assessment Any mission planning must include a medical threat assessment (MTA). The SWAT commander uses information from many sources to create a tactical plan prior to execution of a mission, including the manpower available, building layouts, street layouts, support equipment needed, nature of the mission, available weaponry, and various sources of intelligence.65 An MTA is an important component of the intelligence the commander needs to properly execute the mission. It is the responsibility of the tactical medic to provide a concise and accurate medical briefing to the commander. MTA forms should be used on every mission to ensure systematic planning, as scenarios and problems may be unique. Only a systematic approach ensures complete assessment of the situation. The tactical medical team and its MTA are key factors in dealing with apocalyptic terrorist events, such as the Columbine school shootings and the school hostage crisis in Beslan, Russia.87 Other venues, such as protection details and the war on drugs, rely heavily on a team’s internal capacity for medical care, as evidenced by the U.S. Marshals Service Judicial Protection Training Program.88 A complete threat assessment should include these elements: 1. Location of the operation, with a brief description of the goals of the mission and the other teams involved, with their needs and resources (Table 23-9). 2. Locations of all surrounding hospitals and medical care facilities, such as designated burn and trauma centers, with phone numbers to facilitate communication. Local EMS numbers should be listed. 3. Helicopter flight plan. Before the mission, it should be ascertained that a helicopter is available and that there is an acceptable landing zone (LZ) for day or night conditions. This should include the exact global positioning system (GPS) coordinates of the LZ. Obstructions and debris should be cleared prior to the mission (Table 23-10 and Fig. 23-29). 4. Weather. Factors to be evaluated include temperature, rain, wind, humidity, wet-bulb temperature (TW), and windchill. Sunrise and sunset times should be recorded and logged. The TW is the lowest temperature to which air can be cooled by the evaporation of water into the air at a constant pressure, so it reflects the limit to which a person can shed heat

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TABLE 23-9. Sample Form to Provide Operational Information Location Type of operation Other teams

Hostage # Tactical

Suspect # EMS/medics

Warrant # K9

TABLE 23-10. Sample Form for Helicopter Information Helicopter Landing zone (LZ)

Obstructions? LZ cleared prior to mission start? Address:

LZ coordinates Latitude Longitude

Figure 23-29. Air ambulance helicopter preparing for tactical casualty evacuation. (Courtesy Lawrence E. Heiskell, MD.)

through sweating in a hot environment. The TW is used to determine fluid requirements and the need for work–rest cycles. The weather-related components of the MTA are used to determine the appropriate uniform to wear and the shelter required to prevent overheating or hypothermia (Table 23-11). Water sources should be recorded prior to the mission as part of the MTA. 5. Plant and animal threats. Plant exposures, especially to poison ivy and poison oak, are common to snipers. Snakebites are common to team members working with police dogs. Anticipated animal threats should be recorded, along with telephone numbers for the police veterinarian, animal control, and poison control, including sources of antivenom (Table 23-12).

Forms and Documentation Medical records should be kept for the team and for anyone treated or evaluated as a TEMS patient. Records should be stored for a minimum of 10 years and have proved to be indispensable as defense documents in several antipolice liability lawsuits. Without a medical record, there is no proof that appropriate medical care was given.

Protection # Patrol

Open terrain search # Detective

Terrorist # FBI/other


THE TACTICAL MISSION Each mission has a number of phases55,94: 1. Warning order (issued when the tactical team is first requested, and establishes the situation and chain of command) 2. Gathering of intelligence a. Building intelligence (targets location and surrounding areas and includes avenues of approach, escape routes, and rally points, as well as natural and man-made obstacles, fields of fire, opportunities for cover and concealment) b. Suspect or hostage intelligence (as detailed as possible) c. Medical threat assessment (complete) 3. Operation order 4. Briefing phase a. Detailed planning b. Detailed briefing c. Equipment selection d. Move to staging 5. Execution phase a. Entry b. Secondary search c. Transfer to arrest team and investigation team d. End of mission 6. Debriefing phase a. All persons, weapons, equipment, injuries, shots fired, and ammunition must be accounted for. b. Any problems must be discussed. In general, a tactical mission follows this order, although it may differ somewhat between agencies and missions. Proper handling of each point is required in order for a mission to flow seamlessly. Without proper intelligence, a mission becomes hazardous.


RESERVE PROGRAMS The ways a tactical medical team is utilized by a law enforcement agency can differ widely, especially between the East Coast and the West Coast. For example, in the western United States, especially California, Arizona, Nevada, Washington, Utah, and Oregon, there are many reserve programs in the police and sheriff’s departments.63 In these programs, the tactical medical provider has additional, formal law enforcement training, such as found in the Peace Officer Standards of Training (POST) program in California. This program allows the provider to be a sworn peace officer, bringing about an enhanced comfort level for the department and potentially mitigating some issues of civil liability. On the East Coast, reserve opportunities are less common, and medical providers typically serve as auxiliary units borrowed from traditional fire and EMS agencies. The liability issues and expenses in this type of relationship are often resolved via a written “memorandum of understanding” between the participating agencies.82

Chapter 23: Tactical Medicine and Combat Casualty Care

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TABLE 23-11. Sample Form for Weather-Related Information Temp high Temp low Rain % Wind: MPH Humidity %

Wet-bulb temp H2O qt/hr Rest Min/Hr Cold casualties Heat casualties Uniform adjustments

90 2.0 40 Work cycles Yes/No Shelter: Y/N

Sunrise: AM Sunset: PM Night ops: Duration: Location:

TABLE 23-12. Animal and Plant Threats Animal Threats Yes/No Animals present? Yes/No Police dog? Yes/No # Types of animals Number: Do you anticipate wild animals? Poisonous snake exposure: Veterinarian address: Yes/No Animal Control: Poison Control: 973-470-2242 800-222-1222 Plant Threats Yes/No Exposure to poisonous plants likely? Yes Type No Tecnu or Ivy Block available? Yes No Uniform adjustments needed? Yes Recommendations: No

Yes/No

What type? Vet phone:

Selecting appropriate providers must be accomplished through interviews, psychological testing, background investigations, and physical fitness testing. The tactical team leaders should use a careful approach in the selection process for each candidate, just as they do for other members of the team.58


MILITARY COMBAT FIELD UNITS Field units vary significantly with the mission, service, and threat (Fig. 23-30). Most often, medical care is provided in the open, or in as secure a location as possible. It is done on the ground, on a table, in the back of a Humvee, or on an aircraft or a watercraft. Specific types of shelter and equipment are available, most often in the far-forward care under fire and the tactical field care phases, but generally the equipment is as noted earlier. When CBRN threats or high explosives are added to the scenario, the forward elements are the same, with the exception of the appropriately protective clothing. Once evacuation occurs, the injured team member is taken to a standard unit with the capability for decontamination and treatment, much as is done in the civilian setting. Most larger military transport planes have the capability to accept a critical care air transport team (CCATT), which has a physician trained in critical care (emergency medicine, anesthesiology, internal medicine), a critical care nurse, and a respiratory technician. Most larger Navy ships are equipped with fully functioning operating rooms and intensive care units, or they can expand to provide this service quickly. All the services have basic medical units, from the selfaid or buddy-aide, to an aid station (with a physician), to forward resuscitative systems (surgical and nonsurgical), to surgical companies, combat surgical hospitals, and their equiva-

Figure 23-30. Law enforcement tactical medical team during a training exercise. (Courtesy Lawrence E. Heiskell, MD.)

lents. All services also have teams that are available to move far forward to provide surgical capabilities quickly should the need arise. These units can operate on any semi-flat surface, do resuscitative surgery, and package the patient for expeditious transport for further care.13

Uniforms and Personal Protective Gear The standard military tactical operator carries between 40 and 60 pounds of equipment when heading into battle. For longer

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missions, gear is heavier. Clearly, the operator needs to be in excellent physical condition, and the mission commander must proactively manage nutrition, hydration, and exertion levels. From anecdotal reports, the military has seen a significant decrease in truncal injuries because body armor has improved. The medical personnel have noted that the insurgent combatants in Operation Iraqi Freedom have changed their IEDs to target the head, neck, and extremities more than the whole body. Continued development is underway to produce body armor that will protect against higher-energy weapons, protect extremities, and be lightweight and flexible enough to allow fieldwork. As protective clothing is not removed in the field, the medic must work under and around it. Vigilance is required to check all body areas for hidden wounds. This is clearly more difficult in the field, in the dark, with sound and light restrictions, and with clothing in place than when the patient is undressed on the trauma table. Because the medic carries all the usual combat equipment, medical equipment is additional. Stethoscopes are usually left behind, as the medic cannot use the earpieces under the helmet, the environment is not conducive to being able to hear anything, and the victim is usually wearing body armor. Advanced medical gear is usually found on the MedEvac vehicle, or further to the rear where it is safe enough to remove protective equipment and further evaluate and treat the patient.


EDUCATION AND

TRAINING PROGRAMS

Tremendous advancement in tactical medicine education over the last decade has resulted in numerous training programs, many providing formal continuing medical education (CME) credits. These courses focus on the core issues of tactical medicine. A unique aspect of tactical medicine is application of ALS in an austere environment. The traditional approach to providing EMS is often not feasible in a tactical situation.89 Cost-effective training is available and should be afforded to all involved medical personnel, including prehospital care providers and physicians, who should be trained to the highest level possible. Such training provides emergency medical personnel with an understanding of tactical procedures and an appreciation for why some routine prehospital care techniques may not be appropriate in the tactical environment.53,57 Tactical medicine training needs to be as realistic as possible with live teaching scenarios in full tactical gear. This allows the medical providers to more fully understand the unique aspects of law enforcement tactical operations and the roles and responsibilities of each team member, along with the integration and application of EMS. With an established body of knowledge and skills, graduates of such training programs are better prepared to effectively perform as safe tactical medical providers.64 The International School of Tactical Medicine, a law enforcement agency program, is based at the Palm Springs Police Department Training Center in Palm Springs, California. This school has conducted high-quality realistic tactical medical training courses since 1996 and offers a 2-week, 80-hour program. The training and educational courses are designed for the U.S. military and federal and local law enforcement agencies to enhance their provision of medical care in the tactical environment. The standard curriculum for each course can be seen in Tables 23-13 and 23-14. Both the basic and advanced

TABLE 23-13. Sample Curriculum for Basic Tactical Medicine (BTM) Training Day 1

Day 2

Day 3

Day 4

Day 5

Administration and Introduction Introduction to Tactical Medicine Tactical Medical Equipment Tactical Equipment Team Concepts and Planning Slow and Deliberate Team Movement Introduction to Tactical Pistol Medical Aspects of Chemical Agents and Distraction Devices Forced Entry Techniques Dynamic Clearing Techniques Operational Casualty Care Wound Ballistics Hemostatic Techniques and Dressings Team Health Management Medical Aspects of Clandestine Drug Labs Tactical Medical Scenarios Introduction to MP5 Submachine Gun Special Operations Aeromedical Evacuation Medical Management of K-9 Emergencies Disguised Weapons and Street Survival Medical Threat Assessment Written Exam Safety Briefing Tactical Medical Scenarios

From International School of Tactical Medicine, copyright 1996–2005 (see www.tacticalmedicine.com).

courses offer category 1 CME credit through the American College of Emergency Physicians. The school is approved by the State of California Commission on Peace Officer Standards and Training (POST) (see www.tacticalmedicine.com). The Tactical EMS School of Columbia, Missouri, offers two TEMS educational programs. The Essentials of Tactical EMS is the basic entry-level course. The Tactical EMS Field Operations course is designed to augment the training offered in the essentials course and is scenario-based teaching with a focus on casualty care in the tactical environment (see www.tacticalspecialties.com). The Counter Narcotics Tactical Operations Medical Support program (CONTOMS) at the Casualty Care Research Center (CRC) is a multidisciplinary injury-control research and training facility in Bethesda, Maryland. It is based in the Department of Homeland Security, Federal Protective Service, Special Operations Division, forming the Protective Medicine Branch (see www.casualtycareresearchcenter.org).


THE FUTURE OF

TACTICAL MEDICINE

Tactical medicine will continue to grow as a medical discipline, and emergency medicine is the ideal specialty to lead its development. Since the fall of 2002, under leadership of the International Tactical EMS Association (ITEMS), a multidisciplinary group of subject matter experts has been working to achieve consensus on development of a standardized national curriculum for tactical medicine training.19 Emergency medicine residents and surgeons with no special interest in participating in tactical medicine should have an understanding of this discipline, as they may well have the opportunity to treat an injured

Chapter 24: Wilderness Orthopaedics

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TABLE 23-14. Sample Curriculum for Advanced Tactical Medicine (ATM) Training Day 1

Day 2

Day 3

Day 4

Day 5

Administration and Introduction Pediatric Trauma Management Trauma Anesthesia Building Clearing Techniques Review Tactical Medical Scenarios Range Advanced Pistol–MP5 Advanced Airway Management Advanced Airway Management Skills Stations Environmental Injuries WMD Biological Weapons Part 1 WMD Biological Weapons Part 2 Medical Issues of Less-Lethal Weapons Low Light Tactics and Team Movement Tactical Medical Scenarios Pistol–MP5 Field Courses Explosive Entry Demonstrations Medical Management of Blast Injuries WMD Chemical Weapons WMD Nuclear and Radiation Injuries Written Exam Safety Briefing Tactical Medical Scenarios

From International School of Tactical Medicine, copyright 1996–2005 (see www.tacticalmedicine.com).

operator or victim of violence associated with a tactical law enforcement action.24,40 There is a need for research into the unique aspects of civilian tactical medicine, such as injury prevention during operations, methods of ensuring optimal mental and physical preparedness for tactical operators, and evaluation of various standard EMS therapies for their feasibility and efficacy in tactical scenarios.

Figure 23-31. Tactical medics provide medical support under any and all operative conditions. (Courtesy Lawrence E. Heiskell, MD.)

Tactical medicine is wilderness medicine taking place in both the urban environment and some of the most remote places on earth. In these times, when the threat of violence to civilians in our society is at its greatest, we rely on our law enforcement professionals and the military to do all they can to keep us safe and protected. It is the role of tactical medics, providing medical care under any and all operative conditions (Fig. 23-31), to give back to these professionals by ensuring that someone is there to care for them if they are injured in the course of doing their duty. The references for this chapter can be found on the accompanying DVD-ROM.

Wilderness Orthopaedics Julie A. Switzer, Thomas J. Ellis, and Marc F. Swiontkowski

Musculoskeletal and soft tissue injuries account for 70% to 80% of injuries that occur in a wilderness setting.4,10 Being able to identify and provide initial, acute treatment of the most common types of injury is particularly important. In the initial management of a musculoskeletal injury, the following must be considered: the etiology and time of the injury, the direction of the causative force in relation to the individual or limb, and the environment where the accident occurred. These factors may indicate the severity of the injury and help determine examina-

24

tion and treatment priorities that can affect outcome. Special considerations for injuries to the skeletal system that occur in the wilderness include the effect of weather (exposure to wind, cold, or heat), lack of usual devices for stabilization of bone or joint injuries, and increased time to initiation of a victim’s definitive care. Stabilization of a victim’s cardiovascular and pulmonary status is critical. Once this has been accomplished, examination of the musculoskeletal system should be undertaken in a sys-

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tematic manner. Careful initial attention should be devoted to the spine. After the cervical, thoracic, and lumbar spine are evaluated and stabilized, the focus is brought to bear on the pelvis and extremities.


SPINAL INJURIES Cervical Spine In the wilderness, cervical spine fractures or dislocations often result from falls from a height or from high-velocity ski or vehicle crashes. Because head and cervical spine injuries are highly associated, victims with significant head injuries should be considered to have cervical spine injuries, especially if the individual is unconscious. Ideally, a person with a suspected cervical spine injury is placed on a backboard with neck immobilization and promptly evacuated. When transporting an individual with a cervical spine fracture or dislocation, the neck must be stabilized to prevent further injury. Approximately 28% of persons with cervical spine fractures also have other spinal fractures.3 Therefore, the person providing care must protect the entire spine. When a cervical spine injury is suspected, the field examination involves grading motor strength, documenting sensory response to light touch and pinprick, and noting the presence or absence of the Babinski reflex. When appropriate supplies are available, a rectal examination should be done. Complete lack of tone and failure of the sphincter muscles to contract when pulling on the penis or clitoris (the bulbocavernosus reflex) indicate spinal cord injury. Neurologic deficit often results from cervical spine fracture. Complete neurologic injury from the occiput to the C4 level is usually fatal because of paralysis of the respiratory muscles. The corollary to this is that surviving victims generally have partial deficits or are neurologically intact. Axial cervical spine fractures may result from flexion forces (most common), extension forces, rotational forces, or a combination of these. They most commonly occur at C5-6.3 Fracture of the C1-2 complex results from axial loading (a C1 ring fracture, or Jefferson fracture) or from an acute flexion injury (a C2 posterior element fracture, or hangman’s fracture). A pure flexion event may dislocate one or both posterior facets, producing neck pain and limitation of motion. Because the interspinous ligament is ruptured, in this fracture dislocation victim transport must be done with the neck rigidly immobilized to reduce the risk of posterior motion in this highly unstable condition. Fractures and dislocations may result in neurologic insult distal to the bony injury. Because flexion injuries are the most common cervical spine injuries, the neurologic deficit is generally an anterior cord syndrome. In this setting, the victim suffers complete motor and sensory loss but retains proprioception.

Figure 24-1. Wedge compression fracture from axial or flexion loading at the thoracolumbar junction.

Thoracolumbar Spine

Figure 24-2. Calcaneus fracture, sustained as a result of a fall from a height.

Thoracolumbar spine fractures occur most frequently at the thoracolumbar junction. Because the thoracic spine is well splinted by the thoracic cage, when an axial or flexion load is applied, the ribs diminish forces on the thoracic vertebral bodies and transmit the force to the upper lumbar levels. In the wilderness, falls from significant heights or a high-velocity sporting vehicle crash may produce these fractures (Fig. 24-1). Thoracolumbar spine fracture may also be associated with major hindfoot fractures (particularly of the calcaneus). These injuries commonly occur when there is an axially loaded injury, such as

a fall onto the lower limbs from a height. With the identification of unilateral or bilateral calcaneus fracture, a concomitant spine fracture should be assumed to have occurred (Fig. 24-2). Therefore, an individual who sustains a calcaneus fracture as the result of a fall from a height generally should be transported under spinal precautions. When a spine fracture is suspected, a careful neurologic examination should be performed as part of the secondary

Chapter 24: Wilderness Orthopaedics

Figure 24-3. Bilateral sacroiliac joint dislocations and a pubic symphysis disruption make this pelvis injury unstable both anteriorly and posteriorly. Significant care should be exercised in transporting an individual with suspected pelvic ring disruption.

575

Figure 24-4. Three-dimensional computed tomographic scan of an acetabular fracture.One of the fracture fragments along the inner pelvic brim probably created a small bladder injury in this patient.

survey, with close attention paid to the dermatomal response to light touch and pinprick, motor function, and the presence or absence of cord level reflexes. Because significant fluctuations in sympathetic tone may occur, the rescuer should monitor blood pressure and body temperature, taking appropriate steps to cool or warm the victim. If evacuation cannot be performed immediately, hemodynamic and neurologic function should continue to be noted and documented. When there is significant head injury, a spinal injury should be assumed to be present. The victim should be logrolled, maintaining perfect spinal alignment, and carefully placed on a backboard. The scoop stretcher may be used in this situation (see Chapter 34).


PELVIC INJURIES A study of mortality in the wilderness setting in Pima County, Arizona, between 1980 and 1992 demonstrated that most deaths occurred as a result of falling or drowning.5 Pelvic fractures generally occur with a fall from significant height, highvelocity ski accident, or vehicle crash. The direction of force is directly related to the fracture and influences definitive management.16,18 Pennal and colleagues11 and Tile18 divide pelvis fractures into anteroposterior (AP) compression injuries, lateral compression (LC) injuries, and vertical shear (VS) injuries. In addition, there are simple, nondisplaced inferior or superior ramus fractures and avulsion fractures. On clinical examination, these rami and avulsion fractures are generally appreciated as areas of tenderness without instability. Lateral compression injuries are usually stable, with impaction of the posterior structures. They are usually not emergent surgical or medical situations. AP compression injuries demonstrate anterior instability, palpable ramus fractures, or pubic symphysis gapping (Fig. 24-3). These fractures, which may include acetabular fractures, are often accompanied by bladder, prostate, or urethra injury (Fig. 24-4). If a pelvic fracture is suspected, it should be determined whether there is posterior injury to the pelvic ring, as this is

Figure 24-5. SAM Sling.

associated with significant hemorrhage, neurologic injury, and, ultimately, mortality. Posterior ring fractures are identified by instability of the pelvis associated with posterior pain, swelling, and ecchymosis. This victim should be immediately evacuated on a backboard, taking care to minimize leg and torso motion. Hemodynamic instability may occur with pelvis fractures, especially if the injury is the result of translational or shear forces, or if the posterior pelvis elements are primarily involved. Bleeding associated with a pelvis injury is usually from cancellous bone at fracture sites, retroperitoneal lumbar venous plexus injury, or, rarely, pelvic arterial injuries. Medical antishock trousers (MAST), the portable SAM sling, or even a bed sheet wrapped around the pelvis of an individual with a suspected unstable pelvic fracture may provide stability and accomplish adequate tamponade of bleeding from the fracture.12 The applied sling belt or similar contrivance should be left in place until definitive care is available (Fig. 24-5).

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PART FOUR: INJURIES AND MEDICAL INTERVENTIONS


EXTREMITY INJURIES Physical Examination The physical examination should address circulatory, nerve, skeletal, and joint function.

Circulatory Function. Penetrating or blunt trauma can injure the major vessels that supply the limbs. Fractures can produce injury by direct laceration (rarely) or by stretching, which can produce intimal flap tears. These intimal injuries can occlude distal flow or lead to platelet aggregation and delayed occlusion. Thus, an examination of circulatory function should be done prior to the victim’s arrival at the definitive care center. The color and warmth of the skin or distal extremity should be assessed; pallor and asymmetric regional hypothermia may indicate vascular injury. In the upper extremity, the brachial, radial, and ulnar arteries should be palpated. In the lower extremity, the femoral, popliteal, posterior tibial, and deep peroneal arteries should be palpated. If blood loss, hypothermia, or obesity makes these pulses difficult to assess, temperature and color must be relied on to determine vascular integrity. Any suspected major arterial injury mandates immediate evacuation after appropriate splinting. Nerve Function. Nerve function may be impossible to assess in an unconscious or uncooperative person. In the conscious person, the results of light touch and pinprick tests should be carefully documented. For spinal and pelvic injuries, the dermatomal distribution of spinal nerves is assessed, and muscle function is evaluated by observing active function and by grading the strength of each muscle group against resistance. If possible, once the victim’s condition has been stabilized, nerve function to the distal extremities is established. These initial findings should be compared periodically with repeat examinations during transport. Any change, and, in particular, any deterioration in condition should be noted. Skeletal Function. The long bones of the lower extremity serve as the major structural supports for locomotion, whereas those of the upper extremity stabilize the soft tissues, enabling positioning of the hand in space. A visible angular deformity reveals a fracture; palpable crepitus confirms the diagnosis. The care provider in the field should perform appropriate splinting after aligning the limb using axial traction. After noting the degree and orientation of the limb’s position when the victim is found, there should be no delay in aligning and splinting fractures. Distinguishing joint injuries and intra-articular or very proximal or distal fractures must wait for the definitive care facility, where radiologic studies can be done. Similarly, distinguishing a wrist or ankle ligamentous injury from a fracture is not required for initial treatment. Joint Function. Muscle forces act across joints to improve the position of the lower limbs for ambulation and the hand for handling objects. Each joint has a normal range of motion and a certain minimal function to allow for stability. Making the diagnosis of a joint injury in the field allows appropriate splinting and prevents further damage during transport. The palpation of long bones begins distally and proceeds across all joints. A splint should be applied if there is palpable

crepitus, swelling, deformity, or a block to motion. If the victim can cooperate, each joint is taken through an active range of motion to quickly locate any injury. When this is not possible, passive motion of each joint is evaluated after palpation for crepitus and swelling. Any dislocations are reduced after completing the neurocirculatory examination. This generally relieves the victim’s discomfort considerably. Once reduction of the dislocation has occurred, stability is evaluated by careful, controlled motion. Joints with associated fractures or interposed soft tissues are frequently unstable after reduction. Great care is required in applying splints to prevent redislocation or further soft tissue injury. A report of details of the reduction maneuver, including orientation of the pull, amount of force involved, amount of sedation, and residual instability of the joint, should be provided to the definitive care physician.

Splinting Techniques A victim with suspected cervical or thoracolumbar spine trauma should be transported on a hard surface. Backboards or scoop stretchers (see Chapter 34) are most effective, but improvisation with hard pieces of wood, fiberglass, or straight tree limbs lashed together may be needed. If cervical spine injury is suspected, a roll of clothes or a water bottle can be placed as high as the victim’s mid face on either side of the head to prevent rotational movement. Tape applied from the supporting stretcher across the objects and the victim’s forehead adds stability. Any victim with a suspected major pelvis injury is transported in a similar fashion, stabilizing the pelvis with a circumferential sheet or piece of clothing, and holding the lower extremities as immobile as possible, with the knees slightly flexed. Many different extremity splints are available for use in the wilderness setting. These splints are lightweight, compact, and easy to use. They are designed to provide traction through the injured extremity, while using the intrinsic properties of the splint and the injured limb to apply the traction. With proper splint application, the injured limb can be immobilized securely in a functional position until definitive care is reached. Air splints may be of some benefit, but they are generally manufactured in one shape. Especially in the setting of injured tissues and in environments that might include wide temperature variability, these splints can cause untoward damage to an already injured extremity. Therefore, in more extreme conditions, an air splint is used only if it has an automatic adjustment valve for heat and altitude. Also, these splints should be stored in a minimally inflated state when the temperature is below freezing, to prevent ice from creating a means for the splint material to freeze or adhere together. Beaded vacuum splints can also be used. However, temperature and altitude considerations can make adequate and consistent inflation less reliable. When beaded vacuum splints and air splints are used, vigilance is required to ensure that no excessive pressure is applied to already injured soft tissues. Upper extremity splints may also be made from plaster or fiberglass, which can be applied over a soft cotton roll. Lightweight fiberglass splints, such as Orthoglass (Smith and Nephew), are easy to use and effective in the initial management of these injuries. These splints are pre-padded and can be applied with either cold or warm water. The warmer the water, the faster the fiberglass sets and the greater the exothermic reaction. Hot water should be avoided because it may generate an

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Figure 24-7. SAM splint.

1 Figure 24-6. Short leg splint, well padded and made with fiberglass stirrups. This type of immobilization, if materials are available, may be indicated for tibia–fibula, ankle, and severe foot injuries.

excessively exothermic reaction and possibly burn the skin. The fiberglass is immersed in water, the excess water is gently squeezed out, and the splint is applied. An elasticized bandage helps hold the splint where desired until the fiberglass is hard (Fig. 24-6). Air splints, when inflated, can adequately splint the upper extremity in this position. Wooden or metal splints, custom made or improvised, also can be used to stabilize an injured extremity. Hand splints are applied with the metacarpophalangeal (MCP) joints flexed 90 degrees and the interphalangeal (IP) joints extended. This position places the collateral ligaments at maximal length and prevents later joint contracture. Wrist or forearm splints are applied with the wrist in a neutral position— excessive wrist flexion or extension might compromise median or ulnar nerve function in an already compromised limb. The elbow is positioned in a splint or sling at 90 degrees, if possible. For shoulder fractures or dislocations, a commercially available sling or improvised triangular bandage should be used to take the weight of the arm off the injured structures. Although it may be difficult to place an injured elbow in 90 degrees of flexion and neutral pronation–supination, the upper extremity should be splinted in the position of function whenever possible. For the lower leg, air splints provide adequate immobilization of tibia or fibula fractures and of ankle fractures and dislocations. Splints made from plaster or fiberglass may be applied over cotton padding with elasticized wraps (Fig. 24-6). The SAM splint, an excellent first-aid item that may be molded to immobilize a wide variety of injuries, provides stability and strength through its aluminum and foam core (Fig. 24-7). The aluminum structure can be bent into three configurations to provide different degrees of stability, flexibility, and immobilization. The ankle is held in neutral position and the splint applied firmly. For transport, the lower extremity is positioned with the hip and knee extended and the ankle in neutral position. Victims with unstable lower extremity fractures or dislo-

2

3

4

Figure 24-8. Improvisation of an ankle wrap to be used for traction.

cations are transported in the recumbent position with the afflicted limb elevated. For hip or femur fractures or dislocations, traction is applied whenever possible, improvising when necessary (Fig. 24-8). For suspected hip, femur, or knee injury, a Thomas splint with a Spanish windlass or the Kendrick traction device (a lightweight,

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PART FOUR: INJURIES AND MEDICAL INTERVENTIONS

Figure 24-10. A femoral splint applied against the ischial tuberosity provides traction for this subtrochanteric femur fracture. Figure 24-9. Slishman splint.

more conveniently packaged splint) has traditionally been used. Similar, but lighter-weight and more compact splints include the Slishman splint and Reel splint (Fig. 24-9). The design principles of the Slishman splint are similar to those of the Thomas and Kendrick splints. The ring of the Thomas splint rests against the victim’s ischium and pubis, whereas the Slishman splint applies traction through the pubis (Fig. 24-10). The Kendrick splint employs a rigid, retractable pole and cuffs. The Reel splint uses a multi-angle and hinge system to provide traction in anatomic regions that are especially difficult to access (Fig. 24-11). If commercial splints are unavailable, the injured leg is strapped to the noninjured leg, with a tree limb or walking stick placed between them. If possible, the victim is transported on a backboard.

of an open fracture. Most open fractures persistently ooze blood or fat globules from the laceration, which may facilitate diagnosis. General care of an open fracture outdoors depends on evacuation time. Open fractures require prompt operative irrigation, debridement, and stabilization. If evacuation can be completed within 8 hours, realign the fracture, administer a broadspectrum antibiotic, and splint the extremity. If bone ends extrude through the skin, cover the exposed bone with a povidone-iodine solution–soaked gauze sponge, splint the extremity, and arrange for prompt evacuation. If evacuation time exceeds 8 hours, in addition to antibiotic administration and splinting, irrigation and debridement in the field may be attempted. Antibiotic options are listed in Box 24-1.

Open Fractures

Amputation

Recognizing an open fracture is imperative; without prompt surgical treatment, the incidence of osteomyelitis in this setting is high.7 In an open fracture, the fractured bone communicates with a break in the skin. With subcutaneous bones (e.g., tibia), open fractures are easily identified, but with other bones (e.g., humerus, femur, pelvis) that have more surrounding soft tissue, identification is more difficult because the fractured bone end usually retracts once it punctures the skin and is then covered by soft tissue. A laceration near a fracture may be an indication

In the wilderness, the amputation victim requires immediate evacuation. Control hemorrhage using direct pressure; tourniquets are virtually never indicated. Without cooling, an amputated part remains viable for only 4 to 6 hours; with cooling, viability may extend to 18 hours. Cleanse the amputated part with saline or water, wrap it in a moistened sterile gauze or towel, place it in a plastic bag, and transport it in an ice-water mixture. Do not use dry ice. Keep the amputated part with the victim throughout the evacuation.

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Box 24-1. Antibiotic Options INTRAVENOUS

Cefazolin (Ancef) 1 g q8h and gentamicin (5 mg/kg) q24h or piperacillin with tazobactam (Zosyn) 3.375 g q6h INTRAMUSCULAR

Ceftriaxone (Rocephin) 1 g q24h Oral ciprofloxacin 750 mg bid and cephalexin (Keflex) 500 mg qid WATER EXPOSURE

Ciprofloxacin 400 mg IV or 750 mg PO bid; or a sulfonamide and trimethoprim conbination (Bactrim DS: 800 mg sulfamethoxazole and 160 mg trimethoprim) with either cefazolin (Ancef) 1 gm IV q8h or cephalexin (Keflex) 500 mg PO q6h

A DIRT OR BARNYARD

Add penicillin 20 million units IV qd or 500 mg PO q6h. IF PENICILLIN ALLERGY

Use clindamycin 900 mg IV q8h or 450 mg PO q6h in place of penicillins and cephalexin (Keflex). ALTERNATIVES

Erythromycin 500 mg q6h or amoxicillin 500 mg PO q8h

B Figure 24-11. A and B, Reel splint.

Compartment Syndrome A compartment syndrome begins when locally increased tissue pressure reduces arterial and, ultimately, capillary blood flow to a muscle compartment. When local blood flow is unable to meet metabolic demands of the tissue, ischemia ensues. In the wilderness, a compartment syndrome most frequently occurs in association with a fracture, crush injury, or severe contusion. It can also occur when the victim has been lying for some time across an extremity so that the body weight occludes the arterial supply. Elevated local tissue pressure (compartment pressure within 10 to 20 mm Hg of diastolic arterial blood pressure) can also occur with acute hemorrhage or after revascularization of an ischemic extremity. Because perfusion pressure is the most important variable in the development of compartment syndrome, hypotension can increase the risk of a compartment syndrome. Compartment syndrome can occur in the thigh, hand, foot, and gluteal regions. It is most common, however, in the forearm and, especially, the lower leg, because of the tight fascia in these regions. The conscious victim complains of severe pain out of proportion to the injury. The muscle compartment feels

extremely tight, and applied pressure increases the pain. There may be deceased sensation to light touch and pinprick stimuli in the areas supplied by the nerves traversing the compartment. Stretching muscles within the compartment produces severe pain. The most reliable signs of a compartment syndrome are pain, tight compartments, hypesthesia, and pain on passive stretch. Pulselessness, pallor, and slow capillary refill may not be observed, even with a severe compartment syndrome. Emergency evacuation is required when compartment syndrome is suspected. The victim must be definitively treated in the first 6 to 8 hours after onset to optimize return of function to the involved limb. Emergency fasciotomy, the treatment of choice, relieves the pressure. If a compartment syndrome develops and evacuation cannot occur within 8 hours, it must be decided whether the treating individual possesses the skill to perform a fasciotomy and whether it can be performed in an aseptic manner. Fasciotomies can convert a closed fracture into an open fracture and can provide a conduit for limb- if not lifethreatening infection. If a fasciotomy is to be done, antibiotics should be administered. In the forearm, the procedure usually involves making volar and dorsal incisions and splitting the underlying fascia. In the lower leg, the procedure usually involves making two long incisions, one on the medial aspect and the other on the lateral aspect of the leg, and splitting, in a vertical fashion, the compartmental fascia in each of the four lower leg compartments (Fig. 24-12). Fasciotomies for compartment syndrome that cannot be done within 12 hours of the syndrome’s development ought not to be undertaken. A retrospective analysis of individuals who underwent late release for compartment syndrome (more than 35 hours after the injury) demonstrated significant complication

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PART FOUR: INJURIES AND MEDICAL INTERVENTIONS

Figure 24-13. A 13-year-old sustained a left clavicle fracture in a boating accident.Significant shortening at the fracture site ultimately warranted open reduction and internal fixation. Figure 24-12. This photograph of a compartment syndrome demonstrates the degree of intracompartmental swelling that can occur in the leg.After fasciotomy for compartment syndrome, wound closure is often not possible, and skin grafting may be necessary.

and amputation rates. Therefore, even in an urban trauma hospital, delayed compartment release for compartment syndrome is not recommended.8

RICE Principle The general principle in the acute management of extremity injuries is rest, ice, compression, and elevation (RICE). For unstable fractures, immobilization is also indicated. Avoid heat for the first 72 hours after injury. Chemical cold packs work well, but cold packs made from ice or snow suffice. If cold packs are unavailable, the extremity can be immersed intermittently in a cold mountain stream. If ice is used, mix some water in a bag with the ice to more evenly distribute the cold. The cold pack to the injured area may be held in place with an elasticized bandage. A thin piece of fabric is placed between the cold pack and the victim’s skin to prevent frostbite. The ice is applied to the elevated extremity (above the level of the heart) for 30 to 45 minutes every 2 hours. A compressive dressing also helps decrease swelling but should not be used if development of a compartment syndrome is possible. In this situation, keep the limb at the level of the heart and avoid compressive dressings.


UPPER EXTREMITY FRACTURES Clavicle Fracture of the clavicle usually occurs in the middle or lateral third of the bone and is associated with a direct blow or with a fall onto the lateral shoulder (Fig. 24-13). Clavicle fractures are common with snow skiing and mountain bike riding. The victim complains of shoulder pain, which may be poorly localized. Arm or shoulder motion exacerbates the pain. To localize the problem, gently palpate the clavicle to identify the area of maximal tenderness. The presence of crepitus at the clavicle confirms the diagnosis. Although rare, a clavicle fracture can be associated with a pneumothorax if the cupula of the lung is punctured; therefore, auscultate the chest for breath sounds. Shortness of breath and deep pain on inspiration increase suspicion for a pneumothorax. Clavicle fracture may also be accompanied by injury to the brachial plexus, axillary artery, or subclavian vessels. In an

Figure 24-14. To control pain,a fractured humerus should be stabilized manually until a splint can be applied.

“individual with a fractured clavicle, a thorough neurocirculatory examination of the affected extremity is performed, and the skin is examined carefully. Approximately 3% to 5% of clavicle fractures may be open because of the bone’s subcutaneous location. The victim should be evacuated if there is a significant open wound, suspected pneumothorax, or nerve or vascular injury. Field treatment for a clavicle fracture consists of a figure-8 bandage or sling and judicious use of analgesics.

Humerus Fracture of the shaft of the humerus may result from a direct blow or torsional force on the arm. This fracture frequently occurs with a fall, rope accident, or skiing accident. Fractures of the midshaft and junction of the middle and distal third of the humeral shaft violate the spiral groove path of the radial nerve. If there is arm pain with deformity and crepitus, the arm is stabilized and the sensory and motor function of the radial nerve is carefully checked as part of the overall neurocirculatory examination (Fig. 24-14). Radial nerve function is evaluated by checking sensation in the dorsal thumb web space, and MCP extension with the proximal and distal IP joints flexed. When fracture of the humeral shaft is suspected, an appropriate coaptation splint made of plaster, fiberglass, or wood is firmly applied with an elastic bandage on the medial and lateral sides of the humerus. A sling is useful for comfort. Acute reduction of the fracture is not routinely required.

Chapter 24: Wilderness Orthopaedics

Figure 24-15. Comminuted proximal humerus fracture.

Fracture of the proximal humerus is often difficult to differentiate from shoulder dislocation in the acute phase. The mechanism is frequently a high-velocity fall onto an abducted, externally rotated arm, or a direct blow to the anterior shoulder. The victim complains of severe pain around the shoulder with palpation or with any arm motion. Palpable crepitus confirms the diagnosis. Although the inclination to attempt an emergent reduction may be compelling (it may be mistaken for a shoulder dislocation), this fracture does not routinely require acute reduction; application of an arm sling is appropriate field management (Fig. 24-15). Fracture-dislocation of the proximal humerus can also occur. Most dislocations are anterior. Anterior or posterior fullness, with crepitus on the injured side compared with the uninjured side, suggests the diagnosis. This is a more severe injury than a simple shoulder dislocation, so a very careful neurocirculatory examination should be performed. Any significant nerve or vascular injury should prompt evacuation to a definitive care center (Fig. 24-16). Fracture of the distal humerus is frequently extra-articular in children and intra-articular in adults. Children generally sustain supracondylar fractures after falls from heights. Extension-type injuries are much more common than the flexion type, and they most commonly occur in children aged 4 to 8 years. Deformity, swelling, pain, and crepitus are present, and the diagnosis of fracture is fairly obvious. A careful neurocirculatory examination should be performed, focusing on the motor examination of flexion of the thumb and distal IP joint of the index finger, because injury to the anterior interosseus nerve, which supplies innervation to these muscles, is frequently associated with these fractures. If the radial pulse is absent, an attempt should be made to flex or extend the elbow while palpating the radial pulse. If the pulse improves, the limb is splinted in that position for transport. If the pulse does not improve and definitive care is more than an hour away, a reduction is performed. After

581

Figure 24-16. This woman attempted to break her fall with her outstretched right upper extremity, resulting in a proximal humerus fracture and posterior shoulder dislocation. Relocation of this injury in the field is nearly impossible and should not be attempted.

available sedation is given, the supinated elbow is extended with gentle longitudinal traction. The fracture is reduced by flexing the elbow while maintaining longitudinal traction, and the elbow is splinted in 90 degrees of flexion. Evacuation should be performed promptly. For the adult with elbow pain, crepitus, deformity, and swelling after a fall, the neurocirculatory examination is performed, and then a splint is applied with the elbow at 45 or 90 degrees of flexion, depending on the victim’s comfort. Reduction should not be attempted without radiographic confirmation because crepitus is more often associated with a fracture than with a dislocation. Evacuation should be performed promptly if there is an open fracture or neurocirculatory deficit. Subluxation of the radial head in children (nursemaid’s elbow) occurs when a longitudinal pull is applied to the upper extremity (Fig. 24-17). The orbicular ligament partially tears, allowing a portion of it to slip over the radial head. An audible snap may be heard at the time of the injury. The initial pain from the injury subsides rapidly, and the child does not seem distressed but refuses to use the extremity. Any attempt to supinate the forearm brings a cry of pain and distress. If a definitive care center is nearby, the injury is splinted and evacuation is arranged. Otherwise, if the history and examination are consistent with the diagnosis, a reduction can be attempted. First the slightly flexed forearm is supinated; if this fails to produce the characteristic snapping sensation of reduction, the elbow is maximally flexed in supination until the snapping sensation occurs (Fig. 24-18). If the reduction is successful, the child is usually content and playing within 5 to 10 minutes, and no immobilization of the joint is indicated. If the reduction is unsuccessful, the child continues to avoid using the involved arm and should be evacuated for definitive care.

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Figure 24-17. Nursemaid’s elbow most commonly occurs when a longitudinal pull is applied to the upper extremity. Usually the forearm is pronated. There is a partial tear in the orbicular ligament, allowing it to subluxate into the radiocapitellar joint. (From Rockwood CA Jr, Wilkins KE, King RE [eds]: Fractures in Children, 3rd ed. Philadelphia, JB Lippincott, 1991.)

Figure 24-18. Reduction of nursemaid’s elbow injury.Left, The forearm is supinated.Right, The elbow is then hyperflexed. The rescuer’s thumb is placed laterally over the radial head to feel the characteristic snapping as the ligament is reduced. (From Rockwood CA Jr,Wilkins KE, King RE [eds]: Fractures in Children, 3rd ed. Philadelphia, JB Lippincott, 1991.)

Radius Radial shaft fracture is commonly associated with a motor vehicle crash or an industrial accident but may occur with a fall involving angular or axial loading of the forearm. A radial shaft fracture may be associated with dislocation of the distal radio-

ulnar joint (Galeazzi fracture). Therefore the wrist should be examined for tenderness, swelling, and deformity. The victim generally complains of pain, and deformity and crepitus are noted over the radial shaft after a fall or direct blow. Any arm motion exacerbates the pain. When both the radius and ulna are fractured, forearm instability is marked. The joint above (elbow) and the joint below (wrist) should always be examined for tenderness, crepitus, and deformity. Once a fracture of the radius or both bones of the forearm is identified, the wrist, forearm, and elbow are splinted in the position of function. Fractures of the radial head generally occur in young to middle-aged adults who fall onto outstretched hands. The victim complains of pain about the elbow, with loss of full extension, and pain at the radial head on the lateral side of the elbow with direct gentle pressure and rotation of the forearm. Fracture of the radial head or neck frequently produces an elbow hemarthrosis, which is identifiable by fullness posterior to the radial head and anterior to the tip of the olecranon (Fig. 24-19). A fluid wave can sometimes be ballotted. If equipment is available and the diagnosis is certain, the hemarthrosis is aspirated and 5 mL of lidocaine is instilled. The elbow is gently moved through a range of motion and then placed in a posterior splint in 90 degrees of flexion with the forearm supinated. On a prolonged expedition when definitive care cannot be reached, the splint is removed after 5 days so that the victim can perform intermittent range-of-motion exercises (both flexion–extension and pronation–supination), and the splint is reapplied for comfort. With more comminuted radial head fractures, attempts at motion produce pain and crepitus, and motion remains restricted. These injuries require operative treatment. Although most individuals lose some extension and pronation–supination, early motion may prevent permanent loss of motion when the radial head fracture is nondisplaced or minimally displaced. The arm is splinted in supination to

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Figure 24-19. Fracture of the neck of the radius, sustained in a fall. Pain on palpation at the lateral aspect of the elbow, in the region of the radial neck and head, would be anticipated.

prevent contracture of the intraosseous ligament and loss of supination. Fracture of the distal metaphyseal radius is generally associated with the fall of an older osteoporotic individual onto the outstretched hand (Fig. 24-20). In the wilderness, these fractures occur in younger adults with falls from significant heights onto outstretched hands. Ulnar styloid fracture often accompanies intra-articular fracture of the distal radius. Pain, deformity, and crepitus are obvious. When this injury is suspected, a distal neurocirculatory examination is performed, focusing on the sensory function of the median nerve. Median nerve injury or compression at this level of injury would manifest primarily as decreased sensation of the volar palm and fingers (the thumb, index finger, middle finger and the radial half of the ring finger). Weakness in the opponens and abductor pollicis muscles might also be noted. If there is neurocirculatory compromise and definitive care is more than 2 hours away, a gentle reduction is performed. One hand is placed on the forearm to provide countertraction and the other around the wrist of the involved extremity. The wrist is dorsiflexed and longitudinal traction is applied as the wrist is returned to a neutral position. A splint is applied to immobilize the wrist and elbow. As seen with many extremity fractures, there is a bimodal age group distribution in distal radius fractures; distal radius and ulna fractures occur commonly in children, too. They are seen most frequently in girls aged 11 to 13 years and in boys aged 13 to 15. These fractures are not usually comminuted but can be difficult to reduce (Fig. 24-21). In cases involving an open fracture, a significant distal neurologic deficit, or an abnormal circulatory examination, splinting and evacuation should be prompt. The limb should be kept elevated above the heart during transport.

Ulna Ulna shaft fracture is most often associated with fracture of the radial shaft at the same level. When isolated, it usually occurs

Figure 24-20. Lateral plain radiograph of a 75-year-old hiker who fell onto her outstretched hand and sustained a distal radius fracture.

as a result of a direct blow, the so-called nightstick fracture. Fracture of the ulnar shaft can be associated with dislocation of the radial head (Monteggia lesion), so elbow function is carefully assessed. In the wilderness, the most frequent mechanism of injury is bracing a fall or collision with the forearm. Pain, localized swelling, and crepitus are present. A long-arm splint is applied in the position of function. An open fracture is an indication for prompt evacuation. Fracture of the proximal ulna (olecranon) results from a fall onto the posterior elbow, or from violent asymmetric contraction of the triceps muscle. The victim may be unable to extend the elbow actively against gravity if the triceps is dissociated from the forearm with a complete olecranon fracture. On initial examination, the victim has pain, significant swelling, and a palpable gap in the olecranon. With severe trauma, olecranon fracture may be associated with an elbow dislocation or an intra-articular fracture of the distal humerus, which can only be diagnosed radiographically (Fig. 24-22). A complete distal neurocirculatory examination should be performed. The shoulder and wrist should be examined, and a splint should be applied in the position of function and comfort. An open fracture, absent pulse, severe swelling, or neurologic deficit should prompt immediate evacuation.

Wrist/Carpus Wrist fractures occur with significant rotational forces or high axial loading forces, as occur in falls onto the hand. The victim first complains of pain and later of wrist swelling. Hand use or forearm rotation produces significant pain. Many carpal bone fractures are associated with wrist dislocation. Reduction of dislocations is described later.

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A

Figure 24-22. Closed, displaced olecranon fracture dislocation. A sling or posterior splinting is appropriate for this injury type until definitive care can be provided.

B

Extensor pollicis longus Scaphoid

C Figure 24-21. Technique for reduction of a complete fracture of the forearm.A, Initial fracture position. B, Hyperextend fracture to 100 degrees to disengage the fracture ends. C, Push with the thumb on the distal fragment to achieve reduction.(A to C from Green N,Swiontkowski MF: Skeletal Trauma in Children, vol 3, ed 2. Philadelphia,WB Saunders, 1998.)

Carpal bone fractures cannot be diagnosed without radiographs. Scaphoid (navicular) fracture is the most common fracture and is suspected when the patient’s area of maximal tenderness is in the “anatomic snuffbox” (Fig. 24-23). If appropriate splinting materials are available, a thumb spica splint is applied, immobilizing both the radius and the entire thumb. With fracture of the hook of the hamate bone, the victim complains of pain at the base of the hypothenar eminence. This injury occurs when the hand is used to apply significant force to an object with a handle on it, such as an ax or hammer, and great resistance is met. A short-arm splint suffices for this injury, and for other suspected carpal injuries, until definitive treatment is obtained. With open fractures or those accompanied by median nerve dysfunction, the victim should be promptly evacuated.

Metacarpals Fracture of the metacarpal base or shaft occurs with crush injuries or with axial loads, such as when rocks or other immov-

Extensor pollicis brevis Abductor pollicis longus

Figure 24-23. The scaphoid (navicular) bone sits in the “anatomic snuffbox”of the radial aspect of the wrist.

able objects are struck. Fractures at the base of the metacarpals are suspected when tenderness, crepitus, and, occasionally, deformity are present. These should be managed with a shortarm splint or an ulnar gutter splint. Fractures of the metacarpal necks also occur by the same mechanism and usually involve the fifth and fourth metacarpals. These fractures can be associated with significant flexion deformity. Up to 40 degrees of flexion in the fifth and fourth digits can be accepted without compromising hand function, so these fractures rarely require reduction. Rotational deformity of the metacarpal is poorly tolerated, however, and should be anticipated with suspected metacarpal fractures. With the MCP and the IP joints flexed 90 degrees, the fingernails should be parallel to one another and perpendicular to the orientation of the

Chapter 24: Wilderness Orthopaedics palm. The terminal portions of the digit should point to the scaphoid tubercle. If this is not the case, a rotational deformity should be strongly suspected. When malalignment or significant shortening with a suspected shaft fracture is noted, the fracture is reduced with longitudinal traction on the involved digit. A fractured metacarpal shaft or neck is immobilized by applying an aluminum splint (or stick) to the volar surface of the finger and palm and taping the involved digit to the adjacent digit, with the MCP joint at 90 degrees. This position provides maximal length of the collateral ligaments. Immobilizing the joint in this position prevents contractures that can lead to subsequent loss of motion. Fracture of the base of the thumb metacarpal often occurs with an axial force directed against a partially flexed thumb metacarpal. If the fracture extends into the joint, it often requires operative fixation. If this fracture is suspected, the thumb and wrist are immobilized in a thumb spica splint. An open metacarpal fracture needs cleansing, debridement, and presumptive antibiotic therapy for 48 hours or until definitive care is obtained.

Phalanges Fractures of the digital phalanges occur with crush injuries or when the digits are caught in ropes or in equipment being used to haul objects. Angular or rotational deformity and crepitus make these fractures obvious. Without radiographs, an intraarticular fracture with subluxation or dislocation is difficult to differentiate from an IP joint dislocation. Angular deformities in these fractures can be reduced using a pencil or thin stick placed in the web space as a fulcrum to assist in reduction. A fracture of the shaft of a phalanx is reduced by applying traction and correcting the deformity. The fractures are immobilized by taping the injured digit to the neighboring uninjured digit or to a volar splint. Nail-bed fractures or crushes are cleansed with soap, a sterile dressing is applied, and a protective volar splint is applied to prevent further injury.


UPPER EXTREMITY

DISLOCATIONS AND SPRAINS

Sternoclavicular Joint Traumatic dislocation of the sternoclavicular joint generally requires tremendous force, either direct or indirect, applied to the shoulder. Consequently, it is rare. Anterior dislocation is most common, with the medial head of the clavicle going anterior to the manubrium of the sternum. The victim complains of pain around the sternum and frequently has difficulty taking a deep breath. When the dislocation is posterior, significant pressure may be placed on the esophagus and superior vena cava. The victim may complain of difficulty swallowing and have engorgement of the veins of the face and upper extremities, representing superior vena cava obstruction syndrome. A step-off between the sternum and the medial head of the clavicle (compared with the uninjured side) confirms this diagnosis. Unreduced anterior dislocation does not produce neurocirculatory compromise and is treated with a sling. Reduction of a posterior sternoclavicular dislocation should be attempted as soon as possible if any neurocirculatory compromise is present. The victim is placed supine with a large roll of clothing or other firm object between the scapulae. Traction is applied to the arm against countertraction in an abducted and slightly extended

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position. The medial end of the clavicle may need to be manually manipulated to dislodge the clavicle from behind the manubrium (Fig. 24-24). If this fails, sharp, firm pressure is applied posteriorly to both shoulders. This maneuver is repeated several times, with a larger object placed between the scapulae if reduction attempts are initially unsuccessful. Alternatively, with the victim seated and the caregiver’s knee against the back between the shoulders, both shoulders are pulled back. If the victim remains in extremis, the midshaft clavicle is grasped with a towel clip or pliers and forcefully pulled out of the thoracic cavity. Once reduced, the injury is usually stable. The posterior sternoclavicular dislocation requires evacuation.

Acromioclavicular Joint The acromioclavicular joint is usually injured by a blow on top of the shoulder (Fig. 24-25). Because using the hand increases pain, the arm on the affected side is placed in a sling. As long as the individual can tolerate the discomfort associated with such an injury, evacuation is not necessary.

Glenohumeral Joint The head of the humerus at the shoulder joint is generally dislocated anteriorly and inferiorly. The usual mechanism of injury is a blow to the arm in the abducted and externally rotated position. This frequently occurs in skiing as the individual crosses the ski tips or goes forward on a mogul and lands face down with the arms in this position. Recurrent dislocations and dislocations in younger patients may be easier to reduce than first-time dislocations in older patients. A thorough motor, sensory, and circulatory examination of the involved extremity is performed. Axillary and musculocutaneous nerves are assessed carefully because they are the nerves most commonly injured with an anterior dislocation. Serial examinations of distal pulses, capillary refill, and forearm compartments are performed. The preferred method of reduction is linear traction along the axial line of the extremity while stabilizing the torso with a blanket or rope (Fig. 24-26). Narcotic or benzodiazepine premedication can be extremely helpful, but this should be avoided in a multiply injured victim if there is concern about altering mentation or adversely affecting blood pressure. A sheet, belt, webbed strapping, or avalanche cord can be tied around the caregiver’s waist and the victim’s bent forearm, so that the caregiver (standing or kneeling) can lean back to apply traction, leaving hands free to guide the head of the humerus back into position (Fig. 24-27). Padding is placed in the armpit and bend of the elbow to prevent pressure injury to sensitive nerves beneath the skin. Many other relocation techniques have been described. In the Milch technique, the patient is prone or sitting upright. The caregiver places his or her right hand in the axilla for a dislocated right shoulder and holds the victim’s hand with the left. The victim’s arm is gently abducted and pressure is applied to the humeral head. When the arm is fully abducted, it is rotated externally and gentle traction is applied to reduce the humeral head. This slow process can be highly successful in the acute setting because it usually does not require analgesics or muscle relaxants (Fig. 24-28).13 The success of this maneuver decreases as the time after dislocation increases. Scapular manipulation is also minimally traumatic and highly successful.2 The victim is placed prone and 5 to 15 pounds of traction are applied on the arm. Once relaxation is obtained,

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A

Sand bag between shoulders

B

Figure 24-24. Technique for closed reduction of the sternoclavicular joint. A, The patient is positioned supine with a sandbag placed between the shoulders.Traction is then applied to the arm against countertraction in an abducted and slightly extended position. For anterior dislocation, direct pressure over the medial end of the clavicle may reduce the joint. B, For posterior dislocation,in addition to the traction it may be necessary to manipulate the medial end of the clavicle with the fingers to dislodge the clavicle from behind the manubrium.C, For a stubborn posterior dislocation, it may be necessary to sterilely prepare the medial end of the clavicle and use a towel clip to grasp around the medial clavicle and lift it back into position. (From Rockwood CA Jr, Green DP, Bucholz RW [eds]: Rockwood and Green’s Fractures in Adults, 3rd ed. Philadelphia, JB Lippincott, 1991.)

C

the inferior angle of the scapula is raised and rotated toward the spine; the superior aspect is rotated away from the spine (Fig. 24-29). This can also be done with the victim in the standing position (Fig. 24-30). If the victim is standing, it may help to pull the arm forward as well as down. This technique generally requires excellent relaxation, but it can be highly successful. An alternative method is to have the victim lie prone so that the injured arm dangles free. A thick pad is placed under the injured shoulder. A 10- to 20-lb (4.5- to 9-kg) weight is attached to the wrist or forearm (the victim should not attempt to hold the weight), and it is allowed to exert steady traction on the arm, using gravity to relocate the humeral head (Fig. 24-31). A standing victim can bend forward at the waist as the caregiver pulls steadily downward on the arm to simulate the gravity effect. A gentle side-to-side motion at the wrist can help with

the reduction (Fig. 24-32). The Hippocratic maneuver of placing a foot in the axilla of the injured limb to achieve countertraction should be avoided because of increased pressure on the structures within the axillary sheath (Fig. 24-33). Posterior dislocation of the glenohumeral joint makes up less than 5% of shoulder dislocations. It may occur with adduction and axial loading of the shoulder, a direct blow to the anterior aspect of the shoulder, or as a result of marked internal rotation accompanying a grand mal seizure. Frequently, the dislocation is associated with either a humeral head impaction injury or a glenoid fracture. The victim complains of significant pain and loss of shoulder motion. Usually, external rotation is completely lost. On palpation of the shoulder, posterior fullness that is not found on the uninjured side can usually be detected. This dislocation can be more difficult to reduce than an anterior dislocation, so excellent analgesia is generally required. The

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Figure 24-25. Acromioclavicular joint surgery. A, Normal anatomy. B, Second-degree injury. C, Third-degree injury.

A

B

C

arm is flexed forward, rotated internally, and adducted to disengage the head from the posterior glenoid rim. Occasionally, lateral traction on the humeral shaft is also required. With longitudinal traction and anterior pressure on the humeral head from behind, reduction is achieved. If the reduction maneuver is successful, the arm is placed in a sling until definitive care is reached. If possible, a posterior dislocation is held in neutral or slight external rotation. Because of the significant incidence of fractures with these injuries, radiologic examination is required to make the diagnosis, and evacuation is mandated. If the reduction maneuver is not successful, the injured extremity is placed in a sling and evacuation is arranged as soon as possible.

Elbow Figure 24-26. Traction and countertraction for dislocated shoulder reduction.

Dislocation of the elbow occurs with hyperextension or axial loading from a fall onto an outstretched hand. The direction of

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Figure 24-27. Repositioning a dislocated shoulder. Attached to the victim’s forearm with a strap, rope, or sheet, the rescuer uses his body weight to apply traction, leaving his hands free to manipulate the victim’s arm. A second rescuer applies countertraction, or the victim can be held motionless by fixing the chest sheet to a tree or ground stake. (From Auerbach PS: Medicine for the Outdoors: The Essential Guide to Emergency Medical Procedures and First Aid, 4th ed. Guilford, CT, Lyons Press, 2003.)

Figure 24-29. Scapular manipulation technique for closed reduction of anterior glenohumeral dislocation. (Redrawn from Anderson D, Zvirbulis R, Ciullo J: Clin Orthop 164:181, 1982. In Browner BD, Jupiter JB, Levine AM, Trafton PG: Skeletal Trauma, vol 2, 2nd ed. Philadelphia, WB Saunders, 1998.)

Figure 24-28. Milch technique of closed reduction of anterior glenohumeral dislocation with the patient prone. The arm can be manipulated in the same manner with the patient supine. (Redrawn from Lacey T II, Crawford HB: J Bone Joint Surg 34A:108, 1952. In Browner BD, Jupiter JB, Levine AM,Trafton PG: Skeletal Trauma, vol 2, 2nd ed. Philadelphia,WB Saunders, 1998.)

dislocation is generally posterior and lateral. The diagnosis is clear, with posterior deformity at the elbow and foreshortening of the forearm. After carefully assessing distal sensory, motor, and circulatory status, reduction is performed. With countertraction on the upper arm, linear traction is applied with the elbow slightly flexed and the forearm in the original degree of pronation and supination. Downward pressure on the proximal forearm to disengage the coronoid from the olecranon fossa may be helpful. Hyperextension should be avoided. Adequate

Figure 24-30. Pulling on the hanging arm to relocate a dislocated humerus. (From Auerbach PS: Medicine for the Outdoors: The Essential Guide to Emergency Medical Procedures and First Aid, 4th ed. Guilford, CT, Lyons Press, 2003.)

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A

Figure 24-31. Stimson technique. (Redrawn from Rockwood CA, Green CP [eds]: Fractures in Adults, vol 1.Philadelphia, JB Lippincott, 1984.In Browner BD, Jupiter JB, Levine AM,Trafton PG: Skeletal Trauma, vol 2, 2nd ed. Philadelphia,WB Saunders, 1998.)

analgesia can be extremely helpful. An alternative method (Parvin’s method) is to place the patient prone over a log or makeshift platform and apply gentle downward traction on the wrist for a few minutes. As the olecranon begins to slip distally, the arm is lifted up gently. No assistant is needed, and if the maneuver is done gently, no anesthesia is required (Fig. 24-34). A modification of this maneuver (Meyn and Quigley’s method) is to hang only the forearm over the platform while applying gentle downward traction via the wrist and guiding the reduction of the olecranon with the opposite hand (Fig. 24-35). Reduction provides nearly complete relief of pain and restoration of normal surface anatomy. A posterior splint is applied with the elbow in 90 degrees of flexion and the forearm in neutral position. A sling is provided for comfort. If reduction is not successful after three attempts, or if a nerve injury is suspected, a splint is applied to the arm as it lies and evacuation is initiated.

Wrist Wrist dislocations are frequently associated with carpal fractures and are generally produced by falls onto an outstretched hand. A wrist dislocation may be difficult to differentiate clinically from a fracture of the distal radius. However, in either case, a reduction maneuver is performed after careful assessment of distal neurocirculatory function, focusing on median nerve function. The reduction maneuver is similar to that for a distal radius fracture. One hand is used to stabilize the forearm and the other to grasp the hand. First, the wrist is dorsiflexed if the dislocation is dorsal (most common) or volarflexed if the

B Figure 24-32. A, Pushing the lower edge of the scapula toward the spine while an assistant pulls downward on the hanging arm to assist in the relocation of a dislocated humerus. B, The downward pull on the arm may be slightly forward to help put the humerus back in the shoulder socket. (From Auerbach PS: Medicine for the Outdoors: The Essential Guide to Emergency Medical Procedures and First Aid, 4th ed. Guilford, CT, Lyons Press, 2003.)

dislocation is volar, and then longitudinal traction is applied. In general, significant dorsiflexion is required to obtain reduction, and premedication can be extremely helpful. If reduction is unsuccessful after three attempts, or if there is median nerve dysfunction, evacuation should be initiated. A short-arm splint is applied if reduction is successful, and the arm is elevated above the level of the heart until definitive care is procured. Pain and tenderness about the wrist with no significant deformity indicates a possible intercarpal ligamentous disruption or a carpal fracture, and a short-arm splint is applied.

Metacarpophalangeal Joint MCP joint dislocation is rare and may be produced by a crush injury or when the hand is caught in a rope. This dislocation may be dorsal or volar, with dorsal dislocation more common. Clinically, the joint is hyperextended and the phalanx shortened. Most dorsal dislocations are easily reduced. First, the proximal phalanx is hyperextended 90 degrees on the meta-

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Figure 24-33. Hippocratic technique of closed reduction of anterior glenohumeral dislocation. The foot is placed against the proximal humerus, and longitudinal traction is applied to the upper extremity. (Redrawn from Rockwood CA, Green CP [eds]: Fractures in Adults, vol 1. Philadelphia, JB Lippincott, 1984.)

Figure 24-34. Parvin’s method of closed reduction of an elbow dislocation. The patient lies prone on a stretcher, and the physician applies gentle downward traction on the wrist for a few minutes. As the olecranon begins to slip distally, the physician lifts up gently on the arm. No assistant is required, and if the maneuver is done gently, no anesthesia is required. (Redrawn from Parvin RW: Arch Surg 75:972, 1957. In Rockwood CA Jr, Green DP, Bucholz RW [eds]: Rockwood and Green’s Fractures in Adults, 3rd ed. Philadelphia, JB Lippincott, 1991.)

Figure 24-35. In Meyn and Quigley’s method of reduction, only the forearm hangs from the side of the stretcher. As gentle downward traction is applied on the wrist, the physician guides reduction of the olecranon with the opposite hand. (Redrawn from Meyn MA, Quigley TB: Clin Orthop 103:106, 1974. In Rockwood CA Jr, Green DP, Bucholz RW [eds]: Rockwood and Green’s Fractures in Adults, 3rd ed. Philadelphia, JB Lippincott, 1991.)

carpal, then the base of the proximal phalanx is pushed into flexion, maintaining contact at all times with the metacarpal head to prevent entrapment of the volar plate in the joint (Fig. 24-36). Straight longitudinal traction is avoided because it may turn a simple dislocation into a complex dislocation (see later). The wrist and IP joints are flexed to relax the flexor tendons. The joint usually reduces easily with a palpable and audible clunk. A dorsal–volar splint is applied with the joint held at 90 degrees of flexion. Irreducible or complex dislocations occur when the volar plate is interposed in the joint. Clinically, the joint is only slightly hyperextended and the volar skin is puckered over the joint. These dislocations are most common in the index finger, thumb, and small finger. A single attempt at reduction using the technique just described is indicated, but these dislocations usually require open reduction. If reduction of an MCP joint dislocation is unsuccessful, the joint should be splinted in the position of comfort and definitive treatment obtained as soon as possible. The thumb MCP joint is most commonly injured. Dislocations are reduced as already described. Injury to the ulnar collateral ligament of this joint (skier’s or gamekeeper’s thumb) results from a valgus stress, as may occur when an individual falls holding an object in the first web space. The victim complains of tenderness over the ulnar aspect of the MCP joint. There may be instability to radial stress with the joint held in 30 degrees of flexion, an indication for surgical repair. Often, the adductor aponeurosis becomes interposed between the ligament and its bony attachment, resulting in a Stener lesion

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Chapter 24: Wilderness Orthopaedics (Fig. 24-37). In the field, a thumb spica splint is applied and definitive care sought within 10 days. If splinting material is not available, the thumb is taped until definitive care can be obtained (Fig. 24-38).

Proximal Interphalangeal Joint Proximal interphalangeal (PIP) joint dislocations may be dorsal, volar, or rotatory, with dorsal dislocation by far the most common. Dorsal dislocation occurs with hyperextension and volar plate rupture. It can be associated with fracture of the volar lip of the middle phalanx, creating instability after reduction. Reduction is performed as described for dorsal MCP dislocation. Straight longitudinal traction is avoided to prevent entrapment of the volar plate into the joint. After reduction, the finger is taped to an adjacent finger to avoid hyperextension and

allow early motion (Fig. 24-39). As with MCP dislocation, a complex dislocation can occur, but it is rare. This is difficult to reduce closed and often requires open reduction. Volar dislocations are rare. For this injury to occur, the central slip must be disrupted, and the potential for a boutonniere deformity is present. The digit is reduced by flexion of the PIP joint, pushing the base of the middle phalanx dorsally. The PIP joint is treated like a rupture of the central slip, with the PIP joint splinted in extension. The distal interphalangeal (DIP) and MCP joints are left free to allow motion. Rotatory subluxation of the PIP joint occurring after a twisting injury is also rare (Fig. 24-40). The condyle of the head of the proximal phalanx is buttonholed between the lateral band and the central slip, both of which remain intact. This injury can be difficult to reduce. With both the MCP and PIP joints flexed, gentle traction is applied to the finger. This relaxes the volarly displaced lateral band and allows the lateral band to be disengaged and slip dorsally when a gentle rotary and traction force is applied. Further relaxation of the lateral band can be achieved by dorsiflexion of the wrist. After reduction, the finger is buddy taped and early motion is begun. With any dislocation of the PIP joint, definitive care should be sought promptly to ensure adequate reduction of the injury. “Jammed” fingers may be just as debilitating and painful as dislocated digits. With these injuries, stress the involved joint both radially and ulnarly to ensure collateral ligament integrity. If the joint is stable, the finger can be buddy-taped to an adjacent digit and immediate care is not indicated. If the finger is unstable, definitive care should be sought.

Distal Interphalangeal Joint

Figure 24-36. The single most important element preventing reduction in a complex metacarpophalangeal (MCP) dislocation is interposition of the volar plate within the joint space.It must be extricated surgically. (From Rockwood CA Jr, Green DP, Bucholz RW [eds]: Rockwood and Green’s Fractures in Adults, 3rd ed. Philadelphia, JB Lippincott, 1991.)

The DIP joint is less frequently injured than the PIP joint. Pure dislocations are rare and are usually dorsal and associated with an open wound. The reduction maneuver is similar to that used for dorsal PIP joint dislocation. The injury is usually stable after reduction. More commonly, a mallet-finger injury occurs when the extensor tendon is taut, as when striking an object with the finger extended. The basic injury is incompetence of the extensor tendon at its insertion into the distal phalanx. The three

Figure 24-37. Diagram of the displacement of the ulnar collateral ligament of the thumb metacarpophalangeal joint. A, Normal relationship, with the ulnar ligament covered by the adductor aponeurosis. B, With slight radial angulation, the proximal margin of the aponeurosis slides distally and leaves a portion of the ligament uncovered.C,With major radial angulation,the ulnar ligament ruptures at its distal insertion. In this degree of angulation, the aponeurosis has displaced distal to the rupture and permitted the ligament to escape from beneath it. D, As the joint is realigned, the proximal edge of the adductor aponeurosis sweeps the free end of the ligament proximally and farther away from its insertion. This is the Stener lesion. Unless surgically restored, the ulnar ligament will not heal properly and will be unstable to lateral stress. (Redrawn from Stener B: Acta Chir Scand 125:583–586, 1963.)

A

B

C

D

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A

B

Figure 24-38. Taping the thumb for immobilization. A, The buddy-taping method. B, A thumb-lock. If possible, padding should be placed between the thumb and forefinger. (From Auerbach PS: Medicine for the Outdoors:The Essential Guide to Emergency Medical Procedures and First Aid, 4th ed. Guilford, CT, Lyons Press, 2003.) Tape

Cotton or cloth padding

Figure 24-39. Buddy-taping method to immobilize a finger. (From Auerbach PS: Medicine for the Outdoors:The Essential Guide to Emergency Medical Procedures and First Aid, 4th ed. Guilford, CT, Lyons Press, 2003.) Central slip

Lateral band

Figure 24-40. Rotary subluxation of the proximal interphalangeal (PIP) joint. The condyle of the head of the proximal phalanx is button-holed between the lateral band and the central slip, both of which remain intact.(From Rockwood CA Jr, Green DP, Bucholz RW [eds]:Rockwood and Green’s Fractures in Adults, 3rd ed. Philadelphia, JB Lippincott, 1991.)

Figure 24-41. The three types of injury that cause a mallet finger of tendon origin. Top, The extensor tendon fibers over the distal joint are stretched without complete division of the tendon.Although there is some drop of the distal phalanx,the patient retains weak active extension. Center, The extensor tendon is ruptured from its insertion on the distal phalanx. There is usually a 40- to 45-degree flexion deformity, and the patient has loss of active extension at the distal joint.Bottom, A small fragment of the distal phalanx is avulsed with the extensor tendon. This injury has the same clinical findings as that shown in the center drawing.(From Rockwood CA Jr, Green DP, Bucholz RW [eds]: Rockwood and Green’s Fractures in Adults, 3rd ed. Philadelphia, JB Lippincott, 1991.)

splinted in slight extension for 6 to 8 weeks, leaving the PIP and DIP joints free (Fig. 24-42). A radiograph is obtained within the first 10 days to ensure that the joint is reduced. Occasionally, the flexor digitorum profundus (FDP) tendon is avulsed from its insertion on the distal phalanx. This occurs with forced hyperextension of the DIP joint while the FDP tendon is maximally contracted. The ring finger is most commonly injured. The diagnosis is made by demonstrating inability to flex the DIP joint with the PIP joint held in extension. Pain and local tenderness are more common over the PIP joint, where the retracted end of the tendon usually lies. The digit is splinted in flexion, and care should be sought within 7 days from a surgeon specializing in the upper extremities.


LOWER EXTREMITY FRACTURES Femur and Patella

types of mallet injuries are shown in Figure 24-41. Individuals with this injury lack full extension of the DIP joint when the MCP and PIP joints are kept in extension. Holding these joints in extension isolates the extensor tendon by neutralizing the intrinsic muscles. If an extension lag is noted, the joint is

In general, healthy, active individuals sustain fractures of the proximal femur only in falls from significant heights or from high-velocity injuries sustained, for example, during water or snow skiing. These fractures occur in the femoral neck, intertrochanteric, or subtrochanteric region (Fig. 24-43). When

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A

B

A

C

B D

E Figure 24-42. Mallet finger can be treated by immobilizing the distal interphalangeal (DIP) joint with a dorsal padded aluminum splint (A), a volar unpadded aluminum splint (B), a Stack splint (C), a modified Stack splint (D), or an Abouna splint (E). Each of these splints uses a threepoint fixation principle. (From Rockwood CA Jr, Green DP, Bucholz RW [eds]: Rockwood and Green’s Fractures in Adults, 3rd ed. Philadelphia, JB Lippincott, 1991.)

the head and spinal cord are uninjured, the victim complains of pain within the proximal thigh. In all but the thinnest individuals, there is little local reaction in terms of swelling or deformity around the hip region to aid in diagnosis. Any movement of the affected limb produces significant pain. In many cases, the affected limb is noticeably shortened and externally rotated. After a careful sensory, motor, and circulatory examination, the limb is realigned and, if available, a Kendrick, Thomas, or Reel

Figure 24-43. An intertrochanteric fracture caused by a fall from a height. Always check for other injuries that may result from a fall, such as lumbar spine fractures or calcaneus fractures.

splint is applied. An improvised traction splint can be fabricated. If none is available, the victim is transported on a backboard, with the limbs strapped together or tied to a board with a tree limb placed between them. Fracture of the femoral neck is associated with a significant risk of post-traumatic femoral head necrosis. Without a radiograph, this fracture is impossible to distinguish from a subtrochanteric or an intertrochanteric hip fracture. Because there is evidence that emergency treatment of a fracture of the femoral neck decreases the risk of post-traumatic avascular necrosis,14,17 rapid evacuation should be arranged for any victim in whom this injury is suspected. Fracture of the femoral shaft occurs by similar mechanisms (Fig. 24-44). Crepitus and maximal deformity are noted in the midportion of the thigh. After neurocirculatory examination, the limb is placed in traction or protected as noted previously. Any gross deformity of the shaft is corrected with gentle traction, and the neurocirculatory examination is repeated. This fracture may be an open injury, so the victim’s pants should be

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Figure 24-44. A 12-year-old skier sustained this closed, midshaft femur fracture when he struck a tree.The anteroposterior view shows that the patient is on a backboard and in traction.

A

B

split to complete the examination. Discovery of an open wound should prompt rapid evacuation. Fracture of the distal end of the femur is frequently intraarticular and occurs with high-velocity loading when the knee is flexed. With axial loading on the femur, the patella becomes the driving wedge and the femoral condyles suffer direct impact, producing either a patella fracture or a fracture of the femoral condyles or distal femoral metaphysis. Occasionally, in highenergy trauma, a distal femur fracture and an ipsilateral proximal tibia fracture can occur concurrently (Fig. 24-45). With a patella fracture, the injury may be obvious on deep palpation. This is often an open injury because there is very little soft tissue overlying this sesamoid bone. The definitive diagnosis is made radiographically. After initial neurocirculatory examination, the limb is realigned to avoid compression of the popliteal artery and vein. A posterior splint is applied to the realigned limb for transportation. As with all fractures, open wounds in the region of the fracture or an abnormal nerve or vascular examination should prompt immediate evacuation.

Tibia and Fibula The tibial plateau is the broad intra-articular surface of the upper tibia that articulates with the distal femur. This area can be fractured in a fall or leap from a height (Fig. 24-46). A valgus moment of force produces a fracture of the lateral tibial plateau, whereas a varus moment of force produces a medial plateau fracture. Pain, swelling, and deformity are obvious on initial examination. With a tibial plateau fracture, significant hemarthrosis develops quickly. Because of anatomic tethering of the popliteal artery by fascia of the soleus complex, arterial injury may result from this fracture, especially when it is associated with a knee dislocation. Distal pulses and capillary refill should be assessed at 1-hour intervals. After initial exam-

ination, the limb is carefully realigned, and a posterior splint is applied for transportation. Tibial shaft fractures are associated with fibular shaft fractures in 90% of cases. These fractures result from high-impact trauma. Before the development of higher, anatomically conforming ski boots, these fractures were the most common ski injuries (Fig. 24-47). The injury was sustained when the body rotated around a fixed foot (occurring with a ski caught against a rock or tree stump), which produced a torsional, spiral fracture of the tibia and fibula. Tibial shaft fracture is the most common type of open fracture in the wilderness setting. When this injury is suspected, the entire limb should be inspected for distal sensory, motor, and circulatory function before realignment. A posterior splint is applied for transport. As this is the most common anatomic location for this problem, the limb is serially examined for the possibility of a compartment syndrome.

Ankle The intra-articular distal tibia, medial malleolus, and distal fibula, or any combination of these, may be involved in an ankle fracture, which is generally produced by large torsional moments of force about a fixed foot. With the distal tibia fracture, axial loading from a fall or jump may also be involved. Any significant pain and swelling should be noted as the shoe is removed. Palpation along the medial and lateral malleoli confirms the clinical suspicion. After the shoe is removed to inspect the skin for open wounds, a neurocirculatory examination is performed. If there is a rotational deformity in the ankle, the ankle is realigned with gentle traction before applying a posterior splint with the ankle in neutral position. During transport, the limb is elevated above the level of the heart.

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Figure 24-45. In higher-energy trauma,fractures of adjacent long bones can occur.These distal femur and proximal tibia fractures create the highly unstable situation of a “floating knee.” Adequate and secure splinting is imperative to avoid further damage to neurovascular or soft tissue structures.

Figure 24-46. Anteroposterior and lateral plain radiographs of a tibial plateau fracture that occurred as a result of a fall.When a high-energy knee or lower extremity injury is sustained, always check for pulses, sensation, motor function, and indicators of compartment syndrome, such as pain with passive stretch.

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Figure 24-47. Anteroposterior and lateral plain radiographs of the distal tibia of a 30-year-old man after a twisting injury. This fracture should be well immobilized in a short leg splint, and the victim should be evacuated.

Figure 24-48. A talar neck fracture, when suspected, should be treated as an emergency. Restoration and fixation of alignment provides the greatest chance for maintenance of the tenuous blood supply of the talar dome.

Tarsal Bones The calcaneus and talus are usually fractured during falls or jumps from significant heights when the victim lands on his or her feet. With a calcaneus fracture, significant heel pain, deformity, and crepitus are immediately evident after the boot is removed. A talus fracture may be impossible to differentiate from an ankle fracture on clinical grounds. An ankle fracture is tender at the malleolus level, whereas with a talus fracture, the tenderness is located distal to the malleoli. Talus fracture usually occurs when the foot is forced into maximal dorsiflexion. Knowing the point of the foot’s impact with the ground is helpful in differentiating a talus fracture from an ankle fracture (Fig. 24-48). Talus fracture may be associated with subtalar or ankle joint dislocation. Emergency evacuation should be arranged when this injury is suspected because these injuries are very difficult to reduce closed, and pressure on the skin from the displaced talar body can produce significant skin slough. If a talar neck fracture is suspected (admittedly difficult to diagnosis without plain radiograph), immediate evacuation is indicated; the blood supply to the talar dome, in part via the talar neck, is tenuous (Fig. 24-49). Therefore, to prevent post-traumatic avascular necrosis that may result from the fracture and disrupted blood supply, expedited evacuation is indicated. Fractures of the other tarsal bones are exceedingly rare but can be defined by localizing the tenderness to a specific site. A short-leg splint with extra padding is applied and the limb is elevated during transportation.

Figure 24-49. The talar blood supply.The talus receives contributions from the dorsalis pedis, posterior tibial artery, and perforating peroneal artery. (Redrawn from Myerson MS: Foot and Ankle Disorders. Philadelphia,WB Saunders, 2000, p 1325.)

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Figure 24-50. The Allis technique for reduction of a hip dislocation. The surgeon’s position must provide a mechanical advantage for the application of traction. A, Internal and external rotations are gently alternated,perhaps with lateral traction by an assistant on the proximal thigh. B, In-line traction with hip flexed. C, Adduction is often a helpful adjunct to in-line traction.(A to C redrawn from DeLee JC: In Rockwood CA Jr, Green DP: Fractures, vol 2, 2nd ed. Philadelphia, JB Lippincott, 1985.)

A

Metatarsal Bones Fractures at the base of the metatarsals often accompany midfoot dislocation (Lisfranc dislocation). The mechanism usually occurs with axial loading of the foot in maximal plantar flexion as a result of vehicle crash, most frequently snowmobiling. The victim complains of midfoot pain and swelling. On removing the shoe, crepitus and tenderness are noted at the base of the metatarsals (especially the first, second, and fifth metatarsals) and plantar ecchymosis may be present. Overall foot alignment is maintained, but stressing the midfoot by stabilizing the heel and placing force across the forefoot in the varus and valgus directions reveals instability. The foot is placed in a well-padded posterior splint and elevated whenever possible. The patient is not allowed to ambulate. Swelling associated with Lisfranc dislocation can produce a compartment syndrome. Metatarsal shaft fracture occurs with a crush injury or a fall or jump from moderate height. Midshaft metatarsal fractures also occur as “fatigue” (or “march”) fractures, which often result from prolonged hiking or running with poor preconditioning. Pain and localized tenderness are the hallmarks of this diagnosis. The dull pain at the midshaft of a metatarsal (often the second or fifth) may be converted to more severe pain with associated crepitus by a jump from a log or a rock. These fractures can be temporarily managed with a stiff-soled boot or orthotic insert. If there is fracture instability or extreme pain, a short-leg splint is applied and no further weight-bearing is allowed until more definitive evaluation and treatment can be accessed.

Phalanx Toe phalanges are usually fractured by crush injuries that can be prevented by the use of steel-toed or hard-toed boots. A great-toe phalanx fracture can be a significant problem because force is placed on this digit during the toe-off phase of gait. Phalanx fractures are managed by buddy taping the toe to an adjacent uninjured digit with cotton placed between the toes. Displaced intra-articular fracture of the proximal phalanx of the great toe may need operative fixation. Stiff-soled boots minimize discomfort during weight bearing.

B

C


LOWER EXTREMITY

DISLOCATIONS AND SPRAINS

Hip Posterior hip dislocation is produced by axial loading of the femur with the hip flexed and adducted.7 It generally occurs in a vehicle crash but can follow a fall or a sledding or skiing accident. With posterior dislocation, the victim complains of severe pain about the hip and the affected limb appears shortened, flexed, internally rotated, and adducted. Any hip motion increases the pain. It is not clinically possible to determine if there is an associated acetabular or femoral neck fracture. With the rare anterior dislocation, the limb is externally rotated, slightly flexed, and abducted. This type of dislocation is generally produced by wide abduction of the hip caused by significant force. The victim is placed in the supine position for a complete survey of all organ systems. The distal limb is carefully examined for associated fractures, and a thorough sensory and motor examination is performed. The peroneal division of the sciatic nerve is most susceptible to injury with a posterior dislocation. Hip dislocations are an orthopaedic emergency because time to reduction is directly linked to the incidence of avascular necrosis of the femoral head. Immediate transfer to a definitive care center is desirable because hip radiographs may reveal an associated femoral neck fracture that could become displaced if closed reduction is attempted. However, if it will be more than 6 hours before the victim can be evacuated to a definitive care center, closed reduction should be attempted. To perform the Allis technique (Fig. 24-50), the victim is positioned supine on the ground or a stretcher. Analgesic medication is administered, if available. The caregiver stands above the victim and applies in-line traction on the extremity while an assistant applies counter-traction to the iliac wings. Posterior dislocations are reduced by flexing the hip 60 to 90 degrees. Internal rotation and adduction of the hip facilitates the reduction. With anterior dislocation, traction is applied with the leg slightly abducted and externally rotated and the hip gently extended. Successful reduction is usually indicated by an audible “clunk” and restoration of limb alignment. As with any reduction

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Figure 24-51. The Stimson gravity reduction technique. This method has limited application in patients with multiple injuries. (Redrawn from DeLee JC: In Rockwood CA Jr, Green DP: Fractures, vol 2, 2nd ed. Philadelphia, JB Lippincott, 1985. Copyright © 1990 by Jesse C. DeLee.)

maneuver, adequate analgesia and a slow, progressive increase in traction force are helpful. For the Stimson gravity technique (Fig. 24-51), which may not be as practical in the wilderness, the patient is positioned prone on a makeshift platform. With a posterior dislocation, the hip and knee are flexed 90 degrees. Longitudinal traction is applied in addition to adduction and internal rotation. The reduction maneuver is actually the same for both techniques, but one is performed with the victim supine and the other with the victim prone.

Knee Knee dislocation is usually obvious because of the amount of deformity (Fig. 24-52). The tibia may be dislocated in one of five directions: anterior, posterior, lateral, medial, or rotatory. The most common directions are anterior and posterior. This represents a true emergency because 5% to 40% of knee dislocations have associated vascular injuries.1,15,19 In a large series, Green and Allen6 reported an above-knee amputation rate of 86% for vascular injuries associated with knee dislocations that were not repaired within 8 hours of injury. The vascular injury occurs because of tethering of the popliteal vessels along the posterior border of the tibia by the soleus fascia. A knee dislocation is a high-velocity injury usually produced by a vehicle crash or a fall. When this injury is suspected, a careful screening neurocirculatory examination must be performed. Intact distal pulses do not definitively rule out an arterial injury. Intimal flap tears can produce delayed thromboses of the popliteal artery. In addition, injury to the peroneal nerve can occur. Many knee dislocations spontaneously reduce and may lead the examiner to underestimate the seriousness of the injury. Instability in extension to either varus or valgus stress indicates disruption of at least one of the cruciate ligaments and signifies the potential for a knee dislocation. After the initial examination, the persistent dislocation should be reduced. Anterior dislocation is reduced with traction on the leg and gentle elevation of the distal femur. Posterior dislocation is reduced with traction in extension and anterior elevation of the tibia. Posterolateral rotatory dislocation can be very dif-

Figure 24-52. Anterior knee dislocation.Significant attention should be devoted to relocation, if possible,and to assessment of the neurovascular structures that run posterior to the knee joint, such as the popliteal artery and the tibial and common peroneal nerves.

Chapter 24: Wilderness Orthopaedics ficult to reduce and usually requires open reduction. It occurs when the medial femoral condyle buttonholes through the medial capsule. A transverse furrow on the medial aspect of the knee is pathognomonic for this injury. For transport, a posterior splint is applied to the limb and the victim is moved on a backboard. The possibility of an arterial lesion or emerging compartment syndrome requires vigilance. Emergency evacuation is advised because of the risk of amputation related to vascular injury. Frequently, the patellofemoral joint is dislocated. Because of the increased femorotibial angle in females, this injury is far more common in women. Generalized ligamentous laxity may also predispose to this problem. Dislocation of the kneecap may result from a twisting injury or an asymmetric quadriceps contraction during a fall. These mechanisms routinely occur with hiking, climbing, and skiing accidents. The patella dislocates to a position lateral to the articular surface of the distal femur. Although neurovascular injuries rarely occur in association with a dislocated patella, a screening examination should be conducted. The patella can often be reduced by simply straightening the knee. If this is not successful, gentle pressure is applied to the patella to push it back up onto the distal femoral articular groove. A knee splint is applied with the joint in extension; weight bearing is allowed. The knee is kept in extension until definitive care can be obtained. A radiograph is ultimately required to rule out osteochondral fractures, which are frequently associated with this injury.

Ankle Ankle dislocations are almost always accompanied by fractures of one or more malleoli. These dislocations generally occur with falls onto uneven surfaces or with twisting injuries of moderate velocity. The area about the ankle is carefully examined for open injuries, and a neurocirculatory examination is conducted to obtain a baseline status. Then, the ankle joint is aligned by grasping the posterior heel, applying traction with the knee bent (to relax the gastrocnemius–soleus complex), and bringing the foot into alignment with the distal tibia. After this maneuver, the foot is reexamined, any wounds are dressed, and a posterior splint is applied. During transport, the limb is elevated above the level of the heart. The most common musculoskeletal injury occurring in the wilderness setting is an ankle sprain. Ligament sprain, or tearing of the fibers, is separated into three grades. Grade 1 injury is partial disruption of some of the ligament fibers. Grade 2 injury is complete disruption of a portion of the ligament fibers. The main substance of the ligament remains intact, and the injury is characterized by moderate hemorrhage with grossly visible torn ligament fibers. Grade 3 injury is complete disruption of the ligament fibers, which can result in instability of the ankle joint. The medial ligament complex consists of the deltoid ligament, which runs from the medial malleolus to the talus (Fig. 24-53). The ligament complex on the lateral side is much more intricate and consists of three separate ligaments named for their origins and insertions: the calcaneofibular ligament, the anterior talofibular ligament, and the posterior talofibular ligament (see Figure 24-53). The lateral ligament complex is the most frequent site of an inversion injury. When such an injury occurs, the shoe and sock are removed and a screening neurocirculatory examination is conducted. Each ligament is palpated

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individually for tenderness, and the ankle is evaluated for instability with the anterior drawer test. This test is performed by stabilizing the tibia with one hand and grasping the posterior heel to pull the foot forward with the other hand. If the talus slides forward within the ankle mortis (using the uninjured side as a comparison), the injury represents a grade 3 injury. The foot and ankle are placed into a posterior splint or air splint. If possible, the victim is kept from bearing weight on the limb. If this examination does not reveal instability and is thus indicative of a grade 1 or 2 sprain, an elasticized bandage is applied or the ankle is taped (see Chapter 18). All injuries should be acutely treated following the RICE principle. Commercially available stirrup air splints also aid in ambulatory management of these injuries. A more serious ankle sprain is the high ankle sprain, which affects the anterior inferior tibiofibular ligament (a portion of the syndesmotic ligament) and occurs in up to 10% of ankle sprains. The victim complains of pain to palpation over the distal tibiofibular joint and also with dorsiflexion and external rotation of the foot relative to the tibia. Compression of the fibula and tibia in the proximal half of the calf produces pain over the syndesmosis. Unlike stable lateral ankle sprains, these injuries take 4 to 6 weeks to resolve. Initial treatment is with a short-leg splint or walking boot. Failure to recognize this injury will produce prolonged disability. In the field, the ankle is taped both to decrease pain and to limit swelling (Fig. 24-54, and see Chapter 18). During taping, the victim’s ankle is kept perpendicular to the tibial shaft. This makes walking easier, because the ankle is not plantar flexed, and helps prevent development of an Achilles tendon contracture. If available, an Aircast ankle brace provides additional ankle support and can be used with a shoe or boot. A fracture of the lateral process of the talus, which is a fairly common lower extremity fracture in snowboarders, may be confused with a lateral ankle sprain, so radiographs are generally needed to rule out this injury.9 Inversion injuries are also infrequently associated with fractures at the insertion of the peroneus brevis tendon. This injury can be identified by the point tenderness at the base of the fifth metatarsal, but a radiograph is required for definitive diagnosis. Early management is the same as for an ankle sprain.

Hindfoot The subtalar joint may infrequently be dislocated in a significant fall or jump when an individual lands off balance or on an uneven surface. The calcaneus may be dislocated medially or, more commonly, laterally relative to the talus (Fig. 24-55). The position of the heel relative to the ankle is assessed. With either dislocation, a reduction is attempted if it will be more than 3 hours until the victim will reach a definitive care center. Medial dislocation is reduced more easily than lateral dislocation, in which the posterior tibial tendon frequently becomes displaced onto the lateral neck of the talus, blocking the reduction. The maneuver is the same for both: the heel is grasped with the knee flexed (relaxing the gastrocnemius–soleus complex), the deformity is accentuated, linear traction is applied, and the heel is brought over to the ankle joint. This maneuver is generally successful for medial dislocation, but lateral dislocation, especially when associated with open wounds, often requires open treatment. After reduction is attempted, a posterior splint is applied and the limb is elevated

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Anterior inferior tibiofibular ligament Anterior talofibular ligament

Posterior talofibular ligament Calcaneofibular ligament

Tibiocalcaneal ligament

Lateral ankle Posterior tibiotalar ligament

Tibionavicular ligament

Medial ankle

Figure 24-53. Ligament complexes of the ankle.

above the heart. Even if the reduction is successful, the victim must not be allowed to bear weight until definitive care is obtained.

Midfoot Midfoot fracture dislocation (Lisfranc injury) is described in the metatarsal fracture section.

A

B

C

Figure 24-54. Taping a sprained ankle.Strips of adhesive tape are placed perpendicular to each other (A) to lock the ankle with a tight weave (B). The tape edges are covered to prevent peeling (C). (From Auerbach PS: Medicine for the Outdoors: The Essential Guide to Emergency Medical Procedures and First Aid, 4th ed. Guilford, CT, Lyons Press, 2003.)

Metatarsophalangeal and Interphalangeal Joints Metatarsophalangeal (MTP) joint dislocations of the toes are relatively uncommon but can occur when a moderate axial force is directed at the great toe. Crush injuries and rock-climbing accidents while the victim is wearing flexible-sole shoes can produce this injury; wearing boots with reinforced toe boxes of adequate depth generally prevents it. Injuries of this type at the great toe may be associated with fractures of the metatarsal joint or phalanx. The dislocation is generally dorsal. Because these may be open injuries, the foot must be inspected carefully. The joint is reduced in a manner similar to that used for dorsal

Chapter 24: Wilderness Orthopaedics

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Posterior cruciate ligament Lateral collateral ligament Lateral meniscus

Biceps femoris Tibiofibular ligament Insertion of patellar tendon

Ligament of Humphry Anterior cruciate ligament Medial meniscus Medial collateral ligament Pes anserinus: Sartorius Gracilis Semitendinosus

Figure 24-56. Anterior view of a partially dissected knee joint. (Redrawn from Insall JN, Scott WN [eds]: Surgery of the Knee, 2nd ed. New York, Churchill Livingstone, 1993, p 2.)

Figure 24-55. Ankle and hindfoot of a man with a calcaneus fracture. Soft tissue swelling from a fracture or crush injury can result in swelling that contributes to a compartment syndrome.

PIP joint dislocation of the hand. MTP dislocation of the great toe can occasionally require open reduction if the head of the metatarsal buttonholes through the sesamoid–short flexor complex. The lesser MTP joints are generally dislocated laterally or medially. The most common mechanism for this injury is striking unshod toes on immovable objects. The toes are relocated by applying linear traction with the victim supine and using the weight of the foot as countertraction. Similar mechanisms produce dislocations of the IP joints, which are also reduced by applying linear traction with gentle manipulation. Once reduced, the injured toe is taped to the adjacent toe for 1 to 3 weeks, and the victim wears a protective boot with a stiff sole and deep toe box.


OTHER SOFT TISSUE AND

MUSCULOSKELETAL INJURIES

Intra-articular Knee Disruption Sprains or ruptures of ligaments about the knee (Fig. 24-56) are common occurrences in sporting events and in vigorous activities. They often involve a sudden fall or a twisting mechanism. Anterior cruciate ligament (ACL) injuries often result from twisting or pivoting, or from hyperextension. The individual who sustains this injury often sustains concomitant knee injuries, such as a meniscus tear or an injury to another ligament in the knee. Tearing of the ACL may be accompanied by the sound of a pop in the knee. Usually, but not always, the knee becomes swollen. A sense of instability is common. On examination, there may be marked laxity to anterior stress on the tibia relative to the femur (Lachman test).

Although it may be easy to produce mobilization in extension, ACL injuries do not necessarily require immobilization. If the mechanism of the injury suggests that it is more likely to be ligamentous than a fracture, weight bearing, as tolerated, and range of motion, as tolerated, are safe recommendations. Nonsteroidal anti-inflammatory drugs (NSAIDs), compression dressing, and ice, if it is available, are all palliative and might enhance the victim’s ability to leave the wilderness setting and obtain more definitive diagnosis and treatment. An individual who incurs an ACL tear might also sustain a posterior cruciate ligament (PCL) injury, an MCL injury, or a lateral cruciate ligament (LCL) injury. Sprain or frank disruption of any of these ligaments may result in a sense of instability in the plane controlled by that ligament (for example, valgus instability in the setting of an MCL injury). Meniscal tears in the setting of a ligamentous injury are common. Some tears—called bucket-handle tears—become caught in the joint. These can result in a locked knee. Manipulative procedures have been described for liberating an incarcerated meniscal fragment. However, unless evacuation is substantially hindered by the locked knee, it is generally better to get the injured individual as quickly as possible to a facility that can provide a magnetic resonance imaging (MRI) study. Sometimes, surgery is the sole solution for this problem.

Achilles Tendon Rupture Achilles tendon ruptures are fairly common in the 35- to 55year age group. These injuries usually occur as an individual applies an eccentric load to the calf and Achilles tendon. The affected individual often feels as though he has been struck by a baseball bat at the posterior aspect of the ankle. Active plantar flexion is impossible. In the Thompson squeeze test, the injured person kneels on an elevated surface without sitting on the haunches and allows the feet to hang over the edge of the surface. Squeezing the calf does not result in an involuntary plantar flexion on the injured side. This lack of motion suggests that there is no connection between the gastrocnemius and soleus muscle bellies and the Achilles attachment to the calcaneus.

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If a short-leg splint can be applied as a temporizing measure, this should be done. The affected individual may bear weight as tolerated. This injury may be treated with or without surgery.

Hamstring Pull or Tear A hamstring pull or tear can occur when there is a hyperflexion mechanism applied to the hip simultaneously with a hyperextension mechanism to the leg. This can also occur as an overuse injury. Generally, the best way to treat this is to apply ice, stretch gently, and bear weight, as tolerated.

Effusions Joint or bursal effusions occur when there is excess production of synovial fluid. Effusions may result from trauma (for example, hemarthrosis as a result of an ACL tear, or lipohemarthrosis as the result of a tibial plateau fracture). If an effusion can be aspirated under sterile conditions in the wilderness, aspiration may be of value for comfort and for diagnosis. If it is not possible to perform aspiration under sterile conditions, the effusion should be treated with NSAIDs, compression dressing, and application of cold.


OVERUSE SYNDROMES Overuse syndromes that affect the musculoskeletal system are a very common form of injury in the wilderness.

Plantar Fasciitis Plantar fasciitis is inflammation of the fascia (the tough connective tissue) on the sole of the foot. An individual with plantar fasciitis complains of insidious onset of pain at the origin of the plantar fascia, which is located at the most anterior aspect of the heel pad. Any activities that stretch the plantar fascia elicit pain. The pain is worst when first getting up in the morning or after resting, and it is accentuated when the ankle and great toe are dorsiflexed (e.g., during push-off). Conservative treatment consists of (1) heel cord stretching 20 minutes twice a day, (2) NSAIDs, and (3) wearing an orthotic that cups the heel, has a soft spot under the tender area, and supports the arch. It may take several weeks for symptoms to improve, but conservative therapy is successful in 90% of cases. An ankle–foot splint worn at night may help because it holds the foot in a neutral position, keeping the plantar fascia slightly stretched. The

orthosis also provides significant pain relief if used while walking. In severe cases, taping the arch can provide pain relief (Fig. 24-57). A thin layer of benzoin or spray tape adhesive is applied to the bottom of the foot. An anchor strip of 3/4-inch adhesive tape is fixed in a U shape around the heel from just under the malleoli (the prominences of the ankles) up to just behind the level of the “knuckles” of the toes (see Figure 24-57A). Next, fairly tight cross-strips of 1/2-inch tape are laid across the bottom of the foot, with their ends torn to lie on the anchor strip (see Figure 24-57B). This creates a “sling” of tape under the foot for support. Finally, another U-shaped piece of tape is applied around the heel; it crosses under the center of the arch and locks down the crosspieces (see Figure 24-57C).

Carpal Tunnel Syndrome Carpal tunnel syndrome (CTS) occurs when the median nerve is compressed within the carpal tunnel (Fig. 24-58). The carpal tunnel, located on the palmar side of the wrist, is formed by the transverse carpal ligament volarly and the carpal bones dorsally. The flexor digitorum profundus and superficialis tendons to the second through fifth digits, the long thumb flexor, and the median nerve pass through this canal. Individuals with CTS complain of pain and paresthesias along the palmar aspect of the radial digits. They also complain of frequently dropping objects. Symptoms are worse at night and aggravated with prolonged wrist extension or flexion. The Phalen sign, which is numbness and tingling in the median nerve distribution after sustained wrist flexion, is suggestive of CTS. Thenar muscle atrophy is seen only in severe cases. Other causes should be considered, such as more proximal sites of nerve compression (especially the cervical spine), dialysis, pregnancy, and acute or chronic trauma. Treatment consists of wrist splinting in slight extension (especially at night), activity modification, and NSAIDs.

Tibial Fatigue Fractures Tibial fatigue fractures can occur in individuals who suddenly increase their activity. Victims complain of pain with weight bearing, swelling, tenderness to palpation, and increased warmth at the fracture site. The most common site in the tibia is the proximal two thirds of the tibial diaphysis. Stress fracture of the distal third of the fibula can also occur. Treatment consists of activity reduction, protective weight bearing, and avoidance of activities that produce pain. Failure to decrease activity level complicates fracture of the tibia. As the pain subsides, the activity level can be increased. Two to 3 months may be required for resolution of symptoms.


EVACUATION DECISION

A

B

C

Figure 24-57. Taping for arch support. A, Fix an anchor strip under the heel. B, Attach strips across the bottom of the foot.C, Lock the crosspieces.(From Auerbach PS:Medicine for the Outdoors: The Essential Guide to Emergency Medical Procedures and First Aid, 4th ed. Guilford, CT, Lyons Press, 2003.)

The decision to evacuate an orthopedically injured individual depends on the goals of and the support available to the expedition. The criteria for evacuation of an injured person in a family of four spending a week hiking in the Rockies differ from those of a group of 25 climbers in the Himalayas with physician support and a field hospital at the base camp. In all cases, party leaders should have a plan for contacting evacuation support teams if a serious injury occurs. Musculoskeletal injuries that warrant immediate evacuation to a definitive care center are listed in Box 24-2. These include

Chapter 24: Wilderness Orthopaedics

Hypothenar muscles

Thenar muscles

Figure 24-58. Anatomic basis of carpal tunnel syndrome. A, General view of the relationship between the median nerve and the flexor retinaculum. B, Cross section at the distal carpal row, showing the structures in the carpal tunnel.(Redrawing based on an illustration by Li-Guo Liang, in Yu HL, Chase RA, Strauch B: Atlas of Hand Anatomy and Clinical Implications. Philadelphia, Mosby, 2004, p 513.)

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Median nerve

Transverse carpal ligament Palmar carpal ligament

A Median nerve Tubercle of the trapezium

Tendon of the flexor carpi radialis

Superficial branches of the ulnar vein, artery, and nerve Palmar carpal ligament

Transverse carpal ligament Tendons of the flexor digitorum superficialis Deep branches of the ulnar vein, artery, and nerve Hook of the hamate

Tendon of the flexor pollicis longus

Tendons of the flexor digitorum profundus

B

Box 24-2. Indications for Emergent Evacuation Suspected spine injury Suspected pelvic injury Open fracture Suspected compartment syndrome Hip or knee dislocation Vascular compromise to an extremity Laceration with tendon or nerve injury Uncertainty of severity of injury

any suspected cervical, thoracic, or lumbar spine injury. A victim who has a suspected pelvic injury with posterior instability, possibly significant blood loss, or injury to the sacral plexus should be emergently evacuated on a backboard. Any

open fracture requires definitive debridement and care within 8 hours to prevent development of deep infection, so it should prompt emergency evacuation. Victims with suspected compartment syndromes must be evacuated on an emergency basis. Joint dislocations involving the hip or knee warrant immediate evacuation because of the associated risk of vascular injury or post-traumatic avascular necrosis of the femoral head. Lacerations involving a tendon or nerve warrant urgent evacuation to a center where an extremity surgeon is available. In all but the most serious wilderness expeditions, arrangements should be made to evacuate the victim when the treating individuals are not reasonably sure of the injury with which they are dealing or its appropriate management.

The references for this chapter can be found on the accompanying DVD-ROM.

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25

The Eye in the Wilderness Frank K. Butler, Jr.

This chapter considers several commonly encountered types of eye disorders: periocular trauma; chemical injury to the eye; sudden vision loss in a white, quiet eye; acute orbital and periorbital inflammation; and the acute red eye. A diagnostic and therapeutic approach to these disorders suitable for the wilderness environment is presented. Finally, eye problems that are encountered in diving and altitude exposures are discussed.


PRELIMINARY PLANNING Pertinent ocular items in a preliminary medical survey include contact lens wear; previous episodes of nontraumatic iritis; previous episodes of herpetic keratitis; and a history of corneal transplantation, retinal detachment, refractive surgery, or other ocular surgery. A positive response to these questions may alert the health care professional to specific ocular problems that may be encountered on the proposed trip. Congenital color vision deficiencies are common in the male population (8% in whites)27 and typically pose no functional problems in the wilderness. In addition to reviewing ocular health in the medical survey, a basic wilderness eye kit should be assembled and taken on the trip, as described in the next section.


THE WILDERNESS EYE EMERGENCY KIT

Box 25-1 lists the suggested items for a basic wilderness ocular emergency kit. A topical fluoroquinolone, such as moxifloxacin, is the antibiotic eye drop of choice. These medications are preferred for treatment of bacterial keratitis in a wilderness setting. Topical tetracaine and fluorescein strips are important for diagnosis. Topical prednisolone is an excellent ocular antiinflammatory medication. The choice of an oral antibiotic is based on the efficacy of the proposed antibiotic in treating preseptal cellulitis, orbital cellulitis, and penetrating trauma to the globe. The fluoroquinolone family of antibiotics offers several good choices for these indications. The new fourth-generation fluoroquinolone moxifloxacin provides good coverage against gram-positive, gram-negative, and anaerobic organisms, with a relatively mild side effect profile and once-daily dosing, and is the recommended first-line oral antibiotic.92 Gatifloxacin has recently been withdrawn from the market because of dysglycemic side effects. Trovafloxacin (500-mg tablets) is a systemic fluoroquinolone with excellent coverage against gram-positive, gramnegative, and anaerobic bacteria.54,130 It also offers the

convenience of once-daily dosing, but there have been a number of unpublished reports of hepatotoxicity with trovafloxacin that limit the usefulness of this medication.98 Levofloxacin (500-mg tablets) is another systemic fluoroquinolone with very good activity against a wide variety of gram-positive and gramnegative organisms but less anaerobic coverage than trovafloxacin.98 Ciprofloxacin has been shown to have excellent ocular penetration when given orally,73 but is less efficacious against gram-positive organisms than is levofloxacin. Bacitracin is an antibiotic ointment suitable for use in patching corneal abrasions. Ophthalmic ointments are best applied by using downward pressure on the lower lid to pull it away from the eye and then applying a 1-cm (0.4-inch) ribbon of ointment to the conjunctiva of the lower lid. When released, the lid returns to its normal position and normal blinking distributes the ointment over the corneal surface. Oral prednisone has three possible treatment uses in the wilderness—refractory iritis, giant cell arteritis, and orbital pseudotumor. Topical scopolamine (0.25%) is used to reduce ciliary muscle spasm, which causes much of the discomfort associated with iritis and corneal abrasion. Scopolamine, however, has the disadvantage of dilating the pupil (making the eye very sensitive to bright light) and preventing accommodation (making reading very difficult) for 5 to 7 days. Artificial tears are used to treat ocular surface drying and to flush conjunctival foreign bodies from the eye. Artificial tears are a better choice for these symptoms than are ophthalmic preparations containing vasoconstrictors because ocular decongestants have been shown to cause both acute and chronic conjunctivitis.124 Diclofenac 0.1% drops have been shown to decrease corneal sensitivity, especially when multiple drops are used.112,128,129 They have been found helpful in reducing the discomfort associated with traumatic corneal abrasion60 and excimer laser refractive surgery.40,131,135 In the unlikely event of angle-closure glaucoma in a wilderness setting, 2% pilocarpine may be used. The medications in Box 25-1 are listed in my recommended priority order. In the spirit of making do in the wilderness, all of the disorders mentioned in this chapter can be managed with only the aforementioned medications, but alternative therapies are also discussed. Many individuals suffer from seasonal allergies, including allergic conjunctivitis, that may be exacerbated in the wilderness. Adding olopatadine 0.1%, lodoxamide 0.1%, nedocromil 2%, or ketotifen 0.025% to the wilderness eye kit provides treatment options for allergic conjunctivitis.70 Because this condition is often a chronic one, however, individuals often carry their own medications on trips.

Chapter 25: The Eye in the Wilderness

Box 25-1. The Wilderness Eye Emergency Kit MEDICATIONS

Moxifloxacin 0.5% drops Tetracaine 0.5% drops Prednisolone 1% drops Moxifloxacin 400 mg tabs Levofloxacin 500-mg tabs Bacitracin ointment Prednisone 20-mg tabs Artificial tears Scopolamine 0.25% drops Diclofenac 0.1% drops Pilocarpine 2% drops MISCELLANEOUS

Penlight with blue filter Fluorescein strips Cotton-tipped applicators Metal eye shield Eye patches (gauze) Tape (1 inch, plastic or nylon) Near vision card Wound closure strips (1/4 inch) Magnifying glass


VISUAL ACUITY MEASUREMENT IN THE WILDERNESS

Evaluation of visual acuity is an essential element of the eye examination. Serial measurements of visual acuity are used to monitor an individual’s progress while being treated for an eye disorder. Lack of an eye chart does not preclude the ability to obtain some quantitative measure of visual acuity. A near-vision card can be used for this purpose. It should be held the prescribed distance—usually 35 cm (14 inches)—from the eye. If a near card is not available, the ability to read print in a book is a useful alternative measure. If glasses have been lost, use a piece of paper with a pinhole created by the tip of a pen or pencil to help compensate for the lost refractive correction. Remember that individuals 40 years of age and older may need a pinhole or reading correction to help them focus on a near target. Although a marked decrease in visual acuity can be an important warning of a significant ocular disorder, visual acuity cannot always be considered a reliable indicator of the severity of disease. A corneal abrasion victim may initially have worse visual acuity than a person with a retinal detachment or corneal ulcer, despite the fact that the latter two entities are much more serious disorders.


GENERAL THERAPEUTIC APPROACH

The recommendations made in this chapter are not necessarily the preferred management of the disorders mentioned when one is not in the wilderness setting. Of special interest is the recommendation for a nonophthalmologist to use a topical steroid

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Box 25-2. Differential Diagnosis of Acute Periocular Inflammation Preseptal cellulitis Orbital cellulitis Dacryocystitis Orbital pseudotumor Insect envenomation

in the management of several of the disorders discussed. The use of topical ocular steroids is generally best undertaken by ophthalmologists for two reasons: first, steroids are usually indicated only for relatively serious ocular disorders, which should be followed by an ophthalmologist when possible. Second, topical steroid use may result in elevated intraocular pressure, cataracts, and exacerbation of certain eye infections. All of the disorders for which steroids are recommended in this chapter should be referred to an ophthalmologist for follow-up as soon as possible on return from the wilderness. Caution should be exercised in prescribing a topical steroid for longer than 3 days. Although cataracts are typically associated with long-term steroid use, a significant rise in intraocular pressure may occur within just a few days after initiation of topical steroid therapy.70 The requirement for expedited evacuation is one of the questions that must be answered when treating an eye disease in the wilderness. In the following sections, the need for evacuation may be considered nonurgent unless an emergent (as soon as possible) or expedited evacuation (as soon as is deemed reasonable given the resources required to accomplish the evacuation) is specified in the recommendations for treatment.


ACUTE PERIOCULAR INFLAMMATION

Causes of acute periocular inflammation are listed in Box 25-2. Preseptal cellulitis means that the infectious process is confined to the tissues anterior to the orbital septum. Preseptal cellulitis therefore presents as erythema and edema of the eyelids without restricted ocular motility, proptosis, pupillary change, or decrease in visual acuity. However, some of these findings may be difficult to appreciate in the presence of marked lid edema. Historical clues include antecedent periocular trauma or insect bite or sting. In the past, this disorder has been treated very aggressively because of the high incidence of Haemophilus influenzae infection, especially in pediatric patients, with subsequent septicemia and meningitis. The advent of H. influenzae type B vaccine has changed the microbiology of this disorder and may dictate changes in treatment strategies in the future.31 Persons who present with this disorder may be treated with moxifloxacin 400 mg once a day and should have an expedited evacuation. Alternative antibiotic choices include levofloxacin 500 mg once a day, ciprofloxacin 750 mg twice a day, dicloxacillin 500 mg every 6 hours, or cephalexin 500 mg four times a day. Dacryocystitis (infection of the lacrimal sac) may mimic the findings of preseptal cellulitis, but erythema, edema, and tenderness are localized to the area inferior to the medial aspect of

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the eye, over the nasolacrimal sac and duct. The presence of this condition usually indicates obstruction in the opening between the lacrimal sac and the nasal cavity. Surgical intervention to restore the patency of this opening is usually undertaken after the acute infection is treated. The most common pathogens in acute dacryocystitis are Staphylococcus aureus, Streptococcus species, and (in children) H. influenzae.91 Treatment should be initiated with moxifloxacin 400 mg once a day and warm compresses. Alternative antibiotic choices include levofloxacin 500 mg once a day, ciprofloxacin 750 mg twice a day, or amoxicillin/clavulanate 875 mg/125 mg every 8 hours. Worsening of the condition after 24 to 48 hours should be managed with an expedited evacuation. Periocular insect envenomation is a preseptal cellulitis lookalike. Although secondary infection may follow envenomation, the envenomation itself may produce significant erythema and edema. Diagnostic clues include a history of insect bite or a periocular papular lesion at the site of the envenomation. Ice or cool compresses may be used to treat the envenomation, with moxifloxacin 400 mg once a day, levofloxacin 500 mg once a day, dicloxacillin 500 mg every 6 hours, or cephalexin 500 mg 4 times a day added if secondary infection is suspected. The term orbital cellulitis means that the infection has spread to or originated in the tissues posterior to the orbital septum. This may be manifest as diplopia or restriction in ocular motility as the extraocular muscles are affected, proptosis as edema in the orbit pushes the globe forward, decreased vision as the optic nerve is affected, or pupillary change if innervation of the pupil is affected. Fever is suggestive of orbital cellulitis in the differential diagnosis of periocular inflammation. This condition is more commonly associated with sinusitis than with periocular trauma as an antecedent disorder.76 Most series report a 50% to 75% incidence of sinusitis or other upper respiratory infection in association with orbital cellulitis.137 The bacteria that most commonly cause orbital cellulitis are S. aureus, Streptococcus pyogenes, and Streptococcus pneumoniae.91 Anaerobes are frequently present in cases of chronic sinusitis and should be suspected in orbital cellulitis associated with long-standing sinus disease.91 If not treated aggressively, orbital cellulitis may be associated with life-threatening infection of the central nervous system. Before antibiotics became available, approximately 19% of persons with orbital cellulitis died of intracranial complications and 20% of survivors became blind in the involved eye.91 This disorder requires hospitalization and intravenous antibiotic therapy. Interim therapy should include moxifloxacin 400 mg once a day. Alternative antibiotic choices are levofloxacin 500 mg twice a day, ciprofloxacin 750 mg twice a day, or amoxicillin/clavulanate 875 mg/125 mg every 8 hours. A decongestant should be added if sinusitis is present, and emergent evacuation should be undertaken. Orbital pseudotumor is an inflammatory disease of the orbit that may present very much like orbital cellulitis. The differentiation between these two entities may be difficult.76 There would typically not be a history of preceding sinusitis. A reasonable approach in the wilderness is to begin therapy with moxifloxacin 400 mg once a day and arrange for emergent evacuation. Prednisone (80 mg/day) should be added if there is no response to antibiotic therapy, there is no fever or sign of central nervous system involvement, and evacuation has not been possible by 24 to 48 hours after presentation. If prednisone therapy is initiated, its efficacy should be evaluated after 48 hours. If there has been a decrease in pain, erythema, edema, or propto-

sis, therapy should be continued until evacuation is accomplished. If there has been no response after 48 hours, the prednisone may be discontinued without tapering.


PERIOCULAR TRAUMA Eyelid Laceration The most important aspect of managing an eyelid laceration is carefully to exclude the presence of penetrating injury to the globe. Clues to the presence of an open globe are noted in the sections on Obvious Open Globe and Occult Ruptured Globe, later. A lid laceration that is horizontally oriented on the eyelid, does not penetrate the full thickness of the lid, and does not involve the lid margin is relatively easily managed. In the absence of an ability properly to irrigate, disinfect, and suture the laceration, it should be managed by irrigation with the cleanest disinfected water available, application of topical antibiotic drops (ciprofloxacin, ofloxacin, or tobramycin) to the laceration, drying the surrounding skin surface, and then closing the laceration with tape strips. The wound may then be treated with antibiotic ointment (bacitracin or erythromycin) four times a day for 3 to 4 days. Alternatively, the laceration may be left open, treated with antibiotic ointment four times a day, and repaired 1 or 2 days later.76 The laceration should be observed frequently while healing. If redness or discharge develops, the victim should be started on moxifloxacin 400 mg once a day, levofloxacin 500 mg once daily, or dicloxacillin 500 mg every 6 hours, the wound closure tape should be removed from the laceration, and evacuation should be expedited, especially if the response to oral antibiotics is poor. Complicated lid lacerations, defined as stellate or complex, or involving the lid margin or the canthi (medial or lateral end of the palpebral fissure), are more difficult to manage. These lacerations may result in secondary functional difficulties if ocular lubrication or lacrimal drainage becomes impaired. In addition, cosmesis may be poor if a meticulous repair is not done. These wounds should be managed by irrigation with the cleanest disinfected water available, application of antibiotic ointment, and coverage with a sterile dressing. Evacuation for definitive repair should be expedited.

Corneal Frostbite Corneal frostbite is an uncommon disease, but has been reported during such activities as snowmobiling without protective eye goggles when participants maintain their eyes open in conditions of high windchill factor.5 Symptoms and treatment are the same as those described in the section on Corneal Abrasion, later.

Instillation of Adhesive Drops into the Eye Inadvertent instillation of a “superglue” (cyanoacrylate-type adhesive) compound into the eye may bind the lids tightly together. Overnight application of a pressure patch with eye pads presoaked with water has been reported to make manual separation of the lids possible and eliminate the need for general anesthetic and surgical separation of the lids.102 Ophthalmic ointment inserted through any small opening in the adherent lids has also been reported to facilitate resolution.86 Once the lids are separated, the eye should be checked for a corneal abrasion.116

Chapter 25: The Eye in the Wilderness


CHEMICAL INJURY TO THE EYE The mainstay in the management of any chemical eye injury is immediate and copious irrigation of the ocular surface with water from whatever source is most readily available. In the wilderness, bottled water or intravenous solution is the best option. If neither of those is available, treated (filtered and disinfected) water from a drinking container is the next best option, with untreated water a last resort. Instillation of several drops of tetracaine will make the procedure much less uncomfortable for the victim. Irrigation should be continued for a minimum of 30 minutes.76 The two most damaging chemicals are strong acids and alkalis.76 Sulfuric acid from an exploding car battery is a typical acid, whereas cleaning products, such as drain cleaners, are typical alkalis. Caustic alkalis are more likely to damage the eye than are acids because of their profound and rapid ocular penetration. Do not attempt to neutralize the corneal surface with acidic or alkaline solutions. Chemicals other than acids and alkalis may be uncomfortable when they are encountered, but are less likely to produce significant longterm damage. After a minimum of 30 minutes of flushing has been completed, the eye should be examined for retained particles. These should be removed with a moistened cotton-tipped applicator.76 Treatment for an acid- or alkali-induced injury includes moxifloxacin 0.5% drops (1 drop four times a day) until fluorescein staining confirms that the corneal epithelial defect that typically accompanies these injuries has resolved. Topical prednisolone 1% should be added if there is significant inflammation. Prednisolone drops should be used every hour while awake for 3 days. Eye pain is managed with scopolamine drops four times a day for 3 days and oral pain medications.114 Evacuation should be expedited if (1) the cornea is found to be opaque, (2) a large epithelial defect is found on fluorescein staining, or (3) significant pain persists after 3 days. Another sign of serious injury is blanching of the conjunctiva in the limbal area.76 A special type of chemical injury to the eye is ocular envenomation from a spitting cobra.45,49,132 Ocular injury from cobra venom may be severe and result in blindness. Cobras can project this venom out to a range of 3 m (10 feet) and typically aim directly for the victim’s eyes. Ocular surface envenomation causes severe conjunctival and corneal inflammation, edema, and erosions. Corneal erosions may progress to corneal ulceration, perforation, hypopyon, and endophthalmitis. Central corneal opacification may result despite aggressive therapy. One report described nine individuals who had suffered ocular surface cobra envenomations.132 Five had only severe conjunctivitis, whereas corneal erosions developed in the other four. Two individuals were permanently blinded as a result. Therapy includes immediate flushing of the eyes as described previously. After this is done, check for a corneal abrasion and treat with moxifloxacin 0.5% drops if an erosion is present (1 drop four times a day until the erosion is healed). Note that healing may be prolonged in toxin-induced corneal surface injuries. Immediate consultation with a toxicology consult service and a corneal/external disease subspecialist should be obtained if possible and an expedited evacuation arranged. Topical steroid therapy should be considered (1 drop of prednisolone every hour while awake) and discussed with the consultant. The decision to treat is based on the severity of symptoms and the pres-

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ence or absence of a corneal erosion or ulcer. The value of topical application of specific cobra antivenom has not been documented, so this therapy is not recommended. Systemic heparin therapy has been shown to be useful in preventing corneal opacification in animal models of this injury.57,58 Another type of chemical injury to the eye may occur when the eyes are sprayed with skunk musk. A PubMed search did not disclose any reports of human eye injuries from this type of event, but such an episode should be managed with immediate ocular irrigation as described previously. If discomfort persists beyond several hours, check for a corneal abrasion and treat with moxifloxacin 0.5% drops (1 drop four times a day until the abrasion is healed). If fluorescein staining does not show an abrasion but significant discomfort persists, a 3-day course of prednisolone 1% drops (1 drop four times a day for 3 days or until symptoms have resolved) may be of benefit. If pain is severe and unrelieved by prednisolone drops or persists after the 3-day course has been completed, consider an expedited evacuation and an ophthalmology consultation.


ACUTE LOSS OF VISION IN A WHITE, QUIET EYE

Vision may be variably decreased with many of the disease entities that are noted later in the section on Acute Red Eye. This section addresses sudden loss of vision that occurs in a white, quiet eye. A differential diagnosis is provided in Box 25-3. Disorders that cause this symptom are often difficult to diagnose without ophthalmic instruments (none of which is included in the kit shown in Box 25-1). There are few treatments for most of these disorders that are likely to be effective in a wilderness setting. Although an afferent pupillary defect (Marcus Gunn pupil) may be present, this is a nonspecific finding that would be expected with most of the disorders in Box 25-3, except for vitreous hemorrhage and high-altitude retinal hemorrhage. An important question that must be asked in the face of acute loss of vision in a white, quiet eye is “Does this person have giant cell arteritis?” Giant cell arteritis (GCA), also called temporal arteritis, can cause devastating anterior ischemic optic neuropathy, often first noted on waking and that usually becomes permanent.43 Subsequent involvement of the second eye is common if GCA in the first-stricken eye is not promptly treated.43 Although visual loss has been reported to occur in both eyes simultaneously, there is typically a delay of 1 to 14 days before the second eye is affected.1 Loss of vision in the

Box 25-3. Differential Diagnosis of Acute Loss of Vision in a White, Quiet Eye Retinal detachment Central retinal artery occlusion Anterior ischemic optic neuropathy Optic neuritis Central retinal vein occlusion Arteritic anterior ischemic optic neuropathy Vitreous hemorrhage High-altitude retinal hemorrhage

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second eye can be prevented in most cases by prompt initiation of high-dose corticosteroid therapy.1,43,52,97 Arteritic anterior ischemic optic neuropathy is typically a disease of older individuals, with one large study reporting a mean age of 70 years and the age of the youngest patient as 53 years.1 Clues to diagnosis are temporal headache, jaw claudication, fever, weight loss, transient visual obscurations, and polymyalgia rheumatica (generalized myalgias).97 The visual obscurations seen in GCA usually last 2 to 3 minutes.97 If a person is thought to be suffering from GCA, he or she should be started on prednisone 80 mg once a day and evacuation expedited. If one suspects a retinal detachment based on a history of high myopia (extreme nearsightedness), floaters, or photopsias (flashing lights), expedited evacuation should be undertaken because of the need for surgical repair. Loss of central vision caused by a retinal detachment usually means that the macula is involved and that surgical repair is urgent rather than emergent. Ross and Kozy109 found that a delay to surgery of up to 1 week in macula-off rhegmatogenous retinal detachments did not affect final visual acuity. Expedited evacuation to a facility that has retinal surgery capability allows for more precise determination of the urgency for surgical repair. If the victim is at altitude (above approximately 3048 m [10,000 feet]), high-altitude retinal hemorrhage (discussed later) should be suspected and further ascent avoided.17 Descent of at least 915 m (3000 feet) should be undertaken as soon as feasible.17 Another potentially treatable cause of sudden loss of vision in a white, quiet eye is central retinal artery occlusion (CRAO). Previous conventional therapy for CRAO of ocular massage, pentoxifylline, and anterior chamber paracentesis has been reported to be unsuccessful in restoring vision in 40 of 41 patients with CRAO, even though 11 patients presented within 6 hours of visual loss and 17 presented within 12 hours.110 Primate retinas can tolerate no more than 100 minutes of ischemia caused by a complete blockage of retinal blood flow.51 However, fluorescein angiography has shown that in humans, CRAO is seldom complete, and that therapy begun up to 6 hours after visual loss may be successful in restoring vision.110 Hyperbaric oxygen was reported successful in restoring vision on two separate occasions in one patient with recurrent branch retinal artery occlusions associated with Susac’s syndrome.74 Oxygen is supplied to the retina from both the retinal and choroidal circulations. Under normoxic conditions, approximately 60% of the retina’s oxygen is supplied by the choroidal circulation. Under hyperoxic conditions, the choroid is capable of supplying 100% of the oxygen needed by the retina.74 When retinal arterial flow is interrupted, the retinal tissue undergoes a period of ischemia. Blood flow may be spontaneously reestablished, as frequently happens with arterial obstruction, or ischemia may continue until cell death and necrosis occur.80 The period of time during which the tissue is ischemic, yet capable of recovery, is called the ischemic penumbra.80 Hyperbaric oxygen is not always required for a reversal of retinal ischemia. The author has treated a monocular patient who suffered a central retinal artery occlusion in his only seeing eye and presented to the emergency department within an hour of visual loss. The victim’s vision improved from 20/400 to 20/25 within minutes on supplemental oxygen by mask. Unfortunately, however, his vision decreased rapidly to 20/400 whenever the supplemental oxygen was removed. The victim was heparinized

Box 25-4. Differential Diagnosis of the Acute Red Eye Obvious open globe Corneal abrasion Corneal ulcer Subconjunctival hemorrhage Traumatic iritis Hyphema Occult open globe Herpes simplex virus keratitis Corneal erosion Acute angle-closure glaucoma Iritis Scleritis Conjunctivitis Blepharitis Ultraviolet keratitis Episcleritis Conjunctival foreign body Dry eye Contact lens overwear syndrome

and maintained on supplemental oxygen for approximately 10 hours, at which time the removal of oxygen no longer caused a decrease in vision. If oxygen is being carried for an extreme altitude summit attempt or for other purposes, a person with sudden painless loss of vision should be given a trial of oxygen administered in as high a concentration as possible to see if this therapy results in visual improvement. Care should be taken when monocular visual loss occurs. Although central vision may still be normal in the fellow eye, depth perception may be impaired and the victim may therefore be at increased risk of a fall during evacuation.


ACUTE RED EYE Box 25-4 provides a partial list of disorders that can result in an acute red eye. In the absence of a slit lamp, the diagnosis must rely on the basic techniques of history, penlight inspection, fluorescein staining, response to administration of topical anesthesia, and pupillary status. The discussion of the differential diagnosis of the acute red eye that follows uses these clinical findings to establish the diagnosis. An algorithmic representation is shown in Figure 25-1. The term fluorescein positive is used to denote an eye with a discrete area of staining noted with cobalt blue light after instillation of fluorescein dye. Some conditions, such as blepharitis, viral keratoconjunctivitis, and ultraviolet (UV) keratitis, may cause a pattern of punctate staining referred to as superficial punctate keratitis (SPK).

Traumatic Ocular Disorders Obvious Open Globe If there is a history of trauma and penlight inspection of the eye reveals an obvious open globe (such as the eye in Fig. 25-2), the examination should be discontinued and a protective shield placed over the eye. Do not apply a pressure patch or instill any topical medication. There are two primary concerns in the management of this condition. The first is to minimize manipula-

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History of trauma Yes

No

Fluorescein test

Obvious open globe

Negative or punctate staining only

Positive No

Positive

• Corneal abrasion • Corneal ulcer

Response to topical anesthesia

• Corneal ulcer • Corneal erosion • HSV keratitis

Fluorescein test Negative or variable

Pain relieved (or no pain)

No relief

Pupillary status

• Subconjunctival hemorrhage • Traumatic iritis • Hyphema • Ruptured globe

Dilated

• Angle-closure glaucoma

Normal or miotic

• Iritis • Scleritis

• Conjunctivitis • Blepharitis • UV keratitis • Conjunctival foreign body • Dry eye • Subconjunctival hemorrhage • Episcleritis • Contact lens overwear syndrome

Figure 25-1. Algorithm showing wilderness diagnostic procedure for the acute red eye.

Figure 25-2. Obvious open globe (corneoscleral laceration). (Courtesy Steve Chalfin, MD, University of Texas Health Science Center, San Antonio,TX.)

tion or additional trauma to the eye that might raise intraocular pressure and result in expulsion of intraocular contents through the corneal or scleral defect. The second is to prevent development of post-traumatic endophthalmitis, an infection of the aqueous and vitreous humors of the eye. This typically has devastating visual results, with only 30% of victims in one study retaining visual acuity greater than or equal to 20/400.69 Staphylococcus epidermidis is the most common pathogen implicated, but Bacillus cereus is a very aggressive pathogen often isolated in this condition.69 After the shield is placed, the victim should be started on moxifloxacin 400 mg once a day or levofloxacin 500 mg once a day. Trovafloxacin 200 mg once a day is another alternative choice for prophylaxis because of its very broad antibacterial spectrum54,130 and good ocular penetration.89 Ciprofloxacin 750 mg twice a day is a fourth option. A person with an obvious open globe needs surgical repair as soon as possible and should be evacuated emergently. Because there is a possibility that air may have been introduced into the eye, barometric pressure changes during evacuation should be

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Figure 25-3. Occult open globe with uveal pigment at the limbus and a peaked pupil. (Courtesy Steve Chalfin, MD, University of Texas Health Science Center, San Antonio,TX.)

Figure 25-4. Corneal abrasion. (Courtesy Steve Chalfin, MD, University of Texas Health Science Center, San Antonio,TX.)

minimized, if possible. However, this consideration is secondary to the need for expeditious transport to a facility where surgical repair can be performed.

Occult Ruptured Globe A penetrating injury to the eye or a ruptured globe may not always be obvious. Clues to occult rupture include large subconjunctival hemorrhage with chemosis, dark uveal tissue present at the limbus, distorted pupil (Fig. 25-3), fluorescein leak from a linear or punctate corneal epithelial defect, mechanism of injury (e.g., hammering metal on metal, impaling injury), or decrease in vision. If an occult globe rupture is suspected, the victim should be treated as described previously for an obvious open globe. The relatively less severe appearance of the injury does not eliminate the threat of endophthalmitis, so systemic antibiotic therapy as noted previously should be initiated.

Corneal Abrasion A corneal abrasion is disruption of the protective epithelial covering of the cornea (Fig. 25-4). This results in intense pain, tearing, light sensitivity (photophobia), and increased susceptibility to infection until the defect has healed (usually in 2 to 3

days). There is typically a history of antecedent trauma or contact lens wear. The sine qua non for this diagnosis is an epithelial defect on fluorescein staining. Standard treatment in the recent past consisted of antibiotic ointment followed by application of a pressure patch. A recent study, however, has shown that small (80% PEF variability: 20%–30%

Low-dose inhaled corticosteroid OR Leukotriene modifier, cromolyn, nedocromil, or sustained-release theophylline

Step 1: Mild Intermittent Symptoms ≤2 times a week, normal PEF between exacerbations Nights with symptoms: ≤2/mo PEF or FEV1: >80% PEF variability: 40 years), cigarette smoking, and diabetes mellitus. Hyperlipidemia, hypertension, and hyperhomocystinemia are also important risk factors.58 When evaluating a patient with peripheral arterial disease for a wilderness activity it is helpful to characterize the severity of the disease and how it affects functional capacity. The most useful method for evaluating severity is the ankle-to-arm ratio of systolic blood pressure (ankle–brachial index), which is easily obtained with a standard blood pressure cuff and a Doppler device.58 Systolic blood pressure is measured by Doppler ultrasonography in each arm and in the dorsalis pedis and posterior tibial arteries in each ankle. The higher of the two arm pressures is selected, as is the higher of the two pressures in each ankle to calculate a left and right ankle–brachial index. An ankle-to-arm pressure ratio of 0.91 to 1.3 is normal. A ratio of 0.41 to 0.9 indicates mild to moderate peripheral arterial disease, and less than 0.4 is severe. A ratio of greater than 1.3 indicates a calcified noncompressible vessel. Patients with claudication, defined as walking-induced pain in one or both legs (primarily in the calves) that does not go away with continued walking and is relieved by rest, typically have ankle–brachial indexes in the mild to moderate range. Patients with critical ischemia have ankle–brachial indexes in the severe range. Increased exercise is associated with wilderness activities and this may be a limiting factor for patients with peripheral vascular disease who have claudication. Hiking or trekking, however, are reasonable activities for patients with claudication if they engage in a regular exercise training program. The benefit of exercise in improving functional capacity in patients with claudication is well proven.121 One meta-analysis concluded that exercise training improved pain-free walking time in patients with claudication by an average of 180% and improved maximal walking time by an average of 120%.48 Exerciseinduced increases in functional capacity and lessening of claudication symptoms are primarily due to improvements in endothelial vasodilator function, skeletal muscle metabolism, blood viscosity, and biomechanics of walking. Increases in leg blood flow and oxygen delivery may also occur, but do not appear to account for the large improvements in exercise capacity that are observed. A supervised exercise program several times a week is recommended. The key elements of each session include a warm-up period followed by walking on a track or treadmill at a workload that causes claudication in about 5 minutes. Then, continue at that workload until claudication of moderate severity occurs, then rest standing or sitting for a brief period to allow symptoms to subside, and repeat the exercise–rest pattern for the duration of the session, lasting initially approximately 30 minutes but working up to about an hour. This exercise strategy might also be used while hiking, repeating periods of exercise and rest as gauged by claudication symptoms, and could potentially lead to improvements in exercise capacity over time. A walking or hiking exercise program needs to be done regularly and sustained over months or the benefits diminish.

Patients with peripheral arterial disease who wish to pursue wilderness activities or an exercise program should undergo evaluation for heart disease, hypertension, hyperlipidemia, and diabetes. Appropriate treatment and risk factor modification should be initiated (including smoking cessation). In addition, an exercise test with 12-lead electrocardiographic monitoring should be performed to evaluate for cardiac ischemia. Patients with claudication may be limited by leg pain during a maximal exercise test, thus limiting the stress on the heart, but the information gained regarding heart rate and blood pressure response, work level at which claudication occurs, and exercise capacity is useful for estimating the type of wilderness activity that may be pursued and in formulating a prescription for exercise training. Treatment of claudication should include a formal walkingbased exercise program. In addition, several options exist for drug therapy. The Seventh ACCP Consensus Conference on Antithrombotic and Thrombolytic Therapy recommends lifelong aspirin therapy in patients with peripheral arterial disease.24 Clopidogrel is a thienopyridine drug that inhibits platelet activation and is an alternative to aspirin, and has fewer hematologic side effects than the related drug ticlopidine. Clopidogrel has U.S. Food and Drug Administration (FDA) approval for prevention of ischemic events in patients with peripheral arterial disease, but aspirin is usually recommended over clopidogrel.24,58 Cilostazol and pentoxifylline are the two drugs approved in the United States for treating claudication. Cilostazol is a phosphodiesterase inhibitor that suppresses platelet aggregation and is a direct arterial vasodilator. Cilostazol improves both pain-free and maximal treadmill walking distance in patients with stable moderate to severe claudication,126 and is recommended for patients with more severe disabling claudication.24 Because other oral phosphodiesterase inhibitors used for inotropic therapy have caused increased mortality in patients with advanced heart failure, cilostazol is contraindicated in heart failure of any severity. Pentoxifylline is a methylxanthine derivative that improves deformability of red cells, lowers plasma fibrinogen concentrations, and has antiplatelet effects. It is not as effective in improving walking ability as cilostazol.29 The Seventh ACCP Consensus Conference did not recommend pentoxifylline for treatment of peripheral arterial disease.24 Patients with symptomatic peripheral arterial disease can pursue activities in the wilderness that are appropriate for their functional capacity. Such activities should include walking or hiking and allow for periods of rest when necessary. An exercise program along with drug therapy can improve ability to participate in wilderness activities. Environmental extremes such as cold and high altitude may worsen limb ischemia and predispose to frostbite.

Raynaud’s Phenomenon Raynaud’s phenomenon is an exaggerated vasoconstrictor response to cold or emotional stress in digital arteries, precapillary arterioles, and cutaneous arteriovenous shunts of the fingers or toes. It presents clinically as pallor, cyanosis, and often rubor of the skin134 (Fig. 29-1). It occurs more commonly in the hands than in the feet. Pallor shows the vasospasm and loss of arterial blood flow, cyanosis shows the deoxygenation of static venous blood, and rubor shows reactive hyperemia after return of blood flow. This classic three-phase color change occurs in approximately two thirds of affected patients; the remainder

Chapter 29: Chronic Diseases and Wilderness Activities

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Figure 29-1. Active Raynaud’s phenomenon. A, Sharply demarcated pallor resulting from the closure of digital arteries. B, Digital cyanosis of the fingertips in a patient with primary Raynaud’s phenomenon.(From Wigley FM: N Engl J Med 347:1001–1008, 2002. Copyright © 2002 Massachusetts Medical Society. All rights reserved.)

A 12

have only pallor and cyanosis. Numbness, tingling, and burning frequently accompany these changes, particularly after reperfusion of the vascular beds with rewarming. The ischemic phase of the attack is evidenced by demarcated pale or cyanotic skin limited to the digits. It typically starts in one or several digits after exposure to cold and then spreads symmetrically to all fingers of both hands. In most cases the attack is self-limited and resolves after rewarming the hands or feet. In most patients, Raynaud’s phenomenon is a primary syndrome and represents an exaggerated physiologic response to cold. Raynaud’s phenomenon can also be secondary to collagen vascular disease such as systemic sclerosis or systemic lupus erythematosus. In severe secondary Raynaud’s phenomenon, superficial ulceration or deep tissue necrosis with gangrene and amputation can occur. Primary Raynaud’s phenomenon is more common in women than men, and occurs in approximately 5% of the U.S. population.134 Vasoconstriction is triggered by cold temperatures of the ambient environment when the patient’s body becomes cold, or by exposing the hands alone to cold, such as when handling cold objects. Raynaud’s phenomenon can be exacerbated by the combination of cold and high altitude compared with cold exposure alone, which may be due to the higher sympathetic tone at high altitude. There are several risks accompanying attacks of Raynaud’s phenomenon in a wilderness environment. The intense vasoconstriction predisposes to cold injury, including frostbite and trench foot. The intense vasoconstriction can also make the hands nonfunctional for performing basic tasks essential for survival in a cold-weather environment, such as zipping up a coat or putting on crampons. A person with Raynaud’s phenomenon must rely on the help of others when his or her hands become cold and incapacitated. This includes help with performing simple tasks such as adding layers of clothing, zippering outer garments, lacing boots, or rewarming hands. Measures can be taken to minimize the risk of serious attacks of Raynaud’s phenomenon. The location of a wilderness trip could be in a warmer climate, or could take place in the summer rather than winter. If winter activities are pursued, a location with a less severe winter environment can be chosen. For example, high-altitude mountaineering in South America is

B more equatorial and takes place in a warmer climate than mountaineering in North America, Asia, or Europe. Appropriate cold-weather gear and clothing are essential to keep the entire body warm and help mitigate attacks. High-quality plastic mountaineering boots or ski boots and expedition-type mittens or gloves with space for disposable chemical hand warmers help in winter environments while climbing or skiing. Adequate hydration and nutrition also help prevent attacks. Good physical condition before the climb reduces the chance of exhaustion, which would exacerbate Raynaud’s phenomenon. It is especially important for a climber with Raynaud’s phenomenon to use conservative judgment and retreat early, before becoming overextended and exhausted. Nicotine and other drugs with peripheral vasoconstrictive effects, such as over-thecounter decongestants, should be avoided. Treatment of Raynaud’s phenomenon is initially focused on behavioral modification. It is clear that a significant behavioral component contributes to attacks because in placebo-controlled trials of Raynaud’s phenomenon, the placebo group usually significantly improves along with the active drug group. This implies that increased awareness of Raynaud’s phenomenon and improving clothing insulation can reduce the frequency of attacks. Temperature-related biofeedback is used in combination with various relaxation techniques to treat Raynaud’s phenomenon, with inconsistent results.106 Behavioral modification, supplemented by pharmacologic therapy if necessary, is the mainstay of therapy for primary Raynaud’s phenomenon. Secondary Raynaud’s phenomenon often requires primary pharmacologic treatment. Calcium channel blockers, specifically nifedipine, are the most widely used drugs for treatment of Raynaud’s phenomenon. In one blinded, randomized clinical trial, sustained-release nifedipine treatment reduced attacks by 66% compared with placebo.106 Only 15% of subjects discontinued therapy because of adverse effects of nifedipine. Extended-release nifedipine is favored because of the possible hypoperfusion of digits with short-acting nifedipine owing to a decrease in systolic blood pressure. Other oral drugs that have been used to treat Raynaud’s phenomenon include the peripherally acting α1adrenergic blocker prazosin, although its efficacy may be transient; the angiotensin II receptor antagonist losartan; the

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selective serotonin reuptake inhibitor fluoxetine;134 and the vasodilator isoxsuprine.132 Ginkgo biloba was effective in treating primary Raynaud’s phenomenon in one study,92 and topical therapy with nicotinates (hexyl nicotinate) is used to treat mild to moderate Raynaud’s phenomenon.12

Osteoarthritis Osteoarthritis is a major cause of disability in adults and most commonly affects the joints of the hands, hips, knees, and cervical and lumbar spine. Uncommonly affected joints include the shoulder, elbow, and wrist. Factors in the evolution of osteoarthritis include initiation in either previously injured or susceptible joints; development, which is biochemically mediated and biomechanically driven; and clinical expression, which may be modified by factors such as weight and sex.27 The primary symptom of osteoarthritis is pain that is typically exacerbated by activity and relieved by rest. With more advanced disease, pain may occur with progressively less activity. Osteoarthritis can be inflammatory or noninflammatory. Patients with noninflammatory osteoarthritis complain primarily of joint pain and disability. Physical findings in affected joints include tenderness, bony prominence, and crepitus. Patients with inflammatory osteoarthritis complain of articular swelling, morning stiffness, and night pain. Signs of inflammation include joint effusion on examination or radiography, warmth on palpation of the joint, and synovitis on arthroscopic examination. The degree of disability caused by hip or knee osteoarthritis is an important consideration for wilderness activities. Patients should be guided toward activities that are within their functional capability. Wilderness activities that cause increased weight bearing on lower extremity joints should be avoided. For example, hiking or trekking with a light pack or bicycling are recommended over activities such as a multiday backpacking trip or mountaineering where carrying heavy loads might be required. Risk of development of hip or knee osteoarthritis is also relevant to wilderness activities. There is increased risk of lower limb osteoarthritis associated with repetitive, high-impact sports and that risk is increased with joint injury.27 When assessing risk for osteoarthritis from wilderness activities, the nature and intensity of the activity, presence of previous injury, and body mass index should all be taken into account. Recreational running does not appear to increase the risk of knee osteoarthritis,27,72 but how this applies to trail running is not known. The evidence that obesity is strongly associated with development of knee, and probably hip, osteoarthritis and that weight loss improves joint pain and function94 are relevant to wilderness activities where carrying heavy loads is required. Wilderness activities that repeatedly require carrying a heavy pack, or squatting and kneeling maneuvers, may cause progression of knee or hip osteoarthritis, especially if there has been previous injury to a joint or associated joint muscles, ligaments, or tendons.118 Very little information is available on development of hand arthritis with wilderness activities such as climbing. One study suggests that rock climbing at a high standard for over 10 years may increase risk of osteoarthritis in certain joints of the hands.110 Measures that can be taken to improve functional capacity for wilderness activities include nonpharmacologic and pharmacologic treatments. The goal of management of osteoarthritis is to control pain and improve function and health-related

quality of life with avoidance of therapeutic toxicity. Potential treatments include exercise, biomechanical techniques, pharmacologic therapy, and surgery. Exercise is the primary nonpharmacologic intervention for lower limb osteoarthritis that is directly related to wilderness activities. There is good evidence that strengthening and aerobic exercise can reduce pain and improve function and health status in patients with knee osteoarthritis; the evidence for hip osteoarthritis is not as compelling, but exercise is still recommended.41,109 Well-conditioned muscle and muscular balance are needed to attenuate impact loads and provide joint stability. Muscular conditioning may prevent exercise-related osteoarthritis.118 Muscular conditioning is achieved through well-designed exercise programs performed with supervision or as home exercise routines that include range-of-motion and flexibility exercise, muscle conditioning, and aerobic cardiovascular exercise.43,130 Biomechanical treatments for knee osteoarthritis are relevant to wilderness activities such as hiking and trekking and are helpful at reducing symptoms. For appropriate application, consultation with a physiatrist or sports medicine physician may be required. Shock-absorbing footwear reduces impact loading, heel wedges reduce loading of the medial knee joint surface, neoprene support sleeves increase proprioception and reduce feelings of instability, dynamic bracing controls lateral instability, and taping allows repositioning of the patella.43 Hiking poles are an additional method to help unload lower extremity joints while hiking or trekking, and may be helpful for patients with osteoarthritis of the hip and knee, especially during downhill walking.66,113 The major pharmacologic treatments for osteoarthritis include analgesics, nonsteroidal anti-inflammatory drugs (NSAIDs), and intra-articular corticosteroids. The major goal of treatment with these agents is relief of pain, which usually is achieved with nonopioid analgesics. The nonprescription analgesic acetaminophen at doses up to 4 g/day is the recommended primary treatment.13,135 Patients with osteoarthritis who have mild to moderate pain will obtain a similar degree of pain relief with acetaminophen as with NSAIDs.43 Although it is one of the safest analgesics, acetaminophen can prolong the half-life of warfarin and can cause hepatic toxicity at therapeutic doses in patients with chronic alcohol abuse. For patients who do not obtain adequate symptom relief with nonopioid analgesics, self-limited use of nonselective NSAIDs is an alternative after considering the risk of upper gastrointestinal and renal toxicity. Cyclooxygenase-2–selective NSAIDs are an alternative with less potential risk of gastrointestinal toxicity, but with an increased risk of serious cardiovascular events. The risk of adverse cardiovascular events may also apply to the nonselective NSAIDs, and they are recommended only for short-term use in the relief of pain11 (updated information is available at the FDA website, www.fda.gov/cder/index.html). An alternative to NSAIDs for osteoarthritis pain not relieved by acetaminophen is the centrally acting oral analgesic tramadol. It is a synthetic opioid agonist that inhibits reuptake of norepinephrine and serotonin and has been approved by the FDA for treatment of moderate to severe pain. The efficacy of tramadol has been found to be comparable with that of ibuprofen in patients with hip and knee osteoarthritis.43 Another alternative therapy for osteoarthritis is glucosamine and chondroitin. These are compounds extracted from animal products that are absorbed by the gastrointestinal tract and

Chapter 29: Chronic Diseases and Wilderness Activities appear to be capable of increasing proteoglycan synthesis in articular cartilage. One meta-analysis concluded that, despite methodologic flaws in many studies, these compounds are probably efficacious for treatment of osteoarthritis and have no significant side effects.87 Relevant to wilderness activities, glucosamine and chondroitin were effective in relieving symptoms of knee osteoarthritis in active members of the U.S. Navy diving and special warfare community.77 In persons with osteoarthritis of the hand or knee who have mild to moderate pain, use of topical analgesics, such as capsaicin cream, is appropriate as adjunctive treatment or monotherapy. Evidence supports short-term (up to 2 weeks) improvement in symptoms of osteoarthritis of the knee after intra-articular corticosteroid injection. Significant improvement may also occur for up to 16 to 24 weeks with a dose equivalent to 50 mg of prednisone.4 There is concern that multiple injections of intra-articular corticosteroids may promote disease progression; further study is required. Corticosteroid injection for knee osteoarthritis to provide benefit for the duration of a wilderness trip for up to 2 weeks seems reasonable,81 and may provide enough pain relief and increase in function to make wilderness activity safer and more enjoyable. Surgical treatment of osteoarthritis is usually considered after failure of nonsurgical treatments. Four categories of surgical treatment are available: osteotomy, arthroscopy, arthrodesis, and arthroplasty. Osteotomies are performed in persons with early osteoarthritis and may relieve symptoms and slow the rate of progression. Arthroscopic debridement and lavage can also successfully alleviate symptoms, particularly in the case of degenerative meniscal tears in the presence of mechanical symptoms. When there is substantial joint space narrowing, however, arthroscopic surgery has limited benefit. Arthrodesis, or joint fusion, successfully alleviates pain and is commonly performed in the spine and in small joints of the carpus, hand, and foot. Arthrodesis of the major proximal joints of the upper and lower extremities is not well tolerated because of the functional deficits associated with loss of motion. Total joint arthroplasty represents the most significant advancement in the treatment of osteoarthritis in the past century. It is the mainstay of surgical treatment for advanced osteoarthritis of the hip, knee, and glenohumeral joints. For older persons, total joint replacement is a highly successful procedure that will probably last for the duration of their lives. The pain and disability of end-stage osteoarthritis can be eliminated, restoring patients to near-normal function. However, a total joint replacement may not be sufficiently durable in persons with life expectancies exceeding 20 years and those who wish to participate in high-demand activities. After total joint arthroplasty, patients should be encouraged to remain physically active for general health and also for the quality of their bone. There is evidence that increased bone quality improves prosthesis fixation and decreases the incidence of early loosening. To recommend a certain activity after total knee or hip replacement, factors such as wear, joint load, intensity, and the type of prosthesis must be taken into account for each patient and sport. Because load will influence the amount of wear exponentially, only activities with low joint loads such as swimming, cycling, or walking should be performed regularly for exercise. If an activity is performed intermittently for recreation, then activities with higher joint loads such as skiing or hiking may be acceptable. It is unwise to start technically

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demanding wilderness activities after total joint replacement because the joint loads and the risk for injuries are generally higher for these activities in unskilled individuals. Activity recommendations differ after total knee and total hip replacement. During activities such as hiking or jogging, high joint loads occur between 40 and 60 degrees of knee flexion, where many knee designs are not conforming and high stress will occur. It is prudent to be more conservative after total knee arthroplasty than after total hip arthroplasty for activities that exhibit high joint loads in knee flexion. After total knee replacement, patients should alternate activities such as walking and cycling. For mountain hiking, patients are advised to avoid descents or at least use hiking poles. Jogging or sports involving running should be discouraged after total knee replacement.69,70

Hematology Anemia The most common hematologic condition encountered is anemia. Although specific anemias have certain concerns discussed in the following sections, the general effect of mild to moderate anemia is a reduction in exercise capacity. In general, for every . 1% fall in hematocrit, maximum oxygen consumption (Vo2max) decreases 1% and endurance decreases by 2%.18,37,50,129 Thus, anemic patients should be counseled that their ability to perform strenuous exercise will be reduced compared with traveling companions; they may not be able to keep the same pace or hike as far.

Thalassemia Trait. Thalassemia trait is the most common inherited hemoglobin disorder and can be encountered in patients from diverse ethnic origins. β-Thalassemia trait is autosomal dominant and results in a mild microcytic anemia (mean corpuscular volume [MCV] approximately 60 to 70 femtoliters [fL]) and hematocrit in the 30% range. It is diagnosed by hemoglobin electrophoresis showing elevated hemoglobin A2 in the presence of normal iron stores. The genetics of α-thalassemia trait are more complex, with the most common forms being autosomal dominant; the condition is electrophoretically silent. α-Thalassemia trait leads to microcytosis (MCV approximately 70 fL) with hematocrit at the lower end of the normal range. A severe recessive variant, hemoglobin H disease, predominantly affects people of southeast Asian origin. This type of αthalassemia results in a hemolytic anemia with a hematocrit of 25% to 35%. Presence of either α- or β-thalassemia trait does not lead to any specific problems except for anemia. Diagnosis is important to avoid inappropriate therapy with iron and provide genetic counseling for families. Iron Deficiency. Iron deficiency is very common, affecting up to 40% of women and 1% to 5% of men. In athletes, especially runners, the incidence is increased to 50% to 80% of women and 10% to 17% of men.93,111 This increase in iron deficiency may reflect iron loss through gastrointestinal bleeding20,22,88 or urinary iron loss through hemolysis.20,56 Iron deficiency has multiple impacts on exercise ability. As noted previously, a lower hematocrit decreases exercise ability. However, iron deficiency also has a negative effect on exercise beyond a decrement in hematocrit. Studies have shown that repletion of iron improves . Vo2max, exercise endurance, and strength, suggesting that lack of tissue stores of iron is detrimental.15–17,47,111 Iron deficiency

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has also been shown to impair cold tolerance, perhaps because of alteration in thyroid hormone metabolism.7,14 Going to altitude puts additional stresses on body iron stores. Although the initial increase in hematocrit at altitude is due to contraction of plasma volume, red cell production increases several days later. Studies have shown that after as little as 1 week at altitude, serum ferritin falls as iron is consumed to make more red cells.8,57,107 For example, Berglund and colleagues8 showed that after 10 days of breathing 14% oxygen, a 10% increase in hemoglobin was associated with a 46% decrease in ferritin. Although serum ferritin is the best test for iron deficiency, the range of “normal” listed on the laboratory report may not be the most appropriate level for athletes. Improvement can be seen in exercise ability and fatigue with ferritin above 50 ng/dL.131 Climbers with low measured ferritin may not be able to mount an adequate hematocrit response to altitude and may have impaired exercise ability. In one study, climbers with ferritin measured above 50 to 100 ng/dL were the ones who performed best.107 In theory, 250 mg of storage iron are required for every 1 g/dL increase in hemoglobin; that amount of iron is equivalent to 25 to 32 ng/dL of serum ferritin. It has been suggested that an “ideal” hemoglobin for altitude should be 2.5 g/dL higher than the usual range; increasing the hemoglobin by that amount would require a serum ferritin of 62 to 80 ng/dL.8 Iron replacement therapy should be prescribed for any person with ferritin under 50 ng/dL who is planning a high- or extremeperformance expedition, or if the ferritin is under 100 mg/dL in a patient planning a prolonged trip to altitude. The best method of iron replacement is still controversial. One approach is to start with 1 pill that contains at least 60 mg of elemental iron every day, and if that is tolerated after 1 week, moving up to 2 pills per day. Taking the pills with vitamin C can aid absorption. The subject should avoid certain foods, such as fiber and tea, within several hours of iron ingestion. People who cannot tolerate or absorb oral iron can have intravenous iron therapy. Currently, either iron sucrose or iron glucose can be used intravenously; these preparations are safer than iron dextran.44

Hemolytic Anemias. Many patients have well-compensated congenital hemolytic anemias. The laboratory findings are mild to moderate anemia with elevated reticulocyte count, indirect bilirubin, and lactate dehydrogenase. Red cell membrane defects, such as hereditary spherocytosis, are the most common causes of inherited hemolytic anemia. Any patient with hemolysis is prone to folate deficiency, so adequate intake (400 to 800 µg/day) should be part of nutrition planning. Patients with hemolytic anemia may have increased hemolysis with fevers. The incidence of gallstones is also increased, and consideration should be given to obtaining screening ultrasonography before prolonged expeditions away from medical care. Glucose-6-Phosphate Dehydrogenase Deficiency. Glucose6-phosphate dehydrogenase (G6PD) deficiency is an important cause of hereditary hemolytic syndromes with wilderness implications.9 G6PD deficiency is sex linked and thus most commonly affects men. The defect is in the hexose monophosphate shunt and renders the red cell unable to withstand oxida-

Box 29-1. Drugs That May Precipitate a Hemolytic Crisis with G6PD Deficiency Acetanilide Dapsone Furazolidone Isobutyl nitrate Methylene blue Nalidixic acid Naphthalene Nitrofurantoin Pamaquine

Phenazopyridine Phenylhydrazine Primaquine Quinolones Sulfacetamide Sulfamethoxazole Sulfanilamide Sulfapyridine

tive stress. Most people with this disease have hemolysis only with such stressors as infections and intake of oxidative drugs. There are two main subtypes—African and Mediterranean. In the African type of G6PD deficiency, the enzyme is unstable and older cells have diminished activity. Therefore, when these patients have hemolysis, it is self-limited because as the reticulocyte count increases, G6PD activity returns to normal. The Mediterranean type is caused by a defective enzyme and tends to be more severe, because with oxidative stress the G6PD activity does not increase as the reticulocyte count increases, and fatal hemolysis may result. G6PD deficiency is of concern because many drugs used in travel medicine can cause sudden and severe hemolysis. A list of such drugs is given in Box 29-1. Many patients are unaware that they are G6PD deficient; their first symptom may be fulminant hemolysis with antimalarial drugs. In the field, acute hemolysis presents as back pain and dark urine. Management consists of stopping the suspect drug and hydrating the patient. Ingestion of fava beans (an oxidative stress) in patients with the Mediterranean type of G6PD deficiency may cause severe, potentially fatal hemolysis.

Sickle Cell Anemia and Trait. Eight percent of African Americans and 0.08% to 0.5% of whites have sickle cell trait.45,84,117 It is mostly clinically silent, although there is a potential for problems in the wilderness. Sickling can occur in patients with the trait under moderately hypoxic conditions at altitudes of greater than approximately 1830 m (6000 feet). Multiple case reports describe splenic crisis occurring at altitude or during airplane travel.45,84 Patients present with acute onset of severe left upper quadrant pain that may have a pleuritic component, nausea, and vomiting. Therapy is descent, oxygen, and pain control. In rare cases of large splenic infarction, splenectomy may be required. Patients with sickle trait are more prone to dehydration because of a renal concentration defect. Maintenance of adequate fluid intake is very important. Because patients cannot maximally concentrate their urine, the color of the urine cannot be used as a guide to hydration. If diarrhea or vomiting develops in patients with sickle trait, close attention should be paid to hydration status. Concern about the risk of “sudden death” in people with sickle cell trait with strenuous exercise is valid. Data collected in the 1960s from army recruits in boot camp showed a 28-fold increased risk of death (absolute risk, 1:3200).116 Review of these cases revealed that most patients had heatstroke, with resulting severe rhabdomyolysis causing death. Practical advice

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TABLE 29-5. Guidelines for Factor Replacement SITE OF BLEED Joint Muscle Oral Nose Gastrointestinal Genitourinary Central nervous system Surgery/trauma

DESIRED PLASMA FACTOR LEVEL

HEMOPHILIA A: DOSE OF FACTOR VIII CONCENTRATE

80% acutely, then 40% every other day until resolved 40%–50%

40 U/kg initially, then 20 U/kg every other day until healed

80 U/kg initially, then 40 U/kg every other day or third day as needed

20–40 U/kg per day until healed 50 U/kg* 40–50 U/kg, then 30–40 U/day

40–60 U/kg, then 20–30 every other day as needed 100 U/kg* 80–100 U/kg, then 35–40 U/day

50 U/kg, then 30–40 U/kg per day

100 U/kg, then 30–40 U/day

50 U/kg, then 30–40 U/kg per day

100 U/kg, then 30–40 U/day

50 U/kg, then 25 U/kg every 12 hr

100 U/kg, then 50 U/kg every day

50 U/kg, then 40–50 units every 12 hr, adjusted according to healing

100 U/kg, then 50 U/day, adjusted according to healing

100%* Initially 80%–100%, then 30% until healing Initially 100%, then 50% until healing Initially 100%, then 30% until healing Initially 100%, then 50%–100% for 14 days Initially 100%, then 80%–100% until wound healing begins, then 30% until suture removed.

HEMOPHILIA B: DOSE OF FACTOR IX CONCENTRATE

*Antifibrinolytic agents are useful for oral bleeding. Note: For severe or persistent minor bleeding, factor levels should be followed. Modified from DiMichele D, Neufeld EJ: Hematol Oncol Clin North Am 12:1315–1344, 1998, with permission.

for patients with sickle cell trait is to be cautious about dehydration and avoid strenuous exercise in the heat, especially if they are deconditioned. Patients with sickle cell anemia often have end-organ damage, which may complicate wilderness travel. Older patients may have chronic pain syndromes due to multiple bony infarcts. The leading cause of overall mortality in adults is complications of pulmonary hypertension, which result in hypoxia and impaired lung function. Pain crises are unpredictable but can be provoked by heat extremes, dehydration, or hypoxia—all features found in wilderness travel. Patients with sickle cell anemia who are going on limited trips to the wilderness need to be reminded about the importance of adequate fluid intake and to bring sufficient pain medicine to manage both chronic pain and any crisis. When considering longer-term or adventure travel, patients should be screened for pulmonary hypertension. Patients should be reminded to be compliant with folic acid supplementation. Because most adults with sickle cell anemia are functionally asplenic, they should take the same precautions as outlined later for asplenic patients.

Hemophilia Deficiency of factor VIII or IX occurs in 1 of 10,000 males. Patients with severe hemophilia are at risk for severe bleeding even with minor trauma. Bleeding most often occurs in muscles and joints, but intracranial hemorrhage is the leading cause of fatal hemorrhage. Patients can have severe arthritis due to repeated bleeding. A rough rule is that patients with less than 1% of normal levels of factor VIII or IX can have spontaneous bleeding, those with 1% to 15% of normal levels may have bleeding with minor trauma, and those with greater than 15% of normal factor levels may have bleeding with major trauma. Factor concentrates to correct the coagulation defects are factor VIII for hemophilia A and factor IX for hemophilia B. A suggested dosing scheme is given in Table 29-5. The World

Box 29-2. Factors That Do Not Require Refrigeration Factor VIII Recombinant ReFacto Hemophil M Monarci-M Koate DVI

Alphanate Factor IX BeneFix Mononine Alphanine Profilnine SD

Hemophilia Foundation website is an invaluable guide to resources available for travelers (www.wfh.org). Hemophilia does not preclude travel or expedition travel. However, patients with hemophilia who are planning travel should take factor replacement with them, especially if they will be away from health care facilities. Only certain factors listed in Box 29-2 can be stored without refrigeration. The patient should also have the supplies necessary to inject the factor, such as alcohol wipes and needles. At least one member of the traveling party should also be trained to infuse factor in case the patient is incapacitated. The biggest functional limitation to the patient with hemophilia is joint disease. Arthritis due to joint bleeds is very common and can be disabling. Joint bleeds can occur with minor injuries or ankle twists. Before travel, patients should work to strengthen their muscles to provide joint protection. Simple measures to prevent ankle sprains, such as wearing hightop boots, should also be used. Damaged joints should be splinted to prevent reinjury.

von Willebrand’s Disease The most common inherited bleeding disorder is von Willebrand’s disease, which may affect up to 1 of 1000 people.

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It is characterized by easy bruising and mucocutaneous bleeding. Joint bleeding is unusual for most patients. Patients with von Willebrand’s disease can have significant bleeding with trauma. There are multiple types of von Willebrand’s disease, but the 80% of patients with type 1 respond to desmopressin, which is available as a nasal spray (Stimate; ZLB Behring, King of Prussia, PA). The dose of Stimate is one squirt in each nostril, with the effect lasting up to 24 hours. The physician needs to be specific when prescribing Stimate because generic nasal desmopressin that is used for enuresis has too little desmopressin per dose to be effective for bleeding disorders. Estrogen can also raise levels of von Willebrand factor; the use of oral contraceptives can normalize levels in mildly affected women. The patient with rarer types of von Willebrand’s disease may require specific replacement therapy with Humate-P, a factor concentrate that contains von Willebrand factor. Unfortunately, this concentrate must be refrigerated.

Thrombocytopenia Immune thrombocytopenia is the most common autoimmune hematologic disease; it occurs in 1 in 50,000 people. Patients with modest (>30,000 platelets/µL) thrombocytopenia are at no greater risk for bleeding except with extreme trauma, and no specific precautions are needed. Patients with chronic immune thrombocytopenia and stable platelet counts can be cleared for wilderness travel. For the patient with a history of recurrent severe thrombocytopenia who is planning prolonged travel, the onset of petechiae and bleeding can be treated with a pulse dose of dexamethasone (40 mg orally × 4 days). There are multiple causes of congenital thrombocytopenia and platelet function defects. Some patients have mild thrombocytopenia with no bleeding defects, whereas others may have both platelet number and function defects. One such group of patients has mildly decreased platelets (75,000 to 150,000/µL) but no bleeding defects. These patients require no special precautions. Most patients with congenital platelet defects have a mild bleeding diathesis. Many of these patients respond to desmopressin and can carry the nasal form (Stimate) with them.

Anticoagulation The indications for chronic anticoagulation are increasing, especially because of recommendations for lifelong anticoagulation for idiopathic and recurrent deep venous thrombosis. The patient on warfarin and other oral anticoagulants poses special challenges. Fluctuating amounts of vitamin K in the diet, increased exertion, and potential travel-related illness can dramatically alter the level of anticoagulation. Unless the patient has access to a point-of-care international normalized ratio (INR) monitor, there may be no way to monitor the level of anticoagulation. Patients with a stable INR can safely go several weeks without an INR check. However, this assumes that the diet is the same as their regular diet and there are no concurrent illnesses. For patients who plan to travel longer or for those who will be away from health care, the use of point-of-care INR monitors should be strongly considered. The patient should be very familiar with the machine’s operation and be able (or have a nomogram) to adjust warfarin dose. A suggested nomogram is given in Table 29-6. Vitamin K tablets should also be carried to allow treatment of very high INR. Another option for longterm therapy is to consider the use of low–molecular-weight (LMW) heparin injections. Dosing is weight based and does not

TABLE 29-6. Maintenance Warfarin Adjustment Nomogram INTERNATIONAL NORMALIZED RATIO (INR) 1.1–1.4 1.5–1.9 2.0–3.0 3.1–3.9 4.0–5.0 >5.0

DOSE CHANGE Day 1: Add 10–20% TWD Weekly: Increase TWD by 10–20% Return: 1 Week Day 1: Add 5–10% of TWD Weekly: Increase TWD by 5–10% Return: 2 Weeks No change Return: 4 wk Day 1: subtract 5%–10% TWD Weekly: reduce TWD by 10%–20% Return: 2 wk Day 1: no warfarin Weekly: reduce TWD by 10%–20% Return: 1 wk Stop warfarin until INR 4 to 6 hours) travel, with a higher risk for travel times over 8 hours.1,64,124 The absolute risk for thrombosis is uncertain. For example, the overall risk for symptomatic pulmonary embolism is estimated to be 0.4 per million passengers, rising to 4 per million in the highest-risk group.73,103 In contrast, small prospective trials showed a calf vein thrombosis rate of 2% to 10%.114,115 The presence of risk factors, such as history of deep venous thrombosis or underlying hypercoagulable state, is important. Up to 70% to 90% of persons with thrombosis had other risk factors for thrombosis.62,85 The pathogenesis of “traveler’s thrombosis” is controversial. Venous stasis appears to be the primary risk factor. Prolonged sitting is a risk factor for thrombosis, perhaps through increased venous stasis. Although mild hypoxia due to the low cabin air pressure is often blamed in the popular press, there are no data showing activation of coagulation with mild hypoxic exposure.31 Preexisting risk factors for thrombosis are also important. As noted previously, most studies indicate that people who experience travel-related thrombosis have other risk factors, such as history of thrombosis or estrogen use. The combination of thrombotic risk factors and long travel duration raises the risk of thrombosis by 16-fold.85 The best method of prophylaxis is controversial. Ideally, people should try to be up and exercising their legs at least once an hour. However, given the crowded cabins and today’s secu-

Chapter 29: Chronic Diseases and Wilderness Activities

Box 29-3. Risk Factors for Traveler’s Thrombosis Age > 65 years Cancer Estrogen use History of lower extremity deep venous thrombosis Hypercoagulable state Lower leg cast Obesity (>2× ideal body weight) Recent surgery (previous 6 weeks) rity climate, this is unrealistic. Aspirin remains a popular recommendation but has been demonstrated in a randomized trial not to be effective for preventing traveler’s thrombosis.21,49 Elastic stockings provided protection in trials, but have the side effects of discomfort and superficial thrombosis.115 A single prophylactic dose of LMW heparin is effective, but is inconvenient for most people. A reasonable approach is first to assess a patient’s risk of thrombosis when traveling by plane for over 6 hours (Box 29-3). For most low-risk people, one could encourage foot movement and avoiding dehydration. For medium- and highrisk patients, stockings should be recommended. The feasibility of adding LMW heparin on a case-by-case basis for high-risk patients also should be considered.

The Asplenic Patient Asplenic patients pose unique travel risks. Asplenic patients are at risk for overwhelming infections from a diverse group of infectious agents. The risk of overwhelming sepsis varies by indications for splenectomy, but the lifetime risk appears to be approximately 1%.10,71 The use of pneumococcal vaccine and recognition of this syndrome have helped lessen the risk, but travel can expose the asplenic person to novel infectious organisms. The classic bacterial pathogen is the pneumococcus, but in older patients gram-negative bacteria are a common cause of infections.36 Unusual organisms causing overwhelming infections, such as Capnocytophaga from dog bites or Babesia from ticks, have been reported.32,133 Asplenic patients need to be counseled about the risk of infections and should be vaccinated for pneumococcus, meningococcus, and Haemophilus influenzae.53,91 Patients previously vaccinated for pneumococcus should be revaccinated every 3 to 5 years.71 In addition, because of concerns about greater severity of malarial infection, they should be scrupulous with antimalarial prophylaxis.83,96 The role of prophylactic antibiotics is controversial for adults, but patients younger than 18 years of age should always take penicillin VK 250 mg twice daily, especially when traveling. Patients should be advised to start antibiotics and seek medical care if they develop a fever, shaking chills, or lower respiratory track infection. A reasonable oral antibiotic for self-medicating is amoxicillin/clavulanic acid 875/125 mg twice a day. Patients who are bitten by dogs should also take antibiotics. Asplenic patients should wear an identification bracelet to alert health care providers.40

Oncology The numbers of cancer survivors is increasing, and many of these patients pursue wilderness activities. Chemotherapy can lead to short-term side effects such as nausea and neutropenia,

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Box 29-4. Chemotherapy Agents: Long-Term Side Effects CARDIAC DYSFUNCTION

Anthracyclines (doxorubicin, daunorubicin, epirubicin, mitoxantrone, idarubicin)* PULMONARY TOXICITY

Bleomycin* Nitrosoureas* Cyclophosphamide Methotrexate NEUROPATHY

Cisplatin* Oxaliplatin* Vincristine* Taxol* RAYNAUD’S PHENOMENON

Bleomycin Cisplatin *Common.

but many side effects can last months or years after chemotherapy has ended.

Chemotherapy Common side effects of most chemotherapeutic agents are nausea and bone marrow suppression. The nausea is short term and managed with 5-hydroxytryptamine (5-HT3) blockers such as ondansetron 8 mg orally (PO) or granisetron 1 mg PO. The highest-risk time for neutropenia is usually 10 to 21 days after chemotherapy. Patients may want to hike or go camping in between chemotherapy sessions. Neutropenic patients can be cleared for this type of activity as long as they can seek medical care if they become febrile. A good rule of thumb is that patients should not be more than 2 hours away from an emergency department. The vast majority of infections are due to endogenous organisms and not from the environment, but some precautions include wearing a mask when in crowded areas and avoiding ingestion of fresh fruits or vegetables. Thrombocytopenia is rare with most chemotherapy regimens. Platelet transfusion should be performed only for platelet counts under 10,000/µL. Chemotherapy can cause a variety of long-term side effects (Box 29-4). Anthracyclines such as Adriamycin can lead to cardiac damage that may be well compensated until another stressor, such as altitude, is added. The risk for chronic heart failure is highest with doses over 300 mg/m2, but can be seen with any dose. Agents such as vincristine can lead to neuropathy that causes loss of dexterity. Of particular concern is bleomycin, an antineoplastic agent that is part of a curative regimen for both germ cell tumors and Hodgkin’s disease. Bleomycin can lead to subtle lung damage that results in loss of diffusing capacity. For very competitive athletes with germ cell tumors, effective non–bleomycincontaining regimens can be used.97 Bleomycin can also interact with high concentrations of oxygen, causing a fulminant and fatal lung toxicity. Fatal cases have been reported many months after cessation of therapy. Controversy remains as to whether

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TABLE 29-7. Post–Bone Marrow Transplantation Vaccine Recommendations VACCINE Tetanus toxoid Diphtheria Inactivated polio virus Pneumococcal H. influenzae Influenza Measles Rubella Hepatitis B Hepatitis A Inactivated polio Oral polio MMR Typhoid (tY21a) Varicella Yellow fever Japanese encephalitis V Meningococcal vaccine

ALLOGENEIC TRANSPLANT

AUTOLOGOUS TRANSPLANT

TIMING

Recommended Recommended Recommended Recommended Recommended Recommended No earlier than 24 mo No earlier than 24 mo

Recommended Recommended Recommended Recommended Recommended Recommended

6–12 mo 6–12 mo 6–12 mo 6–12 mo

LIVE?

Yes Yes 6–12 mo 6–12 mo 6–12 mo

No No No No No

earlier earlier earlier earlier earlier

than than than than than

24 mo 24 mo 24 mo 24 mo 24 mo

Yes Yes Yes Yes Yes 6–12 mo 6–12 mo

Information from references 65, 79, 82, 117, 119.

patients who have had bleomycin can safely go scuba diving because of the high pressures of oxygen in tank mixtures. For example, during a dive to 20 m (66 feet), the partial pressure of inhaled oxygen is 0.63 atm; at 30 m (98 feet), it is 0.84 atm.63 Patients who have received bleomycin should wear an identification bracelet in the event that emergency surgery should be required, so that the lowest possible oxygen concentration may be used. The cancer survivor who plans to travel on a high-altitude or extreme-performance expedition should undergo careful screening. Patients who have received anthracyclines should have cardiac function screened; pulmonary function testing should be done in patients who have received bleomycin or other potential pulmonary toxic agents. Any patient who has received upper chest or neck radiation should have thyroid function screened. Certain agents used for hematologic malignancies, especially chronic lymphocytic leukemia, can lead to profound and prolonged T-cell immunosuppression that persists months to years afterward and puts these patients at risk for unusual infections. These agents are fludarabine, cladribine, and alemtuzumab. The degrees of immunosuppression can be monitored by measuring CD4 counts. Patients with counts under 200/µL are severely immunocompromised and travel is not recommended.23,112 Patients with higher CD4 counts still may have residual immunosuppression and be prone to herpes zoster outbreaks for years after chemotherapy.

The Stem Cell (“Bone Marrow”) Transplant Recipient Stem cell transplants are increasingly common therapy. Currently, three different types of stem cell transplantations are performed. Autologous transplants involve harvesting and preserving the patient’s stem cells and then administering radiation or chemotherapy (conditioning) to ablate the marrow. This is followed by reinfusion of the stored stem cells. Allogeneic transplantation involves infusion of another person’s

marrow. Increasingly, nonmyeloablative allogeneic transplants (“mini-transplants”) are being used that involve only modest doses of chemotherapy and radiation to prepare the patient for transplantation. The major long-term complication of allogeneic transplantation is graft-versus-host disease (GVHD) due to the donor immune system attacking the recipient. Chronic GVHD can be a debilitating problem leading to chronic skin disease, restrictive pulmonary disease, and increased propensity for infection. When counseling the stem cell transplant recipient about travel, the physician needs to know what type of transplant the patient has received, time after transplantation, and whether he or she has GVHD. In general, a patient who has received an autologous transplant and has recovered his or her blood counts can be cleared for travel 6 months after transplantation. For the patient who has received an allogeneic transplant, the main concerns are restoration of immunity and presence of GVHD. A reasonable rule of thumb is that patients will be immunosuppressed for 12 to 24 months after they stop their immunosuppressants and should always be treated as functionally asplenic. The transplant (especially allogeneic) recipient who is considering a high- or extreme-performance trip should undergo pulmonary and cardiac screening. Timing of travel immunizations for transplant recipients is an uncertain area.35 If given too soon, the immature immune system will not mount a response. Live vaccines are also a concern if immune function is not normal. An approach is given in Table 29-7. Patients with stem cell transplants who remain on immunosuppression have special concerns. Their family members and close contacts also should not receive live vaccines for fear of disease transmission to these patients. New medications can interfere with immunosuppression. For example, erythromycin can raise cyclosporin levels to the toxic range, whereas rifampin can lower cyclosporin levels. The references for this chapter can be found on the accompanying DVD-ROM.

Chapter 30: Mental Health in the Wilderness

Mental Health in the Wilderness

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Barry Morenz Remote wilderness environments can have a salutary effect on a person’s overall emotional health. Wilderness settings are sometimes used as intensive treatment settings for adolescents with emotional and behavioral problems.8 Those who choose to pursue wilderness activities are often seeking relief from the stress of demanding and hectic urban lives. Traffic, phones, computers, deadlines, and endless chores can make the routine of daily life in an urban environment an objectionable ordeal. However, remote wilderness places can present unique stresses of their own in addition to being a refreshing change from the psychological stresses of urban life. Mental health and mental health problems might improve in the wilderness, but they can also become worse. New psychiatric problems can emerge in response to the demands of wilderness experiences. This chapter discusses the diagnosis and management (including the use of psychotropic medications) of emotional problems in the wilderness, both in people who have preexisting psychological difficulties and in those who develop new mental health problems in the wilderness. The Diagnostic and Statistical Manual of Mental Disorders, 4th edition, Text Revision1 (DSM-IV-TR) is the most recent, exhaustive, and widely used compendium of psychiatric disorders. However, most mental health problems can be thought of as falling into six broad disorders: anxiety, mood, psychotic, organic mental, personality, and substance abuse. Specific diagnostic assessment using the DSM-IV-TR and psychological testing in a wilderness setting is not crucial or practical. However, appropriate triage and management in a wilderness setting depends on being able at least to classify emotional and behavioral problems as falling into one or more of these broad categories. The first stage of diagnosis in the wilderness setting is to separate the normal from the abnormal, a task that may not be simple in many cases. It is not straightforward to differentiate what may be considered a normal adaptive response to the challenge of a wilderness experience from responses that are maladaptive and may signal the onset or exacerbation of a preexisting psychiatric problem. For example, at the end of a physically challenging day of backpacking with a group, one member of the group may break down in tears. Such crying may be a healthy and adaptive response. The process of crying might relieve stress and result in the member receiving needed emotional support. Alternatively, such tears may suggest the person feels mentally and physically overwhelmed. The person might be approaching a panic state, and if appropriate interventions are not undertaken the person’s mental state will deteriorate. The challenge is to determine whether a pat on the back, a hug, and some encouraging words are all that is needed, or if the

individual has to be assisted out of the wilderness as soon as possible to prevent emotional decompensation or prevent the person from becoming unsafe for the group or themselves. In the following sections, five important topical areas for the assessment and management of emotional problems in the wilderness are discussed: (1) the common characteristics of the six major categories of psychiatric disorders most likely to be seen in the wilderness; (2) suicide and violence potential; (3) common complaints, such as insomnia, fatigue, headache, and other somatic complaints; (4) response to crisis (disasters and survival psychology); and (5) leadership and group process.


PSYCHIATRIC DISORDERS Anxiety Disorders Anxiety is a human emotion that is often experienced and is usually a normal and adaptive response to everyday life. Anxiety is an emotion that motivates us in myriad ways—for example, to complete tasks, study for tests, have a reliable belay partner when rock climbing, and work to earn a living. The experience of anxiety is physical as well as psychological. Increased heart rate, blood pressure, and respirations, in addition to sweaty palms and muscular tension, are common physical components of anxiety that are present along with a feeling of psychological tension. Rarely is anyone totally free of anxiety, but for most people anxiety is mild. There are many ritualized, socially condoned means of diminishing this everyday form of anxiety, including activities such as jogging, athletics, hot tubbing, drinking alcohol, and sexual activity. In some circumstances, an extreme form of normal anxiety is triggered in normal people and is sometimes referred to as “the fight-or-flight response.” This response occurs automatically without conscious control in some forms of competition and in response to immediate danger. Athletes, extreme sports enthusiasts, military combatants, crime victims, or people in any context confronting potential serious injury or death will have their fight-or-flight system triggered. This system is mediated through the autonomic nervous system and is a survival adaptation. When our autonomic nervous system is triggered, a variety of physical and mental changes take place. Blood is diverted from internal organs to the skeletal musculature, and heart rate, blood pressure, and respirations dramatically increase. A person in a fight-or-flight state often acts with little or no reflective thinking to preserve his or her life or the lives of others. Memories may be unreliable during these episodes because an individual is often on “automatic pilot.” These

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episodes of autonomic arousal in response to danger or competition are normal. However, some people develop poorly modulated anxiety that interferes with their ability to enjoy life, complete everyday tasks, and respond appropriately to danger. As anxiety begins to interfere with an individual’s functioning, then the anxiety is more likely to be pathologic and might reflect an anxiety disorder. There are several types of anxiety disorders, including generalized anxiety disorder, specific phobias, panic disorder, obsessive-compulsive disorder, and acute and post-traumatic stress disorder (discussed in the section on Response to Crisis, later). The essential feature of each is troublesome manifestations of anxiety. People with generalized anxiety disorder worry a lot. Their anxiety is far out of proportion to what most people would experience in similar circumstances. The individual afflicted may find it difficult to keep worrisome thoughts from interfering with attention to current activities. The focus of the worries in people with generalized anxiety disorders are everyday circumstances, such as getting up on time for work, making appointments, and doing chores. The focus of the worry often migrates from one topic to another. Troubling anxiety plagues these individuals most of the time. People with this type of disorder experience somatic symptoms such as sweating, nausea, and diarrhea. The prevalence of generalized anxiety disorders is approximately 2% to 7%, and the condition is more common in women.9 Individuals with a generalized anxiety disorder in a wilderness setting will probably find a new set of preoccupying concerns: bear attacks, getting lost, not keeping up, flash floods, and so forth. These anxieties will likely diminish the person’s enjoyment of a wilderness experience, affect their focus, and drain their energies. Another deleterious effect of someone with abundant anxiety is a negative impact on a group’s ability to work together and enjoy their wilderness experience. In most cases, these types of anxiety problems do not represent emergencies. They are chronic problems that can be managed in the field. Good leadership can prove extremely valuable in this type of circumstance.4 A person with a generalized anxiety disorder needs ample reassurance. A good leader can provide such reassurance and appoint another supportive member of the wilderness team to assist. Modeling constructive behaviors with an anxiety-ridden participant can help other members learn how to deal with him or her. Building rapport and trust with the afflicted person is a good first step to helping them. A bit of humor, uncritical listening, and simple reassurance may be sufficient. It is not worth trying to talk someone out of his or her worries because it is unlikely to be productive and could consume a group’s energies. In the field, a benzodiazepine such as lorazepam (Ativan) may be useful.11 Side effects include sedation, memory difficulties, and impairment in motor coordination. Sustained use can lead to physical dependence and withdrawal symptoms on abrupt discontinuation. Thus, such medications must be used cautiously in the field. However, they can be very helpful for short-term relief of anxiety-related symptoms. Probably one of the more common specific phobias encountered on a wilderness outing is fear of heights or exposure (to an edge with a drop-off). Other common phobias are to snakes, spiders, and water. A specific phobia is an unreasonable fear in anticipation of or exposure to a particular object or situation.1 The intensity of anxiety with the exposure may vary from relatively mild to extreme panic. In some instances, a phobia to

heights may not be possible to overcome in the wilderness. For instance, a trail that crosses a bridge over a chasm or has a section of precipitous exposure might be more than an individual with a specific phobia to heights can manage. In this instance, it may be necessary to find another route. Sometimes, gentle reassurance or distraction may be all that is required. The author has sometimes been successful in engaging height-phobic people in distracting conversations while backpacking in areas with dizzying exposure. However, if an individual was likely to respond with extreme anxiety, then it would not be safe to use such psychotherapeutic measures. As with a generalized anxiety disorder, benzodiazepines can be useful in the field for these individuals,11 but because they have side effects of sedation and may disturb motor coordination, they should not be used when an individual must be alert and maintain full physical abilities. People with reasonably well-controlled panic disorders may venture out into the wilderness and find their symptoms becoming worse. Individuals with panic disorders experience recurrent, unexpected panic attacks. A panic attack occurs during a discrete period of time lasting approximately 10 to 30 minutes and is manifested by several of the following symptoms: a pounding heart, sweating, trembling, chest pain, nausea, dizziness, numbness, chills, hot flushes, and shortness of breath. During a panic attack, a person may fear that he or she is dying, having a heart attack, going crazy, or losing control. Such individuals often visit emergency departments fearing they have had a heart attack or that something is seriously wrong with them physically. Any person with one of the anxiety disorders described in this section may experience a panic attack, but the person with a panic disorder experiences recurrent, unexpected panic attacks. These attacks occur without warning and seem to come “out of the blue,” in contrast to being in response to a specific trigger as with specific phobias described previously. As a result of recurrent attacks, people may develop avoidant behaviors because they do not want to be in situations where escape might be difficult or embarrassing, or where help might not be available (agoraphobia). When these people are caught in these situations, they have a desperate desire to flee. Agoraphobia may lead people with panic disorders to avoid leaving their homes, or they may leave only in the company of trusted companions. Panic disorders occur in approximately 1% to 2% of the population.1 Treatment with selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine or sertraline, or benzodiazepines, such as alprazolam (Xanax) or clonazepam, or a combination of the two with psychotherapeutic intervention can be successful in controlling panic disorder and agoraphobia.10 People with panic disorder whose symptoms are not problematic may safely enjoy a wilderness adventure without difficulty. However, remote locations, bad weather, or physical challenges may increase the stress on such individuals, causing them to experience a resurgence of symptoms. Having panic attacks in the wilderness may precipitate agoraphobia. It is also possible for people to begin to have panic attacks and agoraphobia symptoms for the first time on a wilderness adventure. The afflicted person may want to escape from the wilderness and may be completely intolerant of being left alone, even for brief periods. People having a panic attack in the wilderness may present a diagnostic dilemma. They may look like they are having a heart attack or acute respiratory distress caused by pulmonary edema. A careful history indicating the person has a history of panic disorder and does not have a history of heart disease may help.

Chapter 30: Mental Health in the Wilderness However, for an older person, who may have risk factors for heart disease such as smoking, diabetes, or obesity, the distinction between panic disorder and symptoms of a myocardial infarction may be nominal. People who have a panic attack usually begin to calm down within 30 minutes to an hour. Symptoms often respond to benzodiazepines such as lorazepam, reassurance, and support. It may be important to avoid leaving such people alone, but they should not be crowded either. Providing regular doses of benzodiazepines to an individual with a panic disorder or increasing the dosage of currently prescribed benzodiazepines may be enough to allow completion of the trip. However, people with intense and recurrent panic attacks with agoraphobia may not be able to function on a wilderness trip and may have to be assisted out of the wilderness or evacuated if judicious use of lorazepam, reassurance, and emotional support does not help. It is also important to keep in mind that benzodiazepines can be sedating and adversely affect motor coordination. This is also true of SSRIs, but to a lesser extent. A person on a wilderness trip is observed constantly stopping to wash his or her hands in a stream or lake, or with water they are carrying. The person’s hands are observed to be raw from frequent washing, and the time consumed in this activity is slowing the group’s progress to a crawl. When confronted, the individual apologizes and acknowledges that the behavior is irrational, but explains that he or she is deathly afraid of germs and cannot cease the behavior. The obsessions and compulsions of a person with obsessive-compulsive disorder (OCD) are usually seen as irrational by the person experiencing them, but at the same time he or she feels helpless to stop them. If a person with OCD is prevented from performing ritualistic compulsions, he or she may experience full panic attacks or near panic. The obsession of the compulsive hand washer is preoccupation with contamination by germs, and the compulsion is hand washing. Another person on a wilderness trip is frequently overheard counting in a whispered voice. When asked about the counting, the individual (with considerable embarrassment) explains that they are afraid they will attack someone, so every time they have a violent thought they count to 100. A person with OCD may not be able to adhere to the requirements of a wilderness trip. For instance, the chronic hand washer may slow a group so profoundly that it cannot make reasonable progress. The example of the person who tries to control his or her anxiety about acting violently by counting may present less of a problem. People with OCD are not typically violent, but a person who is observed to be constantly counting to ward off violent behaviors may have difficulty comfortably fitting in with a group. In the general population, the prevalence of some manifestation of OCD is greater than 1%, but the symptoms often vary in intensity.9 People with OCD are often successfully treated with SSRIs, such as fluoxetine or sertraline.10 The symptoms may not be totally eliminated, but they are diminished in intensity with treatment. It is unlikely that OCD symptoms will suddenly erupt on a wilderness trip. It is more likely that preexisting symptoms will increase under the stress of a wilderness experience. Frank disclosure to a wilderness group about the OCD symptoms of a member of the group can diminish the group’s anxieties about the person’s odd behaviors and make the afflicted person less likely to be isolated by the group.

Mood Disorders Everyone experiences sadness, moodiness, happiness, and elation at different points during the course of their lives. Such

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moods are a normal part of human experience. Periodically, such emotions become extreme and prolonged and interfere with normal functioning. It is unlikely that people with severe depression or unstable bipolar disorder (manic-depressive illness) will venture into the wilderness. However, people who are being successfully treated or who have relatively mild symptoms may participate in wilderness adventures. The wilderness experience may improve or worsen mood disorder symptoms. People who are depressed feel sad, useless, and bad about themselves and the world. Their view of the world is dark and they have difficulty believing things will get better. Depressed people have difficulty sleeping, lose appetite, have poor energy, lose concentration, withdraw socially, and have difficulty enjoying anything. They may cry for no apparent reason. The most common diagnostic term for this type of depression is major depression, and the prevalence of this disorder is approximately 5%.9 At their worst, people with severe depression may become psychotic and suicidal (see sections on Suicide and Violence Potential and Psychotic Disorders).1 However, people who are having relatively mild problems are unlikely to develop severe symptoms rapidly; severe symptoms gradually appear over a period of weeks or months. The more likely problem on a wilderness adventure is someone who started with mild symptoms that are gradually growing worse. Such individuals may already be taking antidepressant medications (typically, SSRIs like escitalopram [Lexapro] or paroxetine [Paxil]). These medications work slowly over a period of weeks, so a change in dose in the midst of a wilderness trip probably would not provide significant benefit. The most common problem the wilderness group may face with a depressed person is overall impact on group morale. Emotional outbursts, crying for no apparent reason, or offhand comments about suicide will likely concern and distress others in the group. If group members provide encouragement and emotional support, this may help the depressed person get through the trip safely without too negative an impact on morale. However, severe symptoms may not respond to ordinary support. Lack of response can anger others, who may begin to feel conflicted because they recognize that they are punishing someone who is already suffering. If this is the case, it becomes necessary to hasten the depressed person’s departure from the wilderness, especially if there is suicidal ideation. Persons with bipolar disorder experience major depression alternating with mania over a period of months, often with periods of normal functioning between abnormal episodes. The prevalence of bipolar disorder is approximately 1%.9 During periods of normal mood or in the early stages of a manic phase (hypomania), bipolar persons may participate in wilderness adventures with no difficulty. During a period of hypomania, a person is very positive, productive, hard working, energetic, and expansive. But as the person becomes manic, problems become readily apparent. There is often rapid, pressured speech that is difficult to interrupt. Sufferers might not sleep at all, be excessively gregarious, and begin to believe they have superhuman powers. An individual may try to awaken a wilderness group in the middle of the night to hike up a nearby peak. When rebuffed, the manic person might take off alone with no water or protection from the weather because of the belief that he is superhuman. An individual who has become manic in the wilderness may present an extreme hazard to himself and possibly the group. Once manic, a person no longer listens to reason or will not listen for long. An individual with mania in

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the wilderness should be considered a medical emergency and be evacuated as rapidly as possible. Careful questioning may reveal the person was taking psychiatric medications, such as mood stabilizers (lithium or divalproex [Depakote]) or antipsychotic medications (risperidone [Risperdal] or olanzapine [Zyprexa]), or both. People who take lithium must avoid dehydration, which results in lithium toxicity. Lithium toxicity begins with tremulousness and can proceed to seizures and death. If lithium toxicity is suspected, the drug should be stopped and the person should be well hydrated. The patient may need dialysis to resolve the toxicity, so evacuation should be strongly considered. People with bipolar disorders sometimes stop their medications because they enjoy how they feel when they are hypomanic. If the person is willing, use of benzodiazepines like lorazepam or antipsychotic medications like risperidone can begin to control some of the symptoms. Risperdal 2 to 6 mg or lorazepam 4 to 8 mg spread over the course of a day may be needed to keep such an individual calm.10 There is a likelihood that the person will not cooperate in taking medications because he or she enjoys the high of being manic. It may be possible to coax a manic person out of the wilderness through encouragement and enticements. Confrontation is unlikely to produce beneficial results because people with mania tend to be extremely irritable and sometimes aggressive. If they have any weapons, these should be removed. People in a manic episode can go for days without sleep. If they will not voluntarily leave the wilderness, then help should be obtained as soon as possible. An evacuation may require the individual to be forcibly restrained and medicated. While waiting for help to arrive, members of the group should do whatever they can to contain the manic individual’s excesses in order to keep the person and the group safe. Such an individual should be monitored constantly.

Psychotic Disorders Individuals with severe mental illnesses, such as schizophrenia or schizoaffective disorder, do not typically venture into the wilderness, especially if they are in a deteriorated state. Their overall functioning is too low for them to organize themselves to the point that they could join a wilderness group. Yet some have been able to benefit from treatment, usually in the form of antipsychotic medications. The 1% prevalence of schizophrenia worldwide is significant.9 Tragically, the illness often presents in young adulthood. The hallmark of these disorders is a substantial period, at least 1 month, during which the individual becomes psychotic. An individual who has lost the ability rationally to perceive reality is psychotic. This individual experiences delusions, which are false beliefs not based in reality, and hallucinations, which are sensory perceptions without a sensory stimulus. A person who believes a sinister group worshiping the devil has implanted a transmitter in his mouth (delusion) and hears mysterious people talking about him saying he is pathetic and should kill himself (auditory hallucination) is considered psychotic. There are many types of delusions and hallucinations, but the essential feature is a disturbance in a person’s perception of reality. People with psychotic symptoms usually cannot be talked out of their beliefs and perceptions. People who are successfully treated with medications may still have some unusual or even delusional beliefs, but these have receded into the background and are not an active concern for the individual. In addition to psychotic symptoms, people with schizophrenia or a schizo-

affective disorder often seem awkward or distant interpersonally. They might express very little emotion and have a wooden personality. Their thoughts may seem a little jumbled, disorganized, and concrete. Their motivation may be very low. If receiving adequate treatment, such individuals might enjoy a wilderness adventure with no difficulty, although their personal contribution to the group may be nominal. Antipsychotic medications cause a wide range of side effects, especially older antipsychotic medications such as haloperidol (Haldol). Side effects are many, including extrapyramidal symptoms (Parkinson’s-like symptoms that can cause considerable difficulty in moving fluidly), acute dystonias (painful involuntary muscle contractions), insomnia, sedation, and orthostatic hypotension.10 Side effects alone may preclude a person from participating in a wilderness adventure, but people who have been on their medication for weeks or months may have adapted to the side effects, and newer antipsychotic medications, such as aripiprazole (Abilify), have fewer side effects. Problems arise for the wilderness group if a member of the group becomes acutely or floridly psychotic. Symptoms may range from the mild, such as a person asking the group why they are always talking about him, to paranoid beliefs that snipers are in the woods trying to kill the psychotic individual. Very mild symptoms may be tolerable or the individual might respond to periodic gentle reassurance (reality orientation). An increase in the dosage of the individual’s already-prescribed antipsychotic medication may help, or a benzodiazepine may have a calming effect, at least temporarily. If psychotic symptoms become more severe, including progressive paranoia or agitation, or if the victim begins making bizarre accusations toward others in the group, the situation should be treated as a medical emergency and the person should be evacuated as soon as possible. Psychotic individuals’ behavior may be unpredictable and violent toward themselves or others. There are many causes of psychotic symptoms, including schizophrenia, schizoaffective disorder, mania, illicit drugs such as methamphetamine, and organic causes such as brain tumor or metabolic disturbance. In the field, it may be extremely difficult to determine the cause of psychosis, but a good history can sometimes narrow the differential considerations considerably.

Organic Mental Disorders There is a wide range of medical problems in the wilderness that can cause behavioral symptoms, ranging from, for example, mild confusion associated with high-altitude hypoxemia, to delirium associated with high-altitude cerebral edema. A person in the wilderness may have fallen and hit his or her head on a rock, initially resulting in a minor scrape and a headache, but progressing to a subdural hematoma that may become life-threatening. It is crucial to recognize signs of delirium in the wilderness. Delirium usually signals a medical emergency. A person with delirium often has a fluctuating level of consciousness, such that he or she may be awake and alert one minute and sleepy the next. Delirious persons may be hard to arouse, but then seem to come around on their own. People with delirium are often confused and disoriented to date, time, and place. Concentration, memory, and calculation ability may be impaired. Visual, tactile (“There are bugs crawling on me”), or other types of hallucinations may appear. Paranoid delusions might be reported.9 The key to differentiating delirium from psychosis without delirium is that with manic or schizophrenic psychosis, attention, alertness, and level of

Chapter 30: Mental Health in the Wilderness consciousness are preserved, and there is no fluctuation of level of consciousness. If delirium is suspected, a cause must be determined as rapidly as possible. Dehydration, hypoglycemia, high-altitude cerebral edema, head injury, meningitis, encephalitis, drug or alcohol withdrawal, and heat illness, to name a few, can cause delirium. In their confusion, people with delirium can easily injure themselves, so they must be watched constantly. If an easily treatable cause cannot be determined and treated, evacuation may become necessary. The author was involved in reviewing a Grand Canyon backpack trip down Kanab Canyon in which a member of the group became increasingly unsteady and confused as he progressed down the canyon. He would be fine for a few hours and then he would become confused. He fainted and fell a couple of times, but was not seriously injured. Other members of the group carried most of his equipment. Shortly after the group made it to the beach lining the Colorado River, the man became stuporous. Soon he was barely awake. The leader of the group raced for help and one person was left with the delirious man. As hours passed, he became semicomatose. After 24 to 36 hours, a helicopter evacuated the victim to a nearby hospital, where he was treated for pulmonary edema. Had the helicopter arrived any later, the man probably would have died.

Personality Disorders Personality disorders are psychiatric disturbances that can cause considerable difficulty in the wilderness, even though they rarely present as an emergency. Personality disorders are common, with an approximately 6% prevalence in some studies.9 There are 10 different categories of personality disorder described in the DSM-IV-TR. People with personality disorders have enduring maladaptive patterns of behavior, usually dating to adolescence. Using a narrow set of adaptive strategies inflexibly leads these individuals to have chronic problems at school, at work, and in interpersonal relationships. Ironically, people with personality disorders do not tend to see themselves as having problems but rather blame some aspect of their environment for their difficulties. They tend to blame others for their failings. As a result, others see these people as troubled and troubling. Individuals with personality disorders unwittingly create their own special circle of misery. Depression and substance abuse are common additional problems in this population. People with schizoid personality disorders are loners and tend to avoid relating to others except on a shallow and superficial level. People who are schizotypal have odd and eccentric preoccupations and manners. They may be enamored of astrology, spiritual vortices, or numerology, and they tend to relate in an awkward or uncomfortable manner. These people may not cause too many problems on a wilderness journey, but they may be annoying or aloof and unable to join in comfortably with a group. People with a paranoid personality disorder are constantly suspicious of others, believing that others have malevolent intentions toward them. The suspicions are not totally absurd, as they are with someone who is psychotic. For instance, they may believe that fellow travelers do not like them or will steal from them, but they do not believe that transmitters have been implanted in their brains or that the FBI is conspiring to kill them. A person with persistent suspicions of others can be problematic for a wilderness group, whose successful functioning depends on trust between members. Someone who is chronically suspicious may be incapable of

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establishing trusting bonds with others. Group leaders need to work doubly hard to draw such individuals into a group and avoid having the group isolate the aberrant group member. Such isolation serves only to amplify the paranoia and discomfort between the affected person and the group. Another group of personality disorders is sometimes referred to as the “dramatic and erratic” personality disorders. The narcissistic personality-disordered person is one who considers himself special and unusually talented, and therefore deserving of special praise or considerations. These are people who want to be first in line, or do not want to carry a heavy pack like everyone else. The person with a histrionic personality disorder is colorful and dramatic and demands to be the center of attention. He may be perceived as vain and shallow and often exaggerates physical complaints. A small blister may be declared to be causing excruciating pain and discomfort. The person with a borderline personality disorder is unstable and has a fragile sense of identity. Relations with a borderline person tend to be stormy because one minute she is begging forgiveness, and the next shouting expletives. The person with an antisocial personality disorder is the “confidence man” who may manipulate, intimidate, or steal to obtain what he wants. He can be superficially charming, but is irresponsible and unreliable. Sometimes an unusually talented and psychologically intuitive leader or group member is able to run interference between the afflicted person and the rest of the group. At other times, the maladjusted individual can be so disruptive that the leader or the rest of the group must insist that the person leave the group. If this is the case, the person should be assisted from the wilderness. These individuals may not willingly accept being dismissed from a group and may be combative physically or verbally. They may even become enraged and report that they are going to kill themselves, sue, or seek some other form of retaliation. Nevertheless, if the individual cannot safely function as part of a wilderness group, the leader must remain firm in dismissing the person and assisting him or her safely out of the wilderness. A third group of personality disorders that may be less problematic includes the avoidant, dependent, and obsessivecompulsive personality disorders. The person with an avoidant personality disorder is constitutionally shy and fears rejection, but desires relationships with others. The person with a dependent personality disorder is someone who looks to others to make decisions and care for them. The person with an obsessivecompulsive personality disorder is task oriented and hard working, but is also perfectionist, moralistic, and humorless. Note that the obsessive-compulsive personality disorder is to be contrasted to OCD, described previously. A combination of social support, reassurance, and humor may be all that is needed to help people with these disorders function reasonably well with a wilderness group. The person with an obsessivecompulsive personality disorder may become tiresome and tedious because of controlling and detail-oriented behavior, but may also make valuable contributions because of hard work and orientation to task. A normal person uses a range of strategies to adapt to the different challenges presented at work, at school, and in social relationships. People with personality disorders use a very limited range of strategies in an inflexible manner in all situations. It is normal and constructive to be suspicious when buying a used car, detail oriented when designing a new aircraft, and colorful at a party. But personality-disordered people have

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just one song to sing. They sing it repeatedly, even when it is not adaptive and contributes to their own unhappiness.


SUICIDE AND VIOLENCE

Substance Use Disorders

Suicide is a major public health problem. The suicide rate in the United States is approximately 12.5 per 100,000, with a recent increase in suicides among people 15 to 24 years of age.9 Depression and alcoholism are frequently associated with suicide. People who are depressed, lonely, or physically ill might commit suicide. Rejection, unemployment, and legal problems are often associated with suicide. Many factors indicate a greater potential for suicide. The factors vary with age. In the context of a wilderness trip, factors to consider are depression and recent loss. For example, a participant recently divorced, widowed, or fired from his or her job shortly before the trip may be at higher risk for suicide. A person who is isolated and lacks social support will be at greater risk for suicide. A family history of suicide or past history of suicidal behavior increases suicide risk. If there is a concern that someone might be suicidal, then they should be asked about suicidal thinking in a straightforward, concerned manner. Asking about suicide does not increase someone’s suicide risk. People who kill themselves often think about or even become preoccupied with ending their lives. They plan how they will kill themselves, so they should be asked about plans for suicide. If someone has become suicidal, it may be useful to obtain an agreement from them that they will not try to kill themselves in the wilderness. If the suicide potential is felt to be great, the person must be watched closely. People who are suicidal should be escorted out of the wilderness and brought to psychiatric help. People who are delirious or psychotic can suddenly become impulsively suicidal in the midst of their confusion and frenzy, so they must be evacuated from the wilderness as soon as possible. United States culture is much more violent than that of other industrialized nations. Each year, 4 to 5 million assaults are reported in the United States.9 Rape, child abuse, homicide, and other violent crimes are far too common. Men are much more likely to be violent than women; young men are particularly prone to violence. Substance abuse is highly correlated with violence. People who have a history of acting violently in the past are more likely to do so in the future. People who are going to be violent often signal their intentions. They act aggressively and clench their fists and jaw, or speak loudly or shout. They may have thoughts of acting violently, so they should be asked if they are thinking of hurting anyone. People who have a personality disorder, abuse drugs or alcohol, or are psychotic are at an elevated risk for violence. If a concern exists about someone being violent in the wilderness, weapons should be removed if possible and everyone should be vigilant. The psychotic or delirious person who is prone to violence should be evacuated. If the issue is substance abuse or a personality disorder, or both, the person should be asked to leave the group and assisted out of the wilderness. If the person refuses to leave the group, then help should be sought and the entire group should leave the wilderness setting.

People who abuse illicit drugs or alcohol should not be on wilderness adventures; they are a hazard to themselves and others. It is not uncommon for the wilderness traveler to enjoy a small quantity of alcohol after a long day, and this may be considered acceptable. However, if it is discovered that someone is using methamphetamines, cocaine, heroin, LSD, or other illicit drugs on a wilderness trip, they should be told to stop and the drugs should be confiscated and destroyed. If someone is unwilling or unable to stop using these drugs, then he or she should be escorted out of the wilderness. More problematic is a person who is prescribed narcotic pain medication (e.g., oxycodone). Narcotics are central nervous system depressants that can impair concentration and coordination. In modest doses, such medications may be reasonable, but at higher doses, or if the individual is abusing prescription narcotics, then it is not safe to have him continue a wilderness journey and he must be escorted out of the wilderness. Some people may be unaware that they have a substance abuse problem when they start a wilderness trip, until they start to experience physical or psychological withdrawal. Alcohol withdrawal is considered a medical emergency because of seizures and delirium tremens.2 A careful history should establish if alcohol or other drugs may be the cause of the problematic symptoms. Withdrawal symptoms usually start with shakiness and increased heart rate and blood pressure. If withdrawal is suspected, a benzodiazepine (e.g., lorazepam) can be given. Alcohol can be used if necessary and available. Withdrawal from barbiturates or benzodiazepines can present similarly to alcohol withdrawal and can be life-threatening. Giving a benzodiazepine can diminish symptoms of alcohol, benzodiazepine, and barbiturate withdrawal. Anyone withdrawing from these substances should be taken to a hospital as soon as possible and should not be allowed to remain in the wilderness, even if enough benzodiazepine is available to diminish the withdrawal symptoms. There are too many potential complications to try to manage withdrawal in the wilderness. People who abuse cocaine, methamphetamines, or narcotics will not experience life-threatening withdrawal, but their symptoms can be extremely uncomfortable and disabling. Extreme irritability and fatigue are common, as are aches and pains typical of influenza. The withdrawal symptoms may last several days. The wilderness is no place to undergo withdrawal from cocaine, methamphetamines, or narcotics, so the person should be assisted out of the wilderness as soon as possible. On a wilderness trip someone may experiment with natural plants hoping to achieve an induced “high,” or someone may ingest, inject, smoke, or inhale a psychedelic drug. Tea made with jimson weed (sacred Datura), a common plant in the southwest United States with large, white, tubular flowers, may induce florid psychosis and delirium. Delirious persons may shed clothes, experience severe sunburn, become dehydrated, and expose themselves to all manner of risks (e.g., cliffs, whitewater). Plants that can cause psychotic symptoms and delirium (see Chapter 58) should be avoided.2 People who are experiencing drug-induced psychotic symptoms or delirium must be watched constantly until evacuation to a hospital can be arranged.

POTENTIAL


SOMATIC COMPLAINTS Some people are more sensitive to physical irritations and discomfort than are others. For most people, a headache, scrape, or sore muscle is not cause for alarm. But for some individuals, a headache is a sure sign of a brain tumor, the scrape will

Chapter 30: Mental Health in the Wilderness undoubtedly become gangrenous, and sore muscles are evidence of a smoldering systemic illness. Simple reassurance that there is no major pathologic process may be enough for many people, but others continue to worry despite solid medical evidence to the contrary. These people suffer from hypochondriasis.1 Insomnia, gastric distress, and fatigue are common complaints associated with travel and are usually not cause for concern. However, persons who tend to magnify the significance of these types of common complaints worry excessively and may voice their concerns to the entire group. Occasionally, this can have the effect of creating a kind of “mass hysteria,” where other members of the group begin to experience the same symptoms. For a person who is very worried about his or her health, repeated reassurance might be successful in ameliorating the problem. The group leader can periodically inquire about the status of the problematic symptoms. The difficulty lies in discriminating symptoms of little consequence from those that might be of greater importance. The key is to take a good history and consider a reasonable differential diagnosis leading to an organic explanation for the symptoms before concluding that the complaints are primarily of psychological origin.


RESPONSE TO CRISIS Disasters Avalanches, storms, rockfalls, climbing and whitewater accidents, and many other untoward events can lead to the death or serious injury of one or more group members. People who venture into the wilderness usually do not anticipate someone getting seriously injured or killed. Even persons who have taken wilderness first-aid courses do not enter the wilderness expecting the worst. Otherwise, no one would participate in these types of activities. There are many descriptions of outdoor trips that encountered crises.7 Humans wrap a cloak of denial around themselves. We know that bad things happen, and we may even be prepared, but no one ever expects it will happen to them or on their watch. Thus, when a crisis or tragedy occurs, it is almost always an emotional shock. When you watch your climbing partner fall and die or your buddy drown when his kayak flips in whitewater, there is a reaction of horror, dread, and disbelief. The situation is overwhelming, and people often describe a sense of unreality associated with the tragic event. A period of grief and preoccupation regarding the event is common. People who are involved in tragedies often need to replay the event in order to put it into some type of meaningful personal context. People who are relatively intact psychologically and have good social support can usually mentally process a trauma successfully without longterm mental health problems. As the size of a disaster grows and its impact on a person or a community’s support networks increases, the likelihood of long-term mental health problems grows. People who handle trauma by psychological avoidance and casting blame may have poorer outcomes.12 In response to natural disasters, some people develop acute stress disorder (ASD) or post-traumatic stress disorder (PTSD). Estimates of the frequency of these disorders after disasters (man-made or natural) vary from 2% to over 50%.12 The symptoms typical of these disorders include efforts to avoid reminders of the traumatic event and markedly increased anxiety when exposed to such reminders. The affected person may be flooded with uncontrollable memories, including bad

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dreams and flashbacks (feeling and behaving as if the trauma was happening again). The person may feel a sense of emotional detachment from others. Finally, people often have difficulty concentrating, have difficulty sleeping, feel restless, and become easily startled. The symptoms begin to interfere with daily interpersonal and occupational functioning. The symptoms can begin immediately after a disaster. If they persist for more than 2 days but less than 1 month, the disorder is called ASD. If the symptoms are present for more than 1 month, the disorder is called PTSD.1 For most people, symptoms diminish as time passes, although there is a common intensification of symptoms around the time of the 1-year anniversary of the tragedy. Symptoms may become chronic and require ongoing psychiatric care. The author has evaluated men who were held as prisoners of war and were subjected to cruel deprivation or torture during the First or Second World Wars. Some did not experience symptoms of PTSD until they retired, many years after they were traumatized (delayed PTSD).1 The immediate response to a wilderness disaster should emphasize ensuring the safety and security of the survivors. This includes provision of food, water, warmth, and shelter. People who have been involved in the disaster should be clearly informed of what has happened and what rescue efforts are underway. Communication with loved ones should be facilitated. People should be provided as calm a setting as possible to decrease arousal as much as possible. Medication use is controversial, with SSRIs showing some clear benefits during the weeks and months after the disaster. However, use of psychotropic medications in the immediate aftermath may not be necessary and may even be harmful, particularly if the sedative properties interfere with survival behavior or motivation. Individualized support should be provided as needed. The concept of critical incident debriefing is controversial, with some studies indicating worse outcomes after such interventions.12 People providing support should approach survivors with an expectation of normal recovery. Efforts to force the trauma victim to discuss the trauma should be avoided. Discussion is appropriate if the person initiates it. Connecting survivors with continuing information about the aftermath of the disaster and the means to contact other survivors can be helpful. Clinics for disaster survivors to obtain assistance in emotionally processing recent events should be provided. Such support should not focus on details of the incident unless the person initiates such discussion, because premature discussion may lead to unnecessary arousal and possibly long-term problems.

Survival Psychology It is not uncommon for people to become lost in the wilderness. Human spatial orientation abilities are limited; we often function under the illusion that we know exactly where we are.3 People rationalize disorientation in the wilderness by explaining away inconsistencies between their topographic map and the actual landmarks before them. The author experienced this phenomenon on a recent backpacking trip in the Wind River Range of Wyoming. Although the landmarks did not match the map, I rationalized the inconsistencies and believed a trail would become obvious at the top of the next pass. There was no trail. After an hour of staring at the landmarks and the topographic map, I finally determined our location. Some people are not so lucky and find themselves completely disoriented in the wilderness. As a person becomes convinced that he is completely lost, he might experience intense fear, panic, and disorientation

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unique to this type of dilemma. People with considerable experience in the wilderness may demonstrate inexplicable behaviors, such as abandoning provisioned backpacks or other potentially valuable items. Some have even removed clothing, which increased their exposure to the elements.3 After becoming lost, some persons develop a strategy and carry it through, but when it fails, they abandon hope and resign themselves to fate. Ironically, children younger than 6 years of age fare better when lost than do older children and adults. The explanation for this paradox might be that younger children act on instinct and seek shelter when cold and water when thirsty, but older children and adults panic and sometimes overlook obvious and simple means to help them survive.3 In groups that become lost, good leadership is often a key component to survival of the group. Perhaps the most famous survival story is that of Ernest Shackleton’s ill-fated voyage to reach the South Pole in 1914. His ship, the Endurance, broke up in the ice. Under his leadership, the group survived months of incredible hardship. Against all odds, all 27 men survived.5


LEADERSHIP Wilderness activities are usually not solo affairs. Outdoor adventures can range from a 5-mile day hike with a social group to an expedition involving dozens of people to climb to the summit of Mt. Everest. For adventures to be successful and safe, some level of planning and preparation is required, along with leadership or guidance. People who share wilderness activity together experience the same types of group interactions that occur among coworkers, families, and myriad other groups. A safe and rewarding wilderness adventure often begins long before the actual trip. Careful planning includes attention to numerous issues: food, equipment, maps, screening of participants, impact on environment, and permits, among others. The planning process itself may involve a group working together. Subsequent to the adventure, some type of communication may be essential to bring spiritual, emotional, or logistical closure to the experience.

The manner in which groups interact can result in a safe, challenging, and rewarding adventure or a conflicted, dangerous, and disorganized affair. Trips in the wilderness sometimes involve people who may not know one another very well, yet are thrown into close quarters and frequent close contact for an extended period. Regular close contact inevitably leads to annoyances and conflicts, but can also result in pleasurable camaraderie. Leadership is one key ingredient to a successful wilderness experience. A group in the wilderness without a leader and a plan can be a recipe for disaster. Groups without direction and guidance tend to deteriorate. They often break into factions or drift aimlessly. Morale suffers and tempers flare, as arguments and fights erupt. Such situations tend to bring out the worst in individuals. However, an effective leader can bring out the best in everyone. The type of leadership needed for a day hike differs from that needed for a difficult expedition. But even the short hike needs coordination. What if someone breaks his or her leg on the hike? Who will go for help, administer first aid, and reassure upset members of the group? Leadership skills should be taught and developed; otherwise, the leader will make the same mistakes repeatedly.4 Good leaders have a vision for the outings, but are flexible enough to adapt according to the exigencies of evolving circumstances. Successful leaders care about their people and build teams that use the strengths of each member of the group. Communication abilities are an essential ingredient in a competent leader. Sometimes, leaders emerge during crisis or disaster and are critical for survival of a group.6 Leadership and interactions among group members evolve during the course of a trip. Often, leadership is fluid, as people with different skills take leadership roles in different functional areas, such as building fires, reading maps, or maintaining good humor and morale. People can be remarkably courageous, kind, and ingenious but they can also be petty, mean, and destructive. A group on a wilderness journey is a microcosm of society, where the full range of human strengths and weaknesses can be witnessed. The leader sets the tone. The references for this chapter can be found on the accompanying DVD-ROM.

31

Wilderness Emergency Medical Services and Response Systems Franklin R. Hubbell

Today, medicine is replete with improving communications, computer-assisted diagnosis, futuristic imaging technology, faster and luxurious emergency medical vehicles, and highly skilled trainees. However, the physical world that we explore is still rugged and enduring: majestic mountains, spectacular shorelines, wild rivers, dense tropical rain forests, horizonless polar ice sheets, arid deserts, vast oceans, and hazards beyond imagination. We enter and must sometimes be rescued, treated, and saved. First response is critical. The wilderness will always have the ability to place humans in situations in which immediate help is simply not available. When in the wilderness, preexisting or created by a disaster, people must know how to survive and be able to perform emergency medicine barehanded, without all the technical wizardry that exists in a modern ambulance or emergency department. The anatomy of disaster response and its limitations are very similar to those found on a mountain or backcountry rescue: time and distance work against the rescuers, where notification of the emergency can be delayed and initial information inaccurate. The weather conditions at the site of the emergency may be poor, hostile, and rapidly changing. Terrain can make travel very difficult, slow, or even impossible. Manpower, equipment, and resources will be very limited and hard to come by. Persons responding need specialized training, skills, and knowledge of everything from self-preservation skills to emergency care skills in an extended care environment. What has changed relatively recently is the scope of practice. The principles of wilderness emergency medicine are now being applied to the expansive realm of providing care outside the “golden hour.” These same techniques, methodology, and experience learned in providing extended care in the wilderness environment apply equally to providing long-term patient care in natural and human-made disasters. Earthquakes, hurricanes, blizzards, tornados, and tsunamis not only can cause thousands of deaths, but also leave many more injured, exposed to disease, and without access to emergency, long-term, or definitive care. The principles discussed in this chapter apply equally to any extended care environment outside the golden hour, from a short 1-hour delay to extended multiday management at a disaster site. Whether an accident or medical crisis occurs in the wilderness, in the backcountry, on the high seas, or at a disaster site away from access to immediate assistance, the chain of events

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set in motion hopefully leads to a successful rescue and lives saved. However, how it unfolds varies tremendously, depending on the part of the world in which the critical events occur. Currently, no national or international standards for wilderness emergency medical service (EMS) and response exist. Instead, the configurations of personnel and policies reflect local, national, and international influences. In the United States, wilderness EMS is the most diverse because it is provided by a broad range of agencies and individuals with a wide variety of training and certification levels, ranging from first aid to paramedic. Canadian wilderness EMS is generally provided through the military, whereas in European wilderness situations, civilian physicians have a prominent role. The skills developed in providing long-term patient care in the wilderness are proving to be beneficial in medical and rescue assistance in the disaster response and relief setting. Although there is not a great effort to produce national or international standards for wilderness or disaster relief, there are national and international organizations that have their own command structures, response systems, and response criteria. It may be that organizations or structures such as the American Red Cross, Federal Emergency Management Agency (FEMA), or Department of Homeland Security will address these issues and develop standards in communications, response, and medical and rescue techniques. The art form will be to create a systemwide or nationwide set of standards that can be used when diverse entities come together during an emergency to provide relief, so that they will be able to function well together. In the world of mountain rescue, the American Alpine Club’s Safety Committee gathers, reviews, and analyzes mountaineering accidents that have occurred throughout North America and publishes the annual report, Accidents in North American Mountaineering. The data collected illustrate both the necessary diversity of wilderness and mountain rescues and the current limitations (Box 31-1). Several states have established (or are in the process of establishing) working protocols for providing care in the wilderness or “extended care” environment. With increased natural and human-made disasters, EMS systems worldwide have suddenly found themselves essentially operating in a “wilderness” setting because of prolonged exposure to a hostile environment, delayed evacuation and transport time, and lack of medical resources and direction. Prehospital personnel in extended care situations find themselves providing care for much longer than

Chapter 31: Wilderness Emergency Medical Services and Response Systems

Box 31-1. Mountain Search and Rescue Factors in the United States 1. Search and rescue is the responsibility of national parks, state parks, county sheriffs, or state conservation officers, depending on the state or park. 2. Most backcountry and technical rescues are carried out by volunteer rescue groups. 3. Ninety percent of all rescues are carry-outs on foot rather than with airlifts by helicopter or fixed-wing aircraft. 4. At least 95% of rescues are performed without physicians present, instead using the skills of first responders, emergency medical technicians, and paramedics, who may or may not be trained in wilderness medicine and rescue techniques. 5. Only two of the major climbing areas, Yosemite and Grand Teton National Parks, use helicopters extensively. 6. Only Denali National Park uses fixed-wing aircraft extensively and helicopters occasionally. 7. Only three national parks have rangers who are trained specifically for technical rescue, advanced medical support, and helicopter operations: Yosemite, Grand Teton, and Mt. Rainier National Parks. 8. National and state parks are not mandated with a “duty to rescue.” However, virtually all parks provide rescue service. Most parks have a budget for these activities. 9. Many roadside climbing areas and popular backcountry areas are not within the jurisdictions of parks. Technical and backcountry rescues carried out at these locations are often performed by local rescue squads, fire departments, and ambulance units, usually without the benefit of specialized training or technical backcountry skills.

the golden hour and discover that their street-oriented skills are often very inadequate. Internationally, the Union Internationale des Associations d’Alpinisme (UIAA) (International Mountaineering and Climbing Federation, www.uiaa.ch), headquartered in Bern, Switzerland, has established criteria and courses for postgraduate training for physicians in mountain medicine. After fulfilling these requirements, physicians in the European Union become certified in wilderness medicine and can practice the relevant skills in an appropriate arena. There is now a similar program for physicians being offered in the United States by the Wilderness Medical Society (www.wms.org). The Wilderness Medical Society has produced a curriculum on various wilderness medical topics for a total of about 100 contact hours. Upon completion and qualification, the individual becomes a Fellow of the Academy of Wilderness Medicine. In the United States, the foundation has been set for national standards in providing emergency care and rescue by adoption and implementation of the Incident Command System (ICS). This system of command and communication was developed by the U.S. Forest Service for coordinating forest firefighting tactics in the western United States, where many different agencies had to work together while fighting large-scale forest fires. The ICS

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command system has been improved and adopted by many state and local agencies and has quickly become the command system standard for all emergency response organizations, especially when it becomes necessary to orchestrate several agencies working together. The assimilation of ICS into police, fire, rescue, and EMS has offered a solution to the single biggest problem facing these services: how to coordinate and interface a variety of teams working on the same rescue effort. When each team follows its own set of operating procedures, standing orders, leadership protocols, terminology, and egos, it is often virtually impossible to effectively and safely coordinate a major rescue effort. The ICS works well, and organizations such as the National Fire Academy and various state police, fire, rescue, and EMS offices nationwide have adopted and implemented this system at all levels of emergency response. ICS is now the standard for responding to any emergency situation, ranging from a single department answering the call to a minor motor vehicle crash to a complex search and rescue effort involving many agencies and rescue teams. ICS is the foundation of emergency response because it establishes a common language and command structure that allows everyone involved to anticipate how the effort is going to proceed, what their individual and team jobs are, who is in charge, and how to communicate with each other. As the ICS becomes widely adopted and utilized, it will help establish a national standard upon which national prehospital standards, including wilderness or extended care protocols, can be built. Most states have now produced a set of working protocols for providing prehospital emergency care. However, few have attempted to write protocols for providing emergency care in the wilderness or extended care environment. At the time of this writing, Maine, New Hampshire, and Alaska have tackled some of the issues associated with providing wilderness care. New Hampshire is the only state that has written a complete set of emergency medical protocols for the wilderness, extended, or long-term patient care environment. Wilderness emergency medicine is a combination of emergency medical training and outdoor wilderness skills. Blending these elements, although essential, is not necessarily natural or easy. The art and science of prehospital emergency medicine began over 35 years ago in the United States and has evolved into a highly regimented and well-defined subspecialty of emergency medicine. Today, there are highly trained first responders, including emergency medical technicians (EMTs) and paramedics, as well as organized EMS systems. Each state has an independent EMS system and its own regulations; a truly national standard does not yet exist. The only national prehospital EMS standard that currently exists is the testing and evaluation and certification standards developed by the National Registry of EMTs. The National Registry of EMTs offers individual state EMS systems standardized written and practical examinations for first responders, EMT-Basics, EMT-Intermediates, and EMTParamedics. This guarantees that regardless of where someone was trained, he or she will be tested using the same standard. Compiling the statistics from each of the 50 U.S. states, there are about 84,000 first responders, 500,000 EMT-Basics, 140,000 EMT-Intermediates, and 140,000 EMT-Paramedics who are currently certified and licensed to practice prehospital care. Because a central agency to monitor persons trained in providing wilderness care does not exist, there is no registry of

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trained individuals. Organizations have been training people in wilderness medicine for the past 20 years. Currently, there are more than 100 different organizations, schools, and individuals offering various forms of wilderness medical training. It is not unreasonable to estimate that more than 500,000 persons have some sort of certificate training in prehospital wilderness EMS. Training programs that focus on rapid response, rapid intervention, and rapid transport to advanced care facilities exist nationwide. Prehospital personnel are prepared to work within the framework of the golden hour, when time is precious and critical actions save lives. This is a nationally accepted urban standard to which all EMS personnel are currently trained. Although this standard is appropriate for evaluating and training urban EMS personnel and response systems, it is often not adequate for rural, wilderness, mountain, or extended EMS personnel and response systems. In these situations, patient care is measured in hours and days rather than minutes. Traditional EMS recognizes rapid notification (the 911 system), dispatch, response, assessment, thorough prehospital care, transport, evaluation, and critical care in a hospital emergency department. Rapidity is the most critical factor that distinguishes urban emergency medical care from wilderness emergency medical care. However, time is not the only difference. Wilderness emergency medicine is governed by a complex set of medical skills and protocols, equipment requirements, and other specialized skills, including different attitudes or psychological requirements, each of which combine premeditated action with improvisation. A productive mental attitude comes largely from the individual’s training, expertise, and experience in the outdoors. In mountain and wilderness outdoor activities, including mountain and wilderness rescue, haste truly makes waste, which may, in certain circumstances, cost lives. As a result, wilderness and mountain rescue teams must achieve a balance between the urgency of the situation and the necessity for adequate preparation. This is not an easy or natural blend of emotions and skills. On one hand, trained EMS professionals are always primed and ready to go, feel comfortable moving rapidly, acting quickly, and thinking on their feet. On the other hand, skilled outdoors people are always eager and willing to travel into the backcountry but understand the necessity of thorough preparedness. This attitude ensures not only that each team is prepared but also that each individual is prepared. The team must be organized from a leadership perspective and know where it is headed, what injuries to anticipate, and how weather will affect the rescue. The team counts on each individual member being physically and mentally prepared. This difficult task requires recognition of the differences between short-term and long-term care during a rescue so that a safe and successful extended care rescue can be achieved. Box 31-2 outlines key skills that training needs to include.


SEQUENCE OF EVENTS IN BACKCOUNTRY RESCUE

The principles and standards of a wilderness or mountain rescue (extended care rescue), including organization, specialized skills and knowledge, and essential components of the team, can best be illustrated by reviewing the sequence of events during a typical backcountry rescue in North America (Box 31-3).

Box 31-2. Rescue Personnel and Training in the United States 1. Most technical rescue personnel in the United States are climbers or skiers who have added wilderness rescue techniques and medical training to their skills. 2. Currently there are about 800,000 certified and licensed EMT-Basics, EMT-Intermediates, and EMT-Paramedics in the United States. 3. A growing number of wilderness EMTs are trained in the skills of extended victim care in the backcountry environment. There are a growing number of courses available for training. 4. Key skill elements of medical training for wilderness medical and rescue training include the following: a. Thorough victim assessment skills and monitoring b. Technical skills and the authority to perform the following: (1) Airway management, to include endotracheal intubation, LMA, Combitube, and other advanced airway skills (2) Shock management to include intravenous therapy (3) Use of the pneumatic antishock garment (MAST and PASG; no longer recommended for general treatment of shock, so use in special circumstances only) (4) Oxygen administration and its limitations (5) Use of appropriate medications: (a) Epinephrine for anaphylactic reactions (b) Antibiotics for major open or penetrating wounds, protruding intestines, compound fractures (c) Acetazolamide, steroids, nifedipine, and furosemide for acute high-altitude problems (d) Pain medications for musculoskeletal trauma (e) Albuterol for bronchodilation (f) Aspirin and nitroglycerin for chest pain (6) Field rewarming techniques (7) Field reduction of angulated fractures and dislocations c. Victim packaging and transportation skills 5. Key skill elements of technical training for rescue personnel in the United States include the following: a. Appropriate climbing skills for terrain (rock, ice, snow, glacier) b. Radio communication skills and protocols c. Helicopter and fixed-wing protocols d. Training and expertise in using the Incident Command System in field protocols

Occurrence of the Critical Event The critical event occurs when an individual participating in an activity away from immediate help is suddenly stricken by injury or illness. The key factor is immobilization. The fact that the injured or ill person cannot self-evacuate or move to seek shelter or stay warm results in the need for a rescue. Once the victim or others in the party realize this, the need to seek help becomes obvious.

Chapter 31: Wilderness Emergency Medical Services and Response Systems

Box 31-3. Sequence of Events in Backcountry Rescue 1. The critical event occurs: an injury or illness that requires assistance and evacuation. 2. A decision is made to “get help,” and someone goes for help. 3. The emergency medical system is notified of the emergency. 4. The emergency medical system is activated, or “dispatched.” 5. Eventually, the “extended rescue team” is notified and mobilized. 6. The rescue team assembles and organizes, then leaves the trailhead (may be preceded by a “hasty team”). 7. The team locates the victim. 8. The team provides appropriate “extended emergency care.” 9. The team organizes and evacuates the victim to the appropriate facility. 10. The team returns to base, is debriefed, and prepares for the next rescue.

Making the Decision to Get Help Before anyone leaves to seek assistance, the victim’s companions should perform a physical examination, record vital signs, determine the level of consciousness, and provide appropriate emergency care, which may entail moving the victim into protective shelter. Victim information should be summarized in a note that accompanies the individuals going for help. A map depicting the victim’s exact location and a list of the other party members, noting their level of preparedness to endure the environmental conditions, should be included. The individuals going for help should carry appropriate provisions. To prepare information adequately generally takes 30 minutes to 1 hour. However, thorough preparation rarely occurs. Often, someone suddenly yells, “I’ll get help” and disappears, running down the trail with sparse vital knowledge. With the improvements and availability of communications technology, such as cellular phones and global positioning systems, backcountry adventurers may have more rapid access to the EMS system from the mountains. Whether this will increase the number of inappropriate callouts remains to be determined. Recent reports indicate that reliance on fallible technology may be responsible for outdoors people using poor judgment in terms of trip planning. Assuming that help is just a phone call away, hikers are taking more risks.

Notifying the Emergency Medical System Eventually, the messenger notifies someone in authority that an emergency has occurred and help is needed. Usually, the request is made to a central 911 system. If no central service is available, a local dispatch agency is notified. The agency contacts the closest emergency medical service, which can be a rescue squad, ambulance corps, fire department, or first response team.

Activating the Emergency Medical System Notification of an emergency usually occurs by means of pagers worn by individual members. An alert tone is followed by an

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oral message describing the emergency, its location, and type of response required. At this point, a wide variety of events can occur, involving agencies within and outside the EMS system. Even in areas of the United States with well-organized extended care rescue teams, the team may be notified last. Ideally, it should be notified immediately, but all too often this is not the case. Instead, local agency responders are notified and rush around trying to determine how quickly they can reach the victim.

Notifying and Mobilizing the Extended Rescue Team The first step is to notify team members. In many parts of the United States, organized and coordinated extended rescue teams do not exist, so a “team” is created of relatively untrained volunteers willing to hike in and assist. The task of further organizing and coordinating the rescue effort generally falls on the shoulders of a local rescue squad, fire service, or police department, which may or may not be willing and prepared to manage and execute an extended or technical rescue. In the parts of the United States where backcountry use is common and backcountry accidents occur regularly, extended care rescue teams have generally evolved from local EMS squads with skilled outdoor enthusiasts. Some teams offering local search and rescue capabilities may be coordinated locally (such as the Appalachian Mountain Club [AMC], Stonehearth Open Learning Opportunities [SOLO], and Mountain Rescue Service in the White Mountains of New Hampshire); other teams may be part of a nationwide system responding to incidents throughout the country and be coordinated on a regional or national level (such as the National Cave Rescue Commission), or the future may involve FEMA, or even the Department of Homeland Security. Coordination of extended care rescue teams may also come under the jurisdiction of a law enforcement body, such as state conservation officers (e.g., New Hampshire Fish and Game), sheriff’s department (e.g., the Los Angeles County Sheriff in California), or a statewide coordinating system (e.g., the Pennsylvania Search and Rescue Council). Organized teams can be quite sophisticated in their dispatching function so that all members can be notified simultaneously, or they may use a more “low-tech” telephone tree to call out members.

Assembling and Organizing the Rescue Team Once members are notified, they assemble at a common location (rescue station) to organize the rescue effort. The first task is to define the type of rescue to establish equipment needs. Estimating the time it will take to effect the rescue and assessing the need for other agency involvement and assistance are also primary tasks. The questions to be answered and the variables to be considered may include the following: 1. Time of day: will this be a night rescue? 2. Weather: what are the current weather conditions at the rescue location and what is the forecast? 3. When did the accident occur? 4. What are the supposed injuries? 5. How many victims are there? 6. How many people are in the party? 7. How well prepared are they? 8. Does anyone in the party have medical expertise? 9. Do we know the exact location, or is this a search and rescue?

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10. Is a “hasty team” needed? Has it left for the scene yet? 11. Is each of the team members prepared? Does each have personal equipment, a bivouac kit, head lamp, food, and water? 12. Is each member trained and skilled in this particular type of rescue? 13. Who is on the medical team? 14. Who is on the evacuation team? 15. Is the team equipment organized and divided up? 16. How urgent is the situation? Is a helicopter required? Is one available? 17. Are the weather conditions appropriate for an air rescue? 18. Will multiple agencies be involved? If so, are radio frequencies coordinated? Once the team is assembled and all pertinent issues have been addressed satisfactorily, the team is transported to the trailhead (launch point) to begin the search. Commonly, a hasty team starts out ahead of the main team. Once the hasty team has enough information to locate the victim, team members travel as lightly as possible, with only enough gear to ensure their own safety and equip them to manage the victim’s primary injuries. The goal is to reach the victim as quickly as is reasonably possible and to deliver primary care, then apprise the rest of the team of the victim’s condition, equipment needs, and environmental concerns.

Locating the Victim How long it takes to locate the victim varies tremendously, depending on distance, terrain, weather conditions, mode of transportation, and whether the victim’s exact location is known. A general rule of thumb for a team responding on foot is that it will take 1 hour for each 1 mile through the backcountry. If a search is involved, all bets are off. A search and rescue effort can involve many agencies, individuals, and days (see Chapter 32).

Providing Appropriate Extended Emergency Care Once the victim is located, appropriate medical care can be provided. The rescue team should ensure its own safety; wet clothes should be replaced with warm, dry clothing, and members should check for emerging problems within their group. While the medical team cares for the victim, the evacuation team secures shelter, prepares warm drinks, establishes and maintains communications, and plans and organizes the evacuation. Companions with the victim may have been affected by the environment while waiting for the rescue team to arrive and require assistance. They may need to be assessed and treated for hypothermia, frostbite, heatstroke, heat exhaustion, or dehydration. Regardless of what transpired before the medical team arrived, a complete victim assessment is essential. Do not assume that all the injuries have been found or that all medical conditions have been managed properly (Box 31-4). In the extended care environment, the victim must be monitored for changing conditions that indicate an underlying problem. Awareness of environmental emergencies is particularly important, with constant care to prevent hypothermia, frostbite, heatstroke, heat exhaustion, and dehydration. To do this, it is necessary to monitor the victim and write a new SOAP note or “reSOAP” the patient every 15 minutes:

Box 31-4. Victim Assessment PRIMARY SURVEY: LOCATING AND TREATING LIFE-THREATENING PROBLEMS A—Airway Management

Is the airway open? Is the airway going to stay open? B—Breathing

Is Is Is Is Is

air moving in and out? the airway quiet or silent? breathing effortless? the respiratory system intact? breathing adequate to support life?

C—Circulation

Is Is Is Is

there a pulse? bleeding well controlled? capillary refill normal (less than 2 seconds)? circulation adequate to support life?

D—Disability

Conscious vs. unconscious Level of consciousness—awake, verbal, painful, unconscious (AVPU) or Glasgow Coma Scale Cervical spine stabilization E—Environment

Internal vs. external? Is the victim warm and dry? Protected from the cold ground? Protected from the elements? SECONDARY SURVEY: WHAT IS WRONG AND HOW SERIOUS IS IT?

Vital signs: Indicate the condition of the victim Respiratory rate (RR) and effort Pulse rate (PR) and character Blood pressure (BP): systolic/diastolic Level of consciousness (LOC): AVPU or Glasgow Coma Scale Tissue perfusion (TP): skin color, temperature, and moisture Capillary refill (less than 2 sec) Victim examination: Head-to-toe examination to locate injuries AMPLE history: Allergies Medicines Past medical history Last in and out: food/drink & voiding Events leading up SOAP Note: To record and organize victim data Subjective: age, gender, mechanism of injury, chief complaint Objective: vital signs, victim examination, AMPLE history Assessment: problem list Plan: plan for each problem

Chapter 31: Wilderness Emergency Medical Services and Response Systems “ReSOAPing” the patient: Subjective: Is the victim comfortable, too hot, too cold, hungry, thirsty, or in need of urination or defecation? Objective: Vital signs—are they stable? Record these. Victim examination—recheck all dressings, bandages, and splints; are they still controlling bleeding? Are they too tight or too loose? (Swelling limbs can cause bandages or splints to impede circulation, resulting in ischemic injuries or worsening frostbite or snakebite.) Assessment: Has the initial assessment changed? Plan: Is the rate of evacuation still the same?

Evacuating the Victim to the Appropriate Facility While providing emergency care, part of the team is designated as the evacuation team. This group has evaluated the various options for evacuation. To properly evaluate the situation, the first information they need is provided by the medical team leader, who needs to know the status of the victim to establish the pace. If the victim’s condition is stable, time is less important; if the victim’s condition is critical, time is critical. The evacuation team must explore different options. If speed is a consideration, weather conditions are reviewed, and the availability of a helicopter-assisted rescue is determined. If a helicopter is not an option, the fastest route out is established. If time or speed is not critical, the safest means of evacuation that is easiest on the victim and rescuers is defined. A general rule for the duration of an evacuation is that it will take 1 to 2 hours for every 1 mile to be covered, requiring six well-rested litter bearers for every 1 mile. Thus, a 4-mile carryout will require a 24-member litter team and can take 4 to 8 hours to complete. Eventually, the team reaches a trailhead, and the victim is transferred to an ambulance for transport to a hospital emergency facility.

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Box 31-5. The Ten Essentials 1. Attitude Positive belief that you can make things better; the will to survive 2. Fuel to burn: food High-carbohydrate foods that require no preparation High-carbohydrate foods that can be made into a drink 3. Quench your thirst: water A minimum of 2 L/day to survive, 4 L/day to thrive Up to 3 L/hr if active Ability to make more disinfected water 4. Stay warm and dry: clothing Warm clothing that retains heat even if wet Waterproof raingear, top and bottom 5. Get dry: shelter Ability to improvise shelter or bivouac A bivouac (“bivy”) kit (see Box 31-6) 6. Get warm: fire Ability to warm water (stove, candle, fire) Ability to build a fire (waterproof matches and tinder) Ability to make kindling or tinder (folding knife) 7. Know where you are going: navigation Map and compass skills and route-finding skills Ability to move about at night (headlamp) 8. Know the environment: weather Basic understanding of weather patterns Knowledge of how to react in severe weather; lightning 9. Getting help: signaling Whistle, preferably plastic 10. Providing help: first aid kit Basic small personal trauma kit

Returning to Base The team returns to base to reorganize equipment in preparation for the next extended rescue, and to debrief. Because people are exhausted and hungry, the debriefing session is often canceled. However, establishing a mechanism to debrief the rescue effort is imperative so that team members can learn from the shared experience, discuss victim care, and work through problems. Whenever several different emergency organizations with disparate rescue and emergency personnel combine to perform a complex rescue, there may be tension, conflicting egos, and concerns about the medical care provided or evacuation plan used. These problems deserve to be discussed and managed in real time as expediently as possible so that teams will cooperate successfully in the future, improve their performance, and provide the best possible patient care on the next rescue. This process minimizes the burnout syndrome that can occur with volunteer teams.


TEAM ORGANIZATION AND FUNCTION

The organization of an extended care rescue team is based both on training of individuals and on type of rescue. The structures of teams can vary from loosely knit groups of friends with no leadership hierarchy to paramilitary organizations with rigid leadership roles.

Team members require personal knowledge, experience, and expertise in the particular aspect of extended care and rescue in which they will participate, as well as knowledge and expertise in the principles of extended emergency care, extended rescue techniques, and technical rescue skills.

Personal Knowledge, Experience, and Expertise Individuals who want to be part of an extended rescue team need to acquire outdoor skills before they become part of a rescue team. Every member must have extensive knowledge of likely environmental emergencies: hypothermia, frostbite, heat syndromes, snakebite, dehydration, lightning strike, and so forth. Each must understand general principles of weather behavior. Rescuers need to be comfortable with route finding, map and compass, personal preparedness, and bivouac and survival skills. The knowledge, skills, and equipment that a skilled outdoors person should possess are often referred to as “the ten essentials” (Boxes 31-5 and 31-6). The same skills, knowledge, and equipment commonly used by the outdoor enthusiast are essential on a mountain rescue.

Extended Rescue Techniques and Skills Specific skills and techniques applicable to a particular situation include those of search and rescue, vertical and technical rock

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Box 31-6. Bivouac Kit Two large garbage bags (emergency shelter or raingear) 10- × 10-foot sheet of plastic and 100 feet of parachute cord (shelter) Emergency space blanket (shelter, ground cloth) Stocking cap (warmth) Spare socks (warmth; can act as spare mittens) Metal cup (to warm liquids) Gelatin (to make a drink) Two plumber’s candles (to warm water or start fire) Waterproof matches or lighter Knife Compass Whistle All these items fit neatly into a small stuff sack that is 6 × 6 inches (15.2 × 15.2 cm) and weighs less than 1 pound (2.2 kg) when filled.

climbing, and white-water navigation. Snow or winter camping or avalanche rescue may be required, depending on the environment. Extended rescue teams should require their members to have, at a minimum, the working knowledge and equipment in Box 31-7. Knowledge is acquired over time. Specific medical, rescue, and technical skills are obtained and retained through courses, continuous training, and refresher programs. The Appendix at the conclusion of this chapter provides a list of schools, institutes, and organizations that are involved in wilderness medicine and mountaineering research, standards development, and training programs.

Wilderness and Mountain Rescue Team Organization Organization of wilderness and mountain rescue teams is where the greatest diversity exists because no universal standard has been established. Teams vary from local mountain rescue teams with extreme skills and qualifications for providing mountain rescue care to informal collections of friends without leadership. Other, more “professional,” teams are operated under the jurisdiction of law enforcement agencies with paramilitary hierarchy and leadership. This diversity is particularly noticeable in the United States because most teams are composed of volunteers who are not reimbursed for their rescue efforts. In Europe, mountain rescue teams are professional and employ full-time personnel. They charge for rescue efforts, with the fees providing money for personnel, equipment, helicopters, technical gear, and ongoing training. As with any “profession,” standards have evolved. As a result, there are more standards in Europe than in the United States. Still, there is variation across Europe from country to country, especially in leadership and organization. In many parts of the world, especially remote and wild areas, organized and available rescue teams do not exist. If someone is in need of help, the expedition team necessarily becomes the rescue team.


TRAINING OF WILDERNESS EMERGENCY MEDICAL TECHNICIANS

The best way to develop an appreciation for the vast difference between what is required of the traditional (urban) EMT and what is required of the extended care or wilderness emergency medical technician (WEMT) is to compare their respective course curriculums. The Department of Transportation (DOT) is responsible for developing and updating the EMT-Basic, EMT-Intermediate, and EMT-Paramedic curricula in the United States. These curricula are considered the minimum national standard for EMT students to qualify for the National Registry or an individual state practical and written examination. Passage of such an examination enables a student to become certified as a National Registry or state EMT-Basic, EMT-Intermediate, or EMT-Paramedic. A national standard for WEMT curricula does not exist. Despite the lack of a DOT-like standard, there are several similar curricula for wilderness emergency care at the EMT level. Based on the recommendations of the Wilderness Medical Society and other groups that address the issues of wilderness prehospital emergency medicine, these curricula adhere to the same principles of long-term patient care, which can be used for comparison with the standard DOT curriculum. A WEMT course typically contains all of the material in the DOT EMT course curriculum plus what is necessary to acquire the skills attendant to long-term wilderness emergency care. Typical EMT courses are about 100 hours, with 10 additional hours of emergency department observation time. The WEMT module carries an additional 48 to 80 hours of training. There are EMT Wilderness Modules available that are postgraduate courses designed to train EMTs in long-term patient care. A typical WEMT course outline appears in Box 31-8. The topics in boldface are unique to WEMT programs; the other topics are those required in a DOT EMT course. Hours per topic illustrate the time required for both EMT and WEMT training. This outline is arranged in the current DOT EMT recommended format, with the WEMT material added on a per topic basis; topics are not necessarily listed in the order that they would be taught for a particular course. An explanation follows of the extended emergency medical care material that must be learned by WEMTs.

Introduction to Emergency Care “Wilderness versus urban emergency care” is an introductory presentation to illustrate the differences between urban (golden hour) emergency care and extended, or wilderness, emergency care. For WEMTs, it will be necessary in certain instances to learn two different modalities of therapy, one for short-term (less than 1 hour) care and one for long-term or extended (several hours to days) care. “Backcountry rescue gear inspection” is a hands-on review of gear for the outdoor practice sessions and backcountry mock rescues. The course staff must inspect the participants’ boots, clothing, raingear, and rescue equipment to determine their adequacy for the particular environment in which they will be deployed. Inspecting equipment not only ensures the safety of each individual in the course but also teaches a standard for

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Box 31-7. Knowledge, Skills, and Equipment for Extended Rescue Teams MOUNTAINEERING SKILLS

Understanding fabrics and clothing systems and their seasonal variations (see Chapter 70) Fabrics and fibers Layering techniques Vapor barrier systems Waterproof fabrics, raingear systems Footgear Personal protection equipment: Helmets Harnesses Gloves Goggles, sunglasses Hearing protection Backcountry equipment Internal or external frame packs and soft packs Shelter (natural and human-made) Specialty equipment: snow shoes, crampons, ice axes, stoves, skis Backcountry travel Route finding Map and compass: map reading, dead reckoning, types of maps; compass reading, bearings, magnetic vs. true bearing, triangulation, global positioning systems Survival skills: the ten essentials Shelter and warmth; emergency bivouac (“bivy”) kits Food, water Understanding how backcountry travel and rescue vary with the seasons Understanding how backcountry travel and rescue vary with different environments: Alpine Desert Forest Water (swamp, river, lake, ocean) Tropics High altitude Low-impact camping and rescue work Basics of weather and weather forecasting Principles of barometric pressure Clouds and their significance in weather forecasting Prevailing weather patterns in the rescue area Personal fitness Physical conditioning Nutrition and hydration requirements for different activities MOUNTAIN AND EXTENDED EMERGENCY MEDICAL SKILLS

Emergency medical training should be at a minimal level of first responder or higher (emergency medical technician, paramedic, registered nurse, nurse practitioner, physician’s assistant, or physician). Regardless of the level, training must include specific information on wilderness and extended emergency care procedures.

TOPICS OF EXTENDED CARE TRAINING AND PRINCIPLES SHOULD INCLUDE THE FOLLOWING:

Patient assessment system Cardiopulmonary resuscitation Airway management, including endotracheal intubation and needle decompression for tension pneumothorax Shock and control of bleeding, including the use of intravenous (IV) therapy for fluid resuscitation Long-term wound care and prevention of infection Musculoskeletal injury management, including specific information on diagnosis and long-term management of the following: Sprains and strains Fractures, including how to reduce or realign angulated fractures Diagnosis and reduction of dislocations Management of compound fractures Management of chest injuries, including decompression of a tension pneumothorax with a needle thoracostomy Spinal cord injury diagnosis and management Head injury, including recognition and management of increasing intracranial pressure Management of environmental emergencies Hypothermia and frostbite, including the use of IV fluids Heatstroke and heat exhaustion, including the use of IV fluids Dehydration and nutrition, acute and during evacuation Lightning injuries Animal attacks, insect bites, and reptile and marine envenomations, including anaphylactic reactions and the use of epinephrine and antihistamines Contact dermatitis, such as poison ivy, oak, and sumac Sunburn and snowblindness High-attitude injuries, including acute mountain sickness, pulmonary edema, cerebral edema Near drowning Diagnosis and management of acute medical emergencies: Chest pain (myocardial infarction, angina, costochondritis) Shortness of breath (asthma, anaphylaxis, pneumothorax) Seizures and cerebrovascular accidents Acute abdomen (peritonitis, constipation, diarrhea) Pyelonephritis Septic shock Victim lifting and handling techniques Improvising techniques: “emergency medicine barehanded” (see Chapter 19) Training in the use of the Incident Command System Blood-borne pathogens and infectious disease prevention Monitoring of bodily functions (hunger, thirst, and bodily waste management) General understanding and appreciation for the difference between urban (short-term) and wilderness (long-term) emergency care Continued

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Box 31-7. Knowledge, Skills, and Equipment for Extended Rescue Teams—cont’d MOUNTAIN AND EXTENDED RESCUE SKILLS

Understanding equipment used in wilderness search and rescue operations, including maintenance and care Ropes, slings, carabiners, harnesses, helmets Litters, litter harnesses, haul systems Litter patient packaging equipment Basic radio communications Care and maintenance of communications equipment Procedures and protocols Basic helicopter operations and procedures Approach to a helicopter Safety considerations Landing zones Haul techniques Interagency relations Basic understanding of search procedures Basic understanding of rescue procedures Basic understanding of Incident Command System and its use in search and rescue management Basic rope-handling and knot-tying skills How to care for and handle ropes

preparedness, awareness, and attention to detail that is critical for wilderness travel and emergency care. “Medical-legal issues” is usually offered early in a course so that the participants are aware of the legal concerns surrounding practicing medicine as EMTs and WEMTs. WEMTs need to be aware of protocols that exist where they will become licensed. “The human animal—our natural physiologic limits” course is an overview of how humans fit into the natural environment, including their daily nutritional and fluid requirements and natural limitations in different settings. The WEMT must understand physiologic limits, such as those of endurance, temperature, and altitude, and the consequences when these limits are exceeded.

Patient Assessment Systems “Patient assessment in the wilderness and practice” takes the newly learned skills of patient assessment and adapts them to the backcountry. The WEMT must be knowledgeable and skillful in wilderness patient assessment, a step-by-step approach to the first 5 minutes of scene safety and patient care. The WEMT will develop an awareness of potential life-threatening dangers in the environment, how to ensure personal safety and the safety of others, how to approach a victim safely, how to perform primary and secondary surveys to determine the extent and severity of injuries, and what impact the environment might have on the victim.

Airways, Oxygen, and Mechanical Aids to Breathing “Airways, oxygen, cardiopulmonary resuscitation, and mechanical aids to breathing in the wilderness environment—uses and limitations” addresses one of the most important lifesaving and life-maintaining skills in emergency medicine: the ability to establish and maintain a patent airway. Unfortunately, most

Rappelling, belaying, and braking techniques Knots Figure-8 Figure-8 follow-through Figure-8 on a bight Double figure-8 Double fisherman’s Prusik Tensionless hitch (round turn and two half hitches) Water knot Half hitch and full hitch Bowline Alpine butterfly Specific rescue training Water search White-water Avalanche Technical or vertical (rock) Cave LEADERSHIP

Leadership and “followship” training Ability to use the Incident Command System

EMTs are not provided with the training and tools they need to properly maintain an open airway in an unconscious victim. Failure to be able to maintain an open airway by the recovery position, endotracheal intubation, use of laryngeal mask airway (LMA), or Combitube can be disastrous. Endotracheal intubation is commonly used by EMTIntermediates and EMT-Paramedics and other advanced life support (ALS) personnel in cardiac arrest settings and for unconscious, unresponsive victims. In the extended care environment, the use of intubation by endotracheal tube, LMA, or Combitube in a cardiac arrest situation is not nearly as common as it is for the normothermic, unconscious, and unresponsive person, who has probably suffered head trauma. In this situation, without the ability to perform intubation, the only way to maintain a patent airway while lifting, moving, and transporting a victim in a litter is to place the victim on his or her side in the recovery position. In the recovery position, gravity pulls the tongue forward and allows secretions to drain from the mouth. Oropharyngeal, nasopharyngeal, and tongue-pinning techniques may temporarily keep the tongue from occluding the airway, but they are ineffective in preventing vomitus, blood, or saliva from entering the airway. Also, during evacuation in a litter, constant monitoring of a victim’s airway is virtually impossible, which makes proper airway management and monitoring of paramount importance. The WEMT should know how to establish and maintain a patent airway, including the use of positioning and advanced airways. “Oxygen administration” presents the use of supplemental oxygen, for which both EMTs and WEMTs follow the same general guidelines. Even though oxygen is important to prehospital care, its use has significant logistic limitations in the backcountry. The WEMT must realize that carrying large quantities of oxygen into the backcountry is impossible. Small D and E cylinders can be carried, but each provides high-flow oxygen

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Box 31-8. EMT and WEMT Course Curricula and Hours per Topic* 1. Introduction to emergency care Wilderness vs. urban emergency care (1 hour) Backcountry rescue gear inspection (1 hour) Medical-legal issues (1 hour) Blood-borne pathogens Overview of human systems—anatomy and physiology (2 hours) The human animal—our natural physiologic limits (2 hours) 2. Patient assessment systems Primary survey—ABCs (1 hour) Secondary survey (1 hour) Patient assessment practice (2 hours) Patient assessment in the wilderness and practice (3 hours) 3. Cardiopulmonary resuscitation (8 hours) Mannequin practice and certification (8 hours) Cardiopulmonary resuscitation (CPR) teaching, practice, and testing to American Heart Association standards 4. Airways, oxygen, and mechanical aids to breathing (3 hours) Airways, oxygen, CPR, and mechanical aids to breathing in the wilderness environment—uses and limitations (6 hours) Airways: oropharyngeal, nasopharyngeal, endotracheal intubation, LMA Oxygen administration Suction techniques 5. Bleeding and shock (3 hours) Shock, intravenous (IV) fluids, and long-term patient care (4 hours) Practice starting IV infusions and fluid administration (4 hours) Use of pneumatic antishock garment (PASG) (3 hours) Use of PASG in the wilderness (1 hour) 6. Soft tissue injuries (3 hours) Long-term wound care (1 hour) 7. Principles of musculoskeletal care Fractures of the upper extremities (3 hours) Fractures of the pelvis, hip, and lower extremities (3 hours) Fracture laboratory—practice in assessment and management (3 hours) Musculoskeletal trauma management in the wilderness (3 hours)

8. Injuries of the head, face, eye, neck, and spine (3 hours) Practical laboratory: spinal cord injury management (SCIM) (3 hours) Head trauma, increasing intracranial pressure (1 hour) SCIM: Long-term care and improvising (l hour) 9. Injuries to the chest, abdomen, and genitalia (3 hours) Chest trauma in the wilderness (3 hours) 10. Medical emergencies I (3 hours) Poisoning, bites and stings, heart attack, stroke, dyspnea Medical emergencies II (3 hours) Diabetes, acute abdomen, communicable disease, seizure, substance abuse, and pediatric emergencies Medical emergencies in the wilderness (3 hours) 11. Emergency childbirth (3 hours) 12. Burns and hazardous materials (3 hours) Long-term care of burns (1 hour) 13. Environmental emergencies (3 hours) Hypothermia, frostbite, immersion foot (4 hours) Heatstroke, heat exhaustion, dehydration (4 hours) Drowning (2 hours) High-altitude emergencies (2 hours) Barotrauma (2 hours) Animals that bite and sting (2 hours) Plants—contact dermatitis (2 hours) Marine animals that bite and sting (2 hours) 14. Psychological aspects of emergency care (3 hours) 15. Lifting and moving patients (3 hours) Use of Stokes litters and improvising litters (3 hours) Principles of backcountry evacuation (4 hours) Search and rescue organization and execution (4 hours) Wilderness mock rescue with or without overnight (8 to 12 hours) 16. Principles of vehicle extrication (4 hours) Practice laboratory (3–8 hours) 17. Leadership and “followship” skills The Incident Command System 18. Ambulance operations I (3 hours) Ambulance operations II (3 hours) Helicopter-assisted rescues (3 hours) 19. Review (3–6 hours) Testing—written and practical examinations (16-20 hours) 20. Emergency department observation time (10 hours)

*Topics in boldface are peculiar to WEMT programs, whereas the other topics are required topics covered in a DOT EMT course.

for only 20 to 30 minutes. Oxygen is a compressed gas in a tank, so as it expands, cools dramatically, and may contribute to hypothermia. To prevent this, the gas should be preheated by wrapping the oxygen tubing around a chemical heat pack during administration. “Suction techniques” presents the use of suction devices to clear the airway, which is similar for EMTs and WEMTs. Handoperated, as distinct from battery-operated, suction devices are usually used in extended care scenarios.

Bleeding and Shock “Shock, intravenous (IV) fluids, and long-term patient care” and “Practice starting IV infusions and fluid administration” provide information about the care of victims in shock or suffering from environmental emergencies that cause volume depletion, such as heatstroke or hypothermia. For urban management of shock, the essential component is recognition. Once shock is recognized, the victim can be rapidly transported to an emergency department or intercepted by

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paramedics for definitive care, namely, fluid resuscitation. In the extended care environment, WEMTs must be able to manage the volume-contracted patient by providing appropriate definitive care and fluid resuscitation. During extended evacuations, WEMTs should know how to administer IV fluids to stabilize hypovolemia. This includes starting a peripheral IV line, maintaining catheter placement, using proper fluids, and prewarming and maintaining warm solutions before and during administration. “Use of pneumatic antishock garments (PASG) in the wilderness” discusses the use of these garments for victims of a pelvic fracture. The practice of treating shock using PASG is no longer recommended. As long as an IV line can be established and maintained, fluid administration is the definitive method for managing shock. The WEMT must be aware that the PASG has other uses. In the extended care situation, the PASG may be invaluable as a splint to stabilize a fractured pelvis, and thus contribute to control of internal bleeding. It may also be used as an improvised air splint for a fractured femur. An added benefit is that the PASG may facilitate a more comfortable and well-padded ride for the victim in the litter during evacuation. However, WEMTs must recognize the limitations of a PASG. The primary drawback in the backcountry is the potential for cold injury. Once the apparatus is inflated, the decrease in peripheral circulation greatly increases the risk for cold injuries or frostbite to the lower extremities. This can be prevented by properly packing the feet with chemical heat packs and adequately insulating the lower extremities in the litter. Careful monitoring of the lower extremities every 15 minutes is essential.

Soft Tissue Injuries “Long-term wound care” covers proper wound management once bleeding has been controlled, and further care if more than 12 hours will be required to bring the victim to definitive care. The principles of long-term wound care are to stabilize the wound and prevent and control infection. To prevent infection, the WEMT must know how to sterilize or disinfect fluid and how to properly débride and rinse out a contaminated wound. Once the wound is cleaned and débrided, the edges can be approximated but not tightly closed because this may increase the risk of abscess formation and a lifethreatening infection. Training in suturing techniques to close wounds is not currently recommended because suturing is usually for cosmetic reasons and can almost always be done later, lessening the risk for infection by tightly closing the wound. Even the most fastidiously cleaned wound can still become infected, particularly in a remote setting, because of constant exposure to microbes. Recognition of wound infections and appropriate management are important. The WEMT must learn to use specific antibiotics in extended care settings of greater than 3 days and for prophylaxis with grossly contaminated wounds and compound fractures. Antibiotic therapy is not controversial because various safe broad-spectrum antibiotics can cover most wound infections with minimal risk for a severe allergic reaction. In certain circumstances, the benefits of antibiotic administration clearly outweigh the risks.

Principles of Musculoskeletal Care “Musculoskeletal trauma management in the wilderness” presents the treatment of injuries. In an urban setting, the primary

concern with fracture and dislocation care is that the injury site be splinted properly to prevent further injury. In the extended care environment, the primary concern is to maintain proper circulation distal to the site of the injury. This may require straightening an angulated fracture or reducing a dislocation. When an angulated fracture occurs, distal circulation can be impaired, putting the soft tissues at considerable risk for ischemic injury or frostbite. Under normal circumstances, it would take hours for moderate ischemia to cause irreparable soft tissue injury, but in the backcountry, prolonged time under hostile weather conditions frequently occurs, which decreases the amount of heat and oxygen being transferred to the extremity. Knowing how to properly straighten out an angulated fracture significantly decreases the risk for secondary ischemic injury and frostbite, controls bleeding at the fracture site, and diminishes pain. It is much easier to splint and stabilize a fracture in proper position if it is in anatomic position than if it is angulated. About 3 additional hours of training are needed to teach a WEMT how to straighten an angulated fracture and reduce dislocations. Without an x-ray, it is impossible to see the exact positioning of bone fragments or disarticulated joints, making it difficult to know exactly how to manipulate the bone. The concern is that if a jagged bone end is moved improperly, secondary injury might occur because part of a neurovascular bundle might be severed, a fascial sheath surrounding a muscle might be cut, or the bone ends might erupt through the skin. Fortunately, all these structures are richly endowed with pain receptors. If the sharp end of a bone fragment begins to impinge, it causes a dramatic increase in pain at the site. A commonly used technique is to straighten the angulated site slowly while maintaining constant gentle traction. With each 1 to 2 cm of movement, the victim is asked if the new position is better or worse (causes less or more pain). If the pain diminishes with movement, the reduction is proceeding properly; if pain increases, all movement is stopped, and the extremity is returned to the previous position of improvement. While still under gentle traction, the extremity is repositioned, and another attempt at reduction is made. As long as nothing is forced and movement is achieved slowly under gentle traction, angulated fractures can be easily realigned and dislocations reduced without the need for pain medication or any risk for further injury. Musculoskeletal injuries in the long-term care setting must be carefully monitored. It is essential to re-inspect the injury site at reasonable intervals for circulation, sensation, and motion. Fracture sites swell; as a result, even the best splint can act as an inadvertent tourniquet. Immobilized extremities cool because of lack of activity and impaired circulation, also increasing the risk for ischemic injury or frostbite.

Injuries of the Head, Face, Eye, Neck, and Spine “Head trauma, increasing intracranial pressure” addresses one of the leading causes of death from backcountry accidents. Many who die of head trauma in the wilderness would have survived in an urban setting because of rapid access to definitive care. The WEMT must be able to recognize a potentially serious head injury long before the victim is at risk for brainstem herniation. In the extended care environment, there are few situations when the team should hurry. One such situation is the presence

Chapter 31: Wilderness Emergency Medical Services and Response Systems of significant head trauma, for which the only appropriate care may be rapid evacuation to a facility where the victim can be treated by a neurosurgeon. It is important to establish and monitor the level of consciousness. The AVPU (awake, verbal, pain, unresponsive) scale is used. Within the primary survey, an initial evaluation of disability or neurologic status is made. After that, level of consciousness is reevaluated every 15 minutes to observe in particular for any evidence of increasing intracranial pressure.

Injuries to the Chest, Abdomen, and Genitalia Chest trauma can result in a pneumothorax that can evolve into a tension pneumothorax. WEMTs need to be taught how to inspect, palpate, percuss, and auscultate the chest to identify significant injuries. It is not difficult to train an individual to detect breath sounds, determine the presence of a pneumothorax, and monitor a pneumothorax for its development into a tension pneumothorax. Unlike increasing intracranial pressure, for which there is little to do but evacuate the victim, a tension pneumothorax can be relieved, increasing the chance of survival. The easiest and most effective technique a WEMT may learn is needle thoracostomy in the fifth intercostal space in the midaxillary line.

Medical Emergencies Diagnosing medical emergencies in the wilderness requires the WEMTs to be aware of essential signs and symptoms.

Environmental Emergencies The typical EMT course includes 3 to 6 hours of training in management of environmental emergencies. A WEMT course will have a minimum of 22 hours of additional training in environmental emergencies. “Hypothermia, frostbite, and nonfreezing cold injuries” covers cold injuries, which are among the most common environmental injuries seen in the backcountry. The WEMT must understand principles of thermoregulation; heat production and heat loss; recognition of hypothermia, frostbite, and immersion foot; and appropriate care. “Heatstroke, heat exhaustion, and dehydration” provides necessary information about the balance of heat production and heat loss in a hot environment and the fluid requirements necessary to support physiologic cooling. WEMTs need to know how to recognize and provide long-term care for victims of heat exhaustion, heatstroke, and dehydration.

Lifting and Moving Patients “Use of Stokes litters and improvising litters” discusses the primary device for evacuation from the backcountry. Even when a helicopter is used, the victim is usually “packaged” in a litter before being loaded. WEMTs must know the specific techniques for victim packaging in a litter to protect and support injuries. Proper carrying techniques and methods of belaying a litter up or down a steep slope are critical to the safety of everyone involved.

Ambulance Operations “Helicopter-assisted rescues” describes the use of helicopters in backcountry rescue efforts and evacuation. WEMT training should address the dangers, hazards, and limitations of helicopters.

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Self-Preservation Whether incidents or disasters are caused by nature or man, rescuers responding to remote places must know how to take care of themselves, from the moment they arrive to the time they return to safety. The classic mistake is when responders assume that there will be someone waiting to make sure that they have potable water, safe food, adequate shelter, and basic protection from the elements and from violence. This is never a safe assumption. When responding to a mountain rescue, each member is responsible for carrying a bivouac kit that contains all the necessities to sustain life in the wild for at least 24 hours. When responding to a disaster, each individual needs to be prepared to survive on his or her own for at least 3 days. Each member has to be potentially self-sufficient, carrying the essentials for survival in a disaster team bivouac kit. The kit must provide shelter and protection from elements, allowing the ability to produce potable water, calorie-rich foods, navigation, and light in the dark. Self-preservation is not an easy task. In the case of wilderness rescue, participants are often “outdoors people,” who before getting involved in search and rescue activities have already obtained wilderness skills. On the other hand, as teams form to respond to a larger disaster, they may be highly skilled medically but without essential survival skills, such as how to make potable water, choose safe foods, or establish a bivouac. The essentials of personal survival: Water: Humans need at least 2 liters of water per day to survive, 4 liters to maintain health, and much more if sweating heavily. Water can be a source of infectious disease, such as giardiasis, hepatitis, amebiasis, and cholera, any of which can cause major diarrhea and abdominal pain. It is absolutely essential to be able to produce potable, safe water. Three ways to produce potable water are: boiling, chemical disinfection, or filtering. Drinking potentially unsafe water puts the entire team at risk. Food: One must know what is safe to eat and how to properly prepare meals and maintain a clean “kitchen.” If refrigeration is not available, meat has to be kept alive until it is ready to be cooked. Safe food rules include: Eat only vegetables or fruits that can be peeled, once they are peeled. Eat vegetables that have been cooked and are served hot. Never eat raw, lightly cooked, or cold meats. Meat should be cooked until “well done” and served hot. Shelter: Shelter is both a roof over your head and clothing on your back. It is not enough to carry a tent; one also must have the skill to improvise or bivouac (build an emergency camp). Navigation: Know how to use a compass and read a map. One should be able to walk a straight line using a compass and determine the distance traveled. Other important items in the survival kit include sources of light, fire building materials, signaling devices, knife, parachute cord, spare socks, hat, and metal cup to make warm water. See Box 31-5. Attitude: The most important aspect of survival is attitude and confidence. Practice and experience build confidence. Maintaining a positive attitude will help ensure that you not only survive, but also thrive.

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APPENDIX The following is a list of organizations and committees dedicated to some aspect of extended medical, rescue, and technical training. Many are also active in mountain, wilderness, marine, or disaster rescue and management efforts. Advanced Wilderness Life Support (AWLS) University of Utah School of Medicine 358 South 700 East B509 Salt Lake City, UT 84102 888-521-2957 www.awls.org Resource: Teaches AWLS certification programs and practical approaches to prevention and treatment of injuries and illnesses related to the wilderness environment. Aerie Backcountry Medicine 240 North Higgins Suite 16 Missoula, MT 59807 406-542-9972 E-mail: [email protected] www.aeriemed.com Resource: Emphasizes prevention, treatment, and improvisation; offers wilderness EMT, wilderness first responder, wilderness first aid, avalanche, and swift-water rescue courses. American Alpine Club 710 Tenth Street, Suite 100 Golden, CO 80401 303-384-0110 www.americanalpineclub.org Resource: Publishes the American Alpine Journal and annual Accidents in North American Mountaineering. Has committees dedicated to establishing and promoting standards in safety and education in mountaineering. American Mountain Guides Association (AMGA) Physical address: 1209 Pearl St. Suites 12 and 14 Boulder, CO 80302 Mailing address: P.O. Box 1739 Boulder, CO 80306 Phone: 303-271-0984 Fax: 303-271-1377 www.amga.com Resource: Dedicated to establishing and maintaining standards for mountaineering and professional mountain guides. Publishes quarterly Mountain Bulletin. Appalachian Mountain Club 5 Joy Street Boston, MA 02108 617-523-0655 E-mail: [email protected] www.outdoors.org Resource: Active mountain rescue team that offers a variety of workshops on outdoor skills, environmental issues, and wilderness medical and rescue skills. Publishes quarterly Appalachia.

International Society for Mountain Medicine (ISMM) PO Box 31142 Colorado Springs, CO 80931-1142 Phone: 719-572-1372 Fax: 719-572-1514 or 800-967-7494 (in the United States) E-mail: [email protected] www.ismmed.org Resource: An international organization dedicated to research and education in mountaineering. Publishes the quarterly Newsletter of the ISMM. Mountain Rescue Association P.O. Box 880868 San Diego, CA 92168-0868 Fax: 619-374-7072 www.mra.org Resource: National wilderness rescue organization dedicated to the development of standards and certification of mountain rescue teams. Nantahala Outdoor Center 13077 Highway 19 W Bryson City, NC 28713-9165 Phone: 888-905-7238 or 828-488-2176 www.noc.com Resource: Offers a variety of courses on white-water rescue and wilderness medical and rescue training. National Association for Search and Rescue P.O. Box 232020 Centreville, VA 20120-2020 703-222-6277 Toll Free: 877-893-0702 E-mail: [email protected] www.nasar.org Resource: National information resource for search and rescue, as well as certifications in various search functions. Publishes quarterly journal Response. National Cave Rescue Commission (NCRC) c/o National Speleological Society Cave Avenue Huntsville, AL 35810 205-852-1300 EMERGENCY: National Rescue Coordination: 800-8513051 www.caves.org/io/ncrc Resource: Active national cave rescue team. National Ski Patrol System, Inc. (NSP) Ski Patrol Building, Suite 100 133 South Van Gordon Street Lakewood, CO 80228 Phone: 303-988-1111 Fax: 800-222-4754 E-mail: [email protected] www.nsp.org Resource: Active rescue teams and ski patrols. Offers an outdoor emergency care course, various ski patrol certifications, avalanche training, and introductory mountaineering training.

Chapter 31: Wilderness Emergency Medical Services and Response Systems Stonehearth Open Learning Opportunities (SOLO) P.O. Box 3150 Conway, NH 03818 603-447-6711 888-SOLO-MED E-mail: [email protected] www.soloschools.com Resource: An international organization dedicated to developing and offering a variety of courses and certifications in wilderness and marine medicine, rescue, leadership, and outdoor skills. An active mountain rescue team. Publishes bimonthly Wilderness Medicine Newsletter. Union Internationale des Associations d’Alpinisme (UIAA) (International Mountaineering and Climbing Federation) Monbijoustrasse 61 Postfach CH-3000 Bern 23/Switzerland Tel: +41 (0)31 370 1828 Fax: +41 (0)31 370 1838 E-mail: [email protected] www.uiaa.ch Resource: An international organization dedicated to the promotion of standards, safety, awareness, and education in mountaineering worldwide. Produces multiple publications on mountain safety and medicine. U.S. Coast Guard Headquarters 2100 Second Street, SW Washington, DC 20593-0001 202-267-1012 (Boating Operations) www.uscg.mil Resource: Active national marine rescue military organization. Source of information and various boatingrelated certifications. Wilderness Medical Associates 400 Riverside Street, Suite A-6 Portland, ME 04103 Phone: 207-797-6005 or 888-WILDMED (945-3633 within US and Canada) Fax: 207-797-6007 E-mail: [email protected] www.wildmed.com Resource: Offers a variety of courses and certifications in wilderness medical and rescue courses. Wilderness Medical Society 810 E. 10th Street, P.O. Box 1897 Lawrence, KS 66044 Phone: 800-627-0629

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Fax: 785-843-1853 E-mail: [email protected] www.wms.org Resource: A physician-based national wilderness medical organization with various committees dedicated to education in wilderness emergency medicine. Particular attention to education for physicians. Publishes quarterly newsletter and peer-reviewed journal Wilderness and Environmental Medicine (formerly Journal of Wilderness Medicine). Wilderness Medicine Institute of the National Outdoor Leadership School (NOLS) 284 Lincoln Street Lander, WY 82520-2848 Phone: 800-710-NOLS Fax: 307-332-1220 www.nols.edu/wmi Resource: Offers a variety of courses and certifications in wilderness medicine and rescue.


SUGGESTED READINGS American Academy of Orthopedic Surgeons: Emergency Care and Transportation of the Sick and Injured, 7th ed. Sudbury, MA, Jones & Bartlett, 1999. Auerbach P: Medicine for the Outdoors. New York, The Lyons Press, 1999. Bowman W: Outdoor Emergency Care, 3rd ed. Lakewood, CO, National Ski Patrol System, 1998. Forgey W (ed): Wilderness Medical Society: Practice Guidelines for Wilderness Emergency Care. Merrillville, IN, ICS Books, 1995. Henry M, Stapleton E: EMT Prehospital Care, 2nd ed. Philadelphia, WB Saunders, 1997. Houston C: Going Higher, 4th ed. Seattle, The Mountaineers Books, 1998. Iverson KV (ed): Position Statements of the Wilderness Medical Society. Point Reyes Station, CA, Wilderness Medical Society, 1989. Lindsay L, et al: Wilderness First Responder, Wilderness and Environmental Medicine. Lawrence, KS, Alliance Communications Group, 1999. McSwain N, et al: The Basic EMT: Comprehensive Prehospital Care, 1st ed. St Louis, Mosby, 1997. Mistovich, J et al: Prehospital Emergency Care and Crisis Intervention, 6th ed. Upper Saddle River, NJ, Brady, 2000. Schimelpfenig T, Lindsey L: NOLS Wilderness First Aid. Lander, WY, National Outdoor Leadership School, 1991. U.S. Department of Transportation, National Highway Traffic Safety Administration: Emergency Medical Technician-Basic: National Standard Curriculum, 4th ed. Washington, DC, 1994, U.S. Government Printing Office. Wilkerson J (ed): Medicine for Mountaineering, 4th ed. Seattle, The Mountaineers Books, 1993. Williamson J (ed): Accidents in North American Mountaineering, Golden, CO, American Alpine Club, published yearly.

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32

Search and Rescue Donald C. Cooper, Patrick H. LaValla, and Robert C. Stoffel

As ever-increasing numbers of outdoor users turn to the wilderness for recreation, the medical community and search and rescue (SAR) organizations are contending with a growing number of lost, sick, and injured persons. Wilderness search, rescue, and medical intervention are unique in several ways. All aspects of SAR are enormously time consuming. Simply raising the alarm for someone lost or injured in an isolated area may take hours, days, or even weeks. Organizing a response, including obtaining equipment and transportation for responders, requires a variable amount of time, depending on the level of preparedness of the response organization. Locating, gaining access to, stabilizing, and transporting a victim to definitive care can be a lengthy process. Because it takes many persons to perform a wilderness rescue (six or eight persons are required to carry a litter 1 mile), logistic considerations such as food, shelter, and transportation for responders quickly create their own problems. SAR personnel are subjected to the same risks and environmental stresses that compromise victims. To obviate further tragedy, they must have a heightened awareness of potential danger, adverse conditions, and personal limitations. In addition to basic and advanced life support training, rescuers must have extensive wilderness experience—or experience in the particular environment in which they will be operating—that combines practicality with creativity and resourcefulness. SAR personnel must have training in survival, improvisation, communications, leadership, navigation (e.g., map, compass, and global positioning system [GPS]), first aid, and specific SAR techniques. Many interventions, such as cardiopulmonary resuscitation, defibrillation, tube thoracostomy, tracheal intubation, and intravenous therapy, are difficult—if not impossible—in the wilderness setting. Examinations may be hampered by the bulky clothing necessary to keep the victim warm and dry. Medications and equipment are subject to rough handling and extremes of temperature, which may render them ineffective, unsterile, or inoperative (see Appendix: Drug Storage and Stability). Finally, decision making that optimizes patient care while not unduly risking the well-being of SAR personnel requires experienced leadership grounded in both common sense and technical skill. Perhaps the demands of SAR were best summarized by the wise rescuer who said that climbers, divers, hikers, and other outdoor enthusiasts get to choose where they practice their skills, but SAR personnel have no such choice. The situation, usually urgent, dictates where and when rescuers practice their art. The same situation that already compromised at least one person’s health or well-being subsequently endangers the SAR participants.

This chapter introduces medical professionals to the unique search, rescue, and medical problems encountered in wilderness, remote (including urban disaster environments), and backcountry situations. The rudiments of SAR coordination, resources, and specialized problems are discussed. This information will help medical personnel understand how the SAR community works and provide an educational foundation to help prevent situations requiring undue risk, or SAR personnel themselves from having to be rescued.


SEARCH AND RESCUE: AN OVERVIEW

SAR systems provide the response for overdue, lost, injured, or stranded persons, usually in connection with outdoor activities and environments. In the context of SAR, “wilderness” can take on several meanings. For instance, most consider wilderness to be regions that are uninhabited and uncultivated. Personnel may be called out to search a natural area such as a large park or desert, but it is equally likely that a search will be urban, in an area devastated by a natural disaster such as an earthquake or hurricane. Because most of the population in the United States resides in urban areas, emergency responders and SAR personnel are far more likely to encounter urban wilderness than a natural one. However, this chapter focuses on the nonurban setting. Types of SAR emergencies vary nationally and internationally, as do the responders. Programs, equipment, and personnel differ geographically in accordance with local needs and available resources. SAR can generally be defined as “finding and aiding people in distress-relieving pain and suffering.”5 However, contemporary references find it most useful to define “search” and “rescue” separately (Box 32-1).16 SAR often involves a great many volunteers and entails a multitude of skills. The eruption of Mt. St. Helens (1980), terrorist attacks on the World Trade Centers (2001), multiple hurricanes that struck the southeastern United States in 2004 and 2005, including Katrina, and the Indonesian earthquake and subsequent tsunamis of 2004, are all examples of significant, yet vastly different, threats and hazards requiring widely diverse sets of SAR skills. SAR operations benefit comprehensive emergency management, providing a training ground and experience builder for disaster response capability at the most elementary level. The management concepts used in SAR operations establish foundation principles for providing response capability to large-

Chapter 32: Search and Rescue

Box 32-1. Search and Rescue Defined Search—An operation using available personnel and facilities to locate persons in distress. Rescue—An operation to retrieve persons in distress, provide for their initial medical or other needs, and deliver them to a place of safety. From the International Maritime Organization and International Civil Aviation Organization (IMO/ICAO): International Aeronautical and Maritime Search and Rescue Manual: Vol. I, Organization and Management; Vol. II, Mission Co-ordination; and Vol. III, Mobile Facilities. London/Montreal, The International Maritime Organization (IMO) and the International Civil Aviation Organization (ICAO), 1999.

scale emergencies and disasters. Nearly every type of hazard mentioned in comprehensive emergency management plans (local and state disaster coordination plans, mandatory in all states) and international treaties require planning for search and rescue.24 Management of these SAR operations can range from directing the actions of a few responders in a small community hit by minor flooding to managing an effort involving thousands of searchers in a large urban calamity. Often, large situations involve several political subdivisions (e.g., counties, states, countries) and coordination of air and ground resources. Local governments and other agencies that participate in SAR response must coordinate diverse multiskilled responders. In addition, many agencies that collectively support multiorganizational SAR responses operate under their own specific statutory authority.40 SAR operations entail a motivating time factor that focuses on a successful conclusion: finding or rescuing a missing, lost, or injured subject before he or she succumbs to the effects of the environment, injuries, or a specific hazard. To be effective, extremely diverse organizations must be drawn together in a life-threatening situation with a commonality of purpose; this is even more true during a large-scale disaster.

International Agreements International conventions are often what countries use to establish rules between them. The Convention on International Aviation, the International Convention on Maritime Search and Rescue, and the International Convention for the Safety of Life at Sea (SOLAS) include rules requiring countries that are parties to these agreements to provide aeronautical and maritime SAR coordination and services for their territories and territorial seas. Coverage of the high seas is apportioned among the member countries by these instruments as well. To carry out its SAR responsibilities, a country usually establishes a national SAR organization, or joins one or more other countries to form a regional SAR organization. In the United States, the national SAR organization is called the National Search and Rescue Committee (NSARC). While airborne, virtually all commercial aircraft on international routes are under positive control (e.g., followed by radar and in direct communication with air traffic controllers) by air traffic services (ATS) units. The International Civil Aviation Organization (ICAO) has linked ATS units into a worldwide system. Consequently, SAR agencies are usually notified very quickly when an international commercial flight has an

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emergency. Commercial aircraft on domestic routes and general aviation aircraft may not be under positive control, which can result in delayed reporting of their emergencies. 121.5 MHz is the international aeronautical distress frequency and is monitored by ATS, some commercial airliners, and other aeronautical facilities where needed to ensure immediate reception of distress calls. Emergency locator transmitters (ELTs) are carried in most aircraft and are required in most aircraft flown in the United States (see COSPAS-SARSAT). Additional information on international SAR may be found at the International Maritime Organization (IMO) website (www.imo.org) and ICAO website (www.icao.int).

International Stages of SAR Operations The international SAR community has developed an approach to organizing operations that has evolved over the past several decades. This system is documented in the International Aeronautical and Maritime SAR (IAMSAR) Manual that was developed jointly by the ICAO and the IMO. Each of the three IAMSAR Manual volumes is written with specific SAR system duties in mind and can be used as a stand-alone document or in conjunction with the other two volumes as a means to attain a full view of the SAR system. Volume 1, Organization and Management, discusses the global SAR system concept, establishment and improvement of national and regional SAR systems, and cooperation with neighboring countries to provide effective and economical SAR services. Volume II, Mission Coordination, assists personnel who plan and coordinate SAR operations and exercises. Volume III, Mobile Facilities, is intended to be carried aboard rescue units, aircraft, and vessels to help with performance of a search, rescue, or on-scene coordinator functions and with aspects of SAR that pertain to their own emergencies. The IAMSAR Manual describes a series of five stages of a SAR operation through which most SAR events pass: Awareness, Initial Action, Planning, Operations, and Conclusion. The manual suggests that, “These stages should be interpreted with flexibility, as many of the actions described may be performed simultaneously or in a different order to suit specific circumstances.”16 The reason the IAMSAR Manual does not have a “Preplanning” stage is twofold. First, the five stages of a SAR operation are about what happens in a specific incident. Preplanning can address types of incidents, but not specific incidents. Second, the preplanning function is addressed in what are called plans of operations or operations plans (OPLANs); see Appendix C of the IAMSAR Manual, volume II. These are “standing” plans for how to deal with various kinds of situations.

Awareness Stage A SAR organization cannot respond to an incident until it becomes aware that someone is in need of assistance. At this stage, information is received that someone (or an aircraft or vessel) is, or will be, in distress. There may not be enough information to initiate action, or action may not be necessary yet.

Initial Action Stage When enough information is available, immediate action may be necessary. The first action is always to evaluate the information available, attempt to gain more, and determine the degree of the emergency. The “phase” of the emergency is used

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by the SAR authority to describe the level of confidence in the available information and the level of concern it raises about the safety of an aircraft or vessel and the persons on board. The IAMSAR Manual describes three emergency phases: uncertainty, alert, and distress. Uncertainty phase: a situation wherein doubt exists as to the safety of an aircraft or vessel and the persons on board Alert phase: a situation wherein apprehension exists as to the safety of an aircraft or vessel and the persons on board Distress phase: a situation wherein there is reasonable certainty that a vessel or other craft, including an aircraft or person, is threatened by grave and imminent danger and requires immediate assistance An overdue aircraft, as an example, may be late for a wide range of reasons. The phases of the emergency allow persons in charge to establish and communicate a summary of the available information that matches its validity, the urgency of action, and the extent of the response required. The IAMSAR Manual requires specific initial actions based on the established emergency phase.

Planning Stage Planning operations is essential, especially when the location of the distress situation is unknown. “Proper and accurate planning is critical to SAR mission success; if the wrong area is searched, there is no hope that search personnel will find the survivors, regardless of the quality of their search techniques or the amount of their search effort.”16 The IAMSAR Manual suggests the use of computers for operational planning, but also includes basic information on manual methods of planning searches.

Operations Stage The operations stage encompasses all the physical activities involved in finding, providing assistance to, and rescuing people in distress. In short, this phase is where the plans are carried out.

Conclusion Stage The conclusion stage is entered when it is determined that no one is in distress, when the search or rescue is concluded, or when nothing was found, and the search is called off. This phase is when all SAR resources are notified that the mission is concluded.

COSPAS-SARSAT The SARSAT system (search and rescue satellite-aided tracking) was developed in a joint effort by the United States, Canada, and France. The COSPAS system (cosmicheskaya sistyema poiska avariynich sudov; in English, “space system for the search of vessels in distress”) was developed by the Soviet Union. These four nations banded together in 1979 to form COSPAS-SARSAT. In 1982, the first satellite was launched and the first life saved using the system. By 1984, the system was declared fully operational. As of this writing, the four original member nations have been joined by 31 other nations that operate 47 ground stations and 25 mission control centers worldwide or serve as search and rescue points of contact (SPOCs). Visit www.cospas-sarsat.org or www.sarsat.noaa.gov for more details. The system uses satellites to detect and locate emergency beacons carried by ships, aircraft, and individuals. The system

consists of a network of satellites, ground stations, mission control centers, and rescue coordination centers. When an emergency beacon is activated, the signal is received by a satellite and relayed to the nearest available ground station. The ground station, called a local user terminal (LUT), processes the signal and calculates the position from which it originated. This position is transmitted to a mission control center (MCC), where it is joined with identification data and other information on that beacon. The MCC then transmits an alert message to the appropriate rescue coordination center (RCC) based on the geographic location of the beacon. If the location of the beacon is in another country’s service area, then the alert is transmitted to that country’s MCC (see Fig. 2-2 in Chapter 2).

Distress Radio Beacons The most recognizable component of the SARSAT system is the distress radio beacon, also known as a “beacon.” There are generally three types of beacons used to transmit distress: emergency position indicating radio beacons (EPIRBs) designed for maritime use, ELTs designed for aviation use, and personal locator beacons (PLBs) designed for use by individuals and land-based applications. Although the three types of devices are physically different owing to the differing environments in which they must operate, they all work on the same principle and in the same way. When turned on, each transmits alert signals on specific frequencies intended to be received by COSPAS-SARSAT satellites.

Emergency Position Indicating Radio Beacons. EPIRBS in use for maritime applications are of two types. One type transmits an analog signal on 121.5 MHz. The other type transmits a digital identification code on 406 MHz and a low-power “homing” signal on 121.5 MHz. The U.S. Coast Guard (USCG) maintains an outstanding website with more information on EPIRBs: www.navcen.uscg. gov/marcomms/gmdss/epirb.htm. Emergency Locator Transmitters. ELTs were the first emergency beacons developed, and most aircraft are required to carry them. ELTs were intended for use on the 121.5-MHz frequency to alert aircraft flying overhead. Obviously, a major limitation to these is that another aircraft must be within range and listening to 121.5 MHz to receive the signal. One of the reasons the COSPAS-SARSAT system was developed was to provide a better receiving source for these signals. Another reason was to provide location data for each activation (something that overflying aircraft were unable to do). Different types of ELTs are currently in use. There are about 170,000 of the older-generation 121.5-MHz ELTs in service in the United States. Unfortunately, these have proved to be highly ineffective. They have a 99% false alert rate, activate properly in only 12% of crashes, and provide no identification data. In order to fix this problem, 406-MHz ELTs were developed to work specifically with the COSPAS-SARSAT system. These ELTs dramatically reduce the false alert impact on SAR resources, have a higher accident survivability success rate, and decrease the time required to reach accident victims by an average of 6 hours. Presently, most aircraft operators are mandated to carry an ELT and have the option to choose either a 121.5-MHz or a 406-MHz version. A 1996 U.S. Government study concluded that 134 extra lives and millions of dollars in SAR resources

Chapter 32: Search and Rescue could be saved per year if only the 406-MHz type ELTs were used.27 Unfortunately, 406-MHz ELTs cost nearly three times as much as 121.5-MHz ELTs, and convincing aircraft owners to upgrade has been a slow process. On the recommendation of ICAO and IMO, the COSPASSARSAT Council announced in 2000 that it will be phasing out 121.5/243-MHz satellite alerting from the system. Users of 121.5/243-MHz beacons will have until February 1, 2009 to switch over to the generally superior 406-MHz models.

Personal Locator Beacons. PLBs are portable units that operate much the same as EPIRBs or ELTs. These beacons are designed to be carried by an individual person instead of on a boat or aircraft. Unlike ELTs and some EPIRBs, they can only be activated manually and operate exclusively on 406 MHz in the United States. Similar to EPIRBs and ELTs, all PLBs also have a built-in, low-power homing beacon that transmits on 121.5 MHz. This allows rescue forces to home in on a beacon once the 406-MHz satellite system has put them within 2 to 3 miles (3.2–4.8 km). Some newer PLBs also allow GPS units to be integrated into the distress signal. This GPS-encoded position dramatically improves the location accuracy down to the 100-meter level. In the United States, PLBs were in limited use until July 1, 2003, after which they were fully authorized for nationwide use. The National Oceanic and Atmospheric Administration encourages all PLB users to be acutely aware of the responsibility that comes with owning one of these devices. PLBs are a distress alerting tool and work exceptionally well. PLB users should familiarize themselves with proper testing and operating procedures to prevent false activation and be careful to avoid their use in nonemergency situations.27

Search and Rescue in the United States SAR involves many agencies and volunteers. The federal government assumes some responsibility for overall coordination, especially of federal or military resources requested by local or state agencies.

U.S. National Search and Rescue Plan The U.S. National Search and Rescue Plan (NSP) was first published in 1956. It provides guidance to signatory federal agencies (Departments of Transportation, Defense, and Commerce, as well as the Federal Communications Commission [FCC], the National Aeronautics and Space Administration [NASA], and the land management components of the Department of the Interior) for coordinating civil SAR services to meet domestic needs and international commitments. The federal government assists with coordination of certain SAR services, including any federal or military resources that are requested by local or state agencies. Guidance for implementing the NSP is provided in the IAMSAR Manual, the National Search and Rescue Supplement (NSS, a domestic interagency supplement to the IAMSAR Manual; discussed later), and other relevant directives of the plan participants.28 NSARC is responsible for coordinating and improving federal involvement in civil SAR for aeronautical, maritime, and land communities within the United States. NSARC is also the federal-level committee formed to sponsor and oversee the NSP. Member agencies of NSARC are the signatories of the NSP. More information about NSARC may be obtained from the Committee’s web site at www.uscg.mil.

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The IAMSAR Manual and the NSP define a SAR region (SRR) as “an area of defined dimensions, associated with a rescue coordination center (RCC), within which SAR services are provided.”16,28 An RCC is a unit responsible for promoting efficient organization of SAR services and for coordinating the conduct of SAR operations within an SRR. For every SRR, there is one RCC, and the goal is to have no overlaps or gaps between SRRs around the world. In the United States, there are two types of SRRs: maritime and aeronautical. Although only the ocean areas surrounding the United States and its territories fall within the maritime SRRs (marine vessels cannot sail on land), both the ocean and land areas of the United States fall within aeronautical SRRs (aircraft can fly over both water and land). The maritime SRRs surrounding the United States include, in the Pacific: Juneau, Honolulu, Seattle, and Alameda; and, in the Atlantic: Boston, Norfolk, Miami, New Orleans, and San Juan. The oceans surrounding the United States and its territories also fall within aeronautical SRRs whose names and limits coincide with their maritime counterparts. However, with the exception of U.S. islands (Hawaiian, Puerto Rico, etc.) that are contained entirely within maritime SRRs and the Great Lakes (Cleveland Maritime SRR), all U.S. land falls within either the Elmendorff Aeronautical SRR (Alaska) or the Langley Aeronautical SRR (continental United States). According to the NSP, an SAR coordinator has overall responsibility for establishing RCCs as necessary and for providing or arranging for SAR services with U.S. SRRs.16 The SAR Coordinators for the United States are as follows: • The U.S. Air Force for the recognized U.S. aeronautical SRR corresponding to the continental United States other than Alaska; • The U.S. Pacific Command for the recognized U.S. aeronautical SRR corresponding to Alaska; and • The USCG for the recognized U.S. aeronautical and maritime SRRs that coincide with the ocean environments, including Hawaii. Although not considered a national SAR coordinator, the National Park Service is the lead agency that provides SAR and other emergency services within national parks. In small parks, this is often achieved through agreements with surrounding emergency service providers. Outside national parks, state and local authorities or SAR units often accept responsibility for providing domestic land SAR services. Because of the unique scale and SAR challenges in Alaska, the USCG is the lead federal agency for inland SAR in certain areas of the state, including the Alaska Peninsula (south of 58° N), the Aleutian Islands, and all other coastal islands. The reason for this is simple: USCG assets can respond much quicker than can the U.S. Air Force Anchorage RCC to these areas. The Alaska State Troopers are the state agency responsible for land SAR in Alaska. Because of the unforgiving environment, all federal, state, and local agencies work together closely in response to SAR missions in Alaska. In addition to the specific assignments of SAR coordinators, the NSP allows “. . . local and state authorities to designate a person to be a SAR Coordinator within their respective jurisdictions.”28 These local and state SAR coordinators, if established, become important contacts for national SAR coordinators. Many U.S. states have chosen to retain established SAR responsibilities within their boundaries for incidents primarily

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local or intrastate in character. In such cases, agreements have been made between SAR coordinators and relevant state organizations.

of these searches may take the form of overdue aircraft, ELTs, hunters, hikers, or children.

The National SAR Supplement

Rescue. A rescue mission entails the use of federal SAR forces to recover persons in distress whose location in a remote area is known, but who need assistance. This may be in the form of transportation to safety or to an adequate medical facility. These requests are normally received by the AFRCC from park service personnel or the local law enforcement authority.

NSARC also directs preparation of the NSS, which provides guidance to federal agencies concerning implementation of the NSP. The NSS provides specific additional national standards and guidance that build on the baseline established by the IAMSAR Manual. It provides guidance to all federal forces, military and civilian, that support civil SAR operations.29 Specifically, the NSS is designed to serve as both a training and operational tool for civil SAR operations. SAR planning is both an art and a science, relying greatly on the creativity and experience of the personnel involved. Because of the many variables encountered during SAR operations and the individuality of each SAR case, the guidance provided in the NSS must be tempered with sound judgment, having due regard for the individual situation. Very little in the NSS is mandatory because it is not intended to relieve SAR personnel of the need for initiative and sound judgment.29 Each of the signatory agencies of the NSARC (and NSP) may also develop an “addendum” to the NSS for their agency. Such documents could include policies, information, procedures, and so forth, on civil SAR matters applicable to the agency concerned, and consistent with the IAMSAR Manual and NSS. The NSS is available on the USCG website (www.uscg.mil).

U.S. Rescue Coordination Centers The USCG and Air Force both operate RCCs in the United States, but each service takes a slightly different approach. The Air Force RCC (AFRCC) coordinates inland SAR activities in the continental United States but does not directly conduct SAR operations. In most situations, the Civil Air Patrol (CAP), state police, or local rescue services carry out the actual SAR operations. In contrast, the USCG not only coordinates but also conducts maritime SAR missions.

U.S. Air Force Rescue Coordination Center. Established in 1947 to meet the growing demand for SAR and its legislated responsibility, the original three AFRCCs have evolved into a single RCC located at Langley Air Force Base in Hampton, Virginia, under the Air Combat Command. The peacetime mission of the AFRCC is to build a coordinated SAR network, ensuring timely, effective lifesaving operations whenever and wherever needed. As of December 2003, the AFRCC recorded the prosecution of more than 58,000 SAR missions, resulting in more than 13,500 lives saved.36 The AFRCC functions around the clock and is staffed by people trained and experienced in the coordination of SAR operations. The center is equipped with extensive audio and digital communications equipment and maintains a comprehensive resource file listing federal, state, local, and volunteer organizations that conduct or assist SAR efforts in the United States, Canada, and Mexico. There are four types of authorized AFRCC missions: search, rescue, MEDIVAC, and mercy. Search. Once a distress situation is determined to exist but a location is unknown, federal SAR forces may be activated to search for, locate, and relieve the distress situation. The object

MEDIVAC. The transportation by federal assets of persons from one medical facility to another is defined as aeromedical evacuation, or MEDIVAC. Requests are normally received from a local hospital when no commercial transportation is available, the person’s life is in jeopardy, and time is critical. Each request is evaluated, and the decision to use federal resources is weighted heavily by the attending physician’s medical opinions. Mercy. A mission to transport blood, organs, serum, medical equipment, or personnel to relieve a specific time-critical, lifethreatening situation is referred to as a mercy mission. Requests are normally referred from a local hospital authority or, in some cases, the American Red Cross when commercial transportation is not available. Although the AFRCC will accept and act on initial notification from any person or agency, it will attempt to determine the urgency and the facts pertaining to the situation before obliging itself. Several aspects of the situation are considered before a mission is opened, including the following: 1. Medical evaluation and urgency 2. State agreement requirements 3. Posse Comitatus Act 4. Conflict of interest with commercial resources 5. Resource availability The medical condition of the victim or victims is the most important aspect of mission consideration. The AFRCC will only consider a request valid when there is an immediate threat to life, limb, or sight. A mission will only be started to prevent death or the aggravation of a serious injury or illness. The observations and opinions of a physician at the incident site weigh heavily on the decision to open a mission, and a flight surgeon is on call at the AFRCC when a local physician is unavailable. Each state has an agreement on file in the AFRCC describing the responsible agency and coordinating requirements for the various types of SAR missions. Each request for federal assistance is evaluated to ensure the requirements stipulated in the relevant agreement are met. Title 18 USC 1385 (the Posse Comitatus Act) prohibits military participation in civil law enforcement activities. Although there are some exceptions to the prohibition, as a general rule, Department of Defense (DOD) forces, including the CAP, will be restricted from participating in searches in which the person being sought is evading searchers, or is a fugitive, or when foul play is considered. On MEDIVAC or mercy missions in which the patient is not eligible for DOD medical benefits, federal assets cannot be used when commercial resources are available. Even when a patient is unable to pay or is destitute, commercial resources will be checked for availability and provided the opportunity to accept the mission before allocating federal resources.

Chapter 32: Search and Rescue Although any SAR-capable asset belonging to the federal government may be requested, each resource is evaluated for distance from the distress location, special equipment requirements, urgency of the situation, and which resource can best accomplish the mission. Military forces may be called on to assist in civilian SAR missions. However, their participation in these activities must not interfere with their primary military mission. Once the decision has been made to use federal resources, a mission number is assigned and SAR forces are selected based on the geographic location and mission requirements. The Air Force coordinator then works closely with the responsible agency in an attempt to provide the resources best suited to accomplish the mission.36 Additional information on the AFRCC can be found at www.acc.af.mil/afrcc.

U.S. Coast Guard Rescue Coordination Centers. The USCG, now a division of the U.S. Department of Homeland Security (DHS), is designated as the federal SAR coordinator for the maritime SRRs surrounding the United States and large portions of the high seas. The USCG is responsible for providing and coordinating SAR services over 28 million square miles of the world’s oceans, mostly in the Northern Hemisphere. This responsibility is divided into two Areas: Atlantic and Pacific. These Areas are divided into several Districts, which are further divided into Groups (several per District) and Stations. A 24hour alert status is maintained year-round at all levels; Coast Guard resources can be underway or airborne within minutes of notification of a SAR incident. At its headquarters, each Area and District maintains a fully staffed operations/command center responsible for coordinating operations within the Area or District on a 24-hour basis. When coordinating SAR missions, these operations centers are called rescue coordination centers (RCCs). Although minor SAR incidents are often resolved at the Station or Group level, the District or Area assumes the duties of the SAR mission coordinator in more complex or large-scale missions.37 The USCG arguably prosecutes more SAR missions than does any other organization or agency. It is also notable that the USCG, although considered an important part of the United States military forces, is a separate federal agency now under the DHS, not under the Department of Defense, as is the Air Force. An important global SAR-related service of the USCG is the automated mutual-assistance vessel rescue (AMVER) system. AMVER involves ships, regardless of flag, voluntarily providing information about their capabilities (i.e., medical personnel on board, rescue equipment) and regularly reporting their location to a global computer system that tracks their whereabouts. When a situation arises that requires SAR capabilities, a surface picture (SURPIC) is produced that graphically shows the location of all AMVER participants in the vicinity. The RCC can use this information to select the best one or several ships to respond to the emergency, and allow all others to continue their voyages. Today, about 12,000 ships from more than 140 countries participate in AMVER. On average, 2800 ships are on the AMVER plot each day, with more than 100,000 voyages tracked annually. The AMVER system has saved more than 2000 lives since 1990.38 A “preventive SAR” service provided by the USCG as a direct result of the Titanic disaster is the International Ice Patrol, with

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operations funded by SOLAS Convention signatories.17 Since 1913, the Ice Patrol has amassed an enviable safety record, with not a single reported loss of life or property caused by collision with an iceberg outside the advertised limits of all known ice in the vicinity of the Grand Banks. However, the potential for a catastrophe still exists, and the Ice Patrol continues its mission using high-tech sensors and computer models.37 The USCG also performs or coordinates the medical evacuation of seriously ill or injured persons from vessels at sea if the patient’s condition warrants and USCG assets are within range. For less serious situations, USCG flight surgeons offer medical advice by radio. On rare occasion, the RCC may coordinate with a U.S. Navy ship to allow a USCG MEDIVAC helicopter to refuel to extend its range. Also on rare occasion, the RCC may coordinate with the Air Force to dispatch pararescue personnel to parachute to the vessel and stabilize the patient. In either case, these actions are taken only in the most serious situations when one or more lives depend on such drastic actions. If a vessel is reported overdue or unreported (i.e., failed to check in when expected), USCG assets may or may not launch immediately, depending on whether the overdue craft is thought to be in immediate danger. Regardless, an extensive investigative effort is initiated immediately. During this investigation, a preliminary communications check (PRECOM) and extended communications check (EXCOM) will likely take place. These actually include more than just contacting intended destinations. They also include interviewing persons who may be knowledgeable about the craft, as well as dispatching USCG vehicles or small boats to physically check harbors, marinas, launching ramps, and the like. In addition, an urgent all-ships broadcast is initiated requesting information on any recent or future sightings that might be the missing vessel, and EXCOMs are repeated on a regular basis.16 If none of these communications and investigation efforts produces positive results (i.e., locating the vessel or indications that the persons on board are not in immediate danger), a search is undertaken. Search planning is conducted by the RCC staff, but additional assets can be requested from other agencies (i.e., U.S. Air Force and Navy) or foreign governments in a position to assist. With assistance from the USCG’s computer-assisted search planning (CASP) system, the RCC develops scenarios based on the available information. These scenarios are then weighted according to a subjective estimate of how likely each one is to represent the true situation. The further analysis of available information leads to development of probability maps (using CASP), after which a search is planned and orders are issued to all participating units. The search continues until either the survivors are found and rescued, or it is deemed that further searching would be fruitless.11 Because SAR regions are not construed as boundaries to effective SAR action, and because the aeronautical SRRs are surrounded by the maritime SRRs, coordination between the AFRCC and the Coast Guard Rescue Coordination Centers is a daily occurrence. Missions that involve portions of both regions will be coordinated through the AFRCC or the appropriate Coast Guard RCC. It is not unusual for the Coast Guard to call upon the AFRCC for a particular resource needed to prosecute a mission in the maritime region or, conversely, for the AFRCC to utilize a Coast Guard resource in the aeronautical region.

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Additional information about the USCG can be found at http://www.uscg.mil/USCG.shtm.

Federal Aviation Administration. The Federal Aviation Administration (FAA), through its Air Route Traffic Control Centers (ARTCCs) and Flight Service Stations (FSSs), monitors and flight-follows aircraft filing flight plans in the aeronautical SAR regions. In some cases, individual citizens contact an FAA facility when they have knowledge of a probable SAR situation involving aircraft. Therefore, the FAA is usually the first agency to alert the AFRCC of a distressed or overdue aircraft. The AFRCC is tied directly into the FAA’s computer network, and FAA facilities use this system to alert the AFRCC. Once the AFRCC is alerted, the FAA and AFRCC work together to determine the urgency of the situation and locate the aircraft. Initially, radio communications are reviewed to determine the last known location of the distressed aircraft. Concurrently, other FAA facilities begin a check of all possible airports where the aircraft might have landed. In the meantime, the AFRCC contacts relatives, friends, and business associates of the pilot or passengers aboard the missing aircraft, with the hope of establishing the whereabouts of the aircraft, or to gather information about the personnel aboard. Through these contacts, the AFRCC determines the pilot’s intentions, flying capabilities, emergency equipment aboard, and other pertinent information that would assist if a search were to become necessary. Through experience, the FAA and AFRCC have learned that most alerts for missing aircraft are due to the pilot failing to either close the flight plan or inform some person or agency of his or her intentions. For this reason, only a small percentage of alerts issued by the FAA result in an actual airborne search for a missing aircraft. All ARTCCs have the capability to recall recorded radar data. The National Track Analysis Program (NTAP) can identify and track targets that are at a sufficient altitude to be tracked by radar regardless of whether they are being controlled by the ARTCC. NTAPs requested by the AFRCC have been proved to be a key ingredient in aircraft searches, providing the route of flight and last radar position. With the congressional mandate requiring most aircraft to be equipped with an ELT, the FAA works very closely with the USMCC and the AFRCC to readily locate the source of ELT signals. All ELT signals reported to FAA facilities are immediately forwarded to the AFRCC and jointly investigated as probable distress signals.41 Civil Air Patrol. In 1948, the CAP was permanently chartered by the U.S. Congress as the official auxiliary of the U.S. Air Force. As such, this nonprofit organization of volunteers was charged with three primary missions: the development of aviation through aerospace education, a cadet youth program, and emergency services. As of this writing, the CAP boasts more than 64,000 members, including more than 27,000 cadets between the ages of 12 and 20 years; the world’s largest fleet of single-engine, piston aircraft; and access to 1000 emergency service vehicles. It is proud of the fact that it saves 100 lives per year.4 Under their emergency services mission, the CAP provides SAR mission coordinators, search aircraft, ground teams, personnel on alert status, and an extensive communications network to emergency response efforts. Further, they provide services to national relief organizations during a disaster; trans-

portation of time-sensitive medical materials (e.g., blood and human tissue); and aerial reconnaissance, airborne communications support, and airlift of law enforcement personnel in the national counter-drug effort. When CAP resources are engaged in a SAR mission, they are reimbursed by the U.S. Air Force for communications expenses, fuel and oil, and a share of aircraft maintenance expenses. In addition, CAP members are covered by the Federal Worker’s Compensation Act in the event of an injury while participating in a SAR mission. The CAP is the AFRCC’s prime air resource for the inland area. The AFRCC maintains an alert roster provided by CAP wings in each of the 48 contiguous states and is the central point of contact for CAP participation in SAR missions. The AFRCC also works closely with CAP national headquarters and directly provides input for CAP training in emergency services.

U.S. Coast Guard Auxiliary. The USCG Auxiliary is to the USCG as the CAP is to the U.S. Air Force. The auxiliary is made up of citizens who volunteer their time and boats or aircraft to enhance and maintain the safety of boaters. Passage of the Auxiliary and Reserve Act of 1941 designated that civilian volunteers of the USCG be referred to as auxiliary. When America entered World War II, some 50,000 auxiliary members joined the war effort. After the war, their attention returned to recreational boating safety duties in compliance with the auxiliary’s four cornerstones: vessel examination, education, operations, and fellowship. Today, as in 1941, auxiliarists are civilian volunteers whose activities are directed by policies established by the commandant of the USCG. Although under the authority of the commandant, the auxiliary is internally autonomous, operating on four organizational levels (smallest to largest): flotilla, division, district regions, and national. When auxiliary resources are engaged under USCG “orders,” they are reimbursed by the USCG for communications expenses, fuel and oil, and a share of vessel and aircraft maintenance expenses. In addition, auxiliary members are covered by the Federal Worker’s Compensation Act in the event of an injury while participating in an authorized mission. Many members of the auxiliary spend their weekends providing free boating safety courses to the public and free courtesy safety inspections to boaters. However, members also respond to minor SAR incidents, and the local USCG Station, Group, or District RCC coordinates their activities. Some auxiliarists have also become qualified to work in the RCCs or assist regular USCG facilities with regulating and patrolling regattas and other maritime events.39 With its 36,600 members, the auxiliary saves hundreds of lives each year, in addition to assisting thousands of boaters, performing courtesy marine exams, teaching public and youth classes, and assisting the USCG in both administrative and operational missions.39

The State’s Role in SAR: Coordination and Support All states have passed legislation that provides for direct support to local government entities during emergencies or lifethreatening situations, and most states have a specific agency responsible for overall coordination and support for local SAR problems. This support can take many forms, but most often it is in the area of coordination and “one-stop shopping” for resources. Each state must establish an agency or central location that is familiar with all aspects of emergency management

Chapter 32: Search and Rescue and the resources available to aid in life-threatening situations. Many of these resources belong to the state and can be used to aid local jurisdictions. A number of states, especially in the Northwest, have designated a state agency to be responsible for directing and coordinating air SAR activities. These state departments, or divisions of aeronautics, develop and maintain aviation SAR response programs with cooperation and support from local and federal agencies. Experience shows that this system usually works better than those in other areas of the country that rely on the federal government to initiate and carry out aircraft SAR activities. If a local emergency manager, sheriff, or fire chief requests outside assistance in the form of specialized teams, search dogs, air support, or enhanced communications, the state agency for emergency services or emergency management can in most cases locate the nearest resources available and coordinate the response. If any federal resources are needed, such as air support or military personnel, the state agency provides a direct link to that resource. For instance, the AFRCC at Langley Air Force Base in Virginia has working agreements with all states that are updated annually. Technically, the resources of local and state governments must have been exhausted or be unable to perform a task before federal support can be rendered. However, policy provides for immediate aid when time is critical and in life-ordeath situations. Much discretion is given to military installation commanders regarding aid to civilian authorities, as long as the primary (military) mission of the resource is not impaired. In fact, most commanders appreciate the opportunity to fly actual missions. Access to these resources must be gained through the state and AFRCC. Every state’s emergency management agency is responsible for providing support, guidance, training, and coordination to local political subdivisions within that state. As such, it produces a vital behind-the-scenes effort to help local jurisdictions prepare for emergencies, including SAR. The state also initiates the laws necessary to enhance effective actions for SAR response. Such legislation often indemnifies volunteer SAR teams, provides their medical coverage and insurance, and in some cases replaces personal property lost during SAR work. Although most volunteers work willingly until the job is done, this recognition and coverage by the state often provide additional incentives for volunteer participation.

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readiness through daily missions that involve SAR work. Fire departments have historically been responsible for rescue and response to emergencies within certain geographic or political areas, and volunteers augment many departments. Law enforcement agencies also maintain full-time, efficient response systems designed for their particular SAR requirements. Ambulance and rescue vehicles operated by a variety of private enterprises and volunteer organizations augment existing local government services. Through local emergency response planning and coordination, these services respond to a spectrum of everyday emergencies, including fires, collapsed buildings, hazardous material spills, vehicle extrications, and home medical emergencies. County sheriffs, reserve law enforcement, volunteer fire departments, and a variety of volunteer and rescue units have been established to address local SAR problems. Delivery of SAR aid to rural and wilderness areas often presents many special logistic problems, which may be compounded by distance, terrain, and weather. The demand for wilderness SAR is often seasonal and unpredictable. Volunteer mountain rescue units, Explorer SAR groups, SAR dog teams, CAP squadrons, motorized units, and many types of volunteer composite teams (i.e., teams that have a variety of capabilities) are usually formed locally in response to the type and nature of recurring SAR problems. Regardless of what type of SAR emergencies occur, local resources and effort must be developed because they are closest to the problem. State and federal resources are subject to problems with time lag, distance, weather, logistics, and bureaucracy. The same storm or disaster that incapacitates a local area may also prohibit outside (and sometimes inside) emergency response and resupply. Although official agency responses differ greatly around the country, one major factor remains constant—the dedicated and unfailing willingness of volunteers to respond and work until the job is done. The volunteer effort in SAR nationwide is the backbone of aid to people in distress, as is stated in the rescue service motto: “These Things We Do That Others May Live.” The volunteer response has proved crucial to wilderness-type situations. Volunteer organizations, communications, and special skills cannot be replaced by any “official agency” resources.


ORGANIZATION OF A SEARCH AND RESCUE EVENT

Local SAR Response The official response to the call for a wilderness SAR situation is usually delegated to a political subdivision within the state. The legal responsibility for SAR is generally vested with the county sheriff or chief law-enforcement officer at the local level, but this varies by region and state. In some cases, it is the responsibility of state police agencies, and in others, it belongs to land management agencies. The SAR response for one jurisdiction may differ greatly from that of another. For instance, many national parks in some areas of the country handle all of their own SAR incidents. Others jointly manage the function, whereas some rely entirely on outside resources. National forest land is managed solely by forest service personnel, but when it comes to SAR, the forest service usually only supports the functions of the local responders. In urban and suburban areas, police officers, firefighters, emergency medical technicians, and emergency management organizations maintain some degree of disaster and emergency

SAR requires people who take action and meet objectives to achieve a common goal, often with one or more lives in the balance. For any combination of actions to be effective in a particular situation, the enterprise must be systematically coordinated and organized. All participants must know their responsibilities, what is expected of them, who is in charge, and to whom they answer. If this knowledge is lacking at any level, the effort can quickly become chaotic, ineffective, and, very probably, dangerous. Nowhere are these issues more important than in an emergency, when time is a crucial factor. Emergency response research is clear and specific. The four operational problems that continue to arise during emergency responses in the United States are ambiguity of authority, inability to communicate between agencies, poor use (or no use) of specialized resources, and unplanned negative interactions with the news media. Accordingly, the key elements for success in SAR operations continue to be good coordination of resources

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Incident commander Command staff

Liaison officer Safety officer Information officer

Section chiefs Branch directors Division or group supervisor

Operations

Air

Ground

Search

Dog team

Unit leaders

Planning

Finance/ administration

Logistics

Service

Support

Situation

Communication

Facilities

Time

Resources

Medical

Supply

Procurement

Documentation

Food

Ground support

Compensation claims

Water

Rescue

Trackers

Searchers

Demobilization Technical specialist

Cost

Figure 32-1. Functional hierarchy of the Incident Command System commonly used in SAR in the United States. (From Cooper DC [ed]: FUNSAR: Fundamentals of Search and Rescue. Chantilly,VA, Jones & Bartlett, 2005.)

(the right people and equipment in the right place at the right time), effective communications, and good management practices with trained leaders.24

Incident Command System The system designed to address the challenges of managing emergency incidents in the United States, including SAR, is called the Incident Command System (ICS). It has been in use in the United States for many years.31 This function-based system was designed to be adaptable to various types and sizes of incidents in a proactive, rather than a reactive, manner. The system groups similar tasks into five functional areas: command, operations, planning, logistics, and finance/administration. Each of these functions is performed at every incident to one degree or another, and all can easily be expanded as the size and complexity of the situation dictate. This expansion, however, is based on the premise that the span of control (the ratio of the subordinates to each supervisor) should never exceed seven to one and should more commonly be five to one. When this is exceeded, another level is added to the hierarchy to maintain an acceptable span of control (Fig. 32-1). The command section is led by the incident commander and provides overall management of the organization. Within ICS, the command section is responsible for dealing with other agencies (liaison officer), the news media, and other external influences (information officer) and is responsible for the overall safety of the operation and its participants (safety officer). If the incident is too small for these functions to be

performed by separate individuals, the incident commander performs them. The operations section is led by the operations section chief, who is responsible for coordinating and performing all tactical operations. This role is commonly performed by the incident commander until the incident becomes large and complex enough that the function must be performed by another individual. When multiple casualties are involved in an incident, their triage, treatment, and transport fall under the purview of the operations section. In such an incident, the operations section is divided into functional groups, often including at least triage, treatment, and transport groups. The person in charge of managing and coordinating the efforts of each group is called the group supervisor. If the operations section is better divided using geography, a division rather than a group is formed. For instance, injured persons at an auto accident might be found on two sides of a road. An east division and a west division might be established to deal with the geographic separation of the resources. In a small organization, the supervisor of each division would answer directly to the operations chief. To respond to specific challenges within an incident, a task force or strike team might be formed. A task force is any combination of single resources assembled for a particular tactical need, with common communications and a leader. For instance, the Federal Emergency Management Agency combines search, rescue, medical, and technical resources to form an urban search and rescue task force. A strike team, on the other hand, is a combination of a designated number of the same kind and type

Chapter 32: Search and Rescue of resources with common communications and a leader. The number of resources used in the team is based on what is needed to perform the function. For instance, four three-person hasty search teams may be combined to form a strike team. These two combinations of resources permit the necessary flexibility when allocating resources. The planning section is led by the planning section chief, who is responsible for collecting, evaluating, and distributing all incident information. As with the other sections, the incident commander performs this function unless the size and complexity of the incident dictate otherwise. In SAR, the planning section is particularly important because it evaluates search evidence and determines, based on what has been learned, what future actions should be taken or how current actions should be modified. Because such interpretation and evaluation often require great technical knowledge, personnel such as hazardous materials specialists, physicians, structural engineers, and other technical specialists may be required to help the planning section develop and revise the incident action plan. The logistics section is led by the logistics section chief, who is responsible for providing personnel, equipment, and supplies for the entire incident. This awesome task involves ensuring that personnel are available, rested, and fed; that all equipment, including communications equipment, is available and operable; that vehicles are fueled and repaired; and that medical care is provided for all incident personnel. Basically, logistics is charged with seeing that the physical tools required to meet the overall objectives are available, operable, and maintained. If the size and complexity of the incident prevent the incident commander from monitoring finance and administrative issues, the finance/administration section is led by the finance/administration section chief. This section is responsible for tracking all financial data for the incident, such as personnel hours, resource costs, costs for damage survey, and injury claims and compensation. Because most agencies involved in SAR can usually handle financial issues on their own, and most incidents are small and of short duration, the incident commander usually performs the functions of this section. Only in the largest or most complex incidents is it necessary for the incident commander to assign an individual or staff to perform finance section duties.

National Incident Management Systems In Homeland Security Presidential Directive-5 (HSPD-5), the President of the United States called on the DHS to develop a national incident management system (NIMS) to provide a consistent nationwide approach for federal, state, tribal, and local governments to work together to prepare for, prevent, respond to, and recover from domestic incidents, regardless of cause, size, or complexity. On March 1, 2004, after collaboration with state and local government officials and representatives from a wide range of public safety organizations, DHS issued the NIMS. It incorporates many existing best practices into a comprehensive national approach to domestic incident management, applicable at all jurisdictional levels and across all functional disciplines. Among these best practices, and a key component of the NIMS, is the incident command system, which has been established by the NIMS as the standard organizational structure for the management of all incidents.5 The NIMS represents a core set of doctrine, principles, terminology, and organizational processes to enable effective, efficient, and collaborative incident management at all levels.

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To provide the framework for interoperability and compatibility, the NIMS is based on a balance between flexibility and standardization. The recommendations of the National Commission on Terrorist Attacks upon the United States (the “9/11 Commission”) further highlight the need for the NIMS and the importance of ICS. The Commission’s 2004 report recommends national adoption of the ICS to enhance command, control, and communications capabilities.


FOUR PHASES OF A SEARCH AND RESCUE EVENT: THE INCIDENT CYCLE

Every SAR event goes through four consecutive phases: locate, access, stabilize, and transport (LAST).5 This sequence, however, could more accurately be described as a continuum that begins with planning or preplanning for the incident. Because planning for the next incident should be affected by what happened during the last, the incident cycle is actually continuous and only pauses between incidents. Once first notice of an incident has been received and the locate phase begins, the goal is to progress through the access, stabilize, and transport phases as quickly, safely, and efficiently as possible. Planning between incidents allows decisions to be made in a calm environment without the urgency that often accompanies a SAR operation. Such plans identify who will be in charge, the organization of the operation, specific procedures, viable alternatives, and other decisions that are best made before an incident occurs (Fig. 32-2).

Locate Phase The first step in addressing any emergency situation is locating the subject or subjects in need of assistance. This may be as simple as asking for an address or as complex as conducting an extended search for a lost person or persons. If the subject is easily found, rescuers can quickly move into the access phase. However, if locating the subject is difficult, this phase may turn into the crux of the SAR problem.

First Notice The first notice of an incident is often conveyed by relatives who report an injury or missing person, by a witness to an incident, by a government agency reporting distress signals (such as an ELT), by bystanders who perceive a problem, or by a 911 call. Once the initial notice is received, the individual taking the information must know what to do and whom to call next.

Planning Data and Its Uses Information gathered at the onset of an incident begins an ongoing investigation. It is used to determine the appropriate response and to help predict how the subject or subjects might react to the situation. This information is called planning data and includes any information that might affect what should be done to resolve the situation. Examples of planning data include name of the subject, situation that caused the problem, last known location of the subject, subject’s physical and mental condition, subject’s plans (where was he or she going?), available resources, weather information (present and predicted), geographic information, and history of similar incidents in the area. The purpose of collecting all this information is to help decide what to do next while predicting what the subject might do to help or hinder the situation.

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Mission “PRE”planning Located

First notice

L A

Mission suspension/ completion

Stabilized Accessed

Planning

Operations

Planning

Operations Mission critique

S T

Operations

Planning

Planning

Operations

Time

A Stabilized Located

Mission “PRE”planning

Accessed First notice

L A S T

Planning

Mission suspension/ completion

Operations

Operations

Planning

Mission critique Operations

Planning

Operations

Planning

Time

B Figure 32-2. The time-specific components of a SAR event vary with the type of incident. Note that all components take place in both incidents but require different amounts of time. A, Typical rescue operation. B, Typical search operation.

Chapter 32: Search and Rescue The investigation and gathering of information continue throughout the incident and are used to modify initial plans. As new information is acquired, an action plan is developed and revised until the end of the incident cycle, when planning for the next incident commences. Once information is gathered, the urgency of the situation is assessed. This assessment ultimately determines the speed, level, and nature of any response and may indicate whether a nonurgent or an emergency response is needed. The specific information used in urgency determination includes the age and condition of the subject, current and predicted weather, and relevant hazards. Figure 32-3 is an Urgency Determination Form, which can be used by SAR personnel to determine how urgent their response should be.5 Urgency also contributes to allowable risks and thus influences searcher safety—a primary consideration for search managers.

Search Tactics During the initial locate phase of the incident, emphasis is on searching for the subject. Exactly how to accomplish this is a priority, especially if this part of the incident cycle is expected to be a problem. SAR managers first initiate techniques that increase the chances of locating the subject in the shortest time. These techniques are generally termed tactics and involve some action performed to find the subject. These actions can be indirect (e.g., not requiring actual field searching) or direct (e.g., requiring deployment of searchers to the field). Examples of indirect tactics include confining the search area to limit movement of the subject and others into and out of the area, identifying and protecting the point last seen (PLS) or the last known position (LKP), and attracting the subject, if he or she is expected to be responsive. Generally, indirect techniques are quicker and easier to apply, so they are started first. As the incident progresses, direct tactics are initiated. In managing an incident, efforts are almost universally made to apply quick response resources in areas likely to offer early success. The best resources are put in the most likely areas as early as possible. In addition, identifying and protecting the PLS or LKP are crucial indirect techniques that can mean the difference between success and failure of the entire effort.5 Direct techniques include sending teams of searchers into an area to search for clues or the subject. They are categorized by level of thoroughness. For instance, a fast, relatively nonthorough search of high-probability areas is called a hasty search. This type of search would be conducted at camp sites, buildings, and other very likely locations where the subject might be found. Loose grid techniques—widely spaced searches of large areas—can be applied when relatively rapid searches of large areas are desired. When using these techniques, thoroughness is greater than with hasty searches, but less than with other slower, more resource-intensive techniques. Loose grid techniques allow some level of effort to be applied to large areas fairly quickly. Alternately, tight grid techniques—slow, highly systematic area searches—are applied only when the absolute highest level of thoroughness is required. Unfortunately, this is almost always at the expense of time and resources. In short, the greater the thoroughness, the more resource intensive and time consuming the technique.

Clues and Their Value Clues are discovered during the investigative and tactical phases of a search. Their importance cannot be overemphasized. They

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may take the form of physical evidence, such as a footprint or discarded item, account by a witness, or information gleaned from the investigation. Clues serve as the rudder that steers the overall search operation. Relevant clues are the basis for all search strategies and can determine or modify nearly all operational actions. Their powerful influence should be obvious; this is why searchers are taught to be “clue conscious” and to seek clues, not just subjects. There are many more clues than there are subjects. People generate clues. A person exudes scent in the form of dead skin cells, crushes or disturbs vegetation, and, when traveling, leaves marks on the ground or other physical evidence of passing. This evidence is often discoverable if the appropriate resource is applied in a coordinated, organized search effort. Searchers must be sophisticated enough to discover this evidence and interpret its meaning before it is destroyed or decays. Because evidence important to a search effort is often easily destroyed once it is discovered, it is important to protect it from damage until it is completely analyzed.

Search Resources Resources are defined as all personnel and equipment available, or potentially available, for assignment to support the search effort. Specific types of active tactics are categorized by the resource that performs them, such as dog teams, human trackers, ground search teams, and aircraft. Other common resources include management teams (e.g., overhead teams, public information officers), water-trained responders (e.g., river rescue, divers), cold weather responders (e.g., ice climbers, avalanche experts, ski patrollers), specialized vehicle responders (e.g., snowmobiles, four-wheel-drive trucks, all-terrain vehicles, mountain bikes, horses), and technical experts (e.g., communications experts, interviewers, chemists, rock climbers, physicians, cavers). In addition to these, other less common resources might also be available. These could include attraction devices (such as horns, flags, lights, sirens), mine detectors (military), noise-sensitive equipment (super microphones), infrared devices (forward-looking infrared [FLIR] on aircraft, night-vision equipment, thermal imagers), thermistors, and even witches, seers, prophets, and diviners. Just about any person or thing imaginable may be available for use in a SAR incident. Their use is limited only by the creativity of those in charge. Here we discuss a few of the most common and useful.

Dogs. Dog teams are a common type of active search resource in the wilderness and are composed of a dog (occasionally more than one) and a human handler. The dog uses scent to search for and follow a subject while the handler interprets signals from the dog and searches visually for evidence. Three common categories into which dogs fit are tracking, trailing, and airscenting. Tracking dogs follow scent on the ground from a person’s footsteps and usually very closely follow the trail where a person traveled, regardless of the wind. Trailing dogs follow scent that has fallen onto the ground from the subject along the route of travel. Unlike the tracking dog, the trailing dog may follow the scent at some distance from the actual tracks of the subject, and may therefore be more affected by wind. Tracking and trailing dogs are most effective when used in areas that have not been contaminated by humans other than the subject. Also, weather and time tend to destroy scent available to these types

Search Urgency Remember: the lower the number, the more urgent the response!!! A.

Date Completed: Time Completed: Initials:

SUBJECT PROFILE Age Very Young Very Old Other Medical Condition Known or suspected injury or illness Healthy Known fatality Number of Subjects One alone More than one (unless separation suspected)

B.

1 1-2 2 3

1 1-2 3

SUBJECT EXPERIENCE PROFILE Not experienced, not familiar with the area Not experienced, knows the area Experienced, not familiar with the area Experienced, knows the area

E.

1 2-3

EQUIPMENT PROFILE Inadequate for environment Questionable for environment Adequate for environment

D.

1-2 3 3

WEATHER PROFILE Existing hazardous weather Predicted hazardous weather (8 hours or less) Predicted hazardous weather (more than 8 hours) No hazardous weather predicted

C.

1 1 2-3

1 1-2 2 3

TERRAIN AND HAZARDS PROFILE Known hazardous terrain or other hazards Few or no hazards

1 2-3

TOTAL

If any of the seven categories above are rated as a one (1), regardless of the total, the search could require an emergency response.

•••THE TOTAL SHOULD RANGE FROM 7 TO 21 WITH 7 BEING THE MOST URGENT.••• 8-11 Emergency Respone

12-16 Measured Response

17-21 Evaluate and Investigate

Figure 32-3. Urgency Determination Form. (From Cooper DC [ed]: FUNSAR: Fundamentals of Search and Rescue. Chantilly,VA, Jones & Bartlett, 2005.)

Chapter 32: Search and Rescue of dogs, so the earlier they are used in a search, the better their chances of finding something. Air-scenting dogs work off-lead to follow a subject’s scent to its source. Specifically bred and trained air-scenting dogs can even discriminate between individual humans. They may detect scent from articles of clothing and can often follow it to discover a person buried in rubble or snow or even submerged under water. Wind is very important to this type of dog, as are other environmental forces, such as sun and rain. But as long as the source exists, an air-scenting dog can usually detect the scent carried in air currents and follow it to the source.

Human Trackers. Human trackers use their visual senses to search for evidence left by a person’s passing. Human trackers “cut” or look for “sign” or discoverable evidence by examining the area where the subject probably would have passed. This process of looking for the first piece of evidence from which to track is called “sign cutting.” Following the subsequent chain or chronology of sign is called “tracking.”9 In SAR, most trackers use a stride-based approach called the step-by-step method. This simple, methodical approach emphasizes finding every piece of possible evidence left by a subject. However, its most important role is undoubtedly the ability to quickly determine the direction of travel of the subject and thus limit the search area. Ground Search Teams Hasty Teams. A hasty team is an initial response team of welltrained, self-sufficient, highly mobile searchers whose primary responsibility is to check out the areas most likely to produce the subject or clues first (e.g., trails, roads, road heads, campsites, lakes, clearings). Their efficiency and usefulness are based on how quickly they can respond and the accuracy of initial information. Ideally, hasty teams should include two or three individuals who are knowledgeable about tracking. They should be clue oriented, familiar with the local terrain and dangers in the area, and completely self-sufficient. Also necessary are the ability to skillfully interview witnesses and to use navigational skills with pinpoint accuracy. Team members should at least be trained in advanced first aid. Hasty teams usually operate under standard operating procedures, so they do not have to wait for specific instructions. They carry all the equipment they might need to help themselves and the lost subject for at least 24 hours. Grid Teams. Grid searchers use a more systematic approach to searching. They usually examine a well-defined, usually small segment to discover evidence. The classic approach to grid searching involves several individuals (almost always too many) standing in a line, shoulder to shoulder, walking through an area in search of either evidence or subjects. The distance between searchers can be varied to change thoroughness and efficiency (wide spacing is less thorough and more efficient). However, such resource-intensive approaches to searching are generally less preferred than those that use fewer personnel in a more efficient manner (such as tracking, dogs, or aircraft). In addition, close-spaced grid searching tends to damage evidence and is generally difficult to coordinate. Although grid searching may be an acceptable approach in certain limited circumstances, experience has shown that when the subject of a search is a person, searching in this thorough

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manner should be used only as a last resort. Experiments involving grid searching have suggested that it is better to place searchers farther apart. This is usually a more efficient use of resources.

Aircraft. Aircraft serve the same purpose as grid searchers, only from a greater distance, at a greater speed, over a larger area, and usually with a lower level of thoroughness. Within a search effort, aircraft can serve both as a tactical tool to look for clues and as transportation for personnel and equipment. They also provide an excellent attraction device for the missing subject as well as witnesses who may have information about the incident. Both fixed- and rotor-wing aircraft have their place in SAR and, like other resources, have their advantages and limitations. Among the most obvious limitations are the expense and complex use requirements. Aircraft not only require specialized personnel and cost a great deal to operate, they also have very strict weather and environmental restrictions. For instance, it would be difficult to search from an aircraft in a snowstorm, and terrain may prevent searching certain areas from the air. However, most of these difficulties can be adequately addressed and minimized in a well-developed preplan.

Search Planning Considerations State-of-the-art searching for lost persons has come a long way from the familiar lining up of volunteers shoulder to shoulder and walking in a straight line to search an area. Many new lifesaving concepts have been developed by the national SAR community. By borrowing from psychology, mathematics, business, and the analysis of past incidents, search planning and management have evolved into sophisticated sciences. Search effectiveness has also been improved through the study of human behavior, statistics, probabilities, leadership, and the use of good planning and management principles (Fig. 32-4). Search planning is guided by two general considerations: where am I going to look for the lost or missing person (strategy), and how am I going to find this missing or lost person (tactics)? To be effective, modern searchers follow several basic principles and techniques that include the following:

Figure 32-4. Map used to brief ground team. (Photo courtesy of D. Maynard.)

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1. Respond urgently—a search is an emergency. 2. Confine the search area. 3. Search for clues. 4. Search at night. 5. Search with a plan and in an organized manner. 6. Grid search (tight grid) as a last resort. Every day, emergency responders receive calls to perform their duties, and they never know what to expect once they arrive. Life-threatening or time-critical situations have engendered what is known today as the “firehouse response.” This means that emergency responders have to assume the worst until proved otherwise. They respond with “lights and siren” to most calls just in case the situation is serious. Unfortunately, people who report incidents are often wrong in their initial assessments, and because of this, every call must get the same urgent response. Essentially, the situation is considered an emergency until proved otherwise. For years, searching has been considered less urgent than other emergencies. Although responders were running with lights and sirens to situations reported as “women not feeling well” or “dumpster on fire,” reports of a missing/lost child or an overdue hiker were relegated to the “let’s wait and see” category. Through years of experience, search managers now know that a search is as much an emergency as any other call for help. Experience also indicates that an urgent response to a search situation often leads to a faster resolution with less impact on family, and to the expenditure of much less effort overall. Any search situation for a lost or missing person should be considered an emergency that justifies an urgent response, high priority, thorough assessment, and immediate action.

Search Theory. The mathematical basis for searching and study of search theory had its beginnings during World War II in the work of the U.S. Navy’s Anti-Submarine Warfare Operations Research Group (ASWORG) and was originally based on searching for the wakes of warships as seen by aircraft flying over the ocean.10 The results of this work were collected in a seminal report by B. O. Koopman in 1946,22 but the report was not declassified and generally available until 1958.2 In 1980, Koopman developed a somewhat expanded version of this work.23 Although Koopman’s work is clearly aimed at naval interests, the general theory of search he established is applicable to virtually any type of search problem. Since this early work, search theory has undergone continuous research and development by agencies such as the USCG and U.S. Navy in both the maritime and aeronautical environments, mining and oil businesses in search of mineral and petroleum deposits,13 and even archeologists in search of lost cities, such as Troy.33 The fundamental usefulness of search theory lies in its ability to help determine where and how to search. It accomplishes this by (1) quantifying the likelihood of a missing subject being in a particular area, as well as the likelihood of searchers finding the subject; and (2) offering tools with which one can estimate the chances of success of a particular search. The application of search theory requires the appropriate use of probability theory, a branch of mathematics that is used for estimating the likelihood of uncertain events, in planning a search. The chance that the missing person is in the search area is called probability of area (POA). The probability that a search resource will find the missing person or clue if it indeed is in the area being searched is called probability of detection (POD). The product of these two important variables produces a result

called probability of success (POS = POA × POD).33 The foremost objective and major challenge for search planners is to deploy the most capable search resources (POD) into segments in which the subject is most likely to be (POA) to produce the most POS in the least amount of time. On the surface this seems to be a straightforward proposition. However, myriad critical factors, such as resource detection capability, environmental influences, search object characteristics, probability density, probability distribution, coverage, and sweep width, conspire to make the most correct search action a complex, unintuitive series of difficult choices. Several initiatives have been undertaken to simplify the process of applying search theory to land search, including standardizing terms6 and developing simplified, yet mathematically correct, approaches to quantifying the variables in less subjective ways.7 Advanced methods have also been developed to optimize the increase in POS over time3,34 and integrate motion and other models into land search problems.42 However, user-friendly computer software will be required for such advances to enjoy widespread use by land search planners. During the past several years, much has been done to improve how scientific search theory is applied to land search. Before 2001, much more research on the topic of search and detection had been conducted in the maritime environment than on land. In 2001, the NSARC Research and Development Working Group convened a meeting of land search experts.30 After this meeting, several research projects sponsored by NSARC, and supported by several national and international organizations, were developed and funded. The first project produced a model for conducting detection experiments on land.32 In 2004, using the model developed, five detection experiments were conducted across the United States in five different ecoregions.1,21 The results should provide tremendous insight into methods of quantifying visual detection on land. In 2004, NSARC, with funding from the Departments of Defense and Homeland Security, published a report that compared published land search procedures with the science of search theory. The full report identified several significant opportunities for improvement in multiple, long-practiced land search procedures and concepts.8 Several of these reports are available on the NSARC website at www.uscg.mil. Although software is available to assist in the mathematical decisions, less than optimum but historically acceptable results have been achieved when a search planner applies the principles of search theory as an intuitive combination of hard science and sage experience. In the final analysis, search success is based on more than just science. At its finest, it involves the artistic application of science and a high degree of organizational and management skill, sprinkled with intuition and punctuated with a bit of luck.

Lost Subject Behavior. Modern search management is also based on the use of what is called a complete “subject profile.” Such a profile identifies as much as is known about the missing subject, including general state of health, past experiences, and state of mind, through the use of a form called the Missing Person Questionnaire. This information is collected and used by search planners to predict how an individual would react in various situations. Analysis of this information from past incidents and understanding how the involved individuals behaved in given circumstances have offered great insight for search managers.

Chapter 32: Search and Rescue It is important to note that most data on abductions, of both children and adults, have been purposefully excluded from SAR research. Although some important work has been done in this area (e.g., by Hanfland and colleagues12), the study of abductions and related criminal activity is often more about the perpetrator than the subject of the crime. This is in stark contrast to the study of lost subject behavior, for which the actions of the subject are the focus of the research. Although it is not difficult to appreciate the importance of predicting how a subject might react when lost, the scientific approach to the topic began with Syrotuck’s seminal paper in 1977.35 This paper was based on the premise that individuals have similar travel habits when compared with others in the same “category.” The six categories are small children (1 to 6 years), children (6 to 12 years), hunters, hikers, older adults (>65 years), and “miscellaneous adults,” such as nature photographers, fruit gatherers, bird watchers, and other outdoor enthusiasts. There are two “special categories” (mentally retarded persons and despondents), for which there were very little data. In his study, Syrotuck described the behavioral characteristics of a representative member of each category and computed “probability zones” for each, based on distances traveled. This distance was measured “as the crow flies,” or as a straight-line distance, between the point where the subject was last seen and the location where the subject was eventually found. Realizing that there was likely a substantial difference between how far a lost subject actually traveled and the crow’sflight distance, the author argued that, “it is more important to realize that a known percentage of all lost persons are found within a one- or two-mile radius than it is to know how they got there.” Syrotuck studied 229 cases, most from wooded areas of Washington and New York states, and all involved subjects traveling on foot.35 Beyond identifying categories, Syrotuck35 also documented and described six other factors that may affect the search plan. He suggested that search personnel in possession of the follow-

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ing information could more accurately predict the subject’s location: 1. Circumstances under which the person became lost 2. Terrain 3. Personality 4. Weather 5. Physical condition at time of loss 6. Medical problems He went on to describe how one’s general state of health, past experiences, and physical situation (e.g., hot, cold, altitude) contribute to predicting behavior patterns. How one reacts to being lost, he also suggested, can affect the type and quantity of clues (i.e., disrobing, discarding equipment), survivability (i.e., failure to build a fire), detectability (i.e., bright clothing, bad weather), and tendency to follow travel aids such as rivers, roads, and trails. What Syrotuck produced was the first relatively scientific description of how people might react to being lost and how searchers could use this information to improve operations. Following the theme of lost person behavior and using the crow’s-flight distance, Koester and Stooksbury18 performed a retrospective study of persons who suffered from what they termed “dementia of Alzheimer’s type” (DAT) and who became the subjects of organized SAR efforts in Virginia. They studied 82 cases (initially) from the Virginia Department of Emergency Services’ (DES) lost-subject database and compared the DAT patients’ behavior to that of lost older adults who possessed normal cognitive abilities. Their findings were of great interest to search managers and planners in that this was the first time research of this type had been conducted for the inland SAR community. The authors also described a “subject profile summary” and suggested specific search techniques for lost DAT patients. Notable in their findings were the facts that none of the subjects in the cases they studied yelled for help, and they were usually found 0.5 miles (0.8 km) from the PLS. Since this initial research, Koester19,20 has extended his analysis of the Virginia DES data (Tables 32-1 and 32-2).

TABLE 32-1. Summary of Findings for Lost Persons with Alzheimer’s and Related Disorders TYPE OF SUBJECT STATISTIC n Age (standard deviation) Males Females Uninjured Injured Deceased

ALZHEIMER’S

ELDERLY

DESPONDENTS

RETARDATION

PSYCHOTIC

87 76 (9.2) 67% 33% 51% 27% 22%

33 70 (4.3) 67% 33% 48% 15% 37%

65 37 (15.7) 76% 24% 34% 11% 55%

29 30 (3.3) 60% 40% 85% 11% 4%

25 43 (15.9) 63% 37% 72% 5% 22%

2.9/1.8 0.8/0.5 0.8/0.5 0–8.0/0–5.0 0.2/0.124 0.8/0.5 4.0/2.48 7.7 (95%)/4.7

2.2/1.36 5.3/3.29 0.3/0.19 0–32.2/0–20.0 0.2/0.124 0.3/0.19 2.6/1.61 8.0 (96%)/5.0

1.4/0.87 1.9/1.18 0.8/0.5 7.7/4.7 0.2/0.124 0.8/0.5 1.6/1.0 4.0 (95%)/2.48

2.2/1.36 3.7/2.3 0.8/0.5 12.9/8.0 0.2/0.124 0.8/0.5 2.0/1.24 7.7 (92%)/4.7

Distance from Point Last Seen (km/mile) Mean 1.0/0.62 Standard deviation 0.8/0.5 Median 0.8/0.5 Range 0–4.8/0–3.0 25% 0.3/0.19 50% 0.8/0.5 75% 1.1/0.68 Max. zone 2.4 (94%)/1.49

Data from Koester RJ: The lost Alzheimer’s and related disorders search subject: New research and perspectives. Conference Proceedings, RESPONSE ’98, Annual Conference of the National Association for Search and Rescue, Chantilly, VA, June, 1998, NASAR, pp. 165-181; and Koester RJ: Behavioral profiles of lost subjects in Virginia. Retrieved March 10, 2004, from http://www.dbs-sar.com.

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TABLE 32-2. Subject Found Location Data TYPE OF SUBJECT

Structure Yard (open field) Drainage Woods Brush/briars Road Power line/linear Other

ALZHEIMER’S (AND RELATED DISORDERS)

DESPONDENTS

MENTAL RETARDATION

PSYCHOTICS

15% 18% 18% 7% 29% 7% — 4%

8% 4% 8% 33% — — 13% 8% (Cliff bottom)

21% 16% 21% 16% 11% 11% 5%

23% — 7% 30% 7% 23% —

Data from Koester RJ: Conference Proceedings, RESPONSE ’98, Annual Conference of the National Association for Search and Rescue, Chantilly, VA, June, 1998, NASAR, pp. 165-181; and Koester RJ: Retrieved March 10, 2004, from http://www.dbs-sar.com.

TABLE 32-3. Formal Estimates of Crow’s-Flight Distance (in km) Between the Point Last Seen and the Point Found for Persons Lost During Different Wilderness Activities PERCENTILE ACTIVITY GROUP (N) Campers (18) Cross-country skiers: break trail (5) Cross-country skiers: groomed trail (18) Despondents (6) Hikers (38) Hunters (5) Mountain bikers (18) Scramblers (7) Walkaways (14) Other (13)

25

50

75

90

0.722 4.537 0.842 0.229 1.691 1.222 3.759 1.165 0.701 1.765

1.559 9.795 1.819 0.656 3.650 2.638 8.116 2.515 2.007 3.812

3.001 18.860 3.501 1.793 7.028 5.079 15.626 4.843 5.486 7.339

4.931 30.988 5.753 4.664 11.548 8.345 25.675 7.958 14.274 12.058

Note: Estimates for despondents and walkaways were based on a different Wakeby distribution than that used to estimate the percentiles of the other user categories. From Heth DC, Cornell EH: J Environ Psychol 18:223-235, 1998.

Also using the crow’s-flight distance, Hill15 described distances traveled and probability zones for lost persons in Nova Scotia. However, Hill found it useful to modify and add to Syrotuck’s categories of lost persons. For instance, Hill broke young people into four categories: children 1 to 3 years, children 4 to 6 years, children 7 to 12 years, and youths 13 to 15 years of age. He described characteristics for fishermen, skiers, and walkaways (i.e., people who walk away from a constantcare situation), and additional characteristics for those who are despondent. Taking a slightly different approach, Heth and Cornell14 published a study of 162 incidents of persons lost in wilderness areas in southwestern Alberta, Canada. They tabulated crow’sflight distance traveled and angular dispersion of travel (the angle from a line that connects the PLS with the intended destination) by different categories of wilderness users. They formed 10 categories of outdoor user (Table 32-3) and included only subjects propelled by muscle (no machinery). Interestingly,

the authors found a behavioral distinction between “front country” users (i.e., front referring to parking lots, groomed trails, frequent signage, along with good, available maps; these areas attracted users with a large range of outdoor experience and skill) and “backcountry” users (i.e., remote, undeveloped areas; these areas attracted prepared and experienced users). Not unlike Syrotuck and Hill, Heth and Cornell discovered that, with the exception of despondents, there is a similar distribution of distance traveled by persons lost outdoors. However, they went further and suggested that there might be a linear relationship between certain data sets. For instance, their analysis indicated that hikers travel about 2.3 times farther than campers, and cross-country skiers breaking trail travel about 5.4 times farther than cross-country skiers using groomed trails. The implication is that if archival data are possessed for one category in one region and are compared with categories of lost subjects similar to those described by Heth and Cornell, a scalar parameter could be applied to extrapolate crow’s-flight

Chapter 32: Search and Rescue distances for other subject categories. Such a possibility is exciting to search managers, who only rarely have access to relevant and reliable archival data.14 Search planners have used these and other behavioral studies in a number of valuable ways. By direct analysis and limited extrapolation, search planners have been able to find answers to important planning questions that are helpful in determining where and how to search. Such efforts have also taught search managers the importance of collecting behavioral data on lost persons, and the predictive value of such data.

Access Phase After the subject is located, the search is over. Rescuers must now gain access to the subject to assess and treat injuries, evaluate the situation, and mitigate the problem. Accomplishing these objectives may be as simple as walking up a trail to reach the subject or as complex as reaching a climber on the face of El Capitan in Yosemite. Regardless, planning for this eventuality should be complete and ready to be carried out at the conclusion of the locate phase. Once rescuers reach a subject, the situation and scene must be assessed. In emergency services terminology, this is called the size-up. The size-up consists of identifying hazards to the subject and rescuers, then developing a strategy to deal with the problems. For instance, a subject might be trapped by a winter storm in a high alpine environment. Safety considerations for rescuers entering such a hostile and dangerous environment would certainly influence further actions and may well take precedence over the entire rescue effort. Specialized skills may be required for rescuers to safely gain access to the scene. For instance, rescuers may need to rappel to a patient who has fallen onto a ledge in the Grand Canyon, or they may need to climb sheer rock faces to reach an injured mountaineer on Half Dome in Yosemite National Park. These are examples of how complex the access phase of a rescue may be and point to the importance of thorough and proper planning. If the size-up indicates that the situation or environment is so hazardous that remaining on scene poses an immediate threat to the subject, accelerated rescue techniques may be required. Accelerated rescue techniques are immediate actions required to remove a subject from a dangerous environment without stabilization. They often entail deviations from local standard operating procedures and protocols. Examples of such situations include poisonous gas environments (e.g., in caves), fires, unstable terrain (such as avalanches and rock slides), adverse weather (hurricanes, thunderstorms, severe snowstorms), or any hostile environment that threatens the subject, rescuers, or both.

Stabilize Phase The stabilization phase has three primary components: physical, medical, and emotional. Once rescuers have access to the subject, the scene must be quickly evaluated, or sized up, for immediate physical hazards and threats from the environment. Scene safety is an initial priority in the size-up, and risks to everyone must be weighed against the benefits to be gained. An example of physical stabilization would include an occupied automobile teetering on the edge of a cliff. Before the occupant can be medically assessed, the situation (i.e., the automobile) must be stabilized to best protect the rescuers and the patient. Other examples of physical stabilization might include protecting the patient from further injury (e.g., removing him from the

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hazardous environment or applying a helmet) or removing the hazard (e.g., extinguishing the fire, securing the teetering auto). Once the physical environment is stabilized and free from immediate hazards, medical management and stabilization can begin. This process usually follows accepted procedures, starting with primary and secondary physical examinations and progressing through basic and advanced life support. The process should include full-body immobilization, usually in a litter; specific site immobilization of fractures and related injuries; treatment of shock and other hemodynamic compromise; and without exception, some type of protection from the environment. The goal of medical stabilization is usually to prepare the subject for transportation to a definitive care facility. If medical care is not required, confirming this fact may be all that is necessary at this stage before moving into the transport phase. Emotional stabilization is necessary because an anxious victim is a hazard to rescuers and himself or herself. Again, the goal is to best protect both the rescuers and the victim. Simple, calm communication with the patient, slowly describing what happened and what rescuers are doing, is often enough to calm a nervous subject. Stabilization, like assessment, should continue throughout the transport phase. The overall objective is to prepare the victim for transport to definitive care while maintaining his or her comfort and safety.

Transport Phase In the fourth phase of SAR, the subject is moved to definitive care. For this to occur, the stabilized subject must be “packaged” so that he or she can be moved safely and efficiently while stabilization and assessment continue. Transportation will range from foot travel, with the subject walking on his or her own, to evacuation by aircraft. If helicopter extraction is going to be used, the injured person must be briefed thoroughly on what to expect. This should include everything from the effects of the “rotor wash” to movement and noise. The appropriate mode of transportation can be determined by weather, type and severity of injuries, overall urgency, terrain, and available resources, to name just a few. Chapter 34, Litter and Carries, addresses the numerous considerations that exist when a patient will be packaged and transported from an isolated wilderness area to definitive care.

Rescue Equipment Today’s rescues occur in many remote and unusual environments and often require extremely technical rescue equipment and skills. Responders trained in the appropriate techniques and technologies should be the only personnel to apply them. Much of the gear and many of the techniques have been derived from those first developed by mountaineers, climbers, cavers, and, more recently, white-water enthusiasts. Rescue equipment is generally broken down into three broad categories: personal gear, rescue software, and rescue hardware. Personal equipment includes such items as footwear, gloves, helmets, articles of clothing, eye protection, and other protective apparel. Software is equipment such as rope, webbing, slings, and harnesses that are made of soft, strong synthetic materials specifically designed and manufactured for rescue. Hardware includes equipment such as carabiners, cams, friction devices, pulleys, and litters made of steel and alloys specifically designed and manufactured to endure the rigors of rescue.

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Figure 32-5. Even though the personal equipment necessary is dictated by both the rescue environment and the needs of the specific situation, it includes head, hand, foot, and eye protection as a minimum.

Figure 32-7. Example of 1/2-inch, nylon, static, kernmantle rope of the type commonly used in rescue. Rescue rope should be checked over its entire length for damage before use.

Figure 32-6. Rescuer wearing a personal flotation device (PFD) and helmet often used for rescue in and around moving water.

Personal Equipment. Rescuers must often wear special equipment to protect them from accidents and hazards. Head, eye, and hand protection is considered mandatory in virtually all rescue environments. Additional personal equipment requirements are dictated by the rescue environment and the specific needs of the situation (Fig. 32-5). Special Gear. In addition to the usual challenges of the rescue environment, certain hazards require specialized equipment. Examples of such equipment include fire-resistant clothing worn by structural and wildland firefighters, personal flotation devices (PFDs) used by rescuers in and around water (Fig. 32-6), netting used in outdoor settings when insects become a

problem, bulletproof garments used by law-enforcement and military rescue personnel, and chemical protective suits worn when exposure to hazardous materials is possible. No clothing or protective gear meets all of the requirements for involvement in or around a rescue scene. Rescuers study situations so that they understand all hazards before anyone becomes involved. Their conclusions help them identify protective equipment requirements. Gear that may be necessary for one environment can be dangerous in another. A firefighter’s turnout gear may be required in a structure fire but can be deadly in a river rescue situation. Every rescuer is responsible for understanding the rescue environment and how to best prepare for it.

Software Rope. Rope is by far the most versatile piece of rescue equipment and serves as the universal link in most rescue environments. The material from which the rope is made (e.g., nylon, polyester, or polyolefin) and the design (laid, kernmantle, flat) are important in the consideration of the use for which a rope is intended. In most rescue environments, nylon is preferred because of its overall strength, resistance to abrasion, and ability to stretch and absorb energy. Natural fiber ropes such as hemp are no longer considered for use in rescue; synthetic materials are far better. Although design and amount of materials used influence strength, new 1/2-inch diameter nylon rescue rope usually has a tensile strength in excess of 9000 pounds (40 kN) (Fig. 32-7).

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Figure 32-8. Left, Tubular webbing with cross section visible. Right, Flat webbing used in anchor sling.

The most common design of rescue rope is kernmantle, a term derived from German, meaning “core in sheath.” With this design, a core of material (often parallel fibers) is surrounded by a braided sheath. The sheath protects the inner core, which supplies much of the strength of the overall rope. Other designs, such as laid (twisted) and braided, are also used in rescue rope. Kernmantle rope is either dynamic or static. Dynamic kernmantle stretches more than 4% of its length to absorb the impact of a fall, and it is used primarily in lead climbing. Static kernmantle stretches less (no more than 4% of its length); it is used in rescues in which a great deal of stretch would be a nuisance or even dangerous. Because of the importance of rope in the rescue chain, frequent inspection, care, and maintenance are important. Rope used in rescue is kept clean, inspected often, and protected from sharp edges, high temperatures, sunlight, chemicals, and abrasion. In addition, a detailed history of rescue ropes is kept so that an educated decision can eventually be made regarding each rope’s removal from rescue service (see Chapter 84).

Webbing. Flat rope or webbing is another common link in rescue systems. It comes in two common configurations: flat and tubular. Tubular webbing is manufactured as a tube in such a way as to seem flat when in use. In cross section, however, it is obviously tubular and a bit less stiff than true flat webbing. One-inch diameter tubular webbing can be used in rescues to tie anchor slings and harnesses. It has a tensile strength of about 4000 pounds (17.8 kN) when new. Flat webbing is flat in cross section. Its strength is directly proportional to the amount of material used in its manufacture. Automobile seat belts are an example of the material used in rescue harnesses and anchor slings, and where strong, flat software is beneficial (Fig. 32-8). Harnesses. Harnesses come in many sizes and shapes; they are used to attach something (usually a rope) to a person’s body. They may be “full body,” encompassing the thorax and the pelvis (Fig. 32-9); “seat,” encompassing only the pelvis (see Fig. 32-5); or “chest,” encompassing only the thorax. Each type of harness has its use and associated advantages and disadvan-

Figure 32-9. An example of a full-body harness. Shown is a CMC ProSeries Harness Combo. Note that this harness encompasses both the pelvis and the thorax. (Photo © CMC Rescue.)

tages. Classically, the most common harness for climbing has been the seat harness. However, rescue practitioners have been trying to standardize the full-body harness for rescuer use, with the separate seat and chest harnesses having only limited special use by trained individuals. Webbing can be tied into a large loop (runner) and applied to a person in such a way as to serve as an improvised harness. Although this is not a preferred method of attachment to a rope, it can work if other harnesses are not available.

Hardware Carabiners. Carabiners are large, safety pin–type mechanisms used to connect various elements of a rescue system, such as a rope and anchor. They are occasionally called “biners,” “snap links,” or “crabs” and consist of a spring-loaded gate that pivots open, a spine that supports most of the load and lies opposite the gate, a latch, and depending on the specific style, a locking mechanism. Carabiners are most commonly made from either steel or aluminum. Size for size, steel is stronger and heavier, but aluminum is lighter and stronger pound for pound. In rescue, steel is almost always preferred unless weight is a factor, as it is in remote alpine situations. Common shapes of carabiners include oval, D, offset D, pear, and large offset D. The design best suited for any situation is dictated by the specific use. No matter what the shape, carabiners used in rescue usually have a mechanism for locking the gate closed so that opening it takes a specific effort. This design feature not only improves the strength of the device but also reduces the chances that a carabiner will open accidentally at an unexpected time (Figs. 32-10 and 32-11).

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Figure 32-10. Various types of carabiners.Top to bottom:(1) RSI Big hook, steel, screw locking hinged gate; (2) alloy, offset D, screw locking hinged gate; (3) RSI Twist Link, steel, screw locking hinged gate; (4) SMC extra large, rescue, steel, screw locking hinged gate; (5) Tri-link, steel, triangular, screw lock; (6) Auto-lock, swivel-mount, steel, quarter twist locking hinged gate (NFPA 1983 certified). Note that locking carabiners should always be locked when in use.

Descending (Friction) Devices. Many different descending devices exist today, but they all do primarily the same thing: apply friction to the rope to allow controlled lowering of a person or load. The most common descending devices in rescue are the figure-8 plate and the brake bar rack. The figure-8 plate gets the name from its general shape. It has two rings of different sizes. The larger ring produces friction on the rope, whereas the smaller ring is used primarily as an attachment for the load (e.g., the rescuer during rappel). Friction is produced by passing a bight of rope through the large ring and around the small ring, then attaching the small ring to either an anchor (for a lowering system) or a rescuer’s harness (for a rappel or abseil) with a locking carabiner (Fig. 32-12). The brake bar rack, or simply “the rack,” uses either steel or aluminum bars on a steel rack to produce friction on a rope. When the rope is threaded alternately around the bars and the load or rescuer is attached to the “eye” in the rack, friction is applied. The number of bars applied to the rope and the distance between them can be varied to change the friction. This variable friction allows versatility not available with the figure8 plate; however, the rack takes a bit more training to use safely (Figs. 32-13 and 32-14). Ascenders. Ascenders are devices that grip or hold the rope. They have been adapted from climbing and caving equipment, with which they are used to ascend or climb a fixed rope. In

Figure 32-11. Close-up view of CMC Rescue aluminum carabiner. Note the locking gate and offset D shape. (Photo © CMC Rescue.)

rescue, they are used to climb fixed lines when necessary, but they can also be used in hauling systems to grip the rope. In this way, they hold fast when the rope is pulled in one direction and allow the rope to slide easily when it is pulled in the other direction (Figs. 32-15A–D and 32-16). When ascenders are used to climb a rope, one is fixed to the rope and supports the load while the other is moved into position ahead. When this action is alternately repeated, a skilled climber can move up a rope with relative speed and ease. Selected rope hitches (e.g., a Prusik hitch) can be used in lieu of an ascender (see Fig. 32-15D).

Pulleys. Pulleys are simple machines that apply a turning wheel to reduce friction on a rope as it rounds a turn. In rescue, these metal devices serve primarily to change the direction of a rope, such as within a mechanical advantage system. The “sheave” is the wheel or pulley, and there may be more than one. The “side plate” or “cheek” is the side of the device that makes contact with the anchor at the “hook,” which is usually the weakest part. The axle or “sheave pin” is what the wheel turns on; it is supported by the side plates. In rescue pulleys, the side plates are movable so that the pulley can be attached to a rope anywhere along its length (Fig. 32-17). The larger the diameter of the pulley, the more efficient the device. That is, the bigger the pulley, the more friction (theoretically) is reduced. A rule of thumb often used by rescuers is

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Figure 32-14. SMC NFPA Brake Bar Rack. Straight frame shown; frame also available with eye twisted 90 degrees.The top bar has been modified to allow for a secure tie-off. (Photo © CMC Rescue.) Figure 32-12. Example of figure-8 plate descending device (with “ears”) commonly used in rescue. Shown is a CMC Rescue 8 with Ears; aluminum (left) and steel (right). (Photo © CMC Rescue.)

that a pulley with the largest diameter possible should be used, but never less than four times the diameter of the rope. Therefore, because 1/2-inch (11 mm) rope is commonly used in rescue, a pulley diameter of at least 2 inches should be used. A variation of the pulley is the edge roller. This device uses 4- to 6-inch open-face pulleys to reduce both the friction of a rope passing over an edge and any damage to the rope by protecting it from excess abrasion. Single units can protect the rope from 90-degree angles, and multiple units tied together can provide protection for complex projections.

Figure 32-13. RSI Super Rack brake bar rack in use.

Litters. Litters or stretchers are the conveyances in which victims are transported when they cannot travel under their own power. New high-technology materials and designs have greatly improved the choices available. In past years, rescuers were forced to choose between wooden backboards, old military stretchers, the wire Navy Stokes basket, or the “scoop” stretcher. Today, strong, lightweight synthetic materials and inventive designs have improved the strength, weight, durability, and comfort of litters. The goals have not changed during evolution of the perfect wilderness transportation device. Rescuers still want a device that is comfortable for a person in pain, serves well as a platform for assessment and medical care during transport, allows for full-body immobilization, and provides complete security and protection of the occupant from the rescue environment. See Chapter 34 for additional information regarding specific litters, packaging, handling, and evacuation techniques.

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A

B

C

D

Figure 32-15. A, Gibbs ascender applied to rope.When the eye of the cam is pulled, the cam squeezes the rope and holds fast.When the cam is released, the device can be moved on the rope. B, Gibbs ascender dismantled with shell around rope. Note cam (upper left) and pin (bottom). C, Clog handled ascender. Although used where climbing a fixed rope is required, handled ascenders are rarely used in rescue. D, A 3-wrap Prusik hitch can often be used in lieu of a mechanical ascender.


ANATOMY OF A SEARCH AND RESCUE INCIDENT

To summarize how all of the previously discussed information fits together, it is convenient to dissect a SAR incident into its component parts and then analyze how all of the parts fit together (Fig. 32-18). From the SAR operative’s perspective, an actual callout is merely an interruption of planning for an incident. That is, people involved in SAR are constantly in a state of readiness and are prepared to respond. When a situation occurs, this constant planning stage is suddenly interrupted by the report of an incident. The individual taking the information is charged with

conveying it to the appropriate authority. The authority determines the urgency, continues the investigation process, begins to develop an operational strategy, and generates an incident action plan. At the same time, those in charge begin to muster appropriate resources to carry out the action plan. In SAR, this is termed resource callout, or just callout. Once notified of an incident, individual resources are gathered at a collection point and signed in. The sign-in process enhances safety and allows tracking of the types and quantity of resources that are available on-scene. Once signed in, resources are given assignments designed to meet the goals of the action plan within a specific operational time frame. This physical implementation of the incident action plan is referred to as tactics.

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Figure 32-17. Two types of pulleys commonly used for rescue. Top, 2-inch double pulley. Bottom, 2-inch,“Prusik-minding.”Note that rescue pulleys are applied to rope by removing the carabiner and swiveling the side plate to allow the introduction of the rope.

Figure 32-16. Alternate type of cam ascender specifically designed for rescue.Shown is a Petzl Rescucender for use with 7/16 or 1/2-inch rope. (Photo © CMC Rescue.)

Deployment of resources to the field continues until there is reason to suspend this phase of the operation. If the subject is found, the search is suspended, and the access phase can commence. Once rescuers have access to the subject, the focus turns to stabilization and transportation. If at any point the operation cannot be continued (e.g., the subject was never found, access cannot be gained, transportation is impossible), suspension and demobilization may occur without completion of the entire cycle. The decision to discontinue active search efforts is difficult and involves complex management issues, almost always of the “no-win” variety. When a situation is resolved, mission suspension and demobilization begin. In larger incidents, this may involve structured deactivation of multiple resources, pulling teams out of the field, dismantling facilities, completing documentation, and returning resources to service. Basically, everyone finishes what he or she was doing at this incident and gets ready to do it again. All of this takes planning and preparation and should be addressed in the overall preplan long before it is required. After every incident, participants realize that if they had it all to do again, they would do some things differently. If these thoughts and ideas are not documented, they can be lost, and future responses may be cursed to repeat past mistakes. This is one reason that every incident should contain some type of evaluation of the entire mission, known as the postincident critique. The critique can be formal, involving every participant at a sit-down meeting, or informal, involving just a brief discussion of recent events. The critique documents lessons learned and

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Mission critique

Incident Check-in

Debriefing

Mission suspension

Resource callout

Assignment

* First notice of incident

Briefing

Check-out

Return to service

Preparedness and training

Figure 32-18. Time progression or the “anatomy” of a search from a searcher’s (operational) perspective.The process is actually a continuous cycle that pauses in the planning and preparation phase until an incident occurs.

should provide a basis for revising the preplan. Thus the cycle continues, and lessons learned from one mission influence the next.


SEARCH AND RESCUE

ENVIRONMENTS WITHIN THE WILDERNESS SETTING

SAR teams throughout the world are frequently called on to solve complex problems in a wide spectrum of environments. Even within the environments addressed in this text, widely diversified subenvironments exist that present unique sets of problems and hazards to SAR personnel. When confronted with the numerous and dangerous environmental conditions found in the wilderness setting, SAR personnel must be prepared to work where others have been unable to cope. An old military motto becomes the SAR credo: “Adapt, improvise, overcome.” It is beyond the scope of this text to discuss in detail how SAR personnel adapt to each of these environments, but it is important to note that adaptation and improvisation are required in nearly all wilderness situations. The particular improvisation depends on the situation, as well as the skill and experience of the individuals involved. Regardless of the type of rescue environment encountered by rescuers, the following general rules should be followed: 1. Use technical personnel for technical rescue. 2. If a missing person is found dead, evacuate only when there is no risk to team members, or at least when the hazard has been assessed and the risk justified. 3. Stabilize any injured person before evacuating and continue stabilization during transport. 4. Find and use the easiest route for evacuation. 5. If a carry-out is required, appoint someone to serve as route finder who has a radio and markers to report potential hazards and problems. 6. Litter teams of six to eight persons per team should be used, with three teams minimum. Normally, there should be no

more than 20 minutes per shift. Additional personnel may also be required to carry equipment. 7. Use accepted procedures to care for and protect the victim. 8. A radio carrier brings up the rear. 9. If using a helicopter for evacuation, make sure: a. That the patient is thoroughly briefed. b. That the patient is protected. c. That someone goes with the patient who knows what has been done medically. In some cases, because of agency or military service protocols, assisting medical personnel will not be allowed to go with the patient. In these cases, it is imperative that a written log specifying assessment and treatment up to that point accompany the patient.

Special Environments in Search and Rescue Specialized SAR environments produce diverse problems and potential complications. Each environment presents its own obstacles to increase the complexity and difficulty of particular rescues.

Technical Rock Mountaineering, rock climbing, and casual scrambling have created a need for specialized SAR expertise. Individuals and groups involved in rock rescue have refined and developed techniques for most situations. The hallmark of a technical rock rescuer is the ability to improvise and modify tools or techniques to meet any crisis. He or she must be comfortable using climbing gear and being exposed to heights. Once an individual is located in a rock environment and the situation is surveyed, access to the site is the next step. Often, local groups familiar with well-known areas will have already solved this problem. The solution will involve either climbing up or dropping down to the victim. Because any accident during a rescue is almost always catastrophic, safety for all persons involved is of paramount importance. Ascent up rock always requires knowledge of rock-climbing techniques, proper equipment, and familiarity with its designed use and limitations. Local outing clubs or mountaineering stores can be contacted for more detailed assistance. Specialized technical rock rescue

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teams, such as those sanctioned by the Mountain Rescue Association, routinely practice climbing techniques and solving vertical rescue problems.

Caves and Mines Standard obstacles in this environment include poor communications, extreme darkness, difficulty in lighting, small and wet spaces, and often the issue of questionable atmosphere. The various environments included here are collectively termed confined spaces. The levels of moisture in water-containing, or “live,” caves can vary over a considerable range. Some are merely muddy; others have flowing rivers. Caves in the western United States are generally drier than eastern caves; however, humidity, wetness, and cold temperatures create potential for hypothermia in both areas. This is a fact that is greatly underestimated. Flooding can be a lethal problem, and many cavers have died because of inattention to the weather on the outside. During heavy rains, the caves become natural drains for streams. Wind and temperature are other underestimated problems associated with cave and mine emergencies. It is not unusual for strong winds to develop along subterranean passages, which intensifies convective air chilling. Confined passages, low crawls, and squeezes pose unique problems for the rescue of injured cavers. The use of standard items, such as litters, backboards, and splints, may be impossible in such places. Confined passages with varying, or even toxic, constituent gases can lead to difficulties for victims and rescuers alike. Occasionally, a self-contained breathing apparatus or surface-supplied air is required. The potential for toxic gases justifies extensive atmospheric monitoring while operating in the underground environment. An essential part of any cave or mine rescue operation is thorough orientation to the hazards associated with a particular underground area. This involves pinpointing the locations of pits, waterfalls, siphons, canyons, and other difficult formations that may pose problems in extrication, search, or safety. Many caves have been mapped by the National Speleological Society and the National Park Service. The real difficulties may begin only after a victim is located. The goal is to move the person rapidly, safely, and comfortably to the surface. Without practice underground, that task will be virtually impossible. Neoprene exposure bags similar to body bags have been used for this purpose and can keep an injured person dry and protected during what may be a very long and slow evacuation. Medical care procedures must be performed under dark, cold, and muddy conditions. Experienced cave rescuers agree that repackaging supplies and equipment for underground use is essential. Streamlining kits, packs, and containers is imperative for unobstructed passage through tight spaces in cold, damp conditions. Team members must carry very specialized equipment, often including a minimum of 24 hours of light in a helmet-mounted lamp; two additional sources of light, with spare bulbs and batteries; and waterproof matches and candles. Depending on the situation, other equipment is also required and is discussed in Chapter 40, Caving and Cave Rescue. Essential caving skills include all of the capabilities for rock climbing, including vertical rope technique, ascending, rappelling, belaying, and being comfortable working at the end of a rope. All these skills must be practiced until they can be done

Figure 32-19. Common personal river rescue equipment. In the CMC Water Rescue Package shown (clockwise from upper left) is a gear bag, type III/IV personal flotation device, emergency strobe light, glow-in-the-dark Fox 40 whistle, McNett Satur knife, NRS neoprene paddler’s gloves, Cascade Swiftwater helmet, and a CMC ProSeries EZ-Stuf throwline bag. (Photo © CMC Rescue.)

in the cold and wet without the benefit of light. Team practices are conducted both on the surface and underground, with participants being forced to work in mud, suffocatingly tight squeezes, soaking waterfalls, and complete darkness. This may be a difficult evolution for even the most experienced rescuer to endure, but just another “hang in the hole” for a seasoned caver.

White-Water River There are dozens of potentially dangerous problems in the river SAR (white-water) situation (see Chapter 39). Log and debris piles at various bends in the river can function as “strainers” for the recreational victim, but they may be death traps for the would-be rescuer. The banks of the stream may be deeply undercut, with treacherous overhanging debris and snags that can catch on clothing, equipment, and skin. Combined with muddy and rapidly rising water, these factors render river rescue difficult and very unpredictable. In fast-moving water, the single greatest problem is that responders underestimate the power and threat of moving water. Foolhardy heroics and excessive enthusiasm frequently lead to further tragedy. Cold-water immersion, coupled with wind and cold temperatures, predisposes everyone to hypothermia. Wet clothing, darkness, and injury add to the insult. The noise of moving water may obviate clear communications, and result in poor contact between the victim and rescuers. These same factors could also affect communications between rescuers and lead to additional confusion and danger. All potential responders in this environment must be properly equipped (Fig. 32-19) and know how to read the water for capsize points and other dangerous phenomena. The hydraulics of low-head dams, collapsed bridges, and other submerged structures can produce a drowning machine for unsuspecting individuals. Rescue team members must know how to protect themselves in fast-moving water at all times. Mandatory in this environment are good judgment, strong swimming ability, knowledge of all types of technical systems, equipment used in

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A

B

Figure 32-20. Runout. A, This phenomenon begins with an offshore sandbar. As waves roll in, the water level builds up behind the bar until a section gives way. B, As the sandbar “dam” gives way, the water develops a very rapid current running seaward.The recommended action is to swim across the current until out of the pull.

climbing, and a thorough understanding of river dynamics and hydraulic influences.

White-Water Surf Like river white-water, ocean surf can present some very different problems in rescue because there is no “average” beach. There are recurring rescue situations that pose unique problems in the white-water surf environment. Along with the potential for immersion hypothermia, lacerations and contusions can result from being dashed against barnacle-encrusted rocks in the wild and unpredictable ocean surf. Contact with venomous sea life is always a possibility. However, the greatest threat to ocean beach users is the action of the water itself and the possibility of drowning through inattention or unfamiliarity with ocean surf hazards in the form of runouts, undertows, and rips.

Runout. A runout occurs when an offshore sandbar or ledge is built up over a long period. Millions of tons of water flow over the bar during daily tidal changes. Eventually, the water may equal or exceed the level outside the bar. Any weak spot in the bar usually gives way, causing a funnel effect (Fig. 32-20). Water rushes toward the bar at a terrific rate, sweeping everything with it. This common phenomenon can be easily spotted from the beach. Usually 15 to 50 yards wide (14 to 46 m), it is characterized by choppy, jumbled-up, little waves. The water often has a dirty, foamy, or debris-laden surface moving seaward. If a bar is visible offshore, definite breaks can be seen where the water pours through. Surfers often seek runout currents for fast transportation out beyond shoreline waves. Swimmers caught in a runout have two options. They may swim parallel to the shoreline out of the strip of current, or if the bar is visible (usually characterized by breaking waves), they may relax and let the current complete its runout. About 25 yards (23 m) beyond the bar, the current dissipates. This is an offshore phenomenon—current force increases near the bar but is often negligible near shore. Rip. A far worse problem close to the beach is a rip, which can knock children and even adults off their feet and carry them to deep water in seconds. Rips are caused by a slight depression on the beach where wave water rushes after breaking on shore.

Figure 32-21. Figure rip. A depression in the beach floor concentrates returning water into a strong current.To escape, a person should ride with the current or swim to the side and out of the pull.

Water rushing to the depression soon becomes an irresistible seaward flow (Fig. 32-21). It may be as narrow as 15 yards (14 m) at its source and usually does not travel as far as a runout. Rips generally dissipate a few yards beyond the breakers. A rip looks like a runout, with a streak of turbulent discolored water or a line of foam leading directly out from shore. A swimmer has the same options as in a runout, either to swim parallel to the beach or to relax and ride the current until it ebbs. A person who swims straight toward the beach will never make it. A beach with several rips moving up and down in unpredictable patterns is very dangerous. An unwary swimmer could panic and drown.

Undertow. On narrow, steep beaches, a type of current known as undertow can be found. It is caused by gravity acting on water thrown up on the beach by wave action. Water retreating back down the steep shore continues under oncoming waves (Fig. 32-22). Undertow is usually of very short duration and is ended by the next breaking wave. Wading near shore on a steep beach, an individual could be pulled under in this current and find himself or herself quickly in deep water. If the person resists the current, the next wave may break directly on the person’s back. In some circumstances, this could cause traumatic injury, especially to the neck and back. A person caught in an undertow should let the current pull until it ceases, then swim to the surface and ride the next wave into shore.

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Cold, Snow, and Ice

Figure 32-22. Undertow. This hazard develops on a steep beach where the water returns rapidly seaward after being tossed up by the wave action.A person should never fight this action but should relax and rise on the next wave.

Box 32-2. COSPAS-SARSAT Abbreviations COSPAS—cosmicheskaya sistyema poiska avariynich sudov (Russian; in English, “space system for the search of vessels in distress”) ELT—emergency locator transmitter EPIRB—emergency position indicating radio beacon PLB—personal locator beacon. SARSAT—search and rescue satellite-aided tracking From the National Oceanic and Atmospheric Administration: National Environmental Satellite, Data and Information Service, Search and Rescue Satellite-Aided Tracking (SARSAT) website. Available at: http://www.sarsat.noaa.gov.

Perhaps no other type of SAR environment requires a more broadly based foundation of personal and team skills than winter snow and ice. These skills include downhill and crosscountry skiing, snowshoeing, technical climbing, winter survival, and a good understanding of snow and ice physics. Unlike rock, snow and ice conditions change on a daily and even minute-to-minute basis. The effects of gravity, wind, temperature, slope, heat exchange, load factors, and avalanche continually impose problems for missions under these conditions. Technical and nontechnical SAR problems in snow and ice environments take longer to address and are more taxing, technical, and complex. Combined with shorter days, extremes of weather, and the ever-present threat of hypothermia and localized cold injuries, technical missions of this type are unacceptable for all but the most experienced SAR personnel. Several chapters in this book address very important issues related to this type of environment: Chapter 5 (Accidental Hypothermia), Chapter 6 (Immersion in Cold Water), and Chapter 9 (Polar Medicine). Versatility and improvisation are essential components of the overall strategy that must be used in snow and ice. Transportation of the victim is often one of the most difficult problems, but it can usually be resolved through detailed preplanning. Innovations such as covering a litter with a canvas cover or improvising an attachment to cross-country skis are clever solutions to common winter problems. Commercial products such as the Hegg sled and the SKED litter (see Chapter 34) have streamlined the laborious task of transporting injured people through snow and ice. The references for this chapter can be found on the accompanying DVD-ROM.

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Loui H. McCurley and Steve E. Hudson Redcloud Peak is the 46th-highest of Colorado’s 52 “14ers” (i.e., peaks whose height is at least 14,000 ft [4267 m]). Located in the beautiful San Juan Range, the peak gets its name from an intense red coloring, making the mountain visually distinctive. A saddle connects Redcloud with its nearest neighbor, Sunshine Peak, making it possible to achieve this second summit with an hour’s hike from the top of Redcloud. Sunshine Peak, at 14,001 ft (4267.5 m), for many years held the dubious distinction of being the lowest 14er in the United

States. In a later survey, the peak gained 5 feet (1.5 m) and is now rated at a lofty 14,006 ft (4269.0 m). Height isn’t the only measure of merit or intensity of a peak, however, and most routes on the Sunshine–Redcloud combo, like most trails in the San Juan Range, are characterized by loose rock, steep terrain, and difficult route-finding. It is certainly not the best terrain for solo climbing, which is always discouraged in the backcountry. Nonetheless, for some people, the mountain experience is best when going solo. Thus, Daniel (name changed), an out-of-state

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visitor to the area, waved goodbye to his companion at the Silver Creek trailhead at 9:30 am one July morning and set off to do just that. The Silver Creek trail taken by Daniel travels into a basin northeast of Redcloud Peak. From here, the trail leads high into the basin and onto the peak’s northeast ridge. Traversing this ridge a half mile or so, the climber reaches the summit of Redcloud, and it is just another hour’s hike to the summit of Sunshine. The best egress from Sunshine is to retrace one’s steps back up Redcloud, down the northeast ridge into the basin, and back down Silver Creek Trail. Off-trail, Redcloud and Sunshine are rugged, marked by numerous steep to vertical drainages, steep scree fields, and talus the size of small houses. At 8:15 pm on the day of Daniel’s summit hike, J. Hunter Holloway, State Mission Coordinator for the Colorado Search and Rescue Board, received a call from the Lake County Sheriff’s office announcing that Daniel had been reported missing. Hunter mobilized several teams from around the state and commenced a search at daybreak with 70 well-qualified responders, several dogs, and an army Chinook helicopter. Seldom is wilderness rescue a nice walk in the woods followed by evacuation off a convenient cliff with a helicopter ride to the hospital, and the search involved to locate Daniel typifies the worst type of wilderness technical rescue for the medical professional. Daniel had undertaken a difficult route at breathtaking altitude, and when stressed, he behaved in an unpredictable way, further increasing search difficulty. Rescuers spent hundreds of hours combing the trails and surrounding terrain day and night. The physical demands of hiking miles of trail, then venturing off trail to negotiate scree fields, scramble over and search under huge talus, and rappel hundreds of feet of steepto-vertical gullies are challenging even for the most fit of rescuerathletes and require extraordinary levels of physical and mental agility. When Daniel’s body was eventually located, it was in a dangerous and compromising location that would require special rigging skills to evacuate. Finding Daniel alive likely would have imbued rescuers with the physical and psychological reserves to effect the evacuation. Instead, the exhausted team had to dig deep into already depleted reserves to remain attentive and energized to fulfill a discouraging operation. The search for Daniel was not unique. Lest the reader think wilderness rescue is a glorious task, let it be known that it frequently involves arduous hikes and climbs followed by less-than-ideal outcomes. Operations such as this, involving search of technically demanding terrain and the potential for a rope rescue evacuation, require personnel with special training and preparation. A medical professional may be exposed to a wilderness incident intentionally, while working in the capacity of a responder, or spontaneously, when witnessing an incident while part of an expedition or recreational outing. Preparing for these possibilities in advance, and resolving to keep the response consistent with the level of training, is the first step toward a successful outcome. Technical evacuations in the wilderness requiring ropes and special techniques range from steep slope to vertical, and even overhanging. Climbing skills do not prepare a person for the rigors of performing a technical evacuation of an injured person from rugged terrain. Experience with ropes and rigging in the urban environment is a useful first step, but preparation for wilderness rescue of the technical kind requires training and rescue in a genuine wilderness environment.

Figure 33-1. High-angle wilderness rescue. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

Wilderness settings are usually relatively inaccessible or not serviced by maintained roads, and they encompass a wide range of terrain and environmental conditions. High-angle rescuers find themselves working in hot, dry, desert conditions, or in snowy, thin-air, or alpine environments, and in anything between (Fig. 33-1). It is a fortunate rescuer who finds himself faced with a nice, clean cliff rather than steep and unstable rock, ice, thin gullies, or loose scree. This chapter addresses broad concepts of wilderness search and rescue; responders should evaluate their particular circumstances and seek specific training for the types of incidents that they may encounter. Not all rescuers need to be trained to the most advanced levels of wilderness operations, and individuals should always operate within the limits of their experience and training. Before attempting to respond to a high-angle rescue incident, responsible persons should ensure that every field team has a breadth and depth of experience to enable personnel to operate safely and make sound decisions. High-angle rescue operations in the wilderness (Fig. 33-2) are often complicated by circumstances unique to the specific environment. Examples include difficult terrain, hoisting (raising) operations, significant obstacle negotiation, navigational difficulties, descending or ascending operations from

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Figure 33-2. A haul team uses a mechanical advantage system during a high-angle rescue. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

extreme heights, and severe environmental conditions (i.e., snow, rain, altitude). In the United States, legal responsibility for wilderness rescue varies by state. In many of the eastern states, search-and-rescue (SAR) duties fall under the state’s Emergency Management Agency (EMA), which covers several services often grouped under the general umbrella of fire emergencies: firefighting, rescue, and emergency medical services (EMS). In most of the western states, law enforcement authorities are charged with SAR. On the oceans and for military personnel, U.S. Coast Guard and other military organizations handle SAR duties. In National Parks, rescues are handled by a mix of staff personnel and volunteer rescuers. Because of unique demands in terms of equipment, training, and techniques, organizations responsible for high-angle wilderness rescue typically have relationships with teams of specially trained volunteers or paid professionals. Rescue squads that perform technical rescue in the wilderness receive training from more experienced members of their own local teams, paid trainers from outside companies, and participation in national conferences and events. Paid trainers may provide a certificate to the individuals they train, based either on their own criteria or on nationally recognized criteria such as found in the National Fire Protection Association’s (NFPA’s) code, NFPA 1006.4 On a more formal level, the National Association for Search and Rescue has developed and oversees a system of training individuals in basic SAR, and the National Cave Rescue Commission maintains a system of training individuals at various levels in cave rescue techniques. Both organizations offer certificates in their respective courses, and all are aimed at the individual. Certification/accreditation at a team level is less common. Some paid trainers provide certificates of conformity to teams that they train, based on national team performance criteria, such as found in NFPA 1670.5 For teams that actively engage in a variety of backcountry rescue operations, the Mountain Rescue Association (MRA) offers team accreditation. However, this accreditation requires teams to meet strict performance requirements and to demonstrate their skills in a rigorous peer evaluation in rugged terrain search, technical rope rescue, and alpine (snow-and-ice and high-altitude) rescue. It is relatively

Figure 33-3. A high-angle rescue technician.(Courtesy Pigeon Mountain Industries,Lafayette, GA.)

impractical for teams that perform technical rescue in only one or two of these areas to seek accreditation, so MRA-accredited teams tend to be limited to areas where the full mix of rescue types are found. Persons who engage in wilderness technical rescue (Fig. 33-3) should be skilled in rope rescue techniques for mountain environments and should combine those skills with (1) an ability to operate effectively in weather extremes, (2) excellent navigational skills, (3) night operations skills, and (4) selfsufficiency for extended insertions. Medical skills and certifications are also useful.


EXPEDITIONS AND SPECIAL EVENTS

Medical and SAR personnel are often called on to assist with medical incidents and rescue needs for expeditions and at adventure-type races that involve rock climbing, rappelling, ascending, and other challenges with high exposure to adverse conditions. Sometimes, adventure race and outdoor experience events occur when there has been little or no preplanning for emergencies, relying completely on available resources, volunteer or paid, to respond in the event of an emergency. Other times, planners contract in advance with local resources, or hire individuals from local rescue agencies. Committing to high-angle rescue responsibility for a special event is a significant undertaking in our litigious society, so the decision should not be taken lightly by an individual or an organization. Often, event managers simply want to shift responsibility and are not willing to provide the support, funding, and resources necessary to effectively develop a complete risk management program. Many such events do not

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even have personnel dedicated to safety and rescue. Even EcoChallenge, a well-known adventure race, did not hire its first dedicated safety director until several years into its existence and until that time did not have a written safety plan. One study6 focused on a 10-day adventure race involving 197 competitors and recorded 761 cases of injury and illness in competitors and staff. Skin and musculoskeletal injuries accounted for 86.9% of complaints. Other interesting clinical problems included an unusual pattern of tenosynovitis, sleep deprivation, hallucinations, and hypothermia occurring in the tropics. More than 80 incidents required rescue, including rope rescue, technical carry-out, and helicopter evacuation. Provision for technical rescue services is but a small part of an overall safety plan for an event, and it should follow a comprehensive program that addresses and mitigates potential hazards to all personnel. Persons responsible for the rescue and medical components should be given sufficient authority and resources to ensure safety as well as effective rescue. Other considerations include questions of jurisdictional authority, medical authority, permits and access, and response protocols.

The Preplan Before engaging in any high-angle rope training or rescue, responsible individuals should perform a risk assessment to identify necessary skills and capabilities. The preplan should consider the types of terrain in the response area, people exposed to that terrain, types of accidents likely to occur, and available resources. Exposed personnel must be specifically trained for terrain and environmental considerations commonly encountered in the areas in which they may work. In addition, responders should be trained for the type of incident to which they are responding. For example, a rescuer responding to a fallen ice climber incident in the wilderness must be trained in both high-angle ice rescue and in wilderness SAR. In addition to helping prevent rescuer accidents, this also ensures an appropriate response to the incident. Having wilderness skills also enables rescuers to work independently of external support and resources in nonwilderness incidents. For example, self-sufficiency and an ability to function with minimal external resources are beneficial when working in the aftermath of an earthquake, or in responding to a transmission tower incident far from a road. Sometimes an accident demands a combination of traditional fire or EMS response and a wilderness response, and the personnel trained in all of the required disciplines are not available within one agency. It is not unusual for organizations or departments to have mutual aid agreements to maximize training and preparation of personnel. If personnel trained in only one of the necessary disciplines must go into the field on a wilderness operation, it should be only after a thorough risk assessment and after a conscious affirmative decision is made. Even then, rescuers not familiar with a particular environment or type of response should operate only under the direct supervision and care of appropriately trained personnel. Placing an untrained person in a high-angle rope rescue situation to perform patient care, for example, endangers that person, the patient, and others involved in the operation.

Team Training Responders who are part of a team should train together frequently to ensure good rapport and knowledge of one another’s

skills. Individual skills are often acquired simply by training with a local team. NFPA 16705 outlines some requisite skills for responding to wilderness incidents, but teams responding frequently or to technically demanding wilderness incidents should consider the benefits of technical rescue accreditation by a wilderness-focused organization such as the MRA. Whereas fire department teams that respond to wilderness rescue incidents may receive only 8 to 16 hours of wildernessspecific technical rescue training per year, Linda Finco, an MRA statistician, estimates that personnel from accredited MRA teams train an average of 140 hours per year. Some teams, particularly those frequently involved in highly technical or complex rescue scenarios, train as frequently as once or twice a week. Team training should take into account the types of incidents likely to occur in the local response area and should prepare team members to deal with general hazards associated with high-angle rescue operations in the wilderness. Considerations include the following: • Personal psychological hazards: The time to learn about psychological limitations, such as fear of heights or tight spaces, or a psychological dependence on external resources, is before an incident occurs. • Personal physical hazards: High-angle rescuers should be prepared for personal injury and physiologic hazards. Topics include harness fit and comfort, personal protective gear selection, care and maintenance of equipment, rappelling and ascending skills, ropes and knots, proper use of team gear, and specific rescue techniques. • Environmental hazards: On cliff faces and steep slopes, cracks and crevices in rocks may harbor stinging insects, venomous creatures, and poisonous plants. Rescuers on a steep or vertical face are susceptible to exposure injuries (cold and heat), lightning, and sunburn. • Terrain hazards: Terrains encountered in high-angle training and operations include rockfalls, avalanches, unstable footing, and high winds. • Operational hazards: Effecting a rescue has inherent hazards. Personnel moving around the site can increase the likelihood of rockfall or other falling objects. The rigging can pose increased hazards. A safety officer should be appointed at every rescue site to watch for and mitigate any unsafe conditions. High-angle rope technicians should be trained in appropriate self-care as well as in applicable rescue techniques and appropriate medical protocol for vertical rescue. Training and retraining should occur frequently enough to keep rescuers’ skills honed to an appropriate level. Several hours per month is not uncommon.


BASIC SKILLS Self-care is a critical skill for a wilderness technical rescuer. Rescuers must respect and be prepared for the wilderness environment, including being adept at functioning in it for extended periods—up to 72 hours—even in the most accessible of circumstances. They must be capable of caring for themselves as well as the victim during a rescue operation. Simple survival skills are a poor substitute for the ability to operate comfortably and effectively as a wilderness rescuer. All rescuers must be able to meet reasonable fitness requirements.

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TABLE 33-1. Terrain Classification

TABLE 33-2. Class 5 Climbing Grades: International Equivalents

Class 1 Class 2 Class 3

UNITED STATES

Class 4 Class 5

Flat, even—easily traveled by foot Uneven—traveled by foot with some balance required Steep—feet primary means of support, hands may be used to assist; rope a good idea Scramble—feet and hands required; rope necessary for safety Vertical—roped protection required for safety (This category is further divided by the various classification systems compared in Table 33-2.)

5.2 5.3 5.4 5.5

UNITED KINGDOM

FRANCE

4a

1 2 3 4

4b

5

AUSTRALIA 11 12 13

5.6 5.7

14 4c

Wilderness is seldom flat, so field personnel involved in any wilderness rescue should understand terrain and navigation, as well as technical and rope rescue systems. In mountaineering terminology, terrain is generally classified in numeric terms (Table 33-1). When the terrain is vertical, it is subclassified into further levels of difficulty, the most common being the Yosemite decimal system (originated and primarily used in the United States), the U.K. system, and the French system (Table 33-2). A climb may be rated in accordance with the system used by the country it is in or by the nationality of the climber who established the route. Technical rescuers for wilderness operations should be able to determine, document, and communicate their position; perform point-to-point navigation with a global positioning system (GPS) as well as map and compass; and be adept at route finding using point-of-reference, dead-reckoning, and map skills. At the most basic level, sometimes referred to as the awareness level, the priorities for a responder’s individual skills are to be able to recognize that a wilderness technical rescue situation is developing, to know how to activate appropriate resources, and to support the ensuing rescue. This involves being able to perform a realistic analysis of terrain hazards, weather conditions, and limitations of available resources. Would-be rescuers have been injured or killed because their initial reaction to an incident was inconsistent with their level of training or equipment. In any emergency, it is difficult to wait for the arrival of additional resources. Yet, responders at the awareness level can tip the scales in favor of the victim by focusing their energies on effectively securing the scene and initiating the collection of key information that will ultimately help resolve the incident. This sizing up of the scope and magnitude of the situation sets the stage for the rescue, and a corresponding response is initiated. In the critical first moments, a risk-to-benefit analysis is initiated, and the safety of the rescuers and of the victim is provided for. An effective initial response can enhance the probability of success. More advanced skills for wilderness rope rescue expand on the basic principles. NFPA 16705 identifies a response level of training, which corresponds with the MRA support level. At this level, responders are capable of functioning effectively on a technical rescue (one that requires rope and special equipment and skills) in the wilderness, and of working under the direction of more experienced personnel. The next NFPA level is the technician level (corresponding with the MRA rescue level). Here, technical requirements are expanded and honed. The MRA adds yet another level of expertise, the qualified level, at which an individual’s breadth and depth of training, as well as

5+

15

6a 6a+

16 17 18 19

5.8 5a 5.9 5b 5.10a 5.10b 5c 5.10c 5.10d 5.11a

20 6b 6b+ 6c

21 22

6c+ 7a 7a+

23 24 25

7b 7b+

26

7c

27

7c+ 8a 8a+ 8b 8b+ 8c 8c+ 9a

28 29 30

6a 5.11b 5.11c 5.11d 6b 5.12a 5.12b 5.12c 5.12d 5.13a

6c

5.13b 5.13c 5.13d 5.14a 5.14b 5.14c

7a 7b 7c 8a

31 32 33

experience, results in unsurpassed expertise. Experience is the key when it comes to making subjective decisions about technical evacuations in the mountains. Personnel operating in mountainous terrain where steep and vertical slopes are common should be comfortable functioning in that terrain before engaging in mountain rescue. Familiarity with basic climbing techniques is essential, as is the ability to rappel and ascend rope. Techniques similar to those used recreationally are sufficient, so long as adequate safety is provided. Other useful skills to develop and practice include leadership under stressful situations, interfacing with aircraft and watercraft, provision of specialized medical care, patient care during extended transport, and equipment transport over terrain. Rope rescue can be intense and demanding and may require more than just one or two experienced individuals to accomplish an effective response. Most teams should have several people trained to the NFPA response (or MRA support) level. Even with several people trained to this level, it is important to have at least a few with a strong depth of experience in a variety of terrains, or at the technician (or rescue) level. A skill achieved

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on a steep slope, such as a lower or raise, can change dramatically as the angle increases. As the geometric influences change, opportunity for and consequences of failure increase as well. Finally, active teams should have several people who meet the MRA requirements for qualified rank. True skill in this arena requires personnel who are honed in every way and backed with a depth of experience and decision-making ability. In addition, enhanced rigging skills and concepts are required—specifically, load-distributing anchors, highlines, and knot passes. Training in these concepts is stimulating and even enjoyable, but proficiency requires much repetition and numerous hours of training. A reasonable path of education begins with the selection, care, and maintenance of appropriate rope rescue equipment. It expands to personal rope skills such as ascending and descending a rope. Finally, it extends to proficiency in high-angle systems, including raising and lowering systems, highlines, track lines, anchor systems, and belays. Training alone, however, is not sufficient. High-angle wilderness rescue personnel should have the appropriate attitude and aptitude for working on steep terrain, sometimes for extended periods. Appropriate preparation depends on the environment in which the rescuer will function—hot, cold, dry, wet, snowy— and the length of time it will be necessary to stay in that environment. Gear must be specific for the environment.


PERSONAL PROTECTIVE GEAR

• Helmet: well fitting, with ventilation holes and a secure threepoint suspension (Fig. 33-5) • Eye protection: close fitting to protect against sun, wind, debris • Clothing: appropriate moisture transport (wicking or nonwicking), appropriate insulation, wind- and water-repellent • Gloves: appropriate for temperature and protection • Footwear: well fitting, lug sole, appropriate to the environment • Backpack: appropriate capacity; protection against injury in the vertical environment There are several versions of the “10 essentials” list for mountaineers and wilderness travelers (including such items as water, matches, and compass), and this is a good starting point for the rescuer as well. However, the purpose of the equipment is not just survival but should instead focus on function. The highangle rescue technician is a professional, focused on operating effectively, not just surviving!


PATIENT CARE AND TRANSPORT The level of patient care that a responder can provide depends on circumstances, training, and resources. A spontaneous response provided when an incident happens in front of the responder is different from a planned response by a trained rescuer, and the expectations differ also. In a spontaneous incident, it is reasonable and prudent for a bystander to render basic emergency care while notifying

The well-prepared high-angle rescuer has equipment that is appropriate for and designed to function effectively in the wilderness environment (Fig. 33-4). The following list is an example of equipment that might be needed:

Figure 33-4. Rescuer’s personal protective equipment: helmet, gloves, footwear, backpack. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

Figure 33-5. Three-point suspension on a helmet. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

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Figure 33-7. Spec Pak. (Courtesy Pigeon Mountain Industries, Lafayette, GA.) Figure 33-6. A Hasty pickoff seat. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

authorities, and to continue until trained rescuers arrive. Those with some level of medical training have a slight advantage in understanding what needs to be done to evaluate the scene, protect the patient (and others) from further harm, and perform basic life support until help arrives. Those who expect to respond intentionally to outdoor emergencies should be trained at least to an emergency medical technician basic or first-responder level, or the outdoor equivalent of one of these, and they should be able to organize and participate in a progressive litter carry on moderate to rugged terrain. If steep or vertical terrain is likely to be encountered, they should have a good working knowledge of rope rescue systems. Extrication and evacuation of a patient from steep or vertical terrain requires special consideration in terms of practicality and patient protection. Some patients may already be wearing a harness, and the rescuer needs to determine whether it is appropriate to use the patient’s harness for extrication or to use an adjunct. Using the patient’s own gear is often discouraged, because the rescuer cannot know its history or condition. However, sometimes this is the best alternative available. When it is reasonable and advantageous to use the responder’s gear for the evacuation, and when the patient is not injured, the best choice is usually an evacuation seat (Fig. 33-6), which is easy to put on the patient and usually feels more secure than a typical harness. When the patient is injured and must be moved from complex terrain, the combination of a harness and an evacuation device is an excellent tool. Some common examples of these are the Spec Pak and LSP Half Back (Fig. 33-7). This type of equipment requires special medical and technical training and expertise to avoid further injuring the patient. Depending on the patient’s medical condition and injuries, it may be prudent to place him in a litter before moving him.

Chapter 34 discusses litters and carries in greater detail. For vertical operations, rigid-basket-style litters offer greater patient protection and comfort than do flexible litters and are the preferred choice for rope rescue evacuations.

Rigid Basket Litter The first priority of a high-angle rescue is the safety and protection of the patient. Numerous accessories for rigid litters are available that are specific for this use (Fig. 33-8). Immobilization can be accomplished with a narrow-profile backboard, but beanbags are by far the preferred immobilization device for litter evacuations. The patient’s head and face should be protected either with a helmet and sunglasses or with a litter shield (Fig. 33-9). Special attention should be given to securing the patient into the litter for a high-angle evacuation. This can be improvised using long strands of webbing, or special tie-in straps may be used (Fig. 33-10). For steep or vertical terrain, seat belt straps are not sufficient. The system chosen should thoroughly secure the patient into the litter and protect against further injury. Although inversion or tipping of the litter may seem unlikely, steps should be taken to protect against the consequences if it should happen. The patient should be secured not only with straps over the body but also from slipping out either end of the litter. Foot loops, shoulder loops, and waist attachments are all excellent for this purpose. In addition, if the patient is wearing a harness, a security strap from it to the main lowering or belay line is a good idea. Litter wheels, usually preferred for trail use, can also be useful in slope evacuation, particularly when there are a limited number of rescuers. Short, fat tires such as those on all-terrain vehicles are stable on a horizontal plane and absorb trail shocks well (Fig. 33-11). Larger, dirt-bike tires are more efficient and maneuverable (Fig. 33-12).

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Figure 33-8. Cascade Professional Series litter. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

Figure 33-9. Patient protection: helmet and glasses or goggles. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

Figure 33-11. All-terrain vehicle (ATV) tire litter wheel.(Courtesy Pigeon Mountain Industries, Lafayette, GA.)

Litters can be rigged for high-angle evacuation in either a horizontal (Fig. 33-13) or a vertical (Fig. 33-14) configuration. Vertical configurations offer a lower profile for rockfall, but they can be quite disconcerting for the patient. In the United States, high-angle rescue is usually done with the litter in a horizontal configuration. The litter is supported and connected to the end of the lowering line by a device commonly called a litter spider or bridle. These are available in different forms, ranging from four litter attachment points and a single mainline connection (Fig. 33-15) to six litter attachment points and dual mainlines (Fig. 33-16). Each system offers advantages and disadvantages. Persons wanting to begin a high-angle rescue program, or to update their current technology or systems, should seek specialized training from a qualified professional.

Flexible Litter

Figure 33-10. FAST patient tie-in. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

The light weight and compact size of flexible litters make them attractive choices for expeditions or other small-team situations. They can also be convenient solutions in caves, mines, or other confined spaces. Flexible litters are best used with some sort of spinal immobilization, and they are not well suited to high-angle rope rescue without additional equipment. They can be placed inside a larger rigid-frame litter once the patient is removed from the confined space, for quicker lowering and raising operations without a complete repackaging of the patient.

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A B Figure 33-12. A, Motocross-tire litter wheel uses a secure universal saddle to attach to any litter. B, Motocross-tire litter wheel provides clearance and maneuverability for difficult terrain. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

It may be feasible to use a flexible litter (Fig. 33-17) for high-angle rescue, but each brand and model requires specific training. The rescue team must be well trained in the specific high-angle rigging recommendations from the manufacturer of the chosen flexible litter.


RESPONDING TO THE

WILDERNESS INCIDENT

Figure 33-13. Litter rigged in horizontal configuration with basic single rope attachment. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

Although different situations require different responses, every responding group or agency can be expected to establish protocols and training criteria that are appropriate to the training and experience levels of its members. Military organizations provide a good model, refined over the years, for managing varying numbers of people in constantly changing field circumstances, and many rescue teams find it convenient and effective to function in a paramilitary manner. Teams may establish personnel ranks to help quantify levels of capability. At the top of the rank is a command structure that helps to streamline

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Figure 33-14. Litter rigged in vertical configuration. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

Figure 33-16. Six-point litter spider. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

Figure 33-17. Sked flexible litter. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

Figure 33-15. Four-point litter spider. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

operations and ensure that qualified personnel manage the incident. The Incident Command System (ICS) or Incident Management System (IMS), a framework developed initially to assist in managing wild-land firefighting operations, has been adapted by many for wilderness rescue operations. Most professional organizations, paid or volunteer, use some variation of the ICS to manage operations.

In the ICS, an incident commander assumes operational control of an entire incident and has several section chiefs to oversee different aspects of the incident. The sections typically include operations, planning, logistics, and finance or administration. The ICS-100 class, available through many municipal governments, is a good introduction to this system. Field personnel typically operate primarily under the operations section of the ICS system. Most wilderness technical rescuers have a combination of technical and medical skills. For wilderness rope rescue operations, the need for technical skills generally outweighs the need for medical skills. Most rescues involve a finite number of patients (usually only one or two), but every responder will probably be faced with the technical aspects of the evacuation.

Chapter 33: Technical Rescue in the Wilderness Environment When neighboring teams often find themselves working together on an incident, it is advisable to synchronize personnel training and team structure, at least to some degree. Having similar ranking systems and operational criteria facilitates working together. Some teams become accredited under national criteria, such as those of the MRA, for just this reason.

The Callout Members of technical mountain rescue teams who respond at the request of local authorities often carry a pager so that they may be contacted quickly in the event of an emergency. When the pager goes off, members rendezvous at team headquarters or at a staging area (the command post or mission base) from which the event is initially coordinated. As soon as a command post or mission base is established, it is given a unique name to identify it, in case another command post must be established for the same mission at a later time, or in case another mission occurs within radio range while the original mission is still going on. Often the name reflects the search area (e.g., Chester Valley Command).

Scene Size-Up Some rescue organizations classify types of rescue according to the degree of slope involved in the evacuation. According to NFPA 1670,5 low-angle refers to an environment in which the load is predominantly supported by itself and not the rope rescue system (e.g., flat land or mild sloping surface), and highangle refers to an environment in which the load is predominantly supported by the rope rescue system. The first person on the scene immediately sizes up the situation and activates appropriate resources. Reevaluation of size-up criteria is then a continuing process throughout the duration of the incident. In addition to collecting information specific to the incident, a wilderness environment size-up should consider the following factors.

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Prearranged agreements with nearby agencies can be very useful in staffing a large incident or for backup in case of another call.

Specific Environmental Factors Involved. Are available personnel suitably trained and equipped for the terrain that will be encountered? Is there a river or lake in the area that will require additional personnel? What is the time of year? Is snow or ice a consideration? The steepness of terrain as well as groundcover must be considered when estimating whether personnel are adequately prepared to function. Integrity and Stability of the Environment Involved. Is a storm coming? Will night fall before the operation is done? Planning to accommodate for changes in weather, ground instability, and other environmental factors must be done several hours in advance. Number of Known and Potential Victims. When the potential of additional victims becomes a reality, the number of rescuers needed increases, and other stresses emerge. A new sense of urgency arises, and there is a need for triage, more equipment, more time, and more resources for evacuation. Additional potential victims must be anticipated.


EVACUATION TECHNIQUES It is not possible to predict the rope rescue systems and techniques that would be most appropriate for every response. The choice is subjective and depends, for example, on environmental conditions, the nature of the incident, height considerations, and the number of rescuers available. Responders should be led by rescuers with enough experience and training to make good decisions.

Low-Angle Litter Lowers Scope and Magnitude of Wilderness Influence. Is the incident 100 yards from a vehicle access point, or several miles into the backcountry? Is the best evacuation route at the top or at the bottom of the slope or cliff? The first person on scene should ask these kinds of questions to determine necessary resources. Scope and Magnitude of High-Angle Influence. Is the highangle obstacle to be negotiated a steep slope, or is it a cliff? How large or accessible is the slope or cliff? Are decent anchors available? The scope and magnitude of the incident will affect the type and number of resources requested. Assessment of Time Required. How long will the evacuation take? Will there be darkness and lighting considerations? How physically demanding will the operation be, and how often will rescuers need to be rotated for rest? The answers will influence resource requirements and may indicate that additional resources must be called in from farther away. Assessment of Manpower Needs. Given the time and work to be done, will changing shifts be a consideration? Is it necessary to keep responders available for a second incident in the area? Are there sufficient resources within the organization, or will external resources be required? Dedicating all resources in a given area to one incident requires consideration in advance.

Low-angle evacuations are typically performed in terrain that allows the majority of the rescuer’s weight to be supported by the ground, but a rope is used in addition for the safety and security of the rescuers. Examples of such terrain are snow slopes, inclined land near bridges, river embankments, scree or talus fields, and roadsides. A typical low-angle litter lower is a personnel-intensive rescue. A site commander should be assigned to manage the operation. This role requires depth of experience, knowledge of personnel and techniques, and familiarity with the terrain. Many teams assign the most experienced person on site to be in charge of site safety, responsible for checking and verifying all aspects of site safety. This person must be free from any other responsibilities or distractions. Other roles and responsibilities include brakeman, rope handlers, and medical personnel. The medical person may serve also as a litter bearer or stay separate from the system. Usually, four litter-bearers carry the patient, but the number may be as few as three or as many as six. Either a plastic shell litter or a metal basket litter may be used for a low-angle evacuation. A plastic shell litter provides more protection to the patient from underbrush and ground cover, but it is not as rigid as the metal basket and offers fewer options for rescuers to tie into or hold onto the litter. A litter bridle (Fig. 33-18) may be used, or the rope may be tied directly into the litter by wrapping it several times around the head of the litter (Fig. 33-19) and then tying off with a

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Figure 33-18. Litter tied in with bridle for low-angle evacuation. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

weight and medical condition of the patient, and the stability of the environment. In flatter terrain, less of the patient’s weight is taken by the rope and more must be carried by litter bearers. A litter wheel may be used in a low-angle evacuation to help support the weight of the litter. On steep slopes, rescuers can gain a certain amount of leverage by wearing a harness and connecting to the litter with cordage or webbing (Fig. 33-21). This adds stability and helps support the litter. Tie-ins may be made of cordage or webbing and are hitched to the litter rail before being clipped to the litter bearer’s harness with a carabiner. If a split litter is used, tie-ins should be connected to the head-end of the litter to avoid undue stress on the connections. Other techniques, including the use of hauls and counterbalances, hand passes, and litter wheels, may be combined with low-angle evacuation techniques or, occasionally, used in their stead. Further direction and instruction regarding low-angle rescue may be found in specialized textbooks.7

Vertical Litter Lowers

Figure 33-19. Litter tied in directly for low-angle evacuation. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

bowline or figure-8, so that the litter is in line with the slope. Wrapping the litter several times like this helps to distribute the force across a wider area, gives some lateral stability to the litter, and helps to avoid undue pressure on the weld that is often found at the center-head of a wire basket litter. The main line of the system supports the load as it is being lowered down the slope (Fig. 33-20). A secondary, or belay, line can be incorporated into the system. This decision should be made in accordance with an appropriate risk-to-benefit assessment. The number of rescuers required for a low-angle evacuation depends on several factors, including the degree of slope, the

When vertical or near-vertical terrain dictates a high-angle rescue system, personnel with specific experience in these techniques should be deployed. Proficiency in high-angle rescue techniques takes a great deal of training and experience. The most common type of high-angle rescue system is known as a single-point vertical fixed-brake lower (Fig. 33-22). This type of system requires at least six well-trained, skilled rescuers. For this, as with the low-angle operation, a site commander should be assigned to oversee all aspects of the operation. Other roles involved include site safety, brakeman, and rope handlers. A belay system is almost always utilized in high-angle rescue operations, in which case a belayer and separate rope handler also become necessary. High-angle rescue operations generally utilize only one or two litter bearers, although one or two additional persons may be required to assist the litter in getting over the edge. These “edge tenders” are also responsible for ensuring that ropes and equipment are well protected as they go over the edge. Occasionally, a separate rappel or lowering line is arranged for a medical attendant or for an extra person to assist with the technical aspects of a mid-face loading procedure. This “third man” is especially valuable as because he or she is not linked directly to the lowering system. Variations on the basic single-point fixed-brake litter lower include the single-point traveling-brake (Fig. 33-23) and the two-rope (scaffold) vertical lowering system (Fig. 33-24). These systems are even more complex and require special training and skills beyond those required for the single-point fixed-brake lower.

Raising and Haul Systems Although the knowledge of lowering systems is essential for competent rope rescue personnel, many rescues involve raising a victim from a low point to a high point. This may occur as part of a lowering system or separately—as in the case of a victim who has fallen into a gorge, or where the carryout trail is higher than the victim’s location. Mechanically, the simplest means of raising a load is via a direct pull. Physically, however, this is not always feasible. The force required to move a load can be greatly reduced by using pulleys and rope to create a mechanical advantage. With a mechanical advantage system, a relatively heavy load can be

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Anchor Brakeman Brake

Litter and litter bearers

Figure 33-20. Example of the rigging and teamwork in a low-angle rescue. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

how efficiently the system is rigged and on the efficiency of the components used to build it. Designing haul systems and optimizing mechanical advantage are advanced skills and require special training and expertise.

Alternative Techniques

Figure 33-21. Low-angle litter bearer tie-in, in use. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

moved with minimal force. Depending on the configuration of pulleys and rope, varying amounts of mechanical advantage can be produced, and the amount of the advantage can be calculated. This haul capability is generally expressed as a ratio. For example, a system wherein a 100-pound load could be moved with a calculated 50 pounds of force is a 2:1 (two-to-one) mechanical advantage, known as a theoretical mechanical advantage. The theoretical mechanical advantage is always greater than the actual mechanical advantage. The actual mechanical advantage produced by a hauling system depends in great part on

Occasionally, a terrain is too complex to allow the use of a basic low-angle or high-angle raising and lowering system, in which case a number of techniques are available. One group of techniques that is particularly useful involves a highline, which is a rope suspended between two points and across which personnel and equipment can be moved. Highlines can be simple or very complex to rig. Even at their simplest, however, highlines are a time-, personnel-, teamwork-, and communicationsintensive technique. At the simplest level, a highline may consist of a single line, or “main line,” across a span. Adding a second main line results in a dual main-line system. One of the most difficult parts in rigging a horizontal highline is getting personnel from the near side of the operation to the far side of the operation. Because a highline often spans difficult terrain such as a river or gorge, the process can be time consuming. Once personnel are at the far side of the operation, the rope can be sent across using a lighter-weight leader-line launched by a giant slingshot or line gun. Perhaps more than any other rope rescue technique, highlines have the potential for overstressing rope, equipment, and anchors, thus causing failure of the system. Rigging and use of highlines require thorough knowledge of the potential forces involved. A highline system may include one or two main lines, also known as track lines. These should be of a low-stretch design, such as static kernmantle (see Chapter 84), to avoid excessive

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Figure 33-22. Example of the rigging and teamwork in a high-angle rescue. (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

stretch in the system. Track lines should be rigged with sufficient sag (up to 10%) to prevent overstressing the system. The main lines should be attached to very trustworthy anchors at each end. At least one of these anchors should be rigged with a tensioning system to allow the sag in the highline to be adjusted. Pulleys are used to facilitate movement of the load across the track line or lines. Nearest the point of origin of the operation, a lowering system is helpful for controlling the load as it starts across the highline. At the other end, a haul system may be required to bring the load back up the other side of the sag. These additional systems may also be incorporated into a safety (or backup) for the highline. A complex highline is a good test of many different rope rescue skills, particularly those incorporating special rigging known as a reeve. Such systems can make it possible to raise and lower loads from mid-span. The personnel requirements for operating a highline are quite similar to those for a low-angle or vertical lowering operation, but multiplied by the complexity of the system. There should

be a site commander at each end of the system, plus sufficient personnel to operate whatever lowering or raising systems are incorporated. A highline may be rigged at a steep angle to provide a “track” for lowering or raising personnel or equipment above obstacles. This type of highline, sometimes called a guide line, can be very useful in negotiating difficult terrain. Such was the case in an area known as the Wonderland of Rocks at Joshua Tree National Monument several years ago, when a 250-lb (113-kg) Boy Scout sustained a tibia-fibula fracture and ended up stuck in a crack between house-size boulders. Wonderland of Rocks is a unique formation involving more than 6 miles of huge boulders jumbled across the desert floor. The boulders range from the size of a car to the size of a large house. They are stacked and strewn upward and outward so that the area is largely impassable—making it a challenging and enjoyable area for scrambling, hiking, and technical climbing. One miscalculation, however, can have severe consequences.

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Figure 33-23. Traveling-brake system (vertical). (Courtesy Pigeon Mountain Industries, Lafayette, GA.)

Figure 33-24. Scaffold system (vertical).(Courtesy Pigeon Mountain Industries,Lafayette,GA.)

This particular accident scene was visible from an adjacent access road, but accessing it required an hour of strenuous scrambling and climbing. At outset, it seemed that the 20 or so rescuers who responded would need to rig a vertical raise to extricate the patient, followed by a series of high- and low-angle lowers and raises in series to get the patient to the desert floor. From there, the carry-out would involve crossing a sandy dry riverbed and then a short haul up a slope to reach the road. The operation would take many hours, and additional resources would be required. The patient, who was in great pain, would be subjected to a grueling evacuation. The alternative evacuation method involved a track line system with a short raise at the top to extricate the patient. Two 600-foot ropes were located, and the track line that was established allowed the patient to soar over the difficult terrain in a fraction of the time that would have been required for the original evacuation plan.

wilderness type of incident. Advance planning, preparation, and training are the best way to mitigate the hazards associated with this type of incident. The critical thing, according to MRA legal advisor David Thorson (www.mra.org), is not that one particular standard or another be followed, but that an organization acknowledge the existence of a given standard and make a conscious decision to either abide by or deviate from it. There are several resources for information on accepted practice and standards for technical wilderness rescue. The ASTM (formerly the American Society for Testing and Materials) F32 Committee on Search and Rescue is a national standards body that has authored several in-depth national standards on searchand-rescue equipment, training, and resources.1 The MRA2 provides resources and accredits teams in skills and capabilities for technical rescue operations in the mountains. The National Association for Search and Rescue (NASAR)3 is an excellent resource but does not yet provide certification for technical rescue skills. It has developed the SAR-TECH program for individuals. In addition, some states, including Maine and Pennsylvania, have developed standards for SAR, and individual teams standardize everything from techniques and equipment to the color of their webbing. High-angle technical rescue in the wilderness environment is a very specialized field. Medical personnel and rescuers interested in engaging in high-angle rescue work should receive thorough training and complete an apprenticeship. Further direction and instruction regarding high-angle rescue may be found in specialized textbooks.7


SUMMARY Wilderness can be defined as “an uncultivated, uninhabited, and natural area usually, but not necessarily, far from human civilization and trappings.”5 A wilderness rescue, then, is one that occurs in this environment, and a technical wilderness rescue is a wilderness rescue that requires rope and special equipment and skills. Depending on the terrain and on environmental factors, a wilderness incident may be as little as a few minutes into the backcountry or a few feet off the roadway. Specialized mountain or wilderness rescue teams are common in only a fraction of the United States, but this does not preclude the rest of the country from susceptibility to an occasional

The references for this chapter can be found on the accompanying DVD-ROM.

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34

Litters and Carries Donald C. Cooper, James Messenger, and Timothy P. Mier

Every search and rescue event goes through a series of four consecutive phases. These phases are illustrated by the acronym LAST (locate, access, stabilize, and transport). This process ends with the movement of the patient (or patients) from the scene to either a medical facility or an area of comfort and safety (transport)6 (see Chapter 32, Search and Rescue). In the United States, the term stretcher suggests a flat, unsophisticated frame covered with canvas and used for carrying the sick, injured, and deceased short distances. The term litter can mean the same thing, but usually suggests an apparatus specifically designed to immobilize and carry a patient longer distances. Over the years, the subtle differences in the terms have been lost, and users have gravitated to one or the other. In the United States, the term litter is used to describe all manner of rescue conveyance. In Great Britain, however, the preference is to use the term stretcher to describe the same devices. In this chapter, the two terms are used interchangeably.


SIZE-UP To select the best method for getting a patient to definitive care, the rescuer must make a realistic assessment of several factors. Scene safety is the initial priority. The necessary evaluation, called the size-up (Box 34-1), involves a (usually hasty) determination of whether the victim, rescuer, or both are immediately threatened by either the environment or the situation. Proper immobilization and patient packaging are always preferable, but sometimes the risk of aggravating existing injuries is outweighed by the immediate danger presented by the physical environment. In such a situation, the rescuer has little choice but to immediately move the patient to a place of safety before definitive care is provided or packaging is completed. Evacuation options are limited by three rescuer-related variables: (1) the number of rescuers, (2) their level of fitness, and (3) their technical ability. Carrying a victim, even over level ground, is an arduous task. At an altitude where just walking requires great effort, carrying a victim may be impossible. The specific rescue situation or environment encountered also may present challenges beyond the capability of the available rescuers. Complex rescue scenarios requiring specially trained personnel and special equipment are called technical rescues and often involve dangerous environments, such as severe terrain, crevasses, avalanche chutes, caves, or swift water. To avoid becoming victims themselves, rescuers must be realistic when evaluating their ability to perform these types of rescues.


DRAGS AND CARRIES The most fundamental and expedient method of transporting an ill or injured person is by dragging or carrying him or her. Although these methods of transportation are far less than ideal and may not meet standard care criteria, the urgency of the situation may outweigh the risks involved. In addition, the process can be physically demanding, and rescuers can quickly become fatigued to the point of hazard. Therefore, other options often should be considered before a victim is moved, especially a long distance. A drag or carry may be the best option when a person cannot move under his or her own power, injuries will not be aggravated by the transport, resources and time are limited, the need for immediate transport outweighs the desire to apply standard care criteria, the travel distance is short, or the terrain makes the use of multiple rescuers or bulky equipment impractical. A blanket drag (Fig. 34-1A) can be performed on relatively smooth terrain by one or more rescuers rolling the victim onto a blanket, a tarp, or even a large coat and pulling it along the ground. This simple technique is especially effective for rapidly moving a person with a spinal injury to safety because the victim is pulled along the long axis of the body. In extreme circumstances, the fireman’s drag (see Fig. 34-1B) can be used. In this type of drag, the rescuer places the bound wrists of the victim around his or her neck, shoulders, or both and crawls to safety. A carry should be considered only after it is confirmed that the victim cannot assist rescuers or travel on his or her own. Beyond simply lifting a person over one’s shoulder in a fireman’s carry (Fig. 34-2) or acting as a human crutch, a more efficient one-person carry can be accomplished by using equipment, such as webbing, backpacks, coils of rope, or commercial harnesses. Equipment-assisted carries are particularly effective when an injured climber or hiker must be evacuated across a short distance over rough terrain or when a person must be quickly removed from a hazardous environment. In the simplest equipment-assisted carry, 4.5 to 6 m (15 to 20 feet) of webbing is wrapped around the victim, who is “worn” like a backpack by the rescuer (Fig. 34-3). Similarly, a backpack or split coil of climbing or rescue rope can be fashioned into a seat around the victim and hoisted by the rescuer. A rescuer can modify a large backpack by cutting holes in the bottom for the victim’s legs, who then sits in it like a child would sit in an infant carrier (Figs. 34-4 and 34-5).

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Box 34-1. Evacuation Size-Up Factors What are the scope and the magnitude of the overall situation? Are there immediate life-threatening hazards? What is the location, and how many victims are there? What is the patient’s condition? Is the subject able to assist rescuers? a. No injury (able to walk unassisted) b. Slight injury (able to walk unassisted) c. Slight injury (assistance required to walk) d. Major injury (requires considerable attention and assistance) e. Deceased Is there a need for technical rescue? Is the scene readily accessible? What rescue resources (including rescuers and equipment) are available? How far must the patient (or patients) be transported? Are ground or air transport assets available? Figure 34-2. Classic fireman’s carry: a single rescuer technique for short distance transport only.The rescuer must use his or her legs for lifting. (From Auerbach PS: Medicine for the Outdoors: The Essential Guide to Emergency Medical Procedures and First Aid, 4th ed. New York, Lyons Press, 2003.)

A

B Figure 34-1. A, Blanket drag.B, Fireman’s drag.Both techniques are intended to be used when expeditious transport over a short distance is required.(From Auerbach PS:Medicine for the Outdoors: The Essential Guide to Emergency Medical Procedures and First Aid, 4th ed. New York, Lyons Press, 2003.)

A few commercial harnesses allow a lone rescuer and single patient to be raised or lowered together by a technical rescue system. A Tragsitz is one example (Fig. 34-6). For carrying infants and small children, a papoose-style sling works well and can easily be constructed by the rescuer tying a rectangular piece of material around his or her waist and neck to form a pouch. The infant or child is then placed inside the pouch, which can be worn on the front or back of the rescuer’s body. If two rescuers are available, additional and often superior options for carrying a victim are possible. One option consists of two rescuers forming a seat by joining their hands or arms together. The victim sits on the “platform” and holds on to the rescuers for support. It is difficult to cover a long distance or rough terrain when using this technique (Fig. 34-7). A coil of climbing or rescue rope can be used to form a tworescuer split coil seat, with each rescuer slipping a side of the rope coil around his or her outside shoulder (Fig. 34-8). The patient then sits on the “seat” formed by the rope. A similar approach involves using padded ski poles or stout limbs tied together and supported by backpacks worn by rescuers. The victim sits on the supported poles with his or her arms around the rescuers’ shoulders. If the poles are properly padded and securely attached to sturdy rescuers, this technique can be quite comfortable for both rescuer and victim. This approach requires gentle terrain without narrow trails. Spine injuries generally prohibit the use of drags or carries because the victim cannot be properly immobilized, but drags or carries may be acceptable when immediate danger outweighs the risk of aggravating existing injuries. Drags are particularly useful for victims who are unconscious or incapacitated and unable to assist their rescuer (or rescuers), but may be uncomfortable for conscious victims. When a drag is used, padding should be placed beneath the victim, especially when long

Figure 34-3. Web sling (tied into a loop) used to carry a victim.The rescuer must use his or her legs for lifting.

Figure 34-4. Backpack carry.

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Figure 34-5. Single-rescuer split coil carry.Note that the coil can be tied in front of the rescuer, and the wrists of the victim can be bound and wrapped around the rescuer’s neck for more stability.

distances are involved. The high fatigue rate of rescuers makes carries less attractive options when long distances are involved.


LITTER IMPROVISATION The simplest improvised litter is made from a heavy plastic tarpaulin, tent material, or large polyethylene bag (Fig. 34-9). By wrapping the material around a rock, wadded sock, or glove and securing it with rope or twine, the rescuer can fashion handles in the corners and sides to facilitate carrying. The beauty of this device is its simplicity, but it can be fragile, so care must be taken not to exceed the capability of the materials used. As an additional precaution, all improvised litters should be tested with an uninjured person before being loaded with a victim. This type of nonrigid, “soft” litter can be dragged over snow, mud, or flat terrain but should be generously padded, with extra clothing or blankets placed beneath the victim. A coil of rope also can be fashioned into a litter, called a rope litter or clove hitch stretcher, but a 46- to 61-m (150- to 200-foot) climbing or rescue rope is required (Fig. 34-10). The rescuer constructs the litter by laying out 16 180-degree loops of rope (8 on each side of center) across an area the desired width of the finished litter. The running ends of the rope are used to tie a clove hitch around each of the loops, and then the unused portion of rope can be passed through the loops on the other side and tied off. The litter is then padded with clothing, sleeping pads, or a similar material. Lateral stability can be added by tying skis or poles to the finished product. Because of its nonrigid construction, this litter offers little back support and is best suited for victims with injuries that do not require immobilization.

Figure 34-6. Tragsitz harness in use.

A sturdy blanket or tarp can be used in combination with ski poles or stout tree branches. The blanket or tarp is stretched over the top of two poles, which are held about 1 m (3 ft) apart; tucked around the far pole; and folded back around the other pole. The remaining material lies over the first layer to complete the litter (Fig. 34-11). The weight of the victim holds the blanket in place. A similar device can be improvised by passing the poles through the sleeves of two heavy, zipped (closed) parkas. It may be necessary to transport victims with certain injuries (i.e., spine injuries; unstable pelvis, knee, or hip dislocations) on a more rigid litter. Ski poles, stout tree limbs, or pack frames can provide a rigid support framework for such a device. For example, three curved backpack frames can be lashed together to form a platform (Fig. 34-12). Ski poles or sturdy branches then can be fastened to the frames for use as carrying handles,

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A

B Figure 34-7. A, Four-handed seat used to carry a person. In this technique, the upper body is not supported. B, Alternative four-handed seat that helps support the victim’s back. (From Auerbach PS: Medicine for the Outdoors:The Essential Guide to Emergency Medical Procedures and First Aid, 4th ed. New York, Lyons Press, 2003.)

and the platform can be padded with ground pads, sleeping bags, or a similar material. Combining a rope litter with a rigid litter can provide more strength and versatility. The rescuer fashions this type of litter by first building a platform of poles or limbs, using a blanket as in a rigid litter, and placing the victim in a sleeping bag on the platform. The patient and platform are wrapped and secured with a length of rope. Because a mummy sleeping bag is used to encapsulate the victim, this device is sometimes called a mummy litter. Although this type of litter offers improved support, strength, and thermal protection, careful thought must be given to the physical and psychological effects such a restrictive enclosure may have on the victim (Fig. 34-13). If long distances must be traveled or if pack animals are available, a litter may be constructed so that it can be dragged or slid along the ground like a sled. One such device is known as a sledge (Fig. 34-14). This litter is fashioned out of two forked tree limbs, with one side of each fork broken off. The limbs form a pair of sledlike runners that are lashed together with cross members to form a patient platform. The sledge offers a solid platform for victim support and stabilization. If sufficient effort is put into fashioning a smooth, curved, leading edge to the runners, a sledge can be dragged easily over smooth ground, mud, ice, or snow. Ropes also can be attached to the front of the platform for hauling and to the rear for use as a brake when traveling downhill.

Figure 34-8. Two-rescuer split coil seat.

A travois is a similar device that is less like a sled and more like a travel trailer (without wheels). A travois is a V-shaped platform constructed out of sturdy limbs or poles that are lashed together with cross members or connected with rope or netting. The open end of the V is dragged along the ground, with the apex lashed to a pack animal or pulled by rescuers. Although the travois can be dragged over rough terrain, the less smooth the ground, the more padding and support necessary for comfort and stabilization. A long pole can be passed through the middle of the platform and used for lifting and stabilization by rescuers when rough terrain is encountered. When victims are transported in improvised litters, especially over rough terrain, they should be kept in a comfortable position, with injured limbs elevated to limit pressure and movement. To splint the chest wall and allow full expansion of the unaffected lung, victims with chest injuries generally should be

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Clove hitch

Sport socks, hat, etc.

Figure 34-9. Improvised handled soft stretcher.

Figure 34-11. Improvising a stretcher from two rigid poles and a blanket or tarp.

Figure 34-10. Tying an improvised rope (nonrigid) stretcher.

Figure 34-12. Pack frame litter.Note that the sapling poles on the litter can be attached to the rescuer’s pack frames to help support the victim’s weight.

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PART FIVE: RESCUE AND SURVIVAL positioned so that they are lying on the injured side during transport. For a person with a head injury, the head should be elevated slightly, and for persons with dyspnea, pulmonary edema, or myocardial infarction, the upper body should be elevated. Conversely, when the victim is in shock, the legs should be elevated and the knees slightly flexed. Whenever possible, unconscious patients with unprotected airways should be positioned so that they are lying on their side during transport to prevent aspiration.1


RESCUE LITTERS

AND STRETCHERS

The image most often associated with rescue immobilization and transportation devices in the United States is that of a traditional tubular steel and chicken wire–netted basket, which came to be known as the Stokes basket. Although this apparatus was and still is ubiquitous, many may recall the Thomas, Duff, Mariner, Brancard Piguillem, Perche Barnarde, Neil Robertson, MacInnes, and Bell stretchers for their evolutionary and robust designs. Today there are a variety of devices that meet the following two primary wilderness medical needs: 1. Immobilization and protection of a patient during transportation 2. Safe, comfortable, and stabilized transportation of a patient to definitive care


DESIRABLE CHARACTERISTICS

OF A WILDERNESS STRETCHER

Figure 34-13. Mummy litter. (From Auerbach PS: Medicine for the Outdoors: The Essential Guide to Emergency Medical Procedures and First Aid, 4th ed. New York, Lyons Press, 2003.)

Figure 34-14. A “sledge.”

Peter Bell,2 rescue equipment historian and developer of Bell stretchers, has described several specific characteristics of a high-quality, useful rescue stretcher. Bell claims that a good stretcher should: 1. Be as strong and robust as possible, with materials compatible with the rescue environment 2. Be as lightweight as possible

Chapter 34: Litters and Carries 3. Have smooth edges that will not snag 4. Be devoid of small spaces that will trap or pinch fingers (rescuers’ and patients’) 5. Be large enough to provide strength, security, and comfort for the largest of persons when the device is in any position (horizontal, vertical, on its side, upside down, etc.) 6. Prevent worsening of injuries during use 7. Provide security for the victim regardless of his or her condition (e.g., slippery, wet, muddy) 8. Be comforting to the conscious victim 9. Be easy to use in the dark and in temperature extremes (very hot or cold) 10. Protect the victim from the environment (heat, cold, brush, rocks, etc.) 11. Be reliable for many years after many uses in extreme conditions 12. Be easy to carry and use when carrying a heavy, large person 13. Be portable (can be carried in a car, boat, plane, helicopter, etc.) 14. Be impossible to use improperly 15. Be easy to clean and sterilize


STRETCHERS In the interest of brevity and with some technical latitude, this discussion describes stretchers in four categories: basket-style, flat, wrap-around, and mountain rescue.

Basket-Style Stretchers The basket-style stretcher derives its name from its shape. The sides curve upward to protect the victim’s sides and to prevent the victim from rolling out. Most basket-style stretchers combine a steel frame (solid, tubular, or both) with a shell of either steel wire netting (“chicken wire”) or plastic. Many include wooden slats in the bottom to provide additional protection and support. Most likely, basket-style stretchers initially were adopted by wilderness rescue organizations because they met fundamental needs and were sufficiently robust to endure great abuse in severe terrain. The seminal basket-style stretcher, called the Stokes, first appeared in the late 1800s and likely got its name from the fact that it was designed to be used on naval and commercial ships to remove casualties from the “stokehold,” a room in which the boilers were stoked (Fig. 34-15). However, at least one source makes an unsubstantiated claim that the

Figure 34-15. Traditional tapered Stokes litter with leg divider. (Courtesy of Junkin Safety Appliance, Inc.)

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device was invented in 1895 by Charles Stokes.8 The significant influence of this device is reflected in the fact that the Stokes was the first commercially available basket-style stretcher in the United States. The original Stokes design included a leg divider meant to separate and support each leg individually. Many came to consider this configuration counterproductive when the use of long (16 × 72-inch [0.40 × 1.83-m]) backboards and other spinal, full-body immobilization devices became widespread, especially for early treatment of trauma. Most current designs of the Stokes basket-style stretcher have eliminated the leg divider to allow full immobilization of a patient on a long backboard, which can be inserted into the basket. The Junkin Safety Appliance Company manufactures several Stokes basket-style stretchers, including models that break into two pieces and models with and without wooden slats or leg dividers, that meet the more robust military specifications (MIL-L-37957 and RR-L1997) (Fig. 34-16). Although the traditional materials and design (i.e., tubular and flat, welded steel with a steel chicken wire covering) are still in use today, basket-style stretchers are more often constructed from tubular stainless steel or aluminum because of the added corrosion resistance, increased strength, and reduced weight. Manufacturers, such as Junkin and Ferno, offer basket-style devices in full rectangular and tapered rectangular shapes. Both are also available in break-apart versions for easy carrying. Narrower versions (usually 19 inches [0.48 m] wide, instead of 24 inches [0.60 m]) are available for use in confined spaces or caves, although cave rescuers rarely prefer any type of chicken wire litter. Because of the importance of portability in wilderness areas, the break-apart capability is an adaptation to nearly all styles and types of litters. Junkin manufactures a version of the Stokes stretcher completely coated with a plastic material called Plastisol, which provides nonsparking, nonconductive, and antistatic properties. Junkin suggests that this coating allows improved purchase (handgrip) on the litter and offers insulation from the temperature of the metal. A collateral benefit of the coating is that it extends the life and integrity of the steel chicken wire netting.

Figure 34-16. Break-apart Stokes litter with wooden slats. Many manufacturers also offer accessory straps or backpack devices that allow the rescuer to carry the litter halves on his or her back. (Courtesy of Junkin Safety Appliance, Inc.)

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Figure 34-19. International Stretcher Systems’ Yellow Jacket Basket Litter with flotation added. (Courtesy of International Stretcher Systems.)

Figure 34-17. Lifesaving Systems Corporation’s Model 404-F Medevac II stainless steel basket litter with optional flotation. (Courtesy of Lifesaving Systems Corporation.)

Figure 34-18. Ferno Model 71 Stretcher. (Courtesy of Ferno.)

Lifesaving Systems Corporation of Florida markets the Medevac II series of Stokes-style litters used widely by the U.S. Coast Guard. These devices are made from either a powdercoated stainless steel or titanium, which is 40% lighter (9 kg [20 lb] versus 14.5 kg [32 lb]). It also comes in a break-apart version (Medevac IIA) and is designed to include flotation for use in and around the marine environment (Fig. 34-17). In this device, the wood slats used on the original Stokes litter have been replaced with stainless steel reinforcements that run the full length of the litter; and smooth, plastic net mesh (with 1/2inch [13-mm] openings) replaces the chicken wire liner. Taking advantage of substantial improvements in polymer research, some manufacturers began producing a stretcher shell composed of rigid plastic instead of steel mesh. Ferno’s model 71 stretcher has an orange plastic shell wrapped around an aluminum frame and secured with aluminum rivets. Brass grommets in the plastic serve as attachment points for a lifting harness (Fig. 34-18). At half the weight of a traditional steel Stokes, this device offers protection from snags and obstacle penetration that cannot be provided by the wire netting of the Stokes. In addition, the plastic used is chemical resistant, and the molded underside runners make it slide smoothly over flat

ground, ice, and snow. Ferno offers a version with tow handles and a chain brake that is designed specifically for ski patrol applications so that a packaged victim can be “skied” down a slope or pulled along a snow-covered trail. The orange Ferno litter has a load limit of 270 kg (600 lb), but its usefulness in a vertical raise configuration depends on the integrity of the aluminum frame and the plastic shell; if one is compromised, both may fail. Because of this limitation and because of the lightweight materials used, bending or twisting the device should be avoided. International Stretcher Systems also builds a basket-style stretcher called the Yellow Jacket. It has a lightweight aluminum frame but uses a different approach for combining the frame with the shell. Its high-density polyethylene shell is similar to the shell in the Ferno model 71, but it is placed outside a full aluminum skeleton to facilitate sliding over the ground. Inside the stretcher, a spring-suspended victim “bed” that doubles as the victim retention system has been added to protect the victim from the internal frame members. This bed minimizes transport shock and features built-in shoulder straps, pelvic padding, a head and chin immobilizing harness, foot and ankle straps, and a large “double-security” Velcro body restraint flap that wraps around the victim. The stretcher weighs 40 pounds (18.2 kg) and has an engineered load rating of 2500 pounds (1136 kg) (Fig. 34-19). The Junkin model SAF-200-B includes parallel stainless steel top rails. The top tube is larger to allow comfortable handgripping and to provide an attachment for lifting bridles, and the smaller solid steel lower rail allows attachment of patient retention straps. The twin rail configuration keeps patient straps and lifting systems from interfering with each other and helps protect the attached materials from abrasion during use. Unlike the International Stretcher Systems device, the stainless steel frame in the Junkin stretcher wraps around the exterior of the basket, which is lined with a smooth-surfaced, permanently padded plastic shell. This design offers comfort for the victim but makes it difficult to slide on the ground because of the external, exposed steel frame members. The unit is heavy (weighing 14.5 kg, or 32 lb) but breaks apart for packing and marries well with a litter wheel to allow easier handling. Cascade Toboggan manufacturers the Model 200 Advanced Series of rescue litters (Fig. 34-20). These robust devices—

Chapter 34: Litters and Carries

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Figure 34-22. The Junkin Air Rescue Stretcher (SAF-350) was designed for use in Bell Jet Ranger helicopters.This lightweight, flat stretcher folds for easy storage but is not designed for long carries. (Courtesy of Junkin Safety Appliance, Inc.)

Figure 34-20. Cascade Toboggan’s Model 200 Advanced Series Rescue Litter with optional snow handles. (Courtesy of Cascade Toboggan Rescue Equipment Company.)

the litter). Four patient retention straps attached to the outermost rails, a patient shoulder strap, and integral lifting rings are supplied with the device. A slightly smaller, lighter, and less robust version, called the Bell Emergency Stretcher (discussed in the next section), also is available.

Flat Stretchers

Figure 34-21. Cascade Toboggan’s Professional Series Litter Skin that can be attached to many types of rescue litters for easy sliding across any rough or abusive surface. (Courtesy of Cascade Toboggan Rescue Equipment Company.)

common sights at many recreational ski areas—have a 5/8-inch (16-mm) stainless steel top rail that attaches to a composite basket. It is available in a break-apart version and integrates four 1-inch (25-mm) patient restraint straps into the basket. The device is compatible with both the CMC rescue Litter Shield and Litter Wheel, and weighs less than 18 pounds (8.1 kg) for the one piece version. The two-piece version is just a bit heavier. Cascade Toboggan also developed and manufactures the Litter Skin, an abrasion-resistant shell that can be quickly attached to many types of rescue litters to make sliding across any surface easier (Fig. 34-21). Bell Rescue Stretchers offers the Series 2 Ludlow stretcher, which is simply their strongest flat stretcher with deep basket sides added. This strong, stainless steel–framed design has folddown sides, which simplify access with a backboard. The sides can be completely removed to revert the device back to a flat stretcher. Other available variations on this theme from Bell include versions with shorter sides (the Otterburn), an open foot end (the Newark), and a steel plate welded into the bottom of the stretcher to help protect the victim (the Manchester). The Manchester weighs nearly 22.5 kg (50 lb) by itself. The manufacturer claims that the Series 2 models can all accommodate a long spine board and have been “proof tested” to between 500 and 720 kg (1102 and 1587 lb). The “bed” of Bell’s Series 2 stretchers is made of 14 polypropylene web straps that cross between the steel frame members. This webbing also passes through two movable stainless steel spinal supports (flat steel frame members that run the length of the caudal two thirds of

Flat stretchers are generally flat and have very short or no sides. Restraint straps or built-in tie downs serve as the physical means by which the victim is secured in the litter. Although the specific characteristics of these types of stretchers vary greatly (from extremely lightweight to high strength), generally they are used when specific benefit is derived from their low-profile shape. Although this style of stretcher has been modified to allow dragging or sliding (e.g., mountain rescue stretchers), the primary purpose of the flat design is to reduce weight and profile for carrying or for specific applications, such as loading into an aircraft. Although a simple, two-pole canvas litter is fine for use over short distances, uncomplicated terrain, or the battlefield (where haste is paramount), the lack of patient protection and immobilization capability limits its usefulness outside of the hospital or battlefield setting. A more modern version of this simple device is made of aluminum, folds for easy storage, and doubles as a long backboard. Another version is hinged at one end so that it can be spread along its long axis and slid under a patient on the ground with little movement or rolling. This “scoop” stretcher was commonly used by emergency medical service providers but has been supplanted by the use of long backboards. In the final analysis, both the military and aluminum iterations of the flat stretcher are intended for carrying a person short distances in an environment with few terrain obstacles or where complete security and immobilization are not required. Several successful varieties of flat stretchers have evolved over the years, including the Brancard Piguillem, the Junkin Air Rescue Stretcher (Fig. 34-22), and a few of the Bell stretchers that are categorized as flat for the purposes of this discussion. The Brancard Piguillem (Brancard is French for “stretcher” and Peguillem is a proper name) is a flat, old-style stretcher consisting of a canvas patient bed lashed to a steel and aluminum frame (weighing 14 kg, or 30 lb), which folds in half for easy carrying by one person. The design, which has evolved over the years in the European and British mountain rescue communities, includes a patient bed with a permanently attached, integral casualty bag lashed to the frame to protect and secure the victim. Full-length runners raise the stretcher a few inches above obstacles and allow for easy barehanded gripping. This folding, portable design with integral patient protection made the Brancard Piguillem popular with mountain rescuers and served as the impetus for the evolution of several of the current styles of mountain rescue stretchers.

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Figure 34-23. Life Support International’s Rescue Sled (manufactured by Switlik) is a unique, durable, and inflatable device that provides 225 lb (101 kg) of buoyancy and weighs under 20 lb (9 kg). Shown is the Rescue Sled with integral flotation devices inflated (one tube each side). (Courtesy of Life Support International, Inc.)

An interesting variation on the flat theme is the Rescue Sled Inflatable Rescue Litter manufactured by Switlik and distributed by Life Support International (Fig. 34-23). The Rescue Sled is an inflatable, flat litter made of coated ballistic nylon that offers 225 pounds (101 kg) of buoyancy and weighs less than 20 pounds (9 kg). The device can be lifted, paddled, towed, or slid, both in and out of the water. It may be inflated either manually or by a small carbon dioxide canister that comes with it. Uninflated, it packs easily into a medium-sized backpack or duffle bag. The integrated head restraints and body straps allow for securing a patient, and towing and lifting attachments simplify the process of moving the device when loaded. Although this device may not be best for all situations, its unique buoyancy and design characteristics make it attractive for many iceand water-related rescues. The Kendall Stretcher, from Bell Rescue Stretchers, has the same features as their Ludlow Stretcher without the basket sides (see the previous section). The Kendall has a stainless steel frame, integral lifting rings, a bed made of polypropylene web straps that cross between the frame members, color-coded patient retention (38-mm web) straps, and a detachable foot loop. The Kendall Stretcher can be used either side up; there is no top or bottom. A slightly less robust version of Bell’s flat stretcher is their Basic Emergency Stretcher. This device is smaller and lighter (weighing 5.2 kg, or 11 lb, 8 oz) and works well in commercial and industrial settings where severe terrain is rarely encountered. Although the manufacturer considers this stretcher to be a mountain rescue device, the MacInnes Mark 7 Rescue Stretcher is the latest in a long line of strong, user friendly stretchers from Hamish MacInnes, the founder of MacInnes Rescue Stretchers and member of the Glencoe (Scotland) Mountain Rescue Team. The designer’s aim was to develop a compact, versatile stretcher made from light, “space age” materials. The Mark 7 is 22 pounds (11 kg) complete, less than 5 cm (2 in) high (unfolded), constructed of abrasion-resistant titanium and composite materials, and can be folded for easy packing into isolated areas. It also includes a folding foot rest and head protector that double as handles.

Mountain Rescue Stretchers Mountain rescue stretchers are essentially stronger, more robust flat litters with runners or skis attached to the bottom for easy

movement over rugged terrain. Over the years, engineers and litter designers with mountaineering and rescue backgrounds have adapted rescue litter designs to meet specific practical needs of their environment. The result is the strongest and most robust platform available for patient treatment and transportation, but these benefits come at the cost of weight and size. The Thomas Stretcher is an early and beautifully simple example of the mountain rescue device. Invented in the United Kingdom in the 1930s by Eustace Thomas (no relation to Hugh Owen Thomas, who invented the Thomas “half-ring” splint), it consisted of wood (ash) runners, an aluminum frame, a canvas bed, and six or seven patient straps attached to the rails. It also had locking, tubular, retractable handles that stowed in the tubular rails.5 The Thomas Stretcher is still manufactured, with some modifications, by Bell Rescue Stretchers in the United Kingdom. In the late 1950s, Donald Duff, a pioneer of mountain rescue in Scotland, designed a stretcher with a steel tubular frame and no handles. Channeled steel runners extended along two thirds of the caudal end of the stretcher. It weighed about 13.5 kg (30 lb) and could be fitted with a wheel and undercarriage for easier movement over rocky terrain. Its profile was low and sleek, and the runners could be detached and the remainder folded in two for backpacking.4 Although they have almost completely been replaced by more modern designs, two basket-style mountain rescue stretchers that evolved in Britain and Europe over the first half of this century deserve mention. The Perche Barnarde (Perche is French for “perch” or “pole,” and Barnarde is a proper name) consists of a 2-m (7-foot) square section of steel tube from which a canvas casualty bag is suspended. The tube breaks into three pieces for easy carrying. The bag is attached to the tube at each end. Where the patient’s shoulders would fall, a spreader bar is placed to keep the bag open. From each end of the steel tube extend two removable, bicycle-type handlebars fitted with pads so that the handlebars can rest on rescuers’ shoulders. Although this device has been used successfully in many difficult mountain evacuations over the years, its limitations regarding patient comfort, protection, and immobilization are obvious. The Mariner consists of a canvas bed attached to a steel sledlike frame. The bed functionally resembles a reclining chair in that the patient sits flexed at the hips and waist with the lower legs supported by a canvas platform. The frame is rounded from end to end and includes two steel runners to deflect obstacles. Two adjustable handles extend from each end of the frame for carrying. Today, the Mariner is used by several U.K. mountain rescue teams and is noted to have contributed significantly to the evolution of the mountain rescue stretcher. The current British standard for mountain rescue stretchers includes two devices that are incredibly strong, durable, and, unfortunately, heavy. The Mark III Bell Rescue Stretcher (which weighs 24 kg, or 53 lb) and the model 6 MacInnes Rescue Stretcher (which weighs 22 kg, or 48 lb) (Fig. 34-24) are intended to survive years of use in extreme mountainous environments. Both have break-apart versions for easy packing into isolated areas, and both incorporate lifting rings, skids, and head guards.

Flexible, Wrap-around Stretchers A focus on improving stretchers for particular environments or situations has led to major developments in a number of litter design areas. It is difficult for a single device to excel in every

Chapter 34: Litters and Carries

Figure 34-24. MacInnes MK 6 Mountain Rescue Stretcher.Note the extending handles,folding head guard, and optional twin (solid) tires. (Courtesy of MacInnes Rescue Stretchers.)

situation because enhancing one capability or characteristic can be detrimental to another. For instance, it can be difficult to achieve a substantial increase in strength while decreasing overall weight. However, new innovative stretcher designs and materials allow structural flexibility to meet specific needs. Flexible, wrap-around stretchers can be folded, rolled, or otherwise compacted for storage and “wrap around” in that they contain the victim to provide protection, immobilization, and often sufficient support for vertical lifting. The Neil Robertson Stretcher was the impetus for this entire category of device. Adapted from a Japanese design by John Neil Robertson and first produced between 1906 and 1912, this wooden and canvas stretcher was originally made of bamboo and sewn by hand. The “Neil Rob” supplanted the Mansfield military stretcher in the United Kingdom and was first given the name “Hammock for Hoisting Wounded Men from Stokeholds and for Use in Ships whose Hoists are 2 feet, 6 inches in Diameter.”3 The Neil Rob consists of wooden slats that are covered with semirigid canvas and sewn the length of the stretcher. These slats wrap around the patient in mummy fashion, with arms in or out, providing protection without bulk. Full-body immobilization, protection, and a small cross section combine to produce a device well suited for use in small spaces or for situations in which the victim must be moved through a small opening.9 The most basic type of flexible, wrap-around stretcher has long been used by the military under combat conditions to quickly move casualties. London Bridge Trading Company manufactures several versions of a Quick Extrication Litter that integrates web handles and torso straps on an ultralight, coated nylon panel (Fig. 34-25). While in use by one person, it may look more like a drag sheet than a litter. But, by passing litter poles through the web handles, the device, which weighs less than 2 pounds (0.9 kg) and can almost be packed in a pocket, works well when spinal immobilization is unnecessary or can be provided separately. The Ferno LifeSaver Stretcher is a modern version of the traditional Neil Robertson Stretcher. It is 153 cm (60 inches) long and uses full-length 5-mm (0.2-in) ribs interwoven by 1000 denier nylon fabric to provide full-body splinting in a very narrow package. Five built-in restraints with forged steel buckles are integrated into the device, and stainless steel rings are used at the foot and head for vertical attachment points.

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Figure 34-25. Quick extrication, ultralight, nylon litters; six handle (left) and four handle (right). Designed for rapid movement of casualty by dragging (one person) or lifting and carrying. Note torso straps to secure patient. (Courtesy of London Bridge Trading Company, Ltd.)

Figure 34-26. Ferno Traverse Rescue Stretcher configured for horizontal lift. (Courtesy of Ferno.)

For situations requiring full-body protection for the victim without complex restraint systems, the Reeves Sleeve and Ferno Traverse Rescue Stretcher almost totally encapsulate the patient. When used in conjunction with a cervical collar and spinal immobilization, these devices provide environmental and mechanical protection while allowing the victim to be carried through narrow passages. The Ferno Traverse Rescue Stretcher (model UT2000) uses heavyweight Cordura nylon to cover a high-density polyethylene sheet that gives the device rigidity when wrapped around the patient (Fig. 34-26). This stretcher has an integrated adjustable, full-body harness to secure the patient in the device,

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Figure 34-28. Sked Rescue Stretcher system. (Courtesy of Skedco.)

Figure 34-27. Reeves Sleeve in use. (Courtesy of Reeves Manufacturing, Inc.)

padded straps in the shoulder and groin areas to make for a comfortable fit, and a foot strap that stops the patient from sliding down during vertical lifts. The Reeves Sleeve is a compact immobilizing stretcher suitable for hand-carry situations or vertical environments, but is not intended for vertical lifting (Fig. 34-27). The device uses a vinyl laminated nylon shell, slides over a full backboard, and depends on the backboard or short spinal immobilizer to provide rigidity. The company now makes a Reeves Sleeve Model 122 that was specifically designed to be lifted both vertically and horizontally. Skedco’s Sked stretcher provides wrap-around protection similar to the Neil Robinson, but a combination of shape and material, rather than integral slats, provides longitudinal rigidity (Fig. 34-28). Light and compact when stored in its packable case, the flexible, low-density polyethylene plastic litter wraps around the victim to form a rigid sleeve that is superbly compact for maneuvering in tight quarters. A half-length version is available for moving persons from areas that are too confined for a full-length device when flexing the victim at the hips might facilitate extrication. The hard and smooth plastic material can be easily dragged over a variety of surfaces and offers substantial protection from penetrating obstacles. Though the Sked stretcher provides spinal protection, the manufacturer recommends using an Oregon Spine Splint (Skedco) or similar device when cervical spine immobilization is necessary. External lift slings are included with the Sked to allow vertical or horizontal lifting, and flotation is available for use in a marine environment.

Figure 34-29. The Medical Devices International Immobile-Vac Full Body Mattress is a full-body vacuum splint that can be inserted into other litters. (Courtesy of Medical Devices International.)

Medical Devices International (MDI) makes the ImmobileVac Full Body Mattress, which is a full-body vacuum splint on which the victim is carried (Fig. 34-29). The vinyl-coated, fabric patient bed contains loose polystyrene (Styrofoam) beads similar to those in a beanbag chair. Once the victim is positioned on the mattress, a small hand pump is used to expel air from within it. This process creates a rigid, full-body splint that conforms to the victim’s shape. This “cocoon” immobilizes the spinal column and extremities while providing a comfortable platform. The mattress has integrated web carrying straps that can be used to carry the patient directly, or the mattress can be inserted into a basket-style stretcher for added versatility and strength. The use of a basket stretcher will be necessary for highangle rescue because the MDI device is not designed for vertical rescue by itself.

Chapter 34: Litters and Carries

Figure 34-30. CMC Rescue Mule II Litter Wheel with handles (manufactured by Traverse Rescue).This versatile device allows the wheel to be removed and stored inside the frame and is available without the handles. (Courtesy of CMC Rescue, Inc.)


TRANSPORTATION HARDWARE

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Figure 34-31. The CMC Rescue Litter Shield protects the victim from falling debris while allowing access to the head and face. It can also be inverted and placed in the litter to save space during storage. (Courtesy of CMC Rescue, Inc.)

ACCESSORIES

A number of wheeled devices can be attached to most basketstyle stretchers. These devices take the carrying burden off rescuers in nontechnical evacuations and reduce the load on low-angle haul systems. One example is the CMC Rescue Mule II Litter Wheel (Fig. 34-30), which incorporates a large, underinflated all-terrain vehicle tire into a lightweight frame that clamps to the underside of the litter. This single wheel is positioned under the center of gravity, and the rescuers walk alongside, or at each end of, the litter to steady and guide it, with the wheel carrying most of the load. When they encounter large obstructions, such as logs or trenches, rescuers simply lift the litter and continue rolling. One advantage of this device is that it reduces the number of rescuers required to move a litter safely over a long distance. When using this device, only two rescuers (one at each end) are required to control the litter, but more may be used as necessary. To meet a similar need, International Stretcher Systems employs a collapsible steel frame trailer (called the Anchor Man Trailer) with two all-terrain vehicle (ATV) wheels. With no axle between the wheels, the tires can be set to the outside of the frame for greater side-to-side stability or to the inside and under the frame to negotiate narrow trails or doorways. The drawbar end of the trailer is set up to receive either the T-bar handle, for towing by rescuers on foot, or a hitch adapter, for towing behind motorized vehicles. Skis can also be substituted for the wheels. Junkin markets several useful stretcher accessories, but at least one is notable. Junkin’s Comfo-Pad is designed to fit in all Junkin stretchers and is simply a pad on which the patient lies in the litter. It is made of 1/2-inch (13-mm) foam rubber with a durable, orange nylon cover and is held in place with hook-andloop–type fasteners. Because comfort is always an issue, this simple accessory can be quite helpful. MacInnes and Bell integrate steel wire head protectors in their mountain rescue stretcher designs. This feature is important where falling rock is a hazard. CMC Rescue markets a similar aftermarket device made of clear polycarbonate under the trademark CMC Rescue Litter Shield (Fig. 34-31). It protects the victim’s face from falling debris; allows for easy, rapid airway access; and can be moved out of the way because it hinges on the end of the litter. The shield stores compactly in the litter when not in use.

Flotation systems are available for some litters. Ferno, International Stretcher Systems, and Skedco each offer this option to make their devices safer and more versatile in swift or open water rescue situations. Most litter manufacturers offer specific packaging or methods for carrying their devices into isolated areas. For instance, London Bridge Trading Company’s Quick Extrication Litter, the Sked, and Ferno’s Traverse Rescue Stretcher can all be compacted and carried in by a single rescuer. Other manufacturers sell special backpacks or integral carrying harnesses for carrying half of their break-apart litters because of the greater weight.

Carrying a Loaded Litter An evacuation is defined as high angle or vertical when the weight of the stretcher and tenders (stretcher attendants) is primarily supported by a rope and the angle of the rope is 60 degrees or greater.7 This type of situation is often encountered when a rescue is performed on a cliff or overhang or over the side of a structure and usually requires only one or two tenders. In high-angle rescues, most often the stretcher is used in the horizontal position to allow only one tender and to keep the victim supine and comfortable. However, when the packaged victim and stretcher must be moved through a narrow passage or when falling rock is a danger, the stretcher may be positioned vertically. In a scree or low-angle evacuation, the slope is not as steep (less than 60 degrees), the tenders support more of the weight of the stretcher, and a rope system is still needed to help move the load. In this type of rescue, more tenders (usually four to six) are required, and the rope is attached to the head of the stretcher. The head of the litter is kept uphill during a low-angle rescue. In a nontechnical evacuation, tenders completely support the weight of the stretcher during a carry out. Generally, the terrain dictates the type of evacuation. If the stretcher can be carried without the support of a rope, it is a nontechnical evacuation. If rope is needed to support the load or to move the stretcher, it is either a low- or high-angle evacuation, depending on the angle of the slope. Carrying a litter in the wilderness is difficult and requires many resources. It takes at least six rescuers to carry a person in a litter a short distance (0.4 km, or 1/4 mile, or less) over relatively flat terrain. With six rescuers, four can carry the litter

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while the other two clear the area in the direction of travel and assist in any difficult spots. However, depending on the terrain and the weight of the victim, all six rescuers may be needed to safely carry the litter any distance. If the travel distance is longer, many more rescuers are required (Fig. 34-32).


PATIENT PACKAGING Patients (victims) on stretchers must be secured, or “packaged,” before transport. Packaging consists of stabilization, immobilization, and preparation of a victim for transport. Physically strapping a person into a litter is relatively easy, but making it comfortable and effective in terms of splinting can be a challenge. The needs of a person secured and transported in a litter are great and should not be overlooked or underestimated. The rescuer’s goals are as follows: 1. Package the person to avoid causing additional injury. 2. Ensure the victim’s comfort and warmth. 3. Immobilize the victim’s entire body in such a way as to allow continued assessment during transport. 4. Package the victim neatly so that the litter can be moved easily and safely. 5. Ensure that the victim is safe during transport by securing him or her within the litter and belaying the litter as necessary. Generally, proper patient packaging must provide for physical protection and psychological comfort. Once packaged in a carrying device, a person feels virtually helpless; thus, transport preparation must focus on alleviating anxiety and providing rock-solid security. With this in mind, rescuers must provide for the victim’s ongoing safety, protection, comfort, medical stabilization, and psychological support.6 Splinting and spinal immobilization are usually achieved by using a full or short backboard. The victim is secured to the board, and then the victim (on the board) is placed into the litter. When the immobilized patient is finally placed into the litter, adequate padding (e.g., blankets, towels, bulky clothing, sleeping bags) placed under and around him or her contributes to comfort and stability. During transport, victims like to have something in their hands to grasp, to have pressure applied to the bottom of their feet by a footplate or webbing, and to be able to see what is happening around them.6 Because persons are so vulnerable to falling debris when packaged in a litter, especially in a horizontal high-angle configuration, a cover of some type should always be used to protect the victim. A blanket or tarpaulin works well as a cover to protect most of the body, but a helmet (in the absence of cervical injury) and face shield or goggles are also options to protect the head and face from projectiles. Alternatively, a commercially available litter shield can be used and allows easy access to the airway, head, and neck (see Fig. 34-31). Because the head and neck usually require immobilization, the technique and equipment used to protect them should allow this. Remember also that the conscious victim desires an unobstructed view of his or her surroundings. Carrying a person in the wilderness often requires that the litter be tilted, angled, placed on end, or even inverted. In all these situations, the victim must remain effectively immobilized and securely attached to the litter, the immobilizing device within the litter, and any supporting rope be easily accessible and securely attached. Poor attachment can cause patient shift-

A

B

C

D Figure 34-32. Litter-carrying sequence.A, Six rescuers are usually required to carry a litter,but rescuers may need relief over long distances (greater than 0.4 km, or 1/4 mile).B, Relief rescuers can rotate into position while the litter is in motion by approaching from the rear. C, As relief rescuers move forward, others progressively move forward. D, Eventually the rescuers who are furthest forward can release the litter (peel out) and move to the rear. Rescuers in the rear can rotate sides so that they alternate carrying arms. Carrying straps (webbing) also can be used to distribute the load over the rescuers’shoulders.In most cases, the litter is carried feet first, with a medical attendant at the head monitoring airway, breathing, level of consciousness, and so on.

Chapter 35: Aeromedical Transport

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Figure 34-33. One 10-m (30-foot) web or rope can be used to secure a person into a litter.

ing, exacerbation of injuries, or even complete failure of the rescue system. Manufacturers have taken several approaches to securing a person within the litter. Most integrate a retention or harness system directly into the litter. However, a few require external straps to secure the victim to the device. Many users suggest that an independent harness be attached directly to the victim to provide a secondary attachment point in case any link in the attachment chain fails. When a harness is not available, tubular webbing, strips of sturdy material, or even rope can be used to secure the victim. One approach uses tubular webbing slings in a figure-8 at the pelvis and shoulders to prevent the victim from sliding lengthwise in the litter.

A 10-m (30-foot) piece of 5-cm (2-inch) webbing or rescue rope can be used to achieve the same goal (Fig. 34-33). The rope or web is laced back and forth between the rails of the litter in a diamond pattern until the victim is entirely covered and secure. Such a technique also easily incorporates a protective cover and support of the victim’s feet. Regardless of the techniques and equipment used, frequently checking vital signs (i.e., distal pulse and capillary refill) during transport can help ensure that strapping does not obstruct circulation.

The references for this chapter can be found on the accompanying DVD-ROM.

Aeromedical Transport Robert C. Allen

Rapid provision of appropriate definitive care to acutely ill and injured patients is a major goal of all emergency medical services (EMS) systems. The ability to rapidly transport and initiate treatment of severely ill or traumatized patients is important in decreasing morbidity and mortality. This is particularly germane to wilderness and environmental emergencies, for which medical resources are scarce, transport times to definitive care facilities are often prolonged, and terrain and weather conditions are inherently difficult. Aeromedical transport crews can deliver emergency medical care at the scene, and the time to definitive care can be greatly decreased. This maximizes the patient’s chance for a successful recovery.

35


AEROMEDICAL EVOLUTION Rapid evacuation of trauma victims from an injury scene to the location of definitive care is a modern concept with roots in antiquity. The New Testament documented an early instance of prehospital care and transport: “A certain Samaritan . . . went to him and bound up his wounds, pouring oil and wine, and set him on his own beast and brought him to an inn, and took care of him.”91 The greatest impetuses to the advancement of emergency care and transportation have been epidemics and wars.69 Before the

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classical Greco-Roman period, injured soldiers were often left on the battlefield to die. Later, Homer described the use of chariots to evacuate fallen warriors during the Trojan War.52 Napoleon’s forces devised horse-drawn carriages, or ambulance volantes, for the same purpose.59 North American Indians devised the travois, a litter that could be pulled by a person or animal to transport ill or injured persons.67 The U.S. Army began a similar practice during the Seminole War of 1835–1842 and used it again in the Civil War. Major Jonathan Letterman established the process of rapidly clearing wounded soldiers to a point behind the battle line where they could be further triaged to an expectant area for persons with mortal wounds, a local treatment area for the “walking wounded,” or a hospital if definitive care was feasible. The central concept was efficient access to surgery for victims of trauma. These developments were soon followed by invention of flying machines. In France, Richet had prophesied the potentials of air transport in 1869.69 This was before the first balloon airlift. The prophesy was validated the following year during the Franco-Prussian War when the first documented aeromedical evacuations took place. During the Prussian siege of Paris, 160 wounded soldiers were evacuated and transported by hot air balloon over enemy lines.93 In the United States, air evacuation took place soon after the Wright brothers flew in 1903.42 Grossman and Rhoades presented their idea of air transport of patients to the War Department in 1910, but the government refused to fund them. It was not until World War I that the U.S. military began to utilize aircraft to carry injured soldiers, and this occurred only rarely. However, the French transported patients as early as 1912 aboard Dorland ARII fighters converted to carry litters, despite the government’s objection to the concept of aeromedical transport: “Are there not enough dead in France today without killing the wounded in airplanes?”42 The United States began utilizing its first dedicated air ambulances in 1920, using the deHavilland DH-4A, followed by the Cox-Klemin XA-I. World War II saw widespread application of fixed-wing aircraft for evacuation. More than 1.4 million patients were transported from front-line hospitals to tertiary care facilities, with only 46 deaths en route.99 During this time, the concept of medical care during transport was implemented. In November 1942, the War Department began to train flight surgeons, flight nurses, and enlisted medical personnel for aeromedical transport.42 Also during 1942, Igor Sikorsky produced a rotor-wing aircraft, called a “helicopter,” which the army configured with external litters. It was used in an air evacuation for the first time in 1944 in Burma.39 Helicopters did not enjoy widespread use until more reliable and powerful machines became available. The Sikorsky S-51 and later the Bell 47-B were deployed over the rugged terrain and uncertain roads of Korea with great success to provide wide-scale evacuation of wounded soldiers to Mobile Army Surgical Hospital (MASH) units. Although only 11 dedicated “Medevac” helicopters were used, more than 17,700 casualties were evacuated. For the first time, injury victims could travel directly from the point of injury to definitive surgical care. This set the stage for Army helicopter evacuation (“Dust Off”) operations in Vietnam in 1962. With the Bell UH-1A Iroquois (“Huey”) under the leadership of Major Charles Kelly, the Army’s 57th Medical Detachment became known for the courage and hard work of flight crews, who flew despite dark-

TABLE 35-1. Mortality Rates and Evacuation Times During Major Wars CONFLICT

EVACUATION TIME (hr)

MORTALITY RATE (%)

World War I World War II Korea Vietnam

18–30 4–6 2–4 1–2

18.3 3.3 2.4 1.8

From Stewart RD: Trauma Q. 1985; May: 1.

ness, adverse weather, and enemy fire. Later, the Bell model UH1H was used to evacuate up to nine patients at a time by hoist from above a dense jungle canopy. By 1967, about 94,000 injured men had been evacuated.77 As air evacuation matured, the time from wounding to definitive care declined from 18 hours in World War I to between 1 and 2 hours in Vietnam.101 Although medical advances have contributed to improved survival, battlefield mortality has steadily declined from 18% in World War I to 1.8% in Vietnam, perhaps more because of rapid aeromedical transport to definitive care (Table 35-1). Unfortunately, emergency medical care for civilians greatly lagged behind the developments in the military. In the late 1960s, rescue efforts were more organized, skilled, and rapidly performed for a man shot in the Vietnam conflict than for a civilian injured on U.S. highways.69 Civilian ambulances were said to be no faster than taxis.90 Civilian transport began to change dramatically in the United States in 1966 when the National Academy of Sciences–National Research Council put forth the white paper “Accidental Death and Disability: The Neglected Disease of Modern Society” (U.S. Department of Health, Education, and Welfare). This document was the impetus for improving EMS systems through the country, and soon the civilian sector began to emulate the military model. Outside the United States, Germany and Switzerland had developed a network of helicopter and fixed-wing air evacuation and transport services that continue to provide rapid access to care from even the most remote areas.41 The first U.S. civilian aeromedical program was begun in 1969 as a joint effort between the Maryland State Police and the University of Maryland Center for the Study of Trauma (now the Maryland Institute for Emergency Medical Service Systems). Certain hospitals were designated as trauma centers, and victims of highway and other trauma were flown by police pilot– paramedic teams in a primary response role at the accident scene. Since 1970, the service has flown more than 199,000 missions.95 The modern-day U.S. Air Force (USAF) aeromedical evacuation system has its root in the Vietnam conflict, during which more than 406,000 wounded troops were aeromedically evacuated. Current USAF aeromedical evacuation crews are composed of flight nurses and aeromedical evacuation technicians. Experienced nurses and medical technicians are trained to be aeromedical crews at the USAF School of Aerospace Medicine, Brooks City-Base, Texas. This 5-week course includes aircraft configuration, air and ground safety, patient flight physiology,

Chapter 35: Aeromedical Transport aeromedical nursing considerations, and a 9-day survival course. Aeromedical evacuation crews are trained to move stable patients by fixed-wing aircraft distances ranging from a few miles to transoceanic flights. Physicians do not normally accompany aeromedical evacuation flights; patient care and medication are provided by prior physician orders and written protocols. U.S. military operations in Afghanistan and Iraq have led to significant changes in the USAF aeromedical evacuation system. Changes in military doctrine have resulted in the need to move seriously ill but stabilized patients over great distances by air. The requirement has led to development of dedicated critical care air transport (CCAT) teams, who fly with aeromedical evacuation crews to provide care for critical patients. CCAT teams include a critical care physician, critical care nurse, and cardiopulmonary technician. A formal training course in CCAT is given at the USAF School of Aerospace Medicine, Brooks City-Base, Texas.84 The trend toward formal CCAT teams has been mirrored throughout the world, with countries such as Great Britain, Germany, Japan, Australia, and Colombia developing and fielding CCAT capabilities.53,58 With development of faster and more powerful helicopters, reconfiguration of fixed-wing aircraft for aeromedical needs, enhanced knowledge of aeromedical physiology, and experience accumulated through more than 50 years of transport experience, the acceptance, utilization, and success of aeromedical transport are universal. The role of aeromedical transport in the wilderness setting continues to evolve as its importance in providing rapid emergency medical care and evacuation to sick and injured patients is recognized.


TYPES OF AEROMEDICAL TRANSPORT PROGRAMS

Hospital-based Programs The most ubiquitous type of program is hospital based. Helicopter service is often provided in primary (to the accident scene) and secondary (to the community hospital emergency department) response roles. In addition, many hospitals provide fixed-wing transport in a secondary response role for long-distance transports or when transport by helicopter is impractical. According to the Association of Air Medical Services (AAMS), in early 1994, there were more than 175 hospital- or health care provider–affiliated and 20 freestanding rotor-wing transport programs in the United States. These services transported more than 172,000 patients in 1993. Nationally, about 70% of all flights are interfacility transports, and 30% are flights from the scene.71 In a hospital-based transport program, the hospital frequently leases the helicopter from a vendor, who also supplies the pilots, maintenance, and fuel. The hospital has the responsibility for providing the medical crew and determining the configuration of the crew. In addition, the program directors are responsible for medical control and quality improvement. The hospital may choose to own the aircraft and contract with a vendor for operations or employ its own pilots and mechanics. In most cases, the helicopter resides on a helipad atop or near the hospital, and the crew, which may consist of a specially trained flight nurse, flight paramedic, and physician,

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is quartered in the hospital ready for immediate launch (see “Flight Crew”).

Non–Hospital-based Programs Non–hospital-based service is provided by an entity that may be supported by a consortium of hospitals, or it may be an independent corporation, ambulance service, or aviation fixed-base operator (FBO). The aircraft may be owned or leased by the entity or by an aviation contractor. Although this is not a common model for helicopter services in the United States, many fixed-wing services operate in this manner. A corporate airplane may be provided on demand for use in an air ambulance mode with its interior reconfigured, or a dedicated airplane may be provided with a custom-made air ambulance interior configuration, usually under a Supplemental Type Certificate (STC).

Public Safety, Police, or State Services The aircraft (usually a helicopter) may be owned and operated by a governmental agency such as the state highway patrol and operated under part 135 of the Federal Aviation Regulations (FAR). As in the Maryland model, flight personnel typically include police pilots and emergency medical technician (EMT)paramedics.

Military Assistance to Safety and Traffic Program The Military Assistance to Safety and Traffic (MAST) program was established to supplement the civilian EMS systems. Under this program, air medical evacuation services are supplied by active-duty military medical units to the extent that their training budgets allow, provided they can use actual patient transports instead of training exercises. The MAST mission is “secondary”; it is available only when its personnel and equipment are not being used in support of the unit’s primary mission. MAST may be requested by the local EMS or disaster management agency. Typical aircraft include the Bell UH-1 and Sikorsky UH-60 (Blackhawk). The medical crew usually consists of medical corpsmen. The MAST program may not compete with similar civilian services.

Other Military Resources The USAF provides aeromedical transport in support of U.S. military operations and some disaster situations. The formal aeromedical evacuation system run by the USAF is the largest in the world, able to move large numbers of stable and criticalstabilized patients over intercontinental distances. In fiscal year 2004, the USAF aeromedical evacuation system moved 28,496 patients (4543 of whom had battle injuries); about 5% of these patients were critically ill and required CCAT team support during flight. Other available resources include the Air National Guard and the U.S. Coast Guard. Many states and some counties have organizations (e.g., California Department of Forestry, Los Angeles County Sheriffs Department) that may be called on to assist in search and rescue (SAR) operations in preparation for aeromedical transport. Many other countries have analogous units; the Israeli Air Force, for example, operates a squadron that provides civilian and military rescue and evacuation services.

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PATIENT MISSION TYPES Primary Response In a primary response role, the aeromedical transport service responds to an accident scene or field location, usually at the request of police, fire, or local EMS personnel, and serves as the initial and sole mechanism of transport to the hospital. In this instance, the aeromedical crew may function as “first responders.” Helicopters are most suited to a primary response role. The required response times must be short (less than 10 minutes from call to takeoff); thus, the flight crew must be stationed at or near the launch site 24 hours a day. The service radius (“stage length”) is short (typically less than 50 miles), and crews need to be experienced in techniques for landing in proximity to obstacles, under poor conditions, and on uncertain surfaces. In prehospital situations, patients’ conditions vary widely, and often, little or no assessment or stabilization is performed before arrival of the flight crew. Medical personnel must possess a high degree of training and experience and should possess at a minimum EMT skills required for patient extrication and stabilization at the scene. It must be kept in mind that the availability of helicopter transport, particularly for on-scene response, may not affect the outcome of the patient. Several studies have found that helicopter transport does not significantly improve outcomes in areas where ground ambulance transport is readily available.10,15,81,83 The possible benefit to the patient must be measured against the risk to the helicopter crew, especially in poor weather conditions or during the night.

transplantation services, for which specialized crews and equipment may be required. In addition, aeromedical transport programs that provide SAR operations require specialized equipment and training.

Trauma Patients

In the secondary response role, a patient has already been transported by other means to a hospital where some degree of stabilization may have occurred. The aeromedical service transports the patient in the early stages of care from the emergency department of a hospital to a facility better equipped to offer definitive care. Response times required for this type of mission must be competitive with one-way ground transport times. Stage lengths are short to intermediate (150 miles). The transport vehicle is typically a helicopter, although in some remote and wilderness areas, fixed-wing services are also suited to this role. Flight crews used in a secondary response vary depending on the needs of the patient (see “Medical Mission Types”). The responding aeromedical service typically consists of flight nurses, paramedics, and in some cases flight physicians.

Trauma patients transported in the primary or secondary response modes may account for 20% to 60% of a hospitalbased helicopter service’s transport activity, depending on the hospital’s function and capability as a trauma center and the relationship between the aeromedical service and the community EMS and public safety network. A study of one urban setting noted that 20% of helicopter missions were to injury scenes, which were located at a mean distance of 14.4 miles from the hospital. Of patients transported, 19% had penetrating trauma, and 81% blunt trauma (66% from motor vehicle crashes). The most common organ system injuries involved the head (65%), extremities (39%), chest (31%), and abdomen (27%). The overall mortality of transported patients was 24%. The most common procedures required at the scene were endotracheal (ET) intubation (41%) and cardiopulmonary resuscitation (CPR) (18.7%). The most common life-threatening conditions were cardiac arrest (18.7%), airway obstruction (5.1%), cardiac tamponade (3.2%), and tension pneumothorax (1.7%).36 A multicenter study of blunt trauma victims transported by helicopter aeromedical services from both urban and rural environments found a mean trauma score of 13 (of 16), mean age of 29 years, and overall mortality rate of 15%.10 These and other studies indicate the need for skilled crews in the transport of trauma patients.105 Medical personnel must have the ability to assess the patient adequately to detect frequent in-flight complications and to intervene with appropriate procedures, including intravenous (IV) cannulation, ET intubation, CPR, chest decompression, and at times a surgical airway (Box 35-1). In wilderness areas, the flight crew must be skilled at victim extrication and operating in rugged terrain. They must be familiar with standard trauma care and the range of clinical entities most frequently seen in the wilderness setting. In addition, because resources may be limited and backup unavailable, they may be required to function semi-autonomously. For this reason, protocols and standing orders are valuable. Most important are training, skill, and judgment.

Tertiary Response

Patients with Cardiac Disease

Secondary Response

In a tertiary response, an inpatient who requires specialized services unavailable at the current facility or who requests relocation is transported to a new facility. Tertiary transports may involve helicopters or fixed-wing aircraft, depending on the level of urgency, stage length, and cost of transport. Commercial entities throughout the world specialize in this type of service.


MEDICAL MISSION TYPES The needs of different patient types may be categorized by medical problem; this in turn dictates the requirements of the aeromedical transport service. In most hospital-based helicopter programs, most patients transported are categorized as adult trauma, cardiac, or medical noncardiac. A number of programs offer or specialize in pediatric, neonatal, perinatal, and organ

Patients with cardiac disease most often are transported in a secondary or tertiary response role, by either helicopter or fixedwing aircraft. They typically account for 20% to 50% of an aeromedical service’s transport activity. The condition of these patients is often medically complex. Technologically sophisticated treatment modalities may include antiarrhythmics, vasopressors, inotropes, vasodilators, thrombolytic agents, cardiac monitoring, arterial and central venous pressure monitoring, pacemakers, implantable defibrillators, and intraaortic balloon counterpulsation devices.25,33,40,55 The flight crew must have sophisticated knowledge, expertise, and experience and may include a cardiac critical care nurse and a physician.

Patients with Medical, Noncardiac Conditions Patients with medical, noncardiac conditions, including those with cardiac disease, are most often transported in the second-

Chapter 35: Aeromedical Transport

Box 35-1. Trauma Care Aboard Emergency Medical Services Helicopters MECHANISM OF INJURY

Motor vehicle crash Fall Industrial or agricultural accident Gunshot or stab wound Burn Sporting accident Drowning Hypothermia PROCEDURES PERFORMED BY FLIGHT CREW

Endotracheal intubation Cardiopulmonary resuscitation Intravenous lines Central venous access Extrication and splinting Bladder catheterization Nasogastric tube insertion Venous cutdown Tube thoracostomy Cricothyrotomy Pericardiocentesis Antishock garment application

ary or tertiary response mode by either helicopter or fixed-wing aircraft. This group consists largely of patients with acute neurologic disease or shock or those who require assisted ventilation.45 The spectrum of potential in-flight challenges includes cardiovascular problems, arrhythmias, hypotension, respiratory difficulties requiring acute airway management, seizures, and alterations in level of consciousness. The flight team must be able to manage an airway and operate a ventilator. Additional considerations relate to the cabin environment and need for pressurization if hypoxemia is present, if barotrauma is likely, or if trapped gas exists, as well as the need to predict the requirement for and manage finite oxygen resources in flight.

Pediatric Patients Pediatric patients may have traumatic or medical conditions.11,48 In a study of 636 pediatric patients transported by air in the Salt Lake City area, 57.5% were transported by helicopter and 37.5% by fixed-wing aircraft, with a mean stage length of 207 miles (helicopter, 82 miles; fixed-wing, 452 miles). Less than 1% of flights were from the scene. The patient ages ranged from 3 weeks to 16 years, with 45% younger than 1 year. Trauma was the most common diagnosis (15.3% had head injury, 9.3% multiple injuries), followed by neurologic illness (24.2%), respiratory failure or infection (20.1%), gastrointestinal or genitourinary problems (10.2%), metabolic disease (9.2%), cardiovascular disease (6%), and general pediatric surgical problems (5.7%). The overall mortality rate was 7%.68 Many of the considerations for pediatric transport are similar to those for adults, especially with older children. Infants may require an incubator, however, and flight crews must be experienced in caring for infants and children. Specifically, knowledge of pediatric advanced cardiac life support skills, including pediatric drug dosages, airway sizes, and fluid management, is essential.

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Perinatal Patients The need for expedient evaluation, preparation, and transport of the obstetric-gynecologic patient is increasing. Types of problems include ectopic pregnancy, pelvic inflammatory disease, toxic shock syndrome, abnormal fetal presentation, multiple gestation, diabetes in pregnancy, placenta previa, abruptio placentae, disseminated intravascular coagulation, preeclampsiaeclampsia, and preterm labor. The decision to transport patients in advanced preterm labor should be based on such factors as distance between hospitals, time required to cover the distance, personnel available for the transport, gestational age, and speed with which labor has progressed. The flight crew must be knowledgeable about these problems and comfortable with their treatment in order to ensure a favorable outcome for both mother and child.

Neonates Neonates have unique anatomy and physiology, and the diseases that affect them require specific knowledge and skills by those involved in their transport. Specific issues include newborn assessment, including assignment of an Apgar score, airway clearance, temperature, homeostasis, and familiarity with neonatal resuscitation.3 Access to references concerning neonatal emergency drug dosages should be available.2 The ability to perform umbilical vein catheterization is an important skill for any member of the transport team involved in neonatal care. In addition, knowledge of fluid, electrolyte, and glucose requirements is essential.53,60 The flight crew involved in the transport of a neonate often includes a neonatal nurse and a neonatologist.

Search and Rescue Wilderness SAR is a unique aspect of aeromedical care and transport that requires significant training and expertise. Most dedicated aeromedical aircraft in the United States are not well suited for SAR operations (see “Aircraft for Search and Rescue”). Most standard aeromedical crews are not trained in SAR techniques. Many aeromedical helicopters and some fixedwing aircraft become involved in SAR activities, however, and it is important to be familiar with SAR techniques. In addition, outside the United States, persons providing aeromedical transport are frequently involved in SAR activities (see Chapter 32). The keys to a successful SAR operation include proper communications, transport, evacuation, and medical treatment, in the setting of favorable weather conditions and topography. The helicopter, equipped with a hoist and winch, is one of the most effective means of providing SAR in the wilderness setting and is essential in mountainous regions. A long delay between the time of the accident and the call for assistance, combined with a serous injury, adversely affects patient outcome. Helicopters are helpful in various SAR activities, including low-altitude search activity, search area evaluation, and movement of supplies and equipment. They may be the only means of extrication and rescue from the scene. Fixed-wing aircraft are also useful for search and can provide secondary transport, especially when long distances are involved. The U.S. Air Force routinely uses helicopters and fixed-wing aircraft for long-distance SAR operations. Fixed-wing aircraft often arrive at the scene first and may deploy pararescue specialists (“PJs”) by parachute. If the rescue site is over water, the aircraft may also deploy an inflatable boat with motor and rescue equipment. The PJs and their survivors are then

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Figure 35-1. MH-60G Pave Hawk hoisting a para-rescuer during a search and rescue exercise. A variant of the UH-60 Blackhawk, the Pave Hawk is flown by U.S. Air Force rescue squadrons. Modifications include forward-looking infrared equipment, night vision–compatible cockpit lighting, terrain and navigation radar, air-refueling probe, auxiliary fuel tanks, and hoist. (Courtesy U.S. Air Force.)

recovered by surface vessels or by rescue helicopters that have been refueled aerially in order to reach the rescue site (Fig. 35-1). This capability permits the rapid deployment of rescuers while allowing the most expeditious recovery of survivors and their delivery to definitive care. These services are on alert for all space shuttle launches to provide SAR support in the event of a mishap. In the United Kingdom, the Royal Air Force operates a helicopter SAR service that flew 1490 missions from 1980 to 1989, almost all of which involved vacationers along the coasts or in the mountains.63 The Danish helicopter rescue service was founded in 1966 and uses a Sikorsky (S-61) helicopter. Since 1973, its crew has included a physician trained in aerospace medicine and helicopter transport. From 1973 to 1989, it flew 5733 missions, 2075 of which involved direct medical intervention. The most frequent problems were abdominal trauma and cardiopulmonary diseases.112 In the high Alps, more than 90% of all rescues are performed using helicopters (3000 per year).6 Of these, 5% are combined rescues; that is, the helicopter carries the rescuers below cloud level, near the site of the accident. Only 5% of mountain rescues are purely ground rescues, mainly necessitated by visibility.89 Currently, a network of SAR systems extends throughout the Alps. In some countries (France, Italy, Germany, Austria, and Spain), air rescues are managed partially or totally by the army or the state. The aircraft most often used for this purpose are the Alouette III, Lama, Ecureil (French), Bolkow 105, 117 (German), Augusta AK 117 (Italian), and Bell (United States). In Switzerland, the rescue system in remote terrain is managed by the Swiss Alpine Club and three air rescue companies, Swiss Air Rescue (REGA), Air Glaciers, and Air Zermatt. Switzerland may be unique in that its 18 strategically placed helicopter rescue bases allow an aircraft to reach any accident scene within 15 minutes of takeoff. Since the foundation of REGA in 1952,

Figure 35-2. Helicopter rescue in extremely difficult terrain. (Courtesy P. Bärtsch, MD, and the Swiss Alpine Club.)

more than 150,000 patients have been transported by either fixed-wing aircraft or helicopter. Up to 8000 patients (5500 from accident scenes) are transported by helicopter every year. Twenty percent of these rescues require a winch, with one third of all winch operations occurring in accident sites that are difficult to reach.31 More than 75% of all persons rescued by winch were thought to have injuries requiring physician assistance at the scene. Eighty percent of all Swiss air rescue missions are physician assisted, and 20% have a paramedic in charge. All the physicians and rescue crews are physically fit and trained in alpine techniques because two thirds of all rescue missions performed from 1990 to 1993 were in topographically remote and difficult terrain (Fig. 35-2). Difficult helicopter SAR operations are those that involve low visibility, strong winds, night missions, high-angle rescues, and long-line hoist operations (extension of the hoist cable up to 120 m [394 feet]). In addition, in mountainous regions, power cables and transport cables present considerable risks. In all cases, the risks to the flight crew (as well as to the patient) must be weighed against the degree of injury and risk for further morbidity. The U.S. Air Force, Army, Navy, and Coast Guard equip and train groups to operate in these hostile rescue environments. Helicopters are frequently equipped with precision navigation systems and night vision, forward-looking infrared (FLIR), and thermal imaging equipment. The intense training and specialized equipment permit rescue operations under much more demanding conditions than those encountered by civilian services. Of the military services, only the U.S. Coast Guard has a primary mission of civilian SAR; Army, Navy, or Air Force groups may be requested to assist in civilian rescues in areas where they are available.

Chapter 35: Aeromedical Transport An increasing number of people participate in alpine sports, including mountain climbing, downhill skiing, mountain biking, and paragliding.33 A typical representation of the type of mountaineering accidents experienced in the Swiss Alps is shown in Table 35-2. In addition to SAR in mountainous regions, aeromedical rescue presents great challenges to the

TABLE 35-2. Mountaineering Accidents in the Swiss Alps, 1992 (N = 1845) ACTIVITY

PATIENTS RESCUED (n)

Delta gliding Paragliding Off-slope skiing Ski touring Mixed climbing Rock climbing Hiking

18 196 35 238 456 178 723

From Dürrer B, Hassler R, Mosimann U: Mountaineering accidents in the Swiss Alps and rescue activities of the Swiss Alpine Club, 1992.

A

771

medical and flight crews involved in rescues from sea and white water, floods, vertical rock faces, and avalanches. Medical treatment of the survivors should begin immediately at the site of the accident unless weather conditions are deteriorating or the scene is inherently unsafe. If a hoist extraction is needed, the patient with potential multisystem trauma should be evacuated by a rescue net or basket (Stokes) litter with careful spinal immobilization. A tag line attached to the litter prevents spinning during hoist operations. The tag line should be attached with a weak link so that the tag line will break away if the litter becomes uncontrollable. Persons with minimal or isolated injuries may be hoisted by a jungle penetrator (Fig. 35-3), rescue basket, or other dedicated hoist device. If a hoist device is not available, the victim may be hoisted by climbing harnesses or rescue belts.30 The climbing harness or belt should be carefully inspected to make sure that it has not been damaged in the mishap, that it will withstand the strain of the hoist operation, and that it can be safely attached to the hoist cable. The extent of medical treatment rendered on site before extraction depends on many factors, including the victim’s condition, scene safety, medical supplies available, medical skill of the rescuers, weather conditions, aircraft loiter time, and flight time to definitive care. Good communication between the flight

B

Figure 35-3. A, Jungle penetrator used as a hoist device on most military rescue helicopters. The streamlined shape allows it to slip through dense tree canopies to reach the ground. A foam flotation collar can be attached, making the penetrator buoyant. B, Jungle penetrator rigged for hoist.The seats are flipped down, and the safety straps are pulled out from their stowed position and passed over the head and under the arms of the victim, who then straddles one of the seat paddles. Although the penetrator has three seats, usually only one or two persons are hoisted at a time. (Courtesy Robert C. Allen.)

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Figure 35-4. Stanford LifeFlight MBB BK-117. (Courtesy Geralyn Martinez.)

crew and the rescue team is essential to the decision-making process. Aeromedical crews involved in mountain rescue need to have a thorough understanding of the unique medical problems frequently found in high-altitude rescue situations.


AEROMEDICAL AIRCRAFT

Figure 35-5. U.S. Coast Guard HH-60J Jayhawk helicopter in low hover over water, preparing to lower hoist cable to the rescue swimmer. Note the extensive spray under the aircraft. The Jayhawk, a variant of the UH-60 Blackhawk, is a medium-range helicopter used for search and rescue, drug interdiction, and maritime law enforcement. (Courtesy U.S. Coast Guard.)

Many different types of aircraft can be adapted to the air ambulance role. Each type has its strengths and weaknesses. On the other hand, not all aircraft are well suited for SAR in wilderness areas. Matching the physical and flight characteristics of the aircraft to the needs of the mission is vital. In many circumstances, compromises must be made because of aircraft availability. Rescuers must consider the physical characteristics of the aircraft when caring for a victim in flight.

and MH-53, there is enough room to work on multiple patients. Even on relatively large (by civilian standards) military helicopters, however, such as the Coast Guard HH-60J Jayhawk (Fig. 35-5), space for patient care can be at a premium. Cabin space can be more generous in fixed-wing aircraft. Cabin-class airplanes, such as the Beech King Air and Piper Cheyenne III, provide an aisle and capability to carry more than one patient and additional crew or family members. However, even in large military aircraft such as the C-130, carrying multiple patients with equipment and supplies can still result in a remarkably crowded cabin.

Cabin Space

Access for Patient Loading

Cabin space should be considered not only in terms of total interior volume in cubic feet, but also with regard to floor space, headroom, and the ergonomics of cabin layout. Ample headroom should be available for the patient to lie comfortably on a secured stretcher and for access by two crew members to all parts of the body. Specifically, access to the head is needed for intubation, the chest for CPR, and the extremities for monitoring perfusion. Some helicopters, such as the Aerospatiale AStar/TwinStar and the MBB BO-105, provide ample upper body access but only limited lower body access while in flight. The relationship of flight crew members when seated (and secured by seat belts) in proximity to the patient is important. The ideal configuration places one medical crew member at the patient’s head for airway management and verbal interaction and one at the patient’s side to monitor vital signs and perform necessary non–airway-related procedures. This arrangement is typified by the MBB BK-117 helicopter (Fig. 35-4). Although some rotor-wing aircraft, such as the BK, are theoretically capable of transporting two patients, this greatly increases demands on the flight crew and the aircraft and diminishes access to both patients. Policies and procedures regarding two-patient transport in these aircraft should be carefully considered. In some large helicopters, such as the CH-46, CH-47,

The cargo door should be wide enough that the patient’s stretcher can be maneuvered into the aircraft without undue tilting, and it should be positioned comfortably near stretcher height to obviate the need for strenuous lifting during ground loading. Standard door configurations on many aircraft do not meet these needs. The “clamshell” doors on an MBB BK-117 helicopter and the oversized cargo door on a Gulfstream Commander 1000 work well for patient loading (Fig. 35-6).

Useful Load One of the most important considerations for a given patient transport is the aircraft’s useful load. This difference between the maximum takeoff weight and the basic empty weight is a reflection of the load-carrying capability. In most EMS helicopters, the useful load ranges between 1500 and 2800 pounds (680 and 1270 kg). On-board avionics, medical equipment, fuel, and crew weights must be subtracted from this value to yield the maximum allowable patient weight (Fig. 35-7). Fuel weighs 6 pounds (2.7 kg) per gallon; a twin-engine helicopter may burn 70 gallons (265 L) per hour (420 pounds [190.5 kg] per hour), requiring it to carry 600 pounds (272.1 kg) or more fuel for a 30-minute-radius flight (with 30-minute reserve). Thus, it becomes evident that a flight crew of three weighing a total of

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helicopter performance. Density altitude (a factor of the air temperature and the pressure altitude) is critical in the performance of helicopters in mountain regions. High altitude combined with hot weather can seriously degrade the performance of even the most powerful helicopters.

Weight and Balance

Figure 35-6. MBB BK-117 with rear clamshell doors open.(Courtesy Susan Lockman, Stanford Lifeflight.)

500 pounds (226.8 kg) with a full load of fuel, oxygen, and medical gear may not have the capability to carry even a small patient, especially on a hot day when the helicopter’s performance (lift) is reduced. This consideration can become critical on flights from the accident scene, where terrain obstacles may require vertical takeoff and climb-out, demanding maximum

Not only must the weight of the loaded aircraft remain at or below the maximum allowed takeoff weight for that aircraft, but also the center of gravity (CG) must lie within fore-and-aft limits established by the manufacturer. Each loading configuration places the CG in a unique position, which must be calculated by the pilot before flight, or the flight characteristics may be adversely affected, compromising safety. This consideration may dictate where certain pieces of medical equipment, such as oxygen bottles, may be placed or where heavier crew members must sit. On flights from the accident scene, the patient’s weight is approximated before departure. With pressure to hasten departure, accurate weight and balance calculations are difficult. The aircraft used must have enough margin in the CG envelope that CG limits are not easily exceeded for the given mission profile.

Cruise Speed One of the most basic reasons for transporting a patient by air is to take advantage of the greater speed of aircraft compared with ground vehicles. This allows the patient earlier arrival at the destination and minimizes time spent out of the hospital.

Maximum take-off weighta

____________

weightb

– ____________

Less basic empty

boardc

– ____________

Less pilot and crew

– ____________

geard

– ____________

Less fuel on

Less medical

Maximum “patient payload”

= ____________

aMaximum

take-off weight is certificated for each aircraft type and can be found in the operating manual. bBasic

empty weight includes added avionics, permanent equipment, fluids, and unusable fuel. It is different for each aircraft and is recorded in the aircraft’s operating manual. cThe

quantity of fuel on board depends on the mission needs. Divide round-trip distance by cruise speed to yield time en route. Add time for warm-up, climb, approach, and a 30-minute reserve (VFR) to yield total engine time. Multiply total engine time by rate of fuel consumption to yield total fuel consumed. Fuel weight 6 lb/gal. dMedical

gear includes carry-on and nonpermanent items.

Figure 35-7. Weight calculation aboard aircraft.

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TABLE 35-3. Helicopters Frequently Used for Aeromedical Transport HELICOPTER Bell 206L-3 AStar 350D TwinStar 355F1 MBB BO-105 CBS Agusata 109A II Bell 222UT MBB BK-117 Sikorsky S-76 Dauphin 2

CRUISE SPEED (mph)

ENGINE

SHP

USEFUL LOAD (lb)

SERVICE CEILING (ft)

RANGE (mi)*

130 140 147 145 163 152 160 167 161

SE-T SE-T TE-T TE-T TE-T TE-T TE-T TE-T TE-T

650 615 420 each 420 each 420 each 684 each 650 each 650 each 700 each

1,950 1,868 2,391 2,732 2,605 3,376 2,645 4,700 4,118

20,000 15,000 13,120 17,000 15,000 15,800 17,000 15,000 15,000

325 379 368 334 359 380 368 550 564

*Range includes fuel for warm-up, taxi, climb, and 30-minute reserve. SE-T, single engine, turbine; SHP, shaft horsepower; TE-T, twin engine, turbine. Data from Collins RL, et al: Flying 1985 Annual and Buyer’s Guide. New York, Ziff-Davis, 1985; and 1987 Hospital Aviation Directory. Hosp Aviat 1987;6(4):8.

Not only do aircraft have a speed advantage, but they can also travel in a straight line from origin to destination without the curves and deviations present in surface travel. For an aircraft to compete with a ground vehicle in speed in a primary or secondary response mode, it must be at least twice as fast as an ambulance because the helicopter must fly round trip (outbound to destination and inbound with patient) in the time that the ambulance would travel one way. This is possible with most EMS helicopters, unless (1) the referral location has no suitable landing area (necessitating a time-consuming transit of crew and stretcher to and from the location), (2) ground “packaging” times for the flight crew with the patient are excessive, or (3) an ambulance has a clear, straight highway as a means of alternative transport. Most EMS helicopters are capable of attaining 120 to 150 mph (193 to 241 km/hr) over the ground, although a headwind or tailwind may hinder or improve these figures (Table 35-3). Piston twin-engine aircraft have a cruise speed range of 220 to 275 mph (354 to 443 km/hr), turboprop aircraft of 300 to 385 mph (483 to 620 km/hr), and jets of 400 to 535 mph (644 to 861 km/hr) or more.24,78

Range Aircraft range is limited by the amount of fuel, which is a function of fuel tank capacity and useful load. In most cases, a tradeoff is made between payload and fuel; the more weight in fuel, the less weight in passengers (or patients). The maximum time aloft can be calculated by dividing usable fuel on board by rate of fuel burn per hour at cruise speed. Multiplying maximum time aloft by cruise speed yields the maximum range. The Federal Aviation Administration (FAA), under FAR part 91.23, requires that a 45-minute fuel reserve remain at the conclusion of all flights conducted under instrument flight rules (IFRs), and a 30-minute reserve under visual flight rules (VFRs). Most EMS helicopters operate under VFRs, whereas most fixed-wing operations are IFRs. Because helicopters typically fly to and from a point at which refueling is not available, round-trip fuel must be carried; this effectively limits the customary radius of operation to about half the range (less required reserves). Although it is possible to refuel en route to an airport, this adds to the flight time. Therefore, helicopters typically operate within a radius of 150 miles (241 km) or less, unless the transport is oneway outbound or unless refueling at the destination is feasible.

Fixed-wing aircraft operate from airport to airport; thus, the radius of operation is closer to the maximum range with reserves. Many fixed-wing aircraft are capable of ranges in excess of 1000 miles, with some jets able to travel more than 2000 miles without refueling.

Pressurization The partial pressure of oxygen in the atmosphere declines with increasing altitude so that at 5486 m (18,000 feet) it is one half that at sea level. Part 91.32 of FAR requires the use of supplemental oxygen for the pilot at flight altitudes above 3810 m (12,500 feet) for longer than 30 minutes.34 Above 4267 m (14,000 feet), supplemental oxygen must be used by the pilot and all minimum required flight crew at all times. Technically, a medical flight crew member is not a required minimum crew member for the operation of the aircraft; neither is the copilot of an aircraft operated under FAR part 135 and certified for single-pilot operations (as with most aeromedical aircraft). Thus, the medical crew member is not required to wear supplemental oxygen, although doing so would be prudent, especially for smokers. At altitudes greater than 4572 m (15,000 feet), in addition to the above requirements, each occupant must be provided with supplemental oxygen (although there is no legal requirement to use it). The effects of hypoxia with increases in altitude are more pronounced in patients with lung disease and preexisting hypoxia; this necessitates supplemental oxygen at much lower altitudes. Supplemental oxygen at night will enhance night vision even at altitudes below 3810 m and should be considered for the flight crew, based on operational requirements. To eliminate the need to provide supplemental oxygen, pressurization is available in many larger, fixed-wing aircraft (Table 35-4). A pressurized aircraft is able to pump air into the cabin to maintain a pressure differential between the cabin and outside air, generally 4 to 8 pounds per square inch (PSI). This allows the cabin atmosphere to be maintained at or below the equivalent of a 2438-m (8000-foot) altitude, despite actual altitudes of 9144 m (30,000 feet) or higher.53,70 Pressurization obviates the need for supplemental oxygen for crew members and nonpatient passengers, but passengers with lung disease may still require it. Also, by limiting the drop in cabin pressure that occurs with altitude, changes in trapped gas volumes, such as in ET tube cuffs, air splints, and the gastrointestinal tract, can

Chapter 35: Aeromedical Transport

775

TABLE 35-4. Fixed-Wing Aircraft Used for Aeromedical Transport AIRCRAFT Seneca III Baron 58TC Cessna 402C Navajo 350 Cessna 414 Cessna 421 Cessna 441 Cheyenne II Cheyenne III MU-2 King Air F90 Commander 1000 Citation I Lear 25D

CRUISE SPEED (mph)

CABIN

ENGINE LOAD (lb)*

USEFUL CEILING (ft)

SERVICE (ft)

RANGE (mi)†

TAKEOFF (ft)‡

221 277 245 250 258 277 330 293 347 317 309 323 410 509

NP NP NP NP P P P P P P P P P P

TE-P TE-P TE-P TE-P TE-P TE-P TE-T TE-T TE-T TE-T TE-T TE-T TE-J TE-J

1,921 2,447 2,774 2,533 2,386 2,807 4,124 4,053 4,448 3,975 4,383 3,965 5,222 7,150

25,000 25,000 26,900 24,000 30,800 30,200 35,000 31,000 35,000 27,300 31,000 30,750 41,000 51,000

721 1,150 1,164 1,200 1,300 1,522 2,195 1,275 1,789 1,412 1,315 2,149 1,500 1,600

1,250 2,700 2,200 2,200 2,600 — — 2,500 3,200 — 2,900 3,000 4,000

*Useful load excluding avionics, fuel, passengers. †Range estimated at cruise speed, less 45-minute reserve. ‡Approximate nonbalance-field takeoff length. NP, nonpressurized; P, pressurized; TE-P, twin engine, piston; TE-T, twin engine, turboprop; TE-J, twin-engine, turbojet/turbofan. Data from Collins RL, et al: Flying 1985 Annual and Buyer’s Guide. New York, Ziff-Davis, 1985; 1987 Hospital Aviation Directory. Hosp Aviat 1987;6(4):8; and McNeil EL: Airborne Care of the Ill and Injured. New York, Springer-Verlag, 1983.

be decreased or eliminated. Special categories of patients include those with dysbarism. Exposure to increased altitude, with its concomitant decrease in ambient pressure, should be avoided. If possible, sea-level ambient pressure should be maintained when transporting these patients. On the other hand, most helicopters are nonpressurized and generally fly at lower altitudes, where altitude-related hypoxia is unlikely. One exception occurs in mountainous regions where altitudes required to rescue victims or cross mountain passes may exceed 3658 m (12,000 feet). Reasons for transporting patients at higher altitudes include terrain avoidance, the need to surmount adverse weather (which usually occurs within 6096 m [20,000 feet] above ground), and greater speed and fuel efficiency at higher altitudes.

unable to land and take off safely on these strips. Thus, when transport from a rural location with a short runway is requested, it is important to determine the capability of the aircraft being used. Piston twin-engine aircraft can usually operate safely from a 762- to 914-m (2500- to 3000-foot) strip but may have difficulty with 610 m (2000 feet); turboprop airplanes require 762 to 1067 m (2500 to 3500 feet); and jets usually require runway lengths of 1220 m (4000 feet) or more.70 The takeoff roll for airplanes increases with increasing temperature and airport altitude; on a hot day, many airplanes may be incapable of taking off from a short runway if heavily loaded. In winter conditions, operating on icy runways may pose a safety hazard for braking. Turboprop airplanes and jets have a reverse thrust mode that can slow the aircraft on rollout without braking.

Service Ceiling

Weather Operations

The service ceiling is the maximum altitude at which an aircraft can still maintain a rate of climb of 30.5 m (100 feet) per minute. This ceiling is important in predicting an aircraft’s ability to climb above adverse terrain and weather and in taking advantage of favorable winds aloft to maximize ground speed. In the western United States, mountainous areas require flight at least 610 m (2000 feet) above the highest terrain along the route of flight, which means a 3658- to 4877-m (12,000- to 16,000-foot) service ceiling. These altitudes restrict most helicopters and require use of supplemental oxygen in nonpressurized airplanes. Flight operations that typically require flight at these altitudes should have access to aircraft with sufficiently high service ceilings and pressurization.

Runway Length Although not a factor in helicopter operations, runway length restricts certain fixed-wing aircraft from landing. Most airports in rural areas have runway lengths between 610 and 1220 m (2000 and 4000 feet). Higher-performance airplanes usually have progressively longer runway requirements and may be

Adverse weather conditions that may affect a given flight include restrictions in visibility resulting from precipitation, fog, haze, or clouds, as well as airframe icing, turbulence, and wind shear. Flight during instrument meteorologic conditions (IMCs) requires adherence to IFR, whereas visual meteorologic conditions (VMCs) allow alternative use of VFR. VMCs for airplanes are defined as visibility of at least 3 miles and ceiling of at least 305 m (1000 feet) (departing from an airport in controlled airspace).34 The ability to fly IFR not only improves the likelihood that the mission can be undertaken and completed safely should clouds or adverse weather be present but also enhances the ability of the air traffic control center to follow the flight and properly separate aircraft. IFR capability has drawbacks. Sophisticated and expensive equipment and training are required. Virtually all fixed-wing aircraft are capable of IFR operations, but most EMS helicopters are not. IFR operations are usually conducted from airport to airport (where an instrument approach is available), but most helicopters travel to and from nonairport points without an instrument approach. The percentage of actual

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PART FIVE: RESCUE AND SURVIVAL

A

B

Figure 35-8. A, U.S.Coast Guard C-130 Hercules aircraft.This long-range aircraft is used for ice patrol, fisheries management, and search and rescue.B, Coast Guard HH-65 Dolphin helicopter.This short-range light-lift helicopter is used for near-shore search and rescue, maritime fisheries enforcement, and law enforcement. (Courtesy U.S. Coast Guard.)

missions canceled or aborted because of IMCs is small in most rotor-wing programs. One study determined that inadvertent excursions into IMCs occurred about 1.3 times per pilot per year, and the anticipated percentage of operations that would be conducted IFR, if it were available, was 9.4%.76 For most hospital-based programs, the cost of upgrading to a more expensive IFR-equipped helicopter (especially if a copilot is necessary for IFR certification), plus the added expense of maintaining pilot IFR proficiency, would be prohibitive. As a rule, military helicopters fly with a pilot and copilot and are usually capable of flying in IFR conditions, although IMCs are far from ideal for SAR operations.

be adequate to provide lift. This fact may be critical if insufficient altitude has been gained to allow a return to the airport before obstructions are encountered. Therefore, single-engine climb performance for various types of aircraft must be considered, especially if operating out of high-altitude airports, in hot weather, or in mountainous regions (see Table 35-4). In general, single-engine climb performance is about 200 to 290 fpm in piston twins, 600 to 900 fpm for turboprops, and 1000 to 2000 fpm for jets.70 The airplane with the best singleengine climb performance will provide the greatest margin of safety, but the cost of equipment, pilot training, and adequate runways will be high.

Performance

Aircraft for Search and Rescue

Closely related to aircraft speed is its ability to climb, expressed in feet per minute (fpm). Known as performance, this ability dictates the type of aircraft used for a given aeromedical transport mission. The greater the performance (a complex function of power, weight, wing, propeller, and air density characteristics), the better is the aircraft’s ability to out-climb adverse weather or to avoid rising terrain or obstacles. Helicopters are unique in their ability to hover above the ground effect, that is, to climb vertically out of the supporting cushion of air produced by the rotor wash. Helicopters perform better when they have a running start, building up forward speed while still in the cushion of ground effect until translational lift is developed. Translational lift results from the forward-to-backward flow of air over the rotor blades. A helicopter’ s ability to climb vertically out of ground effect is limited by horsepower and weight. On a hot day at high altitude, performance may be insufficient to take off vertically.50 This must be considered when selecting a landing site away from an airport. If a confined space surrounded by obstacles is selected, a vertical takeoff may be required.19 Fixed-wing aeromedical aircraft are virtually all twin engine not only for enhanced speed, performance, and cabin space but also for the necessary redundancy of systems required for IFR operations under FAR part 135. If one engine fails, a second is available to allow flight to be maintained; however, if failure occurs during takeoff, single-engine climb performance may not

SAR is a special type of aeromedical transport that demands aircraft uniquely suited to this role. The aircraft should have good visibility to the sides and below, the ability to fly slowly and to hover, the ability to land away from an airport, and adequate performance in high-density altitude conditions. In addition, certain extrication situations require the capability to hoist victims from rugged or hostile terrain. Helicopters are the aircraft of choice for many SAR missions (Fig. 35-8). Few hospital-based EMS helicopters are configured for hoist operations, and hospital flight crews are typically not trained in SAR techniques. The SAR mission differs from other types of medical missions in its requirement for low-level flight over potentially hostile terrain, its use of flight crews for visual surveillance for survivors or wreckage, the need for a prolonged hover if hoist operations occur, and the need for flight crew training in wilderness survival principles if a mishap occurs. Experience and training in these activities are essential for safety. In general, military helicopters and their crews are better equipped and trained to carry out SAR operations. For example, U.S. Coast Guard and Air Force helicopters have radio locating equipment to pinpoint emergency location transponders (ELTs), also known as emergency position-reporting beacons; possess night vision and FLIR cameras to maximize the probability of visually locating a survivor; and have hoists that enable them to extract survivors from areas where landing is not an option.

Chapter 35: Aeromedical Transport Flight crews on these missions must be specially trained in the use of rescue equipment and must possess the appropriate medical qualifications and experience to deal properly with atypical EMS situations. U.S. Navy and Coast Guard rescue swimmers and Air Force PJs are trained to enter the water or proceed on land to aid in the recovery of survivors. Navy and Coast Guard rescue swimmers receive basic medical training; USAF PJs are trained to the EMT-paramedic level and are given additional training in long-term care of trauma victims. Special hazards exist in mountainous areas. High-density altitudes may limit an aircraft’s performance, and local weather patterns may be erratic. On the leeward side of mountains or ridges, severe downdrafts may prevent a helicopter from hovering out of ground effect. The landing site selected should be free of terrain obstacles and should allow for a long, shallow approach and departure. Open areas away from the leeward side of mountains or ridges are preferable. SAR aircraft may not routinely carry the same medical equipment (e.g., ventilators, pacemakers, and defibrillators) as the typical EMS helicopter. Care should be taken to verify that the medical equipment carried on a SAR aircraft is adequate for the intended mission (see Chapters 32 and 33).

Pilot Requirements Helicopter EMS are usually VFR operations, and the FAA has established minimum requirements for pilot experience. FAR part 135.243 specifies that the pilot in command of a helicopter carrying passengers for hire must have at least 500 hours of flight time, including at least 100 hours of cross-country time with 25 hours at night. Fixed-wing services are typically IFR operations, and pilots must have at least 1200 hours of flight time, including 500 cross-country, 100 night, and 75 hours of actual or simulated instrument time. They must also be instrument rated and possess a commercial certificate. Most EMS helicopter pilots have much more experience than the minimum requirements; one survey found 59% had more than 4000 hours, and none fewer than 2000 hours.35 The pilot in command is solely responsible for the safety of all passengers and must decide whether to accept or decline a mission. For this reason, the pilot is often not told the nature of the medical mission until a decision to go is made. This decision should be based on the destination, weather conditions, environmental circumstances, and estimated time at the scene, airport, or destination facility. No mention of patient type or severity should be made to the pilot before the launch decision is made so that this decision is objective. The pilot has the final say on all decisions related to safety of flight.

Communications Helicopter EMS units must have the capability to communicate on very-high-frequency (VHF) air bands assigned for air traffic control, flight service, and local airport Unicom. In addition, the ability to communicate with ground EMS and public safety through VHF and ultrahigh-frequency (UHF) air bands is essential. Air use frequencies are accessible through standard aircraft communications transceivers, but EMS communications require additional radio equipment designed for this purpose. Additional needs include communication with the helicopter’s base station, either on a locally assigned public-use frequency or a Federal Communications Commission (FCC)-assigned discrete frequency in the VHF air band. Another means of communication is aircraft 800-MHz radiotelephones that can access the

777

surface telephone network. Communication over air band frequencies requires strict adherence to FAA communications guidelines and a radiotelephone operator permit from the FCC.29

Medical Equipment and In-Flight Monitoring On-board medical supplies and equipment are typically tailored to the needs of a specific transport program and include medications, airway and ventilation supplies, dressings and bandages, IV fluids, immobilization devices, military antishock trousers, and stretchers.86 The U.S. Department of Transportation (DOT), in conjunction with the American Medical Association (AMA), has published guidelines for onboard equipment for air ambulance operation92 (Box 35-2).

Power Most aircraft systems operate from 14 or 28 volts of directcurrent (DC) power supplied by an engine-driven alternator or generator. This is not adequate to operate most medical devices, which require 110 to 120 volts of alternate-current (AC) power. Such devices cannot be used without an internal battery of sufficient charge to provide power for the duration of the mission, or unless a 110- to 120-volt AC power source is available from a power inverter, which must be installed under STC. Power inverters are common components of EMS helicopters and dedicated fixed-wing aircraft that have been retrofit with a custommade air ambulance cabin configuration, but they may not be a standard component in fixed-wing aircraft that support a dual role and use an interchangeable corporate configuration.

Stretcher The patient stretcher must be secured to the aircraft according to the requirements of FAR part 23.561 or 25.561 for seats: 3.0 g upwards (2.0 part 25), 9.0 g forward, and 1.5 g sideways (in this context g is a measure of force, 1.0 g being equal to the force generated when an object is subjected to an acceleration equal to the acceleration of gravity, e.g., 9.8 meters per second per second). For helicopters, the requirements are 1.5 g upward, 4.0 g forward, and 2.0 g sideways. Special configurations, especially those incorporating oxygen bottles and metal framework, may require an STC. Other guidelines (recommendations only) for stretcher configurations are for clear view and access to the patients with at least 30 inches (76.2 cm) of headroom and at least 12 inches (30.5 cm) of aisle beside the head. The stretcher should be at least 19 inches wide (48.2 cm) by 73 inches long (185.4 cm).108 If the patient is positioned with head forward, the acceleration that occurs during takeoff of a fixed-wing aircraft may cause venous pooling in the lower extremities and transient hypotension. To prevent this, the patient can be positioned with feet forward.

Climate Control The aircraft must be capable of maintaining a comfortable interior environment; about 24° C (75° F) is recommended. During summer months, the extensive glass area on a helicopter can produce a greenhouse effect, which may necessitate air conditioning for the comfort of both crew and patient.

Lighting Lighting should be available to enable the crew to attend to the patient’s needs but not interfere with cockpit operations. Curtains or other physical barriers may satisfy this need.

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PART FIVE: RESCUE AND SURVIVAL

Box 35-2. U.S. Department of Transportation–American Medical Association Guidelines for On-Board Medical Equipment for Aeromedical Transport BASIC MEDICAL EQUIPMENT RECOMMENDED FOR EACH FLIGHT

1/patient 2/patient 2/patient 1/patient 1/patient 1 set

Litter or stretcher with approved restraints Sheets Blankets Pillow with cover impervious to moisture Pillowcase Spare sheets and pillowcase (if weight and space allow) 1 unit Medical oxygen with manual control; adjustable flowmeter with gauge (0–15 L/min); attachment for humidification (NOTE: The oxygen unit must be attached to the aircraft in an approved manner. The amount of oxygen to be carried is determined by multiplying the prescribed flow rate by the length of time the patient must be on oxygen and adding a 45-minute reserve. The minimum amount of oxygen carried should be enough to supply one patient for 1 hour at 10 L/min. It may be necessary to carry a portable oxygen unit if oxygen is not available for patient transfer at some point in the flight.) 2 each Oxygen masks in adult, child, and infant sizes 6 Connecting tubes 1 Oxygen key 1 unit Portable suction with connecting tubes 2 each Suction catheters (various sizes) 2 Tonsil suction tips 1 unit Squeeze bag-valve-mask unit capable of receiving oxygen through an inlet, and delivering 80% to 100% oxygen through the mask; with masks in adult, child, and infant sizes (bags in adult and small child and infant sizes) 1 unit Oxygen-powered, manually triggered breathing device (100-L/min flow rate) 1 Blood pressure cuff, sphygmomanometer 1 Stethoscope (NOTE: To record blood pressure readings, a Doppler or electronic stethoscope may be required if noise or vibration levels are high. An electronic unit must not cause electromagnetic interference on aircraft equipment.) 2 each Oropharyngeal airways in adult, child, and infant sizes 1 Emesis basin 1 Urinal or bedpan or both 1/patient Sound suppressors 1 Pneumatic antishock trousers with pressure relief valve 2 Cervical collars 2 20-gallon trash bags 1 box Zipper-lock plastic bags or similar product 1 Flashlight, 2 D batteries or equivalent with spare batteries and bulb 2 Locking hooks (or other positive locking device for intravenous fluid containers) 1 qt Drinking water 12 Paper cups

DRESSINGS AND SUPPLIES KIT, DESIGNED TO BE CARRIED ON EACH FLIGHT

4 12 2 1 4 1 each 1 each 4 1 1 4 2 pair 3 1 box 6 2 each 3 each 3 each 2 24 6 2 2 2 1 roll 1 2 4 12 1 box

Cardboard or air splints or equivalent in arm and leg sizes Tongue depressors Mouth gags or padded tongue depressors Bandage scissors Tourniquets Rolls of adhesive tape, 1/2, 1, 2, 3 inch Rolls of paper tape, various sizes Kling bandages or equivalent 3-inch elastic bandage 4-inch elastic bandage Kerlix rolls or equivalent Sterile gloves Petrolatum gauze Adhesive bandages Disposable surgical face masks Syringes, 3, 5, and 10 mL (TB and insulin) Needles, 18, 20, and 22 gauge Needles, 19, 21 gauge, scalp/vein Surgical dressings Sterile gauze pads Nonsterile gauze pads Triangle bandages Wrist restraints Eye covers Aluminum foil, sterilized and wrapped Large safety pin Clinical thermometers Airsick bags Waterless towelettes Tissues

MEDICATION AND INTRAVENOUS KIT, DESIGNED TO BE CARRIED ON EACH FLIGHT

2 2 2 4 2 2 2 2 3 6 1 2 4 2 6 2 1 1

Epinephrine HCl, 1 : 1000, 1 mL, prefilled syringe Epinephrine HCl, 1 : 10,000, 10 mL, prefilled syringe with intracardiac needle Aminophylline inj., 500 mg in 2-mL ampules Atropine sulfate, 0.5 mg in 5-mL prefilled syringe Diphenhydramine HCl, 50 mg/mL, 1-mL prefilled syringe Dextrose, 25 g/50 mL, prefilled syringe Intravenous injection sets with microdripper Lidocaine HCl, 2 g/10 mL, prefilled syringe Lidocaine HCl, 20 mg/mL, 5-mL prefilled syringe Naloxone HCl, 0.4 mg/mL, 1-mL ampules Nitroglycerin, 0.4 mg, sublingual tablets, 100 Digoxin inj., 0.5 mg/2 mL, ampules Furosemide, 10 mg/mL, 2-mL ampules Chlorpromazine HCl, 25 mg/mL, 1-mL ampules Sodium bicarbonate inj., 3.75 mg/50 mL, prefilled syringe Morphine sulfate, 15 mg/mL, prefilled syringe Hydrocortisone sodium succinate, 100 mg/vial Methylprednisolone sodium succinate, 1000 mg/vial

Chapter 35: Aeromedical Transport

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Box 35-2. Department of Transportation–American Medical Association Guidelines for On-Board Medical Equipment for Aeromedical Transport—cont’d 1 2 3 6 1 2 2 1 1 1 1 1 2 3 1 1 1 1 1 1 2 6 1 1 1 2 2 1 1 1 1 1

Plasma protein fraction, 250 mL with infusion set Sterile water for injection, 20 mL Diazepam, 5 mg/mL, 2-mL prefilled syringe Alcohol swabs Phenylephrine HCl, 0.25%, nasal spray Ammonia inhalant solution, 0.5-mL ampule Isoproterenol HCl, 1 : 5000, 1-mL ampules Tourniquet 0.9% sodium chloride inj., 500-mL bag 0.9% sodium chloride inj., 250-mL bag Lactated Ringer’s inj., 250-mL bag Lactated Ringer’s inj., 500-mL bag Lactated Ringer’s inj., 1000-mL bag Needles, 15 gauge, 11/2 inch Dextrose, 5% in water, 250 mL Dextrose, 5% in water, 500 mL Dextrose, 5% in normal saline, 250 mL Dextrose, 5% in normal saline, 500 mL Pressure pack or infusion pump each Drip tubing, regular and pediatric Armboards Alcohol wipes Clean hemostat each Sterile hemostat, curved and straight Nasogastric tube, 14 gauge Sterile normal saline for injection, 20 mL pair Sterile gloves Knife handle Subclavian set No. 15 blade Intravenous infusion cuff each Rolls of tape, 1 and 2 inch

AIRWAY MANAGEMENT KIT, DESIGNED TO BE CARRIED ON EACH FLIGHT

1

Laryngoscope with curved and straight blades in various sizes; spare batteries and bulb As Adapters for attaching endotracheal tubes to required oxygen, etc. 1 Rubber-shod forceps 1 Magill forceps 1 Esophageal obturator airway with gastric suction capability 1 McSwain dart or Heimlich valve 1 Syringe, 60 mL 1 Needle, 14 gauge 1 Syringe, 10 mL 1 each Rolls of adhesive tape, 1 and 2 inch 1 Viscous lidocaine HCl, 2% 1 tube Surgical lubricant BURN KIT, TO BE CARRIED WHEN REQUIRED

3 Normal saline, 1 mL in plastic container 1 Sterile burn sheet, 57 × 80 inch 5 packs Xeroform gauze, 5 × 9 inch 1 Irrigating syringe, 50 mL 2 pairs Sterile gloves 4 Kerlix rolls 2 packs Fluffy gauze POISON DRUG OVERDOSE KIT, TO BE CARRIED WHEN REQUIRED

1 1

Irrigation tray Surgical stomach tube for lavage

1 each Specimen bottles for urine, gastric, and miscellaneous 2 each Stomach tubes, 14, 16, and 18 fr 1 Rubber stomach tube, no. 20 1 tube Lubricant 1 box Glucagon, 1 unit 2 Ipecac syrup, 30 mL 1 Physostigmine salicylate, 1 mg/mL, 2-mL ampules 1 Pralidoxime chloride, 1-g kit 1 Activated charcoal, 10 g OBSTETRIC KIT, TO BE CARRIED WHEN REQUIRED

1 2 1 1

Disposable obstetric pack with sheets, cord clamps, DeLee suction, plastic bag, silver swaddler, sterile gloves Oxytocin, 10 units/mL, 1-mL ampule Episiotomy scissors Ring forceps

PEDIATRIC KIT, TO BE CARRIED WHEN REQUIRED AND ALWAYS WITH OBSTETRIC KIT

1 Pediatric laryngoscope handle with blades 1 each Pediatric endotracheal tubes with stylette, 2.5, 3, 3.5, and 4 fr 1 Pediatric Magill forceps 2 Bulb syringes 2 DeLee suction 2 Pediatric drip intravenous tubing 1 each Feeding tubes, 3.5, 5, and 8 fr 1 Pediatric blood pressure cuff, sphygmomanometer ADDITIONAL EQUIPMENT FOR TRAUMA PATIENTS, TO BE CARRIED WHEN REQUIRED

1 1 1 1 1

Scoop stretcher Long backboard Foley catheter set Femur traction splint Suture kit

ADDITIONAL EQUIPMENT FOR CARDIAC PATIENT, TO BE CARRIED WHEN REQUIRED

1 unit Cardiac monitor with strip chart recorder 1 each Spare ECG electrode for each lead 1 Spare roll of ECG recording paper 1 unit Defibrillator with four pads and conductive gel (defibrillator may come as a unit with the cardiac monitor) 1 Rubber mat or other means of electrically isolating the patient from the aircraft 1 Cardiac board ADDITIONAL EQUIPMENT FOR SPECIFIC PATIENTS, TO BE CARRIED WHEN REQUIRED

1 unit 1 unit

Respirator capable of continuous ventilation, with ventilator, tubing, exhaled volume measuring device, set of tracheostomy endotracheal adaptors Incubator, with all equipment suitable for neonatal care

Modified from U.S. Department of Transportation, National Highway Traffic Safety Administration; American Medical Association Commission on Emergency Medical Services: Air Ambulance Guidelines. Washington, DC, DOT, 1981. ECG, electrocardiogram; fr, French; inj., intramuscular injection.

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TABLE 35-5. Oxygen Tank Specifications Endurance† (hr) ENDURANCE (hr) CYLINDER SIZE D G Q H and Q

WEIGHT (lb)

CAPACITY* (L)

AT 2 L/min

AT 10 L/min

11 32 70 150

356 1200 2320 6900

2.0 10.0 9.3 57.5

1.0 2.0 3.8 11.5

*At 21° C (70° F), 14.7 PSI. Capacity varies with ambient conditions. †Estimated endurance; actual values may vary. From National EMS Pilot’s Association: Hosp Aviat 1986;5(6):17.

Suction Suction is a requirement for ambulance operations in most states and should be available at all times during aeromedical transport. Integral suction as a custom retrofit system or a portable battery-powered device can be used.

Oxygen In general, enough oxygen should be provided for the flight, plus a 45-minute reserve (IFR; 30 minutes VFR). In addition, oxygen should be carried to allow for ground handling time at either end. The amount of oxygen required can be obtained by multiplying the desired flow rate in liters per minute (L/min) by the total duration of transport and patient loading and unloading. Table 35-5 lists the capacities of various types of oxygen tanks and their respective weights. Some portable ventilators have a gas-driven logic circuit that requires additional air or oxygen. Electrically powered ventilators have a lower requirement for oxygen but carry the additional need for a power inverter. Most patients are transported with oxygen supplied by nasal cannulae (1 to 6 L/min). A single E-sized oxygen cylinder is adequate for short flights, although backup cylinders are usually carried. Patients intubated and maintained on 100% oxygen, as well as those ventilated on long flights, will exceed the capacity of an E cylinder quickly; several E cylinders or an H cylinder will be required.

Ventilators On short flights, most patients can be bag ventilated manually, with the addition of a positive end-expiratory pressure (PEEP) valve as needed. Manual ventilation has drawbacks. Minute ventilation can rarely be precisely controlled, leading either to respiratory acidosis or more often to alkalosis. The patient’s tidal volume limits may be exceeded, with resultant pulmonary barotrauma. More important, the medical attendant will be completely occupied with ventilation and is thus unavailable to perform other tasks. This takes on added importance if complex infusions are being administered or in-flight complications occur. The likelihood that manual ventilation will be unsatisfactory increases with the duration of transport, medical complexity of the patient, and severity of underlying lung disease. Compact ventilators are available for use in the aeromedical transport environment.14,53 The simplest are pressure ventilators with a timing valve mechanism that will deliver a predicted minute ventilation at a given rate and tidal volume adjustable to patient size. These require that the patient have normal

airway compliance. If airway resistance increases, smaller tidal volumes will result, and tidal volumes usually cannot be varied independently from rate. Volume-cycled ventilators are superior and available in configurations in which tidal volume and rate can be varied independently. Oxygen bottles, a 50-PSI regulator, high-pressure gas lines, a patient breathing circuit, and source of humidification need to be present. As mentioned, ET tube cuffs need to be appropriately monitored during flight to prevent overinflation resulting from decreased ambient pressure.

Infusion Devices Several methods of IV infusion delivery are available in the aeromedical setting: gravity-feed microdrip or macrodrip tubing with the drip rate manually adjusted, gravity-feed automatic infusion regulators with a closed-loop drip-monitoring feedback mechanism controlling drip rate, and infusion pumps. If a pump is used over moderate or long transport distances, the internal battery power may be inadequate, necessitating an external source of power, usually an AC power inverter. With infusions that must be carefully maintained, an infusion pump is preferable. With frequent patient movement and manipulation, tubing can bend and kink, altering resistance to fluid flow. Air trapped in tubing (or in glass IV bottles) can expand with changes in altitude and increase or decrease the infusion pressure. Thus a reliable servo-controlled infusion system provides a margin of safety.

Monitor-Defibrillator and External Pacemaker Combination monitor-defibrillators operate from internal batteries when 110 to 120 volts AC is not available. Other monitors capable of pressure monitoring from arterial lines or pulmonary artery catheters may be used, but these may have limited usefulness on flights of short duration, during which vibration and motion (turbulence) can introduce artifact and erroneous readings, as may occur aboard a helicopter. These devices may find a greater role with dedicated fixed-wing aircraft that frequently transport critically ill patients over long distances. Noninvasive blood pressure measurement is reasonably accurate in most patients, although these devices may have insufficient sensitivity.65 Potential hazards of defibrillation while airborne remain a concern, although trials support its safety.25,47 Caution is still advised, and care should be taken to ensure that crew and aircraft systems are isolated from potential electrical contact (see “Common Aeromedical Transport Problems”). The pilot should be notified before defibrillation. It is unlikely that defibrillation will cause a problem with the aircraft, but if in a critical phase of flight (e.g., takeoff, landing), the pilot may delay the shock until the critical phase of flight is accomplished. Some external pacemakers have been approved for use in flight; however, care must be taken to ensure that the pacemaker and pads are properly shielded so that it will not interfere with the aircraft systems.

Oximetry Pulse oximetry is often indicated for optimal patient care. Pulse oximeters use a colorimetric method, with placement of a soft probe over a fingertip, in a thin skinfold such as an earlobe, or against the conjunctiva.1,53,96 They may be extremely useful in aeromedical transport, during which other methods to detect changes in respiratory status are difficult.

Chapter 35: Aeromedical Transport

whose illness or injuries are complex or whose clinical conditions are extremely unstable may benefit from the presence of a physician. All aeromedical transport programs include one or more of the following providers in the transport medical crew.

TABLE 35-6. Medical Attendants in Aeromedical Transport, 1988–1993 PERCENTAGES 1988

1990

1991

1992

1993

3 97

3 97

2 98

2 98

54 11 12 15 8

53 11 11 20 5

57 19 10 7 7

71 21 3 2 3

2 68 16 9 5

4 70 15 5 6

6 82 11 0 1

3 63 10 19 5

17 83

10 90

4 96

5 95

38 15 3 35 9

36 25 2 32 5

54 18 0 18 10

59 24 6 9 2

3 43 14 40

2 50 14 34

2 47 19 32

8 46 8 38

Helicopter Medical Crew One attendant 8 Two attendants 92 Crew Configuration RN/paramedic 44 RN/RN 15 RN/physician 10 RN/other 17 Other 14 Regular-Duty Shift Length 8h 2 12 h 62 24 h 18 12 and 24 h 9 Other 9 Fixed-Wing Aircraft Medical Crew One attendant 17 Two attendants 83 Crew Configuration RN/paramedic 41 RN/RN 17 RN/physician 5 RN/other 22 Other 15 Regular-Duty Shift Length 8h — 12 h 46 24 h 14 Other 40

781

RN, registered nurse. From Cady G: Air Med J 1993;12:308.

Emergency Medical Technician–Paramedic EMTs are increasingly a part of the aeromedical flight team. In 1993, 71% of rotor-wing transport programs reported using an EMT-paramedic as a member of the flight team, compared with 44% in 1988.17 Paramedics vary in their level of training depending on the state in which they work but usually follow DOT guidelines, which include three levels of certification. EMT-basic provides basic ambulance, rescue, and first-aid skills. EMT-intermediate may include IV and intubation skills. The EMT-paramedic level involves such skills as intubation, IV techniques, medication administration, defibrillation, and arrhythmia recognition and treatment. For an aeromedical flight team member, additional training relating to the aeromedical environment is desirable.53,94,108 EMTs can be of particular value in operations that necessitate frequent interaction with ground EMS. In some regions, helicopter EMS service is integrated into the regional primary response network so that they arrive at the accident scene before ground units, and flight team members experienced in scene assessment and victim extrication are essential.

Flight Nurse At least one flight nurse is part of almost all aeromedical transport programs; in 1993, 21% of rotor-wing programs reported using two flight nurses as the sole team members.17 Critical care or emergency nursing experience is usually a prerequisite, with additional training that includes patient assessment, advanced cardiac life support, a trauma life support course, prehospital care skills, certain procedures such as ET intubation, advanced IV cannulation techniques, and in some cases, needle thoracostomy, venous cutdown, cricothyrotomy, and other specialized patient care activities. The flight nurse often is also a certified EMT.

Flight Physician Mechanical Resuscitators Cardiac arrest resuscitation while airborne in a small cabin is difficult and physically demanding. In most instances, a standard medical crew of two will be completely occupied in performing chest compressions and ensuring ventilation. Additional tasks may be impossible. Therefore, a mechanical resuscitator may be used to prevent fatigue and free crew members for other tasks.75 Mechanical resuscitators are gaspowered devices capable of providing ventilation and chest compressions automatically. Some models provide only chest compressions.


FLIGHT CREW Crew Configuration One of the continuing controversies in aeromedical transport involves crew composition (Table 35-6). The ideal crew composition varies considerably with the mission profile. When the aircraft is involved in a primary response to the accident scene, inclusion of an EMT may be beneficial. Transport of patients

The experience and training of physicians involved in aeromedical transport depend on their role. Those who function as the on-line medical control physician communicate via radio or 800-MHz radiotelephone with the flight crew, monitor care, and give necessary orders. In the United States, physicians fly as a component of the flight team in a minority of aeromedical transport programs; in 1993, only 3% of all rotor-wing transport programs reported the routine use of a physician, compared with 10% in 1988.17 In helicopter EMS operations, an emergency physician or trauma surgeon may be appropriate, whereas with fixed-wing transport of intensive care unit patients, an intensivist may be of value. Physicians functioning in this role must have a current level of skill and expertise sufficient to address a wide range of clinical problems. They must also possess additional training relative to the airborne environment, including flight physiology, aircraft operations, and prehospital care (Box 35-3). Most important, they must function in this role with sufficient frequency so as to maintain their skills and remain safe and comfortable within the aeromedical setting. In doing so, they become an asset to the flight team rather than a distraction or liability.

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PART FIVE: RESCUE AND SURVIVAL

Box 35-3. Specialized Training for Aeromedical Transport Aviation physiology Atmospheric pressure changes with altitude Gas expansion with altitude Changes in partial pressure of oxygen with altitude Effects of motion and acceleration Effects of noise and vibration Changes in temperature and humidity Aircraft safety Aircraft systems and equipment operations In-flight emergency procedures Survival techniques Patient extrication and immobilization Patient loading and handling aboard an aircraft Patient care techniques in the aeromedical environment Respiratory support and ventilation aboard the aircraft Pertinent Federal Aviation Administration regulations and procedures Familiarity with the local EMS system Radio communications skills and techniques Hazardous materials response procedures Record keeping and documentation in aeromedical transport Preflight, in-flight, and postflight procedures Clinical procedures Cardiopulmonary resuscitation aboard the aircraft Defibrillation aboard the aircraft Intravenous cannulation Endotracheal intubation Tube thoracostomy Needle thoracotomy Cricothyrotomy Central vein catheterization Pericardiocentesis Nasogastric tube insertion Bladder catheterization Antishock trouser application Interosseous line placement Umbilical vein catheterization

Studies during the late 1980s and early 1990s attempted to determine whether a physician crew member has an effect on the outcome of patients transported by helicopter.7,9 Some studies concluded that a physician crew member had a positive impact on patient outcome, whereas others found no difference in outcome between similar cohorts of patients transported by flight crews with two nurses or a nurse and a paramedic.43,88 The cost of using a physician crew member is substantially higher than that of a nurse–nurse or nurse–paramedic crew configuration. Some argue that this higher cost would be offset by the decrease in hospital stay or lost person-years that would occur if a physician were a standard member of the flight crew. With advanced training in critical procedures and treatment protocols, combined with on-line medical direction, a nonphysician flight crew usually functions as well as a crew that includes a physician. No objective evidence supports the benefit of a physician as a standard flight crew member in helicopter transports.

USAF CCAT teams, U.S. Army burn transport teams, and other military transport teams designed to move critically ill or injured patients over long distances will almost invariably have a specially trained physician (intensivist or burn specialist) as part of the team. Given the long duration of intercontinental missions and the difficulty of diverting transoceanic flights, the presence of a specialist physician onboard is vital to safe transport.53,84

Crew Member Stress By its nature, aeromedical transport involves moving a gravely ill patient into an adverse environment with limited resources. Under these conditions, a medical crew of only two or three persons must perform complex tasks, solve difficult problems, and make life-or-death decisions. They must perform in a physically confining space that may be uncomfortable, and they must do so under time pressure and with little or no physical assistance. In some cases, rescuers’ lives may be at risk. This scenario occurs in few other arenas of civilian medical care. The term stress describes an array of adverse physiologic and psychological reactions that occur when a person perceives a threat to existence. Although stress may not diminish performance, it may be responsible for errors, faulty judgment, and uneven manual skill performance. It may also affect the physical and psychological health and satisfaction of the flight crew member.18 When measured during patient flights, the level of anxiety among aeromedical crew members was significantly higher than during a baseline period on the ground.100 Factors that correlate with high in-flight anxiety levels include adverse weather conditions (e.g., low ceilings, high winds), severity of the patient’s medical condition, complexity of illness or injuries, and the crew member’s fatigue. Efforts should be made to minimize stress among crew members. This includes frequent and adequate training; continuing education and feedback; adequate medical backup, including on-line medical direction, written protocols, and treatment guidelines that can aid in difficult decisions; a supportive rather than an intimidating or critical quality assurance program; adequate rest; and safe weather minimums. Both routine mission debriefing and critical incident stress debriefing should be an integral part of all transport programs.71,72


FLIGHT PHYSIOLOGY Aeromedical care is different from ground-based care not only because of special equipment and the space-limited environment but also because of the hostile physical milieu.

Hypoxia and Altitude The earth is blanketed by a sea of air. The troposphere lies in the first 9144 to 18,288 m (30,000 to 60,000 feet) and contains atmospheric moisture. Vertical convection currents, as well as a temperature decline with increasing altitude at a lapse rate of 2° C per 305 m (3.6° F per 1000 feet), occur here. Virtually all atmospheric weather occurs in this layer. Above this level lies the stratosphere, extending from 18,288 to 30,480 m (60,000 to 100,000 feet), where temperature remains relatively constant and no moisture or vertical convection currents exist. Air exerts pressure on everything it contacts in an amount equal to the weight of the column of air above the point of reference. At sea level, the atmospheric pressure is 14.7 PSI or

Chapter 35: Aeromedical Transport

800

TABLE 35-7. Composition of Air

700 Pressure (mm Hg)

783

600 500 400

GAS

PERCENTAGE

Nitrogen Oxygen Carbon dioxide Other gases Water vapor

78.09 20.95 0.03 0.07 1–5 at sea level

300 From Del Vecchio RJ: Physiologic Aspects of Flight. Oakdale, NY, Dowling College Press, 1977.

200 100 0 0

20

40

PAO2 = FiO2 × (PB − PW) − PCO2/R

Altitude
1000 feet

A 100 Partial pressure (mm Hg)

90 80 70 60 50 40 30 20 10 0 0

2

4

6

8

10

14

12

16

18

20

Altitude
1000 feet

B

PAO2

PaO2

Hyperventilation

Figure 35-9. A, Atmospheric pressure vs.altitude.B, Alveolar (PAO2) and arterial (PaO2) oxygen tensions versus altitude.

760 mm Hg. As the person ascends, a progressively smaller air mass remains to exert weight, and the pressure diminishes. At 5486 m (18,000 feet), the atmospheric pressure is one half of that at sea level, and at 8534 m (28,000 feet), it is one third as great (Fig. 35-9). Similarly, under the weight of air, individual molecules tend to compact, so the density of air is also greatest at the surface and diminishes with increasing altitude. These phenomena underlie most of the important physiologic consequences of flight. Air is composed of several gases, of which oxygen makes up about 21%, an amount that is relatively constant despite increasing altitude28,53,76 (Table 35-7). Henry’s law states that the quantity of gas that goes into solution depends on the partial pressure of that gas (and its solubility characteristics) as exerted at the air–water interface. The partial pressure of oxygen in alveolar air (PAO2) is determined by multiplying the fractional composition of oxygen in inspired air (FiO2) by the atmospheric pressure (barometric pressure, PB) after the opposing vapor pressure of water (PW, 47 mm Hg) has been subtracted. This is the basis of the alveolar air equation, as follows:

where PCO2 is the arterial carbon dioxide tension and R is the respiratory quotient (about 0.8). Arterial oxygen tension (PaO2) in normal individuals is within 10 to 15 mm Hg of the PAO2. With lung disease characterized by ventilation–perfusion mismatch, intrapulmonic shunting, or severe diffusion defects, the alveolar-arterial (A-a) oxygen gradient is much larger, and higher amounts of inspired oxygen are required to produce sufficient oxygenation of arterial blood. The atmospheric PO2, PAO2, and PaO2 all decline with altitude (see Fig. 35-9). To some extent, PaO2 can be maintained through hyperventilation as PCO2 is reduced, but eventually PaO2 will decline below 60% and hemoglobin will begin to desaturate greatly. It is important during aeromedical transport to maintain hemoglobin saturation at or above 90%. Knowledge of the patient’s preflight PaO2 will enable a calculation of the patient’s A-a oxygen gradient, which can then be subtracted from the PAO2 calculated for the anticipated en route altitude (or cabin altitude in a pressurized craft) to yield the expected en route PAO2. Nomograms can be devised for this purpose (Fig. 35-10). If the en route expected PaO2 is unacceptably low, supplemental oxygen is required. The FiO2 required to maintain the PAO2 at a given level can be calculated from the alveolar air equation as follows: FiO2 = (PAO2 + PCO2/R)/(PB − PW) Or, if PCO2 = 40, R = 0.8, and PW = 47 mm Hg, then: FiO2 = (PAO2 + 50)/(PB − 47) This allows PAO2 to be determined by adding the PaO2 desired (the minimum acceptable is 60 mm Hg) to the known A-a oxygen gradient (calculated from the preflight blood gas). PB can be estimated over the first 15,000 feet (4572 m) of ambient or cabin altitude as follows: PB = 760 − (23 × Alt) where Alt is the altitude above sea level in thousands of feet. Transport cabin environments rarely exceed these altitudes because pressurized craft are usually capable of maintaining cabin pressure equal to 8000 feet (2438 m) or below at normal cruising altitudes. Nonpressurized craft must provide supplemental oxygen above 15,000 feet. Even a modest increase in FiO2 is usually enough to maintain oxygenation under these

PART FIVE: RESCUE AND SURVIVAL

120

Sea level

110

2000

100

4000

90

6000

80

8000

70

10000 12000

60

14000 50

16000

40

18000 20000 22000 24000

30 20

TABLE 35-8. Clinical Manifestations of Trapped Gas Expansion

Altitude

PaO2 at altitude (mm Hg)

784

10

TRAPPED GAS LOCATION

CLINICAL MANIFESTATIONS

Intestinal lumen Pleural space

Abdominal pain, distention Pneumothorax, tension pneumothorax Subcutaneous emphysema Facial pain Ear pain Tooth pain Air embolism, decompression sickness Compartment syndrome, ischemia Flow rate increase Tourniquet effect Air leak, hypoventilation

Subcutaneous Paranasal sinuses Middle ear Dental root Blood Air splints, antishock trousers IV bottle and tubing Blood pressure cuff Endotracheal tube cuff

circumstances, unless a severe A-a oxygen gradient exists, in which case the addition of CPAP or PEEP may be necessary. The previous equation would predict that a PaO2 of 80 mm Hg at sea level on 40% oxygen would require that an FiO2 of 50% at 8000 feet be maintained. An oximeter can simplify monitoring of oxygenation; as altitude increases, a fall in oxygen saturation can be treated with increases in FiO2.

pressure allows nitrogen bubbles to form in the microcirculation, which may lead to ischemia and tissue damage (see Chapter 57). Care must be taken in the transport of an ill or injured diver to allow a surface interval of at least 12 hours before transport. An alternative is to attain at least a level D (PADI) dive stage, with a cabin altitude not to exceed 2438 m (8000 feet). If an individual must be transported abruptly after submersion, the transport must be conducted at the lowest possible safe altitude in a pressurized aircraft, to reduce the risk for decompression illness. Portable hyperbaric chambers have been developed, and several have been approved for flight in U.S. military aircraft. With one of these chambers, it is possible to transport a diving casualty by air while providing recompression therapy during flight (Fig. 35-11). This will usually require a large aircraft and several crew members to monitor the chamber during the flight. Sufficient pressurized breathing gas must be brought along to supply such chambers. Careful planning to ensure sufficient supply is critical.

Effects of Pressure Changes

Motion and Acceleration

40 50

60

70

80

90 100 110 120

PaO2 at sea level (mm Hg)

Figure 35-10. Arterial oxygen tension (PaO2) at altitude versus PaO2 at sea level.Locate the sealevel PaO2 on the x-axis and intersect with the cruise altitude (on the diagonal). Read across to find the PaO2 at altitude (y-axis).

Trapped Gas Boyle’s law states that the volume of a gas varies inversely with pressure. This means that trapped gases expand as an aircraft ascends to higher altitude (and lower pressure) and contract as it descends. The volume change can be determined from the following equation: P1 × V1 = P2 × V2 Clinically, this is manifested by such alterations as expansion or contraction of air splints or military antishock trousers, changes in ET tube cuff size, expansion of bowel gas in cases of intestinal obstruction or ileus, expansion of pneumothorax air space, and expansion of air trapped in IV lines (or glass IV bottles) (Table 35-8). Certain precautions must be taken, such as the use of plastic IV bags and frequent monitoring of pressure cuffs.

Dysbarism Decompression sickness occurs mainly in scuba divers that ascend too soon after a dive. Too rapid a decrease in ambient

Aircraft not only move through space in a rectilinear fashion, which cannot be detected by human senses in the absence of visual cues, but also rotate around three axes: longitudinal (roll), vertical (yaw), and horizontal (pitch) (Fig. 35-12). Motions around these axes are sensed by the semicircular canals located in the inner ear. Sensations from these organs are useful as an adjunct to visual cues. However, they may quickly lead to spatial disorientation, a phenomenon often experienced by individuals traveling in a turbulent environment without a visual frame of reference. For example, when an aircraft enters a bank to the right, the sensation may be initially correctly interpreted. However, after rollout of the stationary bank to a neutral position, a sensation of rolling into a left bank may be sensed. If uncorrected, apprehension may follow. The best remedy for this effect is to maintain a visual reference to the correct position. Vestibular stimuli, especially in turbulence with limited or no visual frame of reference, may result in motion sickness, manifested most often as nausea or vomiting. Affecting both patients and flight crews, motion sickness can be counteracted with antiemetics such as antihistamines (e.g., dimenhydrinate, 50 mg orally) or phenothiazines (e.g., prochlorperazine, 10 mg orally); however, these may produce sedation and are potentially haz-

Chapter 35: Aeromedical Transport

785

Figure 35-11. A, Hyperlyte portable hyperbaric chamber being inflated and rigged for a dive on board a U.S. Air Force C-17 aircraft. Note the gas lines feeding into the near end of the chamber. At the time this photograph was taken, the aircraft was flying at 15,000 feet. B. Hyperlyte portable hyperbaric chamber being secured to the deck of a U.S. Air Force C-17 aircraft. (A, Photo courtesy of Robert C. Allen.)

A

B

Figure 35-12. Axes of movement in aviation.

ardous in flight. Transdermal scopolamine patches applied behind the ear have been used as effective prophylaxis for nausea and vomiting during flight.

Noise and Vibration Noise and vibration are components of all aircraft environments, especially helicopters. The most obvious impact of noise is on communications within the cabin, particularly with the patient, who is least likely to have a headset and access to the

aircraft’s intercom. In addition, the patient’s breath sounds are difficult if not impossible to hear, and thus other means to identify changes in respiratory status, such as pulse oximetry, must be employed. Headsets are essential for effective communication among flight crew members aboard a helicopter, although they may not be necessary aboard larger fixed-wing aircraft. Noise may lead to permanent defects in auditory acuity if exposure is prolonged or recurrent. Veteran pilots frequently demonstrate 10- to

786

PART FIVE: RESCUE AND SURVIVAL

Box 35-4. Pretransport Preparations SCENE RESPONSE

Airway secured Stabilization on a rigid spine board with cervical immobilization device, neck rolls, and tape Two large-bore intravenous lines Antishock garment applied Landing zone selected and secured INTERHOSPITAL TRANSPORT

Airway secured Stabilization on a rigid spine board with cervical immobilization device, neck rolls, and tape Two large-bore intravenous lines Tube thoracostomy for pneumothorax or hemothorax Bladder catheterization (if not contraindicated) Nasogastric catheterization (if not contraindicated) Lactated Ringer’s solution hanging Typed and cross-matched blood if available Extremity fractures splinted (traction splinting for femur fractures) Copies of all available emergency department records and laboratory results, including a description of the mechanism of injury

20-dB reductions in high-frequency auditory acuity. Noise and vibration may also contribute to stress and fatigue.


COMMON AEROMEDICAL TRANSPORT PROBLEMS

Pretransport Preparation Once the decision is made to transport a patient by air and the appropriate aeromedical service is contacted, preparations must be made to ensure patient safety and comfort and to aid the flight crew in patient care. A study of the causes of ground delays in a rural interhospital helicopter transport program found that on arrival of the flight team, 31% of patients required minor interventions (insertion of IV line or nasogastric tube, blood transfusion, bladder catheterization, military antishock trousers application) before takeoff, and 33% required major interventions (ET intubation, tube thoracostomy, central venous access).62 When no intervention was required, the mean ground time was 31.2 minutes, compared with 57.4 minutes when one or more major interventions were required. To minimize delays, pretransport preparations should be made for victims of acute trauma (Box 35-4).

Patient Comfort Motion, vibration, noise, temperature variations, dry air, changes in atmospheric pressure, confinement to a limited position or backboard, and fear of flying may cause patient discomfort.

Patient Movement Patient handling and movement can contribute to morbidity and mortality in unstable patients.110 All transported patients should be adequately secured to the stretcher with safety straps to prevent sudden shifting of position or movement of a secured

fracture. During transport from the ground to the aircraft cabin, attempts should be made to limit sudden pitching of the stretcher. DOT guidelines recommend design of cabin access such that no more than 30 degrees of roll and 45 degrees of pitch may occur to the patient-occupied stretcher during loading.70 The stretcher, in turn, should be adequately attached to the floor. Motion sickness in the patient may be treated with an antiemetic such as promethazine (25 mg orally, intravenously, or intramuscularly). Scopolamine disks are useful for prolonged flight and do not require parenteral or oral administration, although their antiemetic effects are not always uniform and may not occur until 4 to 6 hours after application. They may be best used to decrease motion sickness in the flight crew.

Noise Noise can be avoided with hearing protectors, which are devices similar to headphones but without internal speakers. Inexpensive hearing protectors are available as deformable foam ear plugs. In some cases, headphones may be used in an awake patient if the crew wants the patient to communicate on the intercom system.

Eye Protection When a patient is loaded on or off a helicopter with the rotors turning, the patient’s eyes must be protected. Serious eye injuries can result from debris blown into the air. Lightweight sky diver goggles (“boogie goggles”) are effective and inexpensive. The eyes must be protected even if the patient is unconscious. Taping temporary patches over the eyes is also effective.

Respiratory Distress Patients with respiratory disease or distress should have immediately treatable conditions addressed before takeoff. ET intubation is essential if airway patency is threatened or if adequate oxygenation cannot be maintained with supplemental oxygen. It is better to err on the side of caution when making a decision about a patient’s airway. During flight, it is easier to treat restlessness in an intubated patient than airway obstruction or apnea in a nonintubated patient. Nearly all seriously ill patients should receive supplemental oxygen. FiO2 should be increased with increasing cabin altitude to maintain a stable PO2 (Fig. 35-13). Small, portable pulse oximeters are readily available and should be used to monitor oxygen saturation while in flight. When oxygen saturation monitoring is unavailable and pretransport arterial oxygen content unknown, 100% oxygen may be administered throughout the flight to ensure adequate oxygenation. Patients with chronic lung disease who are prone to hypercapnia may experience deterioration in condition if the hypoxic drive is eliminated. In these patients, the least oxygen necessary to maintain saturation above 90% is advisable; this amount may be estimated in advance or calculated from the alveolar air equation. Close inflight monitoring is essential, preferably by continuous pulse oximetry. Finally, altitude changes may affect ET cuff volume; thus, cuff pressure must be checked frequently throughout the flight.

Cardiopulmonary Resuscitation and Cardiac Defibrillation CPR in an aircraft is difficult. The rescuers must perform several tasks simultaneously while ventilating the lungs or compressing

Chapter 35: Aeromedical Transport

1

0.9

0.8

FiO2

0.7 0.6

0.5

0.4

0.3 0.2 0

2000

4000

8000

6000

10000

12000

Altitude (ft)

PB

FiO2

Altitude (ft) 0

0.21

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

760

2000

0.23

0.32

0.43

0.54

0.65

0.76

0.86

0.97

PP

707

4000

0.25

0.35

0.47

0.59

0.70

0.82

0.94

PP

PP

656

6000

0.27

0.38

0.51

0.63

0.76

0.89

PP

PP

PP

609

8000

0.29

0.41

0.55

0.69

0.83

0.97

PP

PP

PP

564

10000

0.31

0.45

0.60

0.75

0.90

PP

PP

PP

PP

523

12000

0.34

0.49

0.65

0.82

0.98

PP

PP

PP

PP

483

A-a:

15

79

150

222

293

364

435

507

578

Calculated from the alveolar air equation under standard temperature and pressure conditions. PP, Positive pressure required; PB, barometric pressure (mm Hg); A-a, alveolar–arterial oxygen gradient (mm Hg). X axis: en route altitude Y axis: FiO2 required to maintain PO2 = 90 mm Hg To calculate the FiO2 necessary to maintain PO2 = 90 mm Hg at a specific altitude, choose the value on the Y axis closest to that necessary to maintain PO2 = 90 mm Hg at sea level (altitude = 0 ft) and follow the corresponding line across to the new altitude (X axis). The proper FiO2 is the Y value corresponding to the new X value.

Figure 35-13. Fraction of inspired oxygen required to maintain oxygen tension at 90 mm Hg (varying with altitude).

787

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PART FIVE: RESCUE AND SURVIVAL

the chest, all in a physically confining space. The crew must be familiar with modifications in technique.49 As previously mentioned, there should be no concern with airborne defibrillation if all electronic navigational equipment on the aircraft has a common ground, as mandated by the FAA standards. Despite cramped quarters and sensitive electrical equipment, defibrillation can be safely performed in all types of aircraft currently used for emergency transport utilizing standard precautions routinely used during defibrillation on the ground.25,111 In the interest of safety, however, it is best to notify the pilot before performing defibrillation.

Patient Combativeness Patients may be combative to the point that they pose a threat to the safety of the flight and crew. An uncontrollable patient may cause sudden shifts in aircraft balance or may strike a crew member or important flight instruments or equipment. Such patients should be properly restrained in advance. If sedation is necessary, a careful neurologic examination documented beforehand is essential. Useful agents include diazepam or shorter-acting agents, such as midazolam. Paralyzing agents, such as pancuronium, vecuronium, and succinylcholine, have the advantage of not altering the sensorium, but they require airway control with ET intubation.103 In addition, it is necessary to sedate a patient who is paralyzed to facilitate intubation and transport.

Endotracheal Intubation ET intubation may be difficult to perform while airborne, especially in a confining cabin, and should be done before departure if possible. This is especially true in trauma victims with head injuries and in burn victims who have carbonaceous sputum or hoarseness. Special techniques are available to supplement standard methods of intubation, including a lighted stylet, ET tubes with controllable tips, intubating laryngeal mask airways, and digital intubation. Sedation or pharmacologic paralysis may be necessary. Of 106 aeromedical transport programs in the United States that reported using neuromuscular blocking agents, 39 use them to facilitate intubations, and 67 use them once a patient is intubated to manage combativeness and ensure airway patency.92 Induction of paralysis before intubation in the aeromedical setting is controversial. One study reported a 96.6% success rate using succinylcholine to facilitate intubation, with 3.4% of patients requiring an emergency surgical airway.74 Besides the need for surgical airway if intubation is unsuccessful, concerns exist about cervical spine manipulation during intubation in the paralyzed patient, unrecognized esophageal intubation in a nonbreathing patient, and the relative contraindications to the use of succinylcholine in certain patients. As shorter-acting nondepolarizing paralytic agents (e.g., mivacurium) are developed, this adjunct to airway and combativeness control in the aeromedical setting will be studied further.57 In some flight programs, nonphysician crew members are taught to perform emergency cricothyrotomy. Although occasionally lifesaving, this procedure can be difficult to perform and should be undertaken only as a final method to secure an emergency airway.

Thrombolysis The air transport of patients with acute myocardial infarction often involves thrombolytic therapy. Because bleeding is a major

adverse effect of thrombolytic agents, one study investigated whether air transport resulted in a higher incidence of bleeding complications compared with a similar cohort of patients given thrombolytic drugs who were transported by ground ambulance. The study concluded that helicopter transport of patients with acute myocardial infarction after initiation of thrombolysis is comparatively safe and without a clinically significant increase in bleeding complications.37

Flight Safety Because aeromedical transport involves medical care delivered in a hostile environment, the patient and crew are at risk for injury or death in the event of a mishap. Flight crew training must emphasize safety. The pilot is ultimately responsible for the safety of the aircraft’s occupants and is trained not only to operate the aircraft skillfully and safely but also to provide necessary safety instructions and guidance to crew members and passengers. Safety practices vary depending on the type of aircraft but include common guidelines.

Approaching the Aircraft Helicopters with turning rotor blades must be approached only from the front and sides and only while under pilot observation (Fig. 35-14). The tail rotor must be given wide berth, especially on helicopters with rear doors. It is advisable to station a crew member in a safe position to direct approaching individuals away from the tail rotor. Shutting down the helicopter’s engines completely, when the situation allows, is prudent before patient loading and unloading. Approaching in a crouched position minimizes the risk for contact with the rotor blades should a sudden gust of wind or movement of the aircraft cause them to dip. Loose clothing and debris should be secured (Box 35-5). Fixed-wing aircraft should be approached with similar precautions regarding propellers. This is especially important in aircraft with access doors in front of the wing and engine nacelles. Engine shutdown on the side of entry enhances safety of loading and unloading.

Safety Belt Use The use of safety belts (preferably with shoulder harnesses, especially in helicopters) is an important safety measure. Certain patient care activities (e.g., ET intubation, CPR), however, may be impossible to perform with safety belts secured. The design and selection of aircraft and interior configurations should allow maximal access to the patient with the crew members properly restrained. Throughout the flight, the crew members and patient should remain restrained as much as possible in smooth air and at all times in rough air. Movement inside the cabin affects aircraft balance. An aircraft loaded near its aft CG limit may exceed its limits if a crew member moves to a new position within the cabin. Changes in position should be preceded by consultation with the pilot. Light aircraft are sensitive to turbulent air, and appropriate precautions must be taken to avoid being injured from sudden motion.

Proper Use of Aircraft Equipment Crew members must be familiar with all aircraft equipment they may be required to operate in flight or in an emergency. This includes all aircraft doors, fire extinguisher, communications equipment, oxygen equipment, and electrical outlets. In addition, the crew must be familiar with emergency shutdown pro-

Chapter 35: Aeromedical Transport

Prohibited area

Danger zone

789

cedures. Finally, before takeoff, door security must be confirmed by a crew member familiar with operation of the door.

In-Flight Obstacle Reporting An extra pair of eyes can be invaluable to a pilot in a busy airspace or on a scene approach complicated by trees and electrical or phone wires. Primarily important in VFR conditions, assistance with obstacle identification can enhance the safety of the mission; however, flight should not occur under conditions in which obstacle reporting by a crew member is essential to safety because the person must then divide attention between patient care and obstacle reporting.

Ground Coordination and Control

Acceptable area

Best area

Enthusiastic rescue personnel or curious onlookers may approach the aircraft in a hazardous manner. Flight crew members must be able to communicate with ground units during the landing phase to ensure adequate scene preparation; they may be required to perform crowd control while on the ground. This requires directing individuals away from the rotor blades, propellers, or other hazardous equipment at the scene. If loading or unloading the patient while the rotors or propellers are still turning (“hot loading” or “hot off-loading”) is necessary, special precautions must be undertaken for ground crews, the flight crew, and the patient.

Emergency Procedures Uphill (wrong)

Downhill (right)

Figure 35-14. Helicopter safety. A, Safe approach zones. B, The proper way to approach or depart a helicopter.

Box 35-5. Helicopter Safety DO:

Approach and depart downhill. Use crouched position. Approach after visual contact and approval from pilot. Await direction of flight crew. Approach from the front or the sides. Secure area first of people and then of loose debris. DON’T:

Approach or depart uphill. Use tall intravenous poles or other objects. Use loose sheets or clothing. Smoke tobacco within 50 feet. Run near the aircraft. Drive a vehicle within 30 feet. Shine headlights or flashlights toward the aircraft.

All crew members should memorize and routinely practice emergency procedures. These procedures should address inflight fires, electrical failures, loss of pressurization, engine failure, emergency landing with and without power, precautionary landing away from an airport, and other in-flight emergencies.

Survival An emergency or precautionary landing away from an airport necessitates survival before rescue arrives. Under adverse environmental conditions and with injured victims, survival may depend on specific actions by the crew. The crew should be proficient in emergency egress from the aircraft, including escape after crashes and water landings, especially in helicopters. After water landings, helicopters usually roll inverted and sink rapidly. Helicopter “dunker” training is required for all military helicopter crews. The crews are strapped into a simulated helicopter fuselage and lowered rapidly into a pool, simulating a semicontrolled water landing. The fuselage then rolls inverted, and the crew must open emergency exits and egress the simulator. This type of training has been shown to save lives in helicopter water crashes. All crew members should be trained in the use of emergency signaling devices, such as emergency locator transceivers (ELTs), flares, signal fires, and ground emergency signals. Survival skills should be taught to all crew members, including advanced first aid, water survival, building emergency shelters, fire starting, and obtaining water and food from the environment.

Aeromedical Accidents Attention continues to focus on EMS helicopter accidents. Statistics from 1986 estimated a rotor-wing accident rate of 17.65, with 5.88 fatalities per 100,000 transports.38 Aviation accident rates are typically reported in relation to flight hours. EMS fatalities, therefore, amounted to 6.0 per 100,000 flight hours, compared with 3.3 for the helicopter industry in general. The EMS

Accidents per 100,000 patient transports

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PART FIVE: RESCUE AND SURVIVAL

TABLE 35-10. Effect of Weather on Accident Seriousness 30 25

SEVERITY OF ACCIDENT

20

Fatal Injury Damage only

15

WEATHER RELATED

PERCENTAGE

14/21 3/17 1/32

67 18 3

From Collett HM: Hosp Aviat 1986;5(11):15.

10 5 0

(0) 72- 80 81 82 83 84 85 86 79 Year

87 88 89 90 91

VISIBILITY

Figure 35-15. Aeromedical helicopter accident rate, 1972 to 1991. (From Preston N: J Air Med Transport 1992;11:14.)

TABLE 35-9. Major and Primary Causes and Severity of Aeromedical Accidents, 1972–1989

Major Cause Weather Engine failure Obstacle strike Control loss Other Primary Cause Pilot error Mechanical failure Unknown Accident Severity Fatal Injury Damage only

1987–1988

Day visual meteorological conditions Night visual meteorological conditions Day marginal Night marginal TOTAL

ACCIDENTS

PERCENTAGE

3

14

4

19

4 10 21

19 48 100

From Collett HM: Hosp Aviat 1986;5(11):15.

PERCENTAGES 1972–1985

TABLE 35-11. Environment of Fatal Accidents

1989

30 18 18 9 25

30 9 10 20 40

17 0 33 17 33

64 30 6

60 30 10

83 0 17

36 28 36

50 30 20

67 17 17

From Collett HM: J Air Med Transport 1990;9(2):12.

rate subsequently declined, however, with 3.0 accidents per 100,000 transports reported in 199187,101 (Fig. 35-15). Sixty-four to 84% of EMS accidents result from pilot error, about 23% from mechanical causes, and 3% from unknown causes.21 Of accidents caused by pilot error, adverse weather was a contributing factor in 67%19 (Table 35-9). In all, two thirds of fatal weather-related accidents occur at night, and 86% of all fatal accidents occur at night or in marginal weather conditions22 (Table 35-10). Only 35% to 40% of all EMS helicopter flights occur at night. The most common phase of flight for weather-related accidents was en route (86%), with 14% occurring on departure and none on approach (Table 35-11). Only 5% of fatal EMS helicopter accidents occur in flights to or from the scene, although such flights account for 24% of EMS helicopter missions.23 When scene-related accidents occur, they result in fatalities 9% and injuries 35% of the time, suggesting a low-energy impact versus an en route crash. Causal

factors related to scene accidents include wire and obstacle strikes (70%), loss of control (18%), and mechanical failure (12%). The landing phase is involved in scene-related accidents in 41% of cases, whereas the takeoff phase is involved in 59%. Because 40% of scene-related accidents occur at night and about 40% of helicopter EMS flights occur at night, scene accidents do not appear more hazardous at night than in the day. Single-engine helicopters have more often been involved in engine failure accidents (77%) than have twin-engine craft (the two types are about equal in number in the EMS industry). Recommendations for enhancing safety include instituting stringent guidelines to limit flights at night or in adverse weather, increasing pilot proficiency training, and reducing pilot fatigue and workload factors. Decisions on the appropriateness of air transport regarding utilization and weather should be based on general protocols that are not subject to the emotional turmoil of a medical crisis.12 The trend in the industry has been toward twin-engine helicopters for an increased margin of safety from engine failure accidents. In addition, for dedicated EMS helicopter flights, a statistically strong relationship exists between the ability to fly under IFR and a lower accident rate.64 The AAMS considered the question of whether all helicopters should be required to have IFR capability when it published its voluntary standards for rotor- and fixed-wing aircraft. This was not mandated because of the tremendous expense and because many programs were unlikely to comply.66

Ground to Air Signaling It is best to have radio communication between the ground party and the helicopter crew. This may not be possible, however, and hand signals may be needed to communicate. Standard hand signals are used by military rescue personnel for communication between a deployed rescue swimmer and the helicopter (Table 35-12). These same signals can be used while

Chapter 35: Aeromedical Transport

TABLE 35-12. Swimmer to Helicopter and Ground to Air Signals INTENTION Deploy medical kit Situation okay Lower rescue cable Lower rescue cable Helicopter move in/out Cease operations Deploy litter Personnel secured, raise Team recall

ACTION Arms above head, wrists crossed Thumbs up Arm extended over head, rescue device attached with fist clenched Climbing-rope motion without rescue device with hands attached Wave in/out with both hands Slashing motion across throat Hands cupped, then arms outstretched Vigorously shake hoist cable or thumb up; vigorous up motion with arm Circle arm over head with fingers skyward

on land. To acknowledge the signals, the hoist operator gives a “thumbs-up” sign or the pilot flashes the rotating beacon.

Landing Zone Operations The ideal helicopter landing zone is a wide, flat, clear area with no obstacles in the approach or departure end. Vertical landings and take-offs can be done, but it is safer for the helicopter to make a gradual descent while flying forward. Higher altitudes and higher temperatures require larger landing zones. The center of the landing zone can be marked with a V, with the apex pointing into the prevailing wind. Any obstacles can be marked with brightly colored, properly secured clothing. The size of the landing zone depends on the weather conditions, type of helicopter involved, altitude, temperature, and types of obstacles in the area. Small helicopters such as the Jet Ranger can usually land safely in a 60- × 60-foot landing zone. Larger helicopters such as the Bell 412 require a 120- × 120foot zone.112 Large military helicopters may require even greater landing zones. In general, pilots prefer the largest, flattest piece of ground they can find. The condition of the ground (e.g., loose snow, dust, gravel) should be communicated to the pilot before the final approach. Before the helicopter lands, all loose clothing and equipment should be secured. During approach, no personnel or vehicles should move on or near the landing zone. Once the helicopter is on the ground, it must be approached only from the front and side, and then only while under direct observation of the pilot. The aft portion of the aircraft and areas around the tail rotor must be avoided at all times. Some helicopters (e.g., BK-117) have rear doors for loading and unloading patients, and ground personnel should wait for directions from the crew before approaching the rear area. If the ground is uneven or slopes, all personnel should approach and depart from the helicopter on the down-slope side. It is safest to load the patient into the helicopter with the engines off and the rotors stopped (“cold load”). If the patient must be loaded with the engines on and blades turning (“hot load”), eye and ear protection should be worn by all personnel approaching the helicopter, including the patient. A safety person should be assigned to prevent anyone from inadvertently walking toward the tail rotor. Once the patient is loaded, all personnel should leave the landing zone, take cover, and stay in place until the helicopter has departed. It is best to be off to the side, not directly in the takeoff path.

791

Hoist Operations If the helicopter is not able to land and has a rescue hoist installed, hoist operations may be the only means of evacuating the patient. In most circumstances, a helicopter crew member rides the hoist down to the site to rig the survivor into the rescue device and to oversee the hoist operation, using the following guidelines: • It is critical that personnel on the ground not touch the hoist, rescue device, or cable until after it has touched the ground (or water). Helicopters can build up a very powerful static electricity charge that will be grounded through whatever the hoist touches first. This has been known to knock rescuers and survivors off their feet. • Once the rescue device and cable have touched the ground, put the patient into the rescue device, taking care to keep the hoist cable clear of all personnel. Do not allow the hoist cable to loop around any personnel or around the rescue device because serious injury is possible when the cable slack is taken up. • Make sure that the patient is properly secured in the rescue device, with all safety straps tightened. • When the patient is secured, move away from the rescue device and signal “up cable.” • If the rescue device is a basket (Stokes) litter, use a tag line with a properly installed weak link to prevent the litter from spinning during the hoist.

Night Operations Night helicopter rescue operations are considerably more dangerous than daylight operations. In most cases, it is best to delay helicopter insertion or extraction operations until daylight. If this is not possible, however, night missions can be done safely with careful planning and coordination between the helicopter and ground party. The same rules of daylight helicopter operations apply to night operations, but with extra care taken to ensure that all personnel understand their roles. In night operations, it is virtually mandatory to have radio communications between the ground and the helicopter. “Nocomm” night operations should be attempted only by personnel specially trained and experienced in these techniques. The landing zone should be clearly marked and the pilot allowed to make the approach. All personnel should stay clear of the landing zone until the pilot has made a safe landing. Personnel approaching the landing zone should have a small light or reflective material attached to their outer clothing so they can be clearly seen. The minimum number of people should approach the helicopter, and a safety observer is mandatory to keep the ground team together and clear of the tail rotor and rotor blades. The landing zone should be as large as possible, preferably at least 50% larger than a daylight landing zone. Any obstacles should be clearly marked with light-colored streamers, small lights, or even light-colored clothing. The landing zone can be illuminated with flashlights at the corners, with another flashlight at the center point. These flashlights should be pointed at the ground, not into the air; flashlights pointed at the helicopter during landing and takeoff may distract or momentarily blind the crew. If flashlights are not available, small fires can be used to illuminate the edges of the landing zone, although the helicopter can scatter burning embers for many meters. If crew members are using night vision equipment, lights must never be flashed at the helicopter. Even the amount of white

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PART FIVE: RESCUE AND SURVIVAL

light from a small flashlight may be sufficient to overload the night vision equipment, functionally blinding the crew.

Dispatch and Communications The dispatch center is the focal point for communications during aeromedical transport operations. Dispatchers receive incoming requests for service; obtain necessary information relative to the launch decision; coordinate the interaction between essential parties; “scramble” the flight crew; assemble and maintain necessary information regarding destination, weather, local telephone numbers, and frequencies; follow the progress of the flight; input data into the system database; and communicate with ground EMS units and hospitals. Communication may occur through a combination of methods: land telephone lines into a dispatch switchboard, hospital–EMS net transceiver, discrete frequency transceiver (communications with aircraft), or walkie-talkie radios. Familiarity with the EMS system and EMS communications is essential for successful dispatch. Flight following is an important part of aeromedical safety and involves tracking the position of the aircraft during a mission by plotting the location according to reports from the pilot at 10 to 15 minute intervals. If an accident or in-flight emergency occurs, the dispatcher is soon aware and can initiate SAR to a precise location, which enhances the chances of survival.


APPROPRIATE USE OF

AEROMEDICAL SERVICES

Aeromedical transport combines skilled treatment and stabilization capability with rapid access to definitive care, but not without risk, and at high cost ($1 to $2 million per year for a program, or about $2000 per transported patient, which is about 400% higher than ground transport).15 However, the comparative risk of aeromedical transport must be placed in perspective against the risk for patient death from nonreferral or from less timely ground transport with limited medical capability en route. Although not proved, advanced provider skill levels during prehospital care are considered beneficial, especially in severely ill or injured patients.54 In rural and wilderness environments, advanced life support services may be made more readily available by EMS helicopters. This is especially true in areas that are difficult or impossible to reach by ground. The speed of access to definitive care is another consideration in choosing the mode of transport. In isolated rural or wilderness locations, a helicopter may be the only means of expedient access. Prolonged victim extrication allows time for a helicopter to arrive at the scene, decreasing total transport time and thereby increasing the advantage of helicopter transport. Patient comfort also must be considered, especially on long transports over rough roads. Although a helicopter moves in three dimensions, fore-and-aft acceleration is usually steady, without the starting and stopping motions present during ground transport. However, helicopters typically travel within 914 m (3000 feet) of the ground’s surface and are more subject to turbulence than are high-flying fixed-wing aircraft. Whether aeromedical transport reduces mortality when compared with ground transport has not been determined definitively. An uncontrolled national multicenter study of trauma patients transported by helicopter showed a 21% reduction in

mortality from that expected based on predictions from the Trauma Score–Injury Severity Score (TRISS) methodology and national normative trauma outcome data.10 A similar study using the TRISS methodology compared actual mortality with helicopter versus ground transport and showed a 52% reduction from expected mortality when patients were transported by air, compared with no reduction in expected mortality when transport occurred by ground.7 Another study using TRISS methodology found a benefit of aeromedical transport only in patients with severe trauma (a probability of survival less than 90%).13 In 1990, the AAMS issued a position paper on the appropriate use of emergency air medical services. In 1992, these recommendations were accepted by the California Medicaid provider as reasonable criteria for the use of air medical transport. In a review of 558 consecutive patient transports, 98% had met at least one of the AAMS criteria.81 The risk of aeromedical transport can be placed in perspective if the overall risk for death using ground transport, estimated from the trauma score, is compared with the risk when patients are transported by air. Assuming a reduction in risk of between 21% and 52% when transport is by air, the additional risk for death from crashes (6 per 100,000 transports, or 0.006 per transport) is negligible in comparison to the benefits. This is probably true, however, only for patients with moderate to severe, but nonmortal, injuries (i.e., trauma scores between 5 and 14). Those having minor injuries, with near 100% likelihood of survival, are unlikely to gain additional benefit; those having mortal injuries, with little hope of survival, are unlikely to be saved by any means attempted or employed. The decision to transport a patient by air requires judgment and a realistic appraisal of the risks. A patient should be transported by air only if he or she is so ill that transport is necessary; if ground transport is unavailable, delayed, or unable to reach the patient; or if aeromedical transport would reduce the risk for death by permitting more rapid access to definitive care, providing greater medical skill en route, or both.83


SPECIAL PROBLEMS IN

AEROMEDICAL TRANSPORT

Trauma Aeromedical evacuation experience during operations in Afghanistan and Iraq have shown that large numbers of even severely injured patients can be moved long distances by air if proper equipment and personnel are available to carry out the transport. In July 2004, 2121 patients were moved by the USAF: 39 (1.8%) required transport by CCAT teams. In many instances, critical trauma patients are moved after “salvage surgery,” in which initial surgical care is limited to stopping bleeding and limiting contamination, with expectation of further surgery for definitive repair. Patients have been moved with open abdomens and with intracranial pressure monitors, ventriculostomies, and wound vacuum drainage devices in place. In one case, a patient was successfully flown from Hawaii to California while on cardiopulmonary bypass. Transport of severe trauma victims requires careful attention to proper resuscitation, pain control and sedation, fracture stabilization, and temperature control. Abdominal and chest injury patients are frequently flown while on ventilator support; proper attention to sedation, analgesia, antibiotic administration, and neuro-

Chapter 35: Aeromedical Transport muscular paralysis is required. Patients with even a minor pneumothorax must have a chest tube in place before flight.53,107 Blood and blood products can be given in flight; however, careful attention must be given to proper refrigeration of blood and blood products. Blood administration protocols for use in flight should mirror standard practices for administration of blood and blood products, and medications to deal with transfusion reactions must be immediately available.107

Burns Burn critical care and transport are both very similar and very different from standard critical care and transport. As in any aeromedical evacuation, careful planning is the key to successful transport.44 Transport of significant burn victims is best accomplished as early as possible in the course of the burn injury, preferably in the first 24 to 36 hours after injury. If there is any evidence of significant smoke inhalation or thermal injury to the orotracheal area (i.e., carbonaceous sputum, hoarse voice, singed nasal hair), the patient should be intubated before flight. Circumferential third-degree burns may require escharotomy before flight. Burn victims require careful temperature monitoring during flight to avoid hypothermia. Fluid resuscitation algorithms may need to be modified to compensate for increased insensible water losses due to low cabin humidity. Monitoring urine flow hourly is mandatory in burn patients.53 The U.S. Army Institute for Surgical Research (ISR) at Brooke Army Medical Center in San Antonio, Texas houses the only dedicated burn unit in the U.S. military. The ISR has several burn transport teams that specialize in short- and long-range transport of critical burn patients (Fig. 35-16). Teams generally

A

B Figure 35-16. A, Two “burn victims” (actually manikins) being transported by the U.S. Army Burn Transport Team during a training mission on board a U.S. Air Force C-17 aircraft (B). (Photos courtesy of Robert C. Allen.)

793

include four personnel and about 800 pounds of medical equipment. These teams train alongside, and work closely with, USAF CCAT teams and aeromedical evacuation crews.

Infectious Disease Patients Transport of infectious patients may be a hazard to the flight crew, medical crew, and other passengers because everyone on board the aircraft is sealed in an aluminum tube for hours, sometimes breathing recirculated air. Airflow patterns inside the aircraft cabin may contribute to the problem, wafting fomites downwind of a patient. Several cases of severe acute respiratory syndrome (SARS), influenza, and tuberculosis have been attributed to passenger-to-passenger transmission on commercial aircraft.56,61,80 Standard infection control practices, including wearing gloves, masks, and gowns (as required), should be followed with all patients, not just those suspected of being contagious. Handwashing facilities on aircraft are likely to be nonexistent;

Box 35-6. Communicable Disease Checklist RULE-OUT CHECKLIST (HIGHLY TRANSMISSIBLE INFECTIOUS DISEASE AGENTS)

• Any history of exposure to sewage, body fluids, animals prior to illness? • Any report of insect bites? • Did progression to severe symptoms and illness occur rapidly, over a period of less than 3 days, once the patient began to feel ill? • Fever (temperature greater than 102.0° F [38.9°C])? • Any bleeding from gums? • Any nose bleeds? • Any report of petechiae on the palate, throat, or on exam of the mouth? • Are the patient’s eyes “bloodshot” in appearance, typically described as “conjunctival injection” in medical terminology? • Any report of tender or painful lymph nodes? • Any report of lymph nodes with a “bruised” or darkened appearance? • Any report of “matted lymph nodes,” “goose-egg” lymph nodes, or lymph nodes draining pus? • Any report of petechiae or purpura on the skin? • Any report of bloody stools, melena, hematochezia, hematemesis? • Any report of a positive “tourniquet test”? (NOTE: This test is performed by inflating a BP cuff on an extremity. It is considered a positive test if petechiae appear on the skin of the extremity distal to the cuff and is a very good indicator of vasculitis associated with hemorrhagic fever agents.) • Any report of icterus (yellow eyes, skin, or tongue)? • Any report of cough and fever in conjunction with any of the following:  rapid disease progression?  petechiae, purpura?  lymphadenopathy? • Any report of “pox” or “poxlike” skin rash or lesion? NOTE: Answering “yes” to any one question requires immediate telephone consultation with the theater validating flight surgeon. (Data from references 5, 6, 14, 40, 42, 75, 83, 85.)

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PART FIVE: RESCUE AND SURVIVAL

use of waterless hand cleaners such as alcohol gel is the next best thing.114 Patients in the early stages of some highly infectious diseases may not present with obvious symptoms, or these symptoms may not be recognized by personnel inexperienced in infectious disease or tropical medicine. To help aeromedical evacuation crews evaluate patients before flight, USAF aeromedical evacuation crews are supplied with a checklist of symptoms (Box 35-6). The patients’ clinical signs and symptoms are compared with the list, and if any “yes” answers are found, the aeromedical evacuation crew is required to seek additional guidance from a higher medical authority before allowing the patient on the aircraft. In most cases, patients with contagious diseases can be safely moved by air simply by applying appropriate infection control procedures. Precautions required for transporting an infectious disease patient depend on the pathophysiology and means of contagion. For example, although malaria is an infectious disease, it is not a significant contagion hazard onboard an aircraft, whereas pulmonary tuberculosis is a significant contagion hazard. However, this hazard can be mitigated by the patient and medical crew wearing N95 masks, proper handwashing techniques, and making sure the patient is seated downwind and well away from other patients or passengers.114 Patients suspected of having highly contagious diseases can be moved by specialized transport teams. The U.S. Army Medical Research Institute for Infectious Disease at Ft. Detrick, Maryland has a portable Biological Level IV patient transport system capable of moving two patients with highly contagious disease.5 The British Royal Air Force has a similar system, which

36

it has used to transport patients suspected of having diseases such as Lassa fever. However, in most cases, such units are not necessary; standard infection control practices modified for the flying environment suffice. An outstanding paper on aeromedical transport of infectious patients was authored by Withers and Christopher.114


SUMMARY Aeromedical transport, like most other endeavors in medicine, requires teamwork and good communication. Cooperation between the sending and receiving medical facility, the medical aircrew, and the cockpit crew is vital to a successful mission. It has been estimated that emergency aircraft transport of sick and injured patients has allowed more than 1 million patients to be transported over 100 million miles. With a conservative estimate of mortality reduction of even 10%, close to 100,000 patients may owe their lives to the speed and skill provided by aeromedical transport teams.51


DISCLAIMER The opinions expressed in this chapter are those of the author and do not necessarily represent the opinion of or endorsement by the Department of Defense or the U.S. Air Force. The references for this chapter can be found on the accompanying DVD-ROM.

Essentials of Wilderness Survival Warren D. Bowman and Peter Kummerfeldt

This chapter is concerned with the general principles of wilderness survival, particularly in temperate and moderately cold (nonpolar) environments such as the mountains of the American West. For additional information, especially on specific environments, please refer to Chapter 9, which covers polar medicine, Chapter 37 on survival in the jungle, Chapter 38 on survival in the desert, Chapter 85 on wilderness navigation techniques, Chapter 1 on high-altitude medicine, and Chapter 65 on living off the land. The term survival means to “continue to live or exist” and implies the presence of adverse conditions that make this more difficult. These conditions may, and frequently do, include lack of oxygen, food, or water; the presence of rain, snow, high winds, or temperature extremes without shelter; the complicat-

ing presence of illnesses or injuries; and the necessity to rely completely on the physical, mental, and material resources at hand. As we learned in February 2002, even as powerful and vigorous an individual as 2000 Olympic Greco-Roman heavyweight wrestling champion Rulon Gardner can be significantly injured when marooned alone in subzero weather without proper equipment or shelter. Physicians who participate in wilderness recreation or who treat adventurers need to be aware of the physical, physiologic, and psychological hazards of environmental stress and how related deleterious effects can be prevented and treated in themselves and their patients. Increased leisure time and growing interest in outdoor activities place more people into settings where survival situations may develop. Increasing use of all-terrain vehicles and snow-

Chapter 36: Essentials of Wilderness Survival mobiles has made it easier for novices to get lost or stranded far from help. Along with this, the rise in sedentary lifestyles with inattention to healthy diets, decreased emphasis on physical conditioning, and the apparently increasing incidence of the “metabolic syndrome” (central adiposity, dyslipidemia, insulin resistance, and hypertension) mean a decrease in fitness worldwide. With modern communications and tactics, such as the use of combined helicopter and ground teams, search and rescue operations have become more efficient. At the same time, electronic gadgets, such as cellular and satellite phones, Global Positioning System (GPS) locators, emergency locater transmitters (ELTs) for aircraft, and personal locator beacons (PLBs), have made it easier to get assistance, but have led to an increase in risk taking and a decrease in healthy respect for wilderness, neglect of survival training, decreased provision of survival equipment, and less effective use of simple tools such as maps and compasses. Societal affluence, then, has made it easier both to get into trouble and to get assistance in case of trouble. This chapter’s main thrust is the prevention and successful initial definitive management of such trouble. By paying heed to the recommendations discussed here, the reader will be more apt not only to live through a survival emergency but also perhaps even to do so in relative comfort. The exact type of environmental stress depends on the type, location, and duration of the wilderness experience. Crosscountry skiers, winter mountaineers, and winter campers may be exposed to extremes of cold and storm. Expeditionary mountaineers may explore regions where winter exists year-round and where ambient oxygen is low. Desert or tropical travelers may be exposed to extremes of heat and humidity. Passengers in aircraft, sea craft, or land vehicles may be stranded in almost any type of environment. Requirements for survival (discussed in detail later) are similar whether the subject becomes lost with few resources during a simple day hike or whether injury occurs or severe environmental conditions develop during a well-planned wilderness expedition. Although traveling alone in the wilderness is universally condemned, one must always assume that he or she may be alone and possibly injured when in a survival scenario. Therefore, emergency equipment must be familiar, sturdy, uncomplicated, easy to assemble, and—most important—available immediately. Necessary skills cannot be learned on the job but must be acquired and practiced beforehand so that essential tasks can be accomplished with minimal effort should an emergency arise. Therefore, although improvisation and living off the land are important, anticipation, prevention, and especially preplanning and carrying emergency equipment are vital. As examples taken from polar exploration, Roald Amundsen’s style of thorough preparation and the use of familiar equipment should be emulated, rather than Robert Scott’s careless, arbitrary, and stubborn approach.10 Both of these explorers had extensive polar experience, but Scott elected to use European clothing instead of Eskimo furs and unproven motor drawn sledges and ponies instead of Eskimo dogs. He relied excessively on sled hauling by men on foot, rejected the use of skis, failed to establish enough supply depots for his return, and died of cold, exhaustion, and starvation on the way back from the South Pole. Amundsen, who used Eskimo clothing, well-tested Greenland sled dogs, and experienced skiers, won the race to the South Pole and made it back alive. The outcome of an encounter with severe environmental stress varies with both the stressed person’s resources and

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the type, magnitude, and duration of the stress. These resources include the state of acclimatization; physical integrity— particularly conditioning and the presence of illness or injury; experience; equipment on hand plus the ability to improvise intelligently; and such intangibles as good judgment and “backcountry common sense.” A common judgment error is to insist on traveling during a storm or other stressful environmental condition when more prudent persons would stay put in a comfortable bivouac. Excuses for this include desiring to reach a predetermined but not essential goal on time, so that others “will not worry.” Recall the old adage (attributed to Will Rogers) that “good judgment comes from experience; experience comes from bad judgment.” To this we should add “. . . provided you survive the bad judgment.” The most important resource, however, may well be the will to survive. This may be inbred in some persons, can be established through training and experience in many, and is impossible to acquire in a few. Without a will to survive, the best training and resources may be useless. With a strong will to survive, however, persons have survived incredible hardships. A recent example is Aron Ralston, an expert climber who at the time of his accident had done successful winter solo climbs of 45 of the 59 Colorado peaks of more than 14,000 feet (4267 m) elevation (see Ralston [2004] in “Suggested Readings”). On Saturday, April 26, 2003, he parked his truck at a trailhead and entered deep and narrow Horseshoe Canyon in Utah’s Canyonlands National Park. After about 8 miles (12.8 km) down the canyon, he reached a narrow, 12-foot (3.7-m) high chimney-like dropoff that narrowed to about 3 feet (0.09 m) wide at its bottom. He stepped down onto a large boulder wedged a foot below its top and started to lower himself over the boulder’s edge. The boulder stirred and, before he could get out of its way, it fell, struck his left hand, then jammed into the lower end of the chimney, pinning his right hand and wrist against the floor of the chimney. For tools, he had carabiners, rope, slings, and a Leatherman multitool; for sustenance, he had a liter of water and two bean burritos. He was expected to be at work on Monday in Aspen, Colorado, but had told no one where he was going. Over the next 5 days, he attempted unsuccessfully to move the boulder with a rigged pulley system of rope and carabiners, and to scrape away enough of the boulder with the large knife blade of his multitool to free his hand. He became weaker and more dehydrated, starting to hallucinate intermittently. After he ran out of water he was reduced to drinking his own urine. By Thursday, severely starved and dehydrated and almost ready to give up all hope, he decided that his only choice was to free himself by amputating his trapped hand and wrist. His knife was too dull to cut the forearm bones but he was able to break both of them just above the wrist by forcefully bending the wrist over the edge of the bounder with his free hand. He then applied a tourniquet and cut himself free using the small knife and wirecutting pliers from the multitool on the remaining tissues. Following this, he was able to reach water and refresh himself enough to hike 6 miles down the canyon toward his truck. At this point he met a party of hikers, who were able to alert the Park Rangers and get a helicopter evacuation. After multiple surgeries and a bout with osteomyelitis, Aron is climbing again with a specially designed right forearm prosthesis. Although based on science, the study and practice of survival is more a craft or learned skill than an exact science. The recommendations in this chapter are based on the opinions of

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survival experts, research, analysis of actual survival situations, and personal experience. General principles are emphasized, but “tricks of the trade,” which are usually acquired only through experience, may hold the key to life or death. Unfortunately, much of the lay literature emphasizes tales of misfortune, hazardous adventures, and mindless bravado in the face of unnecessary hardships brought on by errors of the participants, whereas great deeds go unrecorded or forgotten because the experience and competence of the adventurers kept catastrophic “newsworthy” experiences to a minimum. In the words of Corneille, “To vanquish without risk is to triumph without glory.”5 Travelers should always plan for the unusual and unexpected. Tools include familiarity with weather forecasts, strategizing worse-case scenarios, carrying emergency items, avoiding solo travel, and leaving notice of the projected route and expected time of return. With good planning, deteriorating weather or an injury-forced bivouac becomes more of an inconvenience than a life-threatening ordeal. However, chance always plays a part in survival. Serious but unforeseen or unavoidable hazards can occur, or environmental stresses can become so severe that survival is impossible regardless of preparations. Anyone venturing into wilderness must accept the possibility, however remote, of death or serious injury. For survival, the body requires a constant supply of oxygen; a core temperature regulated within relatively narrow limits (about 24°–42° C [75°–107° F]); water and food; and selfconfidence, faith, and the will to live. For comfort and optimum performance, however, body temperature must be close to normal, and the body must be rested, well nourished, in top physical condition, and free from disease and injury. The most immediate of these latter requirements are maintenance of body integrity (through accident prevention) and regulation of body temperature. Dehydration, starvation, and exhaustion make temperature maintenance more difficult and interfere with the rational thought and agility required to prevent accidents. Insufficient oxygen becomes a contributing factor at extreme altitude or in such mishaps as suffocation caused by avalanche burial or carbon monoxide (CO) poisoning from cooking in an unventilated shelter. Abundant food and water are of little value to a hypothermic person with insufficient clothing and shelter or to the victim of heat stroke, even though lack of food and water will eventually weaken and kill an otherwise healthy individual. Lack of self-confidence, faith, and the will to live may cause an attitude of panic and defeatism that prevents a person from taking timely survival actions, such as conserving energy, preparing shelter, or lighting a fire. Poor physical conditioning or the presence of illness or injury may interfere with the body’s ability to produce heat by shivering or to lose heat by sweating and increasing skin perfusion, and can hamper wood gathering, shelter building, and other necessary tasks.3 The most important human organ for survival is the brain because voluntary actions such as preparedness, regulation of energy expenditure, adjustment of clothing, and providing shelter are more important than involuntary mechanisms of adaptation to environmental stress.


OXYGEN As a human ascends from sea level, the body is subjected to increasing cold, decreasing oxygen, increasing solar radiation,

and decreasing atmospheric pressure. For every 305 m (1000 feet) of altitude gain, the ambient temperature drops by about 2.2° C (4° F), the barometric pressure drops by about 20 mm Hg (i.e., 27 millibars [mb], or roughly 0.1 mb drop per meter of altitude gain), and the amount of ultraviolet (UV) radiation increases by about 5%. The percentage of oxygen in the atmosphere remains constant, but the partial pressure of oxygen diminishes with altitude, so that at 3077 m (10,000 feet), it is only two-thirds that at sea level, and at 5488 m (18,000 feet), only half.3 During acute exposure to high altitude, the effects of hypoxia initially can cause fatigue, weakness, headache, anorexia, nausea, vomiting, dyspnea on exertion, insomnia, and CheyneStokes respirations. These symptoms are probably present to some degree in everyone who goes rapidly from sea level to 2462 m (8000 feet) or above. The clinical effects of hypoxia are often difficult to distinguish from those of cold, high winds, dehydration, and exhaustion. Serious degrees of acute mountain sickness (AMS) are unusual below 3692 to 4308 m (12,000–14,000 feet) but have been reported in trekkers as low as 2308 m (7500 feet). In Yellowstone National Park, mild AMS is not infrequently seen in visitors at just over 1829 m (6000 feet). At any height, oxygen in ambient air may be prevented from reaching the cellular level because of interruption of normal transport pathways, generally by illness or injury. CO poisoning is probably a greater hazard than is generally appreciated. Many famous polar explorers, including Byrd, Andree, and Stefannson, were killed by or had narrow escapes from the effects of stoves operated in tightly enclosed spaces.12,17


REGULATION OF

BODY TEMPERATURE

Humans are called homeotherms because as warm-blooded animals they maintain a body temperature that varies within very narrow limits despite changes in environmental temperature.2,3 In poikilotherms, or cold-blooded animals, body temperature varies with that of the environment. Homeothermy is necessary to support the enzyme systems of the human body, which function best at 37° to 37.5° C (98.6°–100° F). The human body can be viewed as a heat-generating and heatdissipating machine, where internal temperature is the net result of opposing mechanisms that tend to increase or decrease body heat production, increase or decrease body heat loss, and increase or decrease addition of heat from the outside. Through these mechanisms, the internal body temperature usually can be regulated successfully, despite ambient temperatures that vary more than 55° C (100° F) from the coldest to the hottest seasons in temperate climates. Basal body heat production is about 50 kcal/m2/h. This can be increased by muscular activity (involuntary [shivering] and voluntary), eating, inflammation and infection (fever), and in response to cold exposure. Shivering can increase heat production up to five times the basal rate and vigorous exercise up to 10 times. Cold exposure increases hunger, the secretion of epinephrine, norepinephrine, and thyroxin, and semiconscious activity such as foot stamping and dancing in place. Eating provides not only needed calories but also the temporary increase in basal metabolic rate occurring during digestion alone (specific dynamic action, or SDA). The SDA of protein is five to seven times higher than that of fat and carbohydrate and lasts

Chapter 36: Essentials of Wilderness Survival

Wind mph Calm 5 10 15 20 25 30 35 40 45 50 55 60

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Temperature (°F) 40 36 34 32 30 29 28 28 27 26 26 25 25

35 31 27 25 24 23 22 21 20 19 19 18 17

30 25 21 19 17 16 15 14 13 12 12 11 10

25 19 15 13 11 9 8 7 6 5 4 4 3

20 13 9 6 4 3 1 0 1 2 3 3 4

15 7 3 0 2 4 5 7 8 9 10 11 11

Frost bite in >>

10 1 4 7 9 11 12 14 15 16 17 18 19

5 5 10 13 15 17 19 21 22 23 24 25 26

0 11 16 19 22 24 26 27 29 30 31 32 33

30 min

5 16 22 26 29 31 33 34 36 37 38 39 40

10 min

10 22 28 32 35 37 39 41 43 44 45 46 48

15 28 35 39 42 44 46 48 50 51 52 54 55

20 34 41 45 48 51 53 55 57 58 60 61 62

25 40 47 51 55 58 60 62 64 65 67 68 69

30 46 53 58 61 64 67 69 71 72 74 75 76

35 52 59 64 68 71 73 76 78 79 81 82 84

40 57 66 71 74 78 80 82 84 86 88 89 91

45 63 72 77 81 84 87 89 91 93 95 97 98

5 min

Figure 36-1. Windchill chart. (From Bowman WD, Johe DH, American Academy of Orthopaedic Surgeons, National Ski Patrol System [U.S.]: Outdoor Emergency Care: Comprehensive Prehospital Care for Nonurban Settings, 4th ed. Boston: Jones & Bartlett, 2003, p 32, Figure 2-5.)

longer. However, the onset of the SDA is much faster with carbohydrate than with protein or fat. Therefore, the person who is cold inside a sleeping bag at bedtime should eat carbohydrate for quicker warming, and protein to stay warm all night. In hot weather, body heat production can be decreased by slowing muscular activity and avoiding foods with a high SDA. In cold weather, heat can be added to the body by close exposure to a fire or other heat source, such as sunlight, and by ingesting hot food and drink. In hot weather, external heat addition can be decreased by staying in the shade, wearing clothing that blocks the sun’s rays, and avoiding hot objects and hot food and drink. The body loses heat to the environment by conduction, convection, evaporation, radiation, and respiration. It may gain heat from the environment by the same mechanisms (except for evaporation). The relative importance of these mechanisms depends on temperature, humidity, wind velocity, cloud cover, insulation, contact with hot or cold objects, sweating, and muscular exercise. With a resting body in still air at 21° C (70° F), radiation, conduction, and convection account for about 70% of total heat loss, evaporation for about 27%, and urination, defecation, and respiration for only 3%. During work, however, evaporation may account for up to 85% of heat loss.3 It is useful to think of the body as composed of a core (heart, lungs, liver, adrenal glands, central nervous system, and other vital organs) and a shell (skin, muscles and extremities). Most of the physiologic adjustments in response to cold or heat exposure occur in the shell. They are designed to maintain a relatively constant core temperature; in below-freezing weather, these adjustments may predispose parts of the shell to frostbite and other types of localized cold injury. The importance of avoiding travel and seeking shelter during storms and extreme cold cannot be overemphasized. The additive chilling effect of wind when added to cold is impressive. Windchill charts (Fig. 36-1) show the relationship between actual temperature, wind velocity, and “effective” temperature at the body surface. Windchill refers to the rate of cooling; the actual temperature reached is no lower than it would be if wind were absent (unless evaporation of liquid is occurring at the body surface). The increase in heat loss as the wind rises is not

linear but is more proportional to the square root of the wind speed. At moderate ambient temperatures, the body’s core temperature is kept stable by constant small adjustments in metabolic rate, muscular activity, sweating, and skin circulation. When the body is chilled, automatic and semiautomatic mechanisms increase internal heat production by slightly increasing the metabolic rate, by shivering, and by semiconscious activities (e.g., foot stamping), and reduce heat loss by diminishing sweat production and shell circulation. The person has a strong urge to curl up into a ball, thereby reducing the body’s surface area. At the same time, the brain tells the body to decrease heat loss by adding insulation and wind protection, to seek shelter, and to increase heat gain by increasing muscular activity, building a fire, seeking sunlight, and eating.3 When the body overheats, these actions are reversed. The body increases heat loss by increasing circulation to the skin and extremities and increasing sweating. These mechanisms require more water, which stimulates the thirst response. Heat production is decreased because of a feeling of sluggishness and languor, leading to a reduction in physical activity and the amount of heat produced by muscles. The brain tells the body to decrease heat gain and increase heat loss by providing shelter from the sun, removing clothing, and fanning itself.2


COLD WEATHER SURVIVAL Body temperature in a cold environment is maintained by decreasing body heat loss, increasing internal body heat production, or adding heat from the outside. The most efficient of these methods is conservation of body heat by decreasing heat loss, generally by using clothing and shelter.


DECREASING BODY HEAT LOSS Heat loss from conduction and convection can be prevented by interposing substances of low thermal conductivity, such as clothing made of insulating materials, between the body and the outside air. Clothing creates a microclimate of warmed, still air

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TABLE 36-1. Fiber Characteristics of Natural and Synthetic Fibers FABRIC Wool Cotton Nylon Polyester Acrylic Polypropylene

SPECIFIC GRAVITY* (RATIO TO WATER)

THERMAL CONDUCTANCE† (cal/m2)

EVAPORATIVE ABILITY‡

WICKING ABILITY

MOISTURE REGAIN§

1.32 1.54 1.14 1.38 1.15 0.91

2.1 6.1 2.4 2.4 2.4 1.2

Low Low High High High High

Moderate High Low Low High High

17 7.9 4 1 1 5

*The lower the specific gravity, the better the insulating ability. † The lower the thermal conductance, the slower the flow of heat from the body. ‡ The higher the evaporative ability, the shorter the amount of time a fiber will be wet, that is, in a reduced insulative state. § Moisture regain is the amount of moisture a fiber can absorb before feeling wet. Modified from Davis AK: Nordic Skiing: A Scientific Approach. Minneapolis, University of Minnesota, 1980.

next to the skin surface. Clothing’s value depends on how well it traps air, the thickness of the air layer, and whether these qualities are reduced by wetting (Table 36-1). Traditional insulating materials are wool, down, foam, and older synthetics such as Orlon, Dacron, and polyester. Wool retains warmth when wet because of a moderately low wicking action and a unique ability to suspend water vapor within its fibers without affecting its low thermal conductance. It can absorb a considerable amount of water without feeling wet but is heavier than synthetics, itchy, and more difficult to dry. Its toughness and durability, however, make it a good choice for garments subject to hard wear, such as trousers, mittens, and socks. Cotton, particularly denim and corduroy, is a poor insulator. It dries slowly because of low evaporative ability; high thermal conductance is further increased by wetting. Cotton has no place in the backcountry in cold weather. Orlon, acrylic, and polyester were developed to duplicate wool’s properties without wool’s higher cost and other perceived drawbacks. They traditionally have been used in hats, shirts, sweaters, and long underwear. They are almost as warm and not as itchy as wool, and they evaporate moisture better. A number of newer fabrics are woven from fibers that have lower thermal conductance, greater insulating ability, and better wicking action than traditional fibers. Examples include polypropylene and treated polyesters, such as Capilene, Thermax, and Thermastat. Polyester is also made into pile and fleece, which are light, dry easily, trap air well, and stay warm when wet because the fibers do not absorb water. Examples are Polartec, Borglite, Polarplus, and Synchilla. Fibers used as fillers in quilted garments, such as parkas, include hollow synthetic fibers designed on the principle of reindeer hair, such as Hollofil II and Quallofil. Microfibers that provide good insulating ability with less bulk include Thinsulate, Thermoloft, and Thermolite. One of the newer fibers, Microloft, is supposed to be warmer than down at the same weight. New synthetics come on the market frequently, so one should consult trade journals and “gear” issues of outdoor magazines, such as Backpacker.2,3 The “layer principle” of clothing is effective in preventing both chilling and overheating. Multiple layers of clothing provide multiple layers of microclimate. Layers are added as necessary to prevent chilling or subtracted to prevent overheating that would lead to perspiring. Because water conducts heat 25 to 32 times faster than air at the same temperature, clothing wetted by perspiration or water may cause rapid heat loss

from conduction and evaporation. The need to add or subtract layers should be anticipated before either chilling or heavy perspiring occurs. Clothing should be easily adjustable, sweaters should be of the zipper or cardigan type, and outer layers should be cut full enough to allow expansion of inner layers to their full thicknesses. Zippers in the axillary, lateral chest, and lateral thigh areas are useful for ventilation. Loss of heat from convection can be prevented by wearing windproof outer garments of nylon, tightly woven cotton-nylon blends, or water-resistant laminates such as Gore-Tex. Typical examples include a parka with hood and a pair of windproof pants (regular or bib style) or ski warm-up pants. The loss of heat from infrared radiation can also be prevented by insulation, emphasizing proper covering for body parts with a large surface area to volume ratio. The uncovered head can dissipate up to 70% of body heat production at an ambient temperature of −16° C (5° F), partly because the body does not reduce blood supply to the head and neck as it does to the extremities in cold weather. High heat loss through radiation during cold nights can be decreased by sleeping in a tent or under a tarpaulin (tarp) instead of in the open. Coverage for the head, ears, hands, and feet should not restrict circulation. Developed initially for skiers, the “neck warmer,” or “neck gaiter,” can be pulled up over the back of the head to form a hood or up over the lower face to form a mask. In addition to head and neck protection, this device also blocks some of the heat that would otherwise be lost by the bellows action of clothing caused by body motion. Heat loss from the respiratory tract can be diminished by avoiding overexertion and overheating that occur with excessively heavy breathing. When it is extremely cold, inspired air can be warmed by pulling the parka hood out in front of the face to form a “frost tunnel.” Heat loss from conduction occurs by direct contact with a colder object. Sitting on a pack, foam pad, log, or other object of lower heat conductivity is preferable to sitting in the snow or on a cold rock. At low temperatures, bare skin freezes to metal. This can be avoided by wearing light gloves when handling metal objects. Gasoline or other liquids with freezing points lower than that of water can cause frostbite if accidentally poured on the skin at low temperatures. During bivouacs in snow shelters, contact with the snow can be avoided by sitting on a foam pad or backpack or improvising a mattress of

Chapter 36: Essentials of Wilderness Survival evergreen boughs, grass, or dry leaves. In cold or windy weather, an injured person needs windproof insulating material under as well as over and around the body. Heat loss from conduction and evaporation can be lessened by avoiding wetting and by changing to dry clothes or drying out quickly when wet. Ideally, outer clothing should be windproof, should not collect snow, and should shed water but not be waterproof because waterproof garments prevent evaporation of sweat. Laminated fabrics, such as Gore-Tex and its relatives, are suited for this and for outermost layers.

Dressing for Cold Weather Anyone who ventures outdoors in cold weather should have enough clothing of the proper kind, either on the body or in the backpack, for the most extreme environmental conditions likely to be experienced. Even though fire-building, carrying emergency shelters, and improvising survival shelters are discussed at length later in this chapter, the process of dressing for cold weather should be approached with the idea that clothing may become the only “shelter” and endogenous heat production the only heat you have available. Clothing and other types of insulating materials should be selected with the idea that they need to keep one warm and dry even during periods of inactivity.

First Layer Long Underwear. Wool is an excellent choice for long underwear but is expensive and may be difficult to find. Merino wool is less itchy. Polypropylene, acrylic, and the newer polyesters may be preferable because of their lower cost, good insulating ability, and outstanding evaporative ability (Table 36-1). Avoid fabrics containing cotton. Synthetics tend to retain body odor more than wool after washing. Socks. One or two pair of moderate to heavy wool or woolnylon blend socks are excellent, preferably with an additional pair of light polypropylene socks worn underneath next to the skin. Consider carrying at least one spare pair of wool socks. Thin Gloves (Glove Liners). Light polypropylene, wool, silk, or fingerless wool or pile gloves are useful for moderately cold conditions or when finger dexterity is required, as in adjusting ski bindings. Polyester/Lycra gloves provide a tighter but more stretchable fit, which enhances fine finger movements.

Second Layer Shirt. Shirts should be made of light, soft wool or a durable synthetic such as acrylic, and should have long sleeves. Large breast pockets with buttons or Velcro fasteners are handy to carry such items as sunglasses and a compass. For ventilation, the front of the shirt should open completely or at least halfway (buttons or zipper closure). A turtleneck feature protects the neck, as do neck warmers and mufflers that can be pulled up to protect the lower face. Pants. Wool or pile pants are best and should have pockets that are easily accessible for hand warming. Pile pants should have reinforcements at the knees and buttocks and a zipper or Velcro fly for males. Full or partial lateral leg zippers are convenient. Foot Gear. The type of boot chosen depends on the type of activity and the expected environmental temperatures. For mod-

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erate temperatures, sturdy leather climbing boots made of fullthickness leather, 6 to 8 inches in height with rubber lug soles and roomy enough to accommodate the desired numbers of socks, are ideal. Boots made of leather and fabric, such as GoreTex, are lighter and suited for trail hiking, but may not be as durable for rough terrain. Boots must be long enough so that the toes do not strike the front of the boot during downhill walking. They should be laced firmly enough that the heel does not move up and down, but not so tightly that circulation is restricted and the toes cannot be wiggled easily. For colder temperatures, double boots are preferable. These can be all-leather boots or can have outer shells of plastic or nylon with inner boots of felt or foam. All-leather versions may be difficult to obtain. The Canadian type of shoe-pack with a removable inner felt liner is a good choice for light snowshoeing and other nontechnical outdoor activities in the cold. Special double ski boots are available for ski touring, Telemark skiing, and ski mountaineering, depending on whether three-pin or rondonnee bindings are used.

Hat. Hats should be of the stocking variety, made of wool, pile, Orlon, polypropylene, or wool-polypropylene, and large enough to cover the ears. A small bill feature is desirable to shade the eyes. “Bomber” caps with bills and pull-down earflaps and “Andean” caps with ear coverings are popular. Some arrangement should be provided to protect the face from cold wind, as with a balaclava configuration or a separate face mask. A useful combination for very cold, windy weather is a ski hat together with a neck warmer that can be pulled up to cover most of the lower face, plus using the parka hood.

Third Layer Parka. The parka can be a standard ski or mountain parka filled with down, Dacron, Quallofil, Thinsulate, or other lofting material. A more versatile combination is two separate garments: a pile jacket plus a water-resistant shell. For snow-camping, a pile jacket with a thin outer cover of nylon (three-season, squall, or warm-up jacket) may be preferred because, unlike an uncovered pile jacket, it does not collect snow when worn without the shell. The shell should have a hood with a drawstring, a two-way zipper with an overlying weather flap closed with full-length Velcro (in case of zipper failure, very cold hands, or upper extremity injury), a cloth flap to protect the chin from the metal zipper pull, armpit or lateral chest zippers for ventilation, and at least four outer pockets plus one or two inside pockets to contain frequently needed items (e.g., gloves, compass, map, sunglasses, neck warmer). Outer pockets should be located where they can be reached while wearing a backpack with a fastened waist belt. The shell should be fingertip length unless bibs are worn. Zippers should have extra-long tabs added to facilitate closure with cold or mittened hands. Pockets with horizontal openings may close with Velcro, but those with vertical openings should close with zippers. Because the parka is anchored by the shoulders, when using one hand, it is generally easier to pull a vertical zipper down than up. In some brands of parkas (e.g., Columbia, Marmot, Moonstone, and Patagonia), vertical zippers are pulled down to close the pockets; in other brands, they are pulled up. The senior author prefers the former type because the danger of losing pocket

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contents from difficulty closing a zipper is worse than any perceived delay from difficulty opening a zipper. For ventilation, there should be zippered openings at the armpits. These should be large enough so that the parka can be converted into a vestlike garment during warm conditions by inserting the wearer’s arms through the openings and tucking the sleeves inside the parka. Because these zippers usually perform more easily when pulled from the distal to the proximal direction, this direction should close them; increasing wind protection is usually more urgent than decreasing it (freezing is more dangerous than sweating).

Wind Pants. These should be light and water repellent; a laminated garment such as Gore-Tex is a good choice. Long, zippered side openings are useful to permit donning pants without removing boots, as well as for ventilation and access to inner pants’ pockets. Hand Gear. Mittens and gloves provide hand protection from trauma and cold. Because survival depends to some extent on normal hand dexterity, gloves or mittens should be available to protect hands from cuts, bruises, blisters, and resulting infections. In temperate weather, these can be light, unlined leather gloves. One of the more serious and still unsolved cold weather problems is how to keep fingers warm while leaving them sufficiently unhampered to do work. Mittens are warmer than gloves because fingers that touch each other warm each other, but even thin mittens do not allow delicate finger movements. An important part of the cold finger solution is to prevent core cooling and compensatory extremity vasoconstriction by addressing core temperature stabilization through exercise, eating, and wearing enough layers on the trunk. A common strategy is to wear a pair of thin gloves of polypropylene, silk, thin wool, or polyester-Lycra inside a wool or pile mitten covered with a windproof and water-resistant glove shell. For delicate finger work, the gloved hand is removed from the mitten, the work done as fast as possible, and the hand returned to the mitten. However, because insulating materials insulate in both directions, when inside a warm mitten, cold fingers wearing gloves will not rewarm as fast as cold, bare fingers. Therefore, another solution is to use bare fingers, which will perform faster than gloved fingers, work as fast as possible, and return them to warm mittens periodically until the task is done. This is not practical, however, when working with metal in very cold weather. Another approach is to keep a pair of gloves warm in a pocket and put them on after removing the hands from mittens. Polyester-Lycra gloves are easier to don than are many other types of thin gloves. Excellent three-layer mitten sets include windproof shells with leather palms and two sets of removable pile mittens, at least one of which is fastened to the inner shell with Velcro. Another good system is a thin glove liner inside a heavy wool (Dachstein, rag wool, or wool-polypropylene) mitten inside a Gore-Tex shell. An option that gives more finger dexterity in moderately cold conditions is a polypropylene glove liner inside a fingerless wool glove inside a shell. A new combination is a fingerless wool glove inside a wool mitten that has a horizontal slit in the distal palm (Cordova’s rag wool convertible gloves). The distal tip of the mitten can be folded backward dorsally and secured with a Velcro patch, allowing the hand covered with the fingerless wool glove to be exposed through

the slit. However, more layers and increasing complexity mean more difficulty doing delicate hand tasks. Shells should have easily accessible “nose warmers” of pile or mouton on the backs, should be long enough to cover the wrists, and should have palms of soft leather or sticky fabric for securely holding ice axes and ski poles.

Gaiters and Over-boots. Gaiters, which are long, nylon tubes that cover the lower leg and upper part of the boot, are designed to keep snow, sand, and gravel out of boots and socks. They extend upward to just below the knee, open at the side or in front with a zipper or Velcro, and have a strap that fits under the boot sole to keep them snug on the boots and a drawstring at the top to hold them up. Gaiters with a front opening closed by a wide Velcro strap are easiest to get on and off. Shorter versions that extend to just above the ankle are adequate for summer mountaineering and may be preferable for crosscountry skiers who need access for tightening boot buckles before descents. High altitude mountaineering requires special insulated overboots or lined gaiters.

Fourth Layer The previous three layers are usually worn on the body. A fourth layer should be easily available in the pack. This should include quilted or pile pants and jacket (or vest).

Rain Gear In moderate climates or in spring conditions when rain and wet snow may be encountered, outer garments of Gore-Tex or similar material should be used. For maritime climates and during seasons of heavy rain, it may be better to have two separate sets of outer garments: a light, thin windproof nylon jacket and pants and a waterproof (coated nylon) jacket and pants.

Vapor Barrier Systems Waterproof garments and sleeping bag liners worn close to the skin are favored by many because they can prevent wetting of outer clothing by sweat that might result in decreased insulating capacity. There also is claimed to be some reduction in water consumption requirements. Such “vapor barriers” seem to work better in very cold weather than at moderate temperatures. A light garment of polypropylene or similar material should be worn next to the skin, with the waterproof garment over this. Vapor barrier systems should probably be tried out in the field in nonsurvival conditions before being relied on in severe weather. Persons with hyperhidrosis and those who dislike clammy skin may not feel comfortable with them.


SHELTER Summer Emergency Shelters When faced with an unplanned night out, one’s first step should be to locate a place out of the wind. Getting behind a rock, moving to the lee side of a ridge, going down into the treeline, or even turning one’s back to the wind can make a difference. Eliminating windchill allows one to concentrate on dealing with ambient air temperature by using natural insulation and starting a fire. Look for a space into which you can crawl, such as a rocky overhang or a space under dense evergreens or fallen logs. Experienced and prepared individuals will have some type

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of waterproof material (plastic bag, tube tent, or tarp) into or under which they can crawl as well. Bright-colored (orange or red) materials are easier for searchers to spot. Getting out of the wind, rain, or snow quickly and being able to stay as warm and dry as possible are vital. Once one is wet and cold, it may be very difficult, sometimes impossible, to rewarm and dry out.

Mylar Space Blankets and Bags These are lightweight, inexpensive, and compact, but they are of limited value in an emergency. Consider a typical emergency scenario, when it is late in the day, cold, rainy, and windy, and the survivor is injured, hypothermic, or both. A “space blanket” is frequently difficult to get out of the package, to unfold, and to manage in windy conditions. Depending on the brand, space blankets are usually too small to fully encase an adult. When wrapped up, the survivor will find that a space blanket makes a shelter that is so noisy than even an approaching aircraft or ground search party may not be heard. Space blankets also tear very easily when nicked or punctured. The “space bag” has the same flaws as the blanket except that it is easier to encase yourself and stay enclosed.

Figure 36-2. Two large plastic bags can be taped together in tandem and used with a line to form a tube tent. (Photo courtesy of Peter Kummerfeldt.)

Thermal Blankets These are similar to space blankets, but are made from much heavier material reinforced with fiberglass threads and with a grommet in each corner. They can be used as a body wrap, but again, depending on the size of the person, they are often too small to encase an adult. Some survivors have attempted to use a thermal blanket as a shelter roof by tying lines to each corner and then stretching the blanket between various anchor points. In benign conditions, this may work, but with any wind or snow loading, the grommets quickly tear or pull out.

Tube Tents These are usually about 8 feet (2.4 m) long and provide a tubular shelter 3 to 5 feet high, depending on the brand. They can be pulled over the body to provide a quick shelter or pitched as a “pup tent.” To do this, find two anchors (rocks or trees) the proper distance apart and tie a line to one of them, spread the tent out along the length of the line, run the line through it, and tie off the other end of the line. The height of the line should be such that the tent can be spread out to accommodate the occupant. To avoid ripping, the tent plastic should be 3 to 4 mil thick (1 mil = .001 inch or .0254 mm). Tube tents can be improvised from two plastic 55-gallon drum liners (3 to 4 mil thick) or large, heavy-grade household trash bags by opening up the closed end of one bag, sliding it into the open end of the second bag, and then duct-taping the bags together (Fig. 36-2).

Tarpaulins Sheets of Visqueen plastic, painters’ drop cloths, large pieces of canvas, or other similar materials can be used to erect a wide variety of effective survival shelters. “Blue Crinkly” plastic tarps made of a laminated polyethylene weave are readily available and inexpensive. They can be purchased from most hardware stores, come in a variety of sizes, and are usually blue on both sides with grommets in each corner and at intervals along the sides. An 8- × 10-foot (2.4- × 3-m) tarp is needed to protect an adult. Tarps of this size weigh about 26 oz and roll up into a tube 6 inches in diameter by 12 inches long, which is convenient to carry tied to the outside of a daypack or fanny pack. To save

valuable time in a survival situation, tie 10 feet of parachute line to each corner grommet ahead of time. Tarps can be erected in a number of shelter styles, depending on weather conditions (Fig. 36-3). To erect a lean-to shelter (see Fig. 36-3A), first select a line long enough to stretch between two trees far enough apart for the tarp to be stretched tight. Using a timber hitch, tie off one end of a line to one of the trees about chest height. Then, rather than passing the line itself through the grommet eyes, insert a small loop of the line through the first grommet eye, and secure the loop with a short stick thrust through it on the opposite side (see Fig. 36-3B). Repeat this process for each grommet, stretching the tarp tight each time. After the tarp is attached to the line, tie off the other end of the line to the second tree, with the line stretched as tightly as possible. The lower edge of the tarp is then pegged to the ground or anchored with large stones or a length of log. When making pegs, select a length of wood 11/2 to 2 inches (3.8–5 cm) in diameter and twice as long as needed. Using a saw, make one 45-degree cut at the midpoint of the stick. In this way, one cut produces two pegs, both of which are sharp enough to be driven into the ground by pounding their blunt ends with the back of an ax-head or a large rock. Fill in the sides of the lean-to with vegetation. If a fire will be built in front of the lean-to, the front opening should be parallel to the prevailing wind in order to carry the smoke away from the shelter. If not, the back edge of the leanto should point into the prevailing wind. To erect a pup-tent type of shelter (see Fig. 36-3C), tie a line between two trees, drape the tarp over it, and peg down the sides. Block the ends with vegetation or personal equipment. A lean-to with an eave (see Fig. 36-3D) gives more protection from rain and snow than one without. Instead of attaching the long edge of the tarp to the line between the two trees, drape the tarp over the line so that several feet are on the other side and tie the two corners to pegs to form a down-sloping eave. A triangular tarp shelter can be erected rapidly and gives good protection (see Fig. 36-3E). It requires three pegs and an anchor point on a tree.

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A

B

C

D Figure 36-3. Four types of shelters that can be made from a tarp. A, A simple lean-to. B, Illustration of a method for attaching a line to a tarp. C, A pup-tent type of shelter. D, A lean-to shelter with an eave.

When using a tarp without grommets, use improvised buttons instead of cutting a hole in the tarp to attach a line. A small, smooth pebble, pine cone, or similar object is placed under the material, which is then gathered around the object to form a “button” (see Fig. 36-3F, G). Using a girth or clove hitch, attach a line to the base of the button. This method is stronger than tying a line through a hole cut in the fabric and will tear out less easily.

Plastic Bag Shelters Large, heavy-grade (3 to 4 mil) orange plastic 55-gallon drum liners make good short-term emergency shelters. Having one to crawl into quickly will speed warming and drying as well as shelter the survivor from further wetness and chilling. However, total enclosure in a plastic bag is both uncomfortable and dangerous, because of increased wetting from condensation of water vapor in exhaled air and perspiration plus poor ventilation, with lack of oxygen and buildup of carbon dioxide. To minimize these problems, cut an opening in the bottom end of

the bag just large enough for your head. Then, pass the bag over your head so that your face is at the opening (Fig. 36-4). If you get too warm, you can push your head through the hole. When creating the hole, cut the plastic at 90 degrees to the fold to reduce the likelihood of the bag tearing along the seam.

Winter and Cold Weather Emergency Shelters Everyone who spends time in the winter wilderness should practice the construction of several types of emergency survival shelters before they may be needed. The functions of a shelter are to provide an extension of the microclimate of still, warm air furnished by clothing; to contain heat generated by the body, a fire, or other heat source; and to protect from snow, rain, and wind. A properly designed shelter should permit easy and rapid construction with simple tools and should give good protection from wind, rain, and snowfall. The type and size of shelter depend on the presence or absence of snow and its depth, on natural features of the landscape, including the availability of natural building and insulating materials, and on whether fire-

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E

F

Figure 36-3, cont’d. E, A triangular tarp shelter. F, Creating a button for attaching a line to a grommetless tarp. G, Attaching a line to the neck of the button using a girth or clove hitch. (Photo courtesy of Peter Kummerfeldt.)

G wood or a stove and fuel are available. If external heat cannot be provided, a shelter must be small and windproof to preserve body heat. If possible, a shelter should be constructed in the timber to provide protection from the wind and access to firewood. Generally, shelters partway up the side of a ridge are warmer than those in a valley because cold air tends to collect in valleys and basins during the night. Exposed, windy ridges above the timberline are cold. Areas exposed to flooding (drainages, dry riverbeds), rock-falls, cornice falls, or avalanches or under dead trees or limbs should be avoided. If open water is available, the camp may be located nearby, although in nonsurvival conditions, camps should be at least 200 feet from bodies of water. To avoid drifting snow, tents and shelters should be located with the entrance parallel to the prevailing wind.

Snow is a good insulator (Table 36-2). Its heat conductivity is 1/10,000 that of copper, and its insulating ability superior to wool felt, so snow shelters may be warmer than other types of constructed shelters, as long as the inhabitants remain dry. Contact with the snow or cold ground is avoided by sitting on a foam pad, dry leaves, grass, a backpack, or (in survival conditions only) a bed of evergreen boughs.

Natural Shelters Caves and alcoves under overhangs are good shelters and can be improved by building wind walls with rocks, snow blocks, or brush. A fire should be built in such as way that heat reflects onto the occupant. The fire should be 5 to 6 feet from the back of the shelter, with a reflector wall of logs or stones on the opposite side of the fire; the occupant should sit between the fire and

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the back of the shelter (Fig. 36-5). Adjustments may have to be made to prevent too much smoke from reaching the occupant. In deep snow, large fallen logs and bent-over evergreens frequently have hollows under them that can be used as small caves. Cone-shaped depressions around the trunks of evergreens

(“tree wells”) can be improved by digging them out and roofing them over with evergreen branches or a tarp. A fire built to one side of such a shelter will reflect its heat off the snow toward the occupant. Ventilation must be adequate, and the fire should not be positioned under snow-laden branches that can extinguish the fire by dumping snow on it.

TABLE 36-2. Thermal Conductivity of Various Substances SUBSTANCE Air Down Polyester (hollow) Polyester (solid) Snow (old) Cork Sawdust Wool felt Cardboard Wood Dry sand Water Brick Concrete Ice

Figure 36-4. Example of two large plastic bags used to form a one-person survival shelter. (Photo courtesy of Peter Kummerfeldt.)

CONDUCTIVITY*

TEMPERATURE MEASURED (°C)

0.006 0.01 0.016 0.019 0.115 0.128 0.14 0.149 0.5 0.8 0.93 1.4 1.5 2.2 5.7

0 20 – – 0 30 30 40 20 20 20 12 20 20 0

*Conductivity is the quantity of heat in gram calories transmitted per second through a plate of material 1 cm thick and 1 cm2 in area when the temperature difference between the sides of the plate is 1° C.

Figure 36-5. Natural shelter.

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Figure 36-6. Lean-to shelter. Sides should be closed with brush or snow and a fire built in front.

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A

Constructed Shelters When no snow is available, shelters can be built of small trees, branches, brush, and boughs. In cold weather with minimum or absent snow cover, the most satisfactory form is a lean-to with two sides closed with brush or piled snow, a fire at the open front, and a wall of logs or stones on the far side of the fire to reflect heat into the interior of the lean-to (Fig. 36-6). Walls or a roof of brush, branches, or broad leaves should be thatched (i.e., each layer should overlap the one below it).

Snow Shelters If snow shelters become too warm, the walls will be wet, and the roof will drip. A useful rule of thumb is that persons inside a snow shelter should be able to see his or her breath at all times.19 Snow shelter building should be practiced and perfected beforehand under nonsurvival conditions.

B Figure 36-7. Emergency snow trench. A, Pit is dug and overlaid with skis and poles. B, Tarp is placed over the skis and secured with snow and heavy objects.

Snow Trenches A snow trench is the easiest and quickest survival snow shelter and the one least likely to make the diggers wet. It can be dug in most areas that are flat or on slight to moderate inclines as long as the snow is 3 feet deep or deeper or can be piled to that depth. A 4- × 6-foot (1.2- × 1.8-m) trench can be dug in 20 minutes, one end roofed over with a tarp or boughs, and a fire built at the opposite end (Fig. 36-7). Again, adjustments may need to be made to avoid excessive smoke exposure, which can be prevented to some extent by situating the long axis of the trench at a right angle to the apparent wind direction. If a large (8- × 10-foot [2.4- × 3-m]) tarp and a stove are available, a trench can be dug that is as comfortable as a snow cave and will hold two or three people. The object is to keep the maximal amount of snow around and over the trench. The trench is dug as narrow as possible at the surface while still providing sufficient room to shovel; a suitable size for the top is 4 feet wide by 8 feet long. It is undercut at the back and sides so that the bottom is 6 to 7 feet (1.8 × 2.1 m) wide by 9 to 10 feet (2.7 × 3 m) long (Fig. 36-8). A narrow entrance helps contain heat and can be closed with a small plastic sheet or a pack. Four or more skis or thick limbs are laid from side to side over the

top of the trench, with ski poles or branches interwoven at right angles. A tarp is then laid on top of these and the snow piled around its edges to hold it down. In very cold weather, the entire tarp can be covered by a layer of snow; at least 8 inches (20 cm) is needed for proper insulation. When the entrance is closed, a small stove and the occupants’ body heat will raise the interior temperature to −4° to −1° C (25°–30° F). Higher temperatures should be avoided so that clothing and bedding will not become wet from melting snow. Above the timberline in deep, wind-packed snow, a similar trench can be roofed with snow blocks that are laid horizontally, set as an A-frame, or laid on skis (Fig. 36-9). Chinks between the blocks are caulked with snow.

Snow Caves Although a small snow cave large enough for one person can be dug with a ski or cooking pot, it is much better to have a shovel. Two shovels are best: a medium-sized general-purpose aluminum scoop shovel and a small, straight shovel (French type) to use while excavating the interior of the cave. The best site is a large snow drift, such as is found on the lee side of a

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Ski poles

Sides and ends undercut

A1

Skis

Narrow entrance

A2

B1

B2

Figure 36-8. A1 and A2, Three-person snow trench. A narrow entrance and narrow top with undercut sides are advisable to trap as much warm air as possible. B1 and B2, Skis and ski poles or stout limbs form the roof support.

small hill. Areas in avalanche zones or under cornices should be avoided. Because the diggers tend to become wet, waterresistant or waterproof jackets and pants should be worn. In the traditional snow cave, the entrance is dug just large enough to crawl through and is angled upward toward the sleeping chamber (Fig. 36-10A), an arrangement that tends to trap warm air inside. It should be large enough for a stove and two occupants lying side by side. After the entrance is dug with the scoop shovel, the digger crawls inside, lies supine, and uses the straight shovel to excavate the chamber until the space is large enough to allow room to use the larger scoop shovel. A long, level bench about a foot higher than the floor of the cave is constructed and used for a sleeping area. A ventilation hole as large as a ski pole basket is cut in the roof over the cooking area. Because the traditional cave takes at least 2 hours to dig and gets the diggers quite wet, the T method has found favor.18 This involves excavating a much larger entrance hole, shaped like a T, so that the digger can stand erect, have plenty of room to

dig, and stay drier (see Fig. 36-10B). The crossbar of the T is at the level of the sleeping bench; the digger stands in the foot of the T. After the cave is finished, the top of the T is closed with snow blocks, leaving the foot of the T as a small access hole. Pine branches or other natural materials are used to cover the floor if a sleeping pad is not available.

Snow Domes When the ground is flat or the snow cover is shallow, snow can be piled into a large dome 6 to 7 feet (1.8–2.1 m) high and left to harden for a few hours (Fig. 36-11). A low entrance is dug on one side, and from there, the interior is carved out to make a dome-shaped room large enough to sleep three people. A ventilation hole is cut in the roof over the stove. Another method is to make a form (pile of vegetation or equipment), cover this pile with snow, allow the snow to set, and then open one end and remove the form.

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Snow piled along edges Tarp

Ventilation hole for cookstove

D

C1

C2 Figure 36-8, cont’d. C1 and C2, Finished trench with snow piled along edges of tarp to hold it down. Note ventilation hole for cookstove. D, Completed trench after a heavy snowfall.

Igloos Igloos are the most comfortable arctic shelters but require time, experience, and some engineering skill. They are not recommended for the novice, but may be worth the effort if the party will be stranded for any length of time. Igloos require one or ideally two snow saws and snow of the proper consistency. Wind-blown snow in a treeless area is best; otherwise, a large area of snow can be stamped well and left to harden over several hours. To mark the diameter of the igloo, a ski pole is held by the handle, pointed to the side, and the body turned so that the pole basket makes a large circle in the snow that outlines the base of an igloo suitable for three people. Cutting some of the snow blocks from inside this circle will lower the floor so that fewer blocks are required for the dome. At least two persons are needed: one to cut and carry the blocks and the other inside the igloo to lay the blocks. The blocks should be about 18 inches wide, 30 inches long, and 8 inches (45.7 cm × 76.2 cm) thick. They are laid in a circle leaning in about 20 to 30 degrees toward the center of the igloo, with the sides trimmed for a snug fit. The tops of the first few blocks in the first circle are beveled so that a continuous

line of blocks is laid, with the first few blocks of each succeeding circle cocked upward (Fig. 36-12). A common error is to not lean the blocks inward enough, resulting in an open tower instead of a dome. Gaps are caulked with snow. The dome should be 5 to 6 feet (1.5 to 1.8 m) high inside and can be closed with a single capstone of snow. The entrance is dug as a tunnel under rather than through the edge of the igloo, to prevent warm air from escaping.

Tents Tents are generally comfortable and dry, but in very cold weather are not as warm as snow shelters. They are preferable to snow shelters at mild temperatures, during damp snow conditions at temperatures above freezing, or when the snow cover is minimal. Because of their weight, they are not usually a component of emergency equipment.

Bivouac Sacks and Other Small, Portable Emergency Shelters These shelters are usually made of thin, waterproof or waterresistant fabric or plastic, do not include an insulating layer, and

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A

Figure 36-9. A, Above-timberline snow trench. B, Completed snow trench the morning after a heavy snowfall.

B

Chapter 36: Essentials of Wilderness Survival

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A

Figure 36-10. A, Snow cave entrance. B, Snow cave partly closed with snow blocks. C, Interior of snow cave.

C

A

B Figure 36-11. A, Preparing a snow dome. B, Completed snow dome.

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A

D

Entrance

B Air vent

E Cooking

Sleeping

Entrance

C Figure 36-12. A–C, Stages of igloo construction. D, Building an igloo, southeast ridge of Mt. Foraker. E, Double igloo for a party of five.

hold one or occasionally two persons. Bivouac sacks are carried for emergencies or for sleeping purposes by climbers on long, alpine-style climbs. Their main value is to protect from wind and rain. Many modern packs have extensions so that when used with a cagoule or anorak (roomy, knee-length, hooded pullover garment), they form an acceptable bivouac sack. Tube tents and plastic bag shelters were discussed in the previous section. Caution: When spending the night in a snow shelter (e.g., trench, cave, igloo), always have a shovel and flashlight inside the shelter within easy reach.


INCREASING BODY

HEAT PRODUCTION

Internal body heat production can be increased voluntarily by raising the level of muscular activity and by eating. To obtain maximal heat production from exercise, the body should be well fed and in peak physical condition. This is particularly important for persons with sedentary jobs who participate in vigorous outdoor sports, and for rescue personnel who may be subject to severe, unplanned, and prolonged physical stress. A

Chapter 36: Essentials of Wilderness Survival suitable physical conditioning program should develop both aerobic and motor fitness. The goal of aerobic exercise is efficient extraction of oxygen from alveolar air. This is best developed by rhythmic endurance exercises such as running, cross-country skiing, cycling, swimming, and using exercise bicycles and Nordic skiing simulators. The most effective activities are those that exercise lower and upper extremities simultaneously. Exercise should be vigorous enough to produce a heart rate of 75% of the age-related maximum (0.75 × [220 minus the participant’s age]) for at least 15 minutes 4 days a week. Motor fitness, which includes strength, power, balance, agility, and flexibility, is developed by vigorous competitive team sports, selected calisthenics, and weight-lifting exercises.


ADDING HEAT FROM THE OUTSIDE

Fire Building The ability to build a fire under adverse conditions is an essential skill that should be practiced by all people who engage in outdoor activities (Fig. 36-13). Not only does a fire provide warmth that may mean the difference between life and death, but it also cheers the spirit, improves morale, serves as a signal to rescuers, and reinforces hopes of rescue and survival. Necessary equipment includes a knife, fire starter, and dry matches. A metal match and a candle should be carried as backup. Matches should be of the “strike anywhere” type stored in a screw-top waterproof container that can be opened with one hand and that has a large, rough striking side or bottom. If this area is too small, a large piece of rough sandpaper should be glued to the bottom or side of the container.14 The fire starter, which can be purchased commercially or homemade of cotton pledgets impregnated with Vaseline (Fig. 36-14), is stored in a secure container such as an extra match container or plastic film can and is highly recommended, especially for wet climates. A small saw makes the task of gathering firewood much easier. This can be collapsible for easier storage in the pack. However, a saw that does not require assembly, such as the Dandy Saw, is easier to make useable when one is cold, tired, or injured. To burn, a fire needs air, but not too much air. The fire site should be out of the wind (behind a rock or log or in a snow pit) on rocks or rocky soil. If the fire is built on bare ground, all flammable material such as moss and grass should be cleaned off by scraping the ground surface down to mineral soil over an area at least 4 feet (1.2 m) in diameter. Remember that every year there are reports of signal fires started by lost people that become uncontrolled and burn thousands of acres of forest. Building a fire requires three types of combustible material: tinder, kindling, and fuel (Fig. 36-15). Tinder is any type of finely divided, highly flammable material, and must be dry. Examples include grass and leaves, inner bark of birch trees, shavings from dry sticks, and small dead sticks. The most readily available natural materials are the small dry twigs found on the lower, dead branches of evergreens. If the outer wood of small branches is wet, it can be shaved off, or the branches can be split lengthwise into several thinner lengths with a knife to expose the dry core. If there is a question about flammability, use fire starter if you have it. The tinder is arranged in lean-to

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form by placing it against a larger branch, smallest sticks on the bottom and larger ones on top, separated just enough so that air can reach each piece. To conserve matches, one match should be used to light a candle or segment of fire starter, which in turn lights the tinder. The initial flame should be placed under the middle of the lean-to of tinder so that lower, smaller pieces will set fire to higher, larger pieces. Kindling is larger material, usually pieces of dead branches and branches that have been split lengthwise with a knife. Once the tinder is burning well, these larger pieces of dry wood are added. Fuel is the largest material, usually huge branches and sections of dead tree trunks several inches or more in diameter. These should be split if an ax is available. Standing dead wood is preferable to wood lying on the ground, and wood that has lost its bark to wood with bark, because both will be drier and less rotten than their alternatives. Fuel is added after the kindling is burning well. Several times more fuel than the predicted need should be collected. When dead branches are gathered, only those that snap loudly when broken off should be selected. Long sections of dead trees can be shortened by laying them across a fire so that when they burn through, two shorter sections result. Fires generally should be kept small, both to conserve wood and allow them to be approached more closely. The dry wood supply should be protected from wind, rain, and snow as much as possible. Although the importance of carrying matches in the survival kit cannot be overemphasized, one should also know several ways of starting a fire without matches. A commercial “metal match” is a good backup device. When scraped repeatedly with any sharp, metal edge, it produces showers of sparks that will ignite very dry tinder or fire starter. On a sunny day, a small magnifying glass can focus the sun’s rays enough to ignite dry tinder. If you are stranded in an automobile, the cigarette lighter and battery can be used. If a length of wire is available, its midportion can be stripped of insulation and wrapped 7 to 10 times around a dry stick. Touching the wire ends to each of the two battery terminals will cause the wire to become red hot, igniting the stick. The wire should be long enough that the flame is not close to the battery, where it could ignite hydrogen gas produced by the battery. Because fire bows and fire ploughs require considerable practice and several types of dry wood, they have little use under survival conditions.

Carbon Monoxide Poisoning Open flames in tents, snow caves, and other confined spaces may be dangerous, especially at high altitude and in winter conditions.12 The first caution is to always keep the possibility of CO poisoning in mind. Provide a shelter with adequate internal space, ventilated as well as possible. Caves and igloos should have ventilation ports at least as big as a ski pole basket, located as high as possible. Avoid prolonged simmering, keep stoves highly pressurized, and use a maximally blue flame. If the flame becomes yellow, turn the stove off and repressurize. For warmth, rely on clothing and bedding as much as possible, rather than keeping a stove going. When cooking, make regular trips outside for fresh air so that early signs and symptoms will be easier to notice. Be aware of the early symptoms of CO poisoning, which include headache, tachycardia, and alteration in mental status.

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PART FIVE: RESCUE AND SURVIVAL

A

B

C

D

Figure 36-13. Stages of building a fire. A, Select a spot out of the wind. Start by placing tinder, such as small, dry evergreen twigs, in a lean-to fashion against a larger branch. B, Add a layer of kindling (larger dry branches and split sticks) over the tinder, being sure that air can reach each piece. C, Insert a lighted match, candle, or cigarette lighter into the base of the lean-to. D and E, Add larger pieces of kindling and fuel (large sticks and pieces of split wood) as the fire catches well. Keep the fire small so that you can get close to it.

E


FOOD Although most persons faced with a survival emergency worry more about food than anything else, food is usually less important than shelter or water because a person can survive for weeks without food, even in cold weather. Enough water must

be available, however, and energy expenditure must be kept to a minimum. Most wilderness parties carry adequate supplies of food; problems arise if food is exhausted, lost, or contaminated. Bare ridges, high mountains above timberline, and dense evergreen forests are difficult places to find wild food, especially in winter. Success is more likely on river and stream banks, on lake shores, in the margins of forests, and in natural clearings.

Chapter 36: Essentials of Wilderness Survival

Figure 36-14. Use of Vaseline-impregnated cotton as a fire-starter. (Photo courtesy of Peter Kummerfeldt.)

Figure 36-15. The three sizes of combustible material, from left to right: fuel, kindling, and tinder. Metal match with striker shown at bottom left. (Photo courtesy of Peter Kummerfeldt.)

Because in most cases the amount of wild food found by an untrained individual will not provide enough calories to replenish the energy expended in searching for it, it is important to always carry extra food for emergencies. This is true even on a short afternoon hike. Readers interested in the details of obtaining wild food should consult Chapter 65, Living Off the Land.


WATER Water constitutes about 60% of the body weight of an average young adult male; the value for a female is slightly lower. The percentage of water tends to decrease with age. In a sedentary adult, normal daily water loss includes about 1400 mL of urine, 800 mL through the skin and lungs, and 100 mL in the stool, for a total of 2300 mL daily. Because about 800 mL of water per day is contained in food and 300 mL produced by metabolism, a minimum daily intake of 1200 mL is necessary in a tem-

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perate climate at sea level to avoid dehydration.7 In a hot dry climate, at high altitude, or with exertion, insensible losses and sweating increase considerably, so fluid intake should be increased proportionally. Monitoring urine output determines whether intake is adequate; 1 to 1.5 L of light-colored urine should be excreted per day. Adding fruit flavors and making hot drinks improve the palatability of water. Electrolyte drinks and salt tablets are generally unnecessary in cold or temperate weather because the electrolytes lost in sweat are easily replaced by a normal diet. When water supplies are limited, overexertion is avoided and sweat “rationed.” Almost all surface water should be considered contaminated by animal or human wastes, with the possible exception of small streams descending from untracked snowfields or springs in high, uninhabited areas. At altitudes below 5488 m (18,000 feet), simply bringing water to a boil will kill Giardia cysts and most harmful bacteria and viruses. Water can also be disinfected by filtration or addition of chemicals. (See Chapter 61 for details.) At subfreezing temperatures and in locations above the snow line where liquid water is difficult to find, snow or ice must be melted to obtain water. This requires a metal pot (which should be included in every survival kit), fire-starting equipment, and wood for fuel. The time and effort required to obtain water and decreased thirst in cold weather favor the development of dehydration in cold weather travelers. In the winter, whenever open water is encountered, individuals should drink their fill of disinfected water, then top off all canteens. Each evening, enough snow is melted to provide water for supper plus a full canteen, which is placed in the bottom of the sleeping bag to keep it from freezing, and is ready for use during the night or for making breakfast in the morning. Before leaving camp in the morning, enough snow is melted to provide everyone with at least a full canteen for the day. Melting ice or hard snow is more efficient than melting light, powdery snow. To avoid scorching the pot, the snow is melted slowly, or water is heated in the bottom of the pot before adding snow. On warmer, sunny days, snow can be spread on a dark plastic sheet to melt.


EMERGENCY SNOW TRAVEL Travel in deep snow is almost impossible without skis or snowshoes. Snowmobilers, pilots, and other mechanized oversnow travelers should carry snowshoes for emergencies. Even though travel may be unwise for other reasons, wilderness foot travelers in both subarctic and temperate latitudes should know how to improvise snowshoes from natural materials in the event they are stranded by a late- or early-season snowstorm. Emergency snowshoes (Fig. 36-16A) can be made from poles that are 6 feet long, 3/4 to 1 inch (1.9 to 2.5 cm) thick at the base, and 1 /4 inch thick at the tip, and sticks 3/4 inch thick and 10 inches long.1 Twelve long poles and 12 short sticks are needed. For each snowshoe, six long poles are placed side by side on the ground, and the middle point of the poles is marked. One short stick is lashed crosswise to the tail (base) of the poles, and three short sticks are lashed side by side just forward of the midpoint of the poles where the toe of the boot will rest. Two sticks are lashed where the heel of the boot will strike the snowshoe. The tips of the six poles are tied together. Each binding (see Fig. 36-16B) is made of a continuous length (about 6 feet

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A

B Figure 36-16. A, Emergency snowshoe. B, Detail of snowshoe binding.

[1.8 m]) of nylon cord (preferably braided because it will eventually fray). The midpoint of the cord is positioned at the back of the boot above the bulge of the heel. Each end of the cord is run under the three side-by-side short sticks at the side of the boot, then up and across the boot toe so that it crosses the other end on top of the toe, forming an X. Then, each end is looped around the cord running along the opposite side of the boot, and the ends are brought around the back of the boot heel. The cord is pulled tight around the boot, and the ends are tied together at the lateral side of the heel. On walking, the tip of the snowshoe should rise, the boot heel should rise, and the boot sole should remain on the snowshoe. Snow travelers should avoid stepping close to trees (because of funnel-shaped tree wells around tree trunks), large rocks (because of weak snow or moats around them), and overhanging stream banks. In snow country, the person who falls into a stream or lake should roll repeatedly in powdery snow to wick water from clothing, brushing off the snow after each roll. A fire completes the drying process.1


SURVIVAL IN SPECIAL

INSTANCES, INCLUDING NATURAL CATASTROPHES

The general principles of survival in all catastrophes are the same, particularly the need for forethought, planning, and keeping emergency equipment, water, and food on hand.1,18,21 Nevertheless, different types of catastrophes require different approaches, particularly at first. Some common types are discussed next.

Stalled or Wrecked Automobiles Anyone who drives faces the possibility of spending an unplanned night out in a vehicle.20 Causes include bad weather, breakdown, running out of fuel, and getting stuck. Winter

driving is especially hazardous because of the dangers of driving on snow or ice and the threats of frostbite and hypothermia. Accepting the possibility of trouble, carrying a vehicle survival kit, and giving some thought to survival strategies will help prevent a night out in a car from deteriorating into a lifethreatening experience. Most travelers dress to arrive at a destination and not to survive a night out—“to arrive, not to survive.” A vehicle survival kit (see Appendix C) should include extra clothing, blankets or sleeping bags, food, water, signaling equipment, and communications equipment (e.g., citizen’s band radio, cell phone). It is also generally better to stay with the vehicle, which provides significant protection and is more visible to rescuers than is a person on foot. In cold weather, and especially for long-distance travel, drivers should keep their vehicles in the best possible mechanical condition, using winter-grade oil, the proper amount of radiator antifreeze, deicer fluid for the fuel tank, and antifreeze in the windshield-cleaning fluid. Windshield wiper blades that are becoming worn should be replaced. A combination snow brush and ice scraper should be carried. A can of deicer is useful for frozen door locks and wiper blades. Snow tires, preferably studded (illegal in some states), are desirable, but chains should be carried as well. All-wheel drive or four-wheel drive is optimal, and front-wheel drive is superior to rear-wheel drive. The battery should be kept charged, the exhaust system free of leaks, and the gas tank full (“drive on the upper half of your tank!”). The marooned driver should tie a brightly colored piece of cloth (such as a length of surveyor’s tape) to the antenna and at night should leave the inside dome light on to be seen by snowplow drivers and rescuers (headlights use too much current). If necessary for heat, the standard recommendation is that the motor and heater can be run for 2 minutes each hour (after checking to see if the exhaust pipe is free of snow). However, a recent newspaper column15 notes that because it takes more gasoline to start a cold engine than a warm one, one should initially turn the heat up all the way and run the engine

Chapter 36: Essentials of Wilderness Survival until the inside is comfortable. Then, shut off the engine and wait until it becomes uncomfortably cold (which could be 10 to 30 minutes depending on outside temperature). The engine, however, will still be “warm.” Start the engine again and run the heater until the occupants feel warm. Keep repeating this. CO poisoning is a real threat, so do not go to sleep with the engine running, and keep a downwind window cracked 1 to 2 inches. A reusable CO detector is a wise addition to the survival kit. One or two large candles (“fat Christmas candle” size) should be carried to provide heat and light if the gasoline supply runs out; two lit candles can raise the interior temperature well above freezing. However, resources should be used sparingly because you are never sure how long you will be marooned. Foresight enough to include heavy clothing and blankets or sleeping bags in the cold-weather vehicle survival kit is better than relying excessively on external heat generation. Do not smoke or drink alcohol. If you have to get out of the vehicle, put on additional windproof clothing and snow goggles, and tie a lifeline to yourself and the door handle before moving away from the vehicle. In a blizzard, visibility can be as low as 12 inches.

Aircraft Accidents Passengers on aircraft are routinely lectured on locations of exits and procedures for emergencies. The safest place to sit is as far back in the tail as possible.21 In a crash, this frequently breaks off, and most survivors of crashes were sitting in this area. When a crash is imminent, tighten the seat belt, link arms with people on either side, bend your head so that your chin is firmly on your chest, and lean forward over a folded coat or blanket. After the aircraft finally stops moving, leave it as instructed. Assist injured companions to leave, then get everyone away from the immediate area to avoid the hazard of fire. Do not stop to gather personal belongings or luggage. After the fire risk is over, revisit the wreckage to salvage food, clothing, water, and other useful items. Remember that aircraft fuselages are poorly insulated. Unless a stove is available, survivors are usually better off constructing a shelter that can be heated with a fire (as described earlier), outside but near the craft. Batteries can be used as fire starters. Oil and gasoline can be used as fuel if poured into a container full of dirt or sand. Unless there is no chance that a search will be mounted to find the aircraft, you should remain close to it rather than trying to go for help. It is much easier for searchers to spot a crash site than survivors on foot in the wilderness.

Floods Flooding in wilderness areas may be caused by thunderstorms, unusual storms such as hurricanes, and rapid melting of ice and snow during heat waves. Flash floods in canyons can occur both during and after rains and can be caused by rains many miles upstream. Submarine earthquakes can cause huge tidal waves (tsunamis) that may drown hundreds of thousands of shore dwellers. Whenever traveling or camping near bodies of water in the wilderness, one should keep in mind what might happen if overflow or rising water should occur. When traveling or camping in box canyons, below dams, close to banks of water channels, and on low ground such as valley bottoms, one should have a well-thought-out exit strategy in case flooding occurs. If along the shore and you receive a radio report of an impending tsunami, or if you see the sea recede and expose a large expanse

815

of sea bed, flee immediately and seek high ground as far from the shore as possible. Persons caught in moving water have no recourse other than trying to swim to the side or hang on to floating debris, trying to hang onto emergency supplies in the process. Never try to cross an area of moving water unless you are sure it is no more than knee-deep.

Thunderstorms Dangers from thunderstorms include flooding (discussed earlier), lightning strike (see Chapter 3), and exposure, including wetting and hypothermia. Severe thunderstorms may produce hailstones of various sizes, including stones large enough to harm a struck individual. During a thunderstorm, it is wise to seek shelter. This requires getting into raingear and avoiding heavy rain and hailstones by getting into a metal vehicle or dense grove of trees. If you are on water, head for shore as soon as threatening weather approaches. If in an area where you are the highest object around, leave immediately or crouch down on your haunches. Avoid small buildings, electric wires, metal objects, rocky overhangs where you may be hit by side flashes from ground currents, solitary trees, and trees taller than surrounding trees.

Tornados These funnel-shaped clouds typically form on a hot spring or summer afternoon in the midwestern United States. They are usually preceded by large cumulonimbus clouds, from the bottoms of which a careful observer occasionally can see the formation of the tornado as a dimple that elongates into a typical conical funnel cloud. Persons who witness this phenomenon should leave immediately by vehicle in a direction opposite to the tornado’s likely path, or seek shelter on the spot. In houses, the best shelters are small, interior rooms with non–weight-bearing walls, preferably in the basement but on the ground floor if no basement exists. Ditches and small buildings are not safe. Caves and outdoor root cellars are fairly safe, but vehicles are not.

Hurricanes These severe tropical storms are extreme cases of the vortices of wind and rain that frequently form over tropical seas. By definition, they contain winds of 119 kph (74 mph) or stronger. They require ocean temperatures of 25.5° C (78° F) and a spawning area at least 10 degrees latitude from the equator so that the earth’s rotation is strong enough to start them in motion. Deaths due to hurricanes are usually due to high winds, flooding from heavy rain, or coastal flooding due to storm surges. With modern technology, the formation of a tropical cyclone (tropical low) and its change into a tropical storm and then a hurricane is predictable and reported in detail by the National Oceanic and Atmospheric Administration. Persons at risk should keep the radio or television on so they will be aware when there is a need for evacuation. Most casualties are persons who remained against advice or were caught by winds and flooding before they could get far enough inland. Persons who live in hurricane-prone areas should have emergency caches of water and nonperishable food, clothing, bedding, a first-aid kit with supplies of any regular medications, emergency lights (candles, matches, flashlights, spare batteries), cell phone, and battery-operated radio, should keep the car’s gas tank full, and

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should be ready to head inland with these supplies as soon as advised to do so. Before they leave, they should board or shutter all windows, take inside any yard objects that might be blown away, and shut off the gas and electric power.

Earthquakes Earthquakes can be anticipated on geologic grounds but their time of occurrence cannot be predicted with much accuracy. They are most common along known fault lines, allowing decisions about the strength of building construction to be based on risk to some extent. If you are warned of a possible earthquake because of early tremors, keep your radio on and be sure you have supplies as listed earlier under “Hurricanes.” Turn off electricity, water, and gas if advised to do so. Remove heavy and fragile objects from high shelves, ceilings, and other places from where they might fall. If an earthquake strikes while you are at home, stay away from mirrors and windows and seek shelter in a corner or under a table, preferably in a basement.

Volcanoes Almost all volcanoes near inhabited areas are monitored by seismograph (see also Chapter 15). Because increasing steam releases, small eruptions, increases in seismographic activity such as small to major tremors, and other signs of impending volcanic activity frequently precede major eruptions, residents, workers, tourists, hikers, and campers usually have time to evacuate. Danger to humans comes from earthquakes, explosions, lava flows, mud flows, ash, and flooding. Because many fatalities in eruptions such as that of Mt. St. Helens were in persons who were warned of the danger but refused to evacuate, the obvious advice is to leave the area quickly when advised. The forces released during an eruption are too great to permit survival of unprotected humans.


NAVIGATION Even if in a familiar area, backcountry travelers should always carry a compass, map, and altimeter. Prior training and experience in map reading and compass use are necessary.11 An excellent type of compass for the layperson is the Swedish Silva compass, designed to be used in the sport of orienteering. The compass reading is always believed, even if at odds with “gut feelings” about direction and location. Topographic maps are available at most outdoor stores in both the 7.5- and 15-minute series and can be ordered from the U.S. Geographic Survey (1-888-ASK-USGS or on the Internet at www.USGS.gov). Travelers without a compass should still be able to find rough directions. At night, north can be found by identifying the Big Dipper (Northern Hemisphere only) and following the “pointers” (farthest stars on the bowl of the dipper) to the North Star (Polaris), the most distal star in the handle of the Little Dipper, which is located about halfway between the Big Dipper and the W-shaped constellation Cassiopeia. On a sunny day, a non-digital watch set to standard time can be used to find direction. When the hour hand is pointed toward the sun, south will be one-half of the shorter of the two distances between the hour hand and 12 o’clock. The availability of small, hand-held GPS units has revolutionized wilderness navigation but not replaced the need for good map and compass skills. Detailed information on wilderness navigation is found in Chapter 85.


WEATHER FORECASTING Travelers should check expected weather conditions before entering the backcountry.4,9,13,22 With radar, satellite technology, and other advanced techniques, modern weather forecasting is accurate but not infallible. Local and national radio and television networks broadcast local and regional reports hourly. The Weather Channel (on television) has frequent forecasts and is also available on the Internet at www.weather.com. The best source of up-to-date local weather information is the National Weather Service, which broadcasts 24 hours a day at frequencies from 162.400 to 162.550 MHz on very-high-frequency (VHF) FM. Multichannel radios with a weather band receive these frequencies, and inexpensive, lightweight radios receive only these frequencies. When evaluating avalanche conditions, travelers must know the weather conditions over the previous few days as well. The U.S. Forest Service provides information on avalanche conditions in many mountainous areas, especially in western states, available online at www.avalanche.org. (See Appendix in Chapter 2.) Because weather information from outside sources may be impossible to access in a true wilderness environment, the wilderness traveler should be able to predict weather to some extent. This requires knowledge of both basic meteorology and local weather patterns, particularly the significance of cloud patterns, wind directions, barometric pressure changes, and temperature changes. Backcountry weather forecasting is an inexact science, however. In Michael Hodgson’s words, “Predictions relative to weather are only educated guesses, never statements of fact. Always be prepared for the worst.”9 The major factors that influence weather are solar radiation, the components of the atmosphere (especially water vapor), topography, physical properties of large water bodies and land masses, and the effects of the earth’s daily and yearly rotations on the amount of solar radiation that reaches each part of the earth. The earth’s atmosphere is constantly in motion. The primary motion is basically circular, involving vertical upward motion as air is heated at the equator, then horizontal motion of this warm air toward the poles, where it cools, descends, and moves back toward the equator to replace heated, upward-moving air. If the earth did not rotate, this circular motion would be in a north-to-south direction. The earth’s rotation, however, causes the direction of movement to be deflected to the right (in the Northern Hemisphere), so the movement becomes more west to east (Coriolis effect) in the northern temperate zone (area between the Tropic of Cancer and the Arctic Circle). Because the earth’s surface is covered unevenly by land masses, water bodies, and polar ice, and because these regions are heated irregularly as the earth rotates on its axis, systems of moving cold and warm air masses are formed. Cold, moist air masses tend to form over cold (polar) seas and warm, moist air masses over warm seas. Cold, dry air masses tend to form over cold (polar) land and warm, dry air masses over warm land. The polar regions have large, stable areas of cold, high-pressure air (polar highs), and the equatorial regions (between 10 degrees south and north of the equator) have a large area of stable, warm, moist, and low-pressure air (doldrums). Atmospheric pressure in air masses depends on their temperature: higher in cold air masses and lower in warm air masses.

Chapter 36: Essentials of Wilderness Survival Winds are caused by air moving from a high-pressure to a lowpressure area; the greater the pressure difference, the higher the wind speed. Each air mass, which may cover hundreds to thousands of square miles of the earth’s surface, is nearly homogenous for temperature and humidity. In the northern temperate zone, air masses generally move from west to east in North America. Exceptions include cold, relatively dry air masses that move south from northern Canada in the winter and warm, moist air masses (“monsoons”) that move north from the Gulf of Mexico in the summer. Cold air masses move faster than warm air masses (25 to 35 mph versus 10 to 20 mph). The boundaries between air masses are called fronts. Frontal air is generally unstable and frequently an area of violent weather. A cold front is an area where heavy, cold air is displacing lighter, warm air, frequently by coursing under it. A warm front is an area where lighter, warm air is replacing a retreating mass of heavier, cold air. Warm, low-pressure air masses are called lows, or cyclones; cold, high-pressure ones are called highs or anticyclones. Because air flows from areas of high pressure to areas of low pressure, lows are characterized by winds blowing from their edges toward their centers and highs by winds blowing from their centers toward their edges. The Coriolis effect causes winds in the Northern Hemisphere to move in a clockwise direction from the center to the periphery in a high and in a counterclockwise direction from the periphery to the center in a low. Understanding these principles can help the traveler interpret shifting wind directions as highs and lows pass. Weather within an air mass is controlled by its moisture content, the relationship between land surface and air mass temperatures, and terrain features such as up- or down-slopes. Precipitation can occur in either a high or a low, but is more common in a low. The amount of moisture in an air mass can be described as the air’s relative humidity, which is the amount of water vapor in the air compared with the amount it could hold at its current temperature without condensation occurring. Warm air can hold more water vapor than cold air. The term dew point refers to the temperature at which the relative humidity becomes 100% and the water vapor in air starts to condense. Because the temperature drops about 2.2° C (4° F) for every 305 m (1000 feet) of ascent (1.6° C [3° F] if the air is moist; 3° C [5.5° F] if dry), rising air cools, and descending air warms. Water vapor in rising air will condense when the air cools to its dew point, producing fogs, clouds, and precipitation. The wilderness traveler should be able to identify the different types of common clouds and know their significance. Clouds are divided into four types based on level, form, and association with precipitation (Figs. 36-17 and 36-18). The highest are cirrus clouds, which develop above 6000 m (20,000 feet). These ice-crystal clouds frequently appear thin, veil-like, and delicate. The feathery ones are called “mare’s tails.” The sun shines brightly through cirrus clouds. Middle-level clouds (2000 to 6000 m [6500 to 20,000 feet]) have the prefix alto- (e.g., altocumulus). Low-level clouds (2000 m or below) have the prefix strato- or suffix -stratus (e.g., stratocumulus, nimbostratus.) These terms are also used to indicate clouds in sheets or layers at higher altitudes (e.g., altostratus, cirrostratus). Clouds of high vertical development (500 to 18,200 m [1600 to 60,000 feet]) are the larger types of cumulus clouds frequently associated with heavy precipitation. Developing ones that ascend to 9100 m (30,000 feet) and have billowing tops

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Cirrus Cirrostratus Cirrocumulus Altostratus Altocumulus

Cumulonimbus

Stratocumulus Nimbostratus

Cumulus

Fog

Figure 36-17. Different types of clouds. (Modified from Woodmencey J: Reading Weather: Where Will You Be When the Storm Hits? Helena, MT, Falcon, 1998.)

resembling cauliflowers are called cumulus congestus. The largest ones rise to 18,200 m (60,000 feet) or above, have anvilshaped tops, and are called cumulonimbus. Both types have darkened bases. Because of these clouds’ height, precipitation falls long distances through areas of super-cooled water droplets. Depending on conditions, soft hail (graupel) or huge snowflakes may result. The prefix nimbo- or suffix -nimbus indicates that a cloud is associated with precipitation. The term cumulus refers to any clouds that present as large or small groups of separate fluffy masses (e.g., cirrocumulus, altocumulus, cumulus fractus, depending on their altitude). Cumulus humilis refers to the middle-level, white, cottony clouds with white bases seen in fair weather. In the inland parts of North America, the worst winter weather (blizzards) is associated with moving masses of warm air (lows) and the worst summer weather (severe thunderstorms) with either rising masses of warm air or moving masses of cold air. There are two types of thunderstorms, both associated with cumulonimbus clouds (thunderheads). Frontal thunderstorms result when an arriving cold front slides under a warm air mass. Air mass thunderstorms consist of two subtypes: orographic thunderstorms, which result when moist air is forced up over a mountain range causing thunderstorms on the windward side, and convective thunderstorms, which result from rising vertical currents of air caused by heating of ground or water by solar

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A

B

C

D

Figure 36-18. A and B, Cirrus. C, Altocumulus lenticularis. D and E, Altostratus.

radiation. These latter are the typical afternoon or early-evening thunderstorms, which may spawn tornadoes when severe. An advancing warm front bringing precipitation has a predictable series of lowering, darkening cloud formations: scattered cirrus, sheets of cirrostratus, sheets of altostratus, then nimbostratus. Precipitation can begin with the appearance of either altostratus or nimbostratus clouds. The combination of cirrus followed by cirrostratus and altostratus clouds usually predicts precipitation within 24 to 48 hours. Cumulus congestus and especially cumulonimbus clouds indicate thunderstorms. The wilderness traveler can anticipate weather to a limited extent by using a thermometer and barometer (or altimeter), noting wind direction, and identifying clouds. Remember,

however, that even with the best modern forecasting equipment, the National Weather Service itself is not accurate 100% of the time, especially in forecasting conditions in a small area of wilderness. Nevertheless, we can say that if the signs that predict a severe storm are present, the storm is not guaranteed, but if the signs are absent, a severe storm is unlikely. Some digital watches have altimeter and barometer features. The senior author prefers to carry an aneroid altimeter (which does not require batteries) and that serves as both altimeter and barometer. Both instruments measure air pressure, but are geared oppositely, so that the altimeter registers higher as altitude increases (pressure drops), whereas the barometer registers higher as pressure rises. During mountain travel, barometer and altimeter readings change as altitude changes, regardless of the

Chapter 36: Essentials of Wilderness Survival

E

F

G

H

I

J

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Figure 36-18, cont’d. F, Altocumulus. G, Nimbostratus. H, Cumulus humilis. I, Cumulus congestus. J, Cumulonimbus.

presence of low- or high-pressure areas. In the evening, however, the moveable arrow on the rotating face of the aneroid altimeter can be set at the present altitude or the altitude (or barometric pressure readout) recorded. The next morning, the evening reading is compared with the morning reading. Most severe winter storms in the temperate zone are accompanied by

an altimeter rise of 150 to 240 m (500–800 feet), equivalent to a barometer drop of 0.5 to 0.8 inch of mercury (in Hg) or 15 to 24 mb. A rapid altimeter rise (barometer drop) may signify high winds or a short, severe storm, and a slow, steady altimeter rise (barometer drop) a long storm. A rapid altimeter drop (barometer rise) may also mean high winds (Table 36-3).

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TABLE 36-3. Barometer and Altimeter Forecaster BAROMETER CHANGE

ALTIMETER CHANGE

.04–.07 in Hg (1–2 mb) .08+ in Hg (2.5+ mb) .20–.40 in Hg (6–12 mb) .40+ in Hg (12+ mb)

40–70 ft (12–20 m) 80+ ft (24+ m) 200–400 ft (60–120 m) 400+ ft (120+ m)

TIME (hr)

WEATHER CHANGE EXPECTED

3

Some changes should be expected. May be slow to develop.

3

Significant changes should be expected. May be developing rapidly.

12–24

Some changes should be expected. May be slow to develop.

12–24

Significant changes should be expected. May be developing rapidly.

Hg, mercury; mb, millibar. From Woodmencey J: Reading Weather: Where Will You Be When the Storm Hits? Helena, MT: Falcon, 1998, Table 15, p 113.

Because of their different meteorologic features (as described previously), the marked altimeter rise (barometer drop) seen in a severe winter storm typically does not occur in a severe summer thunderstorm. Because cloud patterns are always changing, they must be observed at regular intervals throughout the day, to develop the ability to predict their significance with any confidence. Measuring and recording the air temperature several times daily (remembering that temperature normally drops with increasing altitude) and noting wind directions can confirm an advancing low or high when coordinated with other observations. If a low is moving directly toward you, the wind will shift so that it is blowing from the southeast or south (Northern Hemisphere). If the wind comes from the southwest or west, the low is passing north of you; if from the northeast or east, it is passing south of you. An easy way to check this is to stand with your back to the wind. The low-pressure area will be in front of you and to your left.4 As a front passes, the wind will gradually shift 180 degrees. The shores of large bodies of water have characteristic wind patterns because of the difference in specific heats of water and land leading to different warming and cooling rates. In the morning, because land warms and cools faster than water, breezes begin to blow from water to shore as the air over land rises. As the land cools in the evening, breezes begin to blow from land to water.

Mountain Weather Mountain weather is more unpredictable than weather in lower, flatter country. Winds frequently blow up and down mountain valleys regardless of their orientation because of the funnel effect of the valley and temperature differentials caused by solar radiation. The funnel effect may also cause heavy snowfalls at passes or the higher ends of valleys. On a sunny day, the sun warms mountaintops and high slopes first, the warm air rises, and winds blow up the slope. In the evening, the tops and high slopes cool first, the cool air descends, and winds blow down the slope. Glaciers and large snowfields produce significant cool, down-slope winds. Except on the clearest days, mountaintops may have clouds over them or nearby because of the up-slope winds that carry moist air high enough to reach its dew point. In the summer, mountains

warm up during the morning and early afternoon, creating cumulus congestus and cumulonimbus clouds that produce thunderstorms, lightning, and hail. Therefore, the standard caution for summer climbers is to arise early and reach the summit well before noon. Lightning usually precedes rain in a thunderstorm and can strike up to 5 miles (8 km) away from the storm. Distance is estimated by counting the seconds between the lightning flash and the first noise of thunder: 5 seconds equals 1 mile (count: “one-and-two-and, etc.,” at a speaking pace slightly faster than normal). Precipitation is frequently heavy on the windward side of large mountain ranges; the leeward sides are usually much drier and in low areas may actually be desert. Stationary lens-shaped clouds (altocumulus lenticularis) are frequently seen near mountaintops in windy weather and signify high winds at the summits. High winds also produce long snow plumes from summits and ridges. The summit wind speed will be about twice the valley wind speed.22 Winds blowing at right angles to a mountain range tend to concentrate at any gaps or passes in the range, creating high winds due to the Venturi effect. Warm down-slope winds in the winter (Chinook or foehn winds) are produced when cool, dense air blowing over mountaintops loses its moisture as precipitation on the windward side; the drier air then warms rapidly as it descends on the lee side. These warm winds can melt snow rapidly. Weather is more stable at some times of the year than at others, but the times vary by geographic area. For example, in the northern Rocky Mountains, the best time to hike or climb in the summer are the last week of July, all of August, and the first two weeks in September. The best time to ski-tour or climb in the winter is February. In Alaska, the best winter climbing weather is during February and in spring and summer from April through June. In the Himalaya and Karakorum, the best climbing weather is immediately before and after the summer monsoon (a seasonal, northward flow of warm, moist air from the Indian Ocean). The principal value of understanding weather signs is in predicting severe, life-threatening storms and providing adequate time to seek shelter or the option to stay put rather than try for a summit. Travel in severe weather, especially above timberline, should never be undertaken casually.

Chapter 36: Essentials of Wilderness Survival

Summary of Backcountry Weather Forecasting 1. Blue sky, a few cirrus or cumulus humilis clouds, cool temperatures, low to medium winds, and a steady or dropping altimeter (steady or rising barometer) are predictors of good weather. 2. A lowering cloud pattern (cirrus followed by cirrostratus, altostratus, and nimbostratus), rising temperatures, wind freshening and shifting to blow from the southeast or south, and an altimeter rise of 152 to 244 m (500–800 feet) or barometer drop of 0.5 to 0.8 in Hg (15–24 mb) indicate a possibly severe winter storm. 3. Building cumulus congestus clouds changing to cumulonimbus clouds indicate probable thunderstorms with lightning and possibly hail. A thunderstorm is frequently preceded by a rush of cold air (cold front). 4. Signs that a severe winter storm is abating include clouds thinning, cloud bases rising, temperature falling, altimeter dropping (barometer rising), and the winds shifting to blow from the north or northwest.


SANITATION Adherence to proper habits of cleanliness and sanitation is as important in the wilderness as at home.2 Hands should be washed with biodegradable soap after urinating or defecating, before cooking and eating, and before dressing open wounds. If soap is unavailable, snow or the cleanest available plain water is used. Dishes and pots are washed with hot water and biodegradable soap and rinsed well to remove all soap. Waste water is scattered over a wide area of ground and never dumped into a body of water. Bathing and washing clothes should be done at least 60 m (200 feet) from bodies of water, using water in a container. Gloves, preferably rubber or vinyl (impermeable) ones, are worn when handling moist animal or human tissues (be aware of possible latex allergy). For defecation, campers should dig a “cat-hole” at least 18 inches (46 cm) deep, 6 inches (15 cm) wide, downhill, and at least 60 m (66 yds) from camp, water sources, or snow to be melted for water. Cover feces completely with dirt or snow. No camp should be within 60 m (66 yds) of a lake or stream, which represents 70 to 80 steps for most adults. Travelers should urinate on rocks or dirt, not on green plants. When sleeping in a tent or snow shelter, a 500-mL, wide-mouth polyethylene bottle can be used as a urinal to avoid having to go outside, especially at night. Funnels designed for use with the bottle are available for women.


PSYCHOLOGICAL AND

ORGANIZATIONAL ASPECTS OF SURVIVAL

Dealing with the psychological aspects of survival is as important as confronting physical and environmental factors. As mentioned previously, the dangerous mindset that keeps a person continuing on a hazardous course, such as completing a climb or reaching a distant campsite despite conditions that would make a more prudent person bivouac or turn back, is a recurring scenario.6 In a survival emergency, a person with survival training, adequate oxygen, a stable body temperature, shelter, water, and food may still die if unable to withstand the psy-

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chological stress. Conversely, persons have survived amazing hardships with little more than a strong determination to live. Individual reactions, however, cannot be predicted in advance. Groups faced with emergencies testify that courage and leadership appear in unexpected places. Still, if persons possess the necessary skills, have at least a minimum of survival equipment (see appendices to this chapter), and have given some forethought to techniques of wilderness survival, the odds are strongly in their favor. Medical personnel have the advantage of being trained to suppress panic. Fear and surrender are normal reactions that must be opposed by whatever psychological tools are available. In some cases, religious faith or the desire to rejoin loved ones have been credited with survival. Anxieties that paralyze action include fear (of the unknown, being alone, wild animals, darkness, weakness, personal failure, discomfort, suffering, and death) and panic. Panic, the uncontrolled urge to run away, interferes with good judgment, resulting in inappropriate actions such as abandoning weaker companions, dividing the party, and discarding vital survival equipment. Useless flight saps available energy, leads to exhaustion, and hastens death. Other psychological reactions include apathy and the normal desires to be comfortable and to avoid pain.18 Apathy is giving up, a state of indifference, mental numbness, surrender, and unwillingness to perform necessary tasks. The victim shows resignation, quietness, lack of communication, loss of appetite, fatigue, drowsiness, and withdrawal. Apathy in one’s self is overcome by faith in abilities and equipment and belief in survival and the possibility of rescue. Apathy in others is combated by communicating plans and positive feelings about resources and outcomes to them, and including all group members in planning and survival activities. Comfort is not essential to survival. Marked discomfort (from injuries, illnesses, thirst, hunger, excessive heat or cold, sleep deprivation and exhaustion) is inevitable in a survival situation and must be tolerated in order to live. As illustrated by the scenario described at the start of this chapter, there are many accounts of adventurers who have survived many days with severe injuries such as open fractures because of the will to live, or who, despite multiple injuries, have dragged themselves for miles to find help. Providing an ill or injured party member with psychological support is important. This includes appearing calm, unhurried, and deliberate yourself while trying to encourage optimism, patience, and cooperation. A person with a minor injury or illness should be encouraged to self-evacuate, accompanied by at least one healthy party member. When a person with a severe injury or illness needs to be evacuated, the party must decide whether to use the resources at hand or to send for help. The decision will depend on the weather, party size, training, available equipment, distance, type of terrain involved, type of injury or illness, victim’s condition, and availability of local search and rescue groups, helicopters, and other assistance. Unless the weather is excellent, party strong and well equipped, route short and easy, and victim comfortable and stable, the best course of action generally is to make a comfortable camp and send the strongest party members for help. A written note should include each victim’s name, gender, age, type of injury or illness, current condition, and emergency care given; the party’s resources and location (preferably map or GPS coordinates); and names, addresses, and telephone numbers of relatives. The victim who

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must be left alone (e.g., because of small party size) should have an adequate supply of food, fuel, and water. As soon as you realize that you are lost, stop, sit down in a sheltered place, calmly go over the situation, and make an inventory of your survival equipment and other resources. If it is cold or becoming dark, start a fire and eat if you have food. Take out your map or draw a sketch of your route and location based on natural features. Then, unless you know your location and can positively reach safety before dark, immediately start to prepare a shelter for the night. Do not allow yourself to be influenced by a desire to keep others from worrying or the need to be at work or keep an appointment. Your life is more important than someone else’s peace of mind.8 If you are alone and unquestionably lost, and especially if injured, you must decide whether to wait for rescue or attempt to walk out under your own power. If rescue is possible, it is almost always better to use the time to prepare a snug shelter (before dark) and conserve your strength. If you decide to leave, mark the site with a cairn or bright-colored material such as surveyor’s tape, leave a note at the site with information about your condition, equipment, and direction of travel, and then mark your trail. These actions will aid rescuers and enable you to return to the site if necessary. Travel should never be attempted in severe weather, desert daytime heat, or deep snow without snowshoes or skis. If no chance of rescue exists, prepare as best possible, wait for good weather, and then travel in the most logical direction. The best way for a lost or stranded person to aid potential rescuers is to do everything possible to draw attention to his or her location. Most modern rescues utilize ground parties, helicopters, and fixed-wing aircraft. When the latter locate victims from the air, they can drop supplies and vector helicopters or ground parties to the site. Besides radios, cell phones, and other electronic equipment, signaling devices are either auditory or visual. Three of anything is a universal distress signal: three whistle blasts, three gunshots, three fires. The most effective auditory device is a whistle. Blowing a whistle is less tiring than shouting, and the distinctive sound can be heard farther than a human voice. An effective visual ground-to-air signal device is a glass signal mirror with a sighting device, which can be seen up to 10 miles away but requires sunlight. Special rescue beacons are available and can be carried as emergency equipment. These include strobe lights, laser signal lights, special beacons with both signaling and GPS capability, and PLBs. Smoke is easily seen by day and a fire or flashlight by night. On a cloudy day, black smoke is more visible than white; the reverse is true on a sunny day. White smoke stands out well against a green forest background but not against snow. Black smoke can be produced by burning parts of a vehicle, such as rubber or oil, and white smoke by adding green vegetation to a fire. The lost person who anticipates an air search should keep a fire going with large supplies of dry, burnable material (wood and brush) and have a large pile of cut green vegetation close by. When an aircraft is heard, the dry materials are placed on the fire, allowed to flare, and then armloads of the green vegetation are piled on top. This produces lots of smoke and a hot thermal updraft to carry it aloft. Ground signals (e.g., SOS, HELP) should be as large as possible—at least 3 feet wide and 18 feet long—and should contain straight lines and square corners, which are not found in nature.

They can be tramped out in dirt or on grass or can be made from brush or logs. In snow, the depressions can be filled with vegetation to increase contrast. Many pilots do not know the traditional 18 international ground-to-air emergency signals. These have been replaced by the following five simple signals adopted by the International Convention on Civil Aviation.18 Although in the age of helicopters these are not as important as they once were, they are worth remembering: V: I require assistance. X: I require medical assistance. N: No Y: Yes →: I am proceeding in this direction. Air-to-ground signals include the following: Message received and understood: rock plane from side to side. Message received but not understood: make a complete righthand circle. When using cell phones, radios, and other electronic devices, persons should move out of valleys and gullies to higher elevations if possible. Operational pay phones in campgrounds closed for the season or other facilities can be used to call for help. Most will allow 911 or another emergency number to be dialed without payment, but carrying sufficient coins and memorizing your telephone credit card number are recommended.

Protection from Wild Animals Although persons in a survival situation often worry about wild animal attacks, these are rare. Many wild animals flee when confronted with a shouting, moving human. Exceptions include polar bears, grizzly bears, moose, bison, cougars, jaguars, wild pigs, elephants, lions, tigers, water buffalo, leopards, wolverines, females with young (particularly bears, moose, elk, and deer), rabid mammals, and feral dogs and cats (see Chapters 51 and 52). Polar bears, some grizzly and back bears, the great cats, and crocodiles may hunt humans as food. Venomous snakes, insects, arachnids (spiders, scorpions, and ticks), and marine animals are also a concern (see Chapters 44 to 50). The only effective weapon against large mammals and reptiles is a high-powered firearm, although pepper spray may discourage attacking bears and ungulates. Improvised weapons, such as a spear tipped with a hunting knife, are useless. Food should not be kept in a shelter or backpack during the night. All food should be placed in a nylon bag and hung between two trees on a high line. Above timberline, small rodents such as mice may gnaw holes in expensive tents to reach food inside, so all food should be bagged and hung on a line between two high boulders. In warm weather, insect repellent should be carried and used liberally.

Summary of Preparations for a Possible Survival Situation 1. Keep in good physical condition by frequent exercise and healthful habits. Avoid tobacco and “recreational” drugs; keep alcohol to a minimum. Maintain current immunizations.

Chapter 36: Essentials of Wilderness Survival 2. Develop the ability to swim well. 3. Learn how to use a map and compass and find directions without a compass. 4. Be able to build a fire under adverse conditions. 5. Have a working knowledge of local weather patterns and be able to use an altimeter (or barometer), thermometer, wind directions, and knowledge of cloud forms to predict storms. Avoid exposure to dangerous meteorologic conditions, such as blizzards and lightning strikes. 6. Be familiar with the special medical problems of the type of wilderness involved. For example, in cold weather and at high altitude, be familiar with the prevention, diagnosis, and treatment of hypothermia, frostbite, and altitude illnesses. Safe travel in the desert and tropics requires familiarity with tropical infections, snakebites, tropical skin diseases, and heat illnesses. Understand basic principles of prehospital emergency care and the improvisation of splints and bandages. 7. Carry a survival kit containing equipment appropriate for the topography, climate, and season (see appendices to this chapter). At a minimum, the kit should include such things as fire-starting, shelter-building, and signaling/navigating equipment plus emergency food, water, spare clothing, and a first-aid kit. 8. Be able to construct appropriate types of survival shelters. 9. Acquire a working knowledge of the characteristics of natural hazards and how to avoid them. These include forest fire, lightning strike, avalanche, rock-fall, cornice fall, flash flood, whitewater, dead-falls, storms of various kinds, and the hazardous animals and plants of the area of travel. 10. Read and analyze accounts of survival experiences (see “Suggested Readings” at the end of this chapter). Remember that more people are killed on simple day hikes than on long wilderness expeditions.14 11. Be aware of the psychological aspects of a survival situation and of errors in judgment that can lead to a survival emergency. 12. Know the edible plants and animals of the area of projected travel, as well as the poisonous or venomous species. Know how to obtain water. Basic hunting, trapping, and fishing skills are valuable. 13. Be intimately familiar with the contents of your survival kit and how to use them. Practice and perfect survival activities such as fire building and shelter building before you need them. 14. Never travel alone. Hunters and other group members who may separate should have means of communicating with each other, such as small radios with a 5-mile (8 km) range. Products are available that combine a GPS locator with a small radio. 15. Always let at least two responsible persons know your destination, the number of persons in the party, their names, the type of vehicles and license plate numbers, and expected time of return. Add several hours to the latter for “normal” mishaps and miscalculations.14 To avoid unnecessary rescue attempts, do not fail to notify these persons of your return. Failure to follow these guidelines has led to many unsuccessful searches.

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APPENDIX A: SUGGESTED BASIC CONTENTS OF TEMPERATE TO COLD WEATHER SURVIVAL KIT

The kit is divided loosely into fire-building, shelter-building, signaling/navigating, and miscellaneous items, all of which will fit into a small backpack (capacity, 3200 to 4000 cubic inches [52.4 to 65.5 L]). The small items can be carried together in a small net bag for convenience and easy identification. Frequently used items, such as a knife, map, dark glasses, and compass, should be in a pocket or on the belt. Always remember to replace consumed items, especially first aid items, repair kit items, and emergency food, as soon as you return from a trip. Replace stored matches at least every year and first aid kit medications before they expire. APPROXIMATE WEIGHT (ounces [grams])

ITEM Fire-Building Equipment Two waterproof screw-top match containers filled with “strike-anywhere” matches or Recreational Equipment, Inc. “storm-proof” matches. If match container doesn’t include a large, rough matchstriking area, a strip of heavy sandpaper should be glued to the top or side of each container. Candle Fire-starter, e.g., cotton impregnated with Vaseline, in waterproof container such as film can or additional match container Metal match Knife: Swiss Army (consider “camping” model with saw, file, scissors, etc., made by Victorinox) Alternate: Leatherman tool with wire-cutting pliers, file, one serrated and two regular blades, saw and scissors Shelter-Building Equipment 1 /8-in braided nylon cord or parachute cord, 100 ft (30.48 m) Rip-stop waterproof nylon tarp, approx. 8 × 10 ft (2.4 × 3 m) with grommets around the edges. Campmor is a good brand. (See online at www.campmor.com.)

2 (57)

1.5 (43) 1 (28) 0.5 (14) 5 (142) 8 (227)

4 (113) 19.5 (55.3)

Alternatives: “blue, crinkly” tarp (laminated polyethylene weave) 26 (737) or 1 to 2 large, heavy-duty (3- to 4-mil) orange plastic 9–18 bags, 3 × 51/2 ft (0.9 × 1.7 m) (255–510) Folding saw or small rigid saw, such as 18-in Dandy 12 (340) Saw Signaling/Navigating Equipment Headlamp (or flashlight) with spare bulb and 7.5 (212) batteries. A good choice is a headlamp with both LED and bulb options. The LED light uses up much less electricity but is more diffuse and doesn’t cast a long beam. The bulb is brighter and casts a longer beam but uses much more electricity.

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Plastic whistle (pea-less) on lanyard Small notebook and pencil Small roll of orange surveyor’s tape Glass signaling mirror with sighting device

0.5 (142) 1.5 (43) 2 (57) 2 (57)

Miscellaneous Metal pot with bale, containing emergency food of 34 (964) choice (e.g., tea, soup mix, power bars, small can of mixed nuts, trail-mix) Metal cup with handle (can heat liquid by putting 3 (85) cup at edge of fire) Plastic or Lexan spoon 0.5 (14) Toilet paper 1.5 (43) Sunburn cream with SPF 30 or greater 4 (113) Lip balm with SPF 30 or greater 0.5 (14) Insect repellent such as DEET (in season) 4 (113) First aid kit, one per party (see below for contents) 25 (701) Canteen (1 to 1.5 L), full; metal or plastic 38.5–51.0 (1091–1446) Sunglasses, preferably polarized with side shields 2 (57) Light raingear, e.g., laminated (Gore-Tex, etc.) 31 (879) jacket with hood and pants Repair kit, adapted to type of travel (e.g., ski, snowshoe, kayak), including: Small needle-nosed pliers with wire-cutting feature 3 (85) (if Leatherman tool not carried) Small crescent wrench 2 (57) Small screwdriver with multiple tips 5.5 (156) Picture wire 1 (28) Fiberglass tape—standard roll 3 (85) Duct tape, small roll 1 (28) Steel wool for shimming (ski binding repair, etc.) 1 (28) Assorted nuts, bolts, and screws 1.5 (43) Total weight of repair kit 18 oz (510) Total weight of basic survival equipment (not including shovel, snow saw, approx. 230 to 250 oz backpack, or cold weather fourth = 14 to 16 lb layer—see below under Winter (6.4 to 7.3 kg) Survival List) Other Useful Equipment for Consideration Nondigital watch Altimeter Magnifying glass Two sets of correct change for pay phone Light pair of leather gloves (hand protection) Water disinfection equipment: chemicals (Potable Aqua, etc.) or filter Thermometer (e.g., plastic alcohol type clipped to outside of pack) Spare eyeglasses Electronic communication/navigation equipment: Cellular telephone (if service available) Global Positioning System locator Personal locator beacon (personal emergency locator transmitter) Pepper spray (to repel bears, moose, etc.) Usual Day Trip Items to Be Added Small thermos of hot or cold drink Lunch Binoculars Camera


APPENDIX B: SUGGESTED

ADDITIONS FOR WINTER SURVIVAL KIT (COLD WEATHER OR SNOW PRESENT OR EXPECTED)

Basic survival items from Appendix A Spare clothing for severe weather, to provide at least four layers total, including spare mittens Small snow shovel, e.g., small collapsible grain-scoop type with Kevlar blade and detachable handle (24 oz) Snow saw (consider for above-timberline travel/igloo building) (8 oz) Optional Items 3 /4-length piece of open or closed cell foam mattress or Therm-a-Rest mattress Sleeping bag Bivouac sac Small stove and fuel Light ax (Hudson’s Bay type) Small piece of closed-cell foam (2 × 2 feet) for sitting in snow Mandatory for Avalanche Country Avalanche probe (folding) or ski poles that join together to form probe for each party member Avalanche transceiver for each party member Shovels—preferably one for each party member Inclinometer for measuring slope angles (included in some compasses)


APPENDIX C: VEHICLE COLD WEATHER SURVIVAL KIT

Sleeping bag or two blankets for each occupant Extra winter clothing, including gloves, boots, and snow goggles, for each occupant Emergency food Metal cup Waterproof matches Long-burning candles, at least two First-aid kit (see Appendix D) Spare doses of personal medications, if any Swiss Army knife or Leatherman multitool Three 3-lb empty coffee cans with lids, for melting snow or sanitary purposes Toilet paper Citizen’s band radio, cell phone, etc., with chargers Portable radio receiver, with spare batteries Flashlight with extra batteries and bulb Battery booster cables Extra quart of oil (place some in hubcap and burn for emergency smoke signal) Tire chains Jack and spare tire Road flares Snow shovel Windshield scraper and brush

Chapter 36: Essentials of Wilderness Survival Tow strap or chain Small sack of sand or cat litter Two plastic gallon water jugs, full Tool kit Gas line deicer Flagging, such as surveyor’s tape (tie to top of radio antenna for signal) Duct tape Notebook and pencil Book to read Long rope (e.g., clothesline) to act as safety rope if you leave car in blizzard Carbon monoxide detector Ax Saw Full tank of gas Data from Winter Survival Handbook. Available at: Montana State Department of Transportation website, http://www.mdt.state.mt.us.


APPENDIX D: MINIMAL

EQUIPMENT FOR SURVIVAL FIRST-AID KIT

Recognizing that the most common significant medical problems will be injuries, each item is selected based on likelihood of need, possibility of multiple use, urgency of need, weight to usefulness ratio, “biggest bang for the buck,” and whether it can be improvised from natural materials. As with the survival kit, the small items can be carried together in a mesh bag for faster location. Basic Items Small Bag Items CPR mouth shield Surgical gloves, preferably nonlatex 20-mL syringe with needle, catheter, or splash shield for wound irrigation Steel sewing needle (can be part of small sewing kit) Clinical thermometer (consider low-reading thermometer for cold environment) Small pill boxes containing: Nonprescription analgesic of choice (acetaminophen, ibuprofen, etc.). Consider ibuprofen if frostbite risk. Prescription analgesic of choice (acetaminophen with codeine, etc.) Diphenhydramine, 25 or 50 mg caps Small tube of biodegradable soap Splinter forceps Seam ripper Small needle holder (useful for retrieving small things out of tight quarters) Small magnifying glass Four large safety pins Other Items 1 or 2 cravats Roll of 3-inch Ace or self-adhering roller bandage Roll of 2-inch adhesive tape (waterproof preferred) Small roll of 1/2-inch 3M Transpore tape Small, prepackaged bandage strips, 1 inch (can cut in half length-wise for smaller sizes)

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Nonadhering sterile gauze pads (Telfa or equivalent), 3 × 4 inch Sterile compresses, 4- × 4-inch Alcohol pledgets for skin cleansing Duct tape, fiberglass strapping tape (for improvising litters and splints; carried in repair kit) Additional Items for Consideration Acetazolamide if acute mountain sickness risk (125–250 mg twice daily to speed acclimatization) Plastic oral airways (three sizes) Pocket mask (instead of mouth shield). This device is easier to use, works better than a mouth shield, and protects the user from the victim’s saliva. Povidone-iodine swabs for skin preparation 14-gauge IV catheter-over-needle (emergency chest decompression). A flutter valve can be improvised by using the finger cut from a rubber glove with its base tied around the base of the catheter and a hole cut in its tip. Small bandage scissors or paramedic shears (substitute: scissors on Swiss Army knife or Leatherman tool) Small, light-weight stethoscope SAM splint Persons who are taking regular medications should carry emergency supplies of their medicines in addition to regular supplies; anyone who has had an anaphylactic reaction should carry an emergency epinephrine kit (EpiPen)


SUGGESTED READINGS Accidents in North American Mountaineering: Golden, CO, American Alpine Club, and Banff, Alpine Club of Canada, 1999 (published yearly by the Lyons Press, Guilford, CT). Anderson K, Tavernier A (eds): Wilderness Basics, 3rd ed. Seattle, Sierra Club, Mountaineer’s Books, 2004. Auerbach PS: Medicine for the Outdoors, 4th ed. Guilford, CT, The Lyons Press, 2003. Clifford H: The Falling Season. New York, HarperCollins, 1995. Craighead FC Jr., Craighead JJ (revised by Smith RE, Jarvis DS): How to Survive on Land and Sea, 4th ed. Annapolis, MD, U.S. Naval Institute, 1984. Kochanski M: Bushcraft: Outdoor Skills and Wilderness Survival. Vancouver, Lone Pine, 1987. Krakauer J: Into Thin Air. New York, Villard, 1997. Landsing A: Endurance. New York, Avon, 1976. Logan N, Atkins D: The Snowy Torrents: Avalanche Accidents in the United States, 1980–1986. Denver, Colorado Geological Survey, 1996. MacInnes H: The Price of Adventure: Mountain Rescue Stories from Four Continents. Seattle, The Mountaineers, 1978. MacInnes H: High Drama: Mountain Rescue Stories from Four Continents. Seattle, The Mountaineers, 1980. Nesbitt PH, Pond AW, Allen WH: The Survival Book. New York, Funk & Wagnall, 1959. Olson LD: Outdoor Survival Skills, 6th ed. Chicago, Chicago Review Press, 1997. Parr P: Mountain High Mountain Rescue. Golden, CO, Fulcrum, 1987. Patterson CI: Surviving in the Wilds. Toronto, Personal Library Publishers, 1979. Ralston A: Between a Rock and a Hard Place. New York, Atria Books, 2004.

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Randall G: Cold Comfort: Keeping Warm in the Outdoors. New York, Lyons Books, 1987. Riles MJ: Don’t Get Snowed: A Guide to Mountain Travel. Matteson, IL, Greatlakes Living Press, 1977. Rutstrum C: Paradise Below Zero. New York, Collier Books, 1974. Simpson J: Touching the Void. New York, HarperCollins, 1988. U.S. Army Survival Handbook. Department of the Army. Guilford, CT, The Lyon’s Press, 2002.

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Waterman J: Surviving Denali: A Study of Accidents on Mount McKinley, 1903–1990, 2nd ed. New York, AAC Press, 1991. Whittlesey LH: Death in Yellowstone: Accidents and Foolhardiness in the First National Park. Boulder, CO, Rinehart, 1995. The references for this chapter can be found on the accompanying DVD-ROM.

Jungle Travel and Survival John Walden


TROPICAL ENVIRONMENT In these forests lies a virtually limitless supply of excitement, joy, and wonder to be encountered in new illuminations on the constructs and workings of life on earth.31 Tropical rainforests, located between the Tropic of Cancer (23° 27′ N latitude) and the Tropic of Capricorn (23° 27′ S latitude), are regions with at least 4 inches of precipitation per month and a mean annual monthly temperature exceeding 24° C (75° F) without any occurrence of frost. Contrasted to temperate regions, the hours of day and night are about equal throughout the year. Seasons are characterized as “wet” or “dry.” These seasonal designations refer to historical trends and should not be taken as gospel: in some years, the dry season extends for months beyond the usual range; in other years, the rains may persist for months as a daily drizzle, making it difficult to trek over the spongy terrain. In the Pacific coastal region of the Colombian Chocó and the Cayapa River Basin of Ecuador, where annual rainfall can exceed 400 inches, the seasons are said to be “wet” and “wetter.” As the most biologically diverse community of living things on Earth, the tropical rainforest is a realm of superlatives: a single acre of tropical forest may contain more than half as many species of trees as occur in all the land mass of temperate North America; one square mile of Amazonian forest may be home to double the variety of butterflies that exist in all of the United States and Canada; a single tree in Peru yields as many species of ants as in all of the British Isles. Facts and figures fail to capture the essence of tropical rainforests and their extraordinary biologic diversity. Seen from the air, the forest stretches from horizon to horizon in a vast green carpet. In season, the crowns of trees in full blossom dot the landscape with vivid splashes of red, orange, and yellow. Sizable streams may be hidden beneath the emerald canopy. Rivers, usually muddy yellow or black, snake through the forest; early-morning

or late-afternoon sun transforms these braided rivers into glistening, mirrorlike strands of liquid silver. Observed from the forest floor, the jungle is entrancing. In virgin, deep forest, all is muted and shadowy, save for random shafts of light that spotlight labyrinths of oddly shaped branches and spectacularly colored flowers. Shrubs and herbaceous plants are scarce in forest away from the flood plain, so it is relatively easy to walk undisturbed. The dimness is occasionally disrupted by areas bathed in bright light from larger holes in the canopy caused by a recently fallen tree, sandy beach, or cutting and burning by humans. It is in these sunlit areas that the traveler encounters the lush and nearly impenetrable wall of foliage portrayed in adventure films. The tidy textbook division of vegetation into distinct tiers is somewhat arbitrary and not easily confirmed, even by experts.36 In addition to drier upland terra firme forests, lowland forests remain submerged for several months each year. Such forests, or várzeas, make up only a small percentage of forested land, but are infinitely more fertile than their nonflooding and nutrient-poor counterparts. Despite environmental differences within the jungle, the basics of travel remain the same.


TRIP PREPARATION Reading Back issues of National Geographic magazine and the writings of Wilson provide an excellent introduction to people, places, and biodiversity issues.4,51,52 The Smithsonian Atlas of the Amazon,18 the definitive illustrated atlas (150 color maps and 289 photographs) of the region, is highly recommended, as is the Conservation Atlas of Tropical Forests series (Asia and the Pacific,9 Africa,38 the Americas22). The references at the end of this chapter offer insights into the complex inner workings of the moist tropical forest.1,35,36 The books by Kritcher26 and Forsyth and colleagues17 are especially helpful.

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Trips into the rainforest should be scheduled for the dry season because trails are more serviceable for trekking at that time. Information on weather patterns can be obtained from agencies of national governments, anthropologists, missionaries, and the series entitled World Survey of Climatology, which is available in large reference libraries.43 The Times Books World Weather Guide by Pearce34 is a comprehensive guide to the weather of every country for every month of the year. Although out of print, this guide is easily obtained from any major online marketplace for used, rare, and out-of-print books. The National Climatic Data Center (www.ncdc.noaa. gov) is an excellent source for weather patterns and trends worldwide. Weather Underground (www.wunderground.com) provides current, as well as seasonal, weather averages for many cities in tropical regions.

Attitude In selecting participants, experienced expedition leaders look for a sense of humor. The ability to see the bright side in difficult times may be an asset more valuable than physical conditioning. Houston24 and others have discussed the role of humor as a predictor of success. Erb13,14 noted that successful or failed participation in wilderness ventures also is a significant predictor.

Relationship Considerations Couples routinely report benefits from the shared experience of wilderness adventure travel, ecotourism, and academic field research. However, in the setting of high-risk expeditions where safety and prompt rescue cannot be assured, a number of group leaders privately note that two individuals who have a sexual relationship may form a team within a team, to the detriment of the expedition as a whole.49

Conditioning Indigenous peoples in jungle regions are almost always slender. After trekking with large numbers of nonindigenous men and women in equatorial regions, I have observed that overweight or powerfully built individuals, particularly men, seem to fare the worst, especially with heat-related illness. Achieving an ideal body weight and becoming aerobically fit by walking or jogging for extended periods of time is beneficial before jungle trekking. Although being in good shape is sensible, a person need not be an elite athlete to trek through the jungle and enjoy the experience. Good leg strength, acquired by training 20 to 30 minutes on alternate days with stair-climbing exercise machines, offers appropriate preparation. To keep up with native porters and guides, the prospective expedition member should practice hiking at a fast pace. Once in the jungle, travelers should imitate the energy-saving, fluid rhythm of local inhabitants. Because trekkers frequently encounter single-log bridges, a well-developed sense of balance is desirable (Fig. 37-1). Walking on the rails of untrafficked train tracks or on roadway curbs may help in preparation. To adapt to specific situations, trekkers should go to the woodlands and practice walking on logs. Head stability is important. Equilibrium can be enhanced by avoiding brisk head movements and by employing the “gazeanchoring” technique of tightrope walkers. The person fixes the gaze on a spot near the end of the log and does not stare down at the spot just ahead of the feet.3,8 Special cleats (Covell Ice Walker Quick Clip cleats) (Fig. 37-2) should be considered for

Figure 37-1. A well-developed sense of balance is desirable.(Photo courtesy of John Walden.)

Figure 37-2. Covell Ice Walker Quick Clip cleat. (Photo courtesy of Jon Willis.)

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crossing log bridges that are high off the ground, long, and slippery. The cleats can be snapped on quickly before crossing a log bridge and promptly snapped off at the other end.


IMMUNIZATIONS Travelers to rainforest regions should protect against the following diseases by vaccination or with prophylactic medications (see Chapter 77): 1. Diphtheria, tetanus 2. Hepatitis A, hepatitis B 3. Influenza (see later) 4. Measles, mumps, rubella 5. Polio (where appropriate) 6. Rabies (see Chapter 54) 7. Typhoid 8. Yellow fever (in certain regions of tropical Africa and South America) 9. Malaria (see Chapter 43) Malaria is prevalent throughout the tropics. Before travel to malarious areas, appropriate prophylaxis is needed. Updated information on the risk for malaria in various regions may be obtained through the Centers for Disease Control and Prevention (www.cdc.gov/travel). The Medical Letter on Drugs and Therapeutics (www.medicalletter.com) is an excellent source for current recommendations on preventing and treating malaria. Persons traveling into remote regions of Amazonia where Indian groups live in isolation should receive yearly influenza vaccinations to reduce the likelihood of inadvertently transmitting disease to these high-risk native inhabitants. Protection against meningococcal disease should be considered where circumstances warrant.

Medical Kit The Wilderness Medical Society points out that it is inappropriate to pack medications and equipment when no team member has the knowledge or experience to use them safely.25 The following items for a basic medical kit (Box 37-1) are adequate for personal use in the rainforest setting:

Box 37-1. Medical Kit for Jungle Travel Bismuth subsalicylate tablets (48) Diphenhydramine hydrochloride, 25- or 50-mg capsules (15) Ciprofloxacin hydrochloride 500-mg tablets (20) Clotrimazole and betamethasone dipropionate cream (60 g) Epinephrine autoinjector (2 adult, 2 child) Ibuprofen, 200- or 600-mg tablets (30) Ketorolac, 60-mg single-dose syringe (2) Lidocaine hydrochloride carpules (3) Metronidazole, 250-mg tablets (21) Mupirocin ointment 2% (30 g) Permethrin, 5% cream (60 g) Permethrin, 1% shampoo (2 oz) SAM splint (1) Sulfacetamide sodium ophthalmic solution 10% (15 mL) Sunscreen (4 oz) (2) Tramadol hydrochloride, 50-mg tablets (20)

1. Bismuth subsalicylate (Pepto-Bismol tablets) is an effective over-the-counter preparation for preventing and treating common traveler’s diarrhea. It also is useful for heartburn and indigestion. Pepto-Bismol tends to turn the tongue and stools black. 2. Diphenhydramine hydrochloride (Benadryl, 50-mg capsules) is safe and effective as an antihistamine, for motion sickness, and as a nighttime sleep aid. 3. Ciprofloxacin hydrochloride (Cipro, 500-mg tablets) is highly active against the important bacterial causes of enteritis, including diarrheogenic Escherichia coli, Vibrio cholerae, Salmonella species, Shigella species, Campylobacter jejuni, Aeromonas species, and Yersinia enterocolitica. 4. Clotrimazole and betamethasone dipropionate (Lotrisone) cream combines an antifungal with a steroid for rashes. 5. Epinephrine autoinjector (EpiPen/EpiPen Jr.) provides for emergency treatment of severe allergic reactions to insect stings, foods, or drugs. 6. Ibuprofen (600-mg tablets) is a good choice for mild to moderate pain from such problems as menstrual cramps, rheumatoid arthritis, and osteoarthritis. It also lowers elevated body temperature caused by common infectious diseases. 7. Ketorolac (Toradol, 60 mg for injection) provides good short-term relief for moderate to severe pain. It is preferred over narcotics only because it is less likely to cause problems with customs officers and police. 8. Lidocaine hydrochloride may be required as a local anesthetic agent for relief of the excruciating pain resulting from stingray envenomation or conga ant and caterpillar stings. It should be infiltrated into and around the wound area using a dental syringe and 25-gauge needle. Lidocaine carpules (used by dentists) are protected and easy to carry and use in the rainforest.19 9. Metronidazole (250-mg tablets) is excellent for treating giardiasis, acute amebic dysentery, and Trichomonas species vaginitis. 10. Mupirocin (Bactroban) ointment 2% should be immediately applied to burns, abrasions, lacerations, and ruptured blisters, which can rapidly become infected in the tropics. 11. Permethrin 5% cream and 1% shampoo should be applied to treat scabies and head lice before returning home by travelers who have been in close contact with heavily infested tribal peoples. Many natives, especially in the tropics of Central and South American, are infested with these ectoparasites. Oral ivermectin (200 µg/kg) can also effectively treat scabies and head lice.16 Marmosets and tamarins are often kept by indigenous peoples of the Americas as pets to aid in grooming for head lice (Fig. 37-3). 12. The SAM splint is lightweight, waterproof, reusable, and not affected by temperature extremes. 13. Sulfacetamide sodium (Sodium Sulamyd/Bleph-10) ophthalmic solution 10% is excellent for treating conjunctivitis, corneal ulcers, or other superficial ocular infections. 14. Sunscreen is essential in open areas such as rivers or jungle clearings. Sunscreens designated “waterproof” retain their full sun protection factor (SPF) rating for

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Gear The goal is to travel as “light” as possible. The more gear that is packed, the greater is the likelihood of breakdowns, complications, and misery. The items mentioned in Box 37-2 have withstood the test of time over years of long-distance tropical trekking. Gear must hold up under difficult jungle travel conditions that include heat, wetness, and mud. No line of advertised gear is ideally suited for the traveler in the tropics. In the United States, L. L. Bean, Inc. (www. llbean.com) and Recreational Equipment, Inc. (REI) (www.rei.com) are good sources for equipment, especially clothing and footwear, that is usually satisfactory for the tropics.

Footwear Because feet absorb more punishment than any other part of the body, suitable footwear is the most important item of gear. This is one area in which a person absolutely must not carry inferior equipment. If the feet cannot go, nothing can go. Military “Vietnam-style” jungle boots with leather uppers, steel insole plates, and speed lacing are unsuitable for serious, long-distance trekking. After an hour of hard walking through streams and muddy trails, blisters can form on every surface of the foot, and the skin will peel off in sheets, bringing a jungle trip to a premature end. Furthermore, safely crossing log bridges and mossy, slime-covered river rocks is almost impossible in these boots. Two pairs of shoes are needed: one suitable for the wet, slippery conditions imposed by the trail and another that meets the need for dryness and comfort in camp.

Trail Shoes

Figure 37-3. Tamarins and marmosets are kept as pets to aid in grooming for head lice.(Photo courtesy of John Walden.)

longer periods during sweating or water immersion than do products designated “water resistant.” Opaque formulations are excellent for the nose, lips, and ears. Visitors to the tropics should wear lightweight, long-sleeved shirts and a wide-brimmed hat when exposed to the sun for prolonged periods. 15. Tramadol hydrochloride (Ultram, 50-mg tablets) is used for moderate to severe pain. Common sense dictates supplementary items. Women on long trips might add miconazole vaginal suppositories or fluconazole (Diflucan, 150 mg as a single oral dose) to treat yeast infections; older men might take a 16-French catheter and sterile lubricating jelly for dealing with urinary retention from prostatic hypertrophy. The fingers may swell rapidly during vigorous activity in the rainforest. To eliminate the possible need for emergency removal, all rings (including toe rings) should be removed before jungle trekking. Body piercings should be removed to eliminate the risk for infection.

The following features are desirable in trail shoes: 1. Uppers that hit just above or just below the ankles. Some people choose a high-cut design, reasoning that the extra height gives some added snake protection. 2. Extra protection over the big toe. Rubber or leather toecaps prevent the big toe from being severely battered and bruised. 3. Moderately deep-tread outsoles. Traction on rugged and muddy terrain is important. Running shoes with hard, “high-impact” soles should not be worn because they become slippery on wet logs or river rocks. 4. Quick drying time. Uppers of Cordura nylon and split leather, in addition to resisting abrasion and being aerated, dry rapidly in the sun. Even though hiking shoes usually become soaked within minutes on the trail, it is a psychological boost to start each day with dry shoes. Because jungle travelers can be in waist-high water while on the trail, waterproof shoes with Gore-Tex liners are not essential. 5. Snag-proof design. Shoes or boots with “quick-lace” steel hooks should be avoided; vines and weeds become tangled around the metal hooks, causing the wearer to stumble and pulling the laces untied. Shoelaces should always be double knotted. 6. Lightweight 7. Well broken in

Camp Boots Footwear needs are different in camp, where the trekker wants dry feet. Shoes, although excellent for the trail, are not suited

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Box 37-2. Gear for Jungle Travel Trail shoes (1 pair) Camp boots (1 pair) Covell cleats Socks, lightweight cotton or thin nylon (3 pairs) Hat (1) Pullover garment, polyester (1) Shirts, cotton Long sleeved (2) Short sleeved (2) Pants, lightweight cotton or Supplex or Taslan (2 pairs) Undergarments Underpants, lightweight polyester mesh (3) Sports bra, cotton or cotton-Lycra blend mesh (2) Poncho, nylon (1) Flannel sheet Hammock or Therm-a-Rest Mosquito net Backpack for porter Personal backpack Antifogging solution for eyeglasses Batteries Binoculars Camera equipment and film Campsuds Candles, dripless Cup (Lexan polycarbonate)/plate (melamine)

Duct tape, 1 small roll Ear plugs Fishing supplies Garbage bags 30-gallon size (4) 13-gallon size (4) Headlamp Inflatable cushion Insect repellent Laminated maps Machete (Collins style) Waterproof matches or butane piezo ignition lighter Pen Toilet paper Leatherman pocket survival tool Polycarbonate wide-mouth bottles (2) Razor/battery-operated shaver Spoon Sport sponge Sunglasses Umbrella Whistle, plastic Zipper-lock bags Gallon size (5) Quart size (5) Pint size (5)

for camp. A noninsulated, pull-on (laceless), open-top boot that comes to midcalf keeps mud off the feet and pants and, when worn with thin nylon socks, allows enough air to circulate to keep the feet cool and dry. Rubber remains an excellent material for keeping water away from the feet. Rubber lug soles provide traction. When rubbersoled boots are worn at an encampment, however, extreme caution is needed when crossing bridges and walking on wet rocks. Camp boots should be lightweight because they must be carried in a pack on the trail. Discount stores usually carry lightweight, lug-soled rubber boots that meet the criteria for jungle camp boots.

Other Options The lightweight, comfortable, mesh/neoprene fabric “water” shoes popular for beach and sailboarding activities may have a place on river trips when substantial time will be spent in dugout canoes or rubber rafts. Thongs and open-toe sandals are fine for most towns and cities in the tropics, but in certain jungle regions, such as the Amazon Basin, exposed feet invite hordes of biting insects. The jungle traveler must never go barefoot. Plant spines and glass can puncture the feet, and larvae of ubiquitous parasites, such as Ancylostoma duodenale and Necator americanus (the hookworms) and Strongyloides species can enter through the skin. The burrowing jigger flea, Tunga penetrans, is a serious pest and can be avoided by wearing shoes.

Socks Cotton or thin synthetic socks should be worn in the jungle to decrease the risk for blisters from wet trail shoes, to reduce

Figure 37-4. Sawgrass. (Photo courtesy of V. Ramey, University of Florida, Center for Aquatic and Invasive Plants.)

insect bites, particularly from no-see-ums (family Ceratopogonidae), and to lessen the risk for lacerations from sawgrass (Fig. 37-4).

Clothing In many countries, military green or camouflage-style clothing is strictly contraindicated. This is particularly true in military dictatorships or in remote border regions. To be mistaken for a guerilla or foreign infiltrator by the military, police, or security (undercover) forces can lead to harassment, detention, or worse.

Chapter 37: Jungle Travel and Survival

Hat For protection from radiant heat and objects falling in the forest, the traveler should wear a lightweight, light-colored hat that has a medium or wide brim. It need not be waterproof, but should be made of material that can be wadded up. A useful feature is a fastener on each side to snap the brim up for traveling on the trail. A pith helmet, widely regarded as an affectation, is fine for open savanna and river trips, but on the trail, branches make it impractical.

Pullover Drenching rain may leave a person feeling chilled and uncomfortable, particularly when traveling mainly by canoe or raft. Chilling generally is not a problem when hiking on the trail as long as the person keeps moving. A Dacron polyester fleece pullover, such as L.L. Bean’s Polartec pullover, REI’s polyester lightweight MTS long-sleeve crew, or Patagonia’s polyester pullover, will keep a person warm. Wet garments should be wrung out so that they continue to offer thermal protection. Professional white-water boatmen working in tropical regions generally pack a polyester outerwear garment.

Shirts Two light-colored, ultra-lightweight, long-sleeved cotton shirts should be taken. At the end of the day, the trail shirt should be washed and rinsed so that it will be ready, although perhaps still damp, the next morning. The second shirt can be used in camp or as a spare for the trail. Expensive synthetic shirts guaranteed to wick away moisture are poor jungle trail shirts and make the person sweaty and sticky. In camp, if no-see-ums and mosquitoes are few, a lightweight, short-sleeved cotton shirt is practical. Two should be packed. A four-pocket style called the guayabera, favored by men throughout Latin America and the Caribbean, is ideal. La Casa de Las Guayaberas (Naroca Plaza, 5840 SW 8th St., Miami, FL 33144; 305-266-9683; fax 305-267-1687) has an exceptional selection of short- and long-sleeved guayaberas; be sure to specify 100% cotton.

Pants Two pairs of ultra lightweight, light-colored cotton pants are needed. One pair is worn on the trail during the entire trip. Trail pants should be washed often. The other pair is worn around camp and in towns along the way. Jeans become waterlogged as soon as they become wet and are totally unsuitable for tropical trekking. Although synthetic shirts are unsuitable, nylon Supplex or Taslan pants with a built-in mesh brief can substitute for cotton. Pants made of these materials hold up well, are quick drying, and meet criteria for comfort on the trail. Pants with zip-off legs to create instant shorts should be avoided; they will not hold up to strenuous trail conditions.

Undergarments Underpants and sport bras should be made of cotton or polyester mesh.

Poncho An ultrathin waterproof poncho is useful on rafting or canoe trips and in villages, but is worthless for use on the trail because it will become snagged on twigs and tree spines.

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Bedding Flannel Sheet Tropical rainforests become uncomfortably cold between midnight and sunrise. A cotton sheet does not provide enough warmth, a blanket is too heavy, and a summer-weight sleeping bag retains too much body heat. A flannel sheet sewn together like a mummy bag (40 × 90 inches), but without a taper, provides suitable warmth placed either in a hammock or on a pad. Many inhabitants of the tropical forests sleep with their feet near a fire that is tended throughout the night. They have learned that the chill of damp, cool jungle nights can be lessened as long as the feet stay warm. Disposable “warm packs” (Heat Treat Toe Warmers) can be attached by the adhesive backing to the outside of your sock, under your toes.

Hammock Soft cloth hammocks are too bulky and heavy for trips and begin to smell after a few days. Fishnet cotton hammocks tend to fall apart within hours or days. So-called camping tenthammocks or military tent-hammocks are usually bulky, heavy, impossible to sling properly, extremely uncomfortable, hot, unstable, and never able to keep the rain out in a heavy tropical downpour. The nylon Marina Double Hammock (Model EZ-199 by E-Z Sales Manufacturing, 1432 West 166 St., Gardena, CA 90247) sold by Wal-Mart and REI has proved nearly ideal for jungle travel. It is compact, lightweight, durable, and reasonably comfortable. It cannot rot or absorb odors. For easier handling, the ski rope tie-end lines that are sold with the Double Hammock should be replaced with 3/8-inch nylon double-braided rope available from home improvement retailers or a boating supply source such as West Marine (www.westmarine.com).

Therm-a-Rest The Therm-a-Rest foam pad is the choice of expedition organizers in temperate and cold climates throughout the world. It combines the insulating qualities of foam and the cushioning of an air mattress, rolls up to a compact size, and inflates on its own when the valve is opened. The traveler who will be sleeping on a pad should pack a 11/2× 21/2-yard (1.4- × 2.3-m) plastic ground sheet. The sheet should not be placed directly on the jungle floor, where stinging insects and snakes abound. It should be used only in a hut or on an elevated platform. The ground sheet may also be beneficial for temporary rain protection and for keeping bow spray off a person or gear during water travel. For jungle travel, I prefer a hammock over a foam pad.

Mosquito Netting A mosquito net designed for use with a hammock is basically a rectangular box that is open at the bottom with sleeves at each end panel for the passage of the ropes by which the hammock is slung. Such nets are difficult to find outside the tropics. Fortunately, a serviceable mosquito net can easily be made from “no-see-um netting” (REI No-See-Um Mosquito Net: available by request). See later in this chapter for details of mosquito net construction.

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Figure 37-5. Indigenous peoples are accustomed to hauling loads using a tumpline. (Photo courtesy of John Walden.)

Backpacks A sturdy, well-designed backpack should be used to carry gear. Reflective material should be sewn onto the back of each backpack. Iron Horse Safety Specialties (800-323-5889, http://fabric.ironhorsesafety.com) sells red-orange reflective material for daytime visibility and reflective silver material for nighttime reflectivity. On serious jungle treks, porters are often present. This frees expedition members to carry much lighter loads.

Backpack for Porter An internal-frame backpack of 3000 to 4000 cubic inch capacity is a good size. It should have external pockets for quick access to liter-sized water bottles. Indigenous peoples are accustomed to carrying packs and hauling loads with a strap, known as a tumpline, slung over the forehead or chest. Many natives, including Amazonian Indians, dislike using the shoulder straps that come as standard equipment on backpacks. Given enough straps, almost any native porter can quickly rig a satisfactory tumpline on a backpack. If you don’t have extra straps, tribesmen reared in the tropical forest will strip bark from saplings and fashion an adequate tumpline in minutes (Fig. 37-5).

Personal Pack A daypack of 1200 to 2000 cubic inch capacity is useful for carrying a camera, snack food, and other gear that must be kept handy. A waterproof liner will keep perspiration from wicking into the bag and wetting everything inside. The pack should have two outside pockets for quick access to liter-sized water bottles.

Pack for River Trips A durable, waterproof “dry” bag, used by river runners, is worth considering, especially if the trip will involve spending

days or weeks at a time in dugout canoes or rubber rafts. Most of these packs, however, cannot stand up to the demands of long-distance overland trekking. The straps tend to be uncomfortable and frequently rip out on the trail.

Other Useful Items Antifogging Solution for Eyeglasses Antifog solution, available from dive shops, reduces humidityinduced fogging of glasses.

Batteries Alkaline batteries should be brought from home. Batteries purchased in Third World nations do not last long and often leak.

Binoculars The traveler who is an avid bird watcher or enjoys watching butterflies or seeking out orchids high on distant limbs will want to pack a pair of binoculars that are lightweight, compact, shockproof, and waterproof or water resistant.

Camera Equipment Older-style cameras with mechanical shutters are reliable in regions of high humidity. Film with an ISO of 200 is ideal for use in low-light conditions of the jungle and much preferred over slower film. Water-resistant point-and-shoot and highperformance, professional digital cameras are now available.

Camera Case or Bag Hard-bodied Pelican cases are waterproof and virtually indestructible. The silver-gray color cuts down on heat absorption and is preferred in hot climates. The cases are ideal for rafting or canoe trips but bulky for trekking. On the trail, waterproof “dry” bags protect equipment.

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Camp Soap

Insect Repellent

A biodegradable soap should be used. The soap Campsuds works in hot, cold, fresh, or salt water and cleans dishes, clothing, hair, and skin.

To repel mosquitoes, flies, ticks, chiggers, fleas, and gnats (but not no-see-ums), insect repellent should contain 15% to 30% N,N-diethyl-meta-toluamide (DEET). Formulations (often called “jungle juice”) should not contain higher than 30% DEET, because they may pose health hazards (see Chapter 41). Technique is critical when applying insect repellent. Before dressing, the person should spray the ankles, lower legs, and waist. If clothing has not been pretreated with permethrin (see later), then after the socks are put on, a band of repellent should be sprayed around the top; a band should also be sprayed around both pant legs to midcalf. A light spray to the shirt, front and back, may also help. The hands should be sprayed, rubbed vigorously, and run through the hair. Some repellent should be dabbed on the face, neck, and ears, carefully avoiding the eyes; contact lens wearers should be especially vigilant when applying insect repellent. No-see-ums, which are tiny gnats that abound throughout the tropics of the Americas, are the most common source of insect annoyance in many regions. They are active at sunset and attack humans emerging from jungle streams. No-see-ums cannot bite through even the thinnest cloth and are usually inhibited by Skin So Soft (SSS, Avon), which appears to have a slight chemical repellent effect, but more likely works by drowning the tiny gnats in oil. SSS is not effective against ticks, fleas, flies, and chiggers and offers little protection against mosquitoes. SSS should be applied liberally and often to the wrists, knuckles, bare ankles, face, ears, and scalp. Men with full beards seem to be especially troubled by tiny gnats and may benefit by applying small amounts of SSS to the beard area. Permethrin kills or stuns insects that land on clothing that has been impregnated with this product. Permethrin is safe, is highly effective, and persists even after extensive washing of garments (see Chapter 77). It is effective against insects when used on mosquito netting, even when the netting has sizable holes and tears. Permethrin can be purchased as a solution for application from a pump spray.

Candles Electricity tends to fail at unpredictable times in small towns and even in larger cities in Third World countries. Travelers should carry dripless candles. Spring-loaded candle lanterns should be avoided because they give off an anemic light, gum up, get crushed or broken, and basically waste space in the pack.

Cup and Plate A large Lexan polycarbonate cup is unbreakable, does not retain taste or odor, and serves the role of cup, bowl, and plate. Travelers who want an actual plate should buy one made of indestructible Melamine.

Duct Tape High-quality duct tape, such as Duck brand, is excellent for protecting existing blisters and for preventing blisters from developing on areas prone to blister formation when applied before trekking. Although a number of products are marketed to prevent blister formation and protect skin once blisters have formed, in my experience nothing beats duct tape.

Ear Plugs Travel in the tropics often involves flying in incredibly loud helicopters, cargo planes, or short takeoff and landing (STOL) aircraft. Sponge ear plugs that roll up and fit in the ear canal offer inexpensive, effective protection against hearing damage.

Fishing Supplies For additional “food insurance” when traveling in extremely isolated regions, the jungle traveler should carry 75 feet of 20pound-test fishing line, a 12-inch steel leader with swivel, and a few size #4 hooks. Travel rods that break down for compact carrying and spin-cast reels should be considered for sport fishing or adding fresh meat to the daily provisions. Throughout the tropics, most species of fish find Rat-L-Trap lures, particularly the chrome and blue combination, irresistible. The hooks that come standard with Rat-L-Trap lures are not sturdy enough to withstand the hard mouth and powerful bite of tropical freshwater fish. Replace these hooks with 3× or 4× strong, size #4, treble hooks.

Laminated Map Accurate maps exist for most regions on Earth. From the best map available, travelers should laminate photocopied portions that are relevant to a particular itinerary (see “Rescue Strategies”).

Garbage Bags

Machete

Four 30-gallon capacity and four 13-gallon capacity large plastic garbage bags can hold clothes, bedding, and other items that must stay absolutely dry and can keep dirty boots isolated from clean items in the backpack.

A Collins-style machete (Fig. 37-6) is the single essential tool for jungle survival and for the many tasks in camp and on the trail that require steel with a sharp edge. Do not purchase a model with a hand guard. A hand guard serves only for protection against an opponent’s blade when used as a weapon in combat; it does not offer added protection when the machete is used as a cutting implement.23 It is hazardous to use a machete in the rain or when cutting wet grass because the weapon may fly out of the hand. Also, when cutting brush, the person often encounters sawgrass. The resulting skin lacerations, which are not noticed at first because sawgrass is razor sharp, may take a week or two to heal. Because of the risks involved, an experienced individual should be in charge of transporting and using the machete. For added safety, a machete should be carried in a sheath.

Headlamp Battery-operated headlamps offer hands-free convenience at night for reading or going to the latrine. The Petzl Tikka LED Headlamp weighs a mere 2.7 ounces (with batteries) and has a battery life of 24 hours at 21° C (70° F).

Inflatable Cushion or Pillow A small, self-inflating cushion made with a low-slip polyester fabric top and durable nylon bottom is recommended for sitting in a dugout canoe or aluminum boat.

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Spoon Knife-spoon-fork sets are unnecessary. A knife blade and a good tablespoon made of either Lexan polycarbonate or stainless steel are sufficient for eating.

Sport Sponge A camp towel, made of microporous material, is lightweight, compact, and superabsorbent; it replaces the cotton towel. With the Cascade Designs Pack Towel or similar brand, the body and even hair can be dried much more quickly than with a traditional towel.

Sunglasses

Figure 37-6. Collins style machete with sheath. (Photo courtesy of John Walden.)

Sunglasses should be polarized with full ultraviolet light protection. Many travelers prefer sunglasses with red-tinted lenses. Because red is the complement of green, these lenses make the jungle foliage stand out intensely and sharply, with enhanced contrast and depth of field. Retainers hold eyeglasses securely during vigorous activity.

Toilet Paper Matches or Cigarette Lighter Waterproof, windproof Hurricane Matches light when damp and stay lit for several seconds, even in the strongest wind. Many jungle travelers prefer a butane cigarette lighter with a piezo ignition system.

Organizer Bags See-through organizer bags help reduce clutter and minimize the risk for misplacing small items.

Pen J. L. Darling Corp. (2614 Pacific Hwy. E., Tacoma, WA, 984241017, phone 253-922-5000, www.riteintherain.com) sells outdoor writing products, including “Rite in the Rain” shirtpocket field notebooks, travel journals, and all-weather pens that write upside down without pumping, underwater, over grease, and in hot and cold temperature extremes. These pens have an estimated shelf life of more than 100 years. The Fisher Space Pen Co. (711 Yucca St., Boulder City, NV 89005, phone 905-713-1163) sells all-weather pens.

Pocket Tool The Leatherman Super Tool is recommended for jungle travel and survival and features needle-nosed pliers and 12 locking implements.

Poly Bottles Essential gear includes two quart- or liter-sized wide-mouth water bottles made of high-density polyethylene or Lexan polycarbonate. A 2-ounce, heavy-duty poly bottle comes in handy for carrying a salt and pepper mixture to add flavor to boiled plantains and yucca. Nalgene products are legendary; whatever you put in a Nalgene bottle will stay there and not leak into your pack.

Razor or Battery-Operated Shaver Both men and women should carry lightweight disposable razors. Most men find that lightweight, AA battery-operated shavers give two shaves a day for up to 2 weeks before requiring a change of batteries.

American toilet paper is much softer than that purchased in Third World countries. The traveler should never wipe with jungle leaves.

Umbrella A collapsible umbrella is useful in tropical cities and in remote villages when walking from hut to hut. It also offers excellent protection from the sun on canoe or raft trips. The umbrella should be reflective silver, not heat-absorbing black.

Whistle A high-quality plastic whistle can be used to signal in case someone strays off the path.

Zipper-Lock Bags Heavy-duty zipper-lock freezer bags are excellent for organizing medicines, toiletries, and other small objects. Bring five each of the gallon, quart, and pint sizes.


COPING WITH THE JUNGLE ENVIRONMENT

A visit to the rainforests of the New World tropics can be either a sublime experience or a hellish ordeal.17

Wetness The superhumid lowland rainforest receives up to 400 inches of rain a year. In contrast, West Virginia averages about 40 inches per year. In the higher-elevation cloud forest, dense cloud cover throughout the year is accompanied by constant mist or drizzle. In such heat and high humidity, people become mentally fatigued as a result of being constantly wet. Fortunately, travelers can use basic strategies for coping with the physical and psychological burden of wetness. Dryness while trekking or working during the day is not a requisite for physical or mental health. Wetness does not equate with illness, significant discomfort, or dampened spirits. People can tolerate being wet throughout much of the day if they know that they have a dry change of clothes to wear in camp and that they will be dry at night. In addition to the psychological ben-

Chapter 37: Jungle Travel and Survival efits, being dry at night means that maceration is less likely to develop in intertriginous areas. Bedding and clothing can be protected from moisture by careful wrapping in plastic garbage bags. Despite all efforts, however, certain “dry” items eventually become damp or accidentally soaked. Wet articles should be spread out on shrubs and bushes. They will dry within 2 hours in full sun. Myiasis caused by the tumbu fly, Cordylobia anthropophaga, of subSaharan Africa can be avoided by hanging clothing to dry in bright sunlight, never on the ground. Clothing dried over a wood fire absorbs odors that do not wash out.

Health Issues Health Risks The subject of the tropics causes many people to think about tropical diseases, such as filariasis, and animals, such as the candirú (see later discussion). Malaria, hepatitis, and motor vehicle accidents are the three leading health problems in most tropical regions. Tropical travelers who venture off the path may be exposed to bodily harm and serious diseases, such as leishmaniasis, onchocerciasis, Chagas’ disease (in the Americas), and sleeping sickness (in sub-Saharan Africa). Close contact with many indigenous populations of Amazonia increases the likelihood of infestation with scabies and head lice. Bouts of diarrhea or other annoyances will likely occur, regardless of the extent of precautions taken, but death is unlikely.

Duration of Travel and Emotional Response

Cashel and colleagues6 examined the mood pattern of participants in eight separate 9-day wilderness expeditions conducted over 4 years and noted a high level of confusion, fatigue, anger, depression, and tension on day 4. After 2 to 3 weeks of travel in remote areas, the general health of expedition participants deteriorates as a result of insect bites, falls, and noxious plants. Inexperienced trekkers may quickly tire of unfamiliar food and miss usual comforts. Experienced leaders therefore prefer to limit expeditions to not more than 3 weeks.

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Heat cramps, often severe, tend to occur when large amounts of water are ingested without adequate salt replacement. Oral rehydration solution (ORS) products, available in premeasured powder form, added to a liter of disinfected water, provide an ideal balance for replacing lost electrolytes. The first liter of disinfected water (noted previously) consumed before trekking should include a packet of ORS. After especially strenuous days, trekkers should drink an additional 1/2 packet of ORS. The rice-based ORS product CeraLyte has a high absorption rate and reduces ongoing fluid loss in diarrheal illness (see Chapter 62). In the United States, rice-based oral rehydration therapy packets may be obtained from Cera Products (www. ceraproductsinc.com) and glucose-based ORS from Jianas Brothers (816-241-2880). To eliminate or reduce the chances of intensely painful leg cramps rousing you from sleep, always perform calf-stretching exercises before falling asleep. Sport beverages do not contain the ideal concentration of electrolytes found in ORS and are not recommended. Salt tablets are not recommended because they are gastric irritants.

Unexpected Isolation Various factors contribute to unexpected isolation in the jungle. These include inclement weather, mechanical problems, or political turmoil that shuts down public transportation. Many people respond with anger and irritability, which can be devastating to group dynamics. Travelers should accept the situation and use the additional time to appreciate the tropical forest, take photographs, or read paperback books. It helps to shift out of gear mentally and allow the intellectual machinery to idle. Nearly everyone has the experience of driving for hours and arriving at a destination with virtually no recollection of the trip. The same can be accomplished in the village setting, lying around on a hammock. The hours and days pass surprisingly quickly, akin to cruising in a sailboat with no engine. The person learns patience and develops an appreciation that the rhythms of nature are not governed by the ticking of a clock.

Camp Life

Preventing Heat-Related Illness

Shelter

The following guidelines may help prevent heat-related illness: 1. Before undertaking long-distance trekking in the tropics, acclimatize by spending at least 5 days in a hot, humid environment and engaging in moderate daily exercise. This acclimatization will be lost within a week if not maintained. 2. Avoid alcohol and certain drugs. Medications, such as βblockers, anticholinergics, and diuretics, increase the likelihood of heat-related illness and should be avoided if possible. 3. Wear ultra-lightweight, light-colored, and loose-fitting cotton clothing and a wide-brimmed hat. As previously noted in this chapter, shirts should always be made of cotton. Pants, however, may be made of cotton or synthetic fabrics such as nylon Supplex or Taslan. 4. Whenever possible, have a native porter carry all gear. 5. Maintain adequate hydration. Before setting off on the trail, drink a liter of disinfected water. A half hour later, drink a second liter. One hour after the second liter, drink a third, then consume about 1 L every 2 to 4 hours during strenuous trekking.

Natives rarely spend the night in makeshift shelters. It is usually best to use existing dwellings for a hammock or sleeping pad. Common courtesy governs placement inside the hut of a native. Travelers should ask about taboo spots before bedding down. When huts are not available for use, a tarpaulin provides satisfactory shelter from the rain. Rip-stop polyethylene tarps (8 × 10 feet) are lightweight and waterproof. Coated nylon tarps are also acceptable but must be sealed with a product such as Seam Grip. Figure 37-7 illustrates a typical method for erecting a tarp. First, a thick line is run 7 to 8 feet (2.1 to 2.4 m) off the ground between two trees and cinched tight. The long axis of the tarp is centered over the rope, and a rope attached to the middle grommet on each end is tied to the tree. The corner grommets are tied to available trees, bushes, or strong clumps of grass; a tie-down in the middle on each side is also helpful. The sides of the roof should be made high enough to enter and exit conveniently but not so high that driving rain can come in at an angle. Once the tarp is up, the hammock ropes are run through the sleeves of the mosquito net. Then the hammock is slung. The hammock should be suspended high enough that it will not sag

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Shingled leaves

Tarp

72

60



44

84

Figure 37-7. Construction of mosquito netting for use with a hammock: sleeve hole is 88 inches (2.2 m) in circumference; small hole is 18 inches (0.46 m) in circumference; smallest holes (for supporting sticks) are 4 inches (10 cm) in circumference.

to the ground during the night because it naturally sags under an adult’s weight. Next, the mosquito net is suspended. The ropes running from tree to tarp, from tree to mosquito net, and from tree to hammock should be sprayed with DEETcontaining insect repellent (or permethrin insecticide) to keep ants and other pests from using the ropes as trails. Finally, a few broad leaves (banana leaves or heliconia) folded at the spine are draped over the bare rope extending from the tree to the tarp to keep rain from running down the tarp and hammock ropes. Knowledge of two knots is needed for slinging a hammock. These knots always hold and always come undone quickly without jamming. The half hitch is used to tie the hammock to a horizontal beam, as follows (Fig. 37-8): 1. Pass the working end of the rope around the object to which it is to be secured. 2. Pass the working end of the rope around again without crossing over itself. 3. Bring the end over and around the standing part and through the loop that has just been created. You have completed a half hitch. 4. Make a second half hitch below the first half hitch. 5. Pull tight.

The camel hitch is used to tie the hammock to a vertical post, as follows (Fig. 37-9): 1. Make three turns around the vertical pole. 2. Bring the working end up and over the turns. 3. Make a turn at the top and pass the end back under itself. 4. Make a second turn at the top and pass the end back under itself. Weather conditions can change in minutes, and travelers must be prepared with adequate shelter. The use of a tent as shelter in the tropical rainforest is not recommended. Clearing a tent space is time consuming, and the stumps remaining from cutting saplings and bushes invariably perforate the floor. Air does not circulate; after a restless night sweltering in the tent, the traveler emerges tired and irritable.

Food Solitary travelers or small groups usually do not need to pack large amounts of food. Edibles are always available in areas inhabited by friendly natives. As a general rule, food is safe to eat if it is peeled, cooked, or boiled. Travelers in the tropics must be open to eating local food. Most creatures are edible, such as boiled caiman (alligator), cooked capybara (a 50-kg rodent), or roasted palm grubs

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2

3

4

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Figure 37-10. The palm grub is a favorite delicacy. (Photo courtesy of John Walden.)

Figure 37-8. Half hitch.

Figure 37-9. Camel hitch.

(larvae of Rhynchophorus). Raw palm grubs, up to 5 inches long, are tasty and a favorite of Amazonian Indians (Fig. 37-10). They are eaten by slashing open the thin integument with the thumbnail, extracting and discarding the intestinal tract, placing the opened skin to the mouth, and sucking out the turgid contents. In addition to palm grubs, more than 20 species of edible insects, including ants and termites, are collected year-round by

the people of Amazonia.12 Large hairy spiders, Theraphosa leblondi, 10 inches in diameter, are often roasted on an open fire. After the barbed hairs are singed off, the spiders are placed in the embers. They have a shrimplike taste. Indians of the Americas have perfected the art of smoking fish and meat so that they remain safe to eat for long periods. It is common to see huge hunks of tapir meat or slabs of 100-pound catfish resting on racks, coal black from the smoking process. Table 37-1 illustrates the diversity of wild game from 867 day hunts by members of the Waorani tribe of Ecuador.54 The Aguaruna and Huambisa of Peru conceptually recognize and classify as food nearly 500 species of animals.2 The tropics have an abundance of flora as food. The yardlong heart of palm is cool and delicious when eaten in its raw state or may be included in a soup spiced with tropical herbs. Familiar tropical fruits include papaya, mango, pineapple, and passion fruit (genus Passiflora). Many New World fruits have no name in English and generally have not found their way into the world market. These include chirimoya, guanabana, pitahayas, naranjilla, uchuva, tamarillo, zapote, sapotilla, and badea.30,33,50 The boiled fruit of the peach palm, Bactris gasipaes, is nutritious and flavorful. The banana and its cousin, the plantain, provide a large percentage of the total caloric intake of natives in the American and African tropics. Curiously, in many native villages, it is difficult to find the sweet, finger-length bananas and the common yellow bananas exported from tropical countries. The green plantain features prominently in the daily fare of inhabitants of the tropics. The plantain has little taste and is exceptionally dry. Yucca (manioc or cassava), Manihot esculenta, is a staple source of carbohydrate nutrition throughout the Americas and much of tropical Africa. The two kinds of yucca, “sweet” and “bitter,” are the same species but differ in their distribution and amount of a poisonous constituent, a cyanogenic glycoside, in the root.42 Sweet and bitter yucca cannot be easily distinguished; one must know which variety was planted. Sweet yucca, common in the eastern lowlands of the Andean countries of Colombia, Ecuador, and Peru, is eaten after the bark containing the toxic substance is peeled off and the root boiled. With bitter yucca, the poison is more concentrated and distributed throughout the root, so it must be extracted before consump-

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TABLE 37-1. Rank Order of Species by Total Weight RANK 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Gross weight

COMMON NAME White-lipped peccary Wooly monkey Collared peccary Howler monkey Tapir Salvin’s curassow Cuvier’s toucan Capuchin monkey Spix’s guan Blue-throated piping guan Brocket deer Capybara Paca Coati Great tinamou Spider monkey Saki Ivory-billed aracari Red squirrel Gray-winged trumpeter Agouti Golden-collared toucanet Tayra Squirrel monkey Speckled chachalaca Nocturnal curassow Cayman Mealy parrot Red-mantled tamarin Scarlet macaw Douracouli Titi Squirrel Acushi Yellow-ridged toucan

SPECIES NAME Tayassu pecan Lagothrix lagotricha Tayassu tajacu Alouatta seniculus Tapirus terrestris Mitu salvini Ramphastos cuvieri Cehus albifrons Penelope jacquacu Pipile pipile Mazama americana Hydrochoerus hydrochaeris Agouti paca Nasua nasua Tinamus major Ateles belzebuth Pithecia monachus Pteroglossus flavirostris Sciurus igniventris Psophia crepitans Dasyprocta fulignosa Selenidera reinwardtii Tayra barbara Saimiri sciurea Ortalis guttata Nothocrax urumutum Caiman sclerops Amazona farinosa Saguinus fascicollis Ara macao Aotus tirvirgatus Callicebus moloch Sciurus cocalis Myoprocta pratti Ramphastos culminatus Miscellaneous small birds (numerous species)

TOTAL WEIGHT (kg)* 4,940.1 3,873.5 2,740.6 2,197.4 1,314.4 610.9 414.4 400.8 301.7 261.8 253.4 226.5 194.8 130.6 116.5 110.1 100.0 86.1 82.9 66.5 47.5 30.4 27.3 23.7 21.6 20.4 20.0 19.6 18.7 18.2 17.6 17.2 15.4 11.1 11.0 29.3 18,781.1

PERCENTAGE OF GROSS WEIGHT 26 21 15 12 7 3 2 2 2 1 1 1 1 1

5

100

*Includes only those species whose total weight was more than 10 kg.

tion. Amerindians use an apparatus called the tipití (Fig. 37-11) to express the poisonous juice from the peeled and grated flour of manioc roots. Travelers in a large group should carry dried, packaged foods because the host village might not be able to provide sufficient foodstuffs or travelers might pass through isolated and uninhabited regions. Packaged foods should also be carried by travelers in regions where natives are unfriendly. Dried instant food needs only water to make a meal. A few selections should be tried before a large supply for field use is ordered. It is not necessary to add hot water to all packaged foods; adding disinfected, ambient-temperature water produces acceptable results for most foods. Drawbacks to prepackaged foods include expense, space, and disposing of the empty foil packages. I carry the following supplemental food items for 2- to 3week treks into remote but inhabited jungle regions: one 2ounce heavy-duty poly bottle filled with salt and pepper mixed half and half, a few pounds of rice, a tin of long-keeping butter

(or oil) for cooking the rice, a few tins of tuna or sardines packed in tropical hot sauce, and several PowerGel energy packets for trail snacks.

Potable Water Potable Aqua (tetraglycine hydroperiodide 16.7%) tablets are recommended for disinfecting water because they are easy to use and have proved effective in killing bacteria, viruses, and many parasite cysts (see Chapter 61). Potable Aqua is ineffective against Cryptosporidium. (Diarrheal illness due to Cryptosporidium species usually resolves without therapy in 10 to 14 days in immunologically healthy people.) Water filters are not recommended for purifying jungle water; they clog with silt and must be cleaned frequently. If a water filter is used, it should be fitted with a good prefilter to catch the excess silt.

Jungle Hazards The following hazards are common in the wilderness jungle setting or thought to be common. Other chapters provide

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Figure 37-11. The tipití expresses poisonous juice. (Photo courtesy William H. Crocker, Department of Anthropology, Smithsonian Institution.)

additional insights and viewpoints, particularly with respect to treatment.

Arthropods

Ants. The conga ant, Paraponera clavata, 1 to 11/2 inches long, is the terror of the American tropics. The bite of these large black ants can produce intense pain and fever for up to 24 hours, which accounts for the Spanish name veinte-cuatro (twenty-four). Fortunately, they are conspicuous because their large, shiny black bodies tend to stand out against foliage. Special caution is needed when ducking under or climbing over trees, where ants are often found. A conga bite requires strong pain medication and perhaps the injection of lidocaine at the bite site. Travelers should avoid touching trees and bushes. Many plants in the tropics provide a home and food for ants, which provide aggressive defense of the plants. Fire ants are common throughout the tropics and subtropics. Their bite causes discomfort but not excruciating pain. Characteristic sterile pustular lesions in crops often result from fire ant stings.

Chiggers. Chiggers, a form of mite, are a problem throughout equatorial regions. Whereas temperate-climate chiggers may cause mild discomfort for a few days, the tropical chigger sets up an inflammatory and allergic reaction that often persists for weeks. In the South American tropics, chiggers are found in grassy fields, such as jungle airstrips and yards around mission compounds. Walking through chigger-infested areas without protection could leave a person covered with chigger bites. After a few days, the victim begins to itch mildly. As the days pass, the itching intensifies and seems to come in waves. Prevention is the best treatment. Areas known to be infested with chiggers should be avoided when possible. Spraying shoes or boots and lower pant legs with repellent containing DEET is highly effective. Pretreatment of clothing with permethrin is recommended. Travelers in the American tropics should never walk through grassy areas in shorts. Jigger Flea. Tunga penetrans, the jigger flea or chigoe, originally found in South and Central America, has now spread to

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East and West Africa and India. The fertilized female flea enters the feet through cracks in the soles, between the toes, and around the toenails. The female swells to the size of a pea and may be readily identified as a white papule with a central pit, through which the female extrudes excrement and eggs. When eggs are ripe for release, intense itching causes scratching that helps release large numbers of flea eggs. Incomplete removal of the jigger frequently results in complications caused by secondary infection. A simple extraction technique virtually eliminates complications. Open the skin over the nest of eggs with a surgical blade. Fold back the flaps, remove the easily identified egg sac, and with tweezers, remove the head of the female flea, which can be seen once the egg sac has been removed. Wash the area with hydrogen peroxide.19

Fish

Myiasis. Myiasis (skin infestation by fly larvae) is common in many regions of sub-Saharan Africa (the tumbu fly, Cordylobia anthropophaga) and Central and South America (the human botfly, Dermatobia hominis). The victim finds an itchy swelling that slowly enlarges into a lesion with a single breathing pore from which bubbles emerge or from which drains slightly bloody fluid. Later, movement is felt under the skin as the developing larva wriggles around. Removing the larvae before they emerge on their own is generally advised. Surgical excision, however, should be undertaken with caution because accidental rupture of the larval tegument can lead to secondary infections. Various methods to close off the breathing pore so the larva will emerge on its own include application of bacon fat, meat, chewing gum, or petroleum jelly.

Electric Eel. The so-called electric eel (actually an eel-shaped fish) is encountered from Guatemala to the La Plata River in South America and is especially common in the Amazon region. A person can drown after being stunned by a jolt from this fish. Electric eels are said to prefer deep water. Inhabitants of regions heavily infested with eels report a slight tingling sensation when one is close. No practical way exists to prevent these shocks.

Scorpions and Spiders. Stinging scorpions and venomous spiders are common throughout the tropics and provide another reason to exercise caution before sitting down or placing a hand on logs, bushes, or the ground. The large, aggressive banana spider, Phoneutria nigriventer,49 causes excruciating pain, which may require local anesthetic infiltration of the bite site for relief. Venomous Moths, Butterflies, and Caterpillars. The larvae and adults of a number of moths (genus Hylesia) and butterflies bear venomous hairs that may cause skin eruptions. A rash may result from direct contact with the adults or larvae or by windblown hairs. Direct contact with certain Amazonian caterpillars can cause disabling pain. In the Amazon tropics, noxious smoke from burning garbage (e.g., plastic wrappers) may cause tree-dwelling caterpillars to loosen their hold on overhead branches and rain down on unwary campers. Treatment of Lepidoptera envenomation may require injection of lidocaine at the site of intense pain and administration of analgesics, antihistamines, and corticosteroids. Moth hairs may be removed with sticky lint removers used upon clothing. Wasp and Bee Stings. Sudden, intense pain from the sting of certain species of tropical wasps and bees can be so severe that it knocks the victim to the ground as though hit with an electric shock. Perfumes and brightly colored or flower-patterned clothing should be avoided.25 Bird watchers should not venture too close to the hanging nests of yellow-rumped caciques and oropendolas because wasps are invariably associated with these nests.

Stingray. The stingray, a flattened, cartilaginous cousin of the shark, may be encountered buried just beneath the surface of the bottom ooze in tropical rivers and streams throughout the Amazon Basin, Africa, and Indo-China. Rays inflict injury by lashing upward with the caudal appendage, driving one or more retroserrated venomous spines deep into the victim’s foot, ankle, or lower leg. This produces agonizing pain, often accompanied by headache, vomiting, and shortness of breath. After the initial phase of envenomation, tissue necrosis may develop. Wearing shoes or boots when wading in water does not always prevent a stingray from jabbing its barb into the foot or leg. Prevention lies in shuffling the feet along the bottom so that the ray will have enough warning to glide away safely.

Candirú. The candirú is a toothpick-sized parasitic catfish that inhabits Amazonian waters and may invade the urethra of urinating humans. Orifice penetration by the wily candirú can be prevented by wearing a tight bathing suit and not urinating underwater. Native methods of dislodging these fish from the urethra include drinking a tea made from the green fruit of the jagua tree, Genipa americana L. Oral vitamin C (2 to 5 g) may serve the same purpose.5 In his exhaustively referenced book entitled Candiru: Life and Legend of the Bloodsucking Catfishes, author Stephen Spotte downplays much of the lore regarding this little fish.44 Piranha. Although no human deaths have been documented, piranha have nipped off the fingertips of canoeists dangling their hands in the water. Attacks on humans by the speckled or darkbanded piranha, Serrasalmus maculatus, in dammed waters in Brazil have been linked to the fish’s behavior of defending its brood from perceived predators.20

Mammals Bats. Vampire bats are found throughout Mexico, Central America, and South America, especially in areas that have large cattle ranches. Sleeping humans are unaware of the presence of a feeding bat; the phlebotomy is painless. Both vampire and fruit bats carry rabies. Sleeping under mosquito netting prevents bat bites. The risk for rabies can be reduced by prophylactic human diploid cell rabies vaccine. Dogs. Most native groups keep dogs for hunting. Populations with a history of recent tribal warfare often keep packs of dogs close by as an early warning system. These semi-wild dogs should be treated with caution; threatening them may cause immediate attack because they are not easily intimidated. When approaching huts or villages, the traveler should allow porters to deal with the dogs. Dogs intent on biting often adopt particular behavior patterns. A dog protecting its territory crouches low, straightens its

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back and tail, emits a deep guttural growl, and stares fixedly at a specific part of the person’s anatomy. Such behavior indicates imminent attack and a sharp blow to the nose may be necessary. Freezing in place may prevent an attack, and direct eye contact should be avoided.

Jaguars. Jaguar attacks are rare. Recommendations are based on advice for avoiding a cougar attack. Increase your apparent size by raising your arms above the head and waving an object, such as a backpack or stick, or opening a jacket. Yell, shout, whistle, or speak loudly and forcefully in a low, deep tone of voice. Back away slowly; do not turn your back and run.11

Reptiles Snakes. Snakebites are rare; 450,000 hours of field work at sites in Costa Rican rainforests were documented without a single snakebite10 (see Chapters 48 and 49). Most poisonous snakes tend to blend into their surroundings, and non-natives rarely see them. The most effective protection is putting a jungle-reared guide in front on the trail. Natives almost always spot a poisonous snake and can quickly dispatch it. Snakes are often encountered along the shorelines of rivers and small streams. Particular caution is needed when hiking in such areas or when disembarking from a canoe or rubber raft. In the forest, the hiker should always step onto a log and then step away from it. The log should not be straddled; snakes often are encountered where the log makes contact with the jungle floor. Because many venomous snakes in the tropics are heat seeking and hunt at night, caution is needed. Anacondas (water boas) feature in the folklore of all native cultures in the regions of Amazonia where these enormous snakes (up to 9 m [30 feet] long) live. These nonpoisonous snakes kill by looping coils around prey and then tightening the coils, suffocating the victim. Anecdotal reports of anacondas attacking and swallowing humans, particularly children and women bathing at the edge of jungle streams, are unconfirmed. Alligators and Crocodiles. Although they appear torpid lying in the sun, alligators and especially crocodiles can move amazingly fast. Humans cannot outswim or outrun a charging crocodile. Bites should be treated with thorough cleaning of the wound, surgical débridement if necessary, tetanus prophylaxis, and an appropriate antibiotic. A study of the oral flora of 10 alligators captured in Louisiana revealed various aerobic and anaerobic organisms responsive to trimethoprim-sulfamethoxazole.15

Plants Armed or Spine-Bearing Plants. Spine-bearing trees abound in forested areas of the tropics. The peach palm (Bactris gasipaes), a tall, slender palm whose heart and fruit mesocarp are prized by natives, is found from Nicaragua to Bolivia. The trunk of this tree is ringed with needle-sharp spines (Fig. 37-12). Peach palms often grow alongside trails. Contact with this palm can result in penetration of spines deep into the flesh. Spines that enter a joint space may require surgical extraction. Secondary infection and inflammation often occur. Chicha. Throughout much of Latin America, particularly in the Andean countries, a beerlike beverage known as chicha is con-

Figure 37-12. Needle-sharp spines ring the peach palm. (Photo courtesy of John Walden.)

sumed. Fermentation is initiated by masticating maize, cassava, plantain, or the fruit of the peach palm. Salivary enzymes hydrolyze the starch to sugar, resulting in a beer of 2% to 4% alcohol content. Some traditional populations consume copious amounts of chicha: the average daily intake among men of the Shuar and Achuar tribes of Ecuador and Peru is 2 to 3 gallons; for women, 1 to 2 gallons. From a health and safety standpoint, and in the social context, there are several aspects to chicha consumption that give pause. In addition to aesthetic considerations arising from its origin by way of human spit, the starchy substrate used for preparing chicha is often kneaded by unwashed handsa ready source of pathogens transmitted by the fecal–oral route. Although natives accustomed to daily chicha consumption seem to be unaffected with alcohol-related instability on the trail, the non-native jungle traveler will almost certainly experience problems maintaining balance, particularly when crossing single-log bridges, if excess chicha is consumed before or during trekking. Because chicha consumption is such a significant element in the social fabric of many tribes, to refuse to partake of the beverage can be a social gaffe. I have found it acceptable to inform my hosts, in a joking manner, I cannot trek and drink chicha throughout the day because “I stagger and fall off logs,” but that I will join in the evening rounds of ritual drinking. Eye contact with a woman who is serving chicha is a cultural signal to initiate a sexual encounter among the Jivaroan tribes of Ecuador and Peru. To avoid misunderstanding, hold the chichi bowl in the outstretched hand with the head turned to face slightly to one side or downward.

Sawgrass. In many regions of the tropics, sawgrass is an everpresent nuisance. The scalpel-like blades of this grass can slice into exposed skin. Even when treated with antibiotic ointment, the lacerations often take 1 to 2 weeks to heal. Hikers should avoid sawgrass; special care is needed when working with a machete.

Hallucinogenic Plants Hallucinogens permeate nearly every aspect of life in primitive societies. They play roles in health and sickness, peace and war, home life and travel, hunting and

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agriculture; they affect relations among individuals, villages and tribes. They are believed to influence life before birth and after death.39 To ignore the ubiquitous use of psychoactive drugs among jungle dwelling tribesmen throughout Central and South America is to deny a key element in understanding the rich and complex weave of Amerindian life. Powerful drugs, such as ayahuasca (Banisteriopsis), brugmansia, the virola snuffs, and yopo (Anadenanthera peregrina), are used by shamans and individuals seeking the truth through visions and a supernatural experience.

Ayahuasca. Also known as caapi, natema, pinde, and yaje, this woody vine (Banisteriopsis caapi) is found throughout western Amazonia in Colombia, Ecuador, Peru, Bolivia, and Brazil. The term ayahuasca derives from the Quechua language and has been translated as “vine of the soul.” The hallucinogenic activity derives primarily from harmine, the major β-carboline alkaloid in the plant. Indigenous peoples use additives (leaves of the shrub Psychotria and a forest liana Diplopteris cabrerana) to prolong and strengthen the intoxication. In addition to experiencing vivid visual hallucinations, users often report a distinct sense of clairvoyance. Adverse effects of ayahuasca ingestion include nausea, dizziness, and vomiting. For some users, the visual hallucinations are intense and disturbing. Brugmansia. Commonly known as borrachero, floripondio, huacacachu, or toá, the lovely, large bell-shaped flowers of brugmansia are encountered throughout the Andean foothills of western Amazonia. Despite their beauty, these are among the most powerful and dangerous of plant hallucinogens. The leaves and seeds of these bushy plants contain tropane alkaloids, including scopolamine, hyoscyamine, atropine, and secondary alkaloids.41 The effects on the user tend to be highly unpleas-

ant to the degree that those who partake of brugmansia often must be restrained.

Virolas. Known as epena, nyakwana, and yakee among indigenous populations of northwestern Amazonia, these hallucinogenic snuffs are made from the blood-red resin of the inner bark of trees (Virola species). The narcotic effect is due to tryptamine alkaloids. The drug acts rapidly. The excitement phase is followed by lack of coordination, copious nasal discharge, and vomiting. A curious effect of ingesting virola snuff is macropsia, in which objects, including hallucinatory spirits (known as hekulas among the Yanomami Indians of Venezuela and Brazil), appear greatly enlarged. Yopo. Seeds of Anadenanthera peregrine, a South American tree of the bean family Leguminosae, are used to prepare this tryptamine-containing hallucinogenic snuff. Employed by Indians in the Orinoco Basin region of Amazonas State, Venezuela, and adjacent regions of northernmost Brazil, yopo is inhaled to communicate with spirits during the phase of intoxication. In preparation, seeds are removed from the distinctive dangling pods and, after being moistened, rolled into a paste that is roasted over a fire and hardened for later use. The dried paste is pulverized and the resulting powder mixed with lime from snail shells or ashes from certain plants. The narcotic is blasted into the nostril through a long tube with the help of an assistant (Fig. 37-13). The user experiences immediate effects, including muscular twitching, nausea, profuse nasal secretions, and visual hallucinations.32 As in the case of virola snuffs, an abnormal exaggeration of the size of objects is common.39 Detailed discussions of additional New World hallucinogens, as well as African and Asian hallucinogens used by jungle dwelling tribesmen, are found in the references listed on the accompanying CD-ROM.39–42

Figure 37-13. Hallucinogen is administered through a long tube. (Photo courtesy of John Walden.)

Chapter 37: Jungle Travel and Survival Should travelers partake of hallucinogens used by tribesmen? Some argue, with a certain validity, that outsiders cannot possibly acquire insight into the Amerindian’s sense of the cosmos without ingesting their mind-altering drugs, and so make the case for limited use by anthropologists and others who plan to live and work closely with tribal populations for prolonged periods. Although none of the hallucinogens discussed in this chapter are known to be addictive, “recreational” use could, in the author’s opinion, have significant adverse consequences for certain individuals, including a lingering blurring of the sense of reality. So, I recommend that these powerful intoxicants be avoided.49

Miscellaneous Hazards Poison-Dart Frogs Poison-dart frogs are tiny, brilliantly colored species of the genus Dendrobates. They are encountered in Central America and Northern South America (Fig. 37-14). Phyllobates terribilis secretes a toxin from its skin so powerful that a lethal dose could be absorbed if enough secretion entered an open wound. It is wise to avoid all contact with brilliantly colored frogs, caterpillars, and snakes.

Falling Trees Tropical trees do not have deep roots and often fall in relatively modest winds. In many regions of the world, risk for snakebite is significantly lower than the risk for injury or death from falling trees. In the forest, hammocks should be slung away from large trees. Travelers setting up camp should always look up at the branches of any trees near camp; although the base of the tree may appear sound, higher areas may be rotted.

Fording Rivers The hiker should never attempt to cross a fast-flowing or deep river with a pack on his back. Regaining footing in a rapidly moving current can be difficult. Unless experienced in crossing such streams, the traveler should take the hand of a native guide or porter.

Figure 37-14. Poison-dart frog. (Photo courtesy of John Walden.)

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Log Bridges On frequently used trails, natives generally place a single log across creeks, ravines, and swampy areas. These log bridges may be up to 20 feet high and 75 feet long. Good balance is essential. Because a backpack impairs balance, a porter should carry it across.

Mercury Contamination Travelers to the Amazon Basin should be aware of the serious, widespread contamination of waterways by mercury that gold miners (garimpeiros) use to process their ore. Although most manufacturers of potable water treatment and filtration systems do not specifically claim to remove mercury, any activated carbon system should reduce the risk. Pres 2 Pure makes a line of filters claimed to remove mercury. Travelers should exercise caution in choosing rivulets as a source of potable water in areas where mercury contamination is known or suspected.

Rising Rivers Streams, particularly narrow ones bounded by vertical banks, can rise 20 feet in a few hours as a result of intense rains. Camp should not be set up on an island or beach in a small canyon during the rainy season. A cloudburst in the headwaters can send a wall of water rushing downstream, even though it may be a clear, moonlit night at the campsite.

Traveling with Children in the Tropics The following guidelines should be considered when trekking with children in the tropical forest: 1. Do not attempt a daylong hike. Unlike indigenous children, visitors cannot hike all day in the humid tropical forest. Preadolescents should hike only 1 to 2 hours; children aged 12 to 16 years can hike 2 to 3 hours. Do not subject a child to jungle trail conditions unless the child has had extensive experience hiking in temperate climates. 2. Do not attempt difficult or dangerous trails. 3. Avoid trekking during the rainy season. 4. Keep the child well hydrated. 5. Provide proper footwear (running or hiking sneaker-type shoes or boots with an adequate tread). Avoid leather boots. 6. Keep the child ahead of you and behind a native guide. Children should not be out of sight on the trail. 7. When wading across rivers, have an adult native guide hold the child’s hand. 8. Always have children wear a properly sized life vest while rafting, taking canoe trips, or crossing deep, swift, or wide rivers. 9. Do not allow a child to carry any equipment in a daypack other than two liter-sized bottles of drinking water. 10. Ensure that routine vaccinations are up to date. Special vaccinations, such as yellow fever and typhoid, should be considered for certain jungle areas. Hepatitis A vaccine is recommended. Antimalarials are indicated. Any child who plans to visit the tropics should be a strong swimmer. Many natives begin swimming in infancy and are accustomed to deep or rapidly flowing water that would be extremely hazardous to visiting children. Swimming holes are often located in the swift-flowing outer loop of jungle rivers, where depths may reach 6 feet or more within a yard of the shoreline.

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SURVIVAL Every year, inexperienced people enter the jungle and become lost. After a person ventures only a mere few yards into the forest, especially jungle that has been cleared and is now a tangle of secondary growth, everything begins to look the same. To avoid becoming lost, travelers should always have an experienced guide when traversing unfamiliar territory. Tribal peoples of the world’s tropical forests have an uncanny ability to find their way and arrive at the desired destination, even after days of travel. They can always find food and water and, if necessary, rapidly construct a shelter or weapon. Occasionally, travelers are left behind on the trail by indigenous guides. Unintentional desertion occurs when trekkers hire natives who have had no experience with neophytes. Realizing that their charges cannot keep up on the trail, the guides run ahead and sit down to rest, not knowing that others cannot navigate the trail alone. Travelers who want to avoid being left behind on the trail should hire a guide who is experienced in traveling with non-natives. Suitable guides and porters can usually be identified with the help of a village leader, local school teacher, village health worker, missionary, or anthropologist.

Rescue Strategies For individuals in a jungle survival situation, lifesaving items include a large-scale map, Global Positioning System (GPS) unit, some form of electronic voice communication, and machete. Topographic maps are available from numerous international and national mapping agencies. Satellite images with extraordinary resolution are available from Space Imaging (phone, 800-232-9037; www.spaceimaging.com) or the U.S. Geological Survey (Eros Data Center 47914, 252nd St., Sioux Falls, SD 57198-0001; phone, 800-252-4547; http://edcwww.cr.usgs. gov). Small, lightweight GPS units display precise latitude, longitude, and altitude. Such information is extremely useful for navigation and for communicating one’s location to rescue aircraft. Newer units quickly lock onto satellites and are more likely to work under the jungle canopy. Trekkers contemplating an expedition into largely uninhabited and unexplored regions should consider buying a compact personal locator beacon (PLB), such as those made by McMurdo Pains Wessex Inc. (www.mcmpw.com). These 406MHz EPIRB units offer a reliable method of alerting various rescue services through a global satellite system. These units should be activated only in a true emergency when lives are at risk. Hand-held satellite phones are available for worldwide communication. Although currently expensive to purchase and operate, their potential to provide rescuers with precise GPS location makes these lightweight phones worthy of serious consideration for inclusion for wilderness travel, especially on expeditions into areas of extreme isolation. The Brunton SOLARPORT portable solar panel is lightweight and allows the expeditioner to charge electronics, such as GPS units or digital cameras. Lightweight, hand-held, very-high-frequency (VHF) aircraft transceivers are excellent for emergency communications. Visitors to remote areas should know the radio frequencies used by rescue aircraft. VHF transceivers are line-of-sight instruments

and thus are most useful when aircraft are overhead without objects, such as trees or mountains, between the hand-held unit and the aircraft. In many regions of the world, the Mission Aviation Fellowship (MAF) provides air service to remote airstrips in small villages. If assistance is needed, a hand-held radio transmitter can be used to call an MAF STOL aircraft. Bush pilots appreciate having information on the condition of seldom-used airstrips. A crude but acceptable device can be constructed to measure airstrip hardness (Fig. 37-15). Cut a pole exactly 2 inches in diameter and about 6 feet long. Starting exactly 6 inches from one end, taper that end to a point. Lash a cross-member on the pole, and have a person weighing about 170 pounds stand with assistance on the cross-member. Make a map of the strip, noting the depth to which the pointed end of the pole sinks into the ground at several dozen sites. Communicate this information to the pilot by radio. If the pole goes in only 2 inches in most areas, the strip is considered ideal; 2 to 4 inches is marginal; penetration beyond 4 inches indicates that the airstrip is unsuitable for landing and takeoff. If rescue is not feasible, the traveler should continually move downstream at a fast pace. Inhabited areas usually have a trail running alongside a stream. The trail may veer away from the stream where natives have cut a path to connect two villages. Marking the trail every 10 yards with a machete makes it easier to return to the starting point. To avoid confusion, the traveler should mark trees only on one side of the trail. Recall will be increased by audibly describing the surrounding topography as you hike down the trail. Where human paths are in frequent use, identifying a trail is fairly easy. Seldom-used trails or any trail traversed during times of optimal plant growth may be extremely difficult for the nonnative to identify and follow. Even under adverse circumstances, however, there are clues to trail identification. Paradoxically, concentrating only on the actual foot path will almost certainly cause you to lose sight of the trail. Think of the jungle trail not as a track on the ground but as the intestinal lumen of “some gigantic leafy creature,”21 with vertical margins, often an overhead horizontal boundary, and sometimes a visible path beneath the feet. Diagonally sliced saplings or neatly severed branches indicate someone has used a machete. There is a particular reflectivity off the ground where humans have trod; this reflectivity is the best way to follow a trail at night. These trail-finding clues are often so subtle that you may sense the trail rather than see it. Game trails meander and are narrower than human trails. In the jungle setting, navigation with a compass for a distance of more than 200 yards is fraught with hazard. Travelers should not attempt to cut overland if lost, inexperienced, or on their own, unless a significant landmark is visible or sounds of humans or domesticated animals, indicating a settlement, are clearly heard. A raft may be constructed by lashing logs together with rope or tough, pliable jungle vines. Balsa trees (Ochroma pyramidale), encountered throughout much of Amazonia, make the best rafts. Balsa is often found growing alongside rivers and has the following characteristics: tall, columnar trunk with branches and leaves bunched at the top, which gives the tree a “skinny” look; beige or gray-beige trunk; bark that is smooth but tends to flake, giving it a mottled appearance; and broadly heartshaped, more or less three-lobed leaves. The key feature of balsa wood is its remarkably light weight. Bamboo also can be used to construct a first-class raft.

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Figure 37-15. A, Young man sharpening a stick to a point.B, Lashing a cross-member to a pole.C, Standing on the pole to take measurements of the depth of penetration into the airstrip.(Photo courtesy of John Walden.)

A log flotation device may be constructed by tying together two balsa logs or other lightweight wood placed 2 feet apart45 (Fig. 37-16). A “brush” raft may be made by placing buoyant vegetation within clothing or a poncho. Dry leaf litter (“duff”) or plants such as water hyacinth may be used.45

Food Food is readily available in inhabited regions. Even abandoned villages yield enough fruit and vegetables on which to survive. Throughout the tropical world, bananas and the large plantain “cooking banana” are ubiquitous. Root crops, such as taro, yams, and yucca, should be sought. Yucca roots should be shredded or pounded and then boiled to release their toxic compounds. As an extra precaution, the wet pulp should be flattened into a “pancake” and cooked on a grate to eliminate any remaining volatile hydrogen cyanide gas. All land crabs, mammals, birds, freshwater fish, turtles, snakes, and lizards are edible, but should be cooked first to eliminate parasites. It is virtually impossible to kill game without firearms. In inexperienced hands, traps and snares are not effective. Much better results are obtained from fishing.

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Edibility Test In a jungle survival situation, the goal is to get out as quickly as possible. In the rare circumstance in which the victim cannot recognize any familiar edible plant; has been unable to capture minnows, crayfish, and insects; and, for whatever reason, is unable to walk out of the jungle or expect prompt rescue, the following abbreviated version of the Universal Edibility Test recommended by the U.S. Army46 and the SAS Survival Guide53 may be used to test an unknown plant:

B Figure 37-16. Log flotation device. A, Two lightweight logs are tied together. B, Device in action.

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Caveats: 1. Never eat mushrooms. 2. Avoid unknown plants that have: • Milky or discolored sap • Beans or seeds inside pods hanging from trees • Bitter or soapy taste • Peach or “bitter almond” scent • Tiny barbs on the stems and leaves that could irritate the mouth and digestive tract Choose a plant that is abundant in the area. First, inspect the new plant, then crush a small portion; if it smells of bitter almonds or peaches, discard it. Check for skin irritation by squeezing some juice into the inner portion of the upper arm; if discomfort, a rash, or swelling occurs, discard the plant. Next, proceed through the following steps, waiting 15 seconds between each to see if there is any reaction and discard if discomfort is felt: • Place a small portion on the lips • Place a small portion in the corner of the mouth • Place a small portion on the tip of the tongue • Place a small portion under the tongue • Chew a small portion Swallow a small amount and wait 5 hours. Drink or eat nothing else during this period of waiting. If, after 5 hours have passed, there is no soreness of the mouth, excess belching, nausea, vomiting, or abdominal pains, the plant may be considered safe.

Water Water may be made safer by boiling or using chemical disinfectants, such as Potable Aqua tablets. Drinkable water may be found in lianas, often called “water vines,” throughout jungle regions. Vines that contain water are fairly easy to identify because they tend to resemble the “grapevines” of North American forests and have rough, scaly bark. These vines may be several inches thick and contain surprising amounts of clear water. Vines that do not contain drinkable water tend to have smoother bark and, when cut, exude sticky, milky liquid. Travelers should not drink from vines that contain milky, latexlike sap; this substance is poisonous. Maximal amounts of water are collected from water-bearing vines if the first cut is high on the vine and the second cut is lower on the vine near the ground (Fig. 37-17). When the water stops flowing from the cut section, cutting about 6 inches from the opposite end will start the flow again. Water may be trapped within sections of certain types of green bamboo. Bamboo that contains water makes a sloshing sound when shaken. Water also may be obtained from green bamboo stalks by bending a stalk over, tying it down, and cutting off the top. Water dripping from the severed tip can be collected in a container during the night45 (Fig. 37-18). Large amounts of water can be found in the voluminous natural cisterns formed by the cuplike interiors of epiphytes (air plants), such as bromeliads (Fig. 37-19). The water should be strained through a cloth.45 Water may be collected from a banana or plantain plant by cutting the plant about 1 foot above the ground and scooping out the center of the stump into a bowl shape. The hollow thus formed fills immediately with water. The first two fillings have a bitter taste and should be dipped out. The third and subsequent fillings are drinkable. A banana plant can furnish water in this fashion for several days45 (Fig. 37-20).

In coastal regions, unripe (green) coconuts provide adequate supplies of refreshing milk. The milk of mature coconuts has a laxative effect and should be avoided.

Shelter Abandoned, temporary shelters previously constructed by natives on hunting expeditions seem to attract particularly aggressive, large biting spiders and stinging ants. Also, venomous snakes may be attracted to rodents residing in these abandoned shelters. It is often preferable to take the extra time to set up a new camp than to risk encountering venomous insects, arachnids, and snakes. In an emergency, a proper shelter can be constructed using only plant materials. Figure 37-21 illustrates the basics of constructing a sleeping platform and lean-to. A shingled covering can be made quickly and easily from long, broad banana or heliconia leaves. Tropical palms provide a more substantial roof, but require more time and skill in construction. After selecting a suitable ground-hugging species or chopping down a slender tall palm (palm trees with spines often provide the best fronds), each frond is separated into halves by grasping it at the distal end, separating the leaves as though parting hair down the middle, and splitting the frond in two with a quick jerk (Fig. 37-22). The halves should be overlapped like shingles and secured to the roof framework. It is much easier to construct an adequate shelter using a tarpaulin (see “Camp Life”).

Fire In addition to boiling water for drinking and cooking food, fire lifts the spirits, warms the body on uncomfortably cool jungle nights, and can be used to signal rescue aircraft.

Tinder and Kindling

Small strips (1/8 × 2 × 4 inches) of rubber tire carried in a survival kit and a butane lighter are an excellent combination for starting a fire even in wet conditions. Tampons make a good fire-lighting aid. The silk-cotton or ceiba tree (Ceiba pentandra), found throughout the American, West African, and Southeast Asian tropics, produces balls of cottonlike fibers, known as kapok, which immediately catch fire and make an ideal tinder. The clothlike fibrous material at the base of palm fronds makes excellent tinder.

Bamboo Fire Saw If you don’t have matches or a butane lighter handy but do have access to bamboo, you can make a bamboo fire saw45,49 (Fig. 37-23). 1. With your machete, cut a 3- to 4-foot long section of bamboo. 2. Split the section the long way with the machete. One of the resulting long sections will be the “baseboard.” 3. Shorten one of the split sections to about 1 foot in length. This section will be the “running board.” 4. If kapok, palm fiber, or other suitable kindling is not available, with the machete blade, prepare tinder by scraping the outer sheath of a piece of bamboo. You need one large handful of scrapings. 5. Cut a narrow notch at 90 degrees on the outer (convex) side of the running board so that it just breaks through

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Figure 37-17. Water vine:first cut is high,second cut is low.

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to the inner wall. This will serve as a guide to slide the running board rapidly over the baseboard. 6. Fill the running board with a fluff ball of tinder. 7. Place a thin strip of wood or a strip of bamboo over the ball of tinder to hold it in place.

Cut vine low.

Drink.

8. Anchor the long section of bamboo (baseboard) with one end in the ground or against a rock or solid log and the other end wedged firmly against your abdomen. The sharp edges of the baseboard should be facing upward.

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Figure 37-18. Bamboo can be a source of water.

Figure 37-19. Water can be found in the natural cisterns in bromeliads. (Main photo courtesy John Walden; inset photo courtesy Erich Lehenbauer.)

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Figure 37-21. Sleeping platform. Figure 37-20. Water collected from a banana plant.

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Figure 37-22. Indian splitting a frond to make a covering for a lean-to (see text). (Photos courtesy of John Walden.)

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Figure 37-24. Bamboo container for heating water. (Redrawn from Walden JB: Jungle Travel and Survival. Guilford, CT, Lyons Press, 2001, p. 178.)

Running board Base board

Figure 37-23. Bamboo fire saw.(Redrawn from Walden JB:Jungle Travel and Survival.Guilford, CT, Lyons Press, 2001, p. 175.)

9. Holding carefully on to each end of the strip of wood that is keeping the tinder trapped inside the running board, rapidly and vigorously slide the running board up and down the baseboard with the groove against the sharp edge of the baseboard. 10. You will know that you are exerting effort sufficient to generate enough friction to ignite the tinder when you feel nearly exhausted, have worked up a sweat, and begin to entertain thoughts such as, “This just isn’t worth it.” 11. As soon as wisps of smoke begin to billow up from the tinder, gently blow upon the tinder until it bursts into flame. 12. Add small pieces of kindling and avoid smothering the fire. Using this or any other friction method for making fire is hard work, but it can be done.

Figure 37-25. Palm spathe container. (Photo courtesy of Jon Willis.)

Bamboo Container Large diameter bamboo makes a great “pot” for heating water to a sufficient degree to cook items such as crawfish and minnows. To prepare a bamboo cooking pot, take a section of bamboo cut just past each end joint. Notch out an opening by making cuts at 45 degrees near each end, then run the machete blade between the notches and pop out the “plug.” Support each end of the bamboo pot on stakes or sturdy Y-branched sticks that have been driven into the ground (Fig. 37-24).

Palm Spathe Container If bamboo is not available to construct a container, a woody spathe (the durable, canoe-shaped structure that encloses flowers and fruits of palms) can be substituted. Support the spathe at each end over a low fire and fill the vessel with water. A palm spathe container will stay intact long enough to cook crawfish and minnows (Fig. 37-25).

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Psychology of Survival Travelers reared on movies and novels depicting the horrors of the Amazon may have irrational fears of being lost or stranded in the jungle. Visible daytime threats worsen with the onset of darkness, when perception becomes distorted. Travelers incapacitated by fear may throw away survival items or may flee from rescuers. Strategies that can increase travelers’ confidence in survival include the following: 1. Previous jungle experience. It is helpful to begin tropical excursions in the structured setting of small-group travel. Ecotours, particularly in Costa Rica and Ecuador, offer a combination of rainforest trekking and cross-cultural experience. 2. Survival manuals. Military experts and others provide insights from decades of experience.45,46 3. Information on the tropical rainforest. Familiarity with exotic plants and animals lessens the likelihood of fear while increasing awareness of potential utility in a survival situation. The anthropologic literature is replete with firstperson accounts by anthropologists who have lived under trying circumstances with minimally contacted tribal populations throughout the tropics. 4. Classic accounts of survival against all odds, such as Alfred Lansing’s Endurance: Shackleton’s Incredible Voyage.27 5. Courses in wilderness-oriented skills. The National Outdoor Leadership School (NOLS, 307-332-5300, www.nols.edu) teaches wilderness-oriented skills and leadership in a core curriculum stressing safety and judgment, leadership and team work, outdoor skills, and environmental studies. Wilderness and outdoor safety courses (www.outdoorsafe.com) teach both the psychological and physiologic aspects of surviving a wilderness emergency. 6. Traveling with a Collins style machete, the one indispensable tool. A map, compass, GPS unit, and windproof lighter are other recommended items. 7. Taking stock. The traveler facing a wilderness crisis assesses a situation analytically and rationally before planning the course of action. Having survival skills is important; having the will to survive is essential.46

Cultural Factors Travelers who have the privilege of spending time with jungledwelling populations will find much to admire in the lives of indigenous peoples throughout the world. In some cultures, however, various facets of tribal life lend a discordant note and remind us that all cultures have their unpleasant aspects.

Infanticide In a few tribal societies, infanticide is still practiced. Often, the first or second of twins (depending on the customs of a particular tribe) and deformed newborns are killed. In some tribes, when the firstborn is a female instead of the more prized male, the decision may be made to kill the child at birth.

Intertribal Warfare, Revenge Killings, Homicide Although the rates may be significantly lower or slightly higher on a regional basis, the literature shows that those who observed certain indigenous populations during their first sustained contact with the outside world found a high background

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level of intertribal warfare, revenge killings, and homicide. Chagnon reported warfare-associated male mortality between 20% and 30% among the Yanomamö of Venezuela.7 Summarizing data for five generations among the Waorani, a linguistic isolate inhabiting the lowlands of eastern Ecuador, Larrick and associates28 concluded 42% of deaths were attributable to internal spearing raids and 16% were attributable to conflicts with the outside world. Various hypotheses have been advanced by anthropologists and others to explain the high death rates due to violence among Amerindians. If you disregard the theories of squabbling academicians and ask the Indians themselves, you will find preoccupation with warfare and homicide is attributed to revenge killings (vendettas), sexual disputes, and shamanism. Interestingly, after contact with the outside world, most groups rapidly abandon generations of warfare and violence. Influences, including Christian missions, school, and sports, in particular intervillage soccer tournaments, have been credited with transformation to more pacific lifestyles.37


SURVIVAL IN HOSTAGE SITUATIONS

The following overview of survival in hostage situations is based on material developed and used by the 2nd Battalion, U.S. Army John F. Kennedy Special Warfare Center and School, and draws heavily from an outline prepared by James Liffrig, MD, U.S. Army.29 Some areas of otherwise pleasant tropical rainforest are in regions of risk for hostage taking by terrorists, guerillas, or criminals whose motivation may be purely mercenary. Individuals traveling to such areas should have insight into the fundamentals of survival in hostage situations.

Prevention Since the late 1960s, hostage taking has been on the increase worldwide as a way of setting up a bargaining position to achieve an otherwise unattainable objective. At times, the individual taken is an innocent victim of circumstances who happened to be in the wrong place at the wrong time. Often, however, the individual has been chosen because he or she is an easy target. The Consular Affairs home page (http://travel.state.gov) of the U.S. State Department provides current travel warnings worldwide and detailed country-by-country profiles on safety and security matters in Consular Information Sheets.47 The likelihood of becoming a victim of hostage taking or kidnapping can be diminished by avoiding travel to areas of known high risk, such as Colombia and the frontier jungle regions of the five countries that share a border with Colombia. If one must travel to an area with a history of recent terrorist attacks or kidnapping, follow common sense precautions: 1. Have your affairs at home in order (current will, insurance documents, power of attorney, guardianship arrangements for minor children). 2. Register with the nearest U.S. embassy or consulate through the State Department’s travel registration website: (https://travelregistration.state.gov/ibrs/).48 3. Avoid obvious terrorist targets, such as places where Americans are known to congregate.

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4. Be sensitive to what you discuss with strangers, and that you may be overheard. 5. Vary routines, including appointments, travel times, and routes. 6. In a city, walk purposefully as if you know where you are going, even if you are lost. Indecision, hesitancy, and directionless movement attract thieves and kidnappers in the same way that thrashing surface movements attract sharks. 7. As much as possible, blend in.

4. 5. 6. 7. 8.

Categories of Hostage Takers Terrorist organizations are often stratified, with educated and dedicated idealists at the top and disillusioned, young, impressionable recruits from colleges or universities lower down in hierarchy. In some organizations, mentally ill persons and sociopaths recruited from prisons make up a nucleus of the more violent members of the group. Political and religious extremist hostage takers may represent the most danger to Americans because of the value of Americans as symbolic targets. Paramilitary/guerilla combatants often operate out of remote jungle regions and may cross in and out of one country to another along an unguarded border. Those who trek in such areas may become “targets of opportunity” by chance encounter with these individuals. Guerilla organizations in certain parts of the world engage in drug trafficking in order to obtain money, weapons, and equipment. Such organizations have increasingly turned to hostage taking for ransom as a source of fund raising.

Behavior at the Moment of Capture The initial moment of capture is dangerous because the captors are tense and may commit unintentional violence with the slightest provocation. 1. Do not reach into a coat or purse to produce a document unless so instructed. 2. Reassure your captors that you are not trying to escape. 3. If the terrorists use blindfolds, gags, or drugs at the time of abduction, keep in mind the fact that the terrorists want you alive. 4. If blindfolded, do not remove the blindfold because this could leave the terrorists no alternative but to kill you.

Hostage Rules of Behavior Always smile: I had learned that lesson years ago in the Congo, where the penalty for dropping your grin, even for an instant, in the face of nervous soldiers or tribesmen, was slow death with both legs hacked off above the knee with pangas.55 Hostage taking forces the terrorist or criminal into stereotyped responses. The more knowledge and understanding a hostage can have about his captors, the better he or she will be able to predict the hostage taker’s behavior and feel some degree of control. The conduct of the hostage can increase or decrease his chances for survival. 1. Smile. Be polite and respectful. 2. Be aware of the common “Good Guy/Bad Guy” interrogation technique. 3. Determine the area of particular sensitivity, such as politics or religion, of the hostage taker and avoid conversa-

9.

tion in these subjects. However, if terrorists want to talk about their cause, show an interest. Explain although you might not agree with your captors, you are interested in their point of view, emphasizing the latter point. Become an active listener. Small talk is better than no talk. Do not argue with captors. Make brief, casual eye contact during conversation; avoid prolonged eye contact. Do not refuse to eat unfamiliar local dishes just because they don’t look or smell appetizing. It is disrespectful to refuse to eat the food that the captors may themselves be eating. Adapt to, but do not adopt, the hostage taker’s value system (see “Stockholm Syndrome,” later.)

Stress Management in Captivity Long-term captivity often leads to exhaustion, lethargy, and depression. Oppose these feelings and try to maintain confidence. 1. Exercise. 2. Maintain sleep discipline and avoid sleeping too much. 3. Plan a schedule for the day and attempt to stick to it. 4. Keep a sense of humor.

Adjusting to Captivity The hostage must make every effort to adjust to captivity. 1. Do not focus on mistakes made up to the point of captivity. Focus on the positive. 2. A positive attitude will help sustain dignity. 3. Smiles are contagious; the hostage should wear one. 4. Fight boredom. Engage in creative mental and physical activities. 5. Avoid setting anticipated release dates or allowing captors to establish these types of milestones. 6. Remember that the longer a hostage is held in captivity, the greater his or her chances of release or rescue.

Stockholm Syndrome The Stockholm syndrome refers to stress-induced alteration of the hostage’s behavior such that the hostage aligns with the hostage taker. This phenomenon is thought to be an automatic, unconscious emotional response to the trauma of becoming a victim. It is not uncommon for hostages to transfer anger from the hostage takers to the society or situation that created the dilemma in which they are now victims. Individuals held in the grip of the Stockholm syndrome have been known to actively participate with the captor group in terrorist activities.

Escape Escape planning should begin at the onset of detention because escape may eventually prove to be a viable option. 1. Escape is considered a last resort but should be considered if conditions deteriorate to the point that the risks associated with escape seem less than the risks of remaining captive: torture, death of fellow detainees, or a credible threat of death. 2. In group hostage situations, detainees should organize and make every effort to establish and sustain communications with other hostages. 3. Terrorists often hold hostages in areas where the local population supports their cause. Do not assume locals are friendly, because they may return escapees to their captors.

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Rescue

Release

Statistically, most hostages who die are killed during rescue attempts. Hostages should, therefore, be mentally prepared for rescue attempts. 1. The first hostage execution, if known by the rescuers, increases the likelihood of a rescue attempt. 2. The hostage must be especially alert and cautious should he suspect that a rescue attempt is imminent or occurring. 3. At the first sign of an active rescue attempt, the hostage should drop immediately to the floor and avoid any sudden movement, especially with his hands. 4. From the rescuer’s point of view, everyone on the scene is a terrorist until proven otherwise. Therefore, do not attempt to assist the rescue forces because you may be mistaken for a terrorist. 5. Expect to be tied up or otherwise restrained by rescue forces until you can be positively identified. If you argue, you may be subdued.

Statistically, the odds favor the hostage being released. 1. The U.S. Government will not negotiate with terrorists. Our government will, however, work closely with the host government from the outset of a hostage-taking incident to encourage that government to exercise its responsibility under international law to protect all persons within its territories and bring about the safe release of hostages. 2. A number of factors can come into play (including ransom demands met by private efforts) so that the hostage is released by his or her captors. If an actual release has been arranged, pay close attention to the instructions the captors are giving when the release is taking place. Do not panic or attempt to run. The references for this chapter can be found on the accompanying DVD-ROM.

Desert Travel and Survival Edward J. Otten

This desert landscape is the indifference to our presence, our absence, our coming, our staying or our going. Whether we live or die is a matter of absolutely no concern to the desert. Edward Abbey, Desert Solitaire


THE DESERT ENVIRONMENT Deserts are land areas that receive less than 10 inches (25 cm) of rain, unevenly distributed throughout the year. A number of climatic processes produce desert areas. The most influential are the six cells of cold air currents that descend at the poles and near the Tropic of Cancer and Tropic of Capricorn. These air currents, driven by the sun and rotation of the earth, create areas of relatively warm, dry conditions. Many of the world’s deserts live in a “rain shadow,” an area to the leeward side of a mountain range that prevents the small amount of moisture that is present in the air to move over the mountains. As the air rises, the moisture cools and precipitates in the higher elevations. Therefore, the area in the “shadow” of the mountain range receives little moisture. The air that does descend is quite dry and adds to the evaporative effect. The Atlas Mountains shadow the Sahara, the Andes the Patagonian, the Great Dividing Range the Australian, and the Sierra Nevada and Cascades

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the Great Basin deserts. The amount of rainfall is not an absolute indicator of “dryness” because the rate of evaporation and timing of the rainfall must also be taken into consideration. The amount and type of vegetation, soil composition, altitude, average temperature, wind speed, and solar radiation all contribute to “dryness” and desert formation. Antarctica would be the world’s largest desert by the definition of less than 10 inches of rainfall annually, some areas of that continent having had no recorded rain in 30 years. There is a large amount of water present in the form of ice, but it is not available for use by plants. Antarctica has its own special survival problems not associated with precipitation and, for the purposes of desert survival, will not be considered here. In contrast to Antarctica stands the northern coast of Alaska, which receives less than 4 inches of rain annually yet nevertheless is quite wet because evaporation is so low there. Deserts are one type of environment on Earth that is increasing in total area, likely because of human as well as geologic factors. Overgrazing, destruction of forests, global warming, and other aspects of increased human population contribute to desertification. Currently about 15% of the land area of the earth is desert (30% if Antarctica is included) (Fig. 38-1; Table 38-1). Most of the earth’s deserts can be found between 30 degrees South and 30 degrees North latitude, making them hot

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Extremely arid Arid

Figure 38-1. Desert areas of the world. Many of these areas are growing.

TABLE 38-1. Deserts of the World NAME Western Sahara Great Erg Tanezrouft Libyan Fezzan Egyptian Sinai Niger Darfur Nubian Sahel Mauritania Somalia Kalahari Namib Andalusian Arabian Syrian Negev Taklimakan Thar Gobi Karakum Sonoran Death Valley Gran Desierto Mojave Great Basin Chihuahua Atacama Great Sandy Simpson Great Victoria

CONTINENT Africa Africa Africa Africa Africa Africa Africa Africa Africa Africa Africa Africa Africa Africa Africa Europe Asia Asia Asia Asia Asia Asia Asia N. America N. America N. America N. America N. America N. America S. America Australia Australia Australia

AREA (mi2) 103,000 151,460 57,900 463,320 212,806 254,828 23,550 179,270 170,000 162,800 1,930,500 278,000 226,700 100,390 36,300 102,700 888,030 200,000 4,630 125,000 82,625 501,930 266,410 120,000 5,700 119,690 25,096 189,190 200,000 77,220 139,000 115,830 223,660

FEATURES Dunes, mountains Dunes Rocky, mountains Rocky, dunes, oases Rocky, mountains Basin, plateau, oases Mountains Dunes, mountains, oases Mountains Rocky, dunes Steppe Dunes, plateaus Mountains, plateaus Dunes, savannah Dunes, plateaus Rocky, dunes Dunes, mountains Rocky, plateaus Plateaus, rocky Basin, dunes Dunes, cold Plateaus, rocky, cold Basin, plateaus, cold Mountains, alluvial Basin, mountains Basin, mountains Basin, mountains Basin, mountains Basin, mountains Mountains, rocky, cold Basin, dunes Dunes, rocky Dunes, alluvial

Chapter 38: Desert Travel and Survival as well as dry. These deserts include the Sahara, Arabian, Kalahari, Australian, Atacama, Thar, Namib, and southwest United States. About 50% of Africa is desert; the Sahara by itself is almost as large as the United States. About 8% of the United States, or 300,000 square miles, is desert. Most of the U.S. desert areas are adjacent to National Parks and Forests and are frequently visited, for example, the Grand Canyon, Big Bend, Arches, Zion, Organ Pipe, Joshua Tree, Great Basin, Saguaro, and Capital Reef. Beyond 40 degrees South and North latitude and at elevations over 10,000 feet are the “cold” deserts, which have wide swings in temperature, for example, the Patagonian, Turkestan, Gobi, and Takla Makan. The large temperature variations in desert regions are greater at higher elevations and latitudes, but are present in all deserts. Lack of vegetation, cloud cover, and ground-water surface allows 90% of solar radiation to reach the desert surface. By contrast, a forest may reflect 50% to 60% of the solar radiation, and its vegetation disperses the rest. At night, lack of cloud cover and vegetation allows almost 100% of the accumulated heat to escape, as opposed to only 50% from a humid climate. This explains why the desert temperature may reach 120° F (49° C) during the day and drop to 40° F (5° C) at night. Tropical rainforests may only reach 95° F (35° C) during the day, but at night the temperature only drops to 85° F (30° C). It might seem that the extreme desert climate would only allow for sparse life, but that is not the case (Fig. 38-2). Death Valley, one of the harshest environments in North America, where air temperatures have been recorded at 134° F (57° C), has 600 species of plants, 30 species of mammals, 25 species of reptiles, and 2 species of fishes. Oases are found in most deserts. They are isolated depressions usually fed by a constant source of water. Often, underground springs and wells supply moisture for plants and animals. Often one must dig to find water at the lowest point of the depression. Many named oases have supported camel caravans, allowing them to move from oasis to oasis and thus cross an otherwise impenetrable desert. Many ancient oases have wells hundreds of feet deep and because of overuse are gradually drying up. When the water is used up, the oasis disappears, along with its desert life. All desert flora and fauna have one guiding principle for survival, which is to conserve water. The ground surface of the desert has the highest temperature because of the direct effect of solar heat and wind. Therefore, during the hottest times of the day, most animals are either below the surface, in underground burrows, or above the surface in available vegetation, cacti, trees, or shrubs. Most animals forage from dusk till dawn when temperatures are cooler. Some mammals, such as kangaroo rats, never drink but obtain necessary water through plant seeds. Plants have evolved a number of survival skills to maintain water, including stomata that are closed during the day, and crassulacean acid metabolism (CAM) photosynthesis. The latter allows for accumulation of carbon compounds at night through the dark reaction. These compounds are converted to carbon dioxide during the day when the stomata are closed. Other adaptations include stem photosynthesis in plants without leaves, thick cuticles, water storage tissues, and widespread shallow root systems. Desert plants also have evolved a variety of defense mechanisms, such as production of toxic compounds that act as herbicides to other plants, and the formation of needles, spines, and thorns that dissuade browsing animals. Obviously, humans are not able to evolve these physiologic changes, but must rely on behavior, technology, and other

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Figure 38-2. Desert landscape. Note the physical features and abundant flora.

adaptations to mimic the methods used by indigenous desert dwellers.


PREPARATION All things being equal, preparation improves the likelihood of survival. However, things are never equal, so luck is probably the most important, albeit the most uncontrollable, factor. The controllable factors are mental and physical conditioning, clothing, survival kit adequacy, and survival skills. These may allow one to survive even in the most extreme conditions. Mental preparation is key to any survival situation. The “will to survive” has been shown to be the most important factor in the outcome of a number of situations. Knowledge of the terrain features, weather, animal and plant life, and potential hazards should all be studied before travel to a desert area. Not only does this increase one’s chances for survival, but it also enhances enjoyment of the desert environment. A number of recommended readings are included in the Suggested Readings section at the end of the chapter. Practical experience in finding water and food, navigation, and constructing shelters is more valuable

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than reading about it. Time spent in attending a course on survival in general or desert survival in particular may be invaluable if one is later in a true survival situation. Physical conditioning and acclimatization are as important for desert travel as for mountaineering. Desert travel is difficult under most circumstances. The terrain is rough and may include sand dunes, sharp loose rock, flash floods, steep grades, and hot surfaces. Lower-body conditioning helps prevent the ankle and knee injuries that can force a survival situation in a harsh climate. Acclimatization involves three well-described physiologic adaptations and may take 10 to 14 days. These are increase in the volume of sweat and number of active sweat glands, decrease in concentration of electrolytes in sweat, and sweating at lower body temperature. These can be induced before arriving in a hot climate by the use of a sauna or vigorous exercise to raise body temperature.

Making a burnoose

Clothing Clothing selection for desert travel is somewhat different than for most other wilderness activities. The less exposed skin, the better. Although cotton is not good for most cold, wet climates, it is useful in the desert. Light-colored clothing reflects sunlight and lowers skin temperature. Rip-stop cotton (cotton material with nylon threads latticed within it) is best because it resists rips that are common in the desert. It is light enough to allow heat to escape, does not have a clammy feeling in low humidity, and protects against some ultraviolet rays and blowing sand. If rip-stop cotton is not available, any tight weave cotton is adequate. Long sleeves and long pants are a must to protect against spines, thorns, splinters, and insects. More important, they protect against solar radiation that causes sunburn and increased body temperature, and they trap more cool air next to the skin. Sweat that is trapped decreases water loss through evaporation. Trousers can be tucked into the tops of socks to protect from insects; sleeves should be not be rolled up in order to minimize risk for sunburn and heat gain. Gaiters can be worn to protect lower legs and the inside of footwear from sand, rocks, and dust. In a survival situation, puttees (wraps that extend from the tops of the shoes to the knees, either over trousers or bare legs) can be made of strips of cloth, elastic bandages, or stockings to protect the lower legs. They can be incorporated into the socks and wrapped to above the knees in a fashion similar to gaiters. Because of the wide temperature swings, a pile jacket or sweater is necessary at night. Layering, just as in cold climates, is the best means of preserving body warmth. In a survival situation, any insulating material, such as seat cushions, newspapers, or dry grass, can be used to insulate whatever clothing is available. Although wind is more of a problem than rain, a Gore-Tex jacket is also recommended, especially for “cold” deserts. A wide-brim hat or kepi (a cap with a cloth extending from the back protecting the neck) is necessary to protect the head, face, neck, and ears. In a survival situation, an expedient head covering can be made from whatever material is at hand (Fig. 38-3). A cotton cravat, bandanna, or handkerchief can be used to keep the head and neck cool by soaking the material in water (if plenty of water is available; do not use precious drinking water) and then placing it on the head, followed by a hat. Alternatively, it can be wrapped around the neck and shoulders underneath a shirt. Commercially produced (Cooldanna, Climatech, Stacool) neck wraps and vests, which contain crystals that can be soaked in water and then become cool through a chemical reaction, are also available, but

T-shirt used as face protection against sand

Facecloth

Neckcloth

Figure 38-3. Expedient head coverings.

probably do not add much in the way of total-body cooling in extreme environments. The cravat can also be used during dust storms to protect the nose and mouth, as a towel, or to absorb moisture from plants when obtaining water. High-top (6 inches [15 cm]) boots composed of leather or synthetic materials are necessary to prevent sand, rocks, and burrs from entering the boot, support the ankle on rough terrain, insulate the foot from hot surfaces, and prevent the boot being pulled off in soft ground. Boots should be well broken in before hiking. Military-issue boots with metal spike protection can become extremely hot in desert conditions and should be avoided. Running shoes do not insulate the feet well and may become extremely hot. Socks should not be cotton, because of the risk for blisters and lack of wicking and insulation. Polypropylene or a combination of polypropylene and wool is best for socks because of less friction and thicker material. Foot care is extremely important, especially in a survival situation when walking is the only means of transportation. Feet should be inspected for blisters, foreign bodies, and abrasions on a regular basis while hiking. Socks should be changed frequently, at least twice a day, to allow them to dry out and to remove accumulated dust and sand. Leather gloves are desirable to

Chapter 38: Desert Travel and Survival protect hands from hot objects, plant spines, thorns and splinters, insects, and blisters. Abrasions and lacerations to the hands can quickly become infected in conditions where hand washing is difficult. Eye protection becomes very important in the desert, especially when traveling. Solar radiation, both direct and reflected, can cause keratitis similar to snow blindness. More commonly, blowing sand, dust, and insects may cause corneal abrasions and conjunctivitis. Contact lenses are difficult to manage in the dry, dusty environment. Tinted goggles are best, just as with mountaineering, but glacier glasses or standard sunglasses can be used. Duct tape, adhesive bandages, or other material can be used to fashion side shields for regular glasses to prevent sand and dust from entering through the sides. Insect head nets can be lifesaving, especially in African, Arabian, and Australian deserts, where insects and insect-borne diseases are a particular problem.

Survival Kit The survival kit must be carried at all times, have quality equipment and supplies, and be protected from the elements. Each item should have multiple uses if possible. There must be items that can be used for shelter, signaling, fire building, first aid, and other uses (Box 38-1). Many items will routinely be carried by most hikers and backpackers, but some specialized items should be added. One’s clothing is the basic survival shelter and if prop-

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erly selected will be the first step in protection from the climate. General-use items include a Swiss Army knife with as many blades as possible. The “Swiss Champ” includes, among many other features, a magnifying glass, which is quite useful for removing cactus spines or starting fires. Parachute cord (eightstrand) has multiple uses, including shelter construction, creation of snares, and fishing nets and lines. A signal mirror; whistle; matches, metal match, or lighter; first-aid supplies; compass; safety pins; water disinfection tablets; and plastic bags can be stored in a relatively small container that should be kept on one’s person at all times. The first-aid kit should contain bandages, insect repellent, sunscreen, lip balm, antiseptic ointment, aspirin, antihistamines, tape, and any prescription medications. The desert survival kit should include a 5- by 5-foot (1.5- by 1.5-m) piece of plastic, 4-foot (1.2 m) length of plastic tubing, and metal cup (all for making a solar still), emergency blanket (silver on one side, red on the other), extra sunglasses or eye protection, nylon canteen (minimum 5-quart [4.7 L] size), and extra sunblock.


PRIORITIES The “rule of 3s” gives us a priority list for survival. One can live 3 minutes without oxygen, 3 hours without warmth, 3 days without water, and 3 weeks without food.

Water Box 38-1. Desert Survival Kit Swiss Army knife Parachute cord Compass Topographic map First-aid kit Goggles Lip balm Leather gloves Safety pins Mosquito head net Waterproof container Rescue blanket Plastic sheet Plastic tube Metal cup Water container (5 qt [4.7 L]) Hat Sweater or pile jacket Gore-Tex jacket Duct tape Hard candy Plastic bags Matches Metal match Metal mirror Whistle Water filter or iodine Peanut butter Flashlight Sunscreen Insect repellent Cravat

The key to desert survival is water. Unfortunately, water weighs 8 pounds (3.6 kg) per gallon (3.8 L), and individual needs may be up to 2 gallons (7.6 L) per day. Always carry as much water as possible. Collapsible canteens can carry several quarts of water and keep it cooler (because the surface heat absorption to volume is less) than can hard plastic or metal (Fig. 38-4). Drink at every stop and while hiking if using a drinking tube. Flavoring and cooling water increase palatability and thus consumption. Most hikers do not carry enough water for more than 1 day, so having a method for acquiring water is mandatory. Solar stills, vegetable stills, digging along arroyos and in dry lake beds, wiping dew from plants in the early morning, and extracting water from succulent plants are all methods for obtaining water in a desert survival environment. Although there are a number of methods for obtaining water in the desert, minimizing water loss might be a better strategy

Figure 38-4. Collapsible 5-quart canteen.

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Figure 38-5. Desert water hole—currently occupied.

for a human with limited water resources. All desert plants and animals have developed adaptive mechanisms for conserving water. Humans, if they are to survive, must develop strategies for conserving their sweat, not their water. Adolph measured water intake, activity, and ambient temperature of World War II soldiers during desert operations. Soldiers who rested in the shade had significantly less water losses than those who exerted themselves in the heat of the day, and could extend the length of time they could survive, despite similar water intake. Although this may be intuitive, most desert travelers limit neither their travel to cooler times of the day nor their work activities to the shade. Employing a strategy of resting in the shade from 1000 hours until 1500 hours, drinking adequate water based on the appearance of the urine, and keeping as much skin covered as possible have decreased the number of heat casualties in the military during training exercises. Although thirst and amount of sweat on clothing are poor indicators of hydration status, the color and amount of urine produced can roughly estimate it. The darker the urine, the more concentrated it is, indicating a greater degree of dehydration. If potable water is available, it should be consumed; it is better to conserve sweat rather than water. If there is a limited amount of water, food should not be eaten unless the food contains a large amount of water. The metabolism of food, especially protein and fat, and excretion of waste products require potentially unnecessary consumption of water. Only potable water should be drunk because vomiting and diarrhea caused by contaminated water could quickly become fatal in the desert. Water obtained from lakes, streams, wells, or springs should be considered contaminated and must be made potable before drinking. Water holes may attract dangerous game as well as potential food (Fig. 38-5). Desert water may be found by looking for animal signs, such as trails or spore. Some plants, such as cottonwood, sycamore, willow, and cattails, may be indicators of water. Water may sometimes be found by digging at the outside bend of a dry riverbed or stream (arroyo and wadi are terms used to indicate rain run-off channels that may contain water during the rainy season) (Fig. 38-6). Rainwater, dew, and water obtained from a solar still or vegetable are relatively potable. Urine, seawater, alkaline pools, and brackish water should never be drunk. They contain large amounts of solutes that would require more water to excrete than they provide, thus hastening dehydration and

Figure 38-6. Desert arroyo or wadi.

Water storage tissue Xylem Epidermis

Figure 38-7. Barrel cactus showing pulp that can be a source of water.

renal failure. Liquid from radiators is contaminated with glycols and should not be drunk or used in solar stills. Many plants, such as barrel cacti and traveler’s tree, and animals, such as the desert tortoise, contain water that can be used in an emergency (Fig. 38-7). A solar still (Figs. 38-8 to 38-10) can be constructed by placing a 5- by 5-foot (1.5- by 1.5-m) piece of clear plastic over a hole 3 to 4 feet (0.9 to 1.2 m) in diameter and dug 3 to 4 feet deep in the ground into which vegetation, urine, or brackish water has been placed. Solar energy causes water to evaporate within the hole and collect on the underside of the plastic. Because it cannot escape, it will drip back into a container placed at the bottom of the hole. A tube can be attached to the inside of the container so that the water can be drunk without

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Sand or dirt to anchor plastic sheet

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Clear plastic sheet Rock

Green foliage moisture producers

Drinking tube

Container

Below ground still using vegetation as a moisture source

Sand or dirt to anchor plastic sheet

Water trough for polluted water

Clear plastic sheet Rock

Drinking tube

Water trough for polluted water Container

Below ground still for obtaining water from a polluted source

Figure 38-8. Diagram of solar still. Figure 38-9. Photo of solar still. Note the moisture on the plastic.

dismantling the still. A plug should be put in the drinking end of the tube to prevent clogging. The amount of water produced depends on the amount of moisture in the hole, the amount of sunshine directed at the still, and the size of the plastic sheet. A still dug into a dune or dry sand will not produce much water. Dew, rainwater, and edible animals may fall into the still as a bonus. Moisture can be wiped off plants during the early morning and can be squeezed from the pulp of certain plants, such as yucca or stool. Milky, bitter, or sour pulp should not be used, and the pulp should not be eaten. Water can be made potable by boiling, or using filters or chemicals (see Chapter 61).

Shelter Desert shelters are of three main types: natural, well-prepared human-made, and improvised human-made. Natural shelters are caves and rock overhangs. When using natural shelters, one must remember that there may already be other inhabitants that need eviction. Rattlesnakes, tortoises, ground squirrels, lizards, and skunks often use caves and other cool areas during the heat of the day. They may be sources of food, but are also potentially dangerous to humans. Some reptiles are venomous, and

many mammals carry rabies or plague. They can usually be removed with a stick or dispatched with a rock. Well-prepared human-made shelters include tents, vehicles, and buildings. Most vehicles become very hot inside, which may hasten heat illness and dehydration. It is better to sit in the shade of an automobile than to be inside it during the heat of the day. Tents and buildings are best if there is adequate ventilation. Improvised shelters are typified by the desert trench shelter, shade shelter, or lean-to. Any structure that provides shade, protects from wind and blowing sand, and decreases heat gain or loss is minimally adequate. The hottest area in a desert climate is at the surface of the ground, so getting above the ground or below the ground decreases exposure to the highest temperatures. Most desert animals take advantage of this fact by their behavior. Birds perch high in trees in the shade of a branch or in some cases inside of a cactus. Most mammals and reptiles burrow into the ground, where just 3 feet below the surface the temperature may be 30% cooler. Humans can imitate this behavior by constructing a desert trench shelter (Fig. 38-11). This is a trench dug in the ground 2 to 4 feet (0.6 to 1.2 m) wide, 2 to

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PART FIVE: RESCUE AND SURVIVAL loss to the ground. Given enough time, a shelter such as a tepee, tent, or lean-to can be constructed using tarps, blankets, parachute panels, or other materials (Fig. 38-13). Construction should take place in the cooler times of the day to conserve sweat and water. If one has a reliable source of water, such as a desert water hole or “tank” (natural collection of water in nonporous rock), then it is best to stay in that place and try to be rescued rather than attempting to travel large distances without adequate water.

Food Food is not as immediate a problem as water in the desert (see Chapter 65). Most humans have an extra 50,000 to 70,000 calories that they store in the form of fat and can exist for weeks without eating. Food in the form of animals or plants is usually available if water is available. Cactus fruit, such as prickly pear (Fig. 38-14), can be eaten when peeled. Legumes, such as acacia, mesquite, and palo verde, produce beans that can be crushed and mixed with water to form tortillas (Fig. 38-15). Yucca stems, cattails, agave stems, and prickly pear pads can be cooked and eaten. Avoid plants with milky saps or red berries and other plants that cannot be positively identified as edible. Mushrooms should not be eaten. It is essential to become familiar with the common poisonous and edible plants in any area through which you will travel. Insects, birds’ eggs, grubs, tortoises, and other slow movers can be captured by hand. Most small animals, such as snakes, lizards, and birds, can be killed with a rock or stick. Jackrabbits, ground squirrels, and rats may be snared or trapped. Large mammals should be avoided because the likelihood of killing one of these without a firearm is small, whereas the likelihood of becoming a casualty is high. All meat should be cooked or dried before ingestion. Animals to avoid as food or in general include caterpillars, spiders, scorpions, centipedes, millipedes, toads, and bats, as well as some mammals that carry plague, tularemia, Hanta virus, and rabies.

Hazards Figure 38-10. Photo of solar still.

3 feet (0.6 to 0.9 m) deep, and about 6 feet long. A barrier can be made of any cloth material at hand, such as a blanket, sheet, poncho, tarp, or space blanket. This barrier is placed over the trench, about 18 inches (45.7 cm) above the bottom, and its edges are weighed down with rocks or sand. Another similar barrier (the first one can be doubled back on itself if it is large enough) is placed about 12 to 18 inches (30.4 to 45.7 cm) above the first barrier and also weighed down. This construction creates an insulating barrier that traps cooler air in the bottom of the trench and reflects solar radiation from the top. Ideally, a reflective space-type blanket is used for the outer layer, which will increase the amount of heat reflected. Removing the seat from a vehicle and sitting above the ground in the shade of the vehicle or constructing shade with a blanket or tarp and available materials can provide some shelter in the heat of the day until a more adequate shelter can be built (Fig. 38-12). At night, when temperatures drop, the shade trench remains warmer because of the heat produced by the inhabitant. The top barrier, with its reflective surface, can be reversed to reflect heat back into the trench. Any insulating material can be added to the floor of the shelter to decrease heat

In addition to the hazards of heat and dehydration, there are other hazards that one may encounter in the desert. Blowing sand and dust created by vehicle traffic may cause eye, nose, mouth, and skin irritation. Desert winds up to 100 mph (161 km/hr) can blow for days, creating immense sandstorms and dust storms that can cover large areas, reducing visibility to near zero. In addition to the sand and dust, other objects can be transported with the ferocity of a hurricane. Vehicles, tents, and buildings can be demolished and roads obliterated. Sandstorms blowing for days have caused destruction in large cities, such as Melbourne and Baghdad. Exposed skin must be protected, and shelter should be sought within a hard-sided building if possible. The possibility of an individual being buried is remote, but drifting sand can block doors and strand vehicles. Quicksand is another hazard. There are two types of quicksand. The first is a mixture of sand and water found along the shores of lakes, seas, and estuaries of rivers. This type may look solid but is a suspension of fine sand and water that cannot compact. The second type is fine sand deposited by wind in hollow depressions. Depending on the depth of the depression, one could sink 15 to 20 feet (4.6 to 6 m). A person caught in quicksand can usually escape by flattening out and swimming to firm ground because most quicksand areas are small. Animals may panic and struggle, hastening their submersion. A rescuer can usually pull the victim to firm ground using a rope, belt, or

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Figure 38-11. Desert shade shelter or trench shelter. Poncho liner Dig trench 18” – 24” deep

Poncho

Sand anchor

12” – 18” airspace

Shade trench

Figure 38-12. Expedient shelters. Shelter for cold deserts

Shade shelter

Double layer of parachute cloth draped from wing

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Figure 38-13. Desert tarp shelter.

Figure 38-15. Mesquite seed pods.

strap. Removing one’s pack and throwing it to firm ground allows for easier escape. Animal hazards include venomous snakes and arthropods, carriers of zoonotic illnesses, and large mammals (Fig. 38-16; Box 38-2). Plant hazards include poisonous varieties that may cause dermatitis or systemic symptoms if ingested. Many types of plants produce spines or thorns, which commonly cause infections if they break the skin.


TRAVEL

Figure 38-14. Prickly pear fruit.

Even in the best of circumstances, hiking in the desert can be difficult. Most modern travel is performed with high-clearance, 4-wheel-drive vehicles. These vehicles should have sand mats (for added traction on soft surfaces) and a winch and cable for self-extracting the vehicle or rescuing another vehicle. Extra water, spare parts (fan belts, hoses, spark plugs, fuses, bulbs), additional fuel and oil, shovel, two jacks, spare battery, spare tires and tire patching materials, radio, and tool kit are manda-

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Figure 38-16. Western diamondback rattlesnake. Figure 38-17. Travelers on camel.

Box 38-2. Dangerous Desert Animals Arthropods Venomous

Spiders, scorpions, assassin bugs, ants, bees, wasps, centipedes, millipedes Zoonotic Disease Vectors

Fleas, sandflies, ticks, mites, mosquitoes, kissing bugs, flies Reptiles Venomous

Lizards, rattlesnakes, coral snakes, desert vipers, desert black snake, cobras, Australian elapids Nonvenomous but Risk for Attack

Crocodiles, monitor lizards Mammals Zoonotic Disease Vectors

Dogs, rodents, rabbits, bats, squirrels, cats, primates Mechanical Injuries

Camels, carnivores, donkeys, antelope, deer, elephants See also Part Six.

tory for desert travel. Traveling in convoys is a must, both for safety and, in some places, for security. Salt flats, mud flats, and soft sand can bog down even 4-wheel-drive vehicles. Never attempt to cross arroyos or wadis when they are flooding. Many areas offer no access to wheeled vehicles, so travel by camel, donkey, or horse is still common. Camels remain the most efficient desert transportation and can travel for long periods without food or water (Fig. 38-17). They also are quite resistant to blowing sand, heat, and temperature changes. Expert assistance is needed for travel by camel. Horses and donkeys are limited to short distances and require more food and water.

Current topographic maps and a good compass are essential, whether traveling by vehicle, by animal, or on foot. Local authorities should be consulted concerning water sources; these should be marked on the maps. A copy of the map should be left with someone who knows the travel plans. The route and campsites should be indicated on the map. In that way, if one becomes lost or injured, search and rescue teams will know where to initiate the search. If one becomes lost or injured, it is usually best to stay in one place and signal for help, using a mirror or other reflective object during the day and a fire at night. Cellular telephone, radio, or emergency locator transmitter may aid searchers. Flares and whistles should be used only when searchers are nearby or a search aircraft is moving in your direction. Geometric patterns drawn on the ground, such as “SOS,” “HELP,” or a large “X,” may aid aircraft in identifying the position of a distressed person. Rocks, contrasting soil, plants, or clothing can be used to produce the patterns. It is difficult to see a single human on the ground; therefore, it is always best to stay near a vehicle if possible. An automobile can be a good source of signaling equipment. The windscreen and windows reflect light, and the mirrors can be removed and used to signal. Oil can be drained, placed in a hubcap, and mixed with sand. When set on fire, it produces dense black smoke. The hubcaps can be used to dig a desert trench shelter, the battery to start a fire, and the seat covers and floor mats for shelter and footwear. If one has adequate water, knows the direction of travel, has good footgear, and decides to try to walk to safety, it is imperative to leave a note outlining plans in a conspicuous place or to draw an arrow on the ground with rocks pointing in the direction of travel. Direction finding can be accomplished without a compass using the sun or stars (see Chapter 85). Before traveling in the desert, it is best to know the location of key terrain features, such as rivers, highways, mountain ranges, and cities. Power lines, stream beds, and pipelines may also lead to civilization, but it may require days to arrive. It is dangerous to travel through arroyos or wadis because of the danger of flash flooding. Rainfall in mountains several miles away can wash down these formerly dry stream beds, pushing tons of mud, rocks, and water in a lethal torrent. Sand dunes should be avoided because of the amount of energy

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required to traverse them. Salt marshes may contain soft ground that traps the hiker. Travel in the cool of the night to conserve water, and use the stars for direction. The dangers at night are that many desert animals are more active, and the chances of falling from a cliff, stepping into a hole, or stumbling into a cactus are greater.


SUGGESTED READINGS Adolph EF: Physiology of Man in the Desert. New York, Hafner Press, 1969. Bender GL: Reference Handbook on the Deserts of North America, London, Greenwood Press, 1982. Benson L: The Cacti of the United States and Canada. Stanford, CA, Stanford University Press, 1981. Brown S: World of the Desert. New York, Bobbs-Merrill, 1963.

39

Craighead FC, Craighead JJ: How to Survive on Land and Sea, 4th ed. Annapolis, MD, Naval Institute Press, 1984. Foster L: Adventuring in the California Desert. San Francisco, Sierra Club Books, 1987. George U: In the Deserts of this Earth. New York, Harcourt Brace Jovanovich, 1976. Larson P: The Deserts of the Southwest. San Francisco, Sierra Club Books, 1977. MacMahon JA: Deserts. New York, Alfred A. Knopf, 1990. Marriott BM (ed): Nutritional Needs in Hot Environments. Washington, DC, National Academy Press, 1993. Stoppato MC, Bini A: Deserts. Buffalo, NY, Firefly Books, 2003. U.S. Air Force: Search and Rescue Survival Training, AF 64-4. Washington, DC, Department of the Air Force, 1985. U.S. Army Research Institute of Environmental Medicine: Sustaining Health and Performance in the Desert. Alexandria, VA, Defense Tactical Information Center, 1990. Wagner FH: Wildlife in the Deserts. New York, Harry Adams, 1984.

White-Water Medicine and Rescue Eric A. Weiss

Rivers have what man most respects and longs for in his own life and thought—a capacity for renewal and replenishment, continual energy, creativity, cleansing. John M. Kauffman, Flow East


DEMOGRAPHICS Rafting, canoeing, and kayaking have become the third largest outdoor recreation industry in the United States.6,36 Recent estimates place the number of rafting participants at 9.8 million.37 Participation in canoeing and kayaking (including flat-water paddlers) rose from 16.7 million in 1994–95 to 22.6 million in 1999.39 According to the Outdoor Industry Association, in 2002, there were 6.5 million white-water kayakers, with participation in river sports growing at a rate of 15% annually.37,38,49 Kayakers are almost 70% male, whereas the male-to-female ratio of rafters is somewhat more reflective of the U.S. population at 55% male and 45% female. Kayaks and rafts are also used by law enforcement officers, park rangers, and game wardens to patrol and manage their territories.30 New equipment designs have opened up more difficult rivers for exploration and commercial recreation.33 It is not surprising that the number of river-related accidents and deaths continues to increase. The American Canoe Association reports that about 130 white-water fatalities occur each year.49 This chapter examines the unique and dynamic hazards

associated with rivers and white-water paddling. Safety equipment, accident prevention, common injuries, environmental hazards, medical management, and swift-water rescue are also reviewed.


HISTORICAL PERSPECTIVE White-water boating as a recreational activity began in the United States in earnest during the late 19th century when adventurers attempted to emulate Major Wesley Powell’s Colorado River expedition by rowing boats down many of the West’s large rivers.25 These heavy wooden boats were replaced by inflatable rafts after World War II, when surplus neoprene assault boats and life rafts became available for civilian use.3 In 1966, fewer than 500 people boated the Colorado River through the Grand Canyon in an entire year. Recently, the figure exceeded 500 per day.25 Rafting did not become popular in the eastern United States until the early 1960s. In 1968, commercially guided raft trips were offered for the first time on the New River in West Virginia.51 The Chattooga River in Georgia attracted many rafters after the movie Deliverance was filmed there in 1971. The Youghiogheny River in Pennsylvania and the South Fork of the American River in northern California have become the two most heavily rafted rivers in the country.

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Figure 39-1. River rescue. The plastic kayak has revolutionized white-water sports. (Courtesy of Paul Auerbach, MD.)

Technologic advances have revolutionized river running. Electronically welded plastic has largely replaced rubber as the primary material used in raft construction, making the vessels lighter, stronger, and easier to repair. Self-bailing rafts, introduced in 1983, are now ubiquitous and provide greater maneuverability, allowing rafters to run rivers previously considered too difficult and dangerous. Unfortunately, greater mobility has been paralleled by an increase in the number of accidents occurring far from medical care. A major innovation in kayaking was the development of the plastic kayak, first manufactured in 1972 by the Holloform Company51 (Fig. 39-1). Kayaks had been previously constructed from resinous materials, such as fiberglass and Kevlar, which were more fragile and less likely to “broach,” or wrap around rocks. Paddlers were reluctant to run steep, rocky rivers for fear of breaking their boats. Most recreational white-water kayaks are now made of molded polyethylene plastic, which does not break apart and has the potential to fold when broached or pinned, trapping the paddler. The hulls or bottoms of kayaks have undergone significant changes during the past 5 years. Older-model kayaks had rounded bottoms or displacement hulls. Most white-water kayaks today have flat bottoms, or planing hulls. The flat bottom makes the kayak more stable (both on its bottom and its sides). A rounded bottom rocks in the water from side to side, whereas a flat bottom does not. Newer boat technology, combined with shorter kayaks and more advanced paddling skills, allows better maneuverability in tight, steep rapids and is pushing the limits of navigable rivers. Even Niagara Falls has been successfully run by a kayaker! The enormous popularity of rafting and kayaking has led to exponential growth of professional guide services. In 1990, 35 million people were taken down U.S. rivers by commercial companies.49 Faced with increased competition, guide services have been leading inexperienced clients with little formal training and few practical skills into difficult and dangerous rivers (Fig. 39-2). In the summer of 1988, five U.S. executives died after their raft flipped on the Chilco River in British Columbia. One of the survivors was reported to have said, “We looked at white water as sort of a roller coaster ride.”47

Figure 39-2. Class V commercial rafting on the Chattooga River, Georgia. (Courtesy of Robert Harrison,Whetstone Photography.)


MORBIDITY AND MORTALITY Deaths are relatively rare in white-water sports. In Colorado, fewer people die while engaged in rafting, canoeing, and kayaking than in climbing, bicycling, and skiing. Figures compiled by the Colorado Department of Public Health and Environment showed that 69 people died in climbing or hiking accidents, 36 while bicycling, and 32 while snow skiing during a 3-year period ending in 1995. Rafting, canoeing, and kayaking incidents, by comparison, resulted in 19 fatalities (Table 39-1). A report from the American Whitewater Association in 2000, based on data from 30 managed rivers from 1994 to 1998, placed the fatality rate of rafters, canoeists, and kayakers at 0.87 per 100,000 user-days.53 The fatality rate for kayakers alone was calculated to be 2.9 per 100,000 participants. The fatality rates of other outdoor sports are listed in Table 39-2. A retrospective analysis of injury reports submitted by commercial rafting outfitters to the West Virginia Division of Natural Resources from 1995 to 1997 revealed a total of 200 injuries with a resulting overall injury incidence rate of 0.263 per 1000 rafters. The average age of injured persons was 33.14 years; 53.3% were male, and 59.8% had previous rafting experience.52

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TABLE 39-1. Recreational Fatalities in Colorado, 1993–1995* ACTIVITY Climbing/hiking Bicycling Snow skiing Swimming Canoeing/kayaking/rafting Horseback riding Boating/water skiing Fishing Hunting

RANK

FATALITIES

1 2 3 4 5 6 7 8 9

69 36 32 25 19 18 13 11 6

*Two hundred fifty-two deaths were the result of recreational activities. Data from Colorado Department of Public Health and Environment.

TABLE 39-2. Fatality Rates of Different Activities ACTIVITY Kayaking Rafting Trekking Skydiving Scuba diving Alpine skiing Driving

FATALITY RATE PER 1 MILLION PARTICIPANT DAYS 8.7–2.2 4.5–8.7 5–15 8.7 3.1 0.57 152 (1 day of driving is 100 miles)

Adapted from Fiore DC: Injuries associated with whitewater rafting and kayaking. Wilderness Environ Med 14:25–26, 2003.

The body parts most frequently injured during rafting mishaps are the face (33.3%), including the eye (12.1%), mouth (6.6%), other facial parts (5.1%), nose (4.5%), and teeth (4.0%); followed by the knee (15.3%); arm, wrist, or hand (11.6%); and other parts of the leg, hip, or foot (10.5%). The most common injury types are lacerations (32.5%), sprains or strains (23.2%), fractures (14.9%), contusions or bruises (9.8%), and dislocations (8.2%). Most injuries occur in the raft as a result of collisions among passengers, being struck by a paddle or other equipment, or entanglement of extremities in parts of the raft.52 Because most injuries occur in the raft and involve the face, accident-preventive measures include attaching face protection to paddling helmets and carrying fewer passengers per raft. In the summer and fall of 2000, a survey was distributed to white-water canoe and kayak paddlers at riverside and through paddle club bulletins, and was posted on the Internet. Three hundred nineteen surveys were returned, reporting 388 acute and chronic injuries. The shoulder, wrist, hand, and elbow were the most common sites of injury. Sprain or strain injuries were the most common (26%), followed by laceration and contusion (17% each). Tendinitis was the most common chronic injury (44%), followed by sprain or strain (27%). Giardia infection was reported in 14%.42 Most injuries occurred while the kayaker was still in the boat (87%). Striking an object was the most common mechanism of injury (44%), followed by traumatic stress and overuse (25% each).14


EQUIPMENT The dynamic and unpredictable nature of rivers can turn any mishap into a tragedy. For this reason, the initial mission of white-water medicine is to emphasize safety and accident prevention. According to the U.S. Coast Guard’s boating accident statistics, the most common factor contributing to white-waterrelated deaths is failure to wear a personal flotation device (PFD, or life jacket).49 Exposure to cold river water can stimulate respiratory and cardiovascular reflexes, making it difficult for a swimmer to keep his or her head above water (maintain freeboard).26 The Coast Guard is charged with regulating and testing life jackets and classifies PFDs into five types. Of these, only two types are commonly used in white-water sports. The type III PFD, a vest-type jacket favored by most paddlers, permits greater mobility and comfort. The Coast Guard requires that type III PFDs have a minimum of 15.5 lbs (7 kg) of flotation (lift). Because most adults effectively weigh between 10 and 12 lbs (4.5 and 5.4 kg) in the water, this allows at least 3.5 lbs (1.6 kg) of effective required buoyancy. Type V PFDs are used by commercial outfitters because they provide greater flotation and are constructed asymmetrically, with more than half of the jacket’s flotation distributed in the front. This is supposed to turn an unconscious wearer face up. Although this may be true in calm water, it does not work reliably in swift water. A PFD should fit snugly and not ride up over the head when a person is in the water. Because even a well-fitting life jacket can be pulled off by turbulent water, some manufacturers now include crotch straps as an added safety feature. Testifying before a congressional subcommittee, the president of the National Transportation Safety Association cited the Chilco River accident to support his contention that crotch straps be made mandatory on all white-water use life jackets. Several survivors reported that their life jackets rode up over their heads and did not keep their faces above water. Life jackets with built-in rescue harnesses, pioneered by the Europeans, are now widely available in the United States. A typical harness system uses seatbelt webbing threaded through a metal retainer, then run into a plastic cam-lock buckle with a toggle. The toggle allows the user to find the buckle in white water. To release the system, the user pulls the toggle, opening the buckle and allowing the webbing to slip through the retainer and release. A D-ring mounted on the back of the jacket provides a point for clipping in a rope (Fig. 39-3). This quickrelease belt allows the wearer to attempt a strong swimmer rescue but also to get free of the tethering line quickly in an emergency. Beyond flotation, life jackets have other benefits that make them highly useful in wilderness settings. Their insulating properties help prevent hypothermia. The closed-cell foam flotation material acts as thoracic padding during falls on slippery rocks or when swimming rapids after exiting the craft. Life jackets also make excellent improvised splints; they can be fashioned into cervical collars, cylindrical knee braces (Fig. 39-4), or padded ankle stirrups. The American Whitewater Affiliation (AWA) safety code recommends the use of helmets at all times in kayaks and canoes, and in rafts and other craft when attempting rapids of class IV or greater difficulty. Surveys have shown that head

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Sewn-in chest harness

Lash tabs for knife

Pockets

Belt with quickrelease buckle

B

Toggle

Girth adjustment straps

Locking waist tie with buckle

A Figure 39-3. A, Life jacket with built-in rescue harness.B and C, A quick-release buckle allows the wearer to release the tether when necessary. It is essential for swift-water use.

C

Figure 39-4. A paddler wearing a type III life jacket around his knee as an improvised knee immobilizer to help stabilize a sprained knee.

trauma after capsizing constitutes 10% to 17% of all kayaking accidents.30,50 Another vital piece of safety equipment is a rope, which should be readily accessible and secured in a manner that facilitates rapid deployment and prevents entanglement. Throw ropes for river use should float, have a certain amount of dynamic stretch, and not absorb water. Self-contained throw

bags have virtually replaced coiled ropes for river use and generally hold about 50 to 75 feet (15.2 to 22.9 m) of 3/8-inch polypropylene rope inside a nylon stuff sack. Newer styles can be attached to life jackets for rapid access. They can also be thrown to rescuers by a paddler who is pinned or broached. Commercial outfitters and large groups of rafters should carry at least one 300-foot (91.4-m) long static rope to be used for Telfar lowers, Tyroleans, and other rescue situations in which mechanical advantages are used. Knives should be readily accessible. Fixed blades are preferable to folding ones unless the folded blade can be opened easily with one hand. Double-edged blades can cut in two directions and thus require minimal handling in precarious situations. Some modern knives designed for kayakers feature serrated edges that can cut through plastic boats during entrapment. Whistles should be worn so paddlers can alert others that an accident has occurred. Paddlers are often spread out over the course of a rapid, and yelling over the roar of the water is usually a frustrating and fruitless endeavor. Placing adequate barriers between the human body and the environment is of paramount importance in aquatic sports. Functional, insulated clothing should be considered a mandatory safety item to prevent hypothermia. Cotton is a poor choice for river wear; it loses all of its insulating properties when wet and dries slowly. Newer synthetics such as polypropylene and polyester pile absorb no more than 1% of their weight in water and maintain thermal insulating qualities when wet.28 When

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Box 39-1. American Version of the International Scale of River Difficulty CLASS I: EASY

Fast-moving water with riffles and small waves. Few obstructions, all obvious and easily avoided with little training. Risk to swimmers is slight; self-rescue is easy. CLASS II: NOVICE

Straightforward rapids with wide, clear channels evident without scouting. Occasional maneuvering may be required, but rocks and medium-sized waves are easily avoided by trained paddlers. Swimmers are seldom injured, and group assistance, although helpful, is seldom needed. CLASS III: INTERMEDIATE

Rapids with moderate, irregular waves that may be difficult to avoid and can swamp an open canoe. Complex maneuvers in fast current and good boat control in tight passages or around ledges are often required; large waves or strainers may be present but are easily avoided. Strong eddies and powerful current effects can be found, particularly on a large-volume river. Scouting is advisable for inexperienced parties. Injuries while swimming are rare; self-rescue is usually easy, but group assistance may be required to avoid long swims. CLASS IV: ADVANCED

Intense and powerful but predictable rapids requiring precise boat handling in turbulent water. The advanced river may feature large, unavoidable waves and holes or constricted passages that demand fast maneuvers under pressure. A fast, reliable eddy turn may be needed to initiate maneuvers,

scout rapids, or rest. Rapids may require “must” moves above dangerous hazards. Scouting is necessary the first time down. Risk for injury to swimmers is moderate to high, and water conditions may make self-rescue difficult. Group assistance for rescue is often essential but requires practiced skills. A strong Eskimo roll is highly recommended. CLASS V: EXPERT

Extremely long, obstructed, or violent rapids that expose a paddler to above-average danger. Drops may contain large, unavoidable waves and holes or steep, congested chutes with complex, demanding routes. Rapids may continue for long distances between pools, demanding a high level of fitness. Eddies may be small, turbulent, or difficult to reach. At the high end of the scale, several of these factors may be combined. Scouting is mandatory but often difficult. Swims are dangerous and rescue is difficult, even for experts. A very reliable Eskimo roll, proper equipment, extensive experience, and practiced rescue skills are essential for survival. CLASS VI: EXTREME

Class VI runs exemplify the extremes of difficulty, unpredictability, and danger. The consequences of errors are severe, and rescue may be impossible. For teams of experts only, at favorable water levels, after close inspection and taking all precautions. This class does not represent drops believed to be unrunnable but may include rapids that are only occasionally run.

From Safety Code of the American Whitewater Affiliation, Phoenicia, NY, American Whitewater Affiliation, 1989.

combined with a nylon or Gore-Tex paddling jacket, a synthetic underlayer provides effective protection from cold and wind. Wet suits, previously considered to be optimal garments for paddlers in extreme conditions, are stiff and somewhat constricting.1 The dry suit, with tight-fitting latex seals at the wrist, ankle, and neck, is the new gold standard for cold-water boating. By sealing water out and preventing evaporative heat loss, the dry suit can keep a paddler warm even during winter conditions.18 Overheating is occasionally a problem with dry suits. Recently, a dry suit contributed to profound and unexpected hyperthermia in a kayaker who had suffered a submersion injury in cold water.4


RIVER HAZARDS The International Scale of River Difficulty grades rivers and rapids into classes I to VI. An American version of this rating has been adopted by the AWA for most U.S. rivers48 (Box 39-1). Some western rivers use the Grand Canyon System, which rates rapids on a scale from 1 to 10. Neither scale is a truly objective standard; individual and regional variations are common, and the margin of difficulty for a particular rapid may differ significantly for kayaks and rafts. Unfortunately, impor-

tant safety parameters, such as water temperature, remoteness, and evacuation potential, are not taken into consideration. The difficulty of a river generally increases with the volume of flow and the average gradient. The volume of water in a river is usually expressed as a measure of cubic feet per second (cfs). This is the amount of water moving past a certain point during a given period of time. The volume of a river can be determined by multiplying the width by the depth by the speed of the current. For example, a channel 10 feet deep and 20 feet wide moving at a velocity of 5 feet per second (fps) equals a volume of 1000 cfs. As the water level rises, its speed and power increase exponentially, raising the difficulty of most rapids.3 When the speed of the current is doubled, the force of the water against an object in the current is quadrupled; that is, the force of the current increases as the square of its speed. Occasionally, however, a rapid becomes easier as the added water submerges hazardous obstacles. Gradient is the amount of drop between two points and is expressed as feet per mile. The steeper the gradient, the faster the water moves. Not all water flows downstream. The most common upstream flow is an eddy, which is created when water flows around an obstacle. The water piles up higher than the river level on the upstream side of the obstacle, whereas the water on the downstream side is lower. Water flows around the obstacle then back toward it to fill in the low spot. The line between

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Recirculation zone

Escape zone

Figure 39-5. Recirculating currents created by a hydraulic.Water and “swimmers” are released downstream beneath the surface.

the upstream and downstream current is the eddy line. Eddies are one of the most important features of the river for boat maneuvering and rescue. Exiting the main current by pulling into an eddy allows the paddler to stop the descent and safely scout the next rapid. It also provides a location for a paddler to set up rescue for his or her companion upstream. Hydraulics, also known as holes, reversals, rollers, suckholes, and pour-overs, are the most common hazards in rivers. A hydraulic is created when water flows over an obstacle, causing a depression that produces a relative vacuum within which the downstream water recirculates (Fig. 39-5). The water below a hydraulic is typically very aerated and presents a white, foamy appearance. Rafts and kayaks can be turned upside down by the force of a hydraulic, and if the reversal currents are strong enough, crafts and people can become trapped in the recirculating flow. When proceeding into a rapid that contains a hazardous hydraulic, one of the group should preset a rope below the hole to facilitate rescue. Hydraulics release water downstream from beneath the surface. This may be the only avenue of escape for a swimmer. Escape from a strong hydraulic may require a person to stay submerged and to resist the urge to return immediately to the surface. Surfacing too early can result in recirculation. Fortunately, most hydraulics eventually release people regardless of what action they take. Novice paddlers often misjudge the force of hydraulics. It is not the height of the drop that generates the recirculating power but rather the shape and angle of the obstruction, combined with water volume and adjacent eddy currents. A “smiling” hydraulic has its outer edges curving downstream, so that the recirculating water feeds out into the main current and is thus easier to escape. In a “frowning” hydraulic, the outer edges curve back upstream into the center of the hydraulic, making escape much more difficult. Low-head dams or weirs form massive hydraulics with enormous recirculating potential. Unlike natural hydraulics, these human-made structures form hydraulics all the way across the river, leaving no escape routes. In the Binghamton Dam disaster of 1975, a 13.5-foot Boston whaler with a 20-horsepower engine was pulled into a hydraulic while attempting a rescue, resulting in the deaths of three firefighters.45 Undercut rocks are boulders or ledges that have been eroded just beneath the water surface. These usually occur on geolog-

ically older rivers. They can be difficult to recognize and pose significant risks for entrapment and drowning, even in class II rapids. The potential for entrapment can also occur when swimmers attempt to stand up and walk in swift-moving currents. A foot can become wedged in an undercut rock or between rocks beneath the surface, causing the victim to lose his or her balance and fall face down into the river (Fig. 39-6A). With the foot entrapped, the victim cannot regain an upright or even face-up position. This type of mishap has caused drownings in water less than 3 feet deep. A swimmer in a rapid should assume a supine position, with feet at the surface and pointed downstream to serve as shock absorbers. This position minimizes the potential for both foot entrapment and head and neck trauma (see Fig. 39-6B). Strainers are obstacles, such as fallen trees, bridge debris, or driftwood, lodged between rocks or jutting out from the shore, that allow water to pass through (sieve effect) while trapping the swimmer or boater. Flooded rivers, a favorite of expert boaters, often develop many new strainers as riverbank debris is washed into the flow. In the summer of 1987, five paddlers drowned when their raft struck a large strainer on Canada’s Ellaho River.47 Negotiating a strainer requires special tactics. The safest option for the swimmer is to swim aggressively into the strainer head first rather than feet first, and then attempt to climb over the debris (Fig. 39-7A). Approaching a strainer feet first may lead to underwater entrapment (see Fig. 39-7B). Human-made hazards can also pose a threat to river runners. Bridge pilings, submerged automobiles, dams, and low-hanging power lines can pin or injure boaters. A broach occurs when a boat wraps sideways around an obstacle or when both bow and stern become stuck on separate obstacles simultaneously. Common obstacles include boulders, trees, bridge pilings, and ledges protruding from canyon walls. Drowning can occur if the paddler leans upstream away from the obstacle and flips upside down while still broached or if the boat collapses and entraps the victim (Fig. 39-8). A vertical pin happens when a kayaker plunges over a drop and the end of the boat becomes trapped between rocks beneath the surface. The force of the water can fold a plastic kayak over on itself, trapping the occupant upside down beneath the surface (Fig. 39-9).

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A A

B

B Figure 39-7. A, Proper approach to a strainer. B, Incorrect approach to a strainer.

Figure 39-6. A, Attempting to stand up in shallow water can produce foot entrapment in an undercut rock. B, Proper way to swim while in a rapid.

A survey of 365 members of the AWA revealed that 33% of serious kayaking incidents and 41% of open canoeing mishaps involved either pinning or broaching50 (Table 39-3). In a separate survey of 500 paddlers between 1989 and 1993, 42% of kayaking fatalities resulted from vertical pins, broaches, or entrapments in strainers. Kayak construction can have important safety implications in both broach and pin situations. The force of the current against the deck of the boat or back of the paddler can make it impossible for the victim to extract his or her legs and escape. Boat makers have developed kayaks with larger cockpits that make it easier to raise the knees out and escape the craft. Transverse bulkhead-type foot braces have replaced pedal-type braces to prevent the kayaker from being shoved forward in the boat. This feature ensures the escape potential offered by larger cockpits. One of the compromises of the larger cockpit, however, is that the spray skirt is more likely to come off in turbulent water.

Obstacle


SUBMERSION ACCIDENTS Almost all fatalities on rivers result from submersion. Each year, the River Safety Task Force of the American Canoe Association compiles accounts of drownings and other accidents. Every 3 years, it publishes the River Safety Report, which chronicles and analyzes these accidents.45–47,49 Most submersion fatalities occur after paddlers unexpectedly swim from their boats or become trapped in them underwater.

Figure 39-8. Broach.

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Figure 39-9. 1, Vertical pin. 2, Pitchpole pin.

2

TABLE 39-3. Serious White-Water–Related Incidents INCIDENT TYPE Vertical pin entrapment Broach entrapment Rock sieve entrapment Undercut rock entrapment Recirculation in hydraulic Long swim

NO. OF INCIDENTS

PERCENTAGE OF ACCIDENTS

18 46 16 23 47 42

8 21 7 10 21 19

From Wallace D: Scary numbers and statistics—results of AWA close calls and serious injuries survey. American Whitewater: Journal of the American Whitewater Affiliation 37:27–29, 1992.

The exact cause of drowning often remains unclear and is inexplicably blamed on immersion hypothermia. Although hypothermia induces impaired judgment and coordination and may be an important contributing factor, immersion hypothermia is probably never the sole cause of death.52 Studies by Hayward and others have shown that seminude subjects are able to maintain normal core temperatures for 15 to 20 minutes in 10° C (50° F) water.20,21 Continuous immersion for up to 1 hour would be required to produce profound hypothermia.21 Cold-water immersion precipitates drowning by three other mechanisms. Sudden cold-water immersion produces profound cardiovascular and respiratory responses. Reflex sympathetic output can markedly increase blood pressure and heart rate, resulting in lethal arrhythmias.17,26,27 An immediate and involuntary gasp occurs after cold-water immersion. This is followed by hyperventilation.8 Pulmonary ventilation increases up to fivefold because of increased tidal volume and respiratory rate.44 The initial gasp can result in aspiration of water and laryngospasm. Hyperventilation produces

respiratory alkalosis with resultant muscle tetany and cerebral hypoperfusion.8 This response can increase the risk for drowning in a person struggling to maintain an airway freeboard in rough water. The respiratory stimulation produced by cold-water immersion significantly decreases breath-holding duration.22 This fact has enormous implications for kayakers, who must hold their breath while attempting to roll up a boat after flipping upside down. This probably accounts for the unexplained swims by expert kayakers who sometimes fail to right themselves after flipping in cold water. I have found that the respiratory response to cold water can be mitigated somewhat by prior acclimatization. This is accomplished by repeatedly splashing cold water on your face for about 1 minute before entering the rapid. Peripheral cold-water–induced vasoconstriction exacerbates rapid cooling of muscles and nerves in the extremities, resulting in loss of strength and coordination.44 The ability to swim, maintain freeboard, avoid obstacles, and climb from the river may be greatly impaired.29 Even when the air temperature is warm, paddlers running cold water rivers should wear sufficiently insulated clothing. The combination of hyperventilation and muscle dysfunction can be lethal for a swimmer in rough water. A PFD helps, but does not prevent even small waves from submerging a swimmer’s head.16 These dangers make imperative the need to preset safety systems in significant rapids and to rescue swimmers first. Unfortunately, paddlers have drowned when their companions chased after equipment, assuming that the swimmer could climb out of the river without assistance.46,48 Safety kayaks with enhanced buoyancy are recommended on commercial raft trips because they provide additional flotation for clients who fall overboard. Although some maintain that the respiratory and cardiovascular reflexes can be abolished by repeated exposure of the face to cold water, there are currently no scientific data to support this theory of acclimatization.

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TRAUMA A survey of commercial raft clients revealed that the most common significant injury was a sprained or fractured ankle.51 Ironically, these injuries usually occur out of the water when walking on loose, wet, and slippery rocks during scouting and portaging or when entering or leaving the river. Ankle and other lower-extremity injuries also occur on the river when rafters are tossed onto each other in rapids. Kayakers are prone to ankle injuries from forced dorsiflexion or inversion when the bow of the boat hits an obstruction. The feet are held against the narrow horizontal braces while the heels are pushed underneath, or the entire ankle is inverted. European- and some American-designed kayaks with bulkhead foot braces have reduced this problem. Management of foot and ankle injuries should begin with ice, elevation, and compression to reduce swelling. Cold river water is usually substituted for ice. Compression wrapping is important after icing to prevent swelling from reflex vasodilation. Splinting is important to reduce pain and edema and to limit exacerbation of the injury during evacuation. Pneumatic splints, still carried by many raft companies, provide adequate support and compression but are prone to overinflation when heated by the sun. Zippers often malfunction when they rust or jam with sand. Neurovascular integrity must be checked frequently with an air splint. Ankle splints can be improvised from life jackets, kayak float bags, articles of clothing, or a SAM splint (SAM Medical Products, Newport, OR). Strains are common in white-water sports. Researchers at Dalhousie University in Halifax, Nova Scotia analyzed dynamic electromyographic potentials of the various muscle groups used in kayaking and then correlated them with videotaped sequences.34 Muscles used most often in kayaking that are prone to strain injury are shoulder extensors (latissimus dorsi, teres major, pectoralis major), medial scapula rotators (rhomboideus major and minor, pectoralis minor), lateral scapula rotators (pectoralis minor, serratus anterior), shoulder flexors and horizontal adductors (anterior deltoideus, pectoralis major, coracobrachialis), elbow extensors (triceps), and spine erector muscles. Any training program for kayakers needs to emphasize conditioning of these muscle groups. Back strain afflicts rafters, kayakers, and canoeists. Rafters are prone to back injuries while portaging, pushing stuck rafts off rocks, and carrying the crafts to and from the river. Raft guides are notorious for suffering back strain when pulling capsized customers, who often weigh more than they do, back into the rafts. Kayakers and canoeists injure their backs lifting waterladen boats and loading their crafts onto automobile roofs. Sitting for prolonged periods with legs extended and minimal back support leads to muscle fatigue in kayakers, compounding the potential for injury. Repetitive dorsiflexion of the wrist required to operate an offset (feathered) kayak paddle produces tendonitis and synovitis.32 A paddle constructed with a 75- to 80-degree offset instead of the traditional 90 degrees can reduce wrist stress. Aspirin or nonsteroidal anti-inflammatory agents ingested 30 minutes before paddling, combined with ice application afterward, may be beneficial. Wrist supports provide limited relief. The injury most often associated with kayaking is anterior shoulder dislocation. Various surveys have placed its incidence in kayakers at 10% to 16%, making it the second most common

Figure 39-10. High brace maneuver.

TABLE 39-4. Common White-Water–Related Injuries, 1980–1991 (N = 85) INJURY TYPE Shoulder dislocation Near drowning Fractures Head and neck Hypothermia Leg injuries Lacerations Fatalities

NO. OF INJURIES

PERCENTAGE OF INJURIES

14 11 15 6 4 11 9 7

16.5 12.9 17.6 7.0 4.7 12.9 10.5 8.2

From Wallace D: Scary numbers and statistics—results of AWA close calls and serious injuries survey. American Whitewater: Journal of the American Whitewater Affiliation 37:27–29, 1992.

white-water–related injury5,31,50,51 (Table 39-4). The maneuver most notorious for precipitating this injury is the high brace. Often used while supporting the kayaker in a hydraulic, surfing on a wave, or rolling the kayak upright after a flip, the high brace entails abduction of the humerus, with external rotation of the glenohumeral joint (Fig. 39-10). If the arm becomes extended behind the midline plane of the body by the force of the current, the triad of abduction, external rotation, and extension of the shoulder can stretch or rupture the glenoid labrum and capsule, resulting in anterior subluxation or dislocation.43 The paddle acts as a lever to increase the force on the glenohumeral joint. To minimize the risk for shoulder dislocation, the preferred method of bracing is the “low brace,” in which the arm is held in internal rotation and close to the body (adduction). Although initially awkward for the novice paddler, this bracing maneuver is inherently stronger and more versatile because it allows backpaddling out of a hydraulic. Exercises that strengthen the rotator cuff and deltoideus, triceps, and pectoralis muscles reinforce the glenohumeral joint.

Chapter 39: White-Water Medicine and Rescue The paddler with a dislocation is usually aware that something has gone wrong and holds the extremity away from the body, unable to bring the arm across the chest.43 The shoulder may appear square because of anterior, medial, and inferior displacement of the humeral head into a subcoracoid position. Although on-scene reduction of shoulder dislocations is controversial, immediate relief of pain, curtailment of ongoing injury, and subsequent ability to function more actively in evacuation are strong reasons to do it. Several techniques have been advocated for reduction.40 The key element is rapid initiation because the longer a shoulder remains dislocated, the more difficult the eventual reduction becomes. Relocation is often delayed because river corridors rarely afford rapid access to a flat and comfortable area upon which to place a victim in the supine or prone position, a requirement for most techniques. For river and other wilderness settings, reduction is facilitated by using a technique in which the victim is standing or sitting (Fig. 39-11). As soon as the diagnosis is made, the victim bends forward at the waist while the rescuer supports the chest with one hand. With the other hand, the rescuer grabs the victim’s wrist and applies steady downward traction and external rotation. While maintaining traction, the rescuer can slowly flex the shoulder by moving it in a cephalad direction until reduction is obtained. If two rescuers are available, one should support the victim at the chest while the other pulls countertraction and flexion at the arm. Scapular manipulation by adducting the inferior tip using thumb pressure and stabilizing the superior aspect of the scapula with the cephalad hand may augment reduction35,40 (Fig. 39-12). Shoulder reduction can also be done while the victim is sitting. Grab the victim’s forearm close to his or her elbow with both hands, and with the elbow bent at 90 degrees, pull steady downward traction on the arm. After about a minute of sustained traction, slowly raise the entire arm upward until reduction is complete. Gingerly rotating the forearm outward while pulling traction may facilitate reduction. If a second rescuer is present, scapular manipulation can be performed simultaneously as described earlier. Another relocation technique uses the victim’s life jacket to allow one rescuer to apply both controlled traction and countertraction.11 This technique requires that the victim be supine, with room for the rescuer to sit adjacent to the dislocated shoulder. The rescuer then slides his or her foot and leg through the life jacket’s arm opening, under the neck, and out through the jacket’s head opening. The rescuer’s leg functions as a head rest, whereas the foot braced against the opposite shoulder strap of the life jacket provides countertraction. Holding the forearm of the affected side with the elbow bent at 90 degrees, the rescuer slowly leans back to apply traction while the leg exerts countertraction. The life jacket allows countertraction force to be distributed across the victim’s chest. External and internal rotation can be applied to the humerus during traction to facilitate reduction (Fig. 39-13). One should always monitor circulation and motor-sensory function to the wrist and hand before and after attempting a shoulder reduction. To prevent a recurrent dislocation, the kayaker’s arm should be splinted across the chest with a sling or swath or by safety pinning the sleeve of the arm across the chest. If circumstances preclude exiting the river without further kayaking, the shoulder can be partially stabilized by wrapping an elastic or neoprene wrap around the torso and involved arm to limit abduction and external rotation (Fig. 39-14).

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A

B Figure 39-11. Weiss technique for shoulder relocation with the victim standing.A, The rescuer supports the victim’s chest with one hand and pulls down and forward (B) with the other hand.

Head, facial, and dental trauma are more common in kayakers and decked canoeists than in rafters because of the potential for flipping upside down while still in the craft. Minor abrasions, lacerations, and contusions are common; serious head injury with loss of consciousness is rare. Head and facial trauma can be minimized by wearing a protective helmet and tucking forward, instead of leaning backward, while rolling. Spine fractures have been reported in kayakers and canoers.46,47,49 Cervical spine injuries have occurred in kayakers

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Thumb pushes inferior point of scapula medially

Assistant pulls down and forward

Figure 39-12. If two rescuers are available, scapular rotation to assist shoulder relocation can be performed while the second rescuer pulls the arm down and forward.The inferior top of the scapula is pushed medially.

Figure 39-14. Shoulder harness for support after shoulder dislocation.

Figure 39-13. Using a life jacket to assist in countertraction for shoulder relocation.

in conjunction with head trauma sustained after flipping upside down. Vertical compression fractures of the thoracolumbar spine have occurred from axial loading when a kayaker landed flat after paddling over a waterfall. One kayaker was rendered paraplegic after landing on his back on rocks while attempting to negotiate a waterfall.49 Fortunately, his companions recognized the injury and kept him supported on minicell blocks from their kayaks until a backboard could be obtained. Significant visceral and musculoskeletal injury can occur when a swimmer is sandwiched between a downstream boulder or obstruction and the upstream craft that has been exited. Swimmers should always stay upstream of their craft. Many kayakers suffer abrasions and contusions to the fingers and knuckles while hanging upside down after flipping. Oar frames, oars, paddles, and the metal ammunition boxes used to keep supplies dry can all inflict injury when rafts are capsized or paddlers are tossed about in turbulent water. Blisters on the hands are a frequently reported problem in paddling surveys.51 Kayakers develop them at the metacarpophalangeal (MCP) joint of the thumb along the ulnar aspect.

Chapter 39: White-Water Medicine and Rescue

Figure 39-15. Giardia lamblia trophozoite seen by methylene blue wet mount staining under oil (1000×).The finding of cysts or trophozoites in a patient with diarrhea is sufficient to make a tentative diagnosis of giardiasis.

Common sites of blister formation in rafters and canoeists are the proximal palmar surfaces of the MCP joints. Taping and moleskin application reduce the incidence of this potentially incapacitating problem.


INFECTIONS Blisters, abrasions, and lacerations are always at increased risk for infection in an aquatic environment. Maceration from prolonged immersion in water and exposure to atypical pathogens are contributing factors. An outbreak of Staphylococcus aureus skin infections among raft guides in Georgia and South Carolina nearly led to the demise of two rafting companies.10 Sharp grommets on the thwarts of the rafts had caused repeated lower extremity abrasions. The causative organism was cultured from rafts up to 48 hours after use. Daily raft disinfection enabled the companies to remain in operation. Otitis externa (swimmer’s ear) is a common problem among paddlers. Water exposure to the ear canal macerates the epithelium and elevates the normally acidic pH of the canal, predisposing the ear to infection.12 The bacteria most commonly cultured are Pseudomonas aeruginosa, Proteus vulgaris, and Staphylococcus species.12,24 Antibiotic eardrops with or without hydrocortisone are widely available and very useful. Irrigation of the canal with commercially available solutions containing acetic acid and alcohol helps prevent infection by lowering the pH and drying the canal.24 The drops should be applied after each outing (see Chapter 75). Recent publicity given to water contamination by Giardia lamblia has been reinforced by statistics from the Centers for Disease Control and Prevention, which report Giardia organisms to be the most common pathogenic intestinal parasite in the U.S. (see Chapters 61 and 62). Giardia cysts abound in mountain streams and rivers once considered to be sources of pristine water (Fig. 39-15). They persist in very cold water and have no detectable taste or smell. Rivers are contaminated by animals that defecate in or near the water. Studies by the Wild Animal Disease Center at Colorado State University, Ft. Collins, Colorado have identified more than 30 animal species as Giardia carriers.

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Paddlers who travel to foreign countries should seek information on local endemic diseases and relevant prophylactic measures. White-water rafting and kayaking in Third World countries subject paddlers to unusual aquatic-related infections. This is exemplified by a report of schistosomiasis in rafters returning from Ethiopia.23 Schistosomiasis is endemic in large areas of Africa, South America, and the Caribbean and is transmitted to humans who swim or come into contact with fresh water containing the larval stage. Paddlers who return from endemic regions should be screened with serologic testing because up to 50% of infections are asymptomatic.32 Malaria has been reported in rafters returning from New Guinea, and both leptospirosis and hepatitis have stricken kayakers venturing to Costa Rica.2 In the United States, pulmonary blastomycosis was reported among canoeists in Wisconsin.7


ENVIRONMENTAL HAZARDS Although hypothermia is rarely the cause of death among whitewater paddlers, hypothermia-induced impairment of judgment and coordination is a significant contributing factor in many fatalities and accidents.19,29,45,46,47,54 The paddling season usually begins in early spring when air temperatures are cool and snow melt–swollen rivers run extremely cold. Paddlers with rusty skills are more prone to frequent swims and the effects of coldwater immersion. Many rivers, especially in the western United States, are controlled by dams that release water from far beneath the surface and thus remain cold year round. Placing adequate barriers between the human body and the environment and carrying adequate food and waterproof matches are of paramount importance. Another common environmental affliction suffered by paddlers is rhus dermatitis from poison oak or poison ivy. Most cases occur during spring paddling when the vines are potent but the characteristic leaves have not yet appeared. Barrier creams such as StokoGard Outdoor Cream and Tecnu Ivy Shield can be used by individuals highly sensitive to the plants. After plant contact occurs, the oil may be removed from the skin by washing within 30 minutes.13 A commercial product, Tecnu Oak and Ivy Cleanser, can remove oil from the skin for up to 8 hours after exposure. Any solvent may help remove some of the urushiol oil from the skin. Gasoline, paint thinner, acetone, and rubbing alcohol have all been reported by paddlers to be effective. Unfortunately, these products can also be irritating to the skin or frankly toxic. Treatment of rhus dermatitis consists of oral antihistamines and systemic corticosteroids. A 2-week treatment course is needed to prevent recurrence of the rash13 (see Chapter 57). Sunburn and the effects of chronic exposure to solar radiation are compounded by water’s ability to reflect up to 100% of ultraviolet (UV) radiation, depending on the time of day. Sand can reflect up to 17% of harmful UV rays. Most rivers are situated in mountains, where UV rays increase 4% to 5% with each additional 305 meters (1000 feet) of altitude.9 Sunscreens must be applied frequently because they are prone to wash off in the water. Zinc oxide and other barrier creams are more resistant to water and are preferable on areas of intense exposure, such as the nose and lips. Paddlers with fair skin should consider using gloves to protect the hands from UV exposure.

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Eye protection from UV radiation is often overlooked or avoided by paddlers because sunglasses frequently fog while on the river. Application of Dawn dishwashing soap to the lenses prevents fogging for up to 30 minutes. Polarizing lenses reduce glare off the water, but the polarizing feature does not in and of itself filter UV and infrared radiation. Venomous snakes, especially pit vipers, along with scorpions, spiders, and fire ants, are frequently encountered by river enthusiasts and should be considered potential hazards. Paddlers should know appropriate first-aid measures for envenomations. Paddlers commonly consume wild foliage, which may produce severe illness. In one published report, six rafters were poisoned and one of them died after eating water hemlock, Cicuta douglasii.32


SWIFT-WATER RESCUE Time is the most important factor in river rescue and often precludes the use of technical rope-based systems. Experience and an understanding of river dynamics are essential. The most common rescue scenario involves a swimmer who has exited the craft. The victim may be moving downstream at 5 to 10 mph in the middle of a large river. Because the dynamic nature of swift water does not often allow time for a shorebased rescue system to be established, many white-water rescues are made from a raft, canoe, or kayak. Rafts should stay close together in rapids to render mutual aid. Throw bags can be used directly from the raft to rescue swimmers, or the victim may often be reached with an outstretched arm and a paddle. A swimmer should be pulled back into the raft by grabbing the shoulder straps on his or her life jacket and then leaning backward into the raft to pull the person in. The swimmer can assist by pulling up on the frame, D-ring, or hand line as he or she is being pulled in. Kayaks can be used to rescue swimmers in midcurrent. The kayak is also an excellent platform to provide additional flotation for a swimmer who is trying to maintain freeboard in rough water. The most common method of rescuing swimmers with kayaks is to have them grab the bow or stern “grab loop” of the boat and then tow them to safety. The loop is usually sized so that it is easy to grab, yet will not admit an adult-sized hand. The swimmer can also grab onto the back of the cockpit rim and pull his or her torso onto the back deck. This gets the swimmer out of the cold water and reduces the likelihood of injury from rocks. “Boogie boards” originally developed for use in the ocean surf have been modified for rescue use on rivers. Rescue boards are larger and come with two sets of handles—one for the rescuer and one for the victim. The boards add a substantial amount of flotation to a rescue swimmer and, when used with swim fins, can provide a maneuverable platform for reaching and picking up a victim. The latest craft to be adapted to swift-water rescue is the personal watercraft, or Jet Ski. Introduced in 1987, these machines have become increasingly popular with professional rescue agencies. Because they lack an exposed propeller, personal watercraft are safe for swimmers and can negotiate shallow rivers. They can be maneuvered upstream in rapids, and turn within a short radius. Newer versions, adapted for rescue, can tow a backboard or litter device behind them and are quite stable.

Rescue from entrapment requires a higher level of skill and often presents greater potential risk to the rescuer. The method used depends on whether the victim can maintain adequate freeboard. If the entrapment site is accessible, direct contact with the victim is quickest and most effective. A rescuer may wade to the entrapment site or reach it by boat if there is a stable site to exit the craft.

Wading Rescues There are two significant risks involved in wading through swift water: foot entrapment and losing balance and thus swimming through a downstream rapid. Before wading, the river downstream should be scouted for hazards, and if possible, a rope thrower should be stationed downstream in the event the rescuer loses his footing. There are several techniques that help to stabilize balance and prevent foot entrapment or the need to swim during wading: (1) Using a paddle for support affords three-point stability and allows rescuers to wade into deeper water. Start by facing upstream, with legs slightly wider than shoulder width. Reach out, turn the paddle blade parallel to the current, and plunge it into the water. Just before the blade hits bottom, turn it sideways to the current. The force of the on-rushing water will pin it to the bottom. The paddle and your two legs form a tripod, which is more stable than your legs alone. Move slowly across the current, facing upstream, moving only one of these three points at a time. As the water deepens, you will have to lean more and more into the current. Although a pole, stick, or tree branch will work, paddle blades are better because they stay against the bottom better when used correctly. (2) A group working together as a team can wade into water far deeper and more securely than can a single individual. Group members support one another, and by standing together, also create eddies that provide protection from the onrushing current for each other. If there are two rescuers, they should face and grab each other by the shoulders of their life jackets, then wade across the current, facing either up and downstream or sideways to the current. One person moves at a time; the upstream person goes first, then the downstream person steps into the eddy created by the upstream individual. The two-person method can also be expanded for more people, with a resultant increase in stability. A strong swimmer rescue is the next quickest method, but entails significant risk to the rescuer (Fig. 39-16). The rescuer is tethered to a rope that provides added stability against the force of the current. If a quick-release harness is not available, a loose loop of rope can be passed under the rescuer’s armpits. A tag line rescue should be considered if the victim cannot be reached directly. A tag line is a rope stretched across the river downstream that is then brought upstream to the victim (Fig. 39-17). Getting the line across the river sometimes constitutes an insurmountable obstacle. If the river is narrow, it may be possible to throw the line across. Otherwise, it can be ferried across by a boat or team of swimmers. During a ferry, as much of the rope as possible should be kept out of the water to avoid drag. There are two types of tag lines (Fig. 39-18). A floating tag line has a life jacket or some other flotation device attached to the middle to keep the rope on the surface, which helps support the victim. A snag tag is a weighted line submerged and walked upstream to snare a foot or other body part that has been

Chapter 39: White-Water Medicine and Rescue

Figure 39-16. Strong swimmer rescue. eddy

Figure 39-18. Two throw bags connected with a carabiner to make a tag line.

Figure 39-17. Tag line.

trapped under the surface. A snag tag can be made by joining together two throw bags filled with rocks (Fig. 39-19).


APPENDIX A: WHITE-WATER FIRST-AID KITS

The following variables should be considered when designing a white-water first-aid kit: remoteness and accessibility of the river, difficulty of travel conditions, number of people the kit will need to support, preexisting medical conditions, and space and weight restrictions. When assembling a kit, the following components are generally recommended for rafting and kayaking:

Rafting Kit Waterproof dry bag or Pelican box Cardiopulmonary resuscitation mouth shield (CPR Microshield) Hypothermia/hyperthermia thermometer Bandage scissors Fine-point tweezers or forceps Temporary dental filling (Cavit) Glutose paste Irrigation syringe with 18-gauge catheter Povidone-iodine solution 3M surgical stapler (1 stapler holds 25 staples) Dermabond tissue glue Wound closure strips (Steri-Strips) Tincture of benzoin Polysporin ointment Moleskin Latex or nonlatex (hypoallergenic) gloves Antiseptic towelettes Safety pins Waterproof matches Accident report form and pencil Large garbage bag 4- × 4-inch sterile dressings 8- × 10-inch trauma pad or Bloodstopper dressing Eye pads

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Rope on surface

Submerged throw bag

Figure 39-19. Submerged snag tag.

Nonadherent dressing (Xeroform or Aquaphor) Triangular bandage 3-inch conforming gauze bandage 3-inch elastic bandage with Velcro closure 1-inch × 10-yard surgical tape Duct tape (can be wrapped around the paddle shaft) Strip and knuckle bandages Cotton-tipped applicators Aloe vera gel Diphenhydramine capsules Cortisone cream Acetaminophen tablets Ibuprofen tablets Eardrops Prophylactic eardrops (mixture of rubbing alcohol and white vinegar) Treatment eardrops (Cortisporin Otic Suspension) Epinephrine (injectable) or EpiPen Prochlorperazine suppository Diazepam or midazolam Oxycodone Oxymetazoline (Afrin) nasal spray Antibiotics (trimethoprim-sulfamethoxazole, ciprofloxacin, cephalexin) Sunscreen (sun protection factor [SPF] 15 or higher) Insect repellent Iodine tablets Tampons Tea bags Kayaking Kit Waterproof dry bag or small Pelican box Cardiopulmonary resuscitation mouth shield Hypothermia/hyperthermia thermometer Scissors

Fine-point tweezers or forceps Small surgical stapler (3M) or Dermabond Glue Wound closure strips Tincture of benzoin Polysporin ointment Latex or nonlatex (hypoallergenic) gloves Antiseptic towelettes Safety pins Waterproof matches Accident report form and pencil 3- × 3-inch sterile dressings Nonadherent dressings 2-inch conforming gauze bandage Duct tape Strip and knuckle bandages Cotton-tipped applicators Diphenhydramine Acetaminophen Ibuprofen Prophylactic eardrops (to protect against otitis externa) Epinephrine Prochlorperazine suppository Diazepam or midazolam Oxycodone Sunscreen Insect repellent Iodine tablets


APPENDIX B: UNIVERSAL RIVER SIGNALS

Stop: Potential hazard ahead. Wait for “all clear” signal before proceeding. Form a horizontal bar with your

Chapter 39: White-Water Medicine and Rescue

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Figure 39-20. Stop signal. Figure 39-22. All clear signal.

Phone: 703-451-0141 Fax: 703-451-2245 E-mail: [email protected] American Whitewater (AW) P.O. Box 1540 Cullowhee, NC 28723 Internet: www.americanwhitewater.org Phone: 1-866-BOAT-4-AW E-mail: [email protected] Figure 39-21. Help/emergency signal.

outstretched arms. Those seeing the signal should pass it back to others in the party (Fig. 39-20). Help/Emergency: Assist the signaler as quickly as possible. Give three long blasts on a whistle while waving a paddle over your head (Fig. 39-21). All Clear: Come ahead (in the absence of other directions, proceed down the center). Form a vertical bar with your paddle or one arm held high above your head. Paddle blade should be turned flat for maximum visibility. To signal direction or a preferred course through a rapid around an obstruction, lower the previously vertical “all clear” by 45 degrees toward the side of the river with the preferred route. Never point toward the obstacle you wish to avoid (Fig. 39-22).


APPENDIX C: ORGANIZATIONS American Canoe Association (ACA) 7432 Alban Station Boulevard Suite B-232 Springfield, VA 22150-2311 Internet: www.acanet.org

Chinook Medical Gear, Inc. 120 Rock Point Drive, Unit C Durango, CO 81301 Internet: www.chinookmed.com Phone: 970-375-1241 Toll Free: 800-766-1365 Fax: 970-375-6343 E-mail: [email protected] Special Rescue Services P.O. Box 4686 Sonora, CA 95370 Internet: www.specialrescue.com Voice: 209-743-9451 Fax: 503-210-8179 E-mail: [email protected] National Organization for Rivers (NORS) 212 West Cheyenne Mountain Blvd. Colorado Springs, CO 80906 Internet: www.nationalrivers.org Phone: 719-579-8759 Fax: 719-576-6238 E-mail: [email protected] The references for this chapter can be found on the accompanying DVD-ROM.

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40

Caving and Cave Rescue Steve E. Hudson and Loui H. McCurley

Caves are among the most awe-inspiring features remaining on Earth. The idea of finding virgin territory within a few miles of major cities worldwide is breathtaking. Caves are a world all their own. Unlike the far reaches of space or deep trenches of the oceans, uncharted caves can be explored by any reasonably fit person, without a plethora of fancy equipment. Caves are found on every continent in a wide array of forms. There are limestone caves, lava tubes, ice caves, marble caves, shelter caves, and water-filled caves—the variations are endless. Full of beautiful formations, strikingly odd structures, and with mystical allure, caves have intrigued man since prehistoric times. From the practical use of caves as shelter to the sheer exhilaration of sport, it is the physical challenges of caving and the rare environment in caves that set them apart. Cavers are a rare breed—people who thrive on the prospect of exploring deep canyons and pits within the earth. Fascination with the unseen, the thrill of the frontier, the personal contest of confronting the unknown, and the very darkness itself offer a distinctive aroma of adventure to which respond both exceptional cavers and the merely curious. Caves can contain hostile environments. Medical and rescue professionals in particular should be thoroughly familiar with the harsh realities of the cave environment well in advance of engaging in medical or rescue duties underground (Fig. 40-1). Even experienced cavers can quickly find themselves in unexpected trouble. Such was the case for Frank and Jim, two experienced cavers who explored a seldom-visited side shaft within an extensive cave in Georgia. It took Frank and Jim about 3 hours to walk up the mountain, negotiate the entrance, climb down into the cave, traverse several hundred feet of passage, rig and rappel a 125-foot (38.1-m) pit, travel across several hundred feet of additional passage, and then rig a side shaft they wanted to explore that ran parallel to the cave’s main 586-foot (178.6-m) pit. Once down the shaft, Frank walked across a large rock slab. It shifted from his weight, and his lower leg was quickly pinned between the slab and the shaft’s wall. Frank’s lower leg was crushed, with pieces of bone sticking through an open wound. Over the next hour, Jim helped free Frank’s leg and did his best to stabilize the injury and make Frank as comfortable as possible. Realizing there was no way Frank could climb the more than 550 feet (167.6 m) of rope back to the surface, much less walk and climb through the hundreds of feet of horizontal passage, Jim went out for help, leaving Frank alone, injured, and in great pain. With the grim realization that he was now solo-caving and in extreme peril himself, Jim carefully climbed the pits and

exited the cave as quickly as possible. Once down the mountain, he drove to town and notified local authorities. Fortunately, the incident had occurred in a region of the country where an experienced cave rescue team was available. The team was called out and a response initiated. The first rescuer reached Frank about 7 hours after the accident. It took another 9 hours to get Frank up and across the pits and out the entrance passages using hauls, highlines, and team hand-carries. Next came a 30-minute four-wheel-drive trip off the mountain to the waiting ambulance. A short 15-minute ride had Frank in the nearest hospital. The rescue involved about 50 people, both inside the cave and as above-ground command and support. Total time was about 17 hours from accident to emergency room. Approaching such a cave rescue situation with the mindset of it being merely a dark version of a typical wilderness environment is at best naïve and at worst a recipe for disaster. As for any environment, potential rescuers should be trained, experienced, and adept in functioning in the cave environment individually before assuming any sort of rescue role. The first thought that enters the minds of many newcomers to caving is “claustrophobia.” In fact, claustrophobia is usually less of a problem for cavers—even new cavers—than such things as physical agility, route finding, endurance, and maintaining optimum performance levels in cold, wet, and confined surroundings. Learning to cope, indeed to thrive, under such circumstances is a prerequisite for the challenges of cave rescue. Not only must a cave rescuer be adept at managing the unique trials of functioning in the cave environment, he or she must also manage a unique set of rescue problems relating to safety, equipment, logistics, access and extrication, and mission support. A cave rescue should be initiated only with the direct and intimate involvement of qualified cave rescuers. Rescuers without cave experience, or cavers without rescue experience, are not sufficient resources with whom to launch a cave rescue. The demands of each of these vocations are unique enough in themselves; the two together create demands that are humbling. In addition to experienced ground personnel, the incident commander must be familiar with or seek the advice of someone who is familiar with the unique challenges of the cave environment. The time to learn about caving is not as a medic on a cave rescue. If there is any chance that one will encounter a cave rescue as part of his or her profession or avocation, time should be spent becoming familiar with caves and caving techniques;

Chapter 40: Caving and Cave Rescue

Figure 40-1. Opening header shot of litter in tight spot. (Photo courtesy Kris H. Green.)

the effort will at least be rewarding, and ultimately may be lifesaving.


ENVIRONMENT Any natural opening in the earth large enough to enter is considered a cave. Caves are similar to human-made mines and tunnels only in that they share a subterranean setting. On a practical level, mines and tunnels must be approached with skills, equipment, and training that differ from those for caves. This chapter addresses only natural caves such as may be found in a wilderness environment, and not their dissimilar humanmade counterparts. Caves take many forms, including sinkholes, cracks, sumps, siphons, springs, pits, and caverns. The precise geology of cave formation is a more complex and diverse topic than can be adequately addressed within the confines of this chapter. Some caves are simply topographic in nature—cracks and fissures that are a natural result of typical geologic features. In this number are counted lava tubes, which form when a volcano erupts and lava flows away from its center. Gases create bubbles in the molten rock, leaving voids as it hardens. Lava tube caves form as flowing lava cools hard on the outside and continues to flow on the inside, leaving a tube of passage. Like most caves that are formed as a result of earthen upheaval and movement, lava tubes are unpredictable and may run for long distances or be limited to short passage and isolated rooms. More interesting, perhaps, is the geology of caves that form over long periods of time. An oversimplification of this formation process is that caves—particularly limestone caves, but in truth any cave found in carbonic rock—are most often formed as a result of solution reaction between water, carbon dioxide, and the rock. Known as karst, such topography is formed when carbon dioxide and water combine to form weak “carbonic acid,” which in turn works to dissolve the carbonic rock. This process is most commonly found in limestone areas.

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As the limestone dissolves, the acid solution follows the path of least resistance through the earth, and eventually pits are formed, then fissures, and eventually passage. When the calcium carbonate–infused water reaches a large enough opening, the carbon dioxide dissipates and the calcium carbonate is deposited as stalagmites (icicle-like columns protruding from the ground) and stalactites (icicle-like columns hanging from cave ceiling). Sumps, siphons, and springs are all names that describe specific features in water-based cave formations. Springs, an outflow of water from the earth, are an obvious access point between underground passage and the surface, but they can be called a cave only when they are large enough for a person to enter. Springs differ from siphons in that where springs outflow water, siphons take in water. Air-filled cave passages that terminate in water-filled passages are known as sumps. Some sumps are only a few feet long before returning to air-filled sections, whereas others can be thousands of feet in length and may never resurface. Sinkholes, cracks, pits, and caverns are terms that describe passage. These may be wet or dry and are differentiated by their shape and attributes. Sinkholes, also called sinks, are formed when bedrock above a void collapses. Sinks may present as a sheer vertical opening into a cave with a well-like or open-air pit entrance, a steep sloping depression with a cave entrance, or a shallow depression of many acres that may not have more than a small, impassable sump to the cave below. Cracks are narrow vertical passages formed as the carbonic acid solution finds its way through the ground. These are usually, but not always, developed along a joint in the rock. The term pit refers to a vertical cave passage. Pits can be found both inside caves and at the surface. Most open-air pits form when the roof of a sinkhole collapses. Pits can also be formed by solution or erosion of passage by flowing water. Solution caves formed in soluble rock are the most common type found on Earth. Depending on local weather conditions and length of time, caves can take up to tens of thousands of years to form to a point where humans can enter. They are always getting larger through solution and erosion, or smaller by filling in with sand, mud, and fallen rock. These changes often happen so slowly that they are seldom noticeable. Most cave ceilings and walls are relatively stable. Large breakdown blocks of fallen ceiling and wall rock are often found in caves, but the chances of one falling precipitously are slim. Breakdown usually occurs suddenly as a result of a major environmental event, such as an earthquake, or very slowly over years as the supporting rock below slowly degrades. Smaller rocks and rock slopes, often the result of ceiling and wall breakdown, are actually the greatest dangers in caves. Because they have not been stabilized by frequent travel, these slopes can shift and slide underfoot. The continuous conduit leading through a cave is known as passage. Passage can be huge, with room dimensions so large it is difficult to see distant walls (Fig. 40-2) even with a light, while just around the next corner, passage can change to tight impenetrable cracks or a dead end (Fig. 40-3). Some caves have passages that wander around in a maze that may total many miles in as little as a few acres of ground. Others may go for miles in the same direction and involve dozens of miles of passage. Many caves are only a few hundred feet long and contain only low, tight, belly-crawl passage. Passage that opens into a wide area

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Figure 40-2. Typical large “room.” (Photo courtesy Kris H. Green.)

Figure 40-4. Wet passages require appropriate clothing. (Photo courtesy Kris H. Green.)

Figure 40-5. Close contact. (Photo courtesy Kris H. Green.)

Figure 40-3. Typical tight crack passage. (Photo courtesy Kris H. Green.)

is called a room, whereas tight, narrow passage may be further described as a squeeze or crawl. Caves are formidable, dark, and often dangerous. Considering that running, seeping, or standing water originally formed most caves, it is not surprising that water is a major part of many cave environments. Cavers and rescuers must be prepared to negotiate anything from crawls in water-filled tubes (Fig. 40-4) to underground rivers so large that a boat is required. Caves that are no longer hydrologically active are called dry caves or dead caves because they are no longer in their formative state. Some caves are so dry that dust induces respiratory problems in visitors. Visitors to dusty caves should wear appro-

priate filter masks as a minimum level of protection from dust stirred up by the act of moving through a dry passage. Temperature extremes are another common characteristic of caves. Caves tend to be at the mean ground temperature of the area. For the most part, U.S. continental caves run from cool to cold. Very warm climates, such as in Puerto Rico, sport warm caves, whereas alpine mountain caves in places like Montana measure close to freezing temperatures and may even contain ice. Caves found in tropical and desert environments can be so hot that cavers must wear lightweight garments to explore them, and even then run the risk of heat illness. A more common scenario in cave rescue, however, is the concern of hypothermia from sitting around underground waiting for the next assignment or struggling in cold and wet passages. Temperature differentials can also exist within a single cave, as a result of exposure, orientation, and water flow. These temperature differentials, as well as pressure differences, can result in winds flowing through the passages. It is not uncommon to be supine or prone in 4-inch deep, 13° C (55° F) water with one’s back pressed against cold rock, facing a stiff breeze (Fig. 40-5).

Chapter 40: Caving and Cave Rescue Caves can be fragile, often heavily decorated with mineral formations that have formed over thousands of years. Cavers try to protect these formations whenever possible by avoiding walking on or touching delicate areas or otherwise altering the cave. Even the natural skin oils deposited by human hands can alter growth of an active formation. The caver’s motto, “leave nothing but footprints, take nothing but pictures, and kill nothing but time,” extends to rescue operations. Everything brought in must be packed out at the end of the operation. An abandoned flashlight battery can leach its chemicals and poison the cave-adapted life forms found in a cave passage, ultimately destroying the cave and its environment.


PERSONAL SAFETY Whether entering a cave for exploration or for rescue purposes, personal gear requirements are tailored to caving. Clothing should be appropriate to the environment. Caves can be wet, dry, dusty, cold, warm, or a combination of these. The wind that can exist in passages makes chill factor an often unpredicted yet significant consideration. Undergarments should provide the necessary thermal layers and be of a fabric that remains warm when wet. Layering undergarments and thermal layers provides the most versatile system of clothing. Many cavers wear protective suits with a rubberized, vinylcoated, or Cordura outer layer, and in very wet caves, it is not unusual to find cavers in wetsuits. Coveralls or one-piece garments with no exterior straps or accessories help prevent snagging in crawls or tight passage. Ventilation is an important consideration in accommodating the various degrees of exertion required in caving. A mountaineering type of helmet, with a nonelastic “threepoint” chin strap that keeps it planted properly on the head, is a must. The helmet protects against impact with the hard and often sharp rock of cave ceilings and walls in tight or low passages and offers rock fall protection. It is also a convenient mounting platform for the required light source (Fig. 40-6). It takes only one episode of trying to navigate in complete darkness underground to understand why no fewer than three light sources should be carried by each person in a cave. Rescuers underground without functioning lights become other

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subjects to be rescued. Electric lights are preferred, but carbide lamps may also be used. At least two of these lights should be helmet mountable for hands-free operation, each with sufficient “burn time” capacity or spare batteries to travel in and out of the cave. If carbide lamps are used, care should be taken when working close to victims because it is easy in tight spots to forget that the light on your head is an open flame that can quickly burn anything with which it comes in contact. For this reason, most cave rescuers prefer electric lights. Many cavers find gloves useful for both thermal insulation and protection against sharp rocks and sticky mud. Neoprene or rubberized gloves are popular choices, and scuba or sailing gloves offer durable protection. If the cave has vertical components, leather-palmed gloves are necessary for rope work. Ideally, a rescuer should carry a different pair of gloves for rope work than for negotiating muddy passage. Cave mud is slippery and adheres to everything. It makes walking and scrambling through a cave dangerous. Lug-sole boots provide the best traction, and stiff leather uppers help protect feet against sharp rocks. For small passages, or “crawlways,” a set of durable kneepads is a necessity, and many cavers use elbow pads as well. As in any remote environment, the caver should be selfsufficient and at least able to care for himself or herself for an extended period. This requires replacement batteries or carbide, fresh water for drinking, food for energy, a basic first-aid kit, and extra insulation, such as extra thermal layers and a hat that can be worn under the helmet. Cavers often store a folded trash bag in the suspension of their helmets to be used as an emergency shelter from wind and water, among other possibilities. For the cave rescuer, the concept of self-reliance extends to being capable of caring for oneself as well as a patient for an extended period of time. Although the responsibility of patient care may be shared among several people, it takes planning to ensure that enough extra gear exists within the group so that the patient can be appropriately equipped and cared for. An additional challenge for the extended cave visit is the requirement to pack out whatever is packed in, including human waste. Strong, leak-proof plastic containers are useful for that purpose. Use a small, durable pack to carry extra gear. Because the pack will be alternately carried, pulled, pushed, and dragged through cave passages of different sizes, excessive size, straps, and external attachments should be avoided because they can impede maneuverability. Not all caves have vertical drops, but for those that do—or when in doubt—a lightweight seat and chest harness, brake bar rack or figure-8 descender, and ascending system are essential. One or two 20-foot sections of 1-inch tubular webbing come in handy for an extra step-up or to construct a quick belay or hand line. Vertical caving is a highly specialized sport, and vertical cave rescue even more so. The National Cave Rescue Commission offers courses in cave rescue, recommended for experienced vertical cavers.


CAVE NAVIGATION Figure 40-6. Typical helmet-mounted light. (Photo courtesy Kris H. Green.)

Navigating through the cave environment can be disconcerting, particularly because of the three-dimensional nature of travel.

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Cave passage moves upward, downward, and side to side through the layers of the earth. It may overlap, cross, and twist, all without the benefit of sun, stars, or moss on the north sides of trees to provide directional clues. It is always best for several cavers (or cave rescuers) in a given party to be familiar with the cave and be responsible for navigation. If this is not possible, several options exist. The first, and best, is to use a cave map. Reading a cave map is an acquired skill, and one that every cave rescuer should possess. In a pinch, cavers use navigational skills such as remembering landmarks, leaving temporary route markers (be sure to pick them up on the way out!) and using one wall of the cave as a source of consistency. Route markers are especially useful in cave rescue so that the rescuers can focus on the job at hand. In an unfamiliar cave, keep track of prominent features so that you can find your way out. Passage often looks different on the way in than it does on the way out. A small crawl that enters into a large room can be hard to find hours later when returning across that same room. One trick for finding one’s way out later is to get in the habit of turning around and looking at the passage as you enter into a different room, take a significant turn, or negotiate a climb. Rock cairns, light sticks, and flagging tape can be used as reminders, as can leaving pieces of reflective tape to mark your way and removing them again as you leave the cave.


CAVE SEARCH When the location of the rescue subject is unknown, a search will be required. Searching a cave is a potentially hazardous task and must be done meticulously and under good planning and management.1 A manager of a cave search uses the same basic skills as does an above-ground rescuer. Once the decision is made to begin an in-cave search, teams of cavers will be formed into task forces. Each Search Task Force’s role is to look for, preserve, record, and recover clues that will lead to finding a missing person. The task force should consist of two or three people with one or more members familiar with basic search techniques, the cave being searched, and cave map reading. They should be able to perform basic first aid, including patient assessment. Required equipment in addition to personal caving gear discussed earlier would include basic medical supplies, materials to mark passages, pencil and paper, food and liquid for the subject, hypothermia protection for the subject, a map, and a compass. A marking system using colored flagging tape or other means should be established to mark side passage that has already been searched and to differentiate the best route in and out once a subject has been located. Each Search Task Force should obtain a briefing from command and then follow instructions as to where to search, how long to search, probability of detection, how to preserve and record clues, how to report if a clue is found, and the debriefing procedures on return. If the search subject is found, the task force will assume the functions of an initial response task force. These are to determine whether the scene is safe, access the subject, treat the subject, consider possible courses of action, including walking the subject out if conditions allow, and then immediately notify command. The report to command should include a full subject assessment, the task force’s recommendation for course of action, additional medical equipment or personnel needed, type of litter

needed, obstacles to evacuation, any rigging that will be needed, and suggestions for action to be taken.


BASIC EVACUATION On any cave rescue, each person entering the cave must have at least the minimum complement of personal gear, as described in the previous section. Beyond this, the amount of equipment used during a cave rescue is prodigious, particularly in a cave with complex terrain. Equipment and personnel are used nearly as quickly as they can be produced; dry clothing, food, and water become valuable commodities; and extra supplies not normally used in cave exploration become necessities. The latter group, items not normally used in cave exploration, should be sourced, tested, and stored at the ready well in advance of being needed. Communications equipment, such as hard-wired field phones or cave radio systems, can be particularly difficult to find—as can experienced personnel to operate them. Other needs may include generators, warming tents, food services, and a command post. Although most cave evacuations require litter transport, each individual situation should be evaluated carefully to determine whether a litter is really necessary. A properly stabilized “walking wounded” caver can be helped out of a cave in short time and with little manpower. Put that same person into a litter, and the number of rescuers and hours to the hospital goes up exponentially. One crisp October day, cave rescuers in Georgia were dispatched to Pettijohn’s Cave on Pigeon Mountain to evacuate a fall victim some 30 minutes from the entrance. Samuel, a fit, experienced caver who was quite familiar with the cave, had taken a fall, experiencing a dislocated shoulder in the process. Pettijohn’s Cave is normally considered a horizontal caving experience, but it also involves scrambling over breakdown block and negotiation of several short, vertical drops. Although Samuel and his friends were quite familiar with the cave and he could easily negotiate the passage under normal circumstances, loss of the use of his arm would make it impossible for him to balance or climb on the difficult terrain. The pain of such a dislocation complicated matters greatly, and even a litter evacuation would prove to be a trying ordeal. Terrain in the cave dictated that litter evacuation would require several roped systems, including an initial raise of 15 to 20 feet, a 100-foot highline, and one to two more raises to lift the patient through and out the cave entrance. Although only an estimated 30-minute walk into the cave, the evacuation would easily encompass 6 hours and require numerous riggers and scads of equipment. The arrival of an experienced paramedic resolved the evacuation in short order by reducing the dislocation and immobilizing the limb securely to the victim’s body. Instead of litter lowers and highlines, the rescuers were able to rig handlines, and Samuel walked out of the cave under his own power in a fraction of the time that the technical evacuation would have taken. Not all cave rescue scenarios benefit from the fitness and ability of such a caver or the good fortune of a medical situation that can be resolved by a skilled paramedic on scene. If litter transport is deemed necessary, the next difficult decision is which litter (or litters) to use. On any given evacuation, this

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cave grit, and the entire kit can be packaged in a large-mouthed bottle or other watertight, durable container. Because of extended times involved in reporting caving accidents and responding to and accessing injured cavers, most victims are either very stable or dead by the time medical help arrives. Advanced life support (ALS) skills and equipment are generally not required. This is fortunate because the effects of cave mud and water are not particularly friendly to medical electronics. Sometimes a cave accident victim is so badly injured that physicians or paramedics on scene choose serious drug intervention. At these times, electronic tools for monitoring vitals can be extraordinarily valuable, but great care should be taken. The cave environment is neither kind to such devices, nor is it friendly to even simple interventions such as intravenous (IV) infusions. In most cases, hanging a gravity-operated IV line is not an option, and positive-pressure infusion methods must be used. Furthermore, consideration must be given to methods for keeping the insertion point clean, and care taken not to interrupt flow while negotiating tight passageways.

Equipment—Vertical Evacuation

Figure 40-7. Plastic litter offers patient protection and slides easily through passage. (Photo courtesy Kris H. Green.)

selection requires a fine balance of requirements. Maneuvering a bulky litter through narrow cave passages can be a challenging proposition. In larger caves, or where a vertical raise is required, basket litters are the best choice. Plastic-bottomed versions are preferable over steel and mesh versions because these allow the option of dragging the litter where necessary (Fig. 40-7). In tighter caves, drag-sheet types of litters, such as the wraparound Sked, provide low-profile and relatively flexible advantages, but are less comfortable or protective for the victim. Occasionally, a cave is so restrictive that even the length of a flexible litter is problematic, and a short board, such as a KED or OSS, is the only alternative. It is not unheard of to begin the carry in a tight section of a cave using an OSS, add a Sked once the passage opens up a bit, drop the Sked into a full basket litter for ease of carrying in a large walking passage, then drop all the way back to the OSS to negotiate a tight entrance passage. When choosing a litter and victim packaging, duration of transport and patient comfort should be prime considerations. Natural positioning, pressure points, and temperature are all key concerns. Although rescuers are working up a sweat, the patient lying in the litter is stationary, unable to regulate his own comfort, and can be extremely cold. Waste elimination may well need to be provided for. Thermal layers are a necessity and include a sleeping bag, vapor barrier, and moisture barrier to keep the patient dry. A full-body vacuum mattress works well as padding, immobilizer, and insulator. The patient should also have adequate head and face protection and, if the environment will become vertical at any point, a harness. A reasonable first-aid kit for a cave rescue operation should contain writing materials for recording victim condition, basic medications, airway management tools, bandages, cervical collars, and splints. Sealing each item in plastic helps keep out

Ropes used for high-angle underground rescue are usually of the static kernmantle variety. Low stretch, abrasion resistance, and consistency of quality are considered key ingredients. Caves can be harsh and unforgiving, so for this purpose, the tougher the sheath, the better the rope. The toughest-sheathed rope is usually less pliable and forgiving than those more prone to abrasion, so skilled riggers should be used for the task. Rope length may vary, depending on the particular cave and the resources at hand. Ideally, rope lengths should be sufficient to negotiate each drop without tying knots to join ropes. Knot passes can add undesired complexity to the operation. Most cave rescues involve negotiation of difficult passage as well as raising the patient from below ground to the surface. This may be accomplished in any number of ways, but pulleys and haul systems are generally basic necessities. Techniques used in high-angle rescue in the cave environment are quite similar to those used above ground, but may be complicated by tight spaces, darkness, environmental conditions, and lack of alternative routes. Brake bar racks are most often preferred for lowering operations because of their variable friction advantages. Aside from these, adequate carabiners, anchor materials, and other hardware should be available for rigging. If multiple locations must be rigged for raising, lowering, or traversing, the best possible scenario is to have enough gear to rig each site individually. Having to de-rig a system, sort the gear, carry it past the proceeding litter, and re-rig another system can be time consuming and derail the entire operation. Even a small cave might require multiple sites rigged for safe patient extrication. Prebagged packages of gear for specific common rigging tasks are often useful. These include anchor webbing, ample carabiners, pulleys, prusiks, belay devices, lowering devices, and rope grabs as required to set up one site per bag.

Logistics Lack of easy communication, limited access, extended time, and difficulty in obtaining rest and nutrition for teams all contribute to complexity. Communication is essential to keep rescuers from becoming lost, to issue instructions, and to maintain the tempo of the

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operation. Various hard-wired field-phone systems are available for use in cave rescue, but generally only well-established teams have access to these. A relatively new development is availability of special low-frequency cave radios that can transmit voice through dense rock and soil. Without such systems, message runners are indispensable. A group of swift, agile, safe, and well-trained cavers with waterproof notepads—and a method for keeping them rested and nourished—is invaluable. A team of rescuers sent into a known location can take hours or most of a day to reach the victim. It is logistically impractical for these rescuers to carry sleeping bags and food to allow rest and recovery before starting their work assignment. Keeping rescuers rested, fed, watered, and warm many hours away through a challenging cave rescue requires an incident management team that can predict the needs of the underground workers hours before they themselves realize the need. Whether or not a communication system is available, establishment of a control point at or near the cave entrance is critical. Entrance control should be established as soon as rescuers arrive at the cave. All personnel and equipment entering or leaving the cave should be recorded into a log kept by people assigned to maintain entrance control. This log becomes invaluable hours later to determine when teams should be replaced, if someone is still in the cave, and who carried in what piece of missing vital gear. The Incident Management System (see Chapter 20), or a modified version of it, provides the best framework for managing cave rescue personnel by performing required functions while maintaining a reasonable span of control. Generally, the functions required on a cave rescue are similar to those required on any other rescue, although the specific means of accomplishing the functions will vary. There should always be one person in command of an operation. This is the foundation of creating accountability and organization, which are the keys to efficiency and safety. The incident commander assesses the incident, activates resources, determines the strategy, and approves the plan for the operation. This may be particularly challenging in jurisdictions where the cave rescue experts are not the same individuals as the emergency response experts. Preplanning and relationships developed in advance are the best solution for preventing problems in this area. Other functions vital to success are planning, operations, logistics, and finance. The incident commander may have one or more people to assist, or he or she may be responsible for several of these functions. Someone must plan strategies, supervise the operation, take care of the physical needs of the rescuers and required equipment, and track the resources used.

Cave Access Gaining access to the victim is a matter of overcoming an array of obstructions inherent in the cave. Merely to move a few hundred feet through a cave might require rappelling, crawling on one’s belly, squeezing through cracks in the rocks, climbing over large rocks, swimming, and slithering through mud—all of which are quite different experiences when embarked on during a rescue while dragging a vast array of equipment. The total darkness of a cave is limiting to any operation and can be confining to some. Even this simple matter can quickly become a major obstacle, particularly if noncavers are called on to assist in medical or other aspects of the operation. Psycho-

logical inhibitions, such as fear of the dark or confined spaces, can cause panic and severe dysfunctional behavior. In no case should a would-be rescuer ever be pushed beyond his or her comfort level. Other factors inherent to the cave rescue operation include temperature variables, wetness, and restrictive cave passages. Certain large or weak people or bulky and heavy equipment might be physically incapable of getting through these tight spaces. These considerations exemplify why it is best for any medical or other rescue person who may eventually become involved in a cave rescue to gain knowledge and experience in advance. If the cave rescue requires raising or lowering a victim, or traversing the victim over horizontal rope lines, people skilled in cave rigging should be responsible for building the systems. Rigging in caves is an art because of anchoring difficulties, directional changes, tight squeezes, and minimal working surface. Details on cave rigging and professional training can be acquired through the National Cave Rescue Commission, a nonprofit organization that teaches courses in cave rescue techniques and management. Many vertical drops in caves are overhung at the top, preventing the rescuer access to a wall while descending and ascending the rope or moving the patient. In cases in which the roped drop has the rope running against a wall, it can be advantageous to place anchors at points throughout the length of the drop. This “re-belay” method allows multiple people to ascend or descend simultaneously, lessens rope wear points, and provides the added safety of having a shorter rope length to protect for each anchor. Practice at crossing re-belays is essential before attempting to enter a cave thus rigged. The caver must be able to effectively transfer from one free-hanging rope to another while hanging in midair. This is easy to do with the correct equipment setup and practice, but not so easy when the technique is tried for the first time underground on the way to a medical emergency. Usually, single-rope techniques are used, especially where a long free-hanging drop is involved. This means that just one rope is put over the side for the rescuer to ascend or descend. The use of an additional belay line not only requires additional people but also might prove more hazardous if the two lines become entangled. In the United States, the most common cave ascending systems are the frog system, Mitchell system, and various renditions of the ropewalker system. These are all efficient means of ascending and can easily be mastered with practice. The frog system requires more climbing effort but is easier to use when ascending past re-belays in the system. It is imperative that an ascending system be fitted to the user. Some rigs work better for tall, lean frames, and others work best for heavier body types. All rescue personnel entering a vertical cave should have their own personally fitted rope climbing system and must have practiced climbing in that system in a safe practice area. Large holes or boulder slopes inside the cave may best be negotiated by using a highline traverse. Highlines can be time and equipment intensive to set up properly but can shave away hours of litter movement time by passing above difficult cave terrain that otherwise would present many challenges for a litter carried by hand. Use of a highline is most practical when it is known in advance that there will be sufficient time for rigging. The decision to take the time to rig a highline traverse should

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be made based on three factors: the time it will take to move the victim to the obstacle you want to be traversed, the time necessary to rig the highline, and the time that will be saved by using the highline to move the victim over the obstacle.

Environmental Hazards One often-overlooked hazard to cavers is the ambient atmosphere. Most caves in the United States breathe naturally either from changes in barometric pressure or from the chimney effect of multiple entrances. When this airflow is interrupted, limited, or polluted in some way, the resulting air can become hazardous to entrants. The most basic type of atmospheric hazard is lack of oxygen. Some caves have small rooms with so little airflow that a few cavers can quickly consume most of the oxygen. While frightening, this type of atmospheric hazard is usually quickly recognized as open flame headlamps sputter or cavers become short of breath. Once recognized, the hazard can be mitigated by avoiding panic, controlling air consumption, and relocating to a friendlier part of the cave. Another type of atmospheric hazard involves buildup of gases such as carbon monoxide, carbon dioxide, methane, and hydrogen sulfide. This can happen as a result of natural metabolism of organics or through external influences. Instances of gasoline seeping into caves from underground storage tanks have been recorded. If poor air quality is suspected, use of an airmonitoring device is essential. It is possible to enter a cave containing high levels of unhealthy gases, but only with appropriate caution. In such cases, it is advisable to solicit participation of the local hazardous materials emergency response team. With the assistance of a hazardous materials or confined space rescue team, “bad air” in caves can be mitigated in several ways. One way is to release compressed air into the cave, forcing good air in and bad air out. Success of this method is limited, and because of the massive amounts of air in a cave, this method is slow at best. If this method is used, entrants should carry an air monitor because pockets of bad air may remain trapped in parts of the cave. The concept of simply releasing oxygen into the cave is a nice idea, but impractical in all but the smallest of spaces. Exhaust fans offer a reasonable method, although care must be taken to prevent generator exhaust from entering the cave. If necessary, rescuers can be equipped for entry with surfacesupplied air with bail-out bottles, self-contained breathing apparatus, or rebreathers. Each of these has advantages and disadvantages, but all are difficult to manage in the cave environment and thus should be avoided if possible. Pre-event training and practice in the safe use of any of this equipment is imperative before entering an atmosphere that is hazardous for breathing. Other airborne hazards, such as histoplasmosis and rabies, are not detectable by air monitor. Histoplasmosis is a human fungal disease that may be contracted by inhalation of organisms found in bird droppings and bat guano. The fungus is a potential inhalation hazard in any cave, but particularly in caves largely populated by bats. Frequent, mild exposure can actually result in strengthening of the immune system against the disease, but a severe case can be deadly. Pulmonary histoplasmosis generally presents with flu-like symptoms within 2 to 4 weeks of exposure and may require hospitalization. Left untreated, histoplasmosis can destroy the lungs and result in death within years or even months.

Figure 40-8. Recreational caver in wet pit. (Photo courtesy Kris H. Green.)

Rabies is also a recognized hazard for cavers who enter caves with large bat colonies. Although actual risk for infection is considered minimal unless the caver is frequently handling bats (which is generally frowned on anyway), immunization against rabies is available and advisable for cave biologists and other scientists who run a high risk for being bitten. In any rescue situation, atmospheric hazards should be considered before entering a cave. If suspected, no rescuer should enter the environment without an appropriate filter mask and other personal protective equipment. Other environmental hazards posed by caves may be more readily recognized and should also be considered before any rescue. As previously discussed, water and caves are usually closely associated. Created by water, caves are a natural deposit for overflow or drainage from a variety of sources. This makes caves particularly prone to flooding with little or no warning. A recreational caver (Fig. 40-8) or rescuer caught in a flooding cave is in mortal danger. Flooding is usually associated with heavy rains, which can cause diffuse seepage over a large area of the cave or a high flow into sinkholes. Occasionally, sinking streams can carry floodwater. In some parts of the world, entire rivers disappear underground, flow through caves, and resurface miles away. A flood crest from many miles upstream can pass through these caves without warning. Flood-prone caves are generally identifiable by their makeup. Cave walls coated with thick mud can be an indication that flooding is not unusual in that section of the cave, and extra caution is warranted. Bedrock cave walls with gravel deposits at key points in the cave and debris lodged in the ceiling can also be warning signs. Becoming trapped in a flooding cave is not desirable, but it can be survivable. If possible, find a high point in a wide passage, downstream of any major constriction, and wait out the flood. It is also possible, with enough advance warning, to remove a sediment dam downstream that may otherwise cause water to back up into your “safety zone.” It is seldom wise to attempt to swim, either upstream or down. For a rescuer called to assist cavers trapped in a flooded cave, entering the torrent is not wise. If the location of the trapped victims is known, it may be possible to use (or make) another

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entrance from which to evacuate them. Knowledgable local cavers can be a valuable asset in this instance. If entry into a flooded cave through the main entrance is absolutely necessary, it is imperative that the water level be controlled before entry. Methods of accomplishing this goal vary depending on the situation. Often, it may be enough to simply wait out the flood and let the water level subside naturally. If the water level is still on the rise, however, or if the source remains constant, additional measures may be warranted. Keep in mind that water is a powerful force, and any plan should be engineered by professionals. One of the simplest diversion methods is to broaden the flood crest so that less of it flows into the cave. Water can be diverted using sandbags, hay bales, or dirt or by digging channels. If this is not possible or feasible, one may be able to lower the water level by digging through debris downstream, thereby expediting the exit. Pumping is also an option, although the hazards inherent in this method should be evaluated closely beforehand. Pumps run on fuel or electricity. Fumes from fuel-driven pumps and generators have entered caves and poisoned the air of the cavers waiting for rescue. Electrical power in a flooded cave situation adds a high risk for electrocution to the operation. Failure of the pumps after rescuers enter a cave can trap additional people if the water can rise again. Entering a flooded cave with scuba equipment is a dangerous, last-resort method that should only be attempted by certified cave divers. A scuba entry may be justified if cavers are known to have been entrapped for an extended period of time, if there is a known medical emergency, or if the cave is completely flooded. In these cases, it may be advisable for certified cave divers to enter and assess the condition of entrapped people, transport survival supplies, or provide medical assistance. Even certified cave divers require additional skills and equipment to enter a recently flooded or sumped cave passage, compared with the typical sport cave dive. Flooded cave passage may have little to no visibility, currents, and debris blocking the passage. Only in the most dire circumstance is it justified to attempt to transport a victim through a flooded passage. At a minimum, a scuba entry requires two to three divers, as well as a backup diver. Diving is gear intensive and requires an air compressor, extra tanks, 110-volt electricity to charge dive lights, underwater communications equipment, waterproof bags, full face masks for subjects, water rescue suits, underwater lights, transport cases, and surface personnel to assist with transporting equipment.

Victim Care As with many remote accidents, the time it takes to report, respond to, and access a caving accident usually means that the victim, if alive, is relatively stable. Although this generalization has exceptions, the treatment issues faced by most rescuers are related to extended transportation times. Data compiled for American Caving Accidents indicate that the leading cause of caving injury is falls, and that hypothermia, fractures, and head injuries top the list of complaints. Unfortunately, spinal injury is invariably present, and this can compound the transportation challenge. The approach to medical care should be similar to any other medical situation, with one notable difference: the victim has suffered an acute injury but will be confined for transport for an extended period. Care, then, will be a combination of acute emergency responses adapted for a victim who is, for all practical purposes, bedridden.

Figure 40-9. Monitoring patient as litter moves. (Photo courtesy Kris H. Green.)

Once the victim has been stabilized and packaged, the assessment process should continue throughout the evacuation. It is best if one medical person stays with and monitors the victim throughout the evacuation (Fig. 40-9). Hypovolemia is a common complaint, so establishing an IV line early in the intervention can be useful. Take measures to ensure that rescuers will be able to maintain IV access and manage the supplies throughout the evacuation, and infuse only fluids not contraindicated for head or other injury. If the victim is alert and oriented, fluid administration will increase the need to urinate, so take this into consideration. As best as possible, maintain communication with the victim, encouraging him or her to flex muscles to maintain good circulation. Allow the victim to assist in care as much as possible. Availability of ALS and drug therapy is useful on extended transports, so it is helpful to have strong rapport with the local medical authorities should complex treatment become necessary.


CONCLUSION Never underestimate a cave rescue. Caves are unique environments, and entry should not be attempted without appropriate technical training and preparation. The advantage to any rescue group of establishing a good working relationship with local cave rescue resources, as well as local recreational cavers, cannot be overemphasized. These are the people with knowledge of the caves; with the training, equipment, and experience to handle the obstacles and the environment; and who already feel at ease underground. They could prove to be your most valuable resource for a successful cave rescue. Many cavers have taken extensive training in cave rescue techniques and are members of organized cave and cliff rescue

Chapter 40: Caving and Cave Rescue teams. The first step to finding cavers is to contact a local chapter, or “grotto,” of the National Speleological Society, the largest cave exploration, education, and science-oriented organization in the United States. Contact them at: National Speleological Society 2813 Cave Avenue Huntsville, AL 35810 [email protected] http://www.caves.org/ Given the unique underground environmental and topographic conditions, nothing can replace formal training in cave rescue techniques and specific cave rescue problems and solutions. People interested in enhancing their training should get in touch with the National Cave Rescue Commission (NCRC).

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The NCRC conducts week-long cave rescue seminars and weekend orientations across the United States. Contact them at the address above as the National Cave Rescue Commission of the National Speleological Society or at www.caves.org/io/ncrc/.


SUGGESTED READINGS Hudson S (ed): Manual of U.S. cave rescue techniques, 2nd ed. Huntsville, AL, National Speleological Society, 1988. Putnam W (ed): American caving accidents. Huntsville, AL, National Speleological Society, published annually. The references for this chapter can be found on the accompanying DVD-ROM.

41

Protection from BloodFeeding Arthropods Mark S. Fradin

Of all the hazards, large and small, that may befall the outdoor enthusiast, perhaps the most vexatious comes from the smallest perils—blood-feeding arthropods. Mosquitoes, flies, fleas, mites, midges, chiggers, and ticks all readily bite humans. The bites are, at best, only a minor annoyance; at worst, arthropod bites may transmit to humans multiple bacterial, viral, protozoal, parasitic, and rickettsial infections (Box 41-1). Mosquitotransmitted diseases alone will be responsible for the deaths of one out of every 17 people currently alive.129 This chapter reviews the arthropod species that bite humans and discusses various options for personal protection against nefarious insects.

Mosquitoes (Family Culicidae) Mosquitoes are responsible for more arthropod bites than any other blood-sucking organism. They can be found all over the world, except in Antarctica. These two-winged insects belong to the order Diptera. There are 170 species of mosquitoes in North America, and over 3000 species worldwide. Anopheline, or malaria-transmitting, mosquitoes can be distinguished by their resting position on the skin—their bodies are characteristically raised high, as if they are standing on their heads. Most other species, in contrast, rest with their bodies parallel to the skin surface (Fig. 41-1A). Mosquitoes vector more diseases to humans than any other blood-feeding arthropod. They transmit malaria to 300 to 500 million people each year, resulting in as many as 3 million deaths per year.119 They vector multiple arboviruses to humans, including several forms of encephalitis, epidemic polyarthritis, yellow fever, and dengue fever (see Chapter 42). Mosquitoes also transmit the larval form of the nematode that causes lymphatic filariasis. Only female mosquitoes bite, requiring a blood-protein meal for egg production. Male mosquitoes feed solely on plant juices and flower nectar. Mosquitoes feed every 3 to 4 days, consuming up to their own weight in blood with each feeding. Certain species of mosquitoes prefer to feed at twilight or nighttime; others (such as the aggressive Asian tiger mosquito, Aedes albopictus) bite mostly during the day. Some mosquito species are zoophilic (preferring to feed on animals, including birds, reptiles, mammals, and amphibians), whereas others are anthropophilic (preferring human blood). Members of the genera Anopheles, Culex, and Aedes are the most common biters of humans. In some mosquitoes, seasonal switching of hosts provides a mechanism for transmitting disease from animal to human.

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Mosquitoes rely on visual, thermal, and olfactory stimuli to help them locate a bloodmeal.10,11,19,25,45,61 For mosquitoes that feed during the daytime, host movement and dark-colored clothing may initiate orientation toward an individual. Visual stimuli appear to be important for in-flight orientation, particularly over long ranges, whereas olfactory stimuli become more important as a mosquito nears its host. Carbon dioxide and lactic acid are the best-studied attractants. Carbon dioxide serves as a long-range attractant, luring mosquitoes at distances of up to 36 meters (118 feet).43,44,122 At close range, skin warmth and moisture serve as attractants.10,19 Volatile compounds, derived from sebum, eccrine and apocrine sweat, and/or the cutaneous microflora bacterial action on these secretions, may also act as chemoattractants.51,68,84,115 Floral fragrances found in perfumes, lotions, soaps, and hair-care products can also lure mosquitoes.36 One study has shown that alcohol ingestion increases the likelihood of being bitten by mosquitoes.120 There can be significant variability in the attractiveness of different individuals to the same or different species of mosquitoes.22,62 Men tend to be bitten more readily than women, and adults are more likely to be bitten than children.62,90 Heavyset people are more likely to attract mosquitoes, perhaps because of their greater relative heat or carbon dioxide output.103 During the day, mosquitoes tend to rest in cool, dark areas, such as on dense vegetation, or in hollow tree stumps, animal burrows, and caves. To complete their life cycle, mosquitoes also require standing water, which may be found in tree holes, woodland pools, marshes, or puddles. To minimize the chance of being bitten by mosquitoes, campsites should be situated as far away from these sites as possible.

Blackflies (Family Simuliidae) At 2 to 5 mm in length, blackflies7,14,29,46,60 (see Figure 41-1B) are smaller than mosquitoes. They have short antennae, stout humpbacked bodies, and broad wings. Blackflies are found worldwide. The adults are most prevalent in late spring and early summer and are most likely encountered near fastrunning, clear rivers or streams, which they require to complete their life cycle. Unlike most mosquitoes, blackflies tend to bite during the daytime. They primarily use visual cues to locate a host. Dark moving objects are particularly attractive, but carbon dioxide and body warmth also serve as attractants. Only the female bites, taking up to 5 minutes to feed. Blackflies may be present in swarms, inflicting numerous bites on their victims. Blackflies are attracted to the eyes, nostrils, and ears of their hosts. They often crawl under clothing or into the hair to feed.

Chapter 41: Protection from Blood-Feeding Arthropods

Box 41-1. Diseases Transmitted to Humans by Biting Arthropods MOSQUITOES

Eastern equine encephalitis* Western equine encephalitis* St. Louis encephalitis* La Cross encephalitis* West Nile virus* Japanese encephalitis Venezuelan equine encephalitis Malaria Yellow fever Dengue fever Bancroftian filariasis Epidemic polyarthritis (Ross River virus) Chikungunya fever Rift Valley fever TICKS

Lyme disease* Rocky Mountain spotted fever* Colorado tick fever* Relapsing fever* Ehrlichiosis* Babesiosis* Tularemia* Tick paralysis* Rickettsial pox* Tick typhus Southern tick-associated rash illness (STARI)

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urticaria, anaphylaxis, and even death, have been reported following blackfly bites. Although these flies are not known to transmit disease to humans in North America, blackflies in the tropics are vectors of the parasite Onchocerca volvulus, which causes river blindness.

Midges (Family Ceratopogonidae) Also known as no-see-ums, sand gnats, sand fleas, and “flying teeth,” biting midges7,14,29,46,60 are small, slender flies (less than 2 mm) with narrow wings (see Figure 41-1C). Their small size makes them difficult to see, and they can pass readily through common window screens. Biting midges are found worldwide. They breed most commonly in salt marshes but may also be found in freshwater wetlands. Despite their inconspicuous size, female midges are aggressive biters, frequently attacking in swarms and inflicting multiple painful and pruritic bites within minutes. Midges often crawl into the hair before biting. Depending on the species, midges may bite during the day or at night. Their activity is greatest during calm weather, declining as wind speed increases. Biting midges are not known to transmit disease in North America.

Tabanids (Family Tabanidae)

CHIGGER MITES

The family Tabanidae (see Figure 41-1D) includes horseflies, deerflies, greenheads, and yellow flies.7,14,29,46,60 These insects are relatively large (10 to 20 mm) robust fliers, with numerous species worldwide. Tabanids breed in aquatic or semi-aquatic environments and have a life cycle of over a year. They can fly for miles and rely primarily on vision to locate a host by movement. These flies are most active on warm, overcast days. Only the females bite, using scissorlike mouthparts to create a bleeding slash in the skin that is slow to heal. Despite their size, these flies usually bite painlessly, but the resulting reaction can include intense itching, secondary infection, and, rarely, systemic reactions such as urticaria or anaphylaxis. Because the adult fly usually lives only about a month, and only one generation emerges per year, the potential season for being bitten is fortunately relatively short. In the United States, deerflies have been shown to be capable of transmitting tularemia to humans; in Africa, the deerfly may vector the filarial parasitic worm Loa loa.

Scrub typhus (tsutsugamushi fever) Rickettsial pox*

Sand Flies (Family Psychodidae)

FLIES

Tularemia* Leishmaniasis* African trypanosomiasis (sleeping sickness) Onchocerciasis Bartonellosis Loiasis

FLEAS

Plague* Murine (endemic) typhus LICE

Epidemic typhus Relapsing fever KISSING BUGS

American trypanosomiasis (Chagas’ disease) *May be found in the United States.

Sand flies7,14,29,32,46,60 are tiny (2 to 3 mm), hairy, and long-legged flies, with multisegmented antennae and a characteristic V shape to the wings when at rest (see Figure 41-1E). Only female sand flies are blood feeders, and they feed mostly during calm, windless nights, and rest during the day in animal burrows, tree holes, or caves. Most sand fly bites tend to occur on the face and neck. In tropical and subtropical climates, sand flies have been shown to vector multiple cutaneous, mucocutaneous, and systemic diseases, including bartonellosis and three forms of leishmaniasis. The only sand fly-transmitted disease in the United States has been cutaneous leishmaniasis, reported in Texas.

Tsetse Flies (Family Glossinidae) The insect’s mouthparts are used to tear the skin surface, producing a pool of blood from which the fly feeds. Blood loss from the bite site often persists after the blackfly has departed. The resulting intensely pruritic, painful, and edematous papules are typically slow to heal. Rare systemic reactions, including fever,

Tsetse flies7,14,29,46,60 are found only in tropical Africa. They are 7 to 14 mm long, yellowish brown, and with wings that fold over their backs, giving them the appearance of honeybees at rest (see Figure 41-1F). Both sexes bite, feeding in daytime on a wide variety of mammals, including humans. Tsetse flies seem

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B

A

C

Figure 41-1. Blood-feeding arthropods. A, Mosquito: Culex and Anopheles. B, Blackfly. C, Biting midge.

to rely primarily on vision and movement to identify their hosts. Their bites may cause petechiae or pruritic wheals. Tsetse flies vector African trypanosomiasis (sleeping sickness).

Trypanosoma cruzi, the causative agent of Chagas’ disease, which has been reported in Central and South America, as well as in the southwestern United States.

Stable Flies (Family Muscidae)

Fleas (Family Pulicidae)

Stable flies46,60 resemble common houseflies and are most often encountered in coastal areas. Unlike a housefly, which rests with its body parallel to the surface, a stable fly rests with its head held higher than its posterior (see Figure 41-1G). Both male and female stable flies are vicious daytime biters, requiring a blood meal every 48 hours to survive. If disturbed, they will attempt to feed multiple times, preferring to bite the lower extremities. Horses and cattle are the preferred hosts, but hungry stable flies will readily bite humans. These flies have knifelike mouthparts that they use to puncture flesh before pumping up the blood. Stable flies breed in decaying vegetation and in herbivore manure and are frequently found congregated on sunny walls. Their bites are generally self-limited. They are not known to transmit disease to humans.

Adult fleas7,14,29,46,60 are small (2 to 6 mm), wingless insects, with 3 pairs of powerful legs that enable them to jump distances of up to 30 cm (see Figure 41-1I). Hungry fleas of both sexes feed on the nearest warm-blooded animal, without clear host preference. Fleas usually move around, probing and biting several times, resulting in grouped lesions of pruritic papules. Fleas are capable of transmitting sylvatic plague and murine typhus.

Kissing Bugs (Family Reduviidae) Kissing bugs7,14,29,33,46,60 (assassin bugs) are large (10 to 30 mm in length) insects with cone-shaped heads, overlapping wings, and an alternating pattern of orange and dark brown stripes on the lateral abdomen (see Figure 41-1H). They get their name from a tendency to bite around the human mouth, but they may also bite other parts of the body. Both male and female reduviids bite, requiring a blood meal to mature through five nymphal growth stages. Reduviids are nocturnal feeders, attracted to their hosts by warmth, carbon dioxide, and odor. During the day, they rest in trees or indoors in crevices of house walls and ceilings. Their bites are initially painless, but frequent exposure to the bites can produce erythema, edema, and pruritus at the bite sites. More importantly, kissing bugs are the vector for

Chigger Mites (Family Trombiculidae) Trombiculid mites7,14,29,46,60 (see Figure 41-1J) are found worldwide. Commonly known as chiggers, redbugs, or harvest mites, these reddish yellow insects are readily encountered in damp, grassy, and wooded areas, especially along the margins of forests, where they may number in the thousands. Only the tiny (less than 0.2 mm) larval stages are parasitic, feeding on mammals, birds, reptiles, and amphibians. Chiggers are most active in the summer and early autumn. They usually infest humans by crawling up the shoes and legs, preferring to attach to skin at areas where the clothing fits tightly, such as at the top of socks or around the elastic edges of underwear. Chiggers do not burrow into the skin or actively suck blood. Rather, they pierce skin with their mouthparts and secrete a proteolytic salivary fluid that dissolves host tissue, which they then suck up. If undisturbed, chiggers may feed for several days before dropping off. In humans, this rarely occurs, because the larvae usually cause enough irritation that they are dislodged by scratching. The host response to chigger bites is brisk, often leading to intensely pruritic, bright red, 1- to 2-cm nodules. In Asia,

E

D

G F

I

J H

K

L

Figure 41-1, cont’d. D, Tabanid fly. E, Sand fly. F, Tsetse fly. G, Stable fly. H, Kissing bug. I, Flea. J, Chigger mite. K, Hard tick. L, Soft tick.

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chiggers may serve as vectors of scrub typhus. Rickettsial pox is also transmitted by a mite bite.

ovarial transmission also enables female ticks to directly infect their offspring.

Ticks (Families Ixodidae and Argasidae)


PERSONAL PROTECTION

(See Chapter 33) Ticks7,14,29,46,60,125 are classified as hard ticks (family Ixodidae) and soft ticks (family Argasidae) (see Figure 41-1K and L). Hard ticks are so named because of the presence of a sclerotized plate, or scutum, that covers part of the body. Both types of ticks are found worldwide, but hard ticks are more commonly encountered in North America. Hard ticks are usually found in weedy or shrubby areas, along trails, and at forest boundaries, where mammalian hosts, such as deer, are plentiful. Soft ticks are more resistant to desiccation than are hard ticks. Soft ticks thrive in hot and dry climates and are commonly found in animal burrows or caves. Both sexes are bloodsuckers. Soft ticks are nocturnal and feed rapidly, finishing in just a few minutes. Hard ticks most commonly feed during the day and may feed on a single host for days. Ticks are unable to fly or jump. Hard ticks climb vegetation and “quest,” waiting passively for hours or days, forelegs outstretched, until they detect the vibration or carbon dioxide plume of a passing host. When they encounter fur or skin, they climb onto the host and then crawl around in search of an appropriate location on which to attach and feed. The attachment bite is usually painless. People in suspected tick habitats should check clothing frequently for the presence of ticks. If multiple ticks are seen on clothing, they are most easily removed by trapping them on a piece of cellophane tape, or by rolling a sticky tape–type lint remover across them; hundreds of small ticks can be easily removed by this method. Laundering infested garments cannot be relied on to kill nymphs unless the clothing is subjected to the hot cycle of the dryer.15 Attached ticks are more difficult to remove. Tick mouthparts are barbed, and some species of tick also secrete a cement that firmly anchors the tick into the skin. Erythema, pruritus, and edema are commonly seen at the site of a tick bite. Improper partial removal of the mouthparts may initiate a long-lasting foreign-body reaction, leading to secondarily infected lesions that are slow to heal, or to granuloma formation that may persist for months. (For a discussion of the best method for tick removal, see Chapter 45.) After the tick is removed, the bite site should be cleansed with soap and water, or with an antiseptic, and hands should be washed. It may be prudent to save the tick, in case later identification becomes necessary. Laboratory studies of ticks infected with Borrelia burgdorferi (the cause of Lyme disease) showed that duration of attachment was directly correlated with the risk of transmission of the spirochete.98,99,101,102,124,125 Prompt removal of attached ticks (ideally within 24 hours of attachment) greatly reduces the likelihood of disease transmission.100 In the United States, soft ticks of the single genus Ornithodoros are capable of transmitting to humans the Borrelia spirochete that causes relapsing fever. Three genera of the hard ticks Ixodidae transmit disease to man: Ixodes (vectors of Lyme disease, babesiosis, and tick paralysis), Dermacentor (vectors of tularemia, Rocky Mountain spotted fever, ehrlichiosis, Colorado tick fever, and tick paralysis), and Amblyomma (vectors of tularemia, ehrlichiosis, southern tick-associated rash illness (STARI) and tick paralysis).87,125 Larval, nymph, and adult ticks can all transmit disease during feeding. Trans-

Personal protection against insect bites can be achieved in three ways: by avoiding infested habitats, by using protective clothing and shelters, and by applying insect repellents.

Habitat Avoidance Avoiding infested habitats reduces the risk of being bitten. Mosquitoes and other nocturnal bloodsuckers are particularly active at dusk, making this a good time to be indoors. To avoid the usual resting places of biting arthropods, campgrounds should be situated in areas that are high, dry, and open, and as free from vegetation as possible. Areas with standing or stagnant water should be avoided, as these are ideal breeding grounds for mosquitoes. Attempts should be made to avoid unnecessary use of lights, which attract many insects.

Physical Protection Physical barriers can be extremely effective in preventing insect bites, by blocking arthropods’ access to the skin. Long-sleeved shirts, socks, long pants, and a hat will protect all but the face, neck, and hands. Tucking pants into the socks or boots makes it much more difficult for ticks or chigger mites to gain access to the skin. Light-colored clothing is preferable, because it makes it easier to spot ticks, and it is less attractive to mosquitoes and biting flies. Ticks will find it more difficult to cling to smooth, tightly woven fabrics (e.g., nylon).118 Loose-fitting clothing, made out of tightly woven fabric, with a tucked-in Tshirt undergarment is particularly effective at reducing bites on the upper body. A light-colored, full-brimmed hat will protect the head and neck. Deerflies tend to land on the hat instead of the head; blackflies and biting midges are less likely to crawl to the shaded skin beneath the brim. Mesh garments or garments made of tightly woven material are available to protect against insect bites. Head nets, hooded jackets, pants, and mittens are available from a number of manufacturers in a wide range of sizes and styles (Box 41-2). Mesh garments are usually made of either polyester or nylon and, depending on the manufacturer, are available in either white or dark colors. With a mesh size of less than 0.3 mm, many of these garments are woven tightly enough to exclude even biting midges and ticks. As with any clothing, bending or crouching may still pull the garments close enough to the skin surface to enable insects to bite through. One manufacturer (Shannon Outdoors, Louisville, GA) addresses this potential problem with a double-layered mesh that reportedly prevents mosquito penetration. Although mesh garments are effective barriers against insects, some people may find them uncomfortable during vigorous activity or in hot weather. Lightweight insect nets and mesh shelters are available to protect travelers sleeping indoors or in the wilderness (Fig. 41-2). Their effectiveness may be enhanced by treating them with a permethrin-based contact insecticide, which can provide weeks of efficacy after a single application.

Repellents For many people, applying an insect repellent may be the most effective and easiest way to prevent arthropod bites. Development of the perfect insect repellent has been a scientific goal for

Chapter 41: Protection from Blood-Feeding Arthropods

Box 41-2. Manufacturers of Protective Clothing, Protective Shelters, and Insect Nets PROTECTIVE CLOTHING*

Bug Baffler, Inc. P.O. Box 444 Goffstown, NH 03045 (800) 662-8411 www.bugbaffler.com Insect Out P.O. Box 49643 Colorado Springs, CO 80949 (888) 488-0285 www.insectout.com BugOut Outdoor Wear, Inc. P.O. Box 185 Centerville, IA 52544 (877) 928-4688 www.bug-out-outdoorwear.com Buzz Off Insect Repellent Apparel (Nonmesh clothing impregnated with permethrin) 701 Green Valley Rd, Suite 302 Greensboro, NC 27408 (336) 272-4157 www.buzzoff.com The Original Bug Shirt Company 908 Niagara Falls Blvd, #467 North Tonawanda, NY 14120 (800) 998-9096 www.bugshirt.com Shannon Outdoor’s Bug Tamer 1210-A Peachtree St Louisville, GA 30434 (800) 852-8058 www.bugtamer.com PROTECTIVE SHELTERS AND INSECT NETS

Long Road Travel Supplies 111 Avenida Dr Berkeley, CA 94708 (800) 359-6040 www.longroad.com Travel Medicine, Inc. 369 Pleasant St Northampton, MA 01060 (800) 872-8633 www.travmed.com Wisconsin Pharmacal Co. 1 Repel Rd Jackson, WI 53037 (800) 558-6614 www.pharmacalway.com *Clothing includes hooded jackets, pants, head nets, ankle guards, gaiters, and mittens.

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years and has yet to be achieved. The ideal agent would repel multiple species of biting arthropods, remain effective for at least 8 hours, cause no irritation to skin or mucous membranes, and possess no systemic toxicity, and it would be resistant to abrasion, greaseless, odorless, and not easily washed off. No presently available insect repellent meets all of these criteria. Efforts to find such a compound have been hampered by the many variables that affect the inherent repellency of any chemical. Repellents do not all share a single mode of action, and different species of insects may react differently to the same repellent.108 To be effective as an insect repellent, a chemical must be volatile enough to maintain an effective repellent vapor concentration at the skin surface, but it must not evaporate so rapidly that it quickly loses its effectiveness. Multiple factors play a role in effectiveness, including concentration, frequency and uniformity of application, the user’s activity level and overall attractiveness to blood-sucking arthropods, and the number and species of the organisms trying to bite. The effectiveness of any repellent is reduced by abrasion from clothing; by evaporation from and absorption into the skin surface; by its tendency to be washed off via sweat, rain, or water; and by a windy environment.42,62,64,82,83,106 Each 10° C (18° F) increase in ambient temperature can lead to as much as a 50% reduction in protection time.64 Insect repellents do not cloak the user in a chemical veil of protection; any untreated exposed skin can be readily bitten by hungry arthropods.83

Chemical Repellents DEET. N,N-diethyl-3-methylbenzamide (previously called N,Ndiethyl-m-toluamide), or DEET, remains the gold standard of presently available insect repellents. DEET has been registered for use by the general public since 1957. It is a broad-spectrum repellent, effective against many species of crawling and flying insects, including mosquitoes, biting flies, midges, chiggers, fleas, and ticks. The United States Environmental Protection Agency (EPA) estimates that about 30% of the U.S. population uses a DEET-based product every year; worldwide use exceeds 200 million people annually.132,134 Decades of empirical testing of more than 20,000 other compounds has not yet led to the release of a superior repellent.24,58,66,105,111,131 DEET may be applied directly to skin, clothing, mesh insect nets or shelters, window screens, tents, or sleeping bags. Care should be taken to avoid inadvertent contact with plastics (such as watch crystals and glasses frames), rayon, spandex, leather, or painted and varnished surfaces, as DEET may damage these. It does not damage natural fibers like wool and cotton. In the United States, DEET is sold in concentrations from 5% to 100%, in multiple formulations, including lotions, solutions, gels, sprays, roll-ons, and impregnated towelettes (Table 41-1). As a general rule, higher concentrations of DEET provide longer-lasting protection. For most uses, however, there is no need to use the highest concentrations of DEET. Products with 10% to 35% DEET provide adequate protection under most conditions. In fact, most manufacturers, responding to consumer demand, have recently begun to offer a greater variety of low-concentration DEET products, and the vast majority of products now contain DEET concentrations of 40% or less. Persons averse to applying DEET directly to their skin may get long-lasting repellency by applying it only to their clothing. DEET-treated garments, stored in a plastic bag between wearings, maintain their repellency for several weeks.22

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A

B

C

D

Figure 41-2. A to C, Protective shelters. D, Bed net. (A, C, and D courtesy Wisconsin Pharmacal Co.; B courtesy Long Road Travel Supplies.)

Products with a DEET concentration over 35% are probably best reserved for circumstances in which the wearer will be in an environment with a very high density of insects (e.g., a rain forest), where there is a high risk of disease transmission from insect bites, or when there may be rapid loss of repellent from the skin surface, such as under conditions of high temperature and humidity or rain. Under these circumstances, reapplication of the repellent will most likely be necessary to maintain its effectiveness. Sequential application of a DEET-based repellent and a sunscreen can reduce the efficacy of the sunscreen. In a study of 14 patients who applied a 33% DEET repellent followed by a sunscreen with a sun protection factor (SPF) of 15, the sunscreen’s SPF was decreased by a mean of 33%, although the repellent maintained its potency.91 Some products contain a combination of sunscreen and DEET and will deliver the SPF stated on the

label. However, these products are generally not the best choice, as it is rare that the need for reapplication of sunscreen and repellent is exactly the same. Two companies (3M, Minneapolis, MN, and Sawyer Products, Tampa, FL) currently manufacture extended-release formulations of DEET that make it possible to deliver long-lasting protection without relying on high concentrations. The 3M product Ultrathon was originally developed for the U.S. military but is also available to the general public. This acrylate polymer formulation containing 35% DEET, when tested under many different environmental and climatic field conditions, was as effective as 75% DEET, providing up to 12 hours of greater than 95% protection against mosquito bites.2,49,67,88,114,116 Sawyer Products’ controlled-release 20% DEET lotion traps the chemical in a protein particle that slowly releases it to the skin surface, providing repellency equivalent to a standard 50%

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TABLE 41-1. DEET-Containing Insect Repellents MANUFACTURER Sawyer Products Tampa, FL (800) 940-4664 S.C. Johnson Wax Racine, WI (800) 558-5566

Tender Corp. Littleton, NH (800) 258-4696 Spectrum Brands St. Louis, MO (800) 874-8892

3M St. Paul, MN (888) 364-3577

PRODUCT NAME

FORM

DEET (%)

Lotion Aerosol and pump spray

20 25

Sawyer Controlled Release Sawyer Broad Spectrum Insect Repellent (with R-326 fly and gnat repellent) Sawyer Maxi DEET OFF! Skintastic OFF! Skintastic OFF! Skintastic with Sunscreen (SPF 30) OFF! Fresh Scent Deep Woods OFF! Deep Woods OFF! Sportsman DEEP Woods OFF! Sportsman Ben’s Tick and Insect Repellent Ben’s 100 Tick and Insect Repellent

Pump spray Pump spray Pump spray Pump spray Pump spray Aerosol and pump spray Aerosol spray Pump spray Aerosol, pump spray, roll-on Pump spray

100 5 7 10 25 25 30 100 30 95

Cutter All Family Insect Repellent Cutter Skinsations Insect Repellent Cutter Unscented Cutter Backwoods Cutter Backwoods Cutter Outdoorsman Cutter Outdoorsman Cutter Oudoorsman Cutter Tick Defense (with MGK 264 and 326) Cutter Max Repel Camp Lotion for Families Repel Sun and Bug Stuff (SPF 15) Repel Family Formula Repel Sportsman Formula Repel Sportsman Formula Repel Sportsman Formula Repel Sportsman Formula Repel Sportsman Max Formula Repel Hunter’s Repellent with Earth Scent Repel 100% Insect Repellent Ultrathon Ultrathon

Aerosol, pump spray, wipes Pump spray Aerosol spray Aerosol and pump spray Wipes Pump Aerosol Stick and lotion Aerosol spray Pump Lotion Lotion Aerosol spray Lotion Pump spray Aerosol spray Wipes Aerosol spray Pump spray Pump spray Aerosol Lotion

7 7 10 23 30 23 28.5 30 25 100 10 20 23 20 25 29 30 40 55 100 25 35

DEET preparation and lasting about 5 hours.34 Compared with a 20% ethanol-based preparation of DEET, 60% less of this encapsulated DEET is absorbed.20 DEET has been used by millions of people worldwide for 50 years, and it continues to show a remarkable safety profile. In 1980, as part of the U.S. EPA Registration Standard for DEET,132 over 30 additional animal studies were conducted to assess acute, chronic, and subchronic toxicity; mutagenicity; oncogenicity; and developmental, reproductive, and neurologic toxicity. The results of these studies neither led to any product changes to comply with current EPA safety standards nor indicated any new toxicities under normal usage. The EPA’s Reregistration Eligibility Decision (RED),134 released in 1998, confirmed that the Agency believes that “normal use of DEET does not present a health concern to the general U.S. population.” Case reports of potential DEET toxicity exist in the medical literature and have been extensively reviewed.8,38,127,136 Fewer

than 50 cases of significant toxicity from DEET exposure have been documented in the medical literature over the last 4 decades; over three quarters of these resolved without sequelae. Many of these cases involved long-term, excessive, or inappropriate use of DEET repellents; the details of exposure were frequently poorly documented, making causal relationships difficult to establish. These cases have not shown a correlation between the concentration of the DEET product used and the risk of toxicity. The reports of DEET toxicity that raise the greatest concern involve 18 cases of encephalopathy, 14 in children under age 8 years.* Three of these children died; one of them had ornithine carbamoyl transferase deficiency, which might have predisposed her to DEET-induced toxicity.55,56 The other children recovered without sequelae. The EPA’s analysis of these cases concluded that they “do not support a direct link between exposure to *See references 12, 28, 31, 38, 52, 55, 56, 71, 79, 93, 94, 142.

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DEET and seizure incidence.”134 Animal studies in rats and mice show that DEET is not a selective neurotoxin.93,109,132 Even if a link between DEET use and seizures does exist, the observed risk, based on DEET usage patterns, would be less than one per 100 million users.134 Other studies have confirmed that children are not at greater risk for developing adverse effects from DEET when compared with older individuals.8,69,136 Very limited studies have been done investigating the safety of DEET use during pregnancy. One published study followed 450 Thai women who used 20% DEET daily during the second and third trimesters of pregnancy to reduce the risk of contracting malaria.86 Of these women, 4% had detectable levels of DEET in umbilical cord blood at the time of delivery. However, no differences in survival, growth, or neurologic development could be detected in the infants born to mothers who used DEET when compared with an equal number of mothers treated with a daily placebo cream during their pregnancies. The EPA has issued guidelines to ensure safe use of DEETbased repellents134 (Box 41-3). Careful product choice and

Box 41-3. Guidelines for Safe and Effective Use of Insect Repellents • For casual use, choose a repellent with 10% to 35% DEET. Repellents with 10% DEET or less are most appropriate for use on children. • Use just enough repellent to lightly cover the exposed skin; do not saturate the skin. • Repellents should be applied only to exposed skin and clothing. Do not use under clothing. • To apply to the face, dispense into palms, rub hands together, and then apply thin layer to face. • Young children should not apply repellents themselves. • Avoid contact with eyes and mouth. Do not apply to children’s hands, to prevent possible subsequent contact with mucous membranes. • After applying, wipe repellent from the palmar surfaces to prevent inadvertent contact with eyes, mouth, and genitals. • Never use repellents over cuts, wounds, or inflamed, irritated, or eczematous skin. • Do not inhale aerosol formulations or get them in eyes. Do not apply when near food. • Frequent reapplication is rarely necessary, unless the repellent seems to have lost its effectiveness. Reapplication may be necessary in very hot, wet environments because of rapid loss of repellent from the skin surface. • Once inside, wash treated areas with soap and water. Washing the repellent from the skin surface is particularly important when a repellent is likely to be applied for several consecutive days. • If you suspect you are having a reaction to an insect repellent, discontinue its use, wash the treated skin, and consult a physician. Adapted from United States Environmental Protection Agency, Office of Pesticide Programs, Prevention, Pesticides and Toxic Substances Division: Reregistration Eligibility Decision (RED): DEET (EPA-738F-95-010), Washington, DC, 1998, EPA.

common-sense application greatly reduce the possibility of toxicity. The current recommendation of the American Academy of Pediatrics is that children over the age of 2 months can safely use up to 30% DEET.138 When required, reapplication of a low-strength repellent can compensate for the inherent shorter duration of protection. Questions about the safety of DEET may be addressed to the EPA-sponsored National Pesticide Information Center, available every day from 6:30 am to 4:30 pm PST at 800-858-7378, or via their website at http://npic.orst.edu.

IR3535 (Ethyl-Butylacetylaminoproprionate). IR3535 is an analog of the amino acid β-alanine and has been sold in Europe as an insect repellent for 20 years. In the United States, this compound is classified by the EPA as a biopesticide, effective against mosquitoes, ticks, and flies. IR3535 was brought to the U.S. market in 1999, sold exclusively by the Avon Corporation as Skin-So-Soft Bug Guard Plus, with 7.5% IR3535. Depending on the species of mosquito and the testing method, this repellent has demonstrated widely variable effectiveness, with complete protection times ranging from 23 to 360 minutes.5,6,39 In general, IR3535 provides longer-lasting repellency than the botanical citronella-based repellents, but it does not match the overall efficacy of DEET.5,6,39 In 2006, Avon also released a 15% IR3535 spray to the market. Avon’s Skin-So-Soft Bath Oil (Avon, New York, NY) received considerable media attention several years ago when it was reported by some consumers to be effective as a mosquito repellent. When tested under laboratory conditions against Aedes aegypti mosquitoes, Skin-So-Soft Bath Oil’s effective half-life was found to be 0.51 hours.107 In one study against Aedes albopictus, Skin-So-Soft oil provided 0.64 hours of protection from bites, and it was 10 times less effective than was 12.5% DEET.116 Skin-So-Soft oil has been found to be somewhat effective against biting midges, but this effect is felt to be a result of its trapping the insects in an oily film on the skin surface.81 It has been proposed that the limited mosquito repellent effect of Skin-So-Soft oil could result from its fragrance, or from the presence of diisopropyl adipate and benzophenone in the formulation, both of which have some repellent activity.17,66 Picaridin. The piperidine derivative picaridin (also known as KBR2023) is the newest insect repellent to become available in the United States. Picaridin-based insect repellents have been sold in Europe since 1998 under the brand name Bayrepel. In 2005, the first picaridin-based repellent was brought to the market in the United States, as Cutter Advanced, containing 7% of the active ingredient. This nearly odorless, nongreasy repellent is effective against mosquitoes, biting flies, and ticks. The 7% repellent should provide protection for up to 4 hours. Studies have shown that, when used at higher concentrations of up to 20%, picaridin repellents can offer an efficacy comparable to that of DEET,3,26,27,40,123 giving up to 8 hours of protection. The chemical is aesthetically pleasant and, unlike DEET, shows no detrimental effects on contact with plastics. The EPA found picaridin to have a very low toxicity risk. In April 2005, the Centers for Disease Control and Prevention (CDC) released a statement adding picaridin to the list of approved repellents that could be used effectively to prevent mosquito-borne diseases.

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TABLE 41-2. Botanical Insect Repellents MANUFACTURER

PRODUCT NAME

HOMS, LLC Clayton, NC (800) 805-2483 Tender Corp. Littleton, NH (800) 258-4696 All Terrain Co. Encinitas, CA (800) 246-7328

Bite Blocker

Lotion, pump spray

Soybean oil 2%

Natrapel

Lotion, pump spray, roll-on, wipes

Citronella oil 10%

Herbal Armor

Pump spray and lotion Lotion

Citronella oil 12%, peppermint oil 2.5%, cedar oil 2%, lemongrass oil 1%, geranium oil 0.05%, in a slow-release encapsulated formula

Green Ban Norway, IA (319) 446-7495 Quantum Inc. Eugene, OR (800) 448-1448 Kiss My Face Gardiner, NY (800) 262-5477 Lakon Herbals, Inc. Montpelier, VT (800) 865-2566

Herbal Armor Bug & Sun SPF15 Kids Herbal Armor Kids Herbal Armor SPF 15 Green Ban for People: Regular Double Strength Buzz Away Buzz Away, SPF 15

FORM

ACTIVE INGREDIENTS

Pump spray Lotion

Oil Oil Towelettes, pump spray

SunSwat SPF 15

Lotion Lotion

Bygone Bugzz

Lotion

Botanical Repellents Thousands of plants have been tested as sources of insect repellents. Although none of the plant-derived chemicals tested to date demonstrates the broad effectiveness and duration of DEET, a few show repellent activity. Plants with essential oils that have been reported to possess repellent activity include citronella, neem, cedar, verbena, pennyroyal, geranium, catnip, lavender, pine, cajeput, cinnamon, vanilla, rosemary, basil, thyme, allspice, garlic, and peppermint.* Unlike DEET-based repellents, botanical repellents have been relatively poorly studied. When tested, most of these essential oils tended to show short-lasting protection, lasting minutes to 2 hours. A summary of readily available plant-derived insect repellents is shown in Table 41-2.

Citronella. Oil of citronella was initially registered as an insect repellent by the EPA in 1948. It is the most common active ingredient found in “natural” or “herbal” insect repellents presently marketed in the United States. Originally extracted from the grass plant Cymbopogon nardus, oil of citronella has a lemony scent. Conflicting data exist on the efficacy of citronella-based products, varying greatly depending on the study methodology, location, and species of biting insect tested. One citronella-based repellent was found to provide no repellency when tested in the laboratory against Aedes aegypti mosquitoes.17 However, another study of the same product conducted in the field *See references 4, 13, 22, 30, 48, 63, 66, 97, 104, 130.

Citronella oil 5%, peppermint oil 1% Citronella oil 10%, peppermint oil 2% Citronella oil 5%; oils of cedarwood, peppermint, eucalyptus, lemongrass Citronella oil, bay, cedarwood, lavender, vetivert, patchouli, juniper, tea tree, lemon peel, pennyroyal, pansy, goldenseal oils Eucalyptus, rosemary, birch, peppermint and geranium oils

showed an average of 88% repellency over a 2-hour exposure. The product’s effectiveness was greatest within the first 40 minutes after application and then decreased with time over the remainder of the test period.128 All Terrain Company (Encinitas, CA; 800-246-7328) produces a citronella-based lotion in which the essential oil has been encapsulated into a beeswax matrix, which slowly releases it to the skin surface, prolonging its efficacy. In laboratory testing against Aedes aegypti, this product provided complete protection for the first 2 hours, and 77% protection 4 hours after application.53 In general, studies show that citronella-based repellents are less effective than are DEET repellents. Citronella provides a shorter protection time, which may be partially overcome by frequent reapplication of the repellent. In 1997, after analyzing available data on the repellent effect of citronella, the EPA concluded that citronella-based insect repellents must contain the following statement on their labels: “For maximum repellent effectiveness of this product, repeat applications at one hour intervals.”133 Citronella candles have been promoted as an effective way to repel mosquitoes from one’s local environment. One study compared the efficacy of commercially available 3% citronella candles, 5% citronella incense, and plain candles to prevent bites by Aedes species mosquitoes under field conditions.77 Subjects near the citronella candles had 42% fewer bites than controls who had no protection (a statistically significant difference). However, burning ordinary candles reduced the number of bites by 23%. There was no difference in efficacy between citronella incense and plain candles. The ability of

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plain candles to decrease biting may be due to their serving as a decoy source of warmth, moisture, and carbon dioxide. The citrosa plant (Pelargonium citrosum “Van Leenii”) has been marketed as being able to repel mosquitoes through the continuous release of citronella oils. Unfortunately, when tested, these plants offer no protection against bites.18,85

portionately longer complete protection times—up to 6 to 8 hours after a single application. Bite Blocker and oil of eucalyptus repellents appear to be the best of the botanical repellents. Because of its pleasant aesthetic qualities, picaridin repellents may eventually replace DEET as the consumer’s preferred repellent.

Bite Blocker. Bite Blocker is a “natural” repellent that was released to the United States market in 1997. It combines soybean oil, geranium oil, and coconut oil in a formulation that has been available in Europe for several years.135 Studies conducted at the University of Guelph showed that this product was capable of providing over 97% protection against Aedes species mosquitoes under field conditions, even after 3.5 hours of application. During the same period, a 6.65% DEET-based spray afforded 86% protection, whereas Avon’s Skin-So-Soft citronella-based repellent gave only 40% protection.74 A second study showed that Bite Blocker provided a mean of 200 ± 30 (SD) minutes of complete protection from mosquito bites.75 A laboratory study using three different species of mosquitoes showed that Bite Blocker provided an average protection time of about 7 hours.6 Another study showed that it could give about 10 hours of protection against biting black flies; in the same test, 20% DEET protected for only about 6.5 hours.76

Alternative Repellents

Eucalyptus. A derivative (p-menthane-3,8-diol, or PMD) isolated from oil of the lemon eucalyptus plant has a strong lemony scent and has shown promise as an effective “natural” repellent.23 This repellent has been very popular in China for years and is currently sold in Europe as Mosi-Guard and in the United States as Repel Lemon Eucalyptus Repellent (Wisconsin Pharmacal Co., Inc., Jackson, WI) and as FiteBite Plant-Based Insect Repellent (Travel Medicine, Inc., Northampton, MA). Field tests of this repellent have shown mean complete protection times ranging from 4 to 7.5 hours, depending on the mosquito species.6,47,89 PMD-based repellents can cause significant ocular irritation, so care must be taken to keep them away from the eyes. In 2005, the CDC added this repellent to the approved list of products that can be effectively used to prevent mosquitoborne diseases.

Efficacy of DEET versus Botanical Repellents Limited data are available from studies that directly compare plant-derived repellents to DEET-based products. Available data proving the efficacy of “natural” repellents are often sparse, and there is no uniformly accepted standard for testing these products. As a result, different studies often yield varied results, depending on how and where the tests were conducted. Studies comparing “natural” repellents to low-strength DEET products, conducted under carefully controlled laboratory conditions with caged mosquitoes, typically demonstrate dramatic differences in effectiveness between currently marketed insect repellents.39 Citronella-based insect repellents usually provide the shortest-duration protection, often lasting only a few minutes. Low-concentration DEET lotions (under 7%) typically prove to be more effective than citronella-based repellents in their ability to prevent mosquito bites and can generally be expected to provide about 1.5 to 2 hours of complete protection.39,54 Reapplication of these low-concentration DEET products can compensate for their shorter duration of action. Because DEET repellents show a clear dose–response relationship, higher concentrations of DEET can be used to provide pro-

There has always been great interest in finding an oral insect repellent. Oral repellents would be convenient and would eliminate the need to apply creams to the skin or put on protective clothing. Unfortunately, no effective oral repellent has been discovered. For decades, lay literature has made the claim that vitamin B1 (thiamine) works as a systemic mosquito repellent. When subjected to scientific scrutiny, however, thiamine has not been found to have any repellent effect on mosquitoes.65,139 The U.S. Food and Drug Administration (FDA), prompted by misleading consumer advertising, issued the following statement about thiamine in 1983: “There is a lack of adequate data to establish the effectiveness of this, or any other ingredient for OTC [over the counter] oral use as an insect repellent. Labeling claims for OTC orally administered insect repellent drug products are either false, misleading, or unsupported by scientific data.”35 Tests of over 100 ingested drugs, including other vitamins, failed to reveal any that worked well against mosquitoes.126 Ingested garlic has also never proven to be an effective deterrent.

Insecticides Permethrin Pyrethrum is a powerful, rapidly acting insecticide, originally derived from crushed dried flowers of the daisy Chrysanthemum cinerariifolium.16 Permethrin is a synthetic pyrethroid. It does not repel insects but works as a contact insecticide, causing nervous system toxicity, leading to death, or “knockdown,” of the insect. The chemical is effective against mosquitoes, flies, ticks, fleas, lice, and chiggers. Permethrin has low mammalian toxicity, is poorly absorbed by the skin, and is rapidly metabolized by skin and blood esterases.57,141 Permethrin should be applied directly to clothing or to other fabrics (tent walls110 or mosquito nets78), not to skin. Permethrins are nonstaining, are nearly odorless, are resistant to degradation by heat or sun, and maintain their effectiveness for at least 2 weeks, and through several launderings.112,117 The combination of permethrin-treated clothing and skin application of a DEET-based repellent creates a formidable barrier against biting insects.50,67,121 In an Alaskan field trial against mosquitoes, subjects wearing permethrin-treated uniforms and a polymer-based 35% DEET product had greater than 99.9% protection (one bite per hour) over 8 hours; unprotected subjects received an average of 1188 bites per hour.73 Permethrin-sprayed clothing also proved very effective against ticks. One hundred percent of Dermacentor occidentalis ticks (which carry Rocky Mountain spotted fever) died within 3 hours of touching permethrin-treated cloth.70 Permethrinsprayed pants and jackets also provided 100% protection from all three life stages of Ixodes dammini ticks, the vector of Lyme disease.118 In contrast, DEET alone (applied to the skin), provided 85% repellency at the time of application; this protection deteriorated to 55% repellency at 6 hours, when tested against the lone star tick Amblyomma americanum.123 Ixodes scapu-

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TABLE 41-3. Permethrin Insecticides MANUFACTURER Coulston Products Easton, PA (610) 253-0167 Sawyer Products Tampa, FL (800) 940-4464 Spectrum Brands St. Louis, MO (800) 874-8892 3M St. Paul, MN (888) 364-3577

PRODUCT NAME

FORM

ACTIVE INGREDIENT

Duranon Odorless Perma-Kill

Aerosol spray Liquid concentrate

Permethrin 0.5% Permethrin 13.3%

Permethrin Clothing Insect Repellent

Aerosol and pump sprays

Permethrin 0.5%

Repel Permanone Clothing and Gear Insect Repellent

Aerosol spray

Permethrin 0.5%

Clothing and Gear Insect Repellent

Aerosol spray

Permethrin 0.5%

laris ticks, which may transmit Lyme disease, also seem to be less sensitive to the repellent effect of DEET.113 Permethrin-based insecticides available in the United States are listed in Table 41-3. To apply to clothing, spray each side of the fabric (outdoors) for 30 to 45 seconds, just enough to moisten it. Allow it to dry for 2 to 4 hours before wearing it. Permethrin solution is also available for soak-treating large items, such as mesh bed nets, or for treating multiple garments simultaneously. Permethrin-pretreated shirts, pants, socks, and hats can also be purchased. The manufacturer (Buzz Off Insect Shield, Greensboro, NC) claims that they will maintain their insecticidal effect through 25 machine washings.

Reducing Local Mosquito Populations Consumers may still find advertisements for small ultrasonic electronic devices that are meant to be carried on the body and claim to repulse mosquitoes by emitting “repellent” sounds, such as that of a dragonfly (claimed to be the natural enemy of the mosquito), male mosquito, or bat. Multiple studies, conducted in the field and in the laboratory, show that these devices do not work.9,21,37,59,72 Mass-marketed backyard bug zappers, which use ultraviolet light to lure and electrocute insects, are also ineffective: mosquitoes continue to be more attracted to humans than to the devices.92 One backyard study showed that of the insects killed by these devices, only 0.13% were female (biting) mosquitoes.41 An estimated 71 to 350 billion beneficial insects may be killed annually in the United States by these devices.41 Newer technology, utilizing more specific bait, such as a warm, moist plume of carbon dioxide, as well as other known chemical attractants (e.g., octenol), may prove to be a more successful way to lure and selectively kill biting insects. Their manufacturers accurately claim that these machines can lure and kill thousands of mosquitoes, but it remains to be proven that an individual unit can actually kill enough mosquitoes to reduce the local biting pressures. Pyrethrincontaining yard foggers set off prior to an outdoor event can temporarily reduce the number of biting arthropods in a local environment. These products should be applied before any food is brought outside and should be kept away from animals or fish ponds. Burning coils that contain natural pyrethrins or synthetic pyrethroids (such as d-allethrin or d-trans-allethrin) can also temporarily reduce local populations of biting insects.59,80,140 Some concerns have been raised about the cumu-

lative safety of long-term use of these coils in an indoor environment.1,96 Wood smoke from campfires can also reduce the likelihood of being bitten by mosquitoes. The smoke’s ability to repel insects may vary depending on the type of wood or vegetation burned.95,137

Integrated Approach to Personal Protection An integrated approach to personal protection is the most effective way to prevent arthropod bites, regardless of where one is in the world and which species of insects may be attacking. Maximal protection is best achieved through avoiding infested habitats and using protective clothing, topical insect repellents and permethrin-treated garments. When appropriate, mesh bed nets or tents should be used to prevent nocturnal insect bites. DEET-containing insect repellents are the most effective products currently on the U.S. market, providing broad-spectrum, long-lasting repellency against multiple arthropod species. Insect repellents alone, however, should not be relied on to provide complete protection. Mosquitoes, for example, can find and bite any untreated skin and may even bite through thin clothing. Deerflies, biting midges, and some blackflies prefer to bite around the head and readily crawl into the hair to bite where there is no protection. Wearing protective clothing, including a hat, reduces the chances of being bitten. Treating clothes, including the hat, with permethrin maximizes their effectiveness by causing knockdown of any insect that crawls or lands on the treated clothing. To prevent chiggers or ticks from crawling up the legs, pants should be tucked into the boots or stockings. The U.S. military relies on this integrated approach to protect troops deployed in areas where arthropods constitute either a significant nuisance or medical risk. The Department of Defense’s insect repellent system consists of DEET applied to exposed areas of skin, and permethrin-treated uniforms, worn with the pant legs tucked into boots and the undershirt tucked into the pant’s waistband. This system has been proven to dramatically reduce the likelihood of being bitten by insects. Persons traveling to parts of the world where insect-borne disease is a potential threat can protect themselves best if they learn about indigenous insects and the diseases they might transmit. Protective clothing, mesh insect tents or bedding, insect repellent, and permethrin spray should be carried. Travelers would be wise to check the most current CDC recommenda-

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tions about traveling to countries where immunizations (e.g., against yellow fever) or antibiotic prophylaxis (e.g., against malaria) should be undertaken before departure. The CDC maintains these recommendations on its website at www.cdc.gov/travel/index.htm, or by telephone at 888-2323228. An excellent summary of information on issues related to travel health can also be found at www.tripprep.com. This

42

website culls information daily from the CDC, the Morbidity and Mortality Weekly Report, the World Health Organization, and the U.S. State Department.

The references for this chapter can be found on the accompanying DVD-ROM.

Mosquitoes and Mosquito-Borne Diseases Renee Y. Hsia

Mosquitoes are in the biologic phylum Arthropoda, class Insecta, order Diptera, and family Culicidae. There are approximately 35 genera, which include Anopheles, Culex, Psorophora, Ochlerotatus, Aedes, Sabethes, Wyeomyia, Culiseta, and Haemagogus. Worldwide, there are over 3000 species and subspecies, and in the United States alone, there are an estimated 200 different species of mosquitoes that differ in their habitats and behaviors.81 In addition to transmitting the parasitic disease of malaria to 300 to 500 million people per year and thereby killing up to 2.7 million people per year,1 mosquitoes also serve as vectors for arboviruses that cause significant morbidity and mortality to humans worldwide. In addition, mosquitoes are responsible for transmission of the larval nematode that leads to lymphatic filariasis.


MOSQUITOES Mosquitoes (the word is derived from the 16th century Spanish or Portuguese word for little fly) have been in existence for an estimated 170 million years. They are characterized by scaled wings, long legs, and a slender body. The size varies but rarely exceeds 15 mm in length. They weigh approximately 2 to 2.5 mg and can fly at about 0.9 to 1.6 mph.

Mosquito Anatomy Mosquito anatomy (Fig. 42-1) includes a slender body with two wings (rather than the four possessed by flies) and six long, delicate legs. The wings are covered with scales. The body is divided into three parts: head, thorax, and abdomen. The head has two large compound eyes with many lenses angled in different directions, and two antennae. The mouth, or proboscis, looks like a funnel extending downward, and it is used to pierce skin and suck blood (for females) or sip nectar (for males). The thin and short neck connects the head to the thorax, which is triangular and holds the wings in place. The thorax also has two pairs of spiracles, which are tubes through which the mosquito can breathe. The shape of the abdomen can be pointed or

rounded, depending on the species, and it has eight pairs of spiracles. The legs are divided into the coxa, femur, tibia, and tarsus. The spiracles form the basis of the mosquito’s tracheal system, which is finely branched so that the cells of the body are directly oxygenated. Mosquitoes have a dorsal blood vessel that extends directly from the eighth abdominal segment into the head. The heart is the portion of the blood vessel located within the thorax and although it is not innervated, it pulses automatically at a rate of 85 beats per minute.74 The mouthparts of the mosquito include the labrum and the labium, which can be understood as the upper and lower lips of the mosquito, respectively, and the mandible and maxilla are anterior and posterior structures that compose a jawlike configuration. The maxillary palps are small, antenna-like sensory structures that detect chemicals from animals, and the sensory hairs (setae) on the antennae sense vibration and motion from potential prey and other organisms.

Mosquito Life Cycle The life cycle of most species of mosquitoes is defined by four stages: egg, larva, pupa, and adult. The time a mosquito spends in each stage depends on the species and the temperature. Culex tarsalis, for example, has a 14-day life cycle at 20° C (68° F), and a 10-day life cycle at 25° C (77° F). The life cycle varies from 4 days to 1 month, but it averages around 2 weeks, which means that several generations can arise within a single year.81 Most mosquitoes that do not have habitats in the tropics lie dormant as eggs, although some, such as the genus Culex, overwinter as larvae or adults. The female mosquito usually mates once in her lifetime and stores sperm in her body. She fertilizes her eggs when she lays them, which is generally on the surface of the water—often in the form of egg rafts, as shown in Figure 42-2, or sometimes in groups in empty containers or jars, as shown in Figure 42-3. Eggs can survive winter and hatch in the spring. They hatch into larvae (also known as wrigglers), about 1 to 2 cm long, that feed on microscopic animal, plant life, and, in some cases, other

Chapter 42: Mosquitoes and Mosquito-Borne Diseases

Anopheles Mosquito (Adult female) Head Thorax

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Tarsus

Abdomen Tibia

Antenna

Femur

Maxillary Palps Banded abdomen 2 Compound eyes

3 pairs of legs

Proboscis

Figure 42-1. The anatomy of a mosquito.

Figure 42-4. Culex larvae suspended diagonally, with siphons at the surface of the water.

11 m m

Figure 42-5. Pupae, where the eyes, legs, and wings are visible. Figure 42-2. A Culex mosquito “egg raft,” measuring 11 mm in length and composed of 200 to 300 eggs.

mosquito larvae. Except for the genus Anopheles, the larvae must come to the surface to employ their air tubes, or siphons, which supplement their gills (Fig. 42-4). After molting several times, they develop into pupae (Fig. 42-5), floating on the surface of the water and breathing through an air tube, now called a trumpet. While encased in the hard pupal case, they transform into adult mosquitoes. Enough pressure is created to burst the case, and when their wings harden, they can fly and live on land.74

Mechanism of Mosquito Bites

Figure 42-3. Eggs of Aedes aegypti mosquito, which transmits dengue virus.

Mosquitoes technically do not sting, because there is no stinger; they simply pierce the skin and suck blood. Only the females of most species have sucking mouth parts that can pierce skin and thus transmit disease (Fig. 42-6). The blood protein is required because the normal mosquito diet of nectar and fruit juices does not contain enough protein for egg development. (One genus, Toxorhynchites, does not suck blood, and its larvae prey on other mosquito larvae.) Mosquitoes generally identify victims by scent, as well as by the carbon dioxide of exhaled breath and some chemicals found in sweat. Mosquitoes have been shown to have odorant-binding proteins on their antennae that bind

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Figure 42-6. A female Aedes albopictus mosquito (a vector of the West Nile virus) becoming engorged with blood while feeding on a human. Figure 42-7. Urticarial plaque.

human-specific odorants, stimulating their olfactory neurons and allowing them to locate their human prey.71 Other risk factors for getting bitten include male sex, heavier weight, and type O blood.30 When mosquitoes pierce human skin, all six legs are usually positioned on the skin surface, along with the labella (part of the proboscis). The female proboscis is made up of six shafts, four of which cut and pierce skin. One serves as a conduit for blood into the mosquito, and another transports mosquito saliva into the skin. The mosquito lays the labella on the skin, which allows the maxillae of the fascicle (a bundle of feeding stylets, contained within the proboscis) to saw into the skin in an oscillatory cutting fashion. Blood is drawn up into the fascicle, which collects into the labrum held between the mandibles of the mosquito. The female mosquito usually requires about 50 seconds to insert the fascicle into the skin, and approximately 2 minutes to finish feeding. She can withdraw her fascicle in 5 seconds.29,35 The saliva of mosquitoes contains a wide array of antihemostatic molecules that allow feeding of blood. These molecules include vasodilators, such as amines and prostaglandins; platelet aggregation inhibitors, such as nitric oxide, prostaglandins, apyrase, molecules that sequester ADP-sequestering molecules, and peptides and proteins specifically targeted to integrin receptors; and anticoagulants, such as thrombin and factor Xa inhibitors. The saliva and its accompanying proteins (specifically, the 33-kilodalton F-1 protein found in mosquito saliva) that remain in human skin after feeding serve as antigens that evoke an immune response.25

Pathophysiology and Clinical Manifestations of Mosquito Bites Individuals vary in their response to a mosquito bite. Almost all experience local irritation caused by a type I immunoglobulin E (IgE)-mediated response of a soft, pale, pruritic wheal or plaque (Fig. 42-7). The subsequent effects reveal which immune response a person has to the bite. Type I IgE-responses can also create immediate hivelike skin lesions (rare), whereas type IV cell-mediated immunity causes delayed pruritic papules or vesicles within 48 hours of the bite. Other type IV reactions caused

Figure 42-8. Mosquito bite demonstrating papular urticaria.

by mosquito bites include blisters, bullae, and erythema multiforme or purpura, but these are rare. One common type IV hypersensitivity response is papular urticaria, which describes an eruption of pruritic papules measuring 3 to 10 mm in diameter that may be surrounded by vesicles grouped in irregular clusters (Fig. 42-8). Because repeated exposures may lead to desensitization in adults, these lesions are more common in children. They begin as an erythematous wheal, lasting from 2 to 10 days, and may lead to temporary hyperpigmentation. Children who suffer this hypersensitivity

Chapter 42: Mosquitoes and Mosquito-Borne Diseases may develop a firm, light brown papule, whereas most adults have only a transient wheal without formation of a persistent papule. The dermatopathology of the epidermis in papular urticaria shows spongiosis with exocytosis and vesicle formation. The upper dermal layer reveals a localized perivascular infiltrate with lymphocytes, histiocytes, eosinophils, and mast cells, and a spattering of eosinophils and mast cells in the mid-dermis.77 The pathophysiology behind the phenomenon of itching is complex. There are abundant theories on the neurophysiologic basis of itch, and the most traditional is that local reaction induces the production of histamine, which stimulates C nerve fibers that travel to the brain and induce a sense of itching.90 Histamine, however, is only one of many pruritogenic substances that stimulate a subset of specialized skin C-fibers. Other mediators of itch include proteases, opioids, lipid peroxidation metabolites (such as leukotrienes and prostaglandins), neuropeptides (e.g., substance P), cytokines, and growth factors (e.g., nerve growth factor). Pruritus is now seen as an interdisciplinary issue that reaches into the fields of neurophysiology, neuroimmunology, neuropharmacology, protease research, internal medicine, and dermatology. In general, mosquitoes confer disease on humans by carrying and harboring viruses that have animal reservoirs. Different viruses have different transmission patterns, some with avian reservoirs and others with nonhuman primate reservoirs (and sometimes even humans). The geographic distribution of mosquitoes and changes in their habitats affect the distribution of disease as well. Although mosquitoes are often thought of as living only in temperate and tropical areas, their geographic distribution extends to climatic extremes and ranges north of the Arctic Circle, where they have adapted to conditions by spending their larval stage frozen in the ice. Disease patterns differ depending on the geographic distribution of the species. Malaria, for example, is mostly found in sub-Saharan Africa, India, Bangladesh, Southeast Asia, Central and South America, and some parts of the Middle East; dengue fever is in Southeast Asia, Central America, the Caribbean, the southwestern Pacific, and recently in the United States; Japanese encephalitis spans the bottom half of India in a northeastern direction up to Japan, covering eastern China and Southeast Asia. Geographic distributions and transmission patterns are discussed in the remainder of this chapter.


DISEASES The effects of mosquitoes on human life are far reaching. Every year, they are responsible for transmitting a wide spectrum of diseases, such as malaria, dengue fever, yellow fever, and encephalitis to millions of people. This chapter discusses the main diseases transmitted by mosquitoes, other than malaria (see Chapter 43). Table 42-1 summarizes the viruses and the clinical presentations of the severe forms of the diseases.

Dengue Dengue was first identified as being caused by a virus in the 1940s, although its existence was probably present much earlier, as reports of dengue fever epidemics were reported as early as 1779. Like West Nile virus, dengue viruses belong to the family Flaviviridae, genus Flavivirus, and have serotypes 1 through 4 (DEN-1, DEN-2, DEN-3, and DEN-4), all of which cause infec-

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tion. Currently, it is estimated that 50 to 100 million people in more than 100 countries are infected yearly with dengue viruses.42

Epidemiology and Transmission Aedes mosquitoes are responsible for transmission of dengue viruses via a human-mosquito-human cycle: having picked up the virus, the female mosquito carries it for the rest of her life and can transmit the disease to many susceptible individuals. These mosquitoes breed either inside or close to houses and often bite humans unnoticed. Because they feed many times in a breeding cycle, numerous people living in one household can be infected by the same mosquito. Several species of Aedes can transmit dengue, but the most important is Aedes aegypti, which is found in temperate zones from latitude 45° north to 35° south. Aedes albopictus, another species that can transmit the virus, has a larger geographic distribution than A. aegypti but is less often the culprit responsible for dengue transmission because these mosquitoes breed farther from households and bite humans less frequently.42 Dengue virus transmission is classified as epidemic dengue when a single virus strain is introduced into a region with a large number of hosts and mosquitoes, or as hyperendemic when there is uninterrupted circulation of numerous dengue serotypes in one area. Epidemic dengue is the usual transmission pattern for many smaller islands in South America, Africa, and Asia, where several years pass between epidemics and then the disease reemerges. For travelers, this means that the risk of acquiring the infection is high during epidemics, but it is very low between those periods. Generally, the frequency of dengue hemorrhagic fever (DHF) during epidemics seems to be lower than in areas where the transmission pattern is hyperendemic. In hyperendemic areas, competent mosquito vectors are present throughout the year and the population of uninfected individuals is sufficiently large to sustain the disease. This latter pattern of transmission accounts for the preponderance of global dengue virus infections.40 As shown in Figure 42-9, dengue virus has been found in Southeast Asia and the western Pacific islands (with hyperendemic transmission of all four serotypes present in Thailand, Vietnam, Indonesia, Malaysia, and the Philippines). Hyperendemic dengue fever (DF) is also found in India, Pakistan, and Sri Lanka. The A. aegypti mosquitoes are also distributed across much of sub-Saharan Africa and the Middle East. In the Americas, A. aegypti exists in the southeastern United States, Mexico, Central America, South America, and the Caribbean.42 Reports of DF and DHF are increasing, and the most recent global epidemic was in 1998. In the past, DF was considered a relatively benign and nonfatal disease, but since World War II there has been expansion of the disease not only in frequency and geographic distribution but also in morbidity and mortality. The 1980s and 1990s saw a rise in DHF (specifically, serotype DEN-3) in southern Asia, and in the 1980s, there was a rise in epidemic DF/DHF (specifically serotype DEN-2) in Taiwan and the People’s Republic of China. Africa has seen large increases in DF incidence since 1980.38 Dengue has also been emerging much more rapidly in the Americas, with the first major outbreak in Cuba in 1981 and continuing outbreaks in other Central and South American countries since then.64,68 Demographic changes, such as population growth and increased human density, contribute to transmission and also to emergence of DHF, and unplanned urbanization that results in

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TABLE 42-1. Characteristics of Mosquito-Borne Viral Diseases

VIRUS

FAMILY

West Nile virus

Flavivirus

St. Louis encephalitis virus Japanese encephalitis virus Murray Valley encephalitis virus Eastern equine encephalitis virus

Flavivirus Flavivirus Flavivirus

Togavirus

Canyon virus

Bunyaviridae

La Crosse virus

Bunyaviridae

Dengue fever virus

Flavivirus

Yellow fever virus Ross River virus

Flavivirus Togavirus

MAIN AGE GROUP AFFECTED

GEOGRAPHIC DISTRIBUTION Africa, West Asia, Middle East, Europe, United States Central, west, southern United States Japan, China, Southeast Asia, India Australia, Papua New Guinea Eastern and Gulf coasts of United States, southern USA, South America United States (including Alaska) Central and eastern United States Central and South America, Africa, Asia, southeastern United States Africa and South America Australia, Papua New Guinea, South Pacific

MORTALITY (%)

SPECIFIC TREATMENT?

HUMAN VACCINE AVAILABLE?

ADDITIONAL NOTES —

Adults

3–15

No

No

Adults

3–30

No

No

38° C [100.4° F]) or hypothermia (10,000/mm3 Neuroimaging findings consistent with acute inflammation (with or without involvement of the meninges) or acute demyelination Presence of focal neurologic deficit Meningismus EEG findings consistent with encephalitis Seizures, either new onset or exacerbation of previously controlled At least 2 of the following: Asymmetry to weakness Areflexia/hyporeflexia of affected limb(s) Absence of pain, paresthesia, or numbness in affected limb(s) CSF pleocytosis (5 leukocytes/mm3) and elevated protein levels (45 mg/dL) Electrodiagnostic studies consistent with an anterior horn cell process Spinal cord MRI documenting abnormal increased signal in the anterior gray matter

CSF, cerebrospinal fluid; EEG, electroencephalography; MRI, magnetic resonance image. From Sejvar JJ, Haddad MB, Tierney GL, et al: Neurologic manifestations and outcome of West Nile virus infection. JAMA 290:511–515, 2003.

Box 42-1. 2004 CDC Case Definition for Neuroinvasive and Non-neuroinvasive Domestic Arboviral Diseases CLINICAL CRITERIA FOR DIAGNOSIS

Confirmed Case

Neuroinvasive disease requires the presence of fever and at least one of the following, as documented by a physician and in the absence of a more likely clinical explanation: • Acutely altered mental status (e.g., disorientation, obtundation, stupor, or coma), or • Other acute signs of central or peripheral neurologic dysfunction (e.g., paresis or paralysis, nerve palsies, sensory deficits, abnormal reflexes, generalized convulsions, or abnormal movements), or • Pleocytosis (increased white blood cell concentration in cerebrospinal fluid [CSF]) associated with illness clinically compatible with meningitis (e.g., headache or stiff neck). Non-neuroinvasive disease requires, at minimum, the presence of documented fever, as measured by the patient or clinician, the absence of neuroinvasive disease (above), and the absence of a more likely clinical explanation for the illness. Involvement of non-neurological organs (e.g., heart, pancreas, liver) should be documented using standard clinical and laboratory criteria.

• Fourfold or greater change in virus-specific serum antibody titer, or • Isolation of virus from or demonstration of specific viral antigen or genomic sequences in tissue, blood, CSF, or other body fluid, or • Virus-specific immunoglobulin M (IgM) antibodies demonstrated in CSF by antibody-capture enzyme immunoassay (EIA), or • Virus-specific IgM antibodies demonstrated in serum by antibody-capture EIA and confirmed by demonstration of virus-specific serum immunoglobulin G (IgG) antibodies in the same or a later specimen by another serologic assay (e.g., neutralization or hemagglutination inhibition).

LABORATORY CRITERIA FOR DIAGNOSIS

Cases of arboviral disease are also classified as either confirmed or probable, according to the following laboratory criteria:

Probable Case

• Stable (less than or equal to a twofold change) but elevated titer of virus-specific serum antibodies, or • Virus-specific serum IgM antibodies detected by antibodycapture EIA but with no available results of a confirmatory test for virus-specific serum IgG antibodies in the same or a later specimen. Case Definition

• A case must meet one or more of the above clinical criteria and one or more of the above laboratory criteria.

From Centers for Disease Control and Prevention, and available at www.cdc.gov/epo/dphsi/casedef/arboviral_current.htm.

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capture ELISA (MAC-ELISA, available in the United States from Focus Technologies and PanBio, Inc.). There is, however, a chance that persistent IgM antibodies can be found in people years after living in places where WNV is epidemic. The diagnosis can be further confounded by the fact that these IgM ELISA tests have a cross-reactivity of up to 44% with other flaviviruses during acute infection.36 The most specific test for arthropod-borne flaviviruses is the plaque-reduction neutralization test (PRNT). It can be used both to negate the false-positive results sometimes seen in MACELISA or other assays, and to facilitate discrimination among the flaviviruses.22 Efforts have been made to develop more specific and rapid serologic assays. Promising candidates include a microsphere immunoassay that discriminates among different flavivirus infections, as well as an immunofluorescence assay that has less cross-reactivity among WNV IgM antibodies and closely related flaviviruses. PCR (used for screening blood products in the United States) or viral culture can also isolate the virus, but sensitivity is not high because of the transient and low levels of viremia, as the virus quickly disappears from the periphery into the CNS in severe disease.67

Treatment and Prevention Currently, there is no specific treatment for WNV, although certain antivirals, antibodies, and drugs altering the inflammation process (e.g., interferon) are being tested. Nucleoside analogs have been studied in vitro, and the most advanced testing in vivo has been with ribavirin, with no reduction in disease48 or viremia58 shown. For prevention of disease, general control measures against mosquitoes can be taken, but so far there is no specific way to prevent WNV. A vaccine exists for horses, but it has not yet been studied in humans. Theoretically, there is a potential for an inactivated virus to induce long-term immunity, because such a vaccine exists for JE and other flavivirus diseases. Candidate vaccines against WNV include a chimeric virus based on the live, attenuated yellow fever 17D vaccine virus containing the pre-membrane and envelope proteins of WNV,32 a DNA vaccine virus based on a low-virulence form of WNV found in Australia (the Kunjin virus),53 and a recombinant envelope-based protein vaccine.

Surveillance and Reporting Reporting requirements for suspected WNV infections vary across local and state health departments, but WNV encephalitis is now on the list of designated nationally notifiable conditions. The CDC may use results from commercial laboratories but may also request samples for diagnosis in its own laboratory. Information on how to send specimens can be found at www.cdc.gov/./ncidod/dvbid/misc/arboviral_shipping.htm. For ecologic surveillance, the CDC and other federal agencies have established specific guidelines and protocols to track avian, equine, and mosquito epizootics.

Epidemiology and Transmission The Culex mosquito is the main species that transmits StLE virus, with birds as a reservoir and humans as another host. The viremia, however, does not cause illness in either birds or mosquitoes. Around the Gulf Coast, Ohio, and Mississippi Valley, the culprit mosquitoes are Culex pipiens and Culex quinquefasciatus; in Florida, Culex nigripalpus; and in the western states, Culex tarsalis.21 In temperate parts of the United States, disease usually occurs in late summer or early fall, but it can occur year-round in the southern United States. Outbreaks can occur almost anywhere in the United States; the most recent epidemic was in the mid1970s in the Midwest. Recent outbreaks of StLE have been less than 30 cases each time. The most recent outbreak in Louisiana was 20 reported cases.18

Clinical Presentation Risk factors are low socioeconomic status, outdoor occupations, and older age. StLE has an incubation period of approximately 5 to 15 days, with a 300 : 1 ratio of asymptomatic to symptomatic cases. Patients with symptomatic StLE present with high fever and headache (55%), aseptic meningitis (40%), and encephalitis (5%).71 Infants, in particular, may have occasional convulsions and spastic paralysis. Of recognized cases, 95% are hospitalized for CNS involvement. The case fatality rate is 3% overall and up to 30% in older adults.18

Treatment and Prevention As is the case for many viral illnesses, there are neither specific therapies nor vaccines.

Eastern Equine Encephalitis First discovered in the brain of a horse with encephalitis in 1933 in New Jersey, eastern equine encephalitis (EEE) is a serious mosquito-borne disease with a high case fatality rate that appears in the eastern half of the United States. The virus is a member of the family Togaviridae, genus Alphavirus, and it is related to western and Venezuelan equine encephalitis viruses.60

Epidemiology and Transmission The transmission cycle involves birds and several species of mosquitoes, predominantly Culiseta melanura (Fig. 42-16). Other possible mosquito vectors include species in the genera Aedes and Coquillettidia.60 Humans and horses are considered hosts with incidental infections that can progress to severe disease. EEE occurs mainly along the eastern and Gulf coasts of the United States, but cases have been documented as far north as southern Canada and as far south as northern parts of South America. It occurs mainly in the summertime. From 1964 to the present, there have been 200 confirmed cases in the United States, with an average of four cases per year. The real incidence is probably higher because of underreporting and underrecognition. Most of the cases have been in Florida, Georgia, Massachusetts, and New Jersey, near coastal areas and freshwater swamps.20

St. Louis Encephalitis

Clinical Presentation

The St. Louis encephalitis (StLE) virus is a flavivirus related to Japanese encephalitis and West Nile virus, and it is also transmitted by mosquitoes. Since 1964, less than 5000 human cases of StLE have been reported in the United States.21

At risk for developing EEE are persons who live (or visit) endemic areas and those who spend significant time outdoors. Individuals older than 50 years and younger than 15 years have a greater chance of developing severe disease.

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Surveillance and Reporting EEE is a nationally notifiable disease.

Australian Encephalitis (Murray Valley Encephalitis) Epidemiology and Transmission Occurring mainly in Australia and New Guinea, Murray Valley encephalitis (MVE) virus is from the family Flaviviridae, genus Flavivirus, and is transmitted via a bird-mosquito-bird cycle with Culex annulirostris. Because humans do not have high levels of viremia, they are seen as dead-end hosts.

Clinical Presentation Most infections are asymptomatic, and only one in 1000 to 2000 infections actually develops into clinical illness.57 The clinical course is similar to that of JE, with headache, fever, myalgias, nausea and vomiting, and anorexia. The neurologic involvement can involve lethargy, irritability, confusion, or meningismus, as well as seizures, spastic paresis, and coma. Persons who succumb to progressive MVE infection have a poor prognosis; more than 30% die and 50% suffer neurologic sequelae, with a bimodal risk for children and older adults.

Diagnosis Figure 42-16. Micrograph of eastern equine encephalitis virus.

Clinical presentation can be within the spectrum from mild influenza-like illness to encephalitis, coma, and death. One study collecting the 36 cases from 1988 to 1994 in the United States showed that clinical signs included fever (83%), headache (75%), nausea and vomiting (61%), confusion (4%), myalgias and arthralgias (36%), chills (25%), seizures (25%), focal weakness (23%), abdominal pain (22%), respiratory symptoms (11%), and cranial nerve palsies (8%).26 The case fatality rate for EEE is 35%, and 35% of persons who survive are left with mild to severe neurologic deficits.20

Diagnosis Peripheral blood may show leukocytosis, and analysis of CSF may reveal elevated protein with red and white cells in the range of 600 to 2000/mm3 (white cells being predominantly lymphocytes). Definitive diagnosis lies in serologic evidence based on paired sera (acute and convalescent samples) in hemagglutinininhibition assays or in neutralization assays. Acute samples should be obtained within 10 days of symptom onset, and convalescent samples about 2 or 3 weeks after the symptom onset. IgM antibodies may also be captured by ELISA. It is possible to isolate the virus directly from the serum in acute infection, but this method is less common.60 Other helpful diagnostic modalities include MRI, which may show focal changes, particularly in the basal ganglia and thalamus.26,34

Treatment and Prevention No specific treatment is available. There has been one case report of a child being treated with intravenous immunoglobulin (IVIg),30 but this has not been further studied. No human vaccine is available, but there are equine vaccines that should be employed in endemic areas.

As is true for many other viral illnesses, definitive diagnosis of MVE is by identifying IgM antibody via immunoassay of the CSF. Direct viral isolation or PCR can also prove the infection in tissue, blood, or CSF. However, these tests can be obscured by cross-reactive antibodies to Kunjin, JE, Edge Hill, Alfuy, Sepik, dengue, and other flaviviruses.79 Two-thirds of patients have normal CT scans. If the scans are abnormal, they may show nonspecific signs of encephalitis, including mild hydrocephalus and cerebral edema.49

Treatment and Prevention There is no specific treatment or vaccine for MVE.

California (La Crosse) Encephalitis La Crosse (LAC) virus is a California serogroup bunyavirus that can cause encephalitis (usually in children) in the central and eastern United States. La Crosse encephalitis comprises 8% to 30% of all cases of encephalitis in the United States, and it is one of the major causes of arboviral illness.70 In fact, its incidence in endemic areas (20 to 30 cases per 100,000 population per year) exceeds that of bacterial meningitis.63

Epidemiology and Transmission Aedes triseriatus is the main vector (although A. albopictus, or Asian tiger mosquito, may be emerging as another significant species), with vertebrate hosts such as chipmunks, tree squirrels, and foxes. The annual incidence is about 60 to 130 cases.66 Most infections are asymptomatic and occur from late summer to early fall in the northern United States.28

Clinical Presentation For 80% to 90% of infected persons, the clinical course is mild, with only headache, fever, and vomiting after an incubation period of 3 to 7 days. Approximately 10% to 20% of infected individuals develop a severe form of the disease within the first 8 to 24 hours of symptom onset.62 In one pediatric study of 127 hospitalized children, it was noted that 70% of patients presented with headache, fever, and vomiting. Of children, 46%

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had seizures (generally focal seizures, with some progression to status epilepticus), and 20% had focal neurologic findings. Encephalitis does not always occur, as aseptic meningitis was also found. Although all patients survived, over 10% were left with neurologic deficits.61 Only one case report has mentioned California encephalitis causing infarction of the basal ganglia, leaving a child with acute hemiparesis.54 The case fatality rate is less than 1%.

Diagnosis Laboratory findings may reveal leukocytosis with polymorphonuclear leukocyte predominance and pleocytosis in the CSF (either neutrophilic or lymphocytic predominance), although studies of laboratory values for LAC and non-LAC cases show no statistically significant differences.45 More than half of patients have abnormal electroencephalography. A CT scan may show nonspecific cerebral edema, if there are any findings at all, and MRI may reveal gadolinium enhancement in cortical areas.61 Definitive diagnosis is made with IgM antibody by capture immunoassay of CSF, a fourfold rise in serum antibody titers against LAC virus, or isolation of virus from or demonstration of viral antigen or genomic sequences in tissue, blood, or CSF.7 As in almost all other viral infections discussed in this chapter, IgM antibody capture with ELISA is the most common method, with the recommendation to confirm IgG antibody with another serologic assay such as neutralization.

Treatment and Prevention No specific treatment is available besides general measures to control cerebral edema and seizures. Certain studies have looked at ribavirin,62 but there is no strong evidence to recommend its use. No vaccine is available against this virus.

Epidemic Polyarthritis (Ross River Virus) A mosquito-borne alphavirus in the family Togaviridae, Ross River virus (RRV) is a single-stranded, enveloped RNA virus in the same family as Chikungunya, Sindbis, and eastern and western equine encephalitis. The virus is endemic and enzootic in Australia (where approximately 5000 cases are reported annually) and Papua New Guinea and causes epidemic polyarthritis.46 In the late 1970s, RRV spread to the South Pacific islands, but it disappeared after the end of an epidemic in which 500,000 people were infected; recent reports, however, show that there are new cases reappearing in Fiji.50

Epidemiology and Transmission The main vectors are Culex and Aedes (particularly Aedes vigilax) mosquitoes, and marsupials such as kangaroos and wallabies are important as vertebrate-amplifying hosts.69 Vertical transmission is possible from mosquito to offspring, and human-mosquito-human transmission is also thought to occur. Tropical coastal regions with salt marsh habitats are the habitat for the mosquito vector species, and infections are most common in the spring, after summer rains, or after inundation of salt marshes by rain or tides.50

Clinical Presentation After inoculation, the virus is thought to replicate within macrophages. It causes local cell-mediated immune responses that appear to be the cause of arthritis. After an incubation of 3 to 9 days (or as long as 21 days), patients can present either with acute febrile illness with arthritis and rash; with acute

fever, rash, and arthritis alone; with polyarthralgia; or with arthritis.32 The joints involved are usually symmetric and include the wrists, knees, ankles, and metacarpophalangeal and interphalangeal joints of the hands, with true arthritis present in 40% of infected individuals. About 50% have fever and a sparse maculopapular rash on the limbs and trunk that may occur before or after the arthritis. Whereas fever may resolve within several days, rash may persist for several months. Joint symptoms, on the other hand, have been reported to last up to 3 years, even after fever and rash have subsided.60

Diagnosis There are no specific laboratory findings for RRV infection, with normal leukocyte counts (although mild neutrophilia or atypical lymphocytes can be found) and possibly elevation in the nonspecific erythrocyte sedimentation rate. Joint aspiration may reveal viscous fluid with predominantly mononuclear cells, and points to viral arthritis.32 Serum can be screened for IgM antibody against Ross River virus IgM, which can then be confirmed by PRNT. These tests are available at only a few reference laboratories, including the CDC.50 Viral culture and PCR are not commonly used for diagnosis of RRV infection.

Treatment and Prevention There is no specific treatment. Management of arthralgias and myalgias is with standard analgesic and nonsteroidal antiinflammatory drugs. There does not seem to be any direct association of mortality with RRV.

Jamestown Canyon Virus Jamestown Canyon virus is a widely distributed California serogroup bunyavirus that appears to be responsible for several cases of encephalitis in the United States. It is transmitted by Culiseta inornata as well as several species of Aedes mosquitoes; the vertebrate reservoir has been identified as the whitetailed deer.33 These infections are rare. There is a case report of Jamestown canyon virus–induced encephalitis in an 8-year-old girl in rural southwestern Michigan, who presented with symptoms of headache and fever that quickly progressed to seizures and coma.37 The infection is difficult to distinguish from other California serogroup bunyaviruses such as California encephalitis, snowshoe hare, Keystone, and trivittatus viruses, because of cross-reactivity in the more common serologic tests and difficulty in isolating the actual virus.80 The virus has been posited as a possible emerging infectious disease,37 but there have been few identified cases and the literature on this subject is scant.


MOSQUITO CONTROL General Guidelines for Individual Protection For personal protection and prevention, individuals can take precautions such as avoiding mosquitoes at their most active time (from dusk to dawn) and wearing loose-fitting cotton clothing covering their arms and legs (see Chapter 41). Individuals may also apply repellents to exposed areas of skin. The most effective preparations contain N,N-diethyl-3-methylbenzamide (DEET), and generally concentrations need not exceed 20% to 35%.31 DEET is safe in children and pregnant women,23 but it has rare side effects of neurologic toxicity and should be used sparingly to avoid systemic absorption, and it should be kept away from mucous membranes. Studies have shown that

Chapter 42: Mosquitoes and Mosquito-Borne Diseases a single application of a product containing 24% DEET confers an average of 5 hours (and up to 12) of protection against A. aegypti mosquitoes. Compared with DEET, newer formulations containing the compound IR3535 fared poorly.31 Permethrincontaining compounds and other residual insecticides that kill rather than simply repel mosquitoes may be applied to clothing and netting. Other strategies include using mosquito coils and sprays containing pyrethroids in sleeping areas. Citronella has been also shown to be mildly effective in reducing the number of bites, but it requires frequent applications if used topically (as opposed to the candle form).30 Current research in insect repellents involves a sophisticated appreciation of the olfactory senses of mosquitoes, and creating proteins to inactivate human-specific odorants.71

Global Programs In general, global eradication programs5 for all infectious diseases, including mosquito vector surveillance and control, have declined dramatically in the past few decades. Because of the success of control programs in the 1970s and the resultant decreased public health threat, less attention has been paid and fewer resources have been allocated to maintaining good control. One result is fewer trained personnel, because training programs are less well funded. The effect has been detrimental, with a reversal of previous gains. In Central and South America, for example, dengue fever was largely eliminated with eradication in the 1950s and 1960s of the A. aegypti mosquito, the main vector for the disease. However, because these programs were largely dismantled in the 1970s, the mosquito species has re-infested most of these tropical regions.39 Vector control has three arms: environmental management, biologic control, and chemical control. Environmental management consists of monitoring and intervening to reduce the vector population, as well as transmission factors that sustain the human-vector-pathogen contact. For example, simply removing old tires, covering water storage containers with tight lids, keeping floor drains cleaned and covered, and chlorinating ornamental pools and fountains (or populating them with larvivorous fish) can help prevent breeding of mosquitoes. Biologic control includes using organisms that naturally prey on the vector. For example, larvivorous fish and Bacillus thuringiensis H-14 (BTI) are commonly used against larvae. Biologic control, however, requires expense and time to raise these organisms, and the organisms may have limited success when the environment in which they are placed does not sustain their existence. Furthermore, even if they are effective in reducing the number of larvae, there is not conclusive evidence to show that this decreases transmission of disease, because a lower density of larvae in a certain area may mean healthier and stronger adult mosquitoes if food is limited. Chemical control is the most well known vector control. It consists of using products such as pyrethrins (e.g., deltamethrin, resmethrin, permethrin) or organophosphate insecticides (e.g., fenthion, malathion, fenitrothion, temephos). These can be applied in several forms: larvicidal application, perifocal treatment, or space spraying. Larvicidal application is focal treatment to domestic water supplies that cannot be eliminated (e.g., for A. aegypti, either 1% temephos or methoprene to regulate larvicidal growth, or BTI can be used to safely treat drinking water). Insecticides such as fenthion, malathion, and fenitrothion can be used as perifocal treatment for nonpotable sources of water to eliminate larvae and adult mosquitoes. Finally, space

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TABLE 42-3. Insecticides for Cold-Spray Control of Aedes aegypti INSECTICIDE Malathion Fenitrothion Naled Pirimiphos-methyl Deltamethrin Resmethrin Bioresmethrin Permethrin Cypermethrin Lambda-cyhalothrin

DOSAGE (grams of active ingredient per hectare) 112–693 250–300 56–280 230–330 0.5–1 2–4 5 5 1–3 1

From World Health Organization: Dengue Haemorrhagic Fever: Diagnosis, Treatment, Prevention and Control, ed 2. Geneva, World Health Organization, 1997.

spraying can be used against adult mosquitoes, often in emergency situations. The chemicals mentioned here can be used as aerosols or mists applied by portable machines, vehiclemounted generators, or aircraft. Parameters for use (e.g., grams of active ingredient per hectare, wind conditions that may limit effectiveness) depend on the type of chemical, the equipment, and the target vector. Table 42-3 shows selected insecticides and dosages for cold-spray control of A. aegypti. Precautions must be taken seriously when using these products, such as following instructions on labels, using physical protection such as gloves and masks, and correctly disposing of chemicals.87 Integrated control programs that incorporate all three methods, along with public education and campaigns, are the most effective way to control disease. This includes initiatives such as encouraging vaccination—not only of humans, but of the animal reservoirs for which vaccines are available. This includes, for example, equine vaccinations against West Nile virus. Recently, leading health organizations have been trying to reinstate vector and disease control, as can be seen by a short history of their efforts. In the 1950s, the WHO embarked on a mission to eradicate malaria. Despite some early success, by the mid-1970s, it was increasingly difficult to achieve the eradication goal for a number of reasons, including resistance to DDT and other insecticides. However, in 1998, the WHO, the United Nations Development Programme (UNDP), the World Bank, and UNICEF established the “Roll Back Malaria” initiative with a special focus on Africa. One arm of the campaign is to encourage widespread use of antimalarial drugs in clinics and health centers with a simple diagnosis. The other objectives are to plan and implement sustainable vector control. Experience has shown that pyrethroid-impregnated bed nets may be a better global strategy for eradicating disease, as this approach is less expensive than repeated spraying of household walls, it reduces infections (and thus the human reservoir for infection in malaria), and it is more effective in terms of horizontal implementation than top-down, or vertical, programming.2 Although source reduction through environmental management has been shown to be effective in some places,82 it is generally very difficult and may not be feasible everywhere.72 Resistance to insecticides is a very real problem. However, it is often a local phenomenon, so certain chemicals and insecticides should not be completely abandoned once reports of

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resistance are raised. For example, sampling sites only a few kilometers apart in Guatemala showed a large difference in resistance for Anopheles albimanus mosquitoes. Similarly, in the United States, resistance of Culex species to organophosphates is high in areas where vector control is well implemented, but it is lower in rural areas.39 The WHO has developed bioassays to determine resistance and keeps a database of resistance. This database, however, can be misleading because it is based on a single dataset from a single point in time that may be several years, or even decades, old and no longer relevant.39 There are newer diagnostic methods to test resistance, including genetic linkage and physical maps, that may elucidate factors in vector competence.3 A further step is to detect and contain epidemics through epidemiologic surveillance, and then to train personnel and build local capacity to sustain these efforts. Vector surveillance is of primary importance, not only to learn the geographic distribution and density of mosquito vectors and to evaluate control programs but also to predict and intervene to stop the advance of preventable diseases. For mosquitoes, indices have been created to study immature and adult populations (e.g., the

43

“house index” (the percentage of houses infected with larvae or pupae), and an index of adult mosquitoes’ landing or biting rates per person-hour). Surveillance also includes verification of control measures, which includes periodically testing the vector’s susceptibility to certain insecticides. Ongoing inspection of areas free of disease and taking measures to prevent reinfestation by vectors (e.g., removing standing water sources and environmental habitats, such as tires and cemetery vases) should be instituted.87 Many countries are committed to the idea of vector and disease surveillance (particularly aided by the work of bodies such as the Pan American Health Organization, the CDC, and the WHO), but hundreds still fall short of pursuing these initiatives and are thus ill-prepared to effectively control disease. Concerted international efforts to collect accurate information and relay it in a timely fashion is the next herculean, but worthwhile, task.

The references for this chapter can be found on the accompanying DVD-ROM.

Malaria Sheral S. Patel and James W. Kazura

Malaria is a major international health problem. As global travel increases, malaria is found with increasing frequency in areas where malaria is not endemic. Human malaria is caused by four species of parasitic protozoa, Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae, which are transmitted by mosquitoes. Prevention of malaria infection through education, chemoprophylaxis, and personal protective measures can significantly reduce the risk of malaria morbidity in travelers. Because malaria infection can be life threatening, awareness of rapid diagnosis and management of this disease by health care providers is essential.


EPIDEMIOLOGY Malaria is endemic throughout tropical areas of the world and is usually transmitted to humans through the bite of a female Anopheles mosquito (Fig. 43-1A and B). Forty-eight percent of the world’s population live in malaria-endemic areas.14 Malaria infects at least 300 to 500 million people annually, resulting in 1 to 2 million deaths.13,43 Most malaria-related deaths occur in infants and young children, particularly in sub-Saharan Africa.

P. falciparum and P. malariae are found throughout malariaendemic areas of the world, including Latin America, subSaharan Africa, Asia, and the South Pacific. P. vivax is endemic in Latin America, Asia, and the South Pacific but uncommon in areas of sub-Saharan Africa. Both P. falciparum and P. vivax were historically endemic in temperate areas such as North America and Europe, and transmission still occurs rarely in these areas.14 Low frequencies of P. ovale infection are prevalent in most malaria-endemic areas, especially in West Africa. The risk of acquiring malaria is highest for travelers to subSaharan Africa and Oceania (Papua New Guinea, Vanuatu, and the Solomon Islands), intermediate in the Indian subcontinent and Haiti, and lowest (but still significant) in Southeast Asia and the Americas (Table 43-1).8 There can be variability in transmission within endemic areas based on season, altitude, and type of travel. For example, the risk of acquiring malaria is lower for a business traveler to a Southeast Asian city staying in an air-conditioned hotel than for a backpacker hiking and sleeping in tents in East Africa. Rates of malaria in U.S. civilians have been rising as travel to malaria-endemic areas increases.29 In 2002, there were 1337 cases of malaria in the

Chapter 43: Malaria

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United States

Mexico Cuba

Dominican Republic

Belize Haiti Honduras Guyana Guatemala Panama El Salvador Venezuela Nicaragua Costa Rica Colombia

Suriname French Guiana

Ecuador

Peru Brazil Bolivia Paraguay

Chile Uruguay

Argentina

Malaria-Endemic Countries

Falkland Islands

Chloroquine-Resistant Chloroquine-Sensitive None

A Figure 43-1. A, Distribution of chloroquine-resistant and chloroquine-sensitive malaria-endemic areas in the Americas, 2002.

United States reported to the Centers for Disease Control and Prevention.29 The majority were imported from malariaendemic areas of Africa (68%) and Asia (13%) and caused by P. falciparum (52%).29 In addition, two cases of malaria were acquired in the United States, indicating that transmission is possible in temperate areas where Anopheles mosquitoes are present. Parasite resistance to antimalarials has been increasing (Table 43-2).41 Most parts of the world have chloroquine-resistant P. falciparum (see Figure 43-1A and B).8 In addition, P. falciparum is becoming resistant to other antimalarials such as mefloquine,

pyrimethamine-sulfadoxine, and halofantrine (Fig. 43-2).8,27 In Southeast Asia, partial resistance of P. falciparum to quinine or quinidine has been reported. Areas with reports of chloroquineresistant P. vivax include Southeast Asia, India, the South Pacific, Somalia, and South and Central America. Many genetic changes in human red blood cells occur in areas where malaria is or was historically endemic, which suggests that these polymorphisms have arisen to protect individuals from malaria. Sickle cell disease, thalassemia, glucose-6phosphate dehydrogenase (G6PD) deficiency, and Southeast Asian ovalocytosis (including Gerbich negativity) have all been

Estonia Latvia Russia

South Africa

Austria

Chloroquine-Resistant Chloroquine-Sensitive None

Swaziland Lesotho

Malaria-Endemic Countries

France

Singapore

Macau

New Zealand

New Caledonia

Vanuatu

Fiji

Solomon Islands

Papua New Guinea

Japan

Figure 43-1, cont’d. B, Distribution of chloroquine-resistant and chloroquine-sensitive malaria-endemic areas in Africa, the Middle East, Asia, and the South Pacific, 2002. (A and B from Centers for Disease Control and Prevention (CDC): Malaria. In Health Information for International Travel, 2005–2006. Atlanta, U.S. Department of Health and Human Services, 2005. [A from Map 4-6, available at http://www2.ncid.cdc.gov/travel/yb/utils/ybGet.asp?section=dis&obj=index.htm#map4-6; B from Map 4-7, available at http://www2.ncid.cdc.gov/travel/yb/utils/ybGet.asp?section=dis&obj=index.htm#map4-7])

B

UK

Lithuania

Sweden

Finland

Belarus Germany Poland Ukraine

Denmark

Norway

Azerbaijan Kazakhstan Georgia Mongolia Romania Uzbekistan Italy BulgariaArmenia Kyrgyzstan Spain Portugal North Korea Turkey Turkmenistan Malta Tajikistan China Greece South Syria Cyprus Tunisia Afghanistan Lebanon Korea Nepal Iraq Iran Israel Morocco Bhutan Jordan Kuwait Pakistan Myanmar Algeria Western Libya Egypt (Burma) Qatar Sahara UAE Taiwan India Senegal Saudi Arabia Laos Mauritania Mali Macau The Oman Niger Philippines Eritrea Yemen Thailand Gambia Chad Bangladesh Burkina Sudan Vietnam Djibouti GuineaFaso Brunei Nigeria Bissau Cambodia Ethiopia CAR Guinea Cameroon Sri Lanka Malaysia Somalia Sierra Leone DROC Uganda Benin Kenya Ghana Rwanda Liberia Togo Burundi Indonesia Tanzania Malawi Côte d'Ivoire (Ivory Coast) Singapore Equatorial Guinea Mozambique Angola Gabon Zambia Congo Australia Zimbabwe Madagascar Namibia Botswana

Ireland

Iceland

Chapter 43: Malaria

TABLE 43-1. Risk of Malaria by Region RISK High Intermediate Low (but significant)

REGION Sub-Saharan Africa, Papua New Guinea, the Solomon Islands, Vanuatu Indian subcontinent, Haiti Southeast Asia, Central and South America

From American Academy of Pediatrics: Malaria. In Pickering LK, et al (eds): Red Book: 2006 Report of the Committee on Infectious Diseases, 27th ed. Elk Grove Village, IL, APP, 2006, pp 435–441.

TABLE 43-2. Antimalarial Drug Resistance in Malarial Parasites PLASMODIUM SPECIES P. falciparum

P. vivax P. ovale P. malariae

DRUGS FOR WHICH RESISTANCE IS ESTABLISHED Chloroquine, mefloquine, pyrimethaminesulfadoxine, halofantrine; partial resistance to quinine and quinidine; resistance to multiple drugs Chloroquine, pyrimethamine-sulfadoxine, primaquine None established None established

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stream to the liver, where they mature and produce 10,000 to 30,000 merozoites per sporozoite. The merozoites are released into the bloodstream 8 to 25 days later to invade circulating erythrocytes (see Figure 43-5).12 A subset of P. vivax and P. ovale parasites may remain dormant as hypnozoites in the liver and emerge as merozoites months to years after the initial inoculation to establish blood-stage infection. Merozoites enter red blood cells rapidly through specific erythrocyte receptors, many of which are yet undefined. P. falciparum has several invasion pathways, including glycophorin A and C, whereas P. vivax depends solely on the Duffy antigen for erythrocyte invasion.44 In the red blood cell, the asexual parasites consume hemoglobin and enlarge from the ring forms to become trophozoites and then schizonts. As the schizonts mature through multiple nuclear divisions, the red blood cell bursts, releasing 6 to 24 merozoites to invade additional circulating erythrocytes.3 The blood-stage cycle takes place over 48 to 72 hours. Some parasites develop into gametocytes (the sexual stage), which can infect mosquitoes when taken up during a feeding. After being ingested by an Anopheles mosquito, diploid zygotes are formed. Zygotes mature into ookinetes in the mosquito midgut.31 The resulting oocyst expands through meiotic reduction division within 7 to 10 days, releasing sporozoites that localize through the hemolymph to the salivary gland of the mosquito.4 The sporozoites are subsequently transmitted to another human host at the next blood meal.

Recurrent and Persistent Infections suggested to confer protection from falciparum malaria mortality.26a,39 In sub-Saharan Africa, nearly 100% of the population is negative for the Duffy blood group and has absolute protection against P. vivax, which depends on the Duffy antigen as a receptor for invasion.23


MALARIA PARASITE Mosquito Vector The female Anopheline mosquito is the arthropod vector for the malaria parasite (Fig. 43-3). Of almost 430 Anopheles species, only 30 to 40 transmit malaria (Fig. 43-4). These include Anopheles gambiae, Anopheles funestus, and Anopheles arabiensis in Africa; the Anopheles punctulatus group in Papua New Guinea; Anopheles culicifacies in India; Anopheles darlingi in South America; and Anopheles quadrimaculatus in North America.17 The female mosquito’s proboscis pierces the skin of a person to obtain the blood meal necessary to produce eggs. Distinguishing features of Anopheles mosquitoes include sensory palps that are as long as the proboscis, and discrete blocks of black and white scales on the wings.25 Both male and female Anopheles mosquitoes rest with their abdomens sticking up in the air, as opposed to parallel to the surface on which they are resting.25

Life Cycle The life cycle of the malaria parasite involves both vertebrate and arthropod hosts (Fig. 43-5). The asexual haploid form of the malaria parasite in the mosquito is the sporozoite. Transmission of 8 to 12 sporozoites usually occurs through the bite of a nocturnal-feeding female Anopheles mosquito (see Figure 43-3). Sporozoites then rapidly migrate through the blood-

Recurrent malaria infection can occur in several ways. First, relapses from P. vivax or P. ovale can occur when dormant hypnozoites mature and release merozoites, thus producing bloodstage infections. Second, incomplete treatment or a partially effective host immune response may lead to recrudescence of blood-stage infections. Relapse and recrudescence are caused by the same parasite clone that was responsible for the initial infection. Although recrudescence can occur with any malarial species, it is most common with P. falciparum because of antimalarial resistance. Finally, in areas of intense transmission, simultaneous infection or re-infection with multiple parasite species or strains can occur. P. malariae is frequently associated with persistent infections that can remain in the bloodstream at undetectable levels for up to 20 to 30 years.

Transmission Natural transmission of malaria occurs through the bite of a female Anopheles mosquito. Blood-stage infection can also be established by transfusions of blood or blood products, by organ transplantation, or by sharing of contaminated needles or syringes.35 Occasionally, congenital malaria occurs when mothers of newborns are infected.29 It may be difficult to distinguish congenital malaria from natural mosquito-borne transmission when the diagnosis is made in neonates 2 to 3 weeks after birth.


CLINICAL MANIFESTATIONS AND PATHOGENESIS

Susceptible Populations Patients with malaria present with variable and nonspecific signs and symptoms ranging from asymptomatic parasitemia to severe disease and death. Individuals living in malaria-endemic

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PART SIX: ANIMALS, INSECTS, AND ZOONOSES

Bhutan

India Bangladesh China Myanmar (Burma)

Laos

Figure 43-2. Distribution of mefloquine-resistant malaria.(From Centers for Disease Control and Prevention: Malaria. In Health Information for International Travel 2005–2006. Atlanta, U.S. Department of Health and Human Services, 2005. Map 4-8, available at http://www2.ncid.cdc.gov/travel/yb/utils/ybGet.asp? section=dis&obj=index.htm#map4-8.)

Thailand

Cambodia Vietnam

Mefloquine-Resistant Malaria Mefloquine-Resistant

Malaysia Indonesia

areas develop partial immunity through repeated infections with malaria parasites and rarely experience serious complications after childhood. Nonimmune individuals, such as travelers and immigrants from nonendemic areas, children (6 months to 5 years) living in endemic areas, and pregnant women, are at risk for severe disease and complications, especially with P. falciparum infection.38

Major Clinical Findings Red blood cell lysis and the release of merozoites at the end of a period of intraerythrocytic asexual reproduction result in the classic presentation of a malarial paroxysm characterized by high fevers, chills, rigors, sweats, and headache (Table 43-3).

Without appropriate therapy, paroxysms can recur in a cyclic pattern; every 48 hours with P. vivax and P. ovale, and every 72 hours with P. malariae. Although P. falciparum has a 48hour asexual erythrocytic cycle, fever and chills typically occur without any periodicity because erythrocyte lysis is not synchronized. Patients with malaria infection may also present with generalized weakness, backache, myalgias, vomiting, diarrhea, and pallor. If an appropriate travel history is not obtained, malaria infection can be mistaken for a viral syndrome or acute gastroenteritis. In addition, severe malaria can mimic other diseases (e.g., meningitis, typhoid fever, dengue, hepatitis) that are common in malaria-endemic countries. Partially immune indi-

Chapter 43: Malaria

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Figure 43-3. Female Anopheles gambiae mosquito feeding. Distinguishing features include sensory palps that are as long as the proboscis, and discrete blocks of black and white scales on the wings. Both male and female Anopheles mosquitoes rest with their abdomens sticking up in the air. (From Centers for Disease Control and Prevention Public Health Image Library, http://phil.cdc.gov/phil/home.asp. Left, image ID#1665; right, image ID#1664. Courtesy Dr. Jim Gathany and the Centers for Disease Control and Prevention, Public Health Information Library.)

messeae atroparvus superpictus sinensis pulcherrimus sacharovi fluviatilis anthropophagus sergentii multicolor pharoahensis funestus, arabiensis stephensi minimus funestus and and gambiae s.s. arabiensis albimanus culicifacies sundaicus melas nunez-tovari arabiensis funestus and dirus gambiae s.s. annularis punctulatus group aquasalis gambiae s.s. maculatus and funestus gambiae s.s. flavirostris darlingi pseudopunctipennis barbirostris farauti

freeborni

quadrimaculatus

labranchiae

arabiensis and funestus

No vector albimanus annularis anthropophagus arabiensis arabiensis and funestus aquasalis atroparvus

barbirostris culicifacies darlingi dirus farauti flavirostris fluviatilis freeborni

funestus and arabiensis funestus, arabiensis, and gambiae s.s. funestus and gambiae s.s. gambiae s.s. gambiae s.s. and funestus labranchiae maculatus marajoara

melas messeae minimus multicolor nunez-tovari punctulatus group pharoahensis pseudopunctipennis

Figure 43-4. Global distribution of malaria vectors. (From Kiszewski A, Mellinger A, Spielman A, et al: Am J Trop Med Hyg 70:486–498, 2004, with permission.)

pulcherrimus quadrimaculatus sacharovi sergentii sinensis stephensi sundaicus superpictus

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TABLE 43-3. Clinical Manifestations and Complications of Human Plasmodium Infection PLASMODIUM SPECIES

Figure 43-5. Malaria parasite life cycle. During the malarial parasite life cycle, sporozoites are transmitted through the bite of a nocturnal-feeding female Anopheles mosquito (A). Sporozoites then migrate to the liver (B) and mature to merozoites (C).A subset of P.vivax and P.ovale parasites remains dormant as hypnozoites emerging months to years after the initial infection to cause disease. Eight to 25 days after the initial infection, 10,000 to 30,000 merozoites are released to invade erythrocytes (D). Asexual parasites mature in 48 to 72 hours, each releasing 6 to 24 merozoites to invade more erythrocytes (E). Some parasites develop into gametocytes (sexual stages), which are taken up during a mosquito blood meal. Diploid zygotes form ookinetes and develop into haploid sporozoites (F). The sporozoites migrate to the mosquito salivary gland and continue the life cycle in humans with the next blood meal. (From Sheral S. Patel, with permission.)

viduals who have recently arrived from endemic areas, such as immigrants and refugees, may be asymptomatic or have jaundice or signs of hepatosplenomegaly. Laboratory studies may reveal anemia and thrombocytopenia. Perinatal transmission of malaria is usually caused by P. falciparum and P. vivax. Clinical manifestations of congenital malaria can mimic neonatal sepsis and include fever, poor appetite, irritability, and lethargy.

Complications of P. falciparum Infection with P. falciparum has a greater risk for complications and death than does infection with the other three human malarial species. First, P. falciparum can invade erythrocytes of all ages and thus produce overwhelming parasitemia. Second, P. falciparum–infected red blood cells adhere to endothelial cells, leading to microvascular pathology not observed with other malarial species.22 Third, P. falciparum is frequently resistant to antimalarials (see Figure 43-1A and B and Figure 43-2). Travelers from nonendemic areas, children, and pregnant women are at greatest risk for developing complications from malaria infection. A person is considered to have complicated malaria when the presenting signs include altered mental status, seizures, profound anemia, respiratory distress, gross hematuria, shock, or severe laboratory abnormalities, including hypoglycemia, acidosis, signs of disseminated intravascular coagulation, or hyperparasitemia (see Table 43-3). These are summarized as follows: • Cerebral malaria: Acute neurologic events such as seizures, obtundation, and coma are associated with cerebral malaria. Cerebrospinal fluid examination is typically unremarkable, thus differentiating cerebral malaria from bacterial meningi-

MANIFESTATIONS AND COMPLICATIONS

All species

Fever, chills, rigors, sweats, headache Weakness Myalgias Vomiting Diarrhea Hepatomegaly Splenomegaly Jaundice Anemia Thrombocytopenia

P. falciparum

Hyperparasitemia Cerebral malaria: seizures, obtundation, coma Severe anemia Hypoglycemia Acidosis Renal failure Pulmonary edema (noncardiogenic) Vascular collapse

P. vivax and P. ovale

Splenic rupture Relapse months to years after primary infection because of latent hepatic stages

P. malariae

Low-grade fever, fatigue Chronic asymptomatic parasitemia Immune complex glomerulonephritis

tis. Pathogenesis is a result of microvascular obstruction by parasitized erythrocytes, but neurologic impairment can result from multiple factors, including hypoglycemia, acidosis, impaired cerebral oxygenation from anemia, and pulmonary edema.33 The mortality rate can be as high as 15% to 30% in endemic areas, and higher in nonimmune adults, such as travelers. Children surviving episodes of cerebral malaria often have subtle cognitive and motor deficits.37 • Severe anemia: Overwhelming parasitemia (>106 parasitized red blood cells/µL or >20% parasitized circulating red blood cells) can develop rapidly in nonimmune individuals, resulting in severe anemia (hemoglobin, 60 mg/dL >3 times normal Serum total bilirubin >2.5 mg/dL >500,000 parasites/mL or >10,000 mature trophozoites and schizonts/mL Hemoglobin viruses.

is allowed to sit without agitation. After sediment has formed on the bottom of the container, the clear water is decanted or filtered from the top. The time required depends on the size of the particle. Generally, 1 to 3 hours are adequate for large particles such as inorganic sands and silts. Microorganisms, especially protozoal cysts, eventually settle; reductions up to 90% may be achieved overnight or in 1 to 2 days.43 However, the organisms are easily disturbed during pouring or filtering. Reservoirs take advantage of sedimentation to improve microbiologic quality. In conclusion, sedimentation is often effective in reducing water turbidity and improves microbiologic quality, but it is not recommended as the sole means of disinfection.

Coagulation-Flocculation Smaller suspended particles and chemical complexes too small to settle by gravity are called colloids. Most of these can be removed by chemical precipitation, known as coagulationflocculation, a technique that has been used to remove unpleasant color, smell, and taste in water since 2000 bc. This technique is used routinely in large municipal disinfection plants, but is simple enough to be used at the household level and in the outdoors209 (Box 61-8). Coagulation is achieved with addition of an appropriate chemical that alters the physical state of dissolved and suspended solids, causing particles to stick together on contact because of electrostatic and ionic forces.47,230 Aluminum salts (alum), iron, and lime (alkaline chemicals principally containing calcium or magnesium and oxygen) are commonly used, readily available coagulants. Rapid mixing is important to obtain dispersion of the coagulant. The second stage, flocculation, is a purely physical process obtained by prolonged gentle mixing to increase interparticle collisions and promote formation of larger particles. The flocculate particles can be removed by sedimentation and filtration. Coagulation-flocculation removes most coliform bacteria (60% to 98%), viruses (65% to 99%),55,174,208 Giardia (60% to 99%), helminth ova (95%),203 heavy metals, dissolved phosphates, and minerals.47,126,230,249 Organic and inorganic compounds may be removed by forming a precipitate or by adsorbing onto aluminum hydroxide or ferric hydroxide floc particles.230 Despite removal of most microorganisms, a subsequent disinfection step is advised. The sequential use of coagulation and activated carbon is often beneficial. Coagulation generally removes large molecules that absorb poorly on granular activated carbon (GAC). On the

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other hand, carbon has limited effectiveness for removing organic matter from water.6 To clarify water by coagulation-flocculation in the field, add 10 to 30 mg of alum per liter of water. The exact amount is not important, so it can be done with a pinch of alum, lime (calcium oxide), or both for each gallon of water, using more if the water is very cloudy. Next, stir or shake briskly for 1 minute to mix the coagulant, then agitate gently and frequently for at least 5 minutes to assist flocculation. Settling requires at least 30 minutes, after which the water is carefully decanted or poured through a cloth or paper filter. The process can be repeated, if necessary. Finally, filtration or halogenation should be used to ensure disinfection.

Toxicity Questions have been raised concerning the association of aluminum with central nervous system toxicity in mammals, but these effects have been observed only after exposures other than ingestion. Most of the aluminum in alum is removed with the floc. A report from the National Academy of Sciences concluded that aluminum in drinking water does not present a significant risk.230 Alum is a common chemical used by the food industry in baking powder and for pickling. It can be found in some food stores or at chemical supply stores.

Alternative Agents Many inorganic and organic compounds can be used as a coagulant, including lime (calcium oxide) or potash (from wood ash). In an emergency, baking powder or even the fine white ash from a campfire can be used.233 Other coagulation-flocculation agents used traditionally by native peoples include seed extracts from the nirmali plant in southern India, or moringa plants in Sudan, crushed almonds or dried, crushed beans, and rauwaq (a form of bentonite clay).43

Adsorption Adsorbents such as charcoal, clay, and other types of organic matter have been used for water treatment since biblical times.119 These processes are often combined with filtration or coagulation, because these substances are used as the filter media and act as coagulants.209 Clays can decrease turbidity and microbes in water by about 90% to 95%, but the process is difficult to control and adsorption is not the main action of ceramic or clay filters. Vegetative matter, including burnt rice hulls and activated (burnt) coconut shell, also have adsorptive capacity.

Granular Activated Carbon (Charcoal) Granular charcoal is widely used for water treatment and for medical detoxification. When activated, charcoal’s regular array of carbon bonds is disrupted, yielding free valences that are highly reactive and adsorb dissolved chemicals.78,194 GAC is the best means to remove toxic organic and inorganic chemicals from water (including disinfection byproducts) and to improve odor and taste.146,230 Thus, it is widely used in municipal disinfection plants and in home under-sink devices. Compressed into block form that acts both as a depth filter and an adsorbent, GAC is a common component of field filters. Block carbon is more effective than granular because the passages are smaller, forcing closer contact with the carbon.

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Many viral particles and bacteria adhere to GAC,146 and some cysts are trapped in the matrix.126 However, using a bed of GAC to filter particles and microorganisms results in more rapid saturation of binding sites and clogs the bed. Dissolved organic matter in water takes up adsorption sites and bacteria colonize GAC, forming a biofilm that can slough off into the effluent water. GAC does not kill microorganisms; in fact, bacteria attached to charcoal are resistant to chlorination because the chlorine is adsorbed by the GAC.119,146,230 This bacterial contamination has not been found to be harmful because the usual heterophilic bacteria are not enteric pathogens. Enteric pathogens have been shown to survive on GAC, but if an active biofilm exists, the pathogens are rapidly displaced by heterophilic bacteria and fail to become established. Therefore, nonpathogenic bacterial colonization is encouraged in municipal plants.178 However, these properties of carbon indicate that it will not reduce pathogenic microbes in water over an extended period of time, and an alternative means of disinfection should always be used. Eventually, the binding sites on the carbon particles become saturated and no longer adsorb; some molecules are released as others preferentially bind.146 Unfortunately, no reliable means are available to determine precisely when saturation is reached. Filters using charcoal in compressed block form as the filter element may clog before the charcoal is fully adsorbed. Presence of unpleasant taste or color in the water can be the first sign that the charcoal is spent. To test the charcoal, filter iodinated water or water tinted with food coloring. With regular use the lifetime of GAC is probably measured in months; it is substantially longer with infrequent use. GAC can be “recharged,” but this is not practical for small-quantity use. Ingested particles of charcoal are harmless. GAC can be used before or after disinfection. Before disinfection, GAC removes many organic impurities that result in bad odor and taste. GAC is best used after chemical disinfection to make water more palatable by completely removing the halogen146,244 and other chemical impurities. With increasing industrial and agricultural contamination of distant groundwater, final treatment of drinking water with GAC may be a necessity for some wilderness users. GAC also removes radioactive contamination.

Filtration Filters are appealing and amenable to commercial production. They have the advantages of being simple and requiring no holding time (Box 61-9). They do not add any unpleasant taste and may improve taste and appearance of water. However, they take space and add weight to baggage. All filters eventually clog from suspended particulate matter, present even in clear streams, requiring cleaning or replacement of the filter. As a filter clogs, it requires increasing pressure to drive the water through, which can force microorganisms through the filter. A crack or eroded channel allows passage of unfiltered water. Filtration is a standard step in municipal disinfection. Many different types of media, from sand to vegetable products to fabric, have been used throughout history in various parts of the world. Filtration is both a physical and a chemical process, so many variables influence filter efficiency. The characteristics of the filter media and the water, as well as flow rate, determine the interactions. Filtration can reduce turbidity, bacteria,

Box 61-9. Filtration Advantages Simple to operate Mechanical filters require no holding time for treatment (water is treated as it comes out of the filter) Large choice of commercial products Adds no unpleasant taste and often improves taste and appearance of water Rationally combined with halogens for removal or destruction of all pathogenic water-borne microbes

Disadvantages Adds bulk and weight to baggage Most filters not reliable for removal of viruses

Expensive relative to chemical treatment Channeling of water or high pressure can force microorganisms through the filter Eventually clogs from suspended particulate matter; may require some maintenance or repair in field

Susceptibility of microorganisms to filtration: protozoa > bacteria > viruses.

algae, viruses, color, oxidized iron, manganese, and radioactive particles.55 The size of a microorganism is the primary determinant of its susceptibility to filtration (Table 61-7 and Fig. 61-1). Filters are rated by their ability to retain particles of a certain size, which is described by two terms. Absolute rating means that 100% of a certain size of particle is retained. Nominal rating indicates that more than 90% of a given particle size will be retained. Filter efficiency is generally determined with hard particles (beads of known diameter), but microorganisms are soft and compressible under pressure. Water-borne pathogens often adhere to larger particles or clump together, making them easier to remove by physical processes. Therefore, observed reductions are often greater than expected based on their individual sizes.209 A membrane with pore size of 0.2 µm can remove enteric bacteria. Giardia and E. histolytica cysts are easily filtered, requiring a maximum filter size of 5 µm. Cryptosporidium cysts are somewhat smaller than Giardia and more flexible; 57% are able to pass through a 3-µm membrane filter, so a filter with 1to 2-µm pores is recommended.190 Helminth eggs and larvae, which are much larger, can be removed by a 20-µm filter. Cyclops (the water-dwelling copepod that ingests the larva and transmits dracunculosis) can be removed by passage through a fine cloth.203 Many filters constructed with various designs and materials are marketed for field use. Surface, membrane, and mesh filters are very thin with a single layer of fairly precise pores, whose size should be equal to or less than the smallest dimension of the organism. These filters provide little volume for holding contaminants and thus clog rapidly, but they can be cleaned easily by washing and brushing without destroying the filter. Maze or depth filters depend on long, irregular labyrinths to trap the organisms, so they may have a larger pore or passage size. Con-

Chapter 61: Field Water Disinfection

Size (microns) 0.001

0.01

0.1

1.0

10

1381

100

1,000

Visible to naked eye Beach sand Protozoan cysts

Figure 61-1. Relative size of microorganisms determines susceptibility to mechanical filtration. (Courtesy Dan Vorhis.)

Bacteria Viruses Colloidal clays and particles Organic compounds that add “tea” color to water Pesticides, taste and odor compounds Dissolved salts, metal ions

TABLE 61-7. Microorganism Susceptibility to Filtration ORGANISM Viruses Escherichia coli Campylobacter Microsporidia Cryptosporidium oocyst Giardia cyst Entamoeba histolytica cyst Cyclospora Nematode eggs Schistosome cercariae Dracunculus larvae

AVERAGE SIZE (mm)

MAXIMUM RECOMMENDED FILTER RATING (mm)

0.03 0.5 × 3–8 0.2–0.4 × 1.5–3.5 1–2 2–6 6–10 × 8–15 5–30 (average 10) 8–10 30–40 × 50–80 50 × 100 20 × 500

N/S 0.2–0.4 Same as above N/S 1 3–5 Same as Giardia Same as Giardia 20 Coffee filter or fine cloth Coffee filter or fine cloth

N/S, not specified.

taminants adhere to the walls of the passageway or are trapped in the numerous dead-end tunnels. Granular media, such as sand or charcoal, diatomaceous earth, or ceramic filters, function as maze filters. A depth filter has a large holding capacity for particles and lasts longer before clogging but may be difficult to clean effectively, in that many particles are trapped deep in the filter. Flow can be partially restored to a clogged filter by back flushing or surface cleaning, which removes the larger particles trapped near the surface. For ceramic filters, surface cleaning is highly effective but removes a tiny layer of the filter medium. Portable filters can readily remove protozoan cysts and bacteria but may not remove viruses, which are another order of magnitude smaller than bacteria. Only the semipermeable membranes in reverse-osmosis filters are inherently capable of removing viruses. However, adsorption and aggregation during passage through mechanical filters reduce viruses. Virus parti-

cles may adhere to the walls of diatomite (ceramic) or charcoal filters by electrostatic chemical attraction, which can be enhanced by a coating on the filter or a positive charge.65,79,82,178 Viruses in heavily polluted water often aggregate in large clumps and become adsorbed to particles or enmeshed in colloidal materials, making them amenable to filtration.174,230 Thus turbidity (cloudiness from contaminants) may help remove pathogens with filtration, while it inhibits chemical disinfection. In one study, however, only 10% of total virus particles detected were recovered on 3- to 5-µm pore prefilters, suggesting that most were not associated with the suspended sediment.153 Furthermore, adsorbed viral particles can be subsequently dislodged and eluted from a filter due to competitive binding and competing electrostatic forces.79,170,227 Some ceramic filters now remove 99% to 99.9% of viruses, but the fourth log required by water treatment units remains a challenge. The First Need filter (General Ecology, Exton, PA) has

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been able to meet the EPA standards for water purifiers, including 4-log removal of viruses, apparently through use of a charged media82 (Appendix A). In general, however, mechanical filters should not be considered adequate for complete removal of viruses, except with special equipment.242 For domestic use and in pristine protected watersheds where pollution is minimal and the main concerns are bacteria and cysts, filtration can be used as the only means of disinfection. For foreign travel and for surface water with high levels of human use or sewage contamination, however, most filters should not be used as the sole means of disinfection.65 Additional treatment with heat or halogens before or after filtration guarantees effective virus removal.178 One rational use of filtration is to clear the water of sediment and organic debris, allowing lower doses of halogens with more predictable residual levels.146 Filters are also useful as a first step to remove parasitic and Cryptosporidium organisms that have high resistance to halogens. Filtration using simple, available products is of interest for use in developing countries and in emergency situations.209 Sand filtration is still used widely in municipal plants. A column of fine sand 60 to 75 cm deep that permits flow of no more than 200 L/m2/hr is capable of removing turbidity and greater than 99% of organisms.176 These can be improvised with stacked buckets or barrels. Rice hull ash filters, crushed charcoal, sponges, and various fabrics have all been used. Typically, bacteria and viruses can be reduced by as much as 50% to 85% or more, and larger parasites by 99%, depending on the media. Fine woven cotton fabric is effective at removing larger parasites, such as schistosoma cercariae, Fasciola species, and guinea worm larvae. Kozlicic tested five commonly available household materials (newspaper, filter paper, cotton, four-layer gauze, and white cotton cloth) for filtration efficiency. Newspaper performed poorly, being too slow. Cotton cloth performed best for both physical and microbiologic parameters of water (although the latter was poorly studied). He incidentally noted that melted snow with the top 4 to 5 cm removed was a better quality water source than rain water from roof runoff.114

Reverse Osmosis A reverse-osmosis filter uses high pressure (100 to 800 psi) to force water through a semipermeable membrane that filters out dissolved ions, molecules, and solids.230 This process can desalinate water, as well as remove microbiologic contamination. If pressure or degradation causes breakdown of the membrane, treatment effectiveness is lost. Even Giardia cyst passage has been shown to occur in a compromised reverse-osmosis unit.53 Small hand-pump reverse-osmosis units have been developed. Their high price and slow output currently prohibit use by landbased wilderness travelers, but they are important survival items for ocean travelers. Battery- or power-operated units are standard equipment on large boats. The U.S. Department of Defense uses large-scale mobile reverse-osmosis units for water treatment. These are considered the most fuel-efficient mobile units, producing the highest quality water from the greatest variety of raw water qualities and capable of producing potable water from fresh, brackish, or salt water, as well as from water contaminated by nuclear, biologic, or chemical agents. The units use pretreatment, filtration, and desalination, then disinfection for storage.233

Silver Impregnation Silver impregnation of filters neither prevents microbial contamination of the filter nor sustains its action as a bactericide in the effluent water.11 Although silver has some antibacterial effect on coliform organisms, filter cartridges impregnated with silver typically become colonized with heterotrophic bacteria, which increase the total bacterial count in the effluent water but which have not been linked to increased illness.11,65,78,178 In GAC filters designed to operate in line with chlorinated tap water, silver merely exerts selective pressure on the kinds of bacteria that will colonize the filter. Colonization of filters with pathogenic coliforms has not been demonstrated, but protective effect cannot be attributed to silver impregnation.65,178

Commercial Devices Using Mechanical Filtration See EPA standards already described. Portable water treatment products are the third highest intended purchase of outdoor equipment after backpacks and tents.106 Some are designed as purely mechanical filters, whereas others combine filtration with GAC. Most of the filters containing iodine resins have been withdrawn from the market. There is currently only one drinkthrough bottle using an iodine resin (see the discussion of halogens and Appendix A). The ceramic filters have been tested most extensively and generally consistently perform well.65,156,227 Results may not apply to all ceramic filters because efficacy depends on the characteristics of the ceramic, water quality, product engineering, and prior extent of filter use. Few comparable data are available on different filters. Most data are from testing organized by one filter manufacturer, so the results are not generally accepted, despite nearly all filters performing well. Schlosser tested three hand-pump filters (Katadyn Mini Ceramic, First Need Deluxe, and Sweetwater Walkabout), all of which removed 3-log (99.9%) or more of viable bacteria, leaving none in the effluent.200 The military preventive medicine group has enumerated the requirements for individual filters for field use.229


HALOGENS Worldwide, chemical disinfection is the most widely used method for improving and maintaining microbiologic quality of drinking water. Chemical disinfectants used for water disinfection are strong oxidants. Halogens, chiefly chlorine and iodine, are the most common chemical disinfectants used in the field; however, chlorine dioxide is now available in small use applications and is gaining acceptance. Germicidal activity results from oxidation of essential cellular structures and enzymes.40,118,146,151 Halogenated amines may be synthesized by white blood cells as part of the body’s natural defenses to destroy microorganisms.243 The disinfection process is determined by characteristics of the disinfectant, the microorganism, and environmental factors.42,96,145 Dilute solutions do not sterilize water. The relative potency of common disinfectants to inactivate water-borne microbes is as follows: ozone > chlorine dioxide > electrochemically generated mixed species oxident > free chlorine or iodine > chloramine Ozone and chlorine dioxide are discussed under Miscellaneous Disinfectants.

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TABLE 61-8. Factors Affecting Halogen Disinfection

Primary Factors Concentration Contact time Secondary Factors Temperature

Water contaminants, cloudy water (turbidity) pH

EFFECT

COMPENSATION

Measured in milligrams per liter (mg/L) or the equivalent, parts per million (ppm); higher concentration increases rate and proportion of microorganisms killed. Usually measured in minutes; longer contact time assures higher proportion of organisms killed.

Higher concentration allows shorter contact time for equivalent results. Lower concentration requires increased contact time. Contact time is inversely related to concentration; longer time allows lower concentration

Cold slows reaction time.

Some treatment protocols recommend doubling the dose (concentration) of halogen in cold water, but if time allows, exposure time can be increased instead, or the temperature of the water can be increased. Doubling the dose of halogen for cloudy water is a crude means of compensation that often results in a strong halogen taste on top of the taste of the contaminants. A more rational approach is to first clarify water to reduce halogen demand.

Halogen reacts with organic nitrogen compounds from decomposition of organisms and their wastes to form compounds with little or no disinfecting ability, effectively decreasing the concentration of available halogen. In general, turbidity increases halogen demand. The optimal pH for halogen disinfection is 6.5 to 7.5. As water becomes more alkaline, approaching pH 8.0, much higher doses of halogens are required.

Most surface water is neutral to slightly acidic, so compensating for pH is not necessary. Tablet formulations of halogen have the advantage of some buffering capacity.

Variables with Halogenation Understanding the principal factors of halogen disinfection allows intelligent and flexible use (Table 61-8). The major variables in the disinfection reaction with chlorine or iodine are the amount of halogen (concentration) and the exposure time of the microorganism to the halogen disinfectant (contact time). Concentration of halogen in water is measured in parts per million (ppm) or milligrams per liter (mg/L), which are equivalent. Contact time is usually measured in minutes but ranges from seconds to hours. In field disinfection, concentrations of 1 to 10 mg/L for 10 to 60 minutes are generally effective. Theoretically, the disinfection reaction follows first-order kinetics. The rate of the reaction is determined by the initial concentration of reactants, and a given proportion of the reaction occurs in any specified interval.96,244 This means concentration and time are inversely related, and their product results in a constant for specified disinfectant, organism, percent reduction of viable microorganisms, and given conditions of water temperature and pH: concentration × time = constant (Ct = K) (Fig. 61-2).244 When concentration and contact time are graphed on logarithmic coordinates, a straight line results. This means that concentration and time can be varied oppositely and still achieve the same result.9 In field disinfection, this can be used to minimize halogen dose and improve taste or to minimize the required contact time. In reality, the disinfection reaction deviates from first-order kinetics, and Ct values do not follow the exponential rates described by the empiric equation because microorganisms do not act as chemical reagents (Cnt = K). An initial lag period may be seen before inactivation begins (e.g., because of penetration of the cyst wall), and inactivation declines for more resistant

Iodine (mg/L)

Concentration and Contact Time

E. histolytica cyst 10

E. coli 1.0 Polio virus

0.1 1.0

10

100

Contact time (min)

Figure 61-2. Relationship of halogen concentration and contact time for a given temperature and pH. The first-order chemical reaction results in a straight line over most values for each microorganism and halogen compound. (Data from Chang SL: J Am Pharm Assoc 47:417, 1958; and Water and Sanitation for Health [WASH] Project: Report on mobile emergency water treatment and disinfection units,WASH Field Report No 217, Arlington,VA, 1980.)

organisms or those protected by aggregation or association with other particulate matter (Fig. 61-3).87,91,96

Contaminants The quality of the water to be disinfected influences microbial inactivation by chemical disinfectants. Organic and inorganic nitrogen compounds from decomposition of organisms and their wastes, fecal matter, and urea complicate disinfection with halogens and must be considered in field water treatment.

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PART EIGHT: FOOD AND WATER

Cyst inactivation (%) 100 30°C 80

2 ppm iodine

15°C 5°C

60 40 20 0

0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240

4 ppm iodine 100 80

30°C 15°C

5°C

60 40 20 0 0 100

15

30

45

30

45

15°C 30°C

60 75 8 ppm iodine

90

105

120

90

105

120

80 5°C 60 40 20 0 0

15

60

75

Time (min)

Figure 61-3. Effect of concentration and temperature on Giardia cyst inactivation by iodine. Low concentrations are effective at cold temperatures with prolonged contact time. ppm, parts per million. (From Fraker LD, et al: J Wilderness Med 3:351, 1992.)

Vegetable matter, ferrous ions, nitrites, sulfides, and humic substances also affect oxidizing disinfectants.62,146,244 These contaminants react with halogens, especially chlorine, to form compounds with little or no disinfecting ability, effectively decreasing the concentration of available halogen.

Halogen Demand and Residual Concentration Halogen demand is the amount of halogen reacting with impurities. Residual halogen concentration is the amount of active

halogen remaining after halogen demand of the water is met. To achieve microbial inactivation in aqueous solution with a chemical agent, a residual concentration must be present for a specified contact time. Failure of chlorination in municipal systems to kill cysts or other microorganisms is usually caused by difficulty maintaining adequate residual halogen concentration and contact times, rather than by extreme resistance of the organism.217 Halogen demand and residual concentration of surface water are the greatest uncertainties in field disinfection. Nitrogen appears in most natural waters in varying amounts, which relate directly to the sanitary quality of water. Cysticidal dose of halogens is strongly affected by the level of contamination (cyst or viral density) in otherwise clean water.42,85,217 Scant data are available on halogen demand of surface water (Table 61-9). Clear water is assumed to have minimal demand and cloudy water high demand. Surface water in the wilderness contains 10 times the organic carbon content of aquifer groundwater. The green or brown color in stagnant ponds or lakes or in tropical and lowland rivers is usually caused by organic matter with considerable halogen demand. In some cases, such as runoff after storms and snowmelt, cloudy water may be caused by inorganic sand and clay that exert little halogen demand. In general, chlorine demand rises with increased turbidity.120 In addition, particulate turbidity can shield microorganisms and interfere with disinfection.55,109,120 (See previous discussion of turbidity.) The initial dose of halogen must consider halogen demand. For clear alpine waters, 1 mg/L demand can be assumed; for cloudy waters, the assumption is 3 to 5 mg/L. If a method is used that adds 4 mg/L to clear water, extra time can compensate for the lower expected residual concentration. In cloudy water, however, where the demand may be nearly 4 mg/L, an increased dose of halogen, rather than prolonging the contact time, is needed to ensure free residual. The usual field recommendation to compensate for the unknown demand of cloudy water is a double dose of halogen (to achieve 8 to 16 mg/L). This crude means of compensation often results in a strong halogen taste on top of the taste of the contaminants. If the cause of turbidity is uncertain, the water should be allowed to sit; inorganic clay and sand will sediment, clarifying the water considerably. Other means of clarification, such as coagulationflocculation or filtration, significantly reduce halogen demand. (See clarification techniques.) Several simple color tests (most often used to test swimming pools and spas) measure the amount of free (residual) halogen in water. Testing in the wilderness for halogen residual may be reasonable for large groups but is not practical for most. Smell of chlorine usually indicates some free residual. Color and taste of iodine can be used as indicators. Above 0.6 ppm, a yellow to brown tint is noted.244

pH and Temperature Two other variables in the disinfection reaction are pH and temperature.62,118,146

pH. Halogen oxidizes water to form several compounds, each with different disinfection capabilities. The percentage of each halogen compound is determined by pH. The optimal pH for halogen disinfection is 6.5 to 7.5.42,144 As water becomes more alkaline, approaching pH 8.0, much higher doses of halogens are required.

Chapter 61: Field Water Disinfection

1385

TABLE 61-9. Halogen Demand of Surface Water SOURCE Cloudy river water, Portland, Oregon Cloudy water from clay particles Clear water with 10% sewage added Lily pond and turbid river water Colorado River; cloudy from inorganic sand, clay Unspecified surface waters Municipal wastewater High-elevation spring Western river Six watersheds in western Oregon Small stream, Australia Bolivian village (well and collected rain)

Although pH can be measured in the field, the relationship is too complex to allow meaningful use of the information. Most surface water pH is neutral to mildly acidic, which is within the effective range of the halogens used. Granite keeps many alpine waters mildly acidic. Unfortunately, acid rain is affecting some high mountain lakes.135 The EPA found the average pH in western alpine lakes to be no less than 5.5; other U.S. lakes are beginning to show lower pH levels. On the alkaline side, some surface water with pH 7.0 to 8.0 begins to affect the chemical species of chlorine, favoring less active forms.96 Certain desert water is so alkaline that halogens would have little activity; however, these waters are usually not palatable. At this time, compensating for pH is not necessary. Tablet formulations of halogen have the advantage of some buffering capacity.

Temperature. Temperature influences the rate of the disinfection reaction. Cold water affects germicidal power and must be offset by longer contact time or higher concentration to achieve comparable disinfection.84 The common rule is a twofold to threefold increase in inactivation rate per 10° C (18° F) increase in temperature. Unusual retardation of rates as temperatures approach 0° C (32° F) has not been seen.96 Temperature can be estimated in the field. Some treatment protocols recommend doubling the dose of halogen in cold water, but if there is no urgency, time can be increased instead of dose. Data for killing Giardia in very cold water (5° C [41° F]) with both chlorine and iodine indicate that contact time must be prolonged three to four times, not merely doubled, to achieve high levels of inactivation.73,92 If feasible, raising the temperature by 10° to 20° C (18° to 36° F) allows a lower dose of halogen and more reliable disinfection at a given dose.

Susceptibility of Microorganisms The final variable is the target microorganism. Sensitivity to halogen is determined by the diffusion barrier of the cell wall or capsule and the relative susceptibility of proteins and cellular respiration to denaturation and oxidation.40,146 Organisms, in order of increasing resistance to halogen disinfection, are enteric (vegetative) bacteria, viruses, protozoan cysts, bacterial spores, and parasitic ova (Tables 61-10 and 61-11); for example, E. histolytica cysts are 160 times as resistant as E. coli and 9 times as resistant as hardier enteroviruses to chlorine (hypochlorous acid [HOCl]). Virucidal residuals of I2 and HOCl are 5 to 70

HALOGEN DEMAND (mg/L)

REFERENCE

3–4 none 2 5–6 0.3 2–3 20–30 0.3 0.7 0.4–1.6 1.3 2

Jarroll, 1980102 Chang, 195346 Chang, 195346 Chang, 195346 Tunnicliff, 1984228 Culp, 197454 Culp, 197454 Ongerth, 1989140 Ongerth, 1989140 LeChevallier, 1981117 Thomson, 1985297 Quick, 1999364

times higher than bactericidal residuals.40,146 Relative resistance between organisms is similar for iodine and chlorine. The physical state of the microbes also determines their susceptibility. Microbes that are aggregated in clumps or embedded in other matter or organisms may be shielded from disinfectants.

Bacteria All vegetative bacteria are extremely sensitive to halogens. Inactivation involves oxidation of enzymes on the cell membrane and does not require penetration.244 Little modern work has focused on bacterial agents because they are more sensitive than viruses and cysts, and little difference is evident between the bacterial pathogens.96 Although halogens were first used to disinfect water during cholera epidemics in 1850, recent cholera epidemics prompted review of data that reaffirmed the susceptibility of V. cholerae to low levels of chlorine and iodine.52 Campylobacter has susceptibility similar to that of other enteric pathogens.20 Bacterial spores, such as Bacillus anthracis, are relatively resistant to halogens, but with chlorine, spores are not much more resistant than are Giardia cysts.9,244 Quantitative data are not available for iodine solutions, but iodine does kill spores. Fortunately, sporulating bacteria do not normally cause waterborne enteric disease.94

Viruses

Enteroviruses are more resistant than are enteric bacteria,146 but they constitute such a large and diverse group of organisms that generalization is especially difficult.41,118,230 Most studies have used poliovirus, a phage virus, or coxsackievirus. The mechanism of action for halogen inactivation of viruses has not been resolved. It is not clear whether the oxidant injures protein on the shell, a process similar to bacterial inactivation,26 or penetrates the protein capsid by chemical transformation and then attacks the nucleic acid core, as in cyst inactivation.244 Most viruses tested against chlorine have shown resistance 10 times greater than that of enteric bacteria, but inactivation is still achieved rapidly (0.3 to 4.5 minutes) with low levels (0.5 mg/L) of chlorine.63,234 Current data suggest that HAV is not significantly more resistant than other enteric viruses.85,163,211,224 In one test using iodine tablets, HAV was inactivated under difficult conditions more readily than poliovirus or echovirus.210 Norovirus may be more resistant to chlorine

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PART EIGHT: FOOD AND WATER

TABLE 61-10. Disinfection Data for Chlorine ORGANISM

CONCENTRATION (mg/L)

TIME (min)

HOCl FAC FRC Free Cl FRC Free Cl HOCl FRC Free Cl Free Cl

Escherichia coli Campylobacter 20 enteric virus 6 enteric viruses Hepatitis A virus Hepatitis A virus Amebic cysts Amebic cysts Giardia cysts G. lamblia cysts

0.1 0.3 0.5 0.5 0.5 0.5 3.5 3.0 2.5 0.85

0.16 0.5 60 4.5 1 5 10 10 60 90

Free Cl Free Cl Free Cl Free Cl Free Cl FRC

3.05 5.87

50 25

Free Cl

G. muris cysts G. muris cysts Giardia Giardia Cryptosporidium Schistosome cercariae Nematodes

Free Cl

Nematodes

95–100

30

FRC

Ascaris eggs

200

20

HALOGEN*

80 1.0

90 30

2–3

120

pH

TEMP

6.0 6.0–8.0 7.8 6.0–8.0 6.0 6.0

7.0 7.0 6.0 6.0

5° C (41° F) 25° C (77° F) 2° C (36° F) 5° C (41° F) 25° C (77° F) 5° C (41° F) 25° C (77° F) 30° C (86° F) 5° C (41° F) 2–3° C (36–37° F) 5° C (41° F) 5° C (41° F) 0.5° C (32° F) 5° C (41° F)

7.0

28° C (82° F)

7.0 6.0–8.0 8.0

DISINFECTION CONSTANT (Ct)

White, 1992210 Blaser, 198630 Briton, 198025 Engelbrecht, 198066 Grabow, 198384 Sobsey, 1975181 Chang, 197044 Stringer, 1970186 Rice, 1982182 Wallis, 1988240

0.16 0.15 30 2.5 0.5 2.5† 35 30 150 77 153 139 170 120 7200 30 (not lethal) (95% lethal)

5.0

37° C (99° F)

REFERENCE

2000

Rubin, 1989196 Rubin, 1989196 Hibler, 198789 Hibler, 198789 Korich, 1990354 World Health Organization, 1981217 National Academy of Sciences, 1980131 National Academy of Sciences, 1980131 Krishnaswami, 1968112

HOCl, hypochlorous acid; FAC, free active chlorine; Free Cl, free chlorine; FRC, free residual chlorine. *These represent nearly equivalent measurements of the residual concentration of active chlorine disinfectant compounds. † Four log reduction. Most experiments use 2 to 3 log (99% to 99.9%) reduction as end point.

TABLE 61-11. Disinfection Data for Iodine ORGANISM

CONCENTRATION (mg/L)

FRI

Escherichia coli

1.3

I2 I2 I2 FRI FRI I2 I2 I2 I2 FRI FRI FRI

Amebic cysts Amebic cysts Amebic cysts Poliovirus 1 Poliovirus 1 Poliovirus 1 Coxsackie virus Amebic cysts Bacteria, viruses Giardia cysts Giardia cysts Giardia cysts

3.5 6.0 12.5 1.25 12.7 1 0.5 8 8 4 4 4

HALOGEN*

TIME (min) 1 10 5 2 39 5 6 30 10 20 15 45 120

pH

TEMP (° C)

6.0–7.0

2–5° C (36–41° F)

6.0 6.0 7.0 7.0 4.0–8.0 5.0 5.0 5.0

25° C (77° F) 25° C (77° F) 25° C (77° F) 25° C (77° F) 25° C (77° F) 18° C (64° F) 5° C (41° F) 23° C (73° F) 0–5° C (32–41° F) 30° C (86° F) 15° C (59° F) 5° C (41° F)

DISINFECTION CONSTANT (Ct) 1.3 35 30 25 49 63 6 15 80 160 60† 170† 480†

REFERENCE National Academy of Sciences, 1980131 Chang, 197044 Chang, 197044 Chang, 197044 Berg, 196413 Berg, 196413 Berg, 196413 Berg, 196413 Chang, 195346 Chang, 195346 Fraker, 199273 Fraker, 199273 Fraker, 199273

*FRI (free residual iodine) and I2 (elemental iodine) are nearly equivalent measurements of the residual concentration of active iodine disinfectant compounds. † 100% kill; viability tested only at 15, 30, 45, 60, and 120 minutes.

than several other viruses, which may account for its importance in water-borne outbreaks.111 Powers and colleagues167,169 found that poliovirus was more slowly inactivated than rotavirus and Giardia muris by both chlorine and iodine, but this is inconsistent with other data. Clumping and association of viruses with cells and particulate matter are thought to be significant factors affecting viral disinfection, causing departure

from first-order kinetics.63,210,234 Cell-associated HAV was 10 times more resistant than dispersed HAV.

Cysts and Parasites Protozoal cysts are considerably more resistant than are enteric bacteria and significantly more resistant than enteric viruses, probably because of the cyst’s physiologically inactive outer

Chapter 61: Field Water Disinfection shell, which the disinfectant must penetrate to be effective.40,244 Early data exist for E. histolytica, but recent work on G. lamblia indicates similar sensitivity to both iodine and chlorine.105 Higher pH and lower temperature decrease the effectiveness of halogens on Giardia.91,101,210 Review literature frequently attributes exaggerated resistance of Giardia to halogens.95 Jarrol and colleagues103,104 tested two chlorine methods and four iodine methods for effectiveness against Giardia cysts. They found all methods effective in warm water, but only two methods destroyed all cysts in cold water in recommended doses. Higher doses or longer contact times would make all these methods effective. Halogens can be used in the field to inactivate Giardia cysts (see Figure 61-3). However, longer contact time is required in cold and dirty water.80 Cryptosporidium oocysts differ greatly from other protozoan cysts and are highly resistant to halogens. The Ct constant for Cryptosporidium in warm water with chlorine has been estimated to be 9600.33 Other data demonstrated 90% inactivation with 80 ppm of chlorine after 90 minutes, 14 times more resistant that Giardia cysts.113 The current recommendation for decontaminating chlorinated swimming pools is to raise the free available chlorine concentration to 20 mg/L for 9 hours (Ct 10,800).27 From 65% to 80% of Cryptosporidium oocysts were inactivated after 4 hours by two iodine tablets in “general case” water.80 This implies that 3-log inactivation could have been achieved after 3 to 4 more hours. Although halogens can achieve disinfection of Cryptosporidium in the field, this is not practical.56,190,201,244 The resistance of Cyclospora and microsporidia is not well studied, but the oocysts are similar to Cryptosporidium and thus may resemble this protozoa more than Giardia. Both Cryptosporidium and Giardia are susceptible to chlorine dioxide.46,113 Schistosome cercariae are susceptible to low concentrations of chlorine.245 Limited data on parasitic helminth larvae and ova indicate such high levels of resistance that chemical disinfection is not useful.115,146,203 However, these are not common waterborne pathogens and can be readily removed or destroyed by heat, filtration, or coagulation-flocculation.

Disinfection Constant The best comparison of disinfection power is the disinfection constant (Ct). Disparate results may be caused by lack of standardized experimental conditions of pH, temperature, chemical species of halogen, and species of microorganism or by different techniques for concentrating, counting, and determining viability of organisms.96,146 The latter is especially a problem for cysts and viruses, which cannot be cultured easily.198 The end point for disinfection effectiveness is now becoming standardized by the EPA guidelines, but most older studies used 99.9% for all organisms, with some using 99% or 99.99%. Differences between laboratory and field conditions also make extrapolation from data to practice inaccurate and suggest the need for a safety factor in the field. Despite variation, Ct remains a useful and widely used concept; values provide a basis for comparing the effectiveness of different disinfectants for inactivation of specific microorganisms.96 To use halogens for disinfection, a consensus organism (the most resistant target) determines the Ct.96,118,244 For wilderness water, this has been protozoan cysts. The resistance of Cryptosporidium will not raise the threshold for halogen use; rather, it will force an alternative or a combination of methods to ensure removal and inactivation of all pathogens.

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CHLORINE Chlorine has been used as a disinfectant for 200 years. Hypochlorite was first used for water disinfection in 1854 during cholera epidemics in London and was first used continuously for water treatment in Belgium in 1902. It is currently the preferred means of municipal water disinfection worldwide and the preference of the Centers for Disease Control and Prevention (CDC) and WHO for individual household disinfection of drinking water, so extensive data support its use244 (see Table 61-10).

Chemistry Chlorine reacts in water to form the following compounds62,244: Cl2 + H2O → HOCl + H+ + Cl− HOCL → OCl− + H+ At neutral pH, negligible amounts of diatomic chlorine are present. The major disinfectant is hypochlorous acid (HOCl), which penetrates cell and cyst walls easily. Dissociation of HOCl to the much weaker disinfectant hypochlorite (OCl−) depends on temperature and pH. In pure water at pH 6.0, 97% of chlorine is HOCl; at pH 7.5, the HOCl/OCl− ratio is 1 : 1; and above pH 7.5, OCl− predominates.244 The combination of these two compounds is defined as free available chlorine. Both calcium hypochlorite (Ca[OCl]2) and sodium hypochlorite (NaOCl) readily dissociate in water, allowing the same equilibrium to form as when elemental chlorine is used.118,244 Chloride ion (Cl−, NaCl, or CaCl2) is germicidally inactive. In addition, chlorine readily reacts with ammonia to form monochloramines (NH2Cl), dichloramines, or trichloramines, referred to as combined chlorine. In field disinfection, these compounds are not considered, and only free residual chlorine should be measured. However, chloramines have weak disinfecting power and are calculated as a disinfectant in municipal sewage plants.96,144,146,244 At doses of a few mg/L and contact times of about 30 minutes, free chlorine generally inactivates >99.99% of enteric bacteria and viruses.212

Toxicity Acute toxicity to chlorine is limited; the main danger is irritation and corrosion of mucous membranes if concentrated solutions (e.g., household bleach) are ingested. Numerous cases have been reported of short-term ingestion of very high residuals (50 to 90 ppm) in drinking water; one military study used 32 ppm for several months without adverse effects.244 Animal studies using long-term chlorination of drinking water at 100 to 200 ppm have not shown toxic effects.146 Sodium hypochlorite is not carcinogenic; however, reactions of chlorine with certain organic contaminants yield chlorinated hydrocarbons, chloroform, and other trihalomethanes, which are considered carcinogenic.146,230 Public health regulations limit residual chlorine in public systems to decrease ingestion of trihalomethane. The concern is now fueled more by public fears than by scientific conclusion.244 The risk of death from infectious diseases if disinfection is not used is far greater than any risk from chlorine disinfection byproducts.184,230 These compounds are not likely to form in clean wilderness surface water, because the organic precursors are not present.

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TABLE 61-12. Water Disinfection Techniques and Halogen Doses ADD TO 1 L OR QUART OF WATER AMOUNT FOR 4 ppm

IODINATION TECHNIQUES Iodine tabs Tetraglycine hydroperiodide EDWGT Potable Aqua Globaline 2% Iodine solution (tincture)* 10% Povidone-iodine solution*† Saturated solution: iodine crystals in water Saturated solution: iodine crystals in alcohol CHLORINATION TECHNIQUES Sodium hypochlorite (household bleach 5%)† Calcium hypochlorite (Redi Chlor [1/10 gm tab]) Sodium dichloroisocyanurate (AquaClear) Chlorine plus flocculating agent (Chlor-Floc)

AMOUNT FOR 8 ppm

1

1 tab

0.2 mL or 5 gtts 0.35 mL or 8 gtts 13 mL 0.1 mL

0.4 mL or 10 gtts 0.70 mL or 16 gtts 26 mL 0.2 mL

AMOUNT FOR 5 ppm

AMOUNT FOR 10 ppm

/2 tab

0.1 mL or 2 gtts

0.2 mL or 4 gtts 1 /4 tab/2 quarts 1 tab (8.5 mg NaDCC) 1 tab

EDWGT, emergency drinking water germicidal tablet; gtts, drops. *Measure with dropper (1drop = 0.05 mL) or tuberculin syringe. † Povidone-iodine solutions release free iodine in levels adequate for disinfection, but scant data are available.

with high heat and humidity. To extend shelf-life, many tablets are individually wrapped in foil.

TABLE 61-13. Recommendations for Contact Time with Halogenations in the Field CONTACT TIME IN MINUTES AT VARIOUS WATER TEMPERATURES CONCENTRATION OF HALOGEN 2 ppm 4 ppm 8 ppm

5° C (41° F)

15° C (59° F)

30° C (86° F)

240 180 60

180 60 30

60 45 15

Note: Data indicate that very cold water requires prolonged contact time with iodine or chlorine to kill Giardia cysts. These contact times have been extended from the usual recommendations in cold water to account for this and for the uncertainty of residual concentration.

Products and Techniques for Chlorination Free chlorine is the most widely available and affordable means of chemical water disinfectant.212 For household or field water treatment, free chlorine can be obtained in liquid, granular, and tablet forms or generated from electrolysis of salt (Tables 61-12 and 61-13 and Appendix B). Tablets have the advantage of easy administration and can be salvaged if the container breaks. However, they lose effectiveness with exposure to heat, air, or moisture. Although no significant loss of potency results from opening a glass bottle intermittently over weeks, activity is rapidly lost after a few days of continuous exposure to air

Superchlorination-Dechlorination The process of superchlorination-dechlorination with different reagents is used in some large-scale disinfection plants to avoid long contact times and to remove tastes and smells. High doses of chlorine remove or oxidize hydrogen sulfide and some other chemical contaminants that contribute to poor taste and odor. Chlorine bleaches organic matter, making water sparkling blue, as in swimming pools.244 This method of chlorination can be readily adapted to field use. High doses of chlorine are added to the water in the form of calcium hypochlorite crystals to achieve concentrations of 30 to 200 ppm of free chlorine. These extremely high levels are above the margin of safety for field conditions and rapidly kill all bacteria, viruses, and protozoa and could kill Cryptosporidium with overnight contact times. After at least 10 to 15 minutes, several drops of 30% hydrogen peroxide solution are added. This reduces hypochlorite to chloride, forming calcium chloride (a common food additive), which remains in solution, as follows: Ca(OCl)2 + 2H2O → 2HOCl + Ca++(OH−)2 Ca(OCl)2 + 2H2O2 → CaCl2 + 2H2O + 2O2 Excess hydrogen peroxide reacts with water to form oxygen and water. Chloride has no taste or smell. Hydrogen peroxide is also a weak disinfectant,253 although not in common use. The minor disadvantage of a two-step process is offset by excellent taste. Measurements to titrate peroxide to the esti-

Chapter 61: Field Water Disinfection mated amount of chlorine do not need to be exact, but some experience is needed to balance the two and achieve optimal results. This is a good technique for highly polluted or cloudy water and for disinfecting large quantities. It is the best technique for storing water on boats or for emergency use. A high level of chlorine prevents growth of algae or bacteria during storage; water is then dechlorinated in needed quantities when ready to use. The two reagents must be kept tightly sealed to maintain potency of the reagents. Properly stored, calcium hypochlorite loses only 3% to 5% of available chlorine per year. Thirtypercent hydrogen peroxide is corrosive and burns skin, so it should be used cautiously. A commercial formulation, The Sanitizer, is no longer available; however, the ingredients can be easily obtained and packaged in small Nalgene bottles.


IODINE Iodine has been used as a topical and water disinfectant since the beginning of the 20th century.118 Iodine is effective in low concentrations for killing bacteria, viruses, and cysts, and in higher concentration against fungi and even bacterial spores, but it is a poor algicide42,84,146 (see Table 61-11 and Figure 61-3). Iodine has been used successfully in low concentrations for continuous water disinfection of small communities.112 Despite several advantages over chlorine disinfection, it has not gained general acceptance because of concern for its physiologic activity.

Chemistry Iodine is the only halogen that is a solid at room temperature. Of the halogens, it has the highest atomic weight, lowest oxidation potential, and lowest water solubility. Its disinfectant activity in water is quite complex because of formation of various chemical intermediates with variable germicidal efficiencies. Seven different ions or molecules are present in pure aqueous iodine solutions, but only elemental (diatomic) iodine (I2) and hypoiodous acid (HOI) play major roles as germicides. Diatomic iodine reacts in water to form the following compounds42,84: I2 + H2O → HOI + I− + H+ I2 is two to three times as cysticidal and six times as sporicidal as HOI, because it more easily diffuses through the cyst wall. Conversely, HOI is 40 times as virucidal and three to four times as bactericidal as I2, in that inactivation of organisms depends directly on oxidation potential, without involving cell wall diffusion.40 Their relative concentrations are determined by pH and concentration of iodine in solution.42 At pH 7.0 and 0.5 ppm of iodine, the concentrations of I2 and HOI are approximately equal, resulting in a broad spectrum of germicidal action. At pH 5.0 to 6.0, most of the iodine is present as I2, whereas at pH 8.0, 12% is present as I2 and 88% as HOI. At higher concentrations of iodine, more HOI is present. Under field conditions, I2 is the major disinfectant for which doses are calculated.42 Other chemical species, including triiodide (I3−), iodate (HIO3), and iodide (I−), form under certain conditions but play no role in water disinfection.42,55 Iodide is important because it

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readily forms when reducing substances are added to iodine solution. Iodide ion is without any effect for water disinfection and it has no taste or color, but it is still physiologically active.

Toxicity The main disadvantage of iodine is its physiologic activity, with effects on thyroid function, potential toxicity, and allergenicity.159 Acute toxic responses generally result from intentional overdoses of iodine, with corrosive effects in the gastrointestinal tract leading to hemorrhagic gastritis. Mean lethal dose is probably about 2 to 4 g of free iodine or 1 to 2 ounces of strong tincture.71 Toxicity is limited by rapid conversion of iodine to iodide by food (especially starch) in the stomach and early reflex vomiting. Iodide is absorbed into the bloodstream but has minimal toxicity (it is used widely for radiographic imaging). Sensitivity reactions, including rashes and acne, may occur with usual supplementation levels of iodine. Given the physiologic necessity of iodine, it is not clear why some people react to certain forms of the substance, such as iodized salt. As with other sensitivity reactions, these may occur with very low doses. Acute allergy to iodide is rare and manifests as individual hypersensitivity, such as angioneurotic and laryngeal edema.159 Chronic iodide poisoning, or iodism, occurs after prolonged ingestion of sufficiently high doses, but marked individual variation is seen. Symptoms simulate upper respiratory illness, with irritation of mucous membranes, mucus production, and cough. Iodine is an essential element for normal thyroid function and health in small amounts of 100 to 300 µg/day, but excess amounts can result in thyroid dysfunction. Maximum safe level and duration of iodine ingestion are not clearly defined, making it difficult to provide recommendations for prolonged use in water treatment.

Thyroid Effects of Excess Iodine Ingestion Most persons can tolerate high doses of iodine without development of thyroid abnormalities,24 because the thyroid gland has an autoregulatory mechanism that effectively manages excessive iodine intake. Initially, excess iodine suppresses production of thyroid hormone, but production usually returns to normal in a few days. Iodine-induced hyperthyroidism can result from iodine ingestion by persons with underlying thyroid disease or when iodine is given to persons with prior iodine deficiency.24,195 During the worldwide campaign to eliminate endemic goiter and cretinism, 1% to 2% of residents developed hyperthyroidism from small amounts of dietary iodine supplementation. Groups at higher risk were elderly persons, Graves’ disease patients (especially after antithyroid therapy), and patients taking pharmacologic sources of iodine. Hyperthyroidism has been reported from iodine use as a water disinfectant in two travelers. Both were from iodine-sufficient areas and had antithyroid antibodies, suggesting underlying thyroiditis; one had a mother and sister with Hashimoto’s thyroiditis.123 Iodine-induced hypothyroidism or goiter is much more common from excessive iodine intake. Hypothyroidism is attributed to prolonged suppression of thyroid hormone production induced by excess iodine levels, but the mechanism through which iodide goiter is produced is not well understood. The incidence of goiter varies and does not correlate well with quantity of iodine or with the level of hypothyroidism. Goiters

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were discovered among a group of Peace Corps volunteers in Africa and were linked epidemiologically to the use of iodine resin water filters.102 Forty-four (46%) of the volunteers had enlarged thyroids, but 30 of these had normal thyroid function tests. Iodine-induced hypothyroidism or goiter may occur with or without underlying thyroid disease but is more common in several groups24,195,246: (1) those with underlying thyroid problems, including prior treatment for Graves’ disease or subtotal thyroidectomy; (2) fetuses and infants, from placental transfer of iodide from mothers treated with iodides; (3) persons with subclinical hypothyroidism, especially elderly persons, in whom the incidence is 5% to 10%; and (4) patients with excessive iodide from medications (formerly potassium iodide; currently amiodarone). Neonatal goiter is especially worrisome because it can lead to asphyxia during birth or hypothyroidism with mental impairment. Daily intakes as small as 12 mg have been reported to produce congenital iodide goiters, but generally much higher doses are required.

Dose-Response or Threshold Level It is unclear what percent of the population will respond adversely to excess iodine or what should be defined as excess intake. The reported incidences of goiter, hypothyroid effects, and hyperthyroid response vary so widely that they provide no clear dose limits.159 These data and other controlled trials of high doses were reviewed by Backer. The use of iodine for decades in the military and civilian population without reports of associated clinical thyroid problems suggests that the risks are minimal and would be outweighed by the risk of enteric disease. However, biochemical assays showed that changes in thyroid function tests were common with excess iodine intake, but usually remained within the range of normal values. Even when outside the normal range, the changes in thyroid function remained subclinical. All changes reverted to normal within weeks to months without persistent thyroid disease. Studying longer duration of ingestion, Freund75 found minimal changes and no clinical problems when water with 1 mg/L of iodine was used to disinfect water at a prison for up to 3 years. Referring to the same project, Thomas and colleagues222 reported that after 15 years of ongoing iodine use at 1 mg/L, iodinated water caused no decrease in serum concentrations of T4 below normal values and no allergic reactions. Patients with prior thyroid disease had no recurrence with iodinated water; four patients with active hyperthyroidism were treated in standard fashion, and their condition remained well controlled despite the extra iodine intake. Also, 177 inmates gave birth to 181 full-term infants, and no neonatal goiters were detected.200 The military studied long-term toxic effects of iodine, adding sodium iodide to drinking water at a naval base for 6 months.143 The estimated daily dose of iodine per person was 12 mg for the first 16 weeks and 19.2 mg for the next 10 weeks. No evidence of functional changes or damage in the thyroid gland, cardiovascular system, bone marrow, eyes, or kidneys was noted. No increase in skin diseases, no sensitization to iodine, and no impaired wound healing or resolution of infections was evident. If subclinical thyroid disease or enlarged thyroid were noted with a history of excess iodine ingestion, most experts would first stop the iodine intake and follow thyroid function before treating hypothyroidism.

Recommendations The tenth edition of the recommended dietary allowances (RDAs, 1989) set the allowable dose to 1 mg/day for children and up to 2 mg/day for adults (increased from 0.5 to 1.0 mg in the ninth edition, 1980), primarily based on the data from Freund and Thomas.159 Possible toxicity with intermediate- to long-term use of iodine and the question of iodide toxicity remain controversial. The EPA and the WHO, supported by the American Water Works Association (AWWA), have recommended iodine use for water disinfection only as an emergency measure for short periods of about 3 weeks.242,256 However, this period of short use appears arbitrary. Available data suggest the following: 1. High levels of iodine, such as those produced by recommended doses of iodine tablets, should be limited to periods of 1 month or less. 2. Iodine treatment that produces a low residual (1 mg/L or less) appears safe, even for long periods in people with normal thyroid function. This would require very low doses of iodine added to the water or an activated charcoal stage to remove residual iodine. 3. Persons planning to use iodine for a prolonged period should have the thyroid gland examined and thyroid function measured to ensure that a state of euthyroidism exists. The following groups should not use iodine for water treatment because of their increased susceptibility to thyroid problems: • Pregnant women • Persons with known hypersensitivity to iodine • Persons with a history of thyroid disease, even if controlled by medication • Persons with a strong family history of thyroid disease (thyroiditis) • Persons from areas with chronic dietary iodine deficiency

Products and Techniques for Iodination Formulations Several forms of iodine are available for field use (See Tables 61-12 to 61-15 for efficacy data and Appendix B for details on commercial products, including tablets and crystalline iodine).

Iodine Solutions Iodine solutions commercially sold as topical disinfectants are inexpensive and can be measured accurately with a dropper but are staining and corrosive if spilled. These contain iodine, potassium or sodium iodide in water, ethyl alcohol, or glycerol (Table 61-14). Iodide improves stability and solubility but has no ger-

TABLE 61-14. Iodine Solutions PREPARATION Iodine topical solution Lugol’s solution Iodine tincture Strong iodine solution

IODINE (%)

IODIDE (%)

TYPE OF SOLUTION

2.0

2.4 (sodium)

Aqueous

5.0 2.0 7.0

10.0 (potassium) 2.4 (sodium) 9.0 (potassium)

Aqueous Aqueous-ethanol Ethanol (85%)

Chapter 61: Field Water Disinfection micidal activity and adds to the total amount of iodine ingested and absorbed into the body. “Decolorized” iodine solution contains only iodide and should not be used for water disinfection. Iodophors are solutions in which diatomic iodine is bound to a neutral polymer of high molecular weight, giving the iodine greater solubility and stability with less toxicity and corrosive effect.42,84 Povidone-iodine is a 1-vinyl-2-pyrrolidinone polymer with 9% to 12% available iodine. The iodophors are routinely used for topical disinfection, because they have less tissue toxicity than iodine solutions. Although they are not approved for water disinfection in the United States, they are used in other countries for this purpose.10 According to the manufacturer, approval for this use in the United States was not pursued because the anticipated use did not justify the expense. Povidone is nontoxic and was used as a blood expander during World War II. In aqueous solution, povidone-iodine provides a sustainedrelease reservoir of halogen; free iodine is released in water solution depending on the concentration (normally, 2 to 10 ppm is present in solution). In dilutions below 0.01%, povidone-iodine solution can be regarded as a simple aqueous solution of iodine.84 One report found these compounds similar in germicidal efficiency to other iodine-iodide solutions.42 Data indicate persistence of about 2 ppm of free iodine at a 1 : 10,000 dilution,84 equivalent to 0.1 mL (2 drops) added to 1 L of water. Conflicting values for available iodine and free iodine in dilute solutions result from the complex chemistry of povidoneiodine.14,97 Personal and anecdotal experience of others attest to its effectiveness in field use.10

Resins Iodine resins have been widely used for water disinfection in individual or small systems and incorporated into many different filter designs available for field use. They provide advantages over chlorination systems by eliminating the need for chemical feed systems, residual monitoring, and contact time.242 Iodine resins are considered demand disinfectants because they are minimally insoluble in water and little iodine is released into aqueous solution. However, when a microorganism comes into contact with the resin, iodine apparently transfers to the microorganism aided by electrostatic forces, binds to the wall or capsule, and penetrates and kills the organism.130 Iodine resins are engineered to produce low residuals in effluent water. Pentaiodide resin produces a constant 1 to 2 ppm concentration after initial use, whereas triiodide resin produces a residual iodine concentration of less than 0.20 ppm at equilibrium.130 The concentration in the effluent of triiodide resin is temperature dependent. Concentrations less than 1.0 ppm were obtained with water at 42.2° C (108° F), but this increased to a total iodine content of 6 to 10 ppm at 71° C (160° F). After returning to room temperature, the iodine residual returned to nominal values.130 Measurable iodine is attached to bacteria and cysts after resin treatment, effectively exposing the organisms to high iodine concentrations. This allows reduced contact time compared with dilute iodine solutions.70,130 Some contact time still appears necessary.129 Fifty percent of Giardia cysts were viable 10 minutes after passage through a triiodine resin. Viable Giardia cysts could be recovered in 4° C (39.2° F) water 40 minutes after passage through an iodine resin.129 A simple resin filter failed to pass the EPA protocol for “worst-case” water unless water was passed through the filter twice. The data implied that a holding

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(contact) time could have achieved the same results.81 The Canadian Health Department, challenging an in-line triiodine resin with highly polluted water, also found that a 15-minute contact time was necessary for warm water and 30-minute contact time for cold water.3,64 The EPA conducted tests of triiodide resin against E. coli but not against other organisms, for which it relied on independent testing. It concluded that the product depends on a 0.2 ppm residual and that additional testing would be necessary below this level. Resins are chemically and physically stable during conditions of dry storage at room temperature. Aqueous suspensions or resins retain biocidal potential for 15 years. No alteration in activity was observed after dry storage for 1 month at 50° C (122° F).130 Resins have proved effective against bacteria, viruses, and cysts but not against Cryptosporidium parvum oocysts or bacterial spores.130 When Cryptosporidium oocysts were passed through a triiodide resin column, most were retained in the resin column, probably by electrostatic attraction to the resin. Of those that passed through, only a small percentage were inactivated within 30 minutes by the iodine.232 Despite the controversy regarding contact time, most of the testing done with iodine resins has shown high levels of effectiveness.

Iodine Resin Filters. Recently, several iodine resin products were withdrawn from the market when company testing showed that they failed to meet viral inactivation standards of 4-log reduction. The units had previously obtained EPA registration on the basis of successful testing contracted through a laboratory that does the majority of testing for the filter industry. It was not clear whether failure was related to inadequate contact with the resin or contact time with the iodine residual. Most designs incorporated two stages in addition to the iodine resin. A microfilter, generally 1 micron (µm), effectively removes Cryptosporidium, Giardia, and other halogen-resistant parasitic eggs or larva. Because iodine resins kill bacteria and viruses rapidly, no significant contact time is required for most water.81 The addition of a third stage of activated charcoal removes dissolved residual; however, the importance of iodine residual for disinfection has not been determined.129,226 In conclusion, iodine resins are effective disinfectants that can be engineered into attractive field products, including use in the space shuttle and large-scale units for international disasters. They may prove useful for small communities in undeveloped and rural areas where chlorine disinfection is technically and economically unfeasible. However, companies recently have abandoned iodine resin–containing portable hand-pump filters. Only one drink-through bottle remains on the U.S. market. Other products may still be available outside the United States.


CHLORINE VS. IODINE A large body of data proves that both iodine and chlorine are effective disinfectants with adequate concentrations and contact times (cold temperatures equate with slow disinfection time for both). Comparing effectiveness of chlorine and iodine is difficult because of the different ionic species and compounds that may exist under varying conditions.94 Chlorine and iodine tablets have been directly compared under identical water test conditions and found to be similar in their biocidal activity in

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PART EIGHT: FOOD AND WATER

TABLE 61-15. Data on Microcidal Efficacy of Iodine Tablets HALOGEN Chlor-Floc

Globaline

AquaPure

Globaline Iodine tabs

DOSE

FRC (mg/L)

TIME (min)

TEMPERATURE ° C (° F)

1 tab or 2 tabs 1 1 1 tab 2 tabs 2 2 2 2 tabs 1 tab 2 2 2 2 tabs 1 2 1 or 2 1 2

4–7 4–14 4 5 5 12 17 14 12 7–11

5 20 5 20 12 20 45 20 60 40 30–40 20 20 20 60 180 120 60 60 60

10–20 (50–68) 10–20 (50–68) 10–20 (50–68) 10–20 (50–68) 25 (77) Various 5 (41) 5 (41) 5 (41) 5 (41) 15–25 (59–77) 15–25 (59–77) 15–25 (59–77) 15–25 (59–77) 15 (59) 5 (41) 5 (41) 5–25 (41–77) 5 (41) 5 (41)

10 8–16 8 16

ORGANISM

LOG REDUCTION

Bacteria Giardia muris Rotavirus Poliovirus Poliovirus Bacteria G. muris Rotavirus Poliovirus

6 3 4 2.5 2 6 3 4 3

Bacteria Rotavirus Polio virus G. muris Giardia Giardia Giardia Hepatitis A Polio, echo Polio, echo

6 4 2 2 3 3 3 4 3 4

REFERENCE Powers, 1994283

Powers, 1992280

Powers, 1991279 Sobsey, 1991213

FRC, free residual chlorine.

most conditions using recommended dose and contact time165 (see Tables 61-12, 61-13, and 61-15.) Contact times in Table 61-13 are extended from the previous recommendations for treatment in cold water to provide a margin of safety and to ensure high levels of cyst destruction. A few investigators have reported data suggesting ineffectiveness of common halogen preparations. Jarroll and colleagues104,105 tested six methods of field disinfection and found that none achieved high levels of Giardia inactivation at the recommended dose and times. However, this failure simply reflected the need for longer contact times in cold water.124 Ongerth and colleagues156 tested seven chemical treatments for Giardia inactivation in clear and turbid water at 10° C (50° F). None achieved 99.9% reduction in 30 minutes. All iodine-based chemical methods were effective at 8 hours, but none of the chlorine preparations was effective, even after this extended time. Although these results after 30 minutes in cold water are to be expected, the 8-hour results do not conform with other experimental data on chlorine. Unfortunately, the authors did not test for residual halogen, although initial levels achieved should have been effective, and they did not test at regular time intervals to determine when the iodine methods had achieved the target reduction of organisms. Schlosser found that sodium hypochlorite tablets, sodium dichloroisocyanurate tablets, and iodine in ethanol used according to package instructions removed 2 to 3 log of bacteria in clear water, but less in turbid river water.200 Again, this suggests the need for clarifying dirty water before halogen use and, if possible, providing extra contact time in any situation. Iodine has several advantages over chlorine. Of the halogens, iodine has the lowest oxidation potential, reacts least readily with organic compounds, is least soluble, is least hydrolyzed by water, and is less affected by pH, all of which indicate that low iodine residuals should be more stable and persistent than corresponding concentrations of chlorine.55,84,112,146

Taste Objectionable taste and smell are the major problems with acceptance of halogens. Most objectionable tastes in treated water are derived from dissolved minerals, such as sulfur, and from chlorine compounds, chloramines, and organic nitrogen compounds, even at extremely low levels. People are familiar with the taste of chlorine compounds; tap water usually contains 0.2 to 0.5 ppm of chlorine, swimming pools 1.5 to 3 ppm, and hot tubs 3 to 5 ppm. Most persons note a distinct taste at 5 ppm and a strong, unpleasant taste at 10 to 15 ppm.188 Hypochlorous acid and chloride have no taste or odor.244 Elemental iodine at 1 mg/L is undetectable. Most persons can detect iodine solutions at 1.5 to 2 mg/L but do not find it objectionable.18,55,76 Eight ppm of iodine produces a distinct taste and odor; however, tablets yielding these concentrations were preferred by military personnel over tincture of iodine in equivalent doses.42,145 Iodide ion has no color or taste. Taste tolerance or preference for iodine over chlorine is individual. Opposite preferences have been documented when direct comparisons are done.154,169 Informal taste tests suggest that most persons prefer the taste of iodine to chlorine at concentrations typically used in the field. In addition, iodine forms fewer organic compounds that produce highly objectionable taste and smell. Taste can be improved by several means (Box 61-10).

Minimal Dosage The relationship between halogen concentration and time allows use of the minimum necessary dose, with a longer contact time (see Table 61-13).

Chapter 61: Field Water Disinfection

Box 61-10. Improving the Taste of Halogens • Decreased dose; increased contact time • Clarification of cloudy water, which decreases amount of halogen needed • Removal of halogen • Use of granular activated carbon (GAC) • Chemical reduction • Ascorbic acid • Sodium thiosulfate • Superchlorination-dechlorination • Use of KDF (zinc-copper) brush or media • Alternative techniques: • Heat • Filtration • Chlorine dioxide or mixed species (Miox)

Theoretically, doubling the contact time allows a 50% reduction of halogen dose at any level. Although this relationship holds true at the higher field doses of halogens, as the levels drop, the reaction departs from mathematical models, and the straight-line graph has a “tail” (see Figure 61-2). This departure from strict first-order kinetics and the uncertainty of halogen demand in field disinfection mean that a margin of safety must be incorporated into contact times at lower doses. Of all standard iodine doses, iodine tablets yield the highest dose (8 mg/L with an intended contact time of 10 minutes in warm water). The tablets cannot be broken in half but can be added to 2 quarts instead of 1 quart to yield concentrations consistent with the other preparations. In recommended doses, the liquid preparations of iodine yield 4 mg/L. Because even clear surface water has some halogen demand, this dose of 4 mg/L should generally not be reduced. The exception would be for backing up tap water in developing countries, when the dose may routinely be cut in half for an added dose of 2 ppm with a few hours of contact time. Giardia cysts and viruses can be killed with doses of chlorine or iodine of 2 ppm or less (see Figure 61-3).73,92,118 For chlorination methods that add 5 mg/L, adding half the amount to clean surface water should be adequate if the contact time is tripled. Even less could be used for tap water. None of these concentrations will destroy Cryptosporidium oocysts. Temperature and organic matter in the water may be manipulated. Increasing the temperature of the water, especially when initially near 5° C (41° F), decreases the Ct constant (see Table 61-13 and Figure 61-3). Filtering water before adding halogen improves the reliability of a given halogen dose by decreasing halogen demand, allowing a lower dose of halogen.146 Sedimentation or coagulation-flocculation cleans cloudy water and lowers the required halogen dosage considerably, in addition to removing many of the contaminants that contribute to objectionable taste.

Dehalogenation Halogen can be removed from water after the required contact time. Activated charcoal removes iodine or chlorine, allowing standard or even high doses to be used without residual taste. The relative instability of chlorine in dilute solutions can be used to decrease taste over time. Chlorine residual in an open

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container decreases 1 mg/L in the first hour, then 0.2 mg/L in the next 5 to 8 hours, for a total of 2 to 2.5 mg/L in 24 hours. Ultraviolet light also depletes free chlorine.244

Alteration of Chemical Species (Reduction) Several chemical means are available to reduce free iodine or chlorine to iodide or chloride that have no color, smell, or taste. These “ides” have no disinfection action, so the techniques should be used only after the required contact time. In superchlorination-dechlorination, hydrogen peroxide “dechlorinates” the water by forming calcium chloride. This reaction with hydrogen peroxide works best when calcium hypochlorite is used as a disinfectant. If bleach (sodium hypochlorite) is used, hydrogen peroxide reacts with chlorine in water to form hydrochloric acid in harmless amounts. Two other chemicals that may be safely used with any form of chlorine or iodine are ascorbic acid (vitamin C) and sodium thiosulfate. Ascorbic acid is widely available in the crystalline or powder form. Grinding up tablets that have binders may cloud the water. Ascorbic acid is a common ingredient of flavored drink mixes, which accounts for their effectiveness in covering up the taste of halogens.154,188 Sodium thiosulfate similarly “neutralizes” iodine and chlorine. A few granules in 1 quart of iodinated water decolorizes and removes the taste of iodine by converting it to iodide. In reaction with chlorine, it forms hydrochloric acid, which is not harmful or detectable in such dilute concentration. Thiosulfate salts are inert in vivo and poorly absorbed from the gastrointestinal tract. Sodium thiosulfate is available at chemical supply stores. Zinc-copper alloys act as catalysts to reduce free iodine and chlorine through an electrochemical reaction (see Copper and Zinc). They also remove or reduce dissolved metals like iron, as well as heavy metals such as lead, selenium, and mercury. One product that is no longer on the market incorporated such an alloy into the bristles of a small brush to be stirred in the water after halogen disinfection. It was effective but slow, which limited its use to small volumes of water: stirring for 1 minute removed 10 mg/L of chlorine from 250 mL of water.


MISCELLANEOUS DISINFECTANTS

Mixed Species Disinfection (Electrolysis) Passing a current through a simple brine salt solution generates free available chlorine, as well as other “mixed species” disinfectants that have been demonstrated effective against bacteria, viruses, and bacterial spores.197 The process is well described and can be used on both large and small scale. It is practical and economical enough to be useful in developing areas of the world. The exact composition of the solution is not well delineated because many of the compounds are relatively unstable. However, the resulting solution has greater disinfectant ability than a simple solution of sodium hypochlorite. It has even been demonstrated to inactivate Cryptosporidium, suggesting that chlorine dioxide is among the chemicals generated.239 A new point-of-use commercial product is now available (Miox, marketed by MSR; see Appendices for more information).

Ozone Ozone and chlorine dioxide are highly effective disinfectants widely used in municipal water treatment plants.244 These are

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PART EIGHT: FOOD AND WATER

the only disinfectants that have been demonstrated effective against Cryptosporidium in typical concentrations.46,113,158 Ozone is an unstable form of oxygen, with the chemical formula O3. In solution, it decays to O2, producing free hydroxyl radicals. Both ozone and the hydroxyl radicals are two of the most powerful oxidants used in water treatment.16 Ozone is a colorless gas manufactured by passing air or oxygen through a high-voltage current discharge. The resulting ozonerich gas is then dissolved in water. Clearly, this is not conducive to small, point-of-use generation, so consumers should have a healthy skepticism of techniques claiming to rely on ozone.

Chlorine Dioxide Chlorine dioxide (CIO2) has been used primarily as a bleaching agent to control taste and odor in municipal disinfection, but it has gained wider use for disinfection of both community and point-of-use drinking water supplies in developed countries. Chlorine dioxide is capable of inactivating most water-borne pathogens, including Cryptosporidium parvum oocysts, at practical doses and contact times. It is at least as effective a bactericide as chlorine, and in many cases it is superior. It is far superior as a virucide.244 For point-of-use treatment of water, chlorine dioxide is produced on site from the reaction of sodium chlorite with acid.16,209 For example: 5NaClO2 + 4HCl → 4ClO2 + 5NaCl + 2H2O Chlorine dioxide is not as unstable as ozone, but it does not produce a lasting residual. Byproducts of chlorine dioxide are chlorite (ClO2−) and chlorate (ClO3−). Chlorine dioxide, a potent biocide, has been used for many years to disinfect municipal water and in numerous other large-scale applications. It does not form chlorinated compounds in the presence of organics and is efficacious over a wide pH range. However, chlorine dioxide is a volatile gas that must be produced on-site and, until recently, the only practical method for its production required sophisticated chemical generation equipment. Therefore, significant capital and operating costs limited the benefits of chlorine dioxide to only largescale applications. However, recently, new technology enables cost-effective and portable chlorine dioxide generation and distribution for use in an ever widening array of small-scale applications (Box 61-11), including MicroPur MP-1, AquaMira, and Miox (see Appendices).

Silver Silver ion has bactericidal effects in low doses. The literature on antimicrobial effects of silver is confusing and contradictory.98,146,244,248 Concentrations in water less than 100 parts per billion (ppb) are effective against enteric bacteria. The reaction follows first-order kinetics and is temperature dependent. Calcium, phosphates, and sulfides interfere significantly with silver disinfection. Organic chemicals, amines, and particulate or colloidal matter may also interfere, but no more than with chlorine. Silver is physiologically active. Acute toxicity does not occur from small doses used in disinfection, but argyria, which is permanent discoloration of the skin and mucous membranes, may result from prolonged use. For this reason, a maximum limit of 50 ppb of silver ion in potable water is recommended. At this concentration, disinfection requires several hours.

Box 61-11. Chlorine Dioxide Advantages Effective against all microorganisms, including Cryptosporidium Low doses have no taste or color Portable device now available for individual and small group field use and is simple to use More potent than equivalent doses of chlorine Less affected by nitrogenous wastes

Disadvantages Volatile, so do not expose tablets to air and use generated solutions rapidly No persistent residual, so does not prevent recontamination during storage Sensitive to sunlight; keep bottle shaded or in pack during treatment

Relative susceptibility of microorganisms to chlorine dioxide: bacteria > viruses > protozoa. Experimental results indicate 18% survival of E. coli at 3 hours at 40 µg/L. Salmonella typhi was reduced more than 5 log at 50 µg/L with a 1-hour exposure; poliovirus was not reduced at 50 µg/L with a 1-hour exposure.11 Water disinfection systems using silver have been devised for spacecraft, swimming pools, and other settings.244 The advantage is absence of taste, odor, and color. Persistence of residual silver concentration allows reliable storage of disinfected water. Silver can be supplied through a silver nitrate solution, desorption from silver-coated materials, or electrolysis. When coated on surfaces, silver acts as a constant-release disinfectant that produces aqueous silver ion concentrations of 0.006 to 0.5 ppm, which are sufficient to disinfect drinking water.130 Because of this attractive feature, silver-based devices are being designed and tested in developing countries. In Pakistan, a nylon bag with silver-coated sand was designed to be placed in earthenware pitchers that store water. Silver incorporated into alum is also being tested in India.43 Filters and granular charcoal media are sometimes coated with silver to prevent bacterial growth on the surface, but this does not maintain sterility. A slow, selective action against total coliform count is noted, but none against total bacterial count. Long-term use might overcome any bacteriostatic action initially shown.78 In an EPA study, effluent populations from the silver-containing units were about as large as those from the units without silver.11 Bacteria can develop resistance to silver ions through generation of silver reductase. Large-scale use of silver for water disinfection has been limited by cost, difficulty controlling and measuring silver content, and physiologic effects. Short-term field use is limited by its marked tendency to adsorb onto the surface of any container (resulting in unreliable concentrations) and interference by several common substances. Data on silver for disinfection of viruses and cysts indicate limited effect, even at high doses.40,146 The use of silver as a drinking water disinfectant has been much more popular in Europe where silver tablets (MicroPur) are sold widely for field water disinfection. They have not been

Chapter 61: Field Water Disinfection approved by the EPA for this purpose in the United States, but they were approved as a water preservative to prevent bacterial growth in previously treated and stored water. MicroPur Forte tablets (Katadyn) release free chlorine for disinfection and silver for prolonged persistence of antimicrobial activity.

Potassium Permanganate Potassium permanganate is a strong oxidizing agent with some disinfectant properties. It was used extensively before hypochlorites as a drinking water disinfectant.145 It is still used for this purpose and also for washing fruits and vegetables in parts of the world. It is used in municipal disinfection to control taste and odor and is usually employed in a 1% to 5% solution for disinfection. Bacterial inactivation can be achieved with moderate concentrations and contact times (45 minutes at 2 mg/L, 15 minutes at 8 mg/L). A 1 : 5000 (0.5%) solution controlled V. cholerae and S. typhi contamination of fruits and vegetables. The virucidal action has been tested, but without titrations of virus that remained after various periods of contact time, so the rate of action is not known. In most instances, however, a 1 : 10,000 solution destroyed the infectivity of virus suspensions in 30 minutes at room temperature; 30 mg/L was effective in inactivating HAV within 15 minutes.224 Although potassium permanganate clearly has disinfectant action, it cannot be recommended for field use, because quantitative data are not available for viruses and no data are available for protozoan cysts, despite the chemical’s frequent use in some parts of the world. Packets of 1 g to be added to 1 L of water are sold in some countries. A French military guide from 1940 instructed users: “To sterilize water, use a solution of 1 gram of KMnO4 for 100 grams of water. Add this solution drop by drop to the water to sterilize until the water becomes pink. The operation is considered sufficient if the water remains pink for half an hour.”44 The solutions are deep pink to purple and stain surfaces. The chemical leaves a pink to brown color in water at concentrations above 0.05 mg/L. Small deposits of brown oxides settle to the bottom of the water container. A few drops of alcohol will cause this residual color to disappear.

Hydrogen Peroxide Hydrogen peroxide is a strong oxidizing agent but a weak disinfectant.21,146,253 Small doses (1 mL of 3% H2O2 in 1 L water) are effective for inactivating bacteria within minutes to hours, depending on the level of contamination. One million colonyforming units/mL of seven bacterial strains were killed overnight, with 80% kill in 1 hour. Viruses require extremely high doses and longer contact times. Although information is lacking on the effect of hydrogen peroxide on protozoa, it is a promising sporicidal agent in high (10% to 25%) concentrations. Hydrogen peroxide was popular as an antiseptic and disinfectant in the late 19th century and remains popular today as a wound cleanser; for odor control in sewage, sludges, and landfill leachates; and for many other applications. It is considered safe enough for use in foods, yielding the innocuous end products oxygen and water. It is considered nature’s disinfectant, because it is naturally present in milk and honey, helping to prevent spoilage. Solutions lose potency in time, but stabilizers can be added to prevent decomposition.21 Although hydrogen peroxide can sterilize water, lack of data for protozoal cysts and quantitative data for dilute solutions prevents it from being useful as a field water disinfectant.

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Box 61-12. Ultraviolet Irradiation Advantages Effective against all microorganisms Imparts no taste Portable device now available for individual and small group field use and is simple to use Available from sunlight

Disadvantages Requires clear water Does not improve water aesthetics Does not prevent recontamination during storage Expensive Require power source Requires direct sunlight, prolonged exposure; dose low and uncontrolled

Relative susceptibility of microorganisms to ultraviolet: protozoa > bacteria > viruses.

Ultraviolet Light The germicidal effect of ultraviolet (UV) light is the result of action on the nucleic acids of bacteria and depends on light intensity and exposure time. UV lamp disinfection systems are widely used to disinfect drinking water at the community and household level (Box 61-12). In sufficient doses, all water-borne enteric pathogens are inactivated by UV radiation. Bacteria and protozoan parasites require lower doses than enteric viruses and bacterial spores. Giardia and Cryptosporidium are susceptible to practical doses of UV and may be more sensitive because of their relatively large size.125 UV treatment does not require chemicals and does not affect the taste of the water. It works rapidly, and an overdose to the water presents no danger; in fact, it is a safety factor. UV irradiation with lamps requires a power source and is costly. UV light has no residual disinfection power; water may become recontaminated, or regrowth of bacteria may occur.65 Particulate matter can shield microorganisms from UV rays. A portable field unit called Hydro Photon is now available (see Appendix A).

Solar Irradiation There is now strong evidence that UV irradiation by sunlight in UV-A range can substantially improve the microbiologic quality of water and reduce diarrheal illness in developing countries. The technique was practiced in India before 2000 bc. Recent work has confirmed efficacy and optimal procedures of the solar disinfection (SODIS) technique.48,152,209 Transparent bottles (e.g., clear plastic beverage bottles), preferably lying on a dark surface, are exposed to sunlight for a minimum of 4 hours, but some investigations demonstrate improved benefit from several sequential days. Multiple studies demonstrate reduction of enteric bacteria and viruses, and some data exist for reduction of bacterial spores.134 Oxygenation induces greater reductions of bacteria, so agitation is recommended before solar treatment in bottles. UV and thermal inactivation were strongly synergistic for solar disinfection of drinking water in transparent plastic bottles that was heavily contaminated with E. coli for temperatures above 45° C (113° F). Above 55° C (131° F), thermal inactivation is of primary importance.133 Whereas thermal inactivation

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TABLE 61-16. Summary of Field Water Disinfection Techniques

Heat Filtration Halogens Chlorine dioxide

BACTERIA

VIRUSES

+ + + +

+ +/− * + +

GIARDIA/AMEBAE + + + +

CRYPTOSPORIDIUM

NEMATODES/CERCARIAE

+ + − +

+ + +/−† +/−†

*Most filters make no claims for viruses. Reverse osmosis is effective. The General Ecology filtration system claims virus removal. † Eggs are not very susceptible to halogens but have very low risk of waterborne transmission.

is effective in turbid water, UV effects are inhibited.108 Use of a simple reflector or solar cooker can achieve temperatures of 65° C (149° F), which will pasteurize the water (see Heat Disinfection). Where strong sunshine is available, solar disinfection of drinking water is an effective, low-cost method for improving water quality and may be of particular use in refugee camps and disaster areas.

Copper and Zinc A copper and zinc alloy (KDF [kinetic degradation fluxion]) has electrochemical properties that can aid in water treatment. Its main actions are through its strong oxidation-reduction (redox) potential of 500 millivolts due to its propensity to exchange electrons with other substances. It is bacteriostatic with some bactericidal activity. Microorganisms are killed by the electrolytic field, and by formation of hydroxyl radicals and peroxide water molecules. Although KDF has been ruled a “pesticidal device” by the EPA and is used in industry to decrease bacteria levels and control bacterial growth, it should not be used as the sole means of water treatment. KDF is most often used to reduce or remove chlorine, hydrogen sulfide, and heavy metals from water. The redox reactions change contaminants into harmless components: chlorine into chloride, soluble ferrous cations into insoluble ferric hydroxide, and hydrogen sulfide into insoluble copper sulfide. Up to 98% of lead, mercury, nickel, chromium, and other dissolved metals are removed by KDF simply by bonding to the media. KDF controls the buildup of bacteria, algae, and fungi in GAC beds and carbon block filters, extending the life of carbon and improving its effectiveness. KDF can remove the taste of chlorine or iodine from treated water. KDF media can be manufactured as brushes with wire bristles, fine steel wool-like media, or granules. KDF has been incorporated into a few portable field filters but has not yet gained widespread use and no portable products are currently targeting the outdoor market. Products that claim to be purifiers, with KDF destroying all microorganisms, should demonstrate rigorous testing to prove the claims.

Citrus Citrus juice has biocidal properties. Lemon or lime juice has been shown to destroy V. cholerae at a concentration of 2% (equivalent of 2 tablespoons per liter of water) with a contact time of 30 minutes. A pH less than 3.9 is essential, which depends on the concentration of lemon juice and the initial pH of the water. Its activity is greatly reduced in alkaline water.58 Lime juice also killed 99.9% of cholerae on cabbage and lettuce and inhibited growth of V. cholera in rice foods, suggesting that adding lime juice to water, beverages, and other foods can

reduce disease risks.209 More research is needed before this can be recommended as more than an ancillary or emergency measure. Commercial products using citrus cannot be recommended as primary means of water disinfection. Traveler’s Friend is a product marketed for water disinfection that contains citrus extract. Company-sponsored data are convincing for antibacterial and antiviral activity. However, the product was not tested against Giardia cysts. The active chemical disinfectant has not been identified, and a time-dose response has not been generated. Without better data, this product cannot be recommended.


PREFERRED TECHNIQUE Field disinfection techniques and their effects on microorganisms are summarized in Table 61-16. The optimal technique for an individual or group depends on the number of persons to be served, space and weight available, quality of source water, personal taste preferences, and availability of fuel (Tables 61-17 and 61-18). The most effective technique may not always be available, but all methods will greatly reduce the load of microorganisms and reduce the risk of illness. For alpine camping with a high-quality source water, any of the primary techniques is adequate. The only limitation for halogens is Cryptosporidium cysts, but in high-quality pristine surface water the cysts are generally found in insufficient numbers to pose significant risk. Chlorine dioxide or mixed species techniques are currently the only one-step chemical processes available. Surface water, even if clear, in undeveloped countries where there is human and animal activity should be considered highly contaminated with enteric pathogens. Optimal protection requires either heat or a two-stage process of filtration and halogens. Currently, First Need and the Exstream iodine resin–containing water bottle are the only filters with demonstrated ability to meet requirements of a water purifier. Water from cloudy low-elevation rivers, ponds, and lakes in developed or undeveloped countries that does not clear with sedimentation should be pretreated with coagulationflocculation, then disinfected with heat or halogens. Filters can be used but will clog rapidly with silted or cloudy water. Even in the United States, water with agricultural runoff or sewage plant discharge from upstream towns or cities must be treated to remove Cryptosporidium and viruses. In addition, water receiving agricultural, industrial, or mining runoff may contain chemical contamination from pesticides, other chemicals, and heavy metals. A filter containing a charcoal element is the best method to remove most chemicals. Coagulation-flocculation or KDF resin will also remove some chemical contamination.

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TABLE 61-17. Advantages and Disadvantages of Disinfection Techniques HEAT

FILTRATION

HALOGENS

CHLORINE DIOXIDE

TWO-STEP PROCESS Filtration plus halogen, or clarification plus second stage Depends of choice of stages

Availability

Wood can be scarce

Many commercial choices

Many common and specific products

Several new products generate ClO2

Cost

Fuel and stove costs Can sterilize or pasteurize

Moderate expense

Cheap

Most filters not reliable for viruses

Optimal application

Clear water

Taste

Does not change taste

Clear or slightly cloudy; turbid water clogs filters rapidly Can improve taste, especially if charcoal stage

Cryptosporidium and some parasitic eggs are resistant Clear; need increased dose if cloudy

Depends on method, generally inexpensive All organisms

Time

Boiling time (minutes)

Filtration time (minutes)

Contact time (minutes to hours)

Other considerations

Fuel is heavy and bulky

Adds weight and space; requires maintenance to keep adequate flow

Works well for large quantities and for water storage. Some understanding of principles is optimal; damaging if spills or container breaks

Effectiveness

Tastes worse unless halogen is removed or “neutralized”

Clear water, but ClO2 less affected by nitrogenous compounds Unchanged, may leave some chlorine taste Prolonged, if need to ensure Cryptosporidium disinfection More experience and testing would be reassuring; likely to replace iodine for field use.

Highly effective, should cover all organisms

UV New portable commercial device; sunlight Commercial device relatively expensive All organisms

May be adapted to any source water

Requires clear water, small volumes

Depends on sequence and choice of stages; generally improves Combination of time for each stage

Unchanged

More rational to use halogens first if filter has charcoal stage; C-F is best means of cleaning very turbid water, then followed by halogen, filtration or heat

Sunlight currently for emergency situations or no other methods available; commercial product good for high-quality source water, small group use

Minutes

C-F, coagulation-flocculation.

TABLE 61-18. Choice of Method for Various Types of Source Water DEVELOPED OR DEVELOPING COUNTRY SOURCE WATER

“PRISTINE” WILDERNESS WATER WITH LITTLE HUMAN OR DOMESTIC ANIMAL ACTIVITY

Primary concern

Giardia, enteric bacteria

Effective methods

Any single step method†

TAP WATER IN DEVELOPING COUNTRY

CLEAR SURFACE WATER NEAR HUMAN AND ANIMAL ACTIVITY*

Bacteria, Giardia, small numbers of viruses Any single step methodb

All enteric pathogens, including Cryptosporidium 1) Heat 2) Filtration plus halogen (can be done in either order); iodine resin filters (see text) 3) Chlorine dioxide 4) Ultraviolet (commercial product, not sunlight)

CF, coagulation-flocculation. *Includes agricultural run-off with cattle grazing or sewage treatment effluent from upstream villages or towns. † Includes heat, filtration, halogens and chlorine dioxide, ultraviolet.

CLOUDY WATER All enteric pathogens plus microorganisms CF followed by second step (heat, filtration or halogen)

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Halogens need to be used when water will be stored, such as on a boat, in a large camp, or for disaster relief. When only heat or filtration is used before storage, recontamination and bacterial growth can occur. Hypochlorite still has many advantages, including cost, ease of handling, and minimal volatilization in tightly covered containers.140 A minimum residual of 3 to 5 mg/L should be maintained in the water. Superchlorinationdechlorination is especially useful in this situation because high levels of chlorination can be maintained for long periods, and when ready for use, the water can be poured into a smaller container and dechlorinated. Iodine works for short-term but not prolonged storage, because it is a poor algicide. Silver has been approved by the EPA for preservation of stored water. Extensive research in the developing world has demonstrated that water is often recontaminated before use and that proper storage techniques can decrease this risk of contamination.212,252 For prolonged storage, a tightly sealed container is best. For water access, narrow-mouth jars or containers with water spigots prevent contamination from repeated contact with hands or utensils.207 On oceangoing vessels where water must be desalinated during the voyage, only reverse-osmosis membrane filters are adequate. Halogen should then be added to the water in the storage tanks. The preferred method of treatment for the military, when large-scale equipment can be brought to the site, is a reverse osmosis water purification unit (ROWPU), because it can produce high-quality water from a low-quality source. For smaller groups, the military relies mainly on monitored chlorine. Individual means include iodine tablets, chlor-floc tabs, and chlorine liquid bleach.233


PREVENTION AND SANITATION Studies in developing countries have demonstrated a clear benefit in the reduction of diarrheal illness and other infections from safe drinking water, hygiene, and adequate sanitation.100,127,137,172,173,180,212 While a benefit can be demonstrated for these interventions independently, the benefit is greater when all are applied together, especially with appropriate education.43 Wilderness travelers essentially live in conditions similar to those in the developing world, without running water or sanitation. Unfortunately, many wilderness travelers confuse the importance of hygiene with the need to relax their concern about living on the ground. A study of Appalachian trail hikers showed that water disinfection, routine hand washing, and proper cookware cleaning were all associated with decreased diarrhea.22 A Shigella outbreak among river rafters on the Colorado River was investigated and assumed to be water-borne from adjacent Native American communities, but no source was found in the tributaries. It was finally traced to infected guides who were shedding organisms in the stool and contaminating food through poor hygiene.136 Personal hygiene, mainly hand washing, prevents spread of infection from food contamination during preparation of meals.136 A widely publicized study in the United States demonstrated that only 67% of Americans wash hands after using a public toilet. Simple hand washing with soap and water purified with hypochlorite (bleach) significantly reduced fecal contamination of market-vended beverages in

Guatemala.207 No one with a diarrheal illness should prepare food. Sanitation should extend to the kitchen or food preparation area.127 In addition to hand washing, dishes and utensils should be disinfected by rinsing in chlorinated water, prepared by adding enough household bleach to achieve a distinct chlorine odor. Prevention of food-borne contamination is also important in preventing enteric illness (see Chapter 62). Washing fruits and vegetables in purified water is a common practice, but little data support its effectiveness. Washing has a mechanical action of removing dirt and microorganisms while the disinfectant kills microorganisms on the surface. However, neither reaches the organisms that are embedded in surface crevices or protected by other particulate matter. When lettuce was seeded with oocysts, then washed and the supernatant examined for cysts, only 25% to 36% of Cryptosporidium parvum and 13% to 15% of C. cayetanensis oocysts were recovered in the washes. Scanning electron microscopy detected oocysts on the surface of the vegetables after washing.157 Chlorine, iodine, or potassium permanganate is often used for this purpose. Higher concentrations can be used than would normally be palatable for drinking water. With superchlorination-dechlorination, highchlorine concentrations are used to rinse vegetables because the chlorine can be removed with the second step. Aquaclear (NaDCC) chlorine tablet instructions suggest 20 mg/L for washing vegetables. Although effective against most microorganisms, these levels would not be effective against Cryptosporidium or Cyclospora. The ultimate responsibility is proper sanitation to prevent contamination of water supplies from human waste. UV rays in sunlight eventually inactivate most microorganisms, but rain may first wash pathogens into a water source. Some suggest that campers smear feces on rocks. Although desiccation occurs, UV disinfection is not reliable, and feces may wash into the watershed with rain runoff.45 Moreover, it would be repulsive to other campers. In the Sierras, feces left on the ground generally disappeared within 1 month, but it was not known whether disinfection occurred before decomposition or whether the feces washed away, dried, or were blown in the wind.175 Despite more rapid decomposition in sunlight rather than underground, burying feces is still preferable in areas that receive regular use. In the soil, microorganisms can survive for months.235 A Sierra Club study found more prolonged survival in alpine environments.175 The investigator marked group latrines in alpine terrain and returned 1 to 2 years later to dig test trenches. He found a thin crust of decomposition covering unaltered raw waste with high coliform bacteria counts. Microorganisms may percolate through the soil. Most bacteria are retained within 20 inches of the surface, but in sandy soil this increases to 75 to 100 feet233; viruses can move laterally 75 to 302 feet.198 When organisms reach groundwater, their survival is prolonged, and they often appear in surface water or wells.235 The U.S. military and U.S. Forest Service recommend burial of human waste 8 to 12 inches deep and a minimum of 100 feet from any water.233,237 Decomposition is hastened by mixing in some dirt before burial. Shallow burying is not recommended because animals are more likely to find and overturn the feces. Judgment should be used to determine a location that is not likely to allow water runoff to wash organisms into nearby water sources. Groups larger than three persons should dig a

Chapter 61: Field Water Disinfection common latrine to avoid numerous individual potholes and inadequate disposal. To minimize latrine odor and improve its function, it should not be used for disposal of wastewater. In some areas the number of individual and group latrines is so great that the entire area becomes contaminated. Therefore sanitary facilities (outhouses) are becoming common in highuse wilderness areas. Popular river canyons require camp toilets, and all waste must be carried out in sealed containers.


APPENDIX A: DISINFECTION DEVICES Product lines are continuously evolving, and prices change frequently and vary widely. There has been a major consolidation of filter product producers in the United States. Katadyn has acquired PUR and Exstream, while MSR has acquired Sweetwater and Miox. PentaPure (formerly WTC) was purchased by CUNO, which has completely dropped the line of iodine resin–containing portable outdoor filters. They now sell only filters for appliances.

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For most of these products, claims are substantiated only by company sponsored and designed testing. Some results have been extrapolated to similar products. All new products must be tested using a standardized EPA protocol. Depending on claims, filters must demonstrate removal or inactivation of 103 cysts (99.9%), 104 viruses (99.99%), and 106 bacteria under varying water conditions of temperature and turbidity. Objective, comparable test results for these products are not available. Filter capacity is especially variable, depending on clarity of water. Numbers provided for capacity are usually with use of clear water. Comparative testing for filter capacity using slightly turbid river water and following manufacturer instructions for cleaning revealed markedly different values for some filters. All field water has some sediment that clogs filters and reduces flow and capacity. For all filters, it is recommended to pump dilute bleach solution through the unit after each trip and dry thoroughly before storage to decrease bacterial growth in the filter.

APPENDIX A Katadyn Endurance Series PRODUCT

PRICE

Katadyn Pocket Filter (Fig. 61-4) Katadyn Combi (Fig. 61-5)

$189

Katadyn Mini (Fig. 61-6) Katadyn Expedition (Fig. 61-7) Katadyn Ceradyn and Gravidyn (Fig. 61-8) Katadyn Camp S Syphon filter Base Camp (Fig. 61-9)

$90

$160

$890 $160 to $190 $100 $60 $60

www.katadyn.com (800) 755-6701 STRUCTURE/FUNCTION All filters contain a 0.2-micron ceramic candle filter, silver impregnated to decrease bacterial growth. Large units also contain silver quartz in center of filter. Hand-pump; 40-inch intake hose and strainer, zipper case; In-line carbon cartridge available; size: 10 × 2 inches; weight: 23 oz; flow: 0.75 to 1 L/min; capacity 13,000 L. Small hand-pump with ceramic filter and activated charcoal stage; with the optional “PLUS” package, the Combi can be connected to a water faucet for multifunctional use in campers, cottages or boats; can brush ceramic to clean or can separately replace elements; size: 2.4 × 10.4 inches; weight: 19 oz; flow: 1.0 L/min; capacity up to 50,000 L, 200 L for charcoal. Smaller, lighter hand-pump; 31-inch intake hose and strainer, hard plastic enclosure and pump; size: 7 × 2.75 × 1.75 inches; weight: 9 oz; flow: 0.5 L/min; capacity: approx 7000 L. Large hand pump with steel stand for large groups; size (packed in case): 23 × 6 × 8 inches; weight: 12 lb; flow: 4 L/min; capacity (per filter element) to 100,000 L. Gravity drip from one plastic bucket to another with three ceramic candle filter elements. Ceradyn filter candles are ceramic only, whereas Gravidyn filter candles combine ceramic and activated carbon elements. Size: 18 × 11 inches (26-inches high when assembled); weight: 9 lb 4 oz; flow: 1 pt/hr (10 gal/day); capacity to 100,000 L. Gravity siphon filter element available alone (Syphon) or with a 10-L water bag (Camp); size: 12 × 2 inches; weight: 2 lb; flow: 2 gal/hr; capacity 5000 to 20,000 L. Camp gravity siphon filter will be phased out and replaced with Base Camp, which will have a pleated glass (see Katadyn Hiker under Katadyn Backcountry Series) cartridge, rather than ceramic, with a higher flow rate and lower price.

Katadyn Endurance Series Claims Removes bacterial pathogens, protozoan cysts, parasites, nuclear debris. Clarifies cloudy water. If filter clogs, brushing the filter element (which can be done hundreds of times before needing to replace filter element) can restore flow. Claims for removal of viruses by ceramic filters not made in the United States, although testimonials offered imply effectiveness in all polluted waters. Pocket Filter has a lifetime warranty. Comments Well-designed, durable products that are effective for claims. However, high filter volume capacity is optimistic and not likely to be achieved filtering average surface water. Backpacker magazine field tests found the flow comparatively slow, requiring more energy to pump and needing frequent cleaning. Abrading the outer surface can effectively clean ceramic filters, but it is necessary to use the gauge to indicate when filter becomes too thin. Pocket Filter is the original, individual or small group filter design. Metal parts make it durable but the heaviest for its size. Minifilter was designed to be lighter and more cost competitive. Expedition filter is popular for larger groups, especially river trips where weight is not a factor. Complete virus removal cannot be expected, although most viruses clump or adhere to larger particles and bacteria that can be filtered. Silver impregnation does not prevent bacterial growth in filters. Bottle filter with iodine resin allows no contact time and may not provide complete viral protection in all situations.

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PART EIGHT: FOOD AND WATER

Figure 61-4. Katadyn Pocket Filter (Courtesy Katadyn.)

Figure 61-5. Katadyn Combi. (Courtesy Katadyn.)

Figure 61-6. Katadyn Mini. (Courtesy Katadyn.)

Figure 61-7. Katadyn Expedition. (Courtesy Katadyn.)

Chapter 61: Field Water Disinfection

Figure 61-8. Katadyn Drip Ceradyn. (Courtesy Katadyn.)

1401

Figure 61-9. Katadyn Base Camp. (Courtesy Katadyn.)

APPENDIX A Katadyn Backcountry Series (Formerly PUR Water Filters) PRODUCT

PRICE

STRUCTURE/FUNCTION

Katadyn Guide (Fig. 61-10)

$80

Katadyn Hiker (Fig. 61-11)

$60

Hand pump with 150-micron intake filter, 0.3-micron pleated filter with 143-square-inch surface area; includes prefilter and bottle adaptor; size: 9.5- × 2.25-inch; weight: 14 oz; max flow: 1 L/min (36 strokes/L); capacity: 100 gal/cartridge. Hand-pump with 0.3- micron pleated glass fiber with 107-square-inch surface; microfilter; size: 6.5 × 2.5 × 3.5 inches; weight: 11 oz; flow: 1 L/min (48 strokes/L); capacity: 200 gal.

Katadyn Backcountry series Claims Guide and Hiker are microfilters designed for high-quality surface water. They will eliminate Giardia, Cryptosporidium, and most bacteria; activated carbon core “reduces chemicals and pesticides, plus improves taste of water.” Filters with large surface area are “guaranteed not to clog for 1 year.” Comments None of these products contain iodine resin. The former PUR Explorer is no longer in the product line. Guide and Hiker were designed for the domestic backpacking market with higher water quality, where cysts and bacteria are a threat but viruses are less of a problem. The Hiker received top ratings by Backpacker magazine for field tests evaluating user-friendliness. These filters may be used with a halogen disinfectant for international travel or conditions where high levels of contamination are possible.

1402

PART EIGHT: FOOD AND WATER

Figure 61-11. Katadyn Hiker. (Courtesy Katadyn.) Figure 61-10. Katadyn Guide. (Courtesy Katadyn.)

APPENDIX A Katadyn Ultralight Series PRODUCT Mini (see earlier) Exstream Exstream XR (Fig. 61-12)

PRICE

STRUCTURE/FUNCTION Drink-through bottle with three-stage water filter: 1-micron cyst filter for protozoa, ViruStat iodine resin, activated carbon; Exstream weight: 7 oz; capacity: 21 oz (bike bottle size). Exstream XR weight: 8 oz; capacity: 28 oz; cartridge capacity: 26 gal.

Katadyn Exstream Claims Passed EPA tests to remove 3-log cysts, 4-log viruses, and 6-log bacteria. Patented ion-release technology and carbon scrubber dramatically reduce residual iodine. I5 is 1000 times more effective than I3 resin. Comments Currently the only water bottle or filter product available with iodine resin. Drink-through with iodine resin and charcoal allows no contact time and may not provide complete viral protection in all situations. Drink-through design limits Exstream to day use.

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Figure 61-12. Katadyn Exstream. (Courtesy Katadyn.)

APPENDIX A Katadyn Marine Products (Formerly PUR Products) Reverse Osmosis Filters PRODUCT

PRICE

STRUCTURE/FUNCTION

$550

Hand-operated pump, reverse osmosis membrane filter with prefilter on intake line; size: 2.5 × 5 × 8 inches; weight: 2.5 lb; flow: 40 strokes/min; yield: 1 L/hr. Hand-operated pump, reverse osmosis membrane filter with prefilter on intake line; size: 3.5 × 5.5 × 22 inches; weight: 7 lb; flow: 1.2 gal/hr (75 mL/min). Smallest power-operated model in this line of reverse osmosis filters; uses only 4 amps, so it can run for extended periods on alternative power alone; converts to manual operation in emergencies; contains 40% fewer parts than its predecessor. Pump size: 6.75 × 16.5 × 15.5 inches; prefilter 12 × 6 inches; weight: 25 lb (11.33 kg); flow: 1.5 gal/hr.

Desalinator Survivor 06 (Fig. 61-13) Survivor 35 (Fig. 61-14)

$1425

Powersurvivor 40E

$2499

Reverse Osmosis Filters Claims Reverse osmosis units desalinate, removing 98% salt from seawater by forcing water through a semipermeable membrane at 800 psi. In the process, microorganisms are filtered out. The manual operation of these units makes them unique and useful for survival at sea or for use in small craft without power source. Larger, power-operated units are also available. Comments Reverse osmosis units are included here for sea kayaking and small boat journeys in open water. Most large ocean-going boats use reverse osmosis filters. These units can obviate the need to rely solely on stored water or can be carried for emergency survival. The U.S. military uses truck-mounted reverse osmosis filters on land for their ability to handle brackish water and remove all types of microorganisms. Reverse osmosis filters are not practical for land travel because of cost, weight, and flow rates. Desalination units will remove microorganisms, including viruses, which are larger than sodium molecules. Note that the company does not make claims for viral removal because they assume that the membrane is imperfect and some pores will be imprecise, perhaps allowing viral passage. Higherflow power models are available from the company.

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PART EIGHT: FOOD AND WATER

Figure 61-14. Survivor 35. (Courtesy Katadyn.)

Figure 61-13. Survivor 06. (Courtesy Katadyn.)

APPENDIX A British Berkfeld

U.S. distributor: James Filter (800) 350-4170 www.jamesfilter.com

PRODUCT

PRICE

SS-4 (Big Berkey)

$249

Arctic Travel Pure

$165 to $229 $145

LP-2

STRUCTURE/FUNCTION Stacked stainless steel containers with four 9-inch ceramic filters with activated carbon core; gravity flow; weight: 6.0 lb; assembled size: 19.5 × 8.5 inches; flow: 1.3 gal/hr; 2.4-gal capacity of lower container. Smaller stainless steel containers with variable numbers of one to three 7-inch filter elements; lower container capacity: 1 gal. Food-grade high-density polypropylene with two ceramic elements, gravity flow; weight: 4 lb; size: 24 × 10 inches; flow: 1/2 gal/hr; lower container capacity: 2.4 gal.

British Berkfeld Claims and Comments Filter design is very similar to that of Katadyn Drip Filter. These filters are excellent for stationary base camps or expatriate homes. Ceramic filter is 0.9-micron absolute, but filters more than 99.99% of particles larger than 0.5 micron. Removes 100% cysts and 4- to 5-log bacteria. For complete protection, requires chlorine treatment as first step.

APPENDIX A AquaRain Filter Systems www.aquarain.com PRODUCT AquaRain 200 AquaRain 400

(800) 572-2051

PRICE

STRUCTURE/FUNCTION

$149 $199

Stainless steel containers (3 gal each) with two or four silver-impregnated ceramic filters with carbon core; gravity flow; weight: 10 lb; size 22 × 10.25 inches; flow: 32 gal/day with four elements, 16 gal/ day with two elements; capacity: 30,000 to 60,000 gal.

AquaRain Claims and Comments Similar design as Berkfeld and Katadyn, although ceramic elements differ slightly (see earlier comments); 0.2-micron absolute pore size, removes 100% cysts and 4-log reduction of bacteria. No claims for viruses. Clean ceramic elements 200 times before replacement.

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APPENDIX A General Ecology, Inc. PRODUCT

First Need Deluxe Water Filter (Fig. 61-15) Trav-L-Pure (Fig. 61-16) Trav-L-Pure Camper (Fig. 61-17) First Need Base Camp (Fig. 61-18) First Need gravity feed bag attachment (Fig. 61-19)

(610) 363-7900 www.general-ecology.com

PRICE

$93 $144 $65 $500

STRUCTURE/FUNCTION All filters (except Microlite) contain 0.1-micron (0.4-micron absolute) “structured matrix” filter in removable canister. Hand pump with intake strainer; outflow end connects directly to common water bottle and adaptors available for platypus bottles; self-cleaning prefilter float; size: 6 × 6 inches; weight: 15 oz; flow: 1.6 L/min; capacity: 100 to 400 L. Filter and hand pump in rectangular housing (1.5 pt capacity); pour water into housing, then pump through prefilter and microfilter; size: 4.5 × 3.5 × 6.75 inches; weight: 22 oz; flow: 1 to 2 pt/min; capacity: 100 to 400 L (carrying case included). Trav-L-Pur canister with attachment to hose bibb for RVs and trailers; requires water pressure of 20 psi; flow: 0.5 gpm (1.9 L/min); capacity: 570 L. Stainless steel casing and hand pump connected with tubing; capacity 1000 gal; size: canister, 4.8 × 5.4 inches; pump, 1.5 × 10.5 inches; weight: 3 lb; flow: 2 L/min (carrying case included). Also available with electric pump and can be hooked up in series to provide higher capacity and flow. Allows the user to let gravity push water through the filter.

General Ecology Filters General Ecology also has an extensive product line of larger-capacity filters for use on cars, boats, and aircraft, and for other situations requiring high-volume output where power is available. These utilize the Seagull IV purifier cartridge with a pump that pushes water through the system and a prefilter that can be cleaned. They can be operated off regular current or vehicle battery. Claims First Need Filter is a proprietary blend of materials including activated charcoal. “Microfiltration” with 0.1-micron retention (0.4 absolute) “removes bacteria and larger pathogens” (cysts, parasites). “Adsorption and molecular sieving” carbon absorbers remove chemicals and organic pollutants that cause color and taste; cavities in surface of adsorption material draw particles in deeper. Does not remove all dissolved minerals or desalinate. Proprietary process also creates ionic surface charge that removes colloids and ultrasmall particles through “electrokinetic attraction.” Has passed laboratory tests as a purifier under single-pass conditions without added chemicals or hold time, reducing test virus by 104 as well as bacteria by 106 and Cryptosporidium by 103. Although it has not been tested with hepatitis virus, testing with rotavirus and poliovirus indicates effectiveness against viruses. Microlite removes sediment, protozoan cysts, algae, and chemicals (including iodine), and improves color and taste of water. Iodine tablets are included to kill bacteria and viruses when these organisms are a concern. Comments Reasonable design, cost, and effectiveness. All units (except Microlite) use the same basic filter design. Most testing with E. coli and Giardia cysts show excellent removal. Charcoal matrix will remove chemical pollutants. This is the only company that has met EPA standards for 4-log reduction of viruses through filtration without halogens. Despite viral claims, recommend caution in highly polluted water; prior disinfection with halogen or clarification with coagulation-flocculation would provide additional security and coagulationflocculation would extend filter life, whereas filter carbon would subsequently remove halogen. The filter cannot be cleaned, although it can potentially be back-flushed; so it must be replaced when clogged. The Microlite is designed primarily for day use or light backpacking. Used alone, it makes microbiologic claims for protozoan cysts (Giardia and Cryptosporidium) only. Iodine or chlorine should be used as pretreatment with this filter for all water except pristine alpine water in North America. This filter is compact, lightweight, and designed for low-volume use with inexpensive, easily changed filter cartridges.

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PART EIGHT: FOOD AND WATER

Figure 61-16. Trav-L-Pure. (Courtesy General Ecology, Inc.) Figure 61-15. First Need Deluxe. (Courtesy General Ecology, Inc.)

Figure 61-17. Trav-L-Pure Camper. (Courtesy General Ecology, Inc.)

Figure 61-18. First Need Base Camp. (Courtesy of General Ecology, Inc.)

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Figure 61-20. Waterworks EX. (Courtesy MSR.) Figure 61-19. First Need Gravity feed. (Courtesy General Ecology, Inc.)

APPENDIX A MSR Longevity Series

(206) 624-7948 www.msrcorp.com/filters

PRODUCT

PRICE

Waterworks EX Total Filtration System (Fig. 61-20)

$130

Miniworks EX (Fig. 61-21) Field maintenance kit

$80 $10

STRUCTURE/FUNCTION Four filter elements of decreasing pore size: porous foam intake filter, 10-micron stainless steel wire mesh screen, cylindrical ceramic filter with block carbon core, then 0.2-micron pharmacologicgrade membrane filter; pressure relief valve releases at 90 to 95 psi; hand pump with intake tubing; storage bag (2 or 4 L) attaches directly to outlet of pump. Size: 9 × 4 inches; weight: 19 oz; flow: 1 L/90 sec (1 L/min max); capacity: up to 2000 L (400 L under average conditions). Similar external design to Waterworks, but uses a slightly different ceramic filter and lacks the final membrane filter; weight: 16 oz; flow rate: 1 L/min; capacity: 400 to 2000 L. Silicone, replacement O-rings

MSR Filter Claims Fully field-maintainable, meaning all elements can be removed, cleaned, and replaced. Removes protozoa (including Giardia and Cryptosporidium), bacteria, pesticides, herbicides, chlorine, and discoloration. Both filters meet EPA standards for removal of cysts and bacteria. Ceramic filters reduced turbidity from 68.8 NTU (nephelometric turbidity units) to 0.01 NTU. Carbon has been shown to reduce levels of iodine from 16 mg/L to less than 0.01 mg/L for at least 150 L. Comments Excellent filter design and function. Prefilters protect more expensive inner, fine-pore filters. Effective for claims; high quality control and extensive testing. No claims are made for viruses, although clumping and adherence remove the majority (currently 2- to 3-log removal, but not 4-log required for purifiers). The company is working on a microfilter that will effectively remove viruses. Until they succeed, the filter should not be considered reliable for complete viral removal from highly polluted waters in developing countries. Reservoir bag that attaches to outflow for filtered water storage is convenient. Design and ease of use are distinct advantages. Filter can be easily maintained in the field; maintenance kit and all replacement parts available. Ceramic filters can be effectively cleaned by abrading outer surface many times without compromising the filter. A simple caliper gauge indicates when filter has become too thin for reliable function. Miniworks was rated very highly in Backpacker magazine field tests.

1408

PART EIGHT: FOOD AND WATER

Figure 61-22. Sweetwater Microfilter and Purifier Solution. (Courtesy MSR.)

Figure 61-21. Miniworks EX. (Courtesy MSR.)

APPENDIX A MSR Simplicity Series PRODUCT Sweetwater Microfilter (Fig. 61-22) Purifier Kit with Microfilter, purifier, and platypus water bag Purifier solution

www.msrcorp.com/filters PRICE $60 $75 $9

STRUCTURE/FUNCTION Lexan body and pump handle; 100-micron metal prefilter; in-line 4-micron secondary filter; labyrinth filter cylinder of borosilicate fibers removes pathogens to 0.2 micron; granular activated carbon; safety pressure relief valve; end-of-life indicator; outflow tubing has universal adapter that fits all water bottles; optional input adapter that attaches to sink faucet while traveling; size: 7.75 × 3.5 inches; weight: 11 oz; flow: 1.25 L/min (new filter); capacity: 200 gal. A chlorine-based purifier solution containing 3.5% sodium hypochlorite; add 5 drops to each liter of filtered water, mix for at least 10 seconds, and wait 5 minutes.

Sweetwater Filter Claims Eliminates Giardia, Cryptosporidium, and other critical bacterial and protozoan pathogens, pollutants, heavy metals, pesticides, and flavors. Lighter, more compact, and more durable than comparable models; easiest to clean or replace. The company recycles filter cartridges. Comments Well-designed filter at a reasonable price. Practical design features like universal bottle adapter. Pressure-release valve indicates when filter needs cleaning, but this can be a problem as the filter clogs. A brush is provided for cleaning and cartridges are replaceable. Rated highly in Backpacker magazine field tests. The iodine resin–containing Viral Guard was recently removed from the market. New in-house testing of the Guardian filter with iodine resin attachment failed to inactivate poliovirus at levels required by EPA standards under certain conditions. The failure of the viral testing was a surprise to the company, because a reliable laboratory had originally tested the product with the iodine resin and verified adequate levels of viral inactivation. It is unclear whether this indicates a problem in general with the iodine resins or with the specific design of their iodine resin filter attachment. Because they were unable to solve the problem, the company has developed a specially formulated chlorine solution (Purifier Solution) for use before filtration when high levels of contamination are possible, including viruses.

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APPENDIX A MSR pump free series

www.msrcorp.com/filters/pump_free

PRODUCT

PRICE

STRUCTURE/FUNCTION

$130

New technology created by military, uses salt, water, and electrical current generated from camera batteries to produce mixed-species disinfectant solution that is added to water. Kit comes with pen, batteries, salt packet, indicator strips, instructions, storage sack. Refills of salt cartridge are available. Pen 3.5 oz; kit 8 oz.

Miox Purifier (Fig. 61-23)

Claims Just add water, shake, and press a button. Solution generated is then added to drinking water. Inactivates all bacteria, viruses, and protozoa. Viruses and bacteria require dwell time of 15 min, Giardia 30 min, Cryptosporidium 4 hours. Can be used for individuals or groups. LED (light-emitting diode) lights indicate low battery or inadequate reagents (salt and water). Test strips are used to test water for adequate chemical residual. Comments Truly new technology. The science has been known for some time and is used in large commercial processes (www.miox.com), but previously was not available in portable design. Although difficult to measure various disinfectant species generated, testing has confirmed that disinfectant activity is greater than with comparable concentrations of sodium hypochlorite. The active oxidant disinfectant that kills Cryptosporidium is assumed to be chlorine dioxide. The extended dwell time indicates low concentrations of this disinfectant and the need to plan for prolonged contact time, if Cryptosporidium is a strong concern. High technology approach is appealing to some, but intimidating to others. The indicator lights and test strips add reassurance that the process is proceeding effectively. Although this technique can be used for large volumes, this instrument generates enough for only 1 L at a time and may be difficult to use for larger volume containers.

Figure 61-23. Miox Purifier. (Courtesy MSR.)

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PART EIGHT: FOOD AND WATER

APPENDIX A Sawyer Products

http://www.sawyerproducts.com/

PRODUCT Biologic Water Filter (Fig. 61-24) Viral water Purifier (includes faucet adaptor) Viral water Purifier Kit (in-line filter (Fig. 61-24), water bottle (Fig. 61-25), faucet adapter, gravity bag)

PRICE

STRUCTURE/FUNCTION

$60

0.2-micron (absolute) hollow fiber membrane filter, which is a cluster of microtubules. Viral filter has 0.02 micron fiber filter. Water is drawn through the walls of the tubules either by suction or by suction, gravity or pressure applied in squeezing the bottle; Both filter cartridges available as inline cartridge for backpack water systems, gravity drip, faucet in-line systems, or polycarbonate drinking bottle with filter. Activated charcoal prefilter cartridge included for optional use; Capacity more than 500 gallons, depending on clarity of source water; rate depends on method used, 5 gallons/30min via gravity feed system; 30 mL/sec from drink through.

$120 $150

Claims Microtubules are new technology that allow unprecedented flow rates and 0.2 or 0.02 micron absolute filtration. Prefilter removes lead, chlorine, odors, taste sediment, while the microfilter removes bacteria, protozoa, and cysts. Biologic filter removes 7-log (99.9999%) bacteria and 6-log protozoa but makes no claims for viruses; add chlorine to kill viruses. Viral filter claims >5 log removal through mechanical filtration. Filter is freeze-resistant, which is not true of many solid filters. Sawyer will supply liquid and tablet form of chlorine to use in combination with the filter to purify highly questionable water. Comments This filter was carefully designed and tested. The potential advantage over other water bottle filters is the hollow fiber technology that may provide faster filtration with less pressure. The charcoal cartridge compromises some of this low-pressure flow, so it is supplied separately for use only when needed. Highly versatile filter product that can be used as water bottle or with camel-back for individuals, gravity drip for small groups, or in-line for added microbiologic protection in households. This is the first low-pressure filter to claim viral removal through mechanical filtration alone.

Figure 61-24. Sawyer Water Filter Bottle. (Courtesy Sawyer Products.)

Figure 61-25. Sawyer filter. (Courtesy Sawyer Products.)

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APPENDIX A Hydro-Photon, Inc. PRODUCT Steri-Pen (Figs. 61-26 and 61-27) Replacement element available Water bottle prefilter

(888) 826-6234 www.hydro-photon.com PRICE $150

$10

STRUCTURE/FUNCTION Portable, battery-operated ultraviolet water disinfection system. Disinfects up to 16 oz of clear water in less than 1 min and 32 oz in 90 seconds by stirring UV element in water. Uses four AA batteries (disposable or rechargeable): alkaline batteries provide 20 to 40 treatments, lithium batteries 130 to 140 treatments; weight: 8 oz, with batteries; length, 7.6 inches, width 1.5 inches; lamp lasts 5000 treatments (625 gal). Comes with a thermoformed nylon carrying case. Prefilter available for removing particulate matter; fits on top of Nalgene water bottle.

Steri-Pen Claims Highly effective against bacteria, viruses, and protozoa, including Cryptosporidium oocysts. Dosage selector for 16- or 32-oz water treatment. Alkaline batteries not recommended for cold water treatment. Unit automatically turns off lamp after UV dose is delivered. Dose counter indicates when lamp replacement is necessary. Microbiologic testing conducted at the University of Arizona, the University of Maine, the Oregon Health Sciences University, and HydroPhoton against multiple types of bacteria, viruses, Giardia, and Cryptosporidium shows that Steri-Pen meets the standard as set forth in the U.S. EPA Guide Standard and Protocol for Testing Microbiological Water Purifiers, destroying in excess of 99.9999% of bacteria, 99.99% of viruses, and 99.9% of protozoa. Comments In general, UV light for water disinfection is well established and widely used for water treatment in many large and varied applications. Until now, these have required a larger, fixed power and light source. The use of this portable technology is currently limited to small volumes of clear water; however, the potential is great for further advances that will increase its uses in the field and make it less expensive. The testing for this device can be found on Hydro-Photon’s website. Testing was only successful in clear water, not in EPA “worse case scenario” water unless prefiltered with microfiltration. The simplicity and rapidity of this technique is appealing.

Figure 61-26. Steri-Pen. (Courtesy Hydro-Photon, Inc.)

Figure 61-27. Steri-Pen in use. (Courtesy Hydro-Photon, Inc.)

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APPENDIX A Stearns Outdoors, Inc. (Formerly Basic Designs Filters) PRODUCT

(800) 697-5801 www.stearnsinc.com

PRICE

High-Flow Ceramic Water Filter (Fig. 61-28)

$72

Ceramic Filter Pump (Fig. 61-29)

$26

STRUCTURE/FUNCTION Ceramic filter with 0.5- micron absolute retention size and carbon center; gravity filtration with element placed near the end of a 6-foot outflow tube connected to a 7.5-L heavy plastic collection bag, providing 2 to 3 lb of hydrostatic pressure through the in-line filter; packing size: 4 × 4 × 8 inches; weight: 1 lb 2 oz; flow rate: 15 L/hr; capacity: 500 to 1000 L. Hand pump with ceramic cartridge at end of intake tubing and polyurethane prefilter; size: pump, 8 × 1 inch; filter, 4 × 3 inches; 18-inch tubing; weight: 7 oz; flow: 0.4 L/min; capacity: 500 gal.

Stearns/Basic Designs Filters Claims Ceramic filter removes Giardia, Cryptosporidium, cysts, tapeworm, flukes, other harmful pathogens larger than 1 micron. Carbon removes color, tastes, and odors. Filter can be cleaned with an abrasive pad. Filter pump makes claims for cysts only. Pump is easily serviced in the field; ceramic cartridge is replaceable. Comments Ceramic candle filters are effective filtering elements, and charcoal is an effective adsorbent. No claims for virus removal. Although the pore size is larger than that of most filters, the low-pressure depth filter increases retention of bacteria. The simple gravity design decreases cost and moving parts. Filtration rate will be slow, and this filter could clog rapidly, in that there is no prefilter for larger particles. Gravity drip can be convenient after making camp, if no time restraints. The filter pump is the most practical hand-pump unit and is reasonably priced, but the ceramic filter can break. The intake is close to the pump, which can be awkward, and the foam sleeve makes it float, requiring an extra hand to hold it underwater. This filter rated poorly on field user tests by Backpacker magazine.

Figure 61-28. Stearns High-Flow Ceramic Water Filter. (Courtesy Stearns, Inc.)

Figure 61-29. Stearns Ceramic Filter Pump. (Courtesy Stearns, Inc.)

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APPENDIX A Timberline Filter PRODUCT Timberline Eagle Replacement filter Base Camp Filter Replacement filter

www.timberlinefilters.com PRICE

STRUCTURE/FUNCTION

$26 $16 $66 $26

1-micron fiberglass and polyethylene matrix; hand pump; size: 9 × 1 to 3 inches; weight: 6 oz; flow: 1 qt in 1.5 min. Gravity drip 2-micron filter (same filter element as the original Timberline filter) with 2-gal reservoir coated nylon bag; flow 1.5 pt/min with 5-ft of elevation; weight of reservoir, tubing, and filter element: 11 oz.; capacity: 200 qt depending on clarity of water.

Timberline Filters Claims Removes Giardia and Cryptosporidium cysts. No claims for bacteria or viruses. Comments Lightweight, inexpensive filters with limited applications. Should be used in conjunction with chemical treatment.

APPENDIX A McNett Aquamira Filters PRODUCT

www.Mcnett.com PRICE

STRUCTURE/FUNCTION

Water Filter Bottle (Fig. 61-30)

$19

Frontier (Fig. 61-31)

$10

Nalgene squeeze bottle with 2-micron carbon block filter; bottle size: 22 oz; weight: 5 oz; capacity: 200 refills. Drink-through straw with 2-micron charcoal filter. Capacity: up to 20 gal depending on clarity of water.

Aquamira Filters Claims Both filters remove Giardia and Cryptosporidium cysts. “If viruses or smaller bacteria are suspected, use a certified chemical treatment or boil water before filtering. Removes chlorine and other chemical flavors. Chemical treatments are recommended when viruses may be present in the water, as when traveling in developing countries or popular natural areas. Used in conjunction with chemical treatment, the Aquamira filter provides the benefit of removing organisms that may be too large to be inactivated by chemical treatment.” Frontier is “just in case” filter for emergency use backup to drink from any bottle or cup or directly from water sources. The Frontier Filter can also be used in conjunction with chemical treatments for maximum protection. Comments Water bottle is reasonable for day trips, but the nominal pore size is not adequate for bacteria, so the filter must be used with chemical treatment if viral or bacterial contamination is a concern. Straw filters are not very useful. In general, they do not perform well on testing. A better means of emergency backup is to carry chemical treatment such as halogen or chlorine dioxide.


APPENDIX B: CHEMICAL

See text for further discussion of halogens, chlorine dioxide, and silver.

allows much smaller volumes to be used (8 mg/0.1 mL), which can be measured with a 1-mL syringe or dropper (2 drops). The stability and simplicity of iodine crystals have led to their testing for in-line systems that provide continuous water disinfection for remote households and small communities. In these designs, residual iodine is removed with GAC.57,205

Iodination Crystals (Saturated Solution). Because of limited solubility in water, iodine crystals may be used for disinfection. In one technique for field use, 4 to 8 g of crystalline iodine is put in a 1- to 2-ounce bottle, which is then filled with water.99 A small amount of elemental iodine goes into solution (no significant iodide is present); the saturated solution is used to disinfect drinking water. Water can be added to the crystals hundreds of times before they are completely dissolved. An alternative technique is to add 8 g of iodine crystals to 100 mL of 95% ethanol.222 Increased solubility of iodine in alcohol makes the solution less temperature dependent and

Product Polar Pure www.polarequipment.com Price: $10.50 Widely available through suppliers of outdoor products (e.g., Campmor) Formulation 8 gm of iodine crystals in a 3-oz glass bottle filled with water; 30- to 50-micron fabric prefilter provided; “trap” in bottle to catch crystals when pouring off water; capacity: 2000 quarts; weight: 5 oz.

DISINFECTION PRODUCTS

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PART EIGHT: FOOD AND WATER

Figure 61-31. McNett Aquamira Frontier. (Courtesy McNett Corp.)

its large disinfectant capacity, small size, and light weight. The glass bottle can break. For many years, Polar Pure Carbonics has been trying to get FDA approval for iodine crystals in alcohol. Its failure to receive approval to market this new product has no relation to effectiveness or safety. At this time, iodine in alcohol is a viable option that allows for much smaller doses due to higher solubility of iodine in alcohol. Figure 61-30. McNett Aquamira Water Filter Bottle. (Courtesy McNett Corp.)

Instructions The bottle cap is used to measure iodine solution. One capful is approximately 6.5 mL. Directions and color dot thermometer are printed on the bottle. Recommended dose (2 capfuls if iodine solution is 20° C [68° F]) yields 4 ppm iodine when added to 1 quart of clean water. Contact time depends on temperature of the water to be consumed; warm water to 20° C (68° F) before adding iodine to shorten contact time.

Comments Saturated aqueous solution of crystalline iodine is an excellent and stable source of iodine. Recommendations are adequate for clear, warm water, but because it is not feasible to warm all water, extend contact time to 1 to 2 hours for very cold water. Temperature of the bottle affects the concentration of iodine in the saturated solution (200 ppm at 10° C [50° F], 300 ppm at 20° C [68° F], 400 ppm at 30° C [86° F]),42,84 which is the reason for the color-dot thermometer on the bottle. In the field, it may be easier to warm the bottle in an inner pocket than to estimate temperature and adjust the dose. The supernatant should be carefully decanted or filtered to avoid ingestion of the crystals255; this is aided by the weight of the crystals, which causes them to sink. Many people prefer crystalline iodine because of

Iodine Tablets The tablets used by the U.S. military and sold in the United States for water disinfection contain tetraglycine hydroperiodide, which is 40% I2 and 20% iodide.42,145 Tetraglycine hydroperiodide was originally developed and chosen as a preferred technique by the military for individual field use because of its broad-spectrum disinfection effect, ease of handling, rapid dissolution, stability, and acceptable taste.109,154,166,188 Each tablet releases 8 mg/L of elemental iodine into water. An acidic buffer provides a pH of 6.5, which supports better cysticidal than virucidal capacity but should be adequate for both. Tablets have the advantages of easy handling and no danger of staining or corroding if spilled. They are stable for 4 to 5 years under sealed storage conditions and for 2 weeks with frequent opening under field conditions, but they lose 30% of the active iodine if bottles are left open for 4 days in high heat or humidity. Products Potable Aqua (Wisconsin Pharmaceuticals) Price: 50 tablets, $5; with P.A. Plus Neutralizing tablets, $8 Weight: 2 oz Widely available through suppliers of outdoor products Also sold as Globaline and EDWGT (emergency drinking water germicidal tablets)

Chapter 61: Field Water Disinfection

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Instructions One tablet is added to 1 quart of water. In cloudy or cold water, add two tablets. Contact time is only 10 to 15 minutes in clear, warm water, and much longer in cold, cloudy water (see Table 61-13). Potable Aqua is now sold with “neutralizing” tablets made of ascorbic acid. Ascorbic acid converts iodine to iodide, removing the taste and color.

Formulations/Instructions Redi-Chlor tablets come in different sizes and can be broken in half or fourths to treat different quantities of water. Recommended dose results in 2 to 5 mg/L residual chlorine. Add more for very cold water or if faint chlorine smell is not detected after contact time. Available in blister packs of 50 one-tenth of a gram tablets to treat 1 gal per tablet, or blister packs of 50 onefourth of a gram tablets to treat 5 gal per tablet.

Comments This method was developed by the military for troops in the field. Advantages are unit dose and short contact time, but these concentrations create strong taste that is not acceptable to many wilderness users. The military requirements dictated a short contact time (10 minutes in clear, warm water), thus the relatively high concentration of iodine (8 to 16 ppm). With adequate contact time and moderate temperatures, one tablet can be added to 2 quarts of water to yield 4 ppm of free iodine (see Table 61-15). Rather than use two tablets in cloudy water, clarify the water first. Ascorbic acid (vitamin C) neutralizer reduces iodine to iodide, which has no color or taste, but also has no disinfecting action. Esthetically, iodine is “removed” from the water. However, iodide is physiologically active, so concerns about toxicity or physiologic activity remain. For short-term use, iodine is safe and removing the taste is a major benefit.

Comments This is a convenient source of hypochlorite, which can also be used for superchlorination (see text).

Chlorination See text for chemistry and effectiveness of free chlorine. Sodium Hypochlorite Household Bleach Liquid household bleach is a hypochlorite solution that comes in various concentrations, usually 5.25%. This has the convenience of easy availability, low cost, high stability, and administration with a dropper. Sodium hypochlorite solutions are vulnerable to significant loss of available chlorine over time. Stability is greatly affected by heat and light. Five percent solution loses about 10% of available chlorine over 6 months at 21° C (70° F) and freezes at −4.4° C (24° F). If bleach containers break or leak in a pack, the liquid is corrosive and stains clothing. Products Drinkwell from Katadyn Available from FirstWater www.firstwater.info/noflash/pdct_ prsnel_chem.html 10-mL bottle can treat 100 L using 3 drops/L. Stable for 3 years if stored under 25° C (77° F). SweetWater Viral Stop 2-oz squeeze dropper bottle Price: $9 Calcium Hypochlorite (dry chlorine) Calcium hypochlorite is a stable, concentrated, dry source of hypochlorite that is commonly used for chlorination of swimming pools. Redi-Chlor www.redi-chlor.com 50 tablets in blister packs Price: $9.95 Calcium hypochlorite is widely available in tablets or tubs of granules through chemical supply or swimming pool supply stores.

Halazone Tablets Tablets contain a mixture of monochloraminobenzoic and dichloraminobenzoic acids.62 Each tablet releases 2.3 to 2.5 ppm of titratable chlorine.154 These tablets have been criticized because the alkaline buffer necessary to improve halazone dissolution decreases disinfectant efficiency, requiring unacceptably high concentrations and contact times (six tablets yield 15 mg/L with recommended contact time of 60 minutes) for reliable disinfection under all conditions.188 The shelf life is 6 months; potency decreases 50% when stored at 40° to 50° C (104° to 122° F). A new bottle should be taken on each major trip or changed every 3 to 6 months. Halazone has been replaced by newer tablet formulations of chlorine. Chlorination-Flocculation Tablets contain alum and 1.4% available chlorine in the form of dichloroisocyanurate (sodium dichloro-s-triazinetrione) with proprietary flocculating agents. Bicarbonate in the tablets promotes rapid dissolution and acts as a buffer. One 600-mg tablet yields 8 mg/L of free chlorine. Testing by the U.S. military demonstrated biocidal effectiveness similar to iodine tablets under most conditions.165,167,169 Extended contact time was necessary for complete viral removal in some of the tests. Because of the ability to flocculate turbid water, the action was superior to that of iodine in some poor-quality water. Chlor-floc (Deatrick & Associates) 30 tablets individually sealed in foil packets; weight 1.6 oz.; capacity: 30 L (8 gal) Price: $7 Chlor-Floc is widely available through military surplus and survival websites AquaPure and AquaCure are other brands that may be available. Proctor and Gamble has developed a packet with chlorination and flocculation powder called PUR Purifier of Water that is now available to large relief organizations for use outside the United States in disaster and conflict situations. They will also begin distributing for individual users in the developing counties. Formulations/Instructions One tablet for the clarification and disinfection of 1 L of water from polluted sources at temperatures of 25° C (77° F). At 5° C (41° F), use two 600-mg tablets to provide 2.8% available chlorine. To strain the sediment, pour the water through the cloth provided. The tablets are stable for 3 years if stored in their packaging out of the heat. Comments This is one of the individual field methods for U.S. military troops and suggested for potential use in developing countries by the WHO. It is an excellent one-step technique for cloudy and highly polluted water (see Table 61-15).

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Alum is a widely used flocculant that causes suspended sediment, colloids, and many microorganisms to clump, settle to the bottom, and readily be filtered or strained. Most Cryptosporidium oocysts would be removed by the flocculation. Some chlorine reacts with contaminants and is inactivated. It is important to confirm some chlorine taste and smell at the end of the contact time. For added safety, prolong the contact times up to 1 hour of contact time in cold, polluted, and dirty water. In clear water without enough impurities to flocculate, the alum causes some cloudiness and leaves a strong chlorine residual. After treatment, water should be poured through a special cloth to remove floc and decrease turbidity.

Sodium Dichloroisocyanurate (NaDCC) NaDCC is a stable, nontoxic chlorine compound that releases free active chlorine and forms a mildly acidic solution, which is optimal for hypochlorous acid, the most active disinfectant of the free chlorine compounds. Free chlorine is in equilibrium with available chlorine that remains in compound, providing greater biocidal capacity. NaDCC is more stable and provides more free, active chlorine than other available chlorine products for water disinfection. Aquatabs www.firstwater.info/noflash/pdct_prsnel_chem.html Similar product may be available under the brand Aquaclear, Puritabs, and Kintab (Bioman Products) Formulation/Instructions Each tablet contains sodium dichloroisocyanurate (NaDCC) in paper/foil laminate. When dissolved in 1 L of water, each effervescent tablet releases 10 mg of free chlorine, with 50% of the available chlorine remaining in compound and released as free chlorine to be used up by halogen demand. Tablets are available in multiple strengths and can be broken to treat smaller quantities of water. Larger quantities are available in tubs. Aquatab also makes slow-dissolving tablets for larger quantities of water that contain trichloroisocynauric acid (TCCA), which acts similarly to NaDCC. Surface water disinfection of clear water is accomplished at 10 mg/L in 10 min, 1 mg/L for tap water, and 2 to 5 mg/L for well water. NaDCC can also be used to wash fruits and vegetables in concentrations of 20 mg/L. The tablets have a 3-year shelf life; cost depends on size and quantity of tablets. Comments This is a good source of chlorine available in multiple dosage forms, including individually wrapped tablet form; larger concentration tablets allow for disinfection of large quantities of water for shock chlorination of tanks and other storage systems. Chlorine Dioxide Until recently, chlorine dioxide could be used only in large-scale water treatment applications, because it is a volatile gas that must be generated on-site. Several new chemical methods for generating chlorine dioxide on-site can now be applied in the field for small quantity water treatment. Advantages of chlorine dioxide are greater effectiveness than chlorine at equivalent doses and the ability to inactivate Cryptosporidium oocysts with reasonable doses and contact times. Katadyn MicroPur MP-1 www.katadyn.ch/site/us/home/outdoor_products

Micropur is also available through Black Mountain, Campmor, and others at www.katadyn.net/micropur.html (Black Mountain commercial site markets a range of Katadyn products) Price: 30 tablets, $13.95 Engelhard (www.engelhard.com) produces a similar product called Aseptrol, a chlorine dioxide release agent in various strength tablets and powders that are EPA registered for a wide range of disinfection tasks Formulation/Instructions The primary chemistry reaction that produces chlorine dioxide (ClO2) in MP-1 tablets is the acid-chlorite reaction using sodium acid sulfate as the acid, a well-known reaction for ClO2: 5NaClO2 + 4NaHSO4 → 4ClO2 + NaCl + 2H2O + 4Na2SO4 A small amount of chlorine in the tablet also catalyzes the otherwise sluggish reaction. These tablets generate chlorine dioxide only when coming into contact with water. Shortly after a tablet is immersed in water, a saturated solution of the soluble solid constituents forms within the matrix of the tablet. ClO2 is rapidly formed within the pores and then carried into the bulk solution by CO2 effervescence, which ensures that the resultant solution is well mixed without the user having to agitate the container. After the chlorine dioxide gas is released, the material reduces into common salts. Company testing shows killing of bacteria and viruses within 15 minutes in any water conditions, and inactivation of Giardia and Cryptosporidium within 30 minutes in clear, warm water and 4 hours in cold and dirty water. One tablet is used for treating 1 quart of water. Instructions are to insert rapidly into water after removing from package and avoid exposure to sunlight during disinfection contact time.

Comments This is a major advance in portable and point-of-use water disinfection. The product is EPA registered as an antimicrobial water purifier. The extended contact time in cold, dirty water ensures that sufficient chlorine dioxide is generated and adequate residual remains for sufficient time to treat water in all conditions. It is more reasonable to clarify the water to improve taste and esthetics and warm the water to reduce contact time. Company testing is well designed with multiple controls. They also have documentation that residual concentrations of chlorine dioxide were well maintained during the recommended contact times. Chlorine dioxide does not have extended persistence in water, so it should not be used to maintain microbiologic purity of stored water. Sunlight breaks down chlorine dioxide, so for optimal effect, keep the water bottle in a dark location, such as inside a pack or bag, during disinfection time. aqua mira (McNett Corp) www.mcnett.com Pristine (Canada) www.pristine.ca A stabilized solution of chlorine dioxide is mixed with phosphoric acid, which activates the chemical and is then mixed with water for disinfection. Contact times for inactivation of Cryptosporidium by Pristine range from 15 minutes in warm water using a triple dose to 7 hours using a single dose in very cold water. The two solutions are mixed together in a mixing cap

Chapter 61: Field Water Disinfection and added to the water for treatment. Advantages include effectiveness across broad range of water, temperature, and pH; no aftertaste or odor; unaffected by freezing. Personal size: two 1 oz plastic bottles; capacity: up to 120 liters (30 gal) of water; weight: 2.8 oz; $10.99. Pristine also makes 2-oz bottles, and larger packages for relief agencies to disinfect large quantities.

Comments The chemistry of generating chlorine dioxide through a similar method is well described. The company is responding to concerns raised by the EPA, so product is still pending EPA approval as a purifier in the United States. It does have limited approval now for bacteria. The Canadian product makes full claims, including claims for Cryptosporidium. Testing data will be available from the company when EPA approval is obtained. It will be important to note the persistence of the active disinfectant. Given the volatility of chlorine dioxide and slow reaction times, concentrations may be variable due to the mixing process and time delay. Likely the EPA delay is related to performance in cold and dirty “worst case” test water, which may be an issue in disaster situations, but it is not often encountered by wilderness users. McNett is exploring other formulations of chlorine dioxide. They are currently developing large-scale systems for relief organizations. Chlorine Dioxide and Mixed Species Disinfection Miox Purifier, marketed by MSR www.miox.com www.msrcorp.com/filters/pump_free.asp See Appendix A for more information on this product, which uses salt and an electric current from camera batteries to generate chlorine dioxide, free chlorine species, and perhaps other disinfectants such as ozone. Passing a current through a simple brine salt solution generates free available chlorine, as well as other “mixed species” disinfectants that have been demonstrated effective against bacteria, viruses, and bacterial spores.197 The process is well described and can be used on both large and small scale. Chlorine dioxide and ozone have not been detected in finished water treated with the Miox mixed-oxidant solutions using classic analytical methods. This is likely due to rapid transformation of the generated oxidant constituents to other forms of oxidants. However, the resulting solution has greater disinfectant ability than a simple solution of sodium hypochlorite and has even been demonstrated to inactivate Cryptosporidium, suggesting that chlorine dioxide is among the chemicals generated.239 Additional testing information is available on the Miox website. Silver MicroPur Forte Tablets from Katadyn Available from FirstWater www.firstwater.info/noflash/pdct_ prsnel_chem.html Widely available in Europe but not marketed in the United States, these tablets contain silver and sodium hypochlorite. The chlorine kills viruses, bacteria, and Giardia. The silver adds to the disinfection capacity, and it prevents recontamination if water is stored for up to 6 months. Contact time is 20 to 120 minutes, depending on temperature of water. Shelf life is 2 years when stored in cool, dry conditions. Available as tablets or liquid.

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MicroPur from Katadyn This product releases silver ions. Available in two sizes of tablets (for 1 quart or 5 quarts), liquid (10 drops/gal), or crystals for treating larger quantities of water. Comments Although it has proven antibacterial effects, silver tablets are not licensed as a water purifier in the United States; however, they are widely used in Europe for this purpose. In addition to poorly documented effects on some types of microorganisms, there is difficulty controlling the residual concentration and concern over chronic effects. This product makes no claims for viruses and protozoa, because concentrations may not be adequate to kill these organisms. Silver has the advantage of having no taste, color, or smell. It has been approved by the EPA to be marketed in the United States as a “water preservative” to maintain bacteria-free water for up to 6 months. Miscellaneous Products The following products cannot be recommended due to insufficient effectiveness data: Traveler’s Friend (Nutrabiotic) Description Extract from citrus seeds in 10-mL plastic dropper bottle; size: 1 × 2 inches; weight: 1 oz; capacity: approximately 20 quarts. Price: $6 Claims “All natural treatment for drinking water.” Nontoxic, noncorrosive, proven effective as disinfectant for bacteria, viruses, protozoa. Recommended dose (drops/qt): 5 to 10 for filtered water, 10 to 15 for ice water, 10 to 20 for tap water, 15 to 25 for untreated water. Allow 30 minutes contact time. Comments Citrus extract is known to have some bacteriostatic effect. This product was introduced in the health food market and is now looking for a broader market. Company data from independent laboratories support bactericidal and virucidal effects. However, protozoal tests were done with trophozoites, not cysts. The data have gaps, and too much of the marketing is testimonial to give a recommendation now. The chemical species or compound responsible for disinfection needs to be identified, then dose-time disinfection values and need to be experimentally established for various microorganisms. Aerobic Oxygen Aerobic Oxygen was initially introduced into the health food market but is now being offered to the general travel market. It is advertised not only as a water disinfectant but also for nearly miraculous qualities ranging from strengthening the immune system and energizing the body to curing headaches and tropical fish diseases. Company literature implies that the active disinfectant is chlorine dioxide, ozone, and free oxygen radicals, but this is not chemically feasible. Company-sponsored testing demonstrates activity against bacteria and viruses but not against cysts. No dose-time response has been developed to compare the product against other disinfectants. It cannot be recommended without further data. The references for this chapter can be found on the accompanying DVD-ROM.

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62

Infectious Diarrhea from Wilderness and Foreign Travel Javier A. Adachi, Howard D. Backer, and Herbert L. DuPont

Acute infectious diarrhea is one of the most common and significant medical problems in any population, second only to acute upper respiratory diseases.132,327 Worldwide, diarrheal diseases were reported to cause nearly 1 billion episodes of illness in 1996,76,95,96,287 with at least 20 million annual deaths.220,327 The rates of illness among children in developing areas of the world range from 5 to 15 bouts per child per year, with diarrhea being the most important cause of morbidity and mortality in many regions. Readily available oral rehydration solutions prevent great numbers of dehydration-associated deaths related to acute diarrhea, especially in developing areas, but invasive bacterial enterocolitis (caused by Shigella species and Campylobacter jejuni/coli), persistent diarrhea (defined as illness lasting 14 days or longer), malnutrition, and increased susceptibility to other infections still cause significant morbidity and mortality.76,131,220,287 In the United States, specific groups with diarrhea rates similar to those in the developing world include travelers, homosexual men, non–toilet-trained toddlers in daycare centers, and mentally impaired residents in custodial institutions.95,115,131,132 This chapter provides information to help decrease exposure to risk factors and enteric pathogens, thus helping to reduce the chance of acquiring diarrheal illness. The clinical features of acute diarrheal illnesses often do not permit differentiation of the specific etiologic agent, but fortunately, the majority of these infections do not require specific treatment.7,76,95,96,132 A clinical approach to self-therapy is formulated that is likely to minimize the complications and suffering caused by these illnesses. For the purpose of this discussion, traveler includes business and pleasure travelers as well as wilderness venturers.


GENERAL PRINCIPLES OF ENTERIC DISEASE

Epidemiology Transmission. Fecal–oral contamination, through ingestion of contaminated water and food, is the usual route of transmission of the enteric pathogens causing acute infectious diarrhea. Whether food or water is the more important origin depends mainly on the location and the precautions taken. The majority of pathogens that cause travelers’ diarrhea or wildernessacquired diarrhea can be either food-borne or water-borne;

however, waterborne pathogens from drinking untreated surface water or from an inadvertent ingestion during water recreational activity probably account for most infectious diarrhea acquired in the U.S. wilderness.131,196,199,209 Avoidance of all these pathogens requires proper sanitation and water disinfection. Person-to-person transmission is seen with pathogens that do not require a large infectious dose, such as Shigella species, the hepatitis A virus, Giardia, and noroviruses. These infections are most common in populations exposed to high levels of pathogens, so prevention includes adequate hand-washing and personal hygiene76,95,96 (Table 62-1). Other, less common routes of fecal–oral transmission are through aerosols (some viruses), contaminated hands or surfaces, and sexual activity.

Location. In several areas of Africa, Asia, and Latin America where satisfactory sanitation is lacking, diarrhea is still the leading cause of infant morbidity and mortality. Good sanitation is related to a much lower incidence of infectious diarrhea in industrialized areas of the world. Travelers to foreign countries and wilderness areas often leave behind sanitation in the form of flush toilets and safe tap water, as well as proximity to advanced medical care. Similarly inadequate hygiene conditions are also found in other settings. Outbreaks of infectious diarrhea in daycare centers among non–toilet-trained toddlers are associated with Giardia lamblia, Shigella, Campylobacter jejuni/coli, and Cryptosporidium, which have a small infectious dose. Hospitals, especially intensive care units and pediatric wards, institutions for mentally handicapped patients, and nursing homes are also locations with high incidences of diarrheal diseases. Clostridium difficile, Salmonella species, rotavirus, and enteropathogenic Escherichia coli (EPEC) are the most common etiologic agents reported96,131,169,249,317 (see Table 62-1). Antimicrobial Therapy. C. difficile–associated diarrhea is frequently related to recent use of an antimicrobial agent (or a cytotoxic agent), usually during the 2 to 4 weeks before the beginning of the diarrheal illness.51,106,171 Age. In developing areas of the world, children younger than 5 years have higher morbidity and mortality rates related to dehydration superimposed on malnutrition; they may experi-

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TABLE 62-1. Epidemiologic Associations with Enteropathogens AGENTS Bacteria Enteropathogenic Escherichia coli Enterotoxigenic E. coli Enteroinvasive E. coli Shiga-toxin producing E. coli Enteroaggregative E. coli Nontyphoid Salmonella Salmonella typhi Shigella species Campylobacter species Vibrio cholerae Yersinia enterocolitica Aeromonas species Plesiomonas shigelloides Clostridium difficile Viruses Norovirus Rotavirus Hepatitis A Protozoa Giardia lamblia Entamoeba histolytica Cryptosporidium parvum Isospora belli Cyclospora cayetanensis Microsporidia Balantidium coli Sarcocystis Blastocystis hominis

WATERBORNE

CHILDREN*

HOSPITALIZED/ INSTITUTIONALIZED

HOMOSEXUALITY

IMMUNOCOMPROMISED

ZOONOTIC

−

+

+

∼−

−

−

+ − +

− − −

− − −

− − −

− − −

− − −

−

+

−

−

+

−

− + − + + − + − −

− − + + − − − − −

+ − − − − − − − +

− − + + − − − − −

− − − − − − − − −

+ − − + − + − − −

+ + +

− + −

− + −

− − −

− − −

− − −

+ + +

+ − −

− − −

− − +

+ − +

+ + +

− +

− −

− −

− −

+ +

− −

− − − −

− − − −

− − − −

− − − −

+ − − −

− + + −

*In industrialized areas or daycare centers. +, association; −, no association or unknown association.

ence 5 to 15 episodes of diarrhea per year. The enteropathogens more common in infectious diarrhea during childhood are rotavirus, EPEC, enterotoxic E. coli (ETEC), enteroadherent E. coli (EAEC), C. jejuni/coli, and G. lamblia (see Table 62-1). Residents in industrialized countries, such as the United States, have only one to two bouts of diarrhea per person per year, with no differences between age groups, although complications, including death, are more common in older adults.76,95,115

Reservoirs of Infection. Organisms are shed in the stools during asymptomatic and symptomatic infection and for a period after the illness. Long-term shedding or chronic carrier states are reported only with typhoid fever, amebiasis, giardiasis, cryptosporidiosis, and EAEC infection. These cases may act as reservoirs for spreading infection, even in areas with low risk for infection from contaminated water. A few enteric pathogens that are zoonotic (having animal reservoirs) can increase the risk for certain persons (e.g., veterinarians, field biologists) and account for wilderness-acquired infections. These zoonotic organisms include Salmonella, Yersinia, Campylobacter, Giardia, Balantidium coli, Entamoeba, Sarcocystis, and Cryptosporidium76,95 (see Table 62-1). Incubation Period. Food intoxication, caused by ingestion of preformed toxins from Staphylococcus aureus or Bacillus

cereus, usually has a short incubation period (2 to 7 hours), and often a common source is found to have affected multiple persons.14,93,260 An outbreak by any enteropathogen that must first infect the intestine usually has an incubation period of 8 or more hours.

Immunocompromised Status. Immunocompromised patients, including those infected with human immunodeficiency virus (HIV), are prone to acquire infection by a wide variety of enteropathogens, to develop infectious diarrhea, and to experience relapses or reinfections. Patients with HIV and advanced acquired immunodeficiency syndrome (AIDS) often experience malabsorption and chronic diarrhea because of changes in intestinal function secondary to HIV or because of reduced immunity that allows coinfection with other enteropathogens. The agents responsible for diarrheal diseases in patients with HIV are common enteric agents, Mycobacterium aviumintracellulare complex, Cryptosporidium, Giardia, Isospora, Cyclospora, microsporidia, cytomegalovirus, herpes simplex virus, and HIV. Treatment of patients with HIV with highly active antiretroviral therapy and managing the enteric infection are associated with improved symptomatology and decreased rates of infection.

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TABLE 62-2. Enteropathogens Found in Tropical and Wilderness Travel AGENTS Bacteria Enteropathogenic Escherichia coli Enterotoxigenic E. coli Enteroinvasive E. coli Shiga toxin–producing E. coli Enteroaggregative E. coli Salmonella species Shigella species Campylobacter species Vibrio cholerae Yersinia enterocolitica Aeromonas species Plesiomonas shigelloides Viruses Norovirus Rotavirus Hepatitis A virus Protozoa Giardia lamblia Entamoeba histolytica Cryptosporidium parvum Isospora belli Cyclospora cayetanensis Microsporidia Balantidium coli Sarcocystis Blastocystis hominis

TRAVEL TO DEVELOPING TROPICAL REGIONS

WILDERNESS TRAVEL IN INDUSTRIALIZED REGIONS

Rarely Yes Rarely Rarely Yes Yes Yes Yes Limited Rare Yes Yes

Rarely Rarely Rarely Rarely Rarely Yes Yes Yes Not currently Limited Yes Rarely

Yes Yes Yes

Yes Rarely Yes

Yes Yes Yes Limited Limited Limited Limited Limited Limited

Yes Rarely Yes Rarely Rarely Rarely Rarely Rarely Rarely

Etiology Enteropathogens, including bacteria, viruses, and protozoa, are the most common etiologic agents of infectious diarrhea. Fungal agents have been reported rarely. Table 62-2 lists the etiologic agents often associated with travel to developing tropical areas, or with wilderness travel in an industrialized region. Food-borne illness may consist of food “poisoning” or food “infection.” In food poisoning, an intoxication results when toxins produced by bacteria are found in food in sufficient concentrations to produce symptoms. The major forms of intoxication result from S. aureus and B. cereus. A rare cause of food poisoning that results in paralysis is botulism, caused when the neurotoxin of Clostridium botulinum is ingested. Other food-borne pathogens are viruses, including rotavirus and small round viruses (norovirus, astrovirus), and intestinal protozoal agents, including Giardia, Entamoeba histolytica, and Cryptosporidium.

Pathophysiology Three intestinal mechanisms lead to acute diarrhea. The most common pathophysiologic mechanism in acute infectious diarrhea is alteration of fluid and electrolyte movement from the serosal to the mucosal surface of the gut (secretory diarrhea). This alteration may occur as a result of cyclic nucleotide stimulation (as a second messenger) or by an inflammatory process that releases cytokines. The second mechanism, malabsorption or the presence of nonabsorbed substances in the lumen of the bowel, and the third, acceleration of intestinal motility,

are more important in chronic forms of infectious and noninfectious diarrhea, such as tropical and nontropical sprue, Whipple’s disease, scleroderma, malabsorption, irritable bowel syndrome, and inflammatory bowel disease. Table 62-3 shows the virulence factors of the most important enteric pathogens related to infectious diarrhea.72,95 In general, enteropathogens cause diarrhea by the first mechanism and can be subdivided into noninvasive and invasive groups. Noninvasive microorganisms primarily colonize the proximal small bowel and cause secretory diarrhea without disruption of the mucosal surface. The unformed stools are usually voluminous and rarely bloody, and high fever is unusual. The common pathogens in this group include Vibrio cholerae, ETEC, preformed enterotoxins, noroviruses, rotavirus, Giardia, and Cryptosporidium. Dehydration is the major complication, especially in the extremes of age, and without adequate therapy it can be followed by renal insufficiency. Invasive pathogens, on the other hand, involve the distal ileum and colon, damaging the mucosa and eliciting an inflammatory response. Stools are typically liquid, the volume is typically small, and they may contain blood and many leukocytes. The common microorganisms in this group are Shigella, Salmonella, enteroinvasive E. coli (EIEC), Shiga-toxin–producing E. coli (STEC), Yersinia enterocolitica, C. jejuni/coli, Aeromonas, Vibrio parahaemolyticus, and E. histolytica. Complications include dehydration and systemic involvement, especially in children with malnutrition.72,73

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TABLE 62-3. Bacterial Enteropathogens:Virulence Properties and Distribution PATHOGEN Vibrio cholerae Vibrio parahemolyticus

VIRULENCE PROPERTIES

DISTRIBUTION

Enteroinvasive E. coli

Heat-labile enterotoxin Invasiveness (?), enterotoxin, hemolytic toxin Enteroadherence, type III secretory system Heat-stable and heat-labile enterotoxins, colonization factor antigens Shigella-like invasiveness

Shiga toxin–producing E. coli Enteroaggregative E. coli Salmonella species Shigella species Campylobacter jejuni Aeromonas species Yersinia enterocolitica Clostridium difficile Clostridium perfringens Bacillus cereus Staphylococcus aureus

Shiga-like toxin Enteroadherence Cholera-like toxin, invasiveness Shiga-like toxin, invasiveness Cholera-like toxin, invasiveness Hemolysin, cytotoxin, enterotoxin Heat-stable enterotoxin, invasiveness Cytotoxins A and B Preformed toxin Preformed toxin Preformed toxins

Enteropathogenic Escherichia coli Enterotoxigenic E. coli


TRAVELERS’ DIARRHEA Travelers’ diarrhea (TD) is the most important travel-related illness in terms of frequency and economic impact. Point of origin, destination, and host factors are the main risk determinants.95,249 International travel is more often associated with enteric infection and diarrhea, particularly when the destination is a developing tropical region, but the same infections can be contracted domestically. The 2% to 4% rate of diarrhea for people who take short-term trips to low-endemic areas (e.g., United States, Canada, northwestern Europe, Australia, Japan) may be related to more frequent consumption of food in public restaurants, increased intake of alcohol, or stress. This rate of diarrhea increases to about 10% for travelers from these lowendemic areas to northern Mediterranean areas, China, Russia, and some Caribbean islands. This incidence increases to as high as 40% to 50% for short-term travelers from low-risk countries to high-risk countries (developing tropical and subtropical regions of Latin America, Southeast Asia, or Africa). More than 25 million persons travel each year from these industrialized countries to high-risk areas, resulting in over 7 million travelers with diarrhea.76,95,96 Multiple episodes of diarrhea may occur on the same trip.249 Attack rates remain high for up to 1 year,76,95 then decrease, but not to the levels of local inhabitants. Immunity to ETEC infection, either asymptomatic or symptomatic, occurs after repeated or chronic exposure,221 which supports the feasibility of developing a vaccine. TD is a syndrome, not a specific disease.76,95,249 Although any water-borne or food-borne enteropathogen may cause TD, bacteria are the most common etiologic agents among persons traveling to high-risk areas. The bacterial flora of the bowel changes rapidly after arrival in a country with high rates of TD.3 At least 15% of travelers remain asymptomatic despite the occurrence of infection by pathogenic organisms, including ETEC and Shigella. However, most infected patients become ill.

Endemic areas in Asia, Africa, and Latin America Endemic areas in Asia and Latin America Infants, worldwide Developing countries, tropical areas, infants, travelers Worldwide, endemic in South America and eastern Europe Beef, other vehicles in industrialized areas Infants, worldwide Worldwide Worldwide Worldwide Worldwide, especially Thailand, Australia, Canada Worldwide, especially Canada, Scandinavia, South Africa Worldwide Worldwide Worldwide Worldwide

Definition TD refers to an illness contracted while traveling, although in 15% of sufferers symptoms begin after the return home.45 Most clinical studies define TD as the passage of three or more unformed stools in a 24-hour period in association with one or more enteric symptoms, such as abdominal cramps; fever; fecal urgency; tenesmus; passage of bloody, mucoid stools; nausea; and vomiting.76,95,249

Etiology Because the incidence of TD reflects in part the extent of environmental contamination with feces, the etiologic agents are pathogens causing illness in local children. The list of etiologic agents changes as laboratory techniques identify new enteropathogens (Table 62-4). Twenty years ago, specific pathogens were found in only 20% of cases.181,182 Currently, etiologic agents can be identified in up to 80% of TD episodes.95,249 In most studies, however, causative pathogens are not identified in 20% to 40% of cases. In most of these cases, antimicrobial therapy shortens illness, suggesting that this subset of diarrhea is caused by undetected bacterial pathogens.37,79,99,119 Overall, the major etiologic agents and their frequency of isolation are remarkably similar when one region of the world is compared with another. ETEC has proved to be the most common cause of TD worldwide,10,61,221,249,284 accounting for about one third to one half of cases. Since the previous edition of this book, EAEC has been identified as the second most common bacterial cause of TD, causing up to 30% of TD cases in some areas of the world.5,156,169,243,317 One study has shown that the source of both types of E. coli is food. Viable ETEC and EAEC were found in hot sauces on the table in popular restaurants in Guadalajara, Mexico.6 Shigella and Campylobacter species cause around 20% of illness. Other causes of TD include Salmonella (4% to 5% of cases), Vibrio, Aeromonas, Plesiomonas, viruses

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TABLE 62-4. Major Pathogens in Travelers’ Diarrhea (Travel to Developing Tropical Regions) AGENT

FREQUENCY (%)

Bacteria Enterotoxigenic Escherichia coli Enteroaggregative E. coli Salmonella species Shigella species Campylobacter jejuni Aeromonas species Plesiomonas shigelloides Other Viruses Rotavirus Norovirus Protozoa Giardia lamblia Entamoeba histolytica Cryptosporidium parvum Unknown

50–80 5–50 5–30 1–15 1–15 1–30 0–10 0–5 0–5 0–20 0–20 1–20 1–5 0–5 0–5 0–5 10–40

TABLE 62-5. Pathophysiologic Syndromes in Diarrheal Disease SYNDROME Acute watery diarrhea Febrile dysentery

Vomiting (as predominant symptom) Persistent diarrhea (>14 days) Chronic diarrhea (>30 days)

AGENT Any agent, especially with toxin-mediated diseases (e.g., enterotoxigenic Escherichia coli, Vibrio cholerae) Shigella, Campylobacter jejuni, Salmonella, enteroinvasive E. coli, Aeromonas species, Vibrio species, Yersinia enterocolitica, Entamoeba histolytica, inflammatory bowel disease Viral agents, preformed toxins of Staphylococcus aureus or Bacillus cereus Protozoa, small bowel bacterial overgrowth, inflammatory or invasive enteropathogens (Shigella, enteroaggregative E. coli) Small bowel injury, inflammatory bowel disease, irritable bowel syndrome (postinfectious), Brainerd diarrhea

(10%),44 and parasites (2% to 4%). Specific pathogens may predominate at a particular time or location. ETEC and EAEC are more common in semitropical countries, including Mexico, Guatemala, Goa, Jamaica, Kenya, and Morocco, and during rainy summer seasons, and they occur less often in drier winters.5,211,243,317

Clinical Syndromes Table 62-5 outlines the major syndromes in patients with enteric infection. The typical clinical syndrome experienced by travelers with diarrhea secondary to the major infectious causes (e.g., ETEC) begins abruptly with watery diarrhea and abdominal cramping. Most cases are mild, consisting of passage of one to two unformed stools per day and associated with symptoms

that are tolerable and do not interfere with normal activities. Approximately 30% of affected persons experience moderately severe illness, with three to five unformed stools per day and distressing symptoms that force a change in activities or itinerary. Only 10% to 20% of persons with TD experience severe illness with more than five unformed stools passed per day, incapacitating symptoms that force confinement to bed, or any number of unformed stools with concomitant fever and dysentery.95,249 Only 4% of persons with TD consult a local physician, and less than 1% are admitted to a local hospital while traveling. Approximately one third of travelers are confined to bed or need to alter their travel plans when a diarrheal illness develops. Although the average duration of diarrhea is 3 to 4 days, 50% of cases resolve within 48 hours, 8% to 15% last longer than 1 week, and 1% to 3% last 1 month or longer. Recently, several studies have shown that infectious diarrhea might trigger irritable bowel syndrome. Up to 10% of subjects with TD developed persistent or chronic gastrointestinal (GI) symptoms.159,236,244,318 TD is rarely life-threatening.

Clinical Examination The etiologic organism of TD cannot be reliably identified on the basis of clinical manifestations alone, because illnesses caused by different microorganisms share similar clinical features.65,95,225,249,295 Although noninvasive organisms rarely cause dysentery, invasive organisms often cause watery diarrhea without dysentery, or a sequential illness beginning with watery diarrhea and progressing to bloody dysentery. If multiple people acquire the illness shortly after eating a shared meal, food poisoning caused by ingestion of preformed toxins in food should be suspected, especially if the illness has a short incubation period (8 hours or less), predominant vomiting, and resolution within 24 hours. Investigators have studied whether clinical factors can reliably be used to predict which persons will have a positive stool culture.65,225,295 Bacterial pathogens are suspected when the sufferer has a large number (more than six) of stools per day, has a fever, and has had the ailment for more than 24 hours but less than 1 week. Regardless of the clinical similarities of enteropathogens causing TD, certain differences exist, with distinct clinical findings. When symptoms last more than 1 to 2 weeks, a protozoal etiology, such as Giardia, an amoeba, or Cryptosporidium, is suggested.

Dehydration. An important part of the initial assessment is to measure the level of hydration, which includes a determination of vital signs, orthostatic pulse and blood pressure, mental status, skin turgor, hydration of mucous membranes, and urine output. Dehydration is most common in pediatric and elder populations. Fever. Fever is a reaction to an intestinal inflammatory process. High fever suggests a pathogen has invaded the intestinal mucosa, and classically this has meant bacterial enteropathogens such as Shigella, Salmonella, and C. jejuni/coli. Fever can also be produced by strains of EIEC, V. parahaemolyticus, Aeromonas, C. difficile, and viral pathogens. Vomiting. Vomiting as the predominant symptom suggests food intoxication secondary to enterotoxin produced by S. aureus, B. cereus, or Clostridium perfringens, or gastroenteritis

Chapter 62: Infectious Diarrhea from Wilderness and Foreign Travel

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TABLE 62-6. Indications for Laboratory Testing in Diarrheal Diseases, and Possible Diagnosis LABORATORY TEST Fecal leukocytes or fecal lactoferrin Stool culture Blood culture Parasite examination Parasite enzyme immunoassay Amebic serology Rotavirus antigen Clostridium difficile toxin

INDICATION

DIAGNOSIS/AGENT

Moderate to severe cases

Diffuse colonic inflammation, invasive enteropathogen

Moderate to severe diarrhea, fever, persistent diarrhea, fecal leukocytes or lactoferrin (+), gay men Enteric fever, sepsis

Any bacterial enteric pathogen

Persistent diarrhea, travel to specific areas, daycare centers, gay men Persistent diarrhea, travel to specific areas, daycare centers, gay men Persistent diarrhea, liver abscess Hospitalized infants (14 days)

Vomiting, minimal diarrhea Diarrhea in pregnant women

RECOMMENDATIONS* Administer oral fluids and crackers (e.g., Saltines) Administer symptomatic treatment with loperamide or bismuth subsalicylate; or antimicrobial drugs† plus loperamide after passage of first unformed stool Perform stool culture and fecal leukocyte or lactoferrin test; administer antimicrobial drugs† plus loperamide after passage of first unformed stool Perform stool culture and fecal leukocyte or lactoferrin test; administer antimicrobial drugs†; no loperamide Perform stool culture and parasite examination; consider empiric trial with metronidazole Administer bismuth subsalicylate Evaluation as above; administer fluids and electrolytes; fluoroquinolones not recommended; consider attapulgite; consider azithromycin or rifaximin; no fluoroquinolones

*Treatment may be started during travel in absence of facilities for evaluation. † Fluoroquinolones (norfloxacin, ciprofloxacin, or levofloxacin), azithromycin, or rifaximin recommended in adults.

TABLE 62-8. Nonspecific Drugs for Therapy in Adults AGENT Attapulgite

Loperamide Bismuth subsalicylate

THERAPEUTIC DOSAGE Initially 3 g, then 3 g after each loose stool or every 2 hours (not to exceed 9 g/day); should be safe during pregnancy and childhood. (Available in 600-mg tabs, or liquid 600 mg/tsp) Initially 4 mg, then 2 mg after each loose stool (not to exceed 8 to 16 mg/day); do not use in dysenteric diarrhea. 30 mL or two 262-mg tablets every 30 min for 8 doses; may repeat on day 2.

diarrhea. Persistent diarrhea is defined as illness lasting 14 days or longer, whereas diarrhea is considered chronic when the illness has lasted 30 days or longer.74,95,249 The etiology of persistent or chronic diarrhea often differs from that of acute diarrhea. Important causes of persistent diarrhea include (1) protozoal parasitic agents (Giardia, Cryptosporidium,

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Cyclospora, and E. histolytica), (2) bacterial infection (Salmonella, Shigella, Campylobacter, and Y. enterocolitica), (3) lactase deficiency induced by a small bowel pathogen (Giardia, rotavirus, or norovirus), and (4) a small bowel bacterial overgrowth syndrome secondary to small bowel motility inhibition (as a result of enteric infection) or secondary to antimicrobial use. Occasionally, other parasitic enteric infections can cause more persistent illness. These include Strongyloides stercoralis, Trichuris trichiura, and severe infection by Necator americanus or Ancylostoma duodenale. In rare cases, more protracted diarrhea may be a prominent symptom in persons with schistosomiasis, Plasmodium falciparum malaria, leishmaniasis, or African trypanosomiasis.74,95,231,249 When chronic diarrhea occurs, the following possibilities should also be considered: • Postinfectious irritable bowel syndrome has recently been noted by a number of authors.159,236,244,291,318 Approximately 10% of travelers who develop TD could develop chronic gastrointestinal symptoms, either completely new or a reactivation of a previous disorder. An underlying condition such as inflammatory bowel disease, irritable bowel syndrome, or celiac sprue may worsen after an episode of acute enteritis. • After eradication of microbial pathogens, bowel habits may not return to normal for several weeks. Postdysenteric colitis resembling ulcerative colitis occasionally follows infection with invasive pathogens, especially infection caused by E. histolytica. This could represent slow repair of damage to the intestinal mucosa. • Chronic parasitic infection with Giardia, Cryptosporidium, Isospora, Cyclospora, microsporidia, or Entamoeba may produce a chronic intestinal process and produce persistent diarrhea. Postinfective malabsorption can persist for weeks to months after acute diarrhea; it is especially common after giardiasis.74,96,249 • A poorly defined condition, tropical sprue, may explain prolonged diarrhea in a traveler. Onset usually follows an episode of acute enteritis and is associated with substandard hygiene and longer stays. The cause may involve small bowel bacterial overgrowth, because small bowel incubation may yield a heavy growth of bacteria, and patients often respond to antimicrobial therapy. • Brainerd diarrhea, named after a community outbreak in Brainerd, Minnesota, may follow consumption of raw (unpasteurized) milk239 or untreated water.246 There is no diagnostic test or therapy, and the diagnosis is suspected on the basis of the epidemiologic history (exposure to unpasteurized milk or untreated water just before onset of illness). Evaluation of persistent or chronic diarrhea in travelers should begin with diagnostic tests for conventional bacterial pathogens in stools and at least three sequential evaluations for parasites in stools. Dietary modification in all cases should include avoidance of lactose. Treatment should be specific, following the results of the microbiologic tests. Because most of these chronic forms of diarrhea are self-limiting, it is unwise to keep treating these patients with multiple antibiotics, which only alters the gut ecology and encourages diarrhea. An empiric trial with metronidazole is an option if all tests are negative (see Table 62-7). If stools contain leukocytes, sigmoidoscopy or colonoscopy should be performed, along with empiric treatment for Shigella or Campylobacter infection. If there are no leukocytes, duodenal mucus should be examined for G. lamblia, followed by empirical treatment for Giardia, if metronidazole has

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not already been given. The next steps are tests for malabsorption and biopsy of the small bowel mucosa.

Treatment In all cases of diarrhea, fluid and electrolyte replacement should be the primary therapy. Outpatient treatment with instructions for oral rehydration can be used in the vast majority of adults and children. Significant dehydration from diarrhea in travelers is unusual. Treatment with intravenous (IV) fluids is indicated for the following: • Patients with hemodynamic decompensation (hypotension) • Inability to retain oral fluids • Systemic compromise (high fever and toxicity) • Moderate toxicity or dehydration and a severe underlying disease • Patients at extremes of age Some patients may benefit from symptomatic therapy, and others may receive empiric antimicrobial therapy (see Table 62-7). The main goal of the therapy, such as an antimotility drug or an antimicrobial agent, is to attenuate the severity and duration of the diarrhea and concomitant symptoms.

Diet and Lifestyle. Supplemental nutrition is beneficial (essential in undernourished populations) and can be given as soon as fluid deficit losses are replaced, usually after the first 4 hours. During acute diarrheal disease, the intestinal tract cannot process complex dietary products, so patients are often told to avoid solid foods. As stooling decreases and appetite improves, staple foods, such as cereals, bananas, crackers, toasts, lentils, potatoes, and other cooked vegetables, are well tolerated and can be gradually added to the diet to facilitate enterocyte renewal, with progression to white meats, fruits, and vegetables. Dairy products and red meats are recommended only after diarrhea has resolved, usually after 2 to 3 days. Only foods and drinks that prolong diarrhea or increase intestinal motility, such as those that contain lactose, caffeine, alcohol, high fiber, and fats, should be avoided. Breastfeeding of infants should be continued or should be resumed as soon as possible.71,76,95,96,296 Patients with TD should avoid excessive physical therapy to reduce the risk of dehydration. Fluid Treatment. The major cause of morbidity and mortality from acute diarrheal disease is depletion of body water and electrolytes. Rehydration is an essential part of therapy, especially in the extremes of age and during pregnancy. Most patients with TD do not become dehydrated, and hydration can be maintained by ingesting fluids, such as sodas, juices, soup, and potable water, in conjunction with a source of electrolytes (e.g., salted crackers).46,76,95,96 The most significant advance in the therapy of diarrhea in the past 50 years has been development of the oral rehydration concept. Oral rehydration solution (ORS) was first developed for treatment of cholera and has saved countless lives, primarily those of children. ORS precludes extensive use of scarce and expensive IV fluids in developing countries; its use is the cornerstone of the World Health Organization (WHO) program to combat diarrheal diseases.46,76,95,96,132 The discovery that glucose-enhanced intestinal absorption of sodium remains intact despite active diarrhea or vomiting was the key to development of ORS.211,273 Other electrolytes are also absorbed nonselectively when ORS is administered.

Watery diarrhea, often caused by release of an enterotoxin, has an electrolyte composition similar to that of plasma, varying somewhat with the type of infection and age of the patient. The formula packaged and promoted by the WHO and the United Nations International Children’s Emergency Fund (UNICEF) contains powder to be mixed with 1 L of disinfected water, with the following resultant concentrations: sodium, 90 mEq; potassium, 20 mEq; chloride, 80 mEq; bicarbonate, 30 mEq; and glucose, 111 mmol. Newer formulations use trisodium citrate instead of sodium bicarbonate, and complex carbohydrates instead of glucose. Cereal-based products are also available. Although this concentration of electrolytes is ideal for managing the purging diarrhea associated with cholera and other dehydrating forms of diarrhea, most TD can be adequately managed with readily available soft and sports drinks, fruit juices, or salt solutions, taken with salted crackers and the foods listed earlier.46,76,96 Fluid status in the field must be guided by physical signs related to hydration, including pulse, mucous membranes, skin turgor, and urine output. Urine color and volume are excellent measures. For travelers in the wilderness or tropics, fluid replacement must equal basic needs plus volume of diarrhea plus estimated sweat loss.

Nonspecific Therapy. Symptomatic medications are useful for treatment of mild to moderate diarrhea, as they decrease symptoms and allow patients to return more quickly to normal activities (see Tables 62-7 and 62-8). Nonantibiotic therapies that may be used in addition to fluids are best classified by their effects on pathophysiologic mechanisms. Probiotics. Lactobacillus preparations and yogurt are safe, but evidence is insufficient to establish their value in the therapy of acute diarrhea.46,76,96,142,309 Adsorbents. Adsorbent agents bind nonspecifically to water and other intraluminal material, including bacteria and toxins, and potentially to other medications such as antibiotics. The most common medication in this group is attapulgite (see Table 62-8 for dosages), a nonabsorbable magnesium aluminum silicate that is more active than the combination of kaolin and pectin.37 By adsorbing water, these agents give stools more form or consistency but do not decrease stool frequency, cramps, or duration of illness. They are reliable and should be safe in all persons, although adsorbents are not approved for use in young infants and pregnant women.270 Antimotility Drugs. Narcotic analogs related to opiates are the major antimotility drugs. In addition to slowing intestinal motility, these drugs alter water and electrolyte transport, probably affecting both secretion and absorption.46,76,95,96 Compared with placebo, antimotility drugs reduce the number of stools passed and the duration of illness by about 80% during their administration.77,83 The most frequently used product is loperamide (Imodium), 4 mg initially, followed by 2 mg after each unformed stool, not to exceed 8 to 16 mg/day. Loperamide also has a weak antisecretory effect through inhibition of intestinal calmodulin. Diphenoxylate with atropine (Lomotil) is less expensive than loperamide but has greater central opiate effects, a danger in case of accidental overdose by a child, and more side effects without antidiarrheal benefits because of the atropine, which is

Chapter 62: Infectious Diarrhea from Wilderness and Foreign Travel added only to prevent overdoses. Tincture of opium or paregoric opium preparations are rapidly and equally effective and offer a modest relief of symptoms. Antimotility drugs should never be used alone in patients who have dysenteric or febrile diarrhea, because inhibition of gut motility may facilitate intestinal infection by invasive bacterial enteropathogens.85 However, this theoretically deleterious effect does not appear to be an issue when loperamide is used concurrently with an effective antimicrobial agent.97,99,300 Antimotility drugs should not be given to children younger than 3 years because of the danger of central nervous system (CNS) depression. They are recommended for only up to 48 hours in acute diarrhea.

Antisecretory Drugs. Because increased secretion of water and electrolytes is the major physiologic derangement in acute watery diarrhea, therapy aimed at this effect is appealing. Although aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit secretion, their usefulness is limited, primarily because of mucosal toxicity.37,95 The salicylate moiety of bismuth subsalicylate reduces the number of stools passed and the duration of diarrhea by about 50%, primarily by blocking the effect of the enterotoxin on the intestinal mucosa.83 Bismuth subsalicylate also has antimicrobial and anti-inflammatory properties. New compounds are being developed that have antisecretory properties without motility effects.80 Antimicrobial Therapy. Although most enteric infections do not require antibiotics, empiric antimicrobial therapy is indicated in acute TD and febrile, dysenteric illness because of the high frequency of bacteria as etiologic agents.96 Travelers with acute diarrhea and mild symptomatology usually do not need empiric antimicrobial therapy and could be treated with oral fluids and saltine crackers. Those travelers with acute diarrhea and moderate symptoms (serious enough to change their itinerary) could be treated with antimicrobial empiric therapy or symptomatic therapy with loperamide or bismuth subsalicylate. Finally, those travelers with severe and incapacitating symptoms, or with dysentery, should be treated with empiric antimicrobial therapy immediately after the first passage of unformed stool (together with loperamide only if there is no evidence of dysentery) (see Table 62-7).7,37,76,96 Therapies for specific infections are discussed later in the relevant sections (Table 62-9). At times, treatment is indicated regardless of symptoms to prevent person-to-person spread (e.g., for food handlers, river guides, daycare workers) or to eradicate pathogenic strains and prevent conversion from asymptomatic to symptomatic illness (e.g., E. histolytica).36,258,292 Fluoroquinolones, azithromycin, and the newly approved rifaximin have adequate activity against most of the bacterial enteric pathogens to be considered useful for empiric therapy.7,81,88,293 Fluoroquinolones,7,95 including those evaluated in TD (norfloxacin, ciprofloxacin, ofloxacin, levofloxacin), represent the treatments of choice for TD when individuals are traveling to areas where resistance in Campylobacter strains is not prevalent or has not been determined. The main advantage of the quinolones is the high degree of in vitro activity against virtually all bacterial etiologic agents.79,99 Ciprofloxacin (500 mg twice a day) was as effective for treating TD as the combination of trimethoprim and sulfamethoxazole (TMP/SMX) in an area where trimethoprim resistance was unusual.99

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TABLE 62-9. Antimicrobial Therapy for Diarrhea in Adults DIAGNOSIS

RECOMMENDATION

Empiric Therapy in Bacteriologically Unconfirmed Disease Travelers’ diarrhea Rifaximin 200 mg tid or 400 mg bid for 3 days; norfloxacin 400 mg bid, ciprofloxacin 500 mg bid or levofloxacin 500 mg qd for 1 to 3 days; or azithromycin 500–1000 mg single dose Febrile and/or Norfloxacin 400 mg bid, ciprofloxacin dysenteric 500 mg bid, levofloxacin 500 mg qd for disease 3 days; or azithromycin 500– 1000 mg qd for 3 days Persistent diarrhea Consider a trial with metronidazole 250 mg qid for 7 days Oraganism-Specific Therapy in Laboratory-Confirmed Diarrhea Enterotoxigenic and Rifaximin 200 mg tid or 400 mg bid for enteroaggregative 3 days; ciprofloxacin 1000 mg single Escherichia coli dose or 500 mg bid for 1 to 3 days; diarrhea norfloxacin 400 mg bid or levofloxacin 500 mg qd for 1 to 3 days; or azithromycin 500–1000 mg single dose Cholera Ciprofloxacin 1000 mg single dose or 500 mg bid for 3 days; norfloxacin 400 mg bid or levofloxacin 500 mg qd for 3 days or doxycycline 300 mg single dose Salmonellosis Norfloxacin 400 mg bid, ciprofloxacin (typhoid fever 500 mg bid, or levofloxacin 500 mg qd or systemic for 7 to 10 days; in patients with infection) underlying disease or immunocompromised persons Salmonellosis Antimicrobial therapy controversial (see (intestinal text) nontyphoid salmonellosis without systemic infection) Shigellosis Norfloxacin 400 mg bid, ciprofloxacin 500 mg bid, levofloxacin 500 mg qd for 3 days Campylobacteriosis Erythromycin 500 mg qid for 5 days; azithromycin 500–1000 mg qd, norfloxacin 400 mg bid, ciprofloxacin 500 mg bid or levofloxacin 500 mg qd for 3 days Enteropathogenic Unclear if antimicrobial therapy is Escherichia coli necessary diarrhea Clostridium difficile Metronidazole 250 mg qid to 500 mg tid; colitis or vancomycin 125 mg qid for 7 to 14 days bid, twice daily; qd, daily; qid, four times daily; tid, three times daily.

TMP/SMX (160/800 mg) and trimethoprim (200 mg) twice a day for 5 days were equally effective in reducing the number of unformed stools, duration of illness, and abdominal symptoms (compared with placebo).84 Reduced duration of illness was reported in infections caused by ETEC or Shigella and also in the group without identifiable pathogens. Recently, TMP/SMX is less recommended because of increasing in vitro resistance to this antimicrobial agent in several areas of the world.7,122

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Azithromycin has been found as a good alternative for the treatment of acute TD. In a randomized, double-blind study, azithromycin (1000 mg, single dose) has been found to be as safe and effective as levofloxacin (500 mg, single dose) in the treatment of TD in Mexico.4 Although it remains to be tested in adequate clinical trials, 500 mg of azithromycin daily for 1 to 3 days should also be safe and effective. Rifaximin (200 mg three times a day) was approved in 2004 by the U.S. Food and Drug Administration (FDA) for the treatment of TD caused by noninvasive E. coli in patients older than 12 years. This approval was based on three randomized, double-blind clinical trials of rifaximin in travelers with diarrhea visiting Guatemala, Mexico, Jamaica, or Kenya81,88,293 that showed reduction in the duration of postenrollment diarrhea and a good safety profile, mainly because it is virtually nonabsorbed after oral administration.129,153,168 In the first study, rifaximin was shown to be more active than TMP/SMX,81 although not with statistical significance. In the second study, rifaximin was comparable to ciprofloxacin.88 In the last multicenter study, two different dosages of rifaximin were significantly better than placebo, with similar rates of nonserious adverse events.293 Azithromycin alone in pediatric dosages (10 mg/kg/day for first dose, follow by 5 mg/kg/day for second and third doses) is the treatment of choice in children. TMP/SMX plus a macrolide or nalidixic acid was previously recommended, but currently there is reported resistance to all these antimicrobial agents. Although fluoroquinolones are not yet approved to be used in children, ciprofloxacin has been used in children with cystic fibrosis without permanent cartilage damage to the joints. A short course of a fluoroquinolone or rifaximin may be considered to be safe and efficacious in children.189,269 Travelers to high-risk regions should carry with them an antibacterial drug for treatment of bacterial diarrhea. A drug such as loperamide may also be included for immediate relief of symptoms. If both drugs are employed in acute cases of TD, persons should be instructed to take the loperamide only if they have no fever and are not passing grossly bloody stools.97,98,300 Loperamide induces more rapid relief of symptoms, whereas the antimicrobial effects the cure. The duration of antimicrobials needed in TD appears to be short. Many patients respond to single-dose treatment, and no person needs more than 3 days of treatment.4,79,97 In cases of dysenteric diarrhea, the same antimicrobial regimen is given for 3 full days. Empiric therapy should be with fluoroquinolones in adults, and with TMP/SMX plus a macrolide or nalidixic acid in children. Azithromycin is currently being studied as an alternative antimicrobial agent. Rifaximin, because of its lack of absorption and systemic activity, has not been approved when TD is caused by invasive pathogens.153 Campylobacter strains are more resistant to regularly used antibiotics, including ciprofloxacin and rifaximin. Azithromycin is the preferred agent for this pathogen, which is found more commonly in Asia but seen in all high-risk areas. Viruses and parasites are also not successfully treated with antibacterial drugs. Antibiotics should not be continued in the face of persistent or worsening diarrhea, because these agents may be responsible for the illness.

Prevention and Prophylaxis Dietary Precautions. Food and water transmit the pathogens that cause infectious diarrhea and TD.6,7,76,95,96,100 When diar-

rhea occurs, however, the exact source cannot be determined. It is clear that education can play an important role in prevention of TD,16 but dietary habits usually cannot be rigidly controlled. Food in developing countries is often contaminated with fecal coliforms and enteropathogens.6 V. cholerae remains viable for 1 to 3 weeks in food,107 and Salmonella can survive 2 to 14 days in water or in the environment in a desiccated state.100 Risk of illness is lowest when most of the meals are selfprepared and eaten in a private home, it is intermediate when food is consumed at public restaurants, and it is highest when food is obtained from street vendors.27,100 The following standard dietary recommendations for prevention are based more on known potential vehicles for transmission of illness than on strong evidence, because most of the studies evaluating risk have found little correlation between routine precautions and the presence of diarrhea95,100: • Avoid tap water, ice made from untreated water, and suspect bottled water. Bottled and carbonated drinks, beer, and wine are probably safe. Boiled or otherwise disinfected water is safe. Tap water in high-risk countries is difficult to implicate in TD, but it has been shown to contain enteric bacteria and pathogenic viruses and parasites.100,209 Bottled carbonated beverages are considered safe because of the antibacterial effects of the low acidity. Alcohol in mixed drinks does not disinfect contaminated ice cubes, but bottled beer and wine are safe to consume. Most enteric organisms can survive freezing and melting in common drinks, so ice is not considered safe unless made from treated or previously boiled water. Ice in block form is often handled with unsanitary methods.100 • Avoid unpasteurized dairy products. These may be the source of infection with Salmonella, Campylobacter, Brucella, Listeria monocytogenes, Mycobacterium tuberculosis, and others.253 • Avoid raw meat and vegetables. Raw vegetables in salads may be contaminated by human waste that was used as fertilization, or by washing in contaminated water.100 Anything that can be peeled or have the surface removed is safe. Fruits and leafy vegetables can be disinfected by immersion and washing in iodinated water or by exposure to boiling water for 30 seconds. Raw seafood, including that in traditional dishes such as ceviche and sashimi, has been associated with increased risk of TD. Shellfish concentrate enteric organisms from contaminated water and can carry hepatitis A, noroviruses, Aeromonas hydrophila, Y. enterocolitica, V. cholerae, and V. parahaemolyticus. Raw fish can carry parasites such as Anisakis simplex, Clonorchis sinensis, and Metagonimus yokogawai. Raw meat is a source of Salmonella and Campylobacter and the vehicle for Trichinella, Taenia saginata, and Taenia solium (beef or pork tapeworm), and Sarcocystis. Although adequate cooking kills all microorganisms and parasites, if food is left at room temperature and recontaminated before serving, it can incubate Salmonella, Shigella, or ETEC and EAEC. Food served on an airplane, train, boat, or bus has probably been catered in the country of origin. Problems of food hygiene pertaining to these forms of public transportation may be related to employee handling of food even in the United States. Safe foods are those served steaming hot, dry foods such as bread, freshly cooked food, foods that have a high sugar content (e.g., syrups, jellies), and fruits that can be peeled.100

Chapter 62: Infectious Diarrhea from Wilderness and Foreign Travel

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TABLE 62-10. Prophylactic Medications for Prevention of Traveler’s Diarrhea* AGENT Bismuth subsalicylate Fluoroquinolones Rifaximin

PROTECTIVE EFFICACY

PROPHYLACTIC DOSE

65%

Two 262-mg tablets before meals and at bedtime Norfloxacin 400 mg, ciprofloxacin 500 mg, or levofloxacin 500 mg once a day Rifaximin 200 mg once or twice a day with meals

90% 70%–80%

COMMENT Safe; temporary darkening of stools and tongue Side effects, increased resistance Safe, nonabsorbable, no increased resistance; should be considered the standard agent for prophylaxis during high-risk travel

*Not generally recommended for travelers; used only in special situations (see text) and for no longer than 3 weeks.

Prophylactic Medication. Traditionally, chemoprophylaxis was an alternative for certain people making critical trips or for travelers with underlying medical conditions. Preventive drugs are generally recommended to be used for 3 weeks or less and will require a prescription from a physician. In past studies, 10% to 25% of European travelers to high-risk areas and up to one third of U.S. travelers to Mexico used to take prophylactic medication to prevent TD.100,182 Compared with empiric therapy with a single dose of an antimicrobial agent and loperamide, chemoprophylaxis is cost effective only when its use does not exceed a few days100 (Table 62-10). Several nonantimicrobial agents have been studied for prevention of TD, with some found to be minimally effective. Lactobacilli have been tested on the assumption that they are safe and favorably modify intestinal flora, but they did not invariably reduce the incidence of TD and provided protective efficacy only up to 47%.142 Antimotility drugs, such as loperamide, have adverse effects when used for prophylaxis.100 Of the nonantibiotic drugs, only bismuth subsalicylate (BSS), the active ingredient of Pepto-Bismol, has been shown by controlled studies to offer reasonable protection and safety. Several studies with volunteers and in the field have demonstrated that the use of BSS gives a protection rate from 40% to 77%,78,100 with fewer abdominal symptoms. Because the volume of the liquid preparation is quite large, BSS in tablet form was also evaluated. The currently recommended dosage of BSS is two tablets four times a day (2.1 g/day).78,96,100 Mild side effects include constipation, nausea, tinnitus, and temporarily blackened tongue or stools. In areas where doxycycline is used for malaria prevention, concurrent BSS should be avoided because it may bind to the antimicrobial and prevent absorption.100 Ninety percent of the salicylate in the liquid form of BSS is absorbed and excreted in the urine of children.78 Whether this salicylate cross-reacts with aspirin is unknown. However, BSS should not be used by someone with a history of aspirin allergy. Caution is recommended in small children, children with chickenpox or influenza (because of the potential risk of developing Reye’s syndrome), patients with gout or renal insufficiency, and persons taking anticoagulants, probenecid, methotrexate, or other aspirincontaining products. BSS is not approved for children younger than 2 years, and it is not recommended as prophylaxis for more than 3 weeks. The precise mechanism by which BSS prevents diarrhea is still unknown. Salicylate released during dissociation in the stomach exhibits antisecretory activity after exposure to bacterial enterotoxin on intestinal mucosa, and bismuth salts have antimicrobial activity.78 Adherence of bacteria to intestinal mucosa may be affected.

Since the first studies in the 1950s, a protective effect of antimicrobials in TD has been demonstrated. Several antimicrobial agents are highly effective in preventing TD when given over short periods to people at risk. Protection levels of 80% to 90% have been found with antimicrobial prophylaxis, provided that enteropathogens in the area were susceptible to the agent under investigation.96,100 The most experience has been obtained with doxycycline, TMP/SMX, and the fluoroquinolones. Other antimicrobials (streptomycin and sulfonamides, erythromycin, mecillinam) have shown significant protection but have not been well studied.96,221 Studies of U.S. students in Mexico taking trimethoprim (160 mg) and sulfamethoxazole (800 mg) twice daily for 3 weeks or once daily for 2 weeks demonstrated 71% and 95% protection, respectively.82,84 The fluoroquinolones (e.g., ciprofloxacin, ofloxacin, norfloxacin, pefloxacin, fleroxacin, levofloxacin) have been shown to be highly protective when employed as prophylactic agents. Because of the emergence of resistance among enteropathogens to tetracyclines, doxycycline can no longer be recommended for prophylaxis. Similarly, TMP/SMX resistance has been reported in many regions of the developing world.100 The effect of the antibiotics that were evaluated lasted only as long as the drug was continued. Subjects who remained in a high-risk area experienced an increased incidence of diarrhea during the week after cessation of prophylaxis.74,100 Despite dramatic protection against diarrhea, investigators in general do not recommend widespread use of these absorbed medications for prophylaxis by travelers for the following reasons: • Side effects. These include GI symptoms, photosensitivity, and other cutaneous eruptions and reactions. Furthermore, fluoroquinolones are not licensed for use in pregnant women and children. With larger numbers of people using these drugs, more serious side effects (e.g., Stevens-Johnson syndrome, hemolytic or aplastic anemia, antibiotic-associated colitis, anaphylaxis) will undoubtedly result. • Alteration of normal bacterial flora. Broad-spectrum antimicrobials may increase risk of infection with other antibiotic-resistant bacteria. Severe pseudomembranous colitis caused by colonic overgrowth with Clostridium difficile has occurred after therapy with most antibiotics. Vaginal candidiasis and GI side effects, including diarrhea, are common with antibiotic therapy. Changes in anaerobic flora can cause long-term alterations in the metabolism of bile acids and pancreatic enzymes, although the clinical effects are unknown.

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• Development of antimicrobial resistance. Overuse of antimicrobial agents increases the prevalence of resistant strains.91,100,125,282 • False sense of security. Travelers taking antibiotics may relax their vigilance of dietary precautions and increase their risk of acquiring enteric infections. • High cost of antimicrobials. • Rapid effectiveness of presumptive therapy. The result is that the illness is often limited to 12 to 24 hours. Although the consensus is most travelers should not employ absorbed drugs for prophylaxis, this approach may be appropriate for some travelers.80,96,100 Potential candidates would be residents of a low-risk country going to a high-risk area for short stays, who have one or more of the following conditions or requirements: • An underlying illness that increases the risk of enteric infection or morbidity, such as gastric achlorhydria (from surgery or taking proton pump inhibitors), AIDS, inflammatory bowel disease, diabetes (involving insulin treatment), or a cardiac, renal, or CNS disorder. • An itinerary that is so rigid and critical to the overall mission that travelers would not tolerate even minor schedule changes caused by illness. • Travelers who prefer prophylaxis after hearing the pros and cons of the approach. These recommendations were currently challenged by the new nonabsorbed rifaximin. This antimicrobial would be ideal for prophylaxis because of its activity against most enteric pathogens, its safety profile, its lack of absorption and systemic effects, and its limited medical indications. In one recent randomized, double-blind, placebo-controlled study, data support the idea of using rifaximin for the prevention of TD. Within the first 72 hours of arrival in Mexico, 210 travelers were randomized to receive either placebo or one of the following three dosages of rifaximin for 2 weeks: 200 mg once a day, 200 mg twice a day, or 200 mg three times a day. Between 72% and 77% of persons who took rifaximin were free of disease during 3 weeks of follow-up, significantly better than the rate for people on placebo alone (46%).89,168 Because of its minimal absorption and excellent safety profile, rifaximin is more likely to be used by high-risk travelers as antimicrobial chemoprophylaxis than absorbed drugs. No studies have evaluated prophylaxis of TD in young children, although they may be at higher risk for infectious diarrhea.

Immunoprophylaxis. Because of the emergence of in vitro resistance to antimicrobial agents (including the fluoroquinolones) among enteropathogens, prophylaxis with vaccines is being developed to control bacterial diarrhea. Several vaccines are under investigation for protection against rotavirus, Shigella, V. cholerae, and ETEC.32,63,64,148,164,220,223,266 Although these vaccines would be most beneficial to residents of developing countries, they will be heavily marketed to travelers. The ideal travel vaccine would provide immunity to multiple organisms.


BACTERIAL ENTEROPATHOGENS Escherichia coli E. coli is the most prevalent facultative gram-negative rod in human feces. Diarrheogenic E. coli is a heterogeneous group of

organisms that belong to one taxonomic species but have different virulence properties, epidemiologic characteristics, and clinical features. At least six groups have been characterized, based on either genotypic or phenotypic markers.221

Enteropathogenic E. coli. EPEC strains, the first of the diarrheogenic E. coli strains, were described between the 1920s and 1940s as causes of hospital nursery outbreaks.221 Usually identified by serotype, they are also characterized by a localized adherence pattern to a specialized cell line (HEp-2 cells).313 EPEC strains have worldwide distribution, and their most accepted virulence property is enterocyte attachment with selective damage to the surface without cell invasion. They induce production of a receptor (type III secretory system) that intimately interacts with the host cells, and this interaction leads to intracellular changes in the enterocyte.50,62,124,184,191,221,307 Lactoferrin, a component of breast milk, apparently protects against EPEC infection, with loss and degradation of the type III secretory system of this bacterium.230 Enterotoxigenic E. coli. ETEC strains, first identified in the 1970s, produce one or two enterotoxins that act on the small intestine by different mechanisms and with different time responses.221 One of these toxins is a heat-labile cholera-like toxin (LT), a high-molecular-weight protein immunologically and physiologically similar to cholera toxin. Human ETEC strains also have a low-molecular-weight, poorly antigenic toxin (ST) that is heat stable.263 Both enterotoxins inhibit sodium reabsorption and increase secretion of anions and fluid into the intestinal lumen, resulting in secretory diarrhea without inflammatory exudate.221 One common method for the diagnosis of ETEC is identification of specific DNA plasmid sequences using a hybridization technique.221 Recently, PCR has been used to improve the level of detection.10,24,111,305,314,330 ETEC has worldwide distribution and is the major cause of TD, accounting for 20% to 50% of cases in series from all parts of the world.155,221,249 It also accounts for a large percentage and frequently the majority of cases of enteritis in local pediatric populations of developing countries, where contaminated food and water are the primary sources of infection.221 Most outbreaks of ETEC in the United States have been waterborne.221,263 Person-to-person spread is infrequent because of the large infectious dose (106 to 1010 organisms).221 Contamination of different types of food with these strains has been reported.6,221 Enteroinvasive E. coli. EIEC strains, like strains of Shigella, possess the property of bowel mucosa invasion, resulting in microabscesses and ulcer formation. Because of the presence of the same invasive plasmid and some antigens of Shigella,191,264 EIEC must be considered (along with Shigella, Salmonella, Y. enterocolitica, E. histolytica, and V. parahaemolyticus) in the differential diagnoses of febrile dysenteric diarrhea and inflammatory bowel disease. EIEC strains are found worldwide and have been associated with food-borne outbreaks, especially in areas of South America and eastern Europe.191,264,319 Shiga Toxin–Producing E. coli. Shiga toxin–producing E. coli used to be classified as enterohemorrhagic E. coli (EHEC), and the organisms are also known as verotoxin-producing E. coli. They have caused outbreaks of diarrhea associated with consumption of contaminated beef, often fast-food hamburgers,

Chapter 62: Infectious Diarrhea from Wilderness and Foreign Travel unpasteurized apple juice, and more recently with contaminated vegetables. Contact with contaminated swimming pools and exposure to farm animals have also been associated with this infection.53,213,221,245,255,285,303 STEC produces copious bloody diarrhea with fecal mucus (hemorrhagic colitis), but fever is either low grade or absent.303 The most important STEC strain thus far identified is O157 : H7. The production of Shiga or similar toxins by these strains may be related to the hemolytic-uremic syndrome (HUS), a common complication in children infected with STEC O157 : H7 or Shiga toxin– producing Shigella. HUS may be life-threatening, and it is possible that antimicrobial therapy of STEC colitis, rather than preventing this complication, is related to more frequent development of HUS.*,326a

Enteroaggregative E. coli. EAEC strains are the most recent addition to the group of diarrheogenic E. coli. In recent years, they have been identified as important and prevalent enteric pathogens, especially in TD. They are non-EPEC and do not produce ETEC LT or ST, and they adhere to human laryngeal epithelial (HEp-2) cells in a typical aggregative pattern. Several bacterial markers have been studied as possible diagnostic aids, but no one is present in all strains.155,156,167 Some studies suggest that EAEC strains should be considered a phenotypically and genotypically heterogeneous group.36,60,155,193,221,222 Although the pathophysiology of EAEC is not completely understood, multiple possible virulence factors, as well as association with inflammatory cytokines, have been described, especially with interleukin (IL)-8.34,127,154–156,167,170,222,332 EAEC has been associated with acute and persistent illness and malnutrition in children with diarrhea, especially in the developing world,54,152,231,275,332 and recent studies have demonstrated that EAEC is also an important cause of TD, second only to ETEC in some areas of the world.3,5,6,116,167 Diffusely Adherent E. coli. Also known as enteroadherent E. coli, these non-EPEC strains show a diffuse adherence pattern to HEp-2 cells. Although associated with cases of diarrhea, the pathogenicity, pathophysiology, and importance of these strains are still not completely understood, and some authors propose that they be categorized as a subtype of EAEC.60,221,222

Diagnosis Laboratory culture cannot differentiate the various diarrheogenic strains of E. coli from normal bowel flora or from one another. Specialized assays, such as DNA probing and HEp2 adherence technique, are specifically used for research purposes.221 New serologic and molecular diagnostic techniques are under investigation and may become available in the future to differentiate between these organisms.10,20,25,111,202,224,256,290,314

Treatment Most cases of E. coli diarrhea are brief and self-limited, and therapy should be primarily supportive with oral fluid replacement and maintenance, empirically based on the clinical manifestations. Dysenteric illness, however, should be treated with antibacterial drugs whether in a developing country or an industrialized region. The exception here is colitis caused by STEC, which should not be treated with antibacterial drugs because of the possibility of further development of HUS (see Shiga *References 26, 46, 52, 108, 213, 224, 247, 299, 303, 307.

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Toxin–Producing E. coli, earlier). In developing tropical countries, TD associated with the passage of numerous watery stools is often caused by both ETEC and EAEC, and antibiotics may shorten the duration of illness, especially when started within 48 to 72 hours of symptom onset. Because of the increasing resistance of ETEC strains to antimicrobial agents (including fluoroquinolones), new therapeutic agents, such as rifaximin and azithromycin, are actively being sought.†,4,81,88,293 Because resistance patterns vary with geographic area and season, it is necessary to monitor the susceptibility of bacterial isolates in various regions of the world. Susceptibility testing is required when treating diarrhea caused by EPEC, because the strains are invariably resistant to a broad range of drugs.

Immunoprophylaxis Several studies looking for possible ETEC vaccines have been unsuccessful,32,192,266,276,277 apparently because of the presence of multiple and different colonization factor antigens that may not confer protection against all strains. A live vaccine for ETEC could offer advantages over a killed preparation in terms of duration and protection. Vaccines for EPEC and STEC are still under investigation.148

Salmonella Salmonella infections may result in four different clinical syndromes: gastroenterocolitis, enteric (typhoid) fever, bacteremia with focal extraintestinal infection, and asymptomatic carriage,30,274 depending on the type of organism and the host characteristics. Gastroenterocolitis is usually a mild to moderately severe, self-limited illness, with preferential involvement of the lower intestine. Enteric fever is characterized by septicemia with a prolonged toxic course if not treated. In patients infected with Salmonella choleraesuis strains, or with sickle cell disease or immunosuppression (e.g., those who have had a splenectomy; those who have HIV infection or a malignancy; those on immunosuppressive therapy; and newborns and older adults), nontyphoid salmonellae may disseminate and produce localized infection, including osteomyelitis or meningitis. A person with an abdominal aortic aneurysm is prone to develop Salmonella infection, leading to aneurysm perforation. Between 1% and 3% of patients who have recovered from typhoid fever may become chronic carriers who continue to shed the organism in the intestinal tract for 1 year or longer. Characteristically, the chronic typhoid carrier is an adult woman with cholelithiasis.30

Microbiology The following discussion pertains to nontyphoid Salmonella, unless otherwise stated. Salmonellae are nonsporulating, facultative, gram-negative rods. The genus Salmonella is composed of more than 2000 serotypes that infect humans and animals. Enteric fever results from infection by S. typhi or by S. paratyphi A, B, and C, which usually cause milder disease. S. typhi and S. paratyphi are further distinguished by their adaptation to humans as the only host. Although numerous other serotypes are capable of causing enteric fever, illness is usually limited to gastroenteritis.214,249,274 New serotypes occasionally become prominent, but most human infections are caused by only 10 serotypes, with S. typhimurium the most common one.

†

References 4, 81, 88, 125, 160, 214, 221, 282, 293, 320.

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Epidemiology Nontyphoid Salmonella organisms infect nearly all animal species and cause zoonotic infections. They can persist in fresh water for 2 to 14 days but may remain dormant in a desiccated nonsporulating state.30 Human salmonellosis is a worldwide problem, remaining endemic in large areas of the developing world, where it is passed primarily through contaminated food and water. The Centers for Disease Control and Prevention (CDC) estimates that the 25,000 human cases of nontyphoid salmonellosis reported annually in the United States represent less than 1% of the actual number of clinical cases.43,212,214 A recent report of typhoid fever in the United States from 1985 to 1994 showed that travel to underdeveloped countries is still a risk factor for this disease.212 Salmonella is the most common identifiable cause of foodborne illness. Contamination may occur from the animal feed, at slaughter, or, most often, during food preparation. Because the infectious dose is relatively high, averaging 103 to 106 organisms (but lower in water),30 the bacteria must multiply on or in food. This accounts for the high summer case incidence, when refrigeration may not be adequate.212 The foods most commonly implicated are meat, dairy products (especially unpasteurized), poultry, and eggs. Recent outbreaks of salmonellosis have been related to different foods, ranging from toasted oat cereal to alfalfa sprouts to infant formula.42,212,308 Person-to-person spread accounts for 10% of cases, but 20% to 35% of household contacts may become infected.212 Salmonella is an occasional cause of TD, accounting for up to 15% of cases, with marked geographic differences in serotype distribution.43,94,249 Elements that affect host resistance include normal gastric acid, gut motility, bacterial flora, and poorly understood immune factors. Bacterial virulence factors, the vehicle of transmission, and infectious dose are the major determinants of infection.30,212 Salmonellosis primarily affects children and older adults. Fifty-five percent of reported isolates in the United States are from persons under 5 years of age. The organism has an unexplained propensity to infect infants less than 1 year of age, who may experience serious systemic infection, including sepsis and meningitis. Greater susceptibility has also been observed in patients with gastrectomy-induced hypochlorhydria, hemolytic disorders (e.g., sickle cell anemia), parasitic infections (e.g., malaria, schistosomiasis), and chronic illness (e.g., malignancies, liver disease).212,214

Pathophysiology Salmonellosis involves mucosal invasion and possibly enterotoxin production.172,274 After surviving the gastric acid barrier, the organisms reproduce in the gut, where they attach to the walls of the ileum and colon, inducing local degeneration of the microvilli. Invasion occurs through vacuolization, with resultant discharge of the bacteria into the lamina propria, from where they gain entry into the bloodstream. At this point, only the strains that cause enteric fever enter and multiply within lymphatic tissue and phagocytic cells. The mechanism of diarrhea in enterocolitis is not clear. A heat-stable enterotoxin has been identified. In most cases, local inflammation of the bowel wall is not severe enough to cause mucosal sloughing and dysentery. Recent studies of pathogenesis demonstrated that IL-18 and gamma-interferon contribute to host resistance and that deficiency of IL-12 or nitric oxide is related to severity of infection.204,210 Protection against typhoid fever is associated with the

cystic fibrosis gene, called cystic fibrosis transmembrane conductance regulator (CFTR), and it resembles the protection of sickle cells against Plasmodium infestation. Apparently, S. typhi uses this gene to invade intestinal epithelial cells.173,252

Clinical Syndromes Although the incubation period for typhoid fever is usually 1 to 2 weeks, it is only 8 to 48 hours for intestinal infections with nontyphoid Salmonella.252 Nausea, vomiting, malaise, headache, and low-grade fever may precede abdominal cramps and diarrhea. Stools are usually foul and green-brown to watery, with variable amounts of mucus, blood, and leukocytes. Cholera-like fluid loss, or dysentery with grossly bloody and mucoid stools occurs less often. The acute phase lasts only a few days. Asymptomatic excretion of organisms in the stool continues for 4 to 8 weeks, and chronic carriers are rare. Infants less than 3 months of age experience longer illnesses (average, 8 days) with more complications. Among all ages, transient bacteremia is common, accounting for significant isolation of Salmonella types from blood. Fever and malaise occurring more than 1 week after resolution of diarrhea suggests a complication or another diagnosis.173,252 In healthy adults, Salmonella bacteremia occurs in 5% to 10% of infections and is not distinguishable from other causes of sepsis. Focal infections may be seen in any organ, but sites adjacent to the bowel are most common. Mortality is highest at the extremes of age, but deaths occur in all age groups.214

Diagnosis Diagnosis of enterocolitis can be made by clinical manifestations and isolation of Salmonella organisms from stool or rectal swabs cultured onto selective media (MacConkey’s or salmonella-shigella agar). Blood cultures are useful to identify a systemic nontyphoid salmonellosis. Blood cultures (or culture of bone marrow aspirates) for S. typhi or S. paratyphi are also used to diagnose enteric fever. Stool cultures are often negative early in the disease. Widal’s serum test is useful for diagnosing typhoid fever in areas with high prevalence, but not in industrialized areas, because of the more frequent occurrence of cross-reaction with other gram-negative organisms. Several PCR-based diagnostic techniques are currently being studied.

Treatment Supportive treatment with fluids is sufficient therapy for most cases of uncomplicated Salmonella enterocolitis. Antibiotics are not indicated because they do not shorten the illness, and they slightly prolong the carrier state and increase the risk of developing resistant strains.13,214 Antimicrobial therapy is indicated for persons who have symptomatic Salmonella infection with fever, systemic toxicity, or bloody stools. Patients with underlying debility (e.g., immunosuppression) that may predispose to septicemia or localized infection, young infants (less than 3 months), older adults (more than 65 years), and patients with sickle cell disease should be treated with antimicrobial agents. Fluoroquinolones are the treatment of choice because they shorten the duration of fever and diarrhea in salmonellosis. Dosages are the same as those recommended to treat shigellosis, although treatment is continued for 7 days (or 14 days if the patient is immunosuppressed). In cases of enteric (typhoid) fever, septicemic salmonellosis, or local tissue suppuration, antibiotic therapy is indicated. The drugs of choice for enteric fever in the United States are fluo-

Chapter 62: Infectious Diarrhea from Wilderness and Foreign Travel roquinolones. These drugs can be given for a shorter duration (10 instead of 14 days), resistance is still low, and posttreatment carriage of S. typhi is reduced.13,102 In many developing countries, the drug of choice is still chloramphenicol (25 to 50 mg/kg/day in divided doses every 6 hours) because of its low price and predictable activity. Alternative empiric therapy in the United States is a third-generation cephalosporin. Other traditional options, such as ampicillin or TMP/SMX,38 have low in vitro activity in many areas. Local suppuration may require 2 to 6 weeks of antibiotics, depending on the adequacy of surgical drainage. Salmonella species, like Shigella species, are showing increasing resistance to many antimicrobial agents worldwide.120,129,214,283

Immunoprophylaxis Immunity to Salmonella is serotype specific. Vaccines have not been successful for nontyphoid Salmonella because of the number of serotypes. For typhoid fever, immunoprophylaxis is possible, and three protective vaccines are now commercially available. The traditional killed vaccine is associated with a high reaction rate and has limited use in young children traveling in highly endemic areas. More frequently used for antityphoidal vaccination is a live-attenuated strain (Ty21a) that is given as one oral dose every other day for four doses,12,117 or an inactivated Vi polysaccharide preparation given as a single parenteral immunization.1 These two preparations are of approximately equal cost and effectiveness. New vaccines are under evaluation. One new live-attenuated S. typhimurium mutant is highly immunogenic and protective in animal models and induces cross-reactive antibodies to other enteric pathogens.306

Shigella Microbiology Dysentery has been described since the beginning of recorded history. At the end of the 19th century, Shiga first identified Shigella dysenteriae as the cause of an outbreak of dysenteric diarrhea in Japan, and since then, shigellosis has become synonymous with bacterial dysentery. As described before, other bacteria and protozoa are also capable of producing the bloody and mucoid stools that define this syndrome. Shigellae are thin, nonmotile, nonsporulating, gram-negative rods in the Enterobacteriaceae family. There are four species or groups: A (S. dysenteriae), B (Shigella flexneri), C (Shigella boydii), and D (Shigella sonnei). A, B, and C contain numerous serotypes.

Epidemiology Shigellosis occurs worldwide. S. dysenteriae 1 (Shiga bacillus), which causes severe disease, is most common in developing countries. In the United States and many other areas, particularly more industrialized regions, Shigella remains endemic, with S. sonnei replacing S. flexneri as the most common isolate.133 Humans and certain primates are the only hosts for Shigella. Fecal–oral contamination is the mode of spread. Common source infections occur through water or food prepared by contaminated hands.185 Shigella can survive freezing and thawing in ice cubes. With an infectious dose as low as 10 to 200 organisms, person-to-person spread is common.90 Even in countries with good sanitation, Shigella accounts for persistent endemic

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foci and high rates of transmission, especially among groups in close physical contact (e.g., gay men, children in daycare centers), groups with poor hygiene (e.g., mentally impaired patients), and those who lack sanitary facilities and water (e.g., populations in developing countries, Native Americans on reservations). Long-term carriage of Shigella is less common than for Salmonella. Shigella is a potential pathogen in the American wilderness. Environmental persistence averages 3 to 4 weeks, with best survival in cool fresh water.

Pathophysiology The essential virulence factor of Shigella is invasiveness associated with a large (120- to 140-megadalton) plasmid. Shigella organisms invade and proliferate within the epithelium of the large bowel, producing well-demarcated ulcers with cellular infiltrates (chiefly PMNs and proinflammatory cytokines) and overlying suppurative exudates.164,251,257 These organisms interact with the epithelial cells initially through a type III secretory system, with invasion of these cells and reorganization of their cytoskeleton.70,124,227,272 Organisms have also been demonstrated in the small bowel, with reduced potential for invasion or changes in the mucosa, causing instead a profuse watery diarrhea, possibly mediated by an enterotoxin.70 Despite similarities in pathogenesis between EIEC and Shigella strains, different molecular biology techniques have shown controversial results.19,264 However, one recent study supports the idea that EIEC and Shigella species are part of a pathovar of E. coli.191

Clinical Syndromes As with most enteric pathogens, infection with Shigella may be asymptomatic, mild, or severe. Rarely, a chronic carrier state may develop, depending on a combination of host and organism factors. Two distinct diarrheal syndromes may occur separately or sequentially in shigellosis. After a short incubation period of 1 to 3 days, illness begins with malaise, headache, nausea, fever, abdominal cramps, and watery diarrhea, representing small bowel infection. Children may present with fever, with diarrhea developing later. In the second and classic form of shigellosis, after 1 to 3 days of small bowel disease, colonic involvement causes progression to clinical dysentery. In this dysenteric form, the volume of stools decreases and the frequency increases, with up to 20 to 30 bowel movements a day, containing gross blood and associated with fecal urgency and often tenesmus. Fever is common in dysenteric cases, found in up to one half of cases of shigellosis overall. Mild abdominal tenderness is also common but without peritoneal signs. The natural history of shigellosis is varied, with most cases resolving spontaneously within 7 days but with others persisting for weeks.73,86 The mortality rate is as high as 25% in developing countries when S. dysenteriae 1 (Shiga bacillus) diarrhea is untreated, but it decreases to less than 1% with adequate antimicrobial therapy.

Complications Several potential complications of shigellosis may occur. Severe anemia and hypoalbuminemia may result from blood and protein losses. Febrile convulsions are seen in young children with shigellosis. Shigella has been described as a sexually transmitted disease and also as an unusual cause of urinary tract infection and pneumonitis. A severe leukemoid reaction with a white blood cell count of up to 50,000 may result after appar-

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ent clinical improvement. In some patients infected by strains that produce Shiga toxin, HUS syndrome develops, probably induced by formation of immune complexes.201 Reactive arthritis syndrome (or other reactive musculoskeletal symptoms) has also been reported in patients with S. sonnei and S. flexneri infection, sometimes associated with human leukocyte antigen (HLA) B27 positivity.136 Septicemia was found in less than 5% of Shigella infections, with fewer cases of metastatic abscesses.86,90

Diagnosis Laboratory tests often show mild leukocytosis with left shift (i.e., an increase in the number of immature granulocytes). If colitis is present, microscopic examination of the stool shows countless white (PMNs) and red blood cells, but this is not specific to shigellosis. Diagnosis is made by stool culture on selective media (MacConkey’s or salmonella-shigella agar), which is positive in most infected patients.86 Fresh stool or sigmoidoscopic biopsy is the best source of culture material, but rectal cotton swabs, although not as reliable, can be used if plated rapidly or placed in a holding medium. In hospitalized patients, blood cultures should be obtained. Few studies have tested the use of PCR for diagnosis of shigellosis.10,111

Treatment Therapy first involves fluid replacement. Although large-volume diarrhea is unusual, significant dehydration may occur, especially in children. Antimotility drugs are controversial in patients with signs of toxicity85; however, these medications are unlikely to be detrimental if antibiotics are used concurrently.7 Patients with fever and dysentery should be treated with antimicrobial agents, as these drugs decrease duration of fever, diarrhea, and excretion of Shigella in stool. Antibiotic-resistant strains are emerging worldwide, with recent reports in Asia, Oceania, and Latin America38,150,289 showing that most of the strains are resistant to ampicillin and TMP/SMX, whereas the fluoroquinolones remain active. The current recommendation for treatment is with a fluoroquinolone (norfloxacin, 400 mg; ciprofloxacin, 500 mg; or levofloxacin, 500 mg daily) for a total of 3 to 5 days. Single-dose therapy is probably effective in milder forms of illness.79,98,99,300 Fluoroquinolones are contraindicated in infants and children because of the possible effects on articular cartilage. However, short-course fluoroquinolone therapy appears to be safe. Alternative treatments for children in areas where TMP resistance occurs are nalidixic acid and furazolidone.269 Another option is azithromycin, but it needs further testing.4

Immunoprophylaxis Temporary immunity to homologous Shigella strains follows natural infection.87,229 A vaccine composed of specific polysaccharide conjugates of S. flexneri and S. sonnei has been shown to be safe and immunogenic in children.15 Other attenuated or killed strains or specific synthetic polysaccharides have shown promise in animal studies.56,164,254,310

Campylobacter Microbiology The Campylobacter organism is a small, curved, gram-negative rod, initially classified as Vibrio. C. jejuni/coli strains are widespread in the environment. The major reservoir is animals, including dogs, cattle, birds, horses, goats, pigs, cats, and

sheep.28 The strains of Campylobacter jejuni share up to 87% of their nucleotide sequence, and it is very difficult to differentiate them at the species level.69 A reemergent species, Campylobacter upsaliensis, has recently been associated with diarrheal disease, persistent diarrhea in patients with HIV infection, and a few cases of HUS.35

Epidemiology Most epidemics of gastroenteritis have been caused by contaminated food. The most important source for human illness is poultry, but epidemics have also been associated with ingestion of raw milk.28,29 C. jejuni has been isolated from surface water and can survive up to 5 weeks in cold water, ensuring its potential for wilderness waterborne spread. Person-to-person spread occurs but is uncommon. The prevalence of C. jejuni as a cause of TD varies with geographic area and time of year. TD secondary to C. jejuni is more prevalent in Southeast Asia and accounts for about 3% of cases in rainy summertime and up to 15% of cases during drier wintertime.28,211,271 One recent study proposed flies as an agent transmitting Campylobacter and as a possible explanation of the seasonal distribution.228 Studies in the United States and abroad have demonstrated that C. jejuni accounts for up to 25% of patients with infectious diarrhea and is often more common than Salmonella or Shigella species.28 C. jejuni is now the most common cause of bacterial gastroenteritis in developed countries. Rates are highest among children and young adults.

Pathophysiology The complete pathogenic mechanisms are unclear. All segments of the small and large intestine may be affected, accounting for the variety of diarrheal symptoms. Evidence of invasiveness includes recovery of bacteria from blood and presence of colitis, with cellular infiltration on intestinal biopsy. An unusual microtubule-dependent mechanism and a possible heat-labile enterotoxin may play a role in disease pathogenesis.186

Clinical Syndromes The incubation period of C. jejuni enteritis is 2 to 7 days. Clinical symptoms are extremely variable and nonspecific. Victims often have a 1-day prodrome of general malaise and fever, followed by abdominal cramps and pain that herald the onset of diarrhea, with up to eight bowel movements a day. The diarrhea is initially watery, followed by passage of stools that are bile stained or bloody. The reported symptoms (and their frequencies) are diarrhea (75% to 95%), cramps and abdominal pain (80% to 90%), nausea (20% to 50%), headache (50%), fever (50% to 80%), vomiting (20%), and bloody diarrhea (10% to 50%).28 Tenesmus is unusual. Physical examination is nonspecific, with variable degrees of fever (averaging 40° C [104° F]), abdominal tenderness, and dehydration. Microscopic evaluation of stool shows blood and PMNs in 60% to 75% of samples. The enteric symptoms subside in 2 to 4 days, and the entire illness resolves spontaneously within 1 week. Some patients developed postinfectious arthralgia, usually associated with more severe cases, apparently without any association with the use of antimicrobials.200 Campylobacter organisms are shed in the stool for 3 to 5 weeks after resolution of symptoms, but chronic carrier states have not been described. Up to 20% of victims may show clinical relapse, which is usually less severe than the original symptoms.28 Chronic diarrhea caused by C.

Chapter 62: Infectious Diarrhea from Wilderness and Foreign Travel jejuni has been reported in children and adults but is usually associated with significant underlying disease.

Complications C. jejuni infection has been associated with Guillain-Barré syndrome.28,157,218,259 Apparently, the mechanism of cross-reactivity could be explained by induction of antiganglioside antibodies by specific strains of Campylobacter.121 One study in Japan reported the possible association of specific strains and the development of two different syndromes: Guillain-Barré syndrome or Miller-Fischer syndrome, a variant of Guillain-Barré.298

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on marine organisms, and infection is acquired by ingesting infected and undercooked seafood or by contamination of a wound with infected water.175,267

Epidemiology

Treatment is primarily supportive, with oral fluids; dehydration is usually mild. Most patients have improved by the time that culture results return, and do well without antibiotics. Antibiotic treatment does not conclusively improve C. jejuni gastroenteritis, but earlier therapy appears to be effective31 and eradicates the organism from the stool within 48 hours. The antibiotic of choice is erythromycin or a fluoroquinolone (unless there is a high reported prevalence of resistant strains, as in Southeast Asia). TMP/SMX is not active against Campylobacter; the new rifaximin is active in vitro261 but still needs to be evaluated clinically. Fluoroquinolones are given in the same dosages as for shigellosis; they are active against all the major causes of dysentery (C. jejuni, Shigella, Salmonella). In children, because fluoroquinolones are contraindicated, erythromycin (20 to 50 mg/kg every 6 hours for 5 days) is an option. Another alternative, in view of increased resistance to fluoroquinolones by Campylobacter strains,118,282 is azithromycin, a newer macrolide that can be used in children and is active against all major bacterial enteric pathogens.125,189

V. cholerae is endemic in areas of Asia, Africa, and the Middle East. It has accounted for seven deadly worldwide pandemics since the early 1800s. The last began in 1961 in Indonesia and spread throughout Southeast Asia, the Middle East, and Africa; to parts of the Pacific and Europe; and, in the 1990s, to Latin America. In 1973, cholera resurfaced in the United States after being absent since 1911. Since then, a small number of cases have occurred along the Gulf Coast of Louisiana and Texas. Only 10 cases of cholera were reported in travelers returning from endemic areas between 1961 and 1981. In January 1991, an outbreak of cholera started in Latin America along the coast of Peru. Since then, this disease has become endemic in most regions of Latin America, moving as close to the United States as northern Mexico.175,267 The infection was associated with consumption of uncooked or poorly handled seafood, and it spread rapidly because of a highly susceptible population that has not been exposed to cholera for almost a century and because of inadequate water supply and sewage service. Cholera continues to be a disease of poor and lower socioeconomic groups; the Indian subcontinent and southwestern Asia are still the areas with the highest prevalence.104,175,268 The risk to travelers has been estimated at 1 : 500,000 during a journey to an endemic area,249 which should be further reduced with dietary discretion. Nonhuman reservoirs for V. cholerae O1 include marine or brackish waters.175,268 As with other strains (V. parahaemolyticus, non-O1 V. cholerae), shellfish ingest and carry these organisms. Fecal–oral spread is the major mechanism of transmission, and water is the most common vehicle, followed by food.104 The organism remains viable for days to weeks in various foods. Because of the large infective dose (106 to 1010 organisms),149 person-to-person spread is uncommon. Most cases of gastroenteritis caused by noncholera vibrios have been associated with ingestion of raw seafood. Cases have been reported from travelers, particularly after visits to coastal areas of Southeast Asia and Latin America. V. parahaemolyticus causes 70% of cases of food-borne gastroenteritis in Japan (where large amounts of raw seafood are eaten), leads to sporadic outbreaks in the United States, and is a common cause of TD in Thailand.33

Vibrio

Pathophysiology

Diagnosis Definitive diagnosis is made by stool culture on a selective medium (e.g., Skirrow, Butzler, Campy-BAP), with isolation rates directly related to severity of disease. Extraintestinal sources account for 0.4% of positive Campylobacter cultures in the United States and are usually preceded by GI infection. Blood is the most common site in extraintestinal disease, followed by the gallbladder and cerebrospinal fluid (in children), but because blood cultures are rarely drawn in the evaluation of gastroenteritis, the real frequency of bacteremia is unknown. The serologic tests available are still not well standardized and need further evaluation.

Treatment

Microbiology Cholera is a severe form of watery diarrhea often associated with dehydration. The disease is caused by Vibrio cholerae O group 1 (O1), a motile, curved, gram-negative rod. These microorganisms have two major biotypes, classic and El Tor, which produce similar clinical illness. Each biotype contains two main serotypes, Ogawa and Inaba.267 Non-O1 V. cholerae strains also produce diarrheal illness, but they show less potential for epidemic disease.175 Nine other species have been associated with human disease. V. parahaemolyticus, Vibrio fluvialis, Vibrio mimicus, Vibrio hollisae, and Vibrio furnissii are associated with GI disease. Others, mainly Vibrio vulnificus, are associated with wound infections and septicemia. All are halophilic, gram-negative rods that reside in seawater and

After passing through the stomach, the organism multiplies and colonizes the small bowel. The local effects of enterotoxin account for the pathophysiology of cholera. No pathologic changes are noted in the intestinal wall. The binding subunits of toxin attach to the membrane of the mucosa, after which the adenylate cyclase–activating B subunit enters the cell. The enzyme acts inside the serosal cell, enhancing production of cyclic adenosine monophosphate (cAMP). This molecule produces a 70% reduction in influx of water, saline, and a wide range of other substances into the gut mucosal cells, resulting in watery diarrhea. Glucose, potassium, bicarbonate, and most significantly, absorption of sodium and water linked to glucose remain intact. Thus, although plain water worsens cholera diarrhea, the addition of glucose renders the water and essential electrolytes absorbable, forming the basis for oral rehydration

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therapy.175,215,250,273 V. cholerae has the bacteriophage VPIphi, which encodes a receptor used by enterocytes for the phage CTXphi, which encodes the cholera toxin.178 Details of the pathogenesis of infection by the noncholera vibrios remain unclear. Some strains produce an enterotoxin, but generally it is not a cholera-like toxin. In the case of V. parahaemolyticus, a hemolytic toxin was thought to explain its effects, but the dysenteric illness that typically develops implies invasion. Another enterotoxin has been found in some strains.33

Clinical Syndromes Some cholera infections are asymptomatic, and 60% to 80% of clinical cases are presented as mild diarrhea, which never raises suspicion for cholera.149 After an incubation period of 2 days (range, 1 to 5 days), fluid accumulates in the gut, causing intestinal distention and diarrhea. Diarrhea may begin as passage of brown stools but soon assumes the translucent gray watery appearance known as “rice-water” stools. In serious cases, stool volume may reach 1 L/hr, leading to severe dehydration, acidosis, shock, and death. Vomiting may occur as a result of gut distention or acidosis.175,267 The clinical syndrome caused by noncholera vibrios is not characteristic. Intestinal illness is associated with diarrhea, abdominal cramps, and fever, with nausea and vomiting in about 20% of cases. Diarrhea may be severe, with up to 20 to 30 watery stools per day. In outbreaks of V. parahaemolyticus infection, explosive diarrhea associated with abdominal cramps and nausea is often described, with vomiting in about 50% and fever in about 30% of cases. In Asia, a dysentery-like syndrome with mucoid bloody diarrhea is often seen.33 Infections are usually brief, lasting an average of 3 days, with spontaneous resolution.

Diagnosis Diagnosis for any of the Vibrio strains can be made by stool culture on suitable media (e.g., thiosulfate-citrate-bile saltssucrose [TCBS] agar). Vibrios can survive for 1 week on a stoolsaturated piece of filter paper sealed in a plastic bag, before placing it in the culture medium.175 In the case of V. cholerae, another way to diagnose infection is using a darkfield microscopic examination of fresh stools, which may reveal the characteristic helical vibrio motion.

Treatment Aggressive replacement of fluid and electrolytes is the cornerstone of therapy for cholera, especially in severe cases. Severe untreated cholera has a 50% mortality, which may be reduced to 1% with appropriate treatment. Children are at higher risk for complications and death. With fluid replacement, most cases of cholera last 3 to 5 days, with the peak fluid losses 24 hours after the onset of illness. When hypotension or persistent vomiting is present, IV fluids are necessary, but as soon as initial rehydration is complete, ORS is used for maintenance. Less than 5% of patients require IV maintenance after initial rehydration, and ORS alone is successful in 90% of cholera cases without shock. With voluminous losses, ORS can be given by nasogastric feeding tube to continue fluids during the night. A normal or light diet should be resumed early in the course of treatment, after initial rehydration. Success of fluid replacement therapy was clearly demonstrated by the low mortality rate seen during the cholera

outbreak in Peru, where the principles of rehydration were applied.175,267 Antibiotics shorten the duration of diarrhea and excretion of organisms in severe cholera and reduce fluid losses, but they are not as important as fluid therapy. Oral antibiotics can be started within a few hours of initial rehydration. The drug of choice is doxycycline, a 300-mg single dose in adults or 50 mg/kg/day in four divided doses for children. This is perhaps the only indication for the use of tetracycline in children, because a short course (2 to 4 days) is unlikely to stain teeth. Furazolidone (100 mg every 6 hours for adults and 5 mg/kg/day in four divided doses for children) for 2 days is an alternative. Vibrio strains are also susceptible to fluoroquinolones, but these medications are more expensive.175,267 In vitro activity of rifaximin against vibrios has already been established.281 Treatment of patients infected with noncholera vibrios should also focus on fluid replacement. Little information exists on the benefit of antibiotic therapy for GI disease, but antimicrobials may be reasonable in dysentery-like cases or prolonged illness. The same antimicrobial agents used in cholera could be used against this infection. New developments in drug therapy of cholera, still under investigation, are aiming toward inhibiting the binding of cholera toxin to receptors in the enterocytes.302

Immunoprophylaxis Temporary immunity to homologous, but not to heterologous, strains of cholera develop after infection.175 The current parenteral vaccine has no antitoxin activity and is only about 50% effective in reducing attack rates over a 3- to 6-month period for those living in endemic areas. It is recommended for persons who live and work under poor sanitary conditions in highly endemic areas and for those with known achlorhydria. It is not recommended for travelers to endemic areas.175 Outside the United States, two additional vaccines are already available: an oral killed whole cell–cholera toxin recombinant B subunit (WC-rBS) and an oral live attenuated V. cholerae vaccine (CVD 103-HgR), both with a 60% to 100% rate of protection against V. cholerae O1 for at least 6 months. They are not active against V. cholerae O139.266 Finally, a bivalent (CVD103-HgR plus CVD 111) oral vaccine has been shown to be more effective than the monovalent one.13,22,134,301 A recent advance was the development of transgenic potatoes that synthesized cholera toxin subunit B without requiring a cold chain. This is a promising option for an inexpensive, effective vaccine for the developing world.9a

Yersinia enterocolitica Microbiology Y. enterocolitica is an intracellular, facultative anaerobic, gramnegative rod in the Enterobacteriaceae family, and different serogroups have been found to cause human infection.

Epidemiology The major natural reservoirs of the organism are wild, farm, and domestic animals. In the United States and Europe, the organism resides in surface and unchlorinated well waters. Evidence indicates that persistence in warm water ranges from days to weeks, with longer survival at colder temperatures. Human isolates of Y. enterocolitica are found worldwide, but with preference for colder regions such as Canada and Northern

Chapter 62: Infectious Diarrhea from Wilderness and Foreign Travel European countries, with an incidence equal to or greater than those of Salmonella and Shigella.208 Transmission occurs from fecal–oral contamination, through food and water, and probably through person-to-person or animal-to-person contact.208,249,311 Raw milk and oysters have also been implicated as vehicles of transmission. The infectious dose and attack rate are not well studied, but yersiniosis is suspected to be caused by ingestion of a large infectious dose based on a common source of transmission. The incubation period averages 3 to 7 days. Patients with β-thalassemia show a greater risk for acquisition of yersiniosis.8

Pathophysiology Illness caused by Y. enterocolitica may involve three pathogenic mechanisms: bowel mucosal invasion, release of a heat-stable enterotoxin similar to that produced by ETEC, and elaboration of a cytotoxin.73,208 The organism multiplies in the small bowel and characteristically invades the mucosa in the region of the terminal ileum and colon. The mucosa may be diffusely inflamed with small and shallow ulcerations. Also, some bacteria migrate through lymphatics to mesenteric lymph nodes, producing adenitis with focal areas of necrosis.

Clinical Syndromes The most common clinical presentation in yersiniosis is gastroenteritis, characterized by diarrhea, fever, and abdominal pain, with nausea and vomiting in 20% to 40% of cases and dysentery (passage of bloody stools) in 10% to 25%.208,311 Fever or abdominal pain without significant diarrhea may be the most prominent sign, mimicking appendicitis in up to 20% of patients with positive stool cultures.18 Although acute appendicitis has been associated with serologic evidence of Y. enterocolitica infection, the usual surgical findings are mesenteric adenitis or terminal ileitis. Rarely, severe colitis results in septicemia, extensive necrosis, or perforation. Numerous extraintestinal manifestations of Y. enterocolitica infection include skin rash (erythema nodosum or maculopapular) and arthritis, probably related to an immune reaction. Extraintestinal infection involving lung, joints, lymph nodes, wounds, or septicemia may occur with or without enteritis. In the majority of intestinal infections, illness is mild and self-limited, with duration averaging 1 week, but some patients experience prolonged symptoms.208,311 Excretion of the organism in stool continues for a few weeks to months. Complications may be related to particularly severe disease and a misdiagnosis of Crohn’s disease or appendicitis and development of Reiter’s disease or collagenous colitis.205

Diagnosis The diagnosis of yersiniosis is usually made by stool culture, but it can grow also from blood or surgical samples. The organism grows better at lower temperatures (22° to 25° C [71.6° to 77° F]), which inhibit most other enteric bacteria. Abnormalities related to ileitis or colitis and seen on contrast radiography and colonoscopy may be mistaken for other causes of colitis.17,208 Serologic tests are also diagnostic and especially helpful to diagnose Yersinia arthritis.

Treatment Tetracyclines have been suggested as the drug of first choice for chronic or fulminant infections,17 but Yersinia is also susceptible in vitro to streptomycin, chloramphenicol, aminoglycosides,

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fluoroquinolones, TMP/SMX, and the new rifaximin. Most strains are resistant to penicillins and cephalosporins and variably resistant to erythromycin and sulfonamides.122,203

Aeromonas Species and Plesiomonas shigelloides Aeromonas species and Plesiomonas shigelloides are gramnegative, facultative anaerobic, nonsporulating rods. Their normal habitats are water and soil. These bacteria have been implicated in a variety of human illnesses, most often gastroenteritis.146,147,163,249,316 Aeromonas was part of the Vibrionaceae family until the family Aeromonadaceae was established to include the 14 species so far identified. Only five species (Aeromonas hydrophila, Aeromonas caviae, Aeromonas veronii, Aeromonas jandaei, and Aeromonas schubertti) have been associated with a variety of human diseases, including gastroenteritis, soft tissue infections, HUS, burn-associated sepsis, and respiratory infections.163,316 A. hydrophila is the most commonly isolated species, but its real prevalence is still uncertain. A. hydrophila has been associated with diarrheal illness in the United States, Australia, India, Latin America, and southwestern Asia.163,315,316 An association between the illness and drinking untreated spring or well water was demonstrated in the United States.163 Pathogenicity includes production of cytotoxin, enterotoxin, and proteases, as well as the capacity of adhesion and invasion, with participation of a type III secretory system.331 The pathogenicity of A. hydrophila remains controversial.163,278 Clinical illness associated with enteric infection by A. hydrophila varies from acute to chronic diarrhea and from passage of watery stools to dysentery with colitis.163,278,315 Median duration of diarrhea is 2 weeks, but occasional cases persist a month or longer. Asymptomatic carriers have been identified. Non-GI infections, such as soft tissue infections and septicemia, have been associated with exposure of wounds to water. Aeromonas strains are susceptible to chloramphenicol, tetracycline, TMP/SMX, fluoroquinolones, rifaximin, and aminoglycosides but are resistant to ampicillin and erythromycin.122,163 P. shigelloides has been isolated from patients with gastroenteritis, both in sporadic cases and in outbreaks.147,249 Infection has been associated with recent travel and ingestion of raw or inadequately cooked shellfish. Plesiomonas may cause dysenteric illness suggestive of an invasive organism, but its pathogenic mechanisms remain poorly defined.147 Plesiomonas is susceptible in vitro to tetracyclines, aminoglycosides, quinolones, TMP/SMX, azithromycin, and rifaximin.122,294

Miscellaneous Bacterial Agents Klebsiella pneumoniae and Klebsiella oxytoca have been reported to occasionally cause diarrhea, but they are usually commensals of the GI flora.130 Another cause of severe diarrhea in hospitalized (usually postoperative) patients receiving antibiotics is Staphylococcus aureus. The causative organism of this antibiotic-associated diarrhea illness may be methicillinresistant S. aureus.260,279


VIRAL ENTERIC PATHOGENS Studies have identified viruses as major causes of acute nonbacterial GI infections.27,48,49,139 The most important defined agents are noroviruses and other caliciviruses, rotavirus, enteric

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adenoviruses, and astroviruses. Usually they cause vomiting with or without mild and self-limiting watery diarrhea. Transmission occurs through fecal–oral contamination or person-toperson transmission. Respiratory symptoms are common in patients with viral gastroenteritis. Caliciviruses and astroviruses are similar to noroviruses in structure and clinical appearance. They generally infect in early childhood and apparently provide lifetime immunity.240,241

Noroviruses Noroviruses are the leading cause of viral gastroenteritis of all ages. Norwalk virus is the prototype strain that belongs to the genogroup I, and it was the first well-described etiologic agent in nonbacterial gastroenteritis outbreaks, in an elementary school outbreak that occurred in Norwalk, Ohio.176 Soon after, several other small round viruses were identified as causes of nonbacterial gastroenteritis.240,241 Noroviruses are nonsymmetrical, single-stranded ribonucleic acid (RNA) viruses, recently classified as being in the family Caliciviridiae.166,190 They are the main cause of outbreaks of epidemic nonbacterial GI illness worldwide. They also cause “winter vomiting disease” because of their wintertime predisposition and common association with vomiting. In the United States, the proportion of norovirus outbreaks increased from 1% in 1991 to 12% in 2000, mainly related to food-borne outbreaks.326 These viruses are highly infective (requiring only 10 to 100 organisms per inoculum), and the infection is spread by common-source vehicles with a propensity for secondary person-to-person spread (high secondary attack rate).139 Humans are the only known carriers of these viruses. Outbreaks have been recognized in family settings, health care facilities, nursing homes, schools, cruise ships, and travel settings, characteristically affecting both children and adults in the United States. They are found less often in neonates and toddlers. Contaminated water supplies, drinking water in cruise ships, recreational swimming pools, and commercial ice cubes have been implicated in outbreaks.139,190 Vehicles identified for food-borne outbreaks include contaminated shellfish, salads, bakery products, cold foods, cooked meat, and fresh fruits.241 Between 20% to 67% of outbreaks of noroviruses have been associated with food.40,233 After a cruise ship has experienced a norovirus outbreak, this viral infection can continue to be a problem in future trips, despite extensive sanitization.161 After invasion of the enterocytes, the viral particles replicate inside, resulting in damage to the villi and in crypt cell hyperplasia.240 Malabsorption of fat, lactose, and xylose occurs with these histologic changes. The exact mechanisms of diarrhea production in viral gastroenteritis are not completely understood. Small numbers of viral particles are shed in stool during the acute illness, but prolonged carrier states are not seen. In the United States, antibodies in stools typically appear during late adolescence, but in tropical, developing countries, children acquire antibodies at a young age. Although antibodies persist in most people, they do not provide protection from clinical illness.240 A recent study has found that people with histoblood group antigens type B may be protected against infection with Norwalk virus or norovirus genogroup I.262 Transmission is followed by an incubation period of 24 to 48 hours, and illness begins abruptly with vomiting, abdominal cramps, and diarrhea. Stools are watery and usually do not contain blood or leukocytes. Other common symptoms include

low-grade fever, malaise, myalgias, respiratory symptoms, and headache. Illness is almost always mild and self-limited, lasting 1 to 2 days. Complications and mortality are extremely rare and usually involve older adult and debilitated patients. Some malabsorption of fats and disaccharides persists after the acute illness. Supportive treatment with oral fluids and electrolytes is sufficient in the vast majority of cases.240 Historically, because of the difficulty or impossibility of growing these viruses in cell culture, electron microscopy was the initial means of detecting these viruses. Now, immunoassays and molecular techniques (reverse-transcription PCR) are available for detection of these small round RNA viruses in stool.126,165,219,240 Vaccine development is being explored for the noroviruses but the studies are in a very early stage.

Rotavirus Rotaviruses are 70-nm, double-stranded RNA viruses that are classified by the capsid antigens, with group A and serotype G1 being the most common in human infections worldwide. Most severe infections in children are caused by serotypes G1 to G4.25,242 Rotavirus is the most common enteric pathogen in children, causing diarrhea worldwide and resulting in around 800,000 deaths per year.48,139,174,242,325 Infection tends to be endemic, with peak incidence during winter months in temperate climates. Transmission is by person-to-person contact or as a result of common-source outbreaks. Viral shedding occurs in stools, and particles can retain infectivity for months. Rotaviruses have been found in almost every animal species, and in general, animal strains have reduced virulence for humans.25,48 Rotavirus infects humans repeatedly, at any age. It is the most frequently isolated pathogen in infantile diarrhea and is responsible for a disproportionate amount of hospitalization for dehydration.25,242 The majority of symptomatic infections occur in children less than 3 years old, with peak incidence in children 6 months to 2 years of age. Rotavirus can also cause illness in adults, apparently with the same strains that infect the children and usually associated with secondary spread within a family.25,61 Nonspecific pathologic changes are seen in small bowel epithelial cells, with particles identified intracellularly. The exact mechanism of diarrhea is unknown, but a net secretion of water, sodium, and chloride occurs during the illness. Diarrheal losses contain 30 to 40 mEq/L each of sodium and potassium. Lactose malabsorption may persist for 1 to 2 weeks and is associated with continued viral excretion in stool. Large numbers of viral particles are shed in the stool of ill patients, but prolonged excretion is unusual.242 After an incubation period of 24 to 72 hours, illness begins with vomiting, followed by diarrhea associated with abdominal cramps, low-grade fever, and malaise. Vomiting usually resolves within 2 days (range, 1 to 5), but the diarrhea may last 3 to 8 days or longer. Natural infection reduces the incidence and severity of subsequent episodes. Serum antibody levels are demonstrated within the first few years of life and in almost all adults but appear to be nonprotective. Severity of illness usually decreases with age. Adults are more likely to have asymptomatic or mild illness with less vomiting. Dehydration frequently occurs in children, accounting for appreciable mortality in developing countries. Fortunately, oral fluid and electrolytes can be successfully used in most cases.242

Chapter 62: Infectious Diarrhea from Wilderness and Foreign Travel The first rotavirus vaccine approved by the FDA in 1998 was a tetravalent rhesus-human strain that provides coverage against the four common G serotypes of human rotavirus.232,242,312 In clinical trials in industrialized countries, this vaccine provided 50% to 70% protection (up to 60% to 100% protection against severe cases). The recommendation was to give this vaccine orally to all children at 2, 4, and 6 months of age,232 but the vaccine was withdrawn because of associated intussusception (calculated risk of 1/10,000 to 1/32,000 vaccine recipients).23 Several new safe and effective rotavirus vaccines are being developed, with one already licensed in Mexico in 2004 and another in the last stages for approval in the United States at the time of this writing.63,325


INTESTINAL PROTOZOA Protozoal infections may be pathogenic or commensal (which have little or no effect) to the human host. Most protozoal infections are suspected on the basis of subacute or chronic GI symptoms, which may fluctuate over time. Although acute self-limited diarrheal illness may occur, only a small proportion of cases of acute TD are caused by parasites. The symptoms are nonspecific, and the diagnosis is often made on stool examination. Several factors have increased the prevalence of intestinal parasites in the United States and worldwide: an increase in immunocompromised patients, who frequently become infected by these organisms; improvement in diagnostic techniques; changes in social behaviors (increased use of daycare and nursing homes, more frequent international travel); and in the United States, increased immigration of people from Asia, Africa, and Latin America.131,177,179 As with enteric bacteria, symptoms from infection by intestinal protozoa depend on the level of bowel colonized. Those colonizing the small intestine, such as Giardia and coccidia (see Cryptosporidium, later), cause a wide spectrum of GI complaints, including malabsorption (resulting in foul stools and flatulence) and weight loss in persistent infections. Although many protozoa are capable of superficial mucosal invasion, only Entamoeba histolytica and Balantidium coli, which colonize the colon, can ulcerate the bowel wall, cause dysentery, and spread to other tissues.131 All intestinal protozoa are transmitted by the fecal–oral route, so infection rates are highest in areas and groups with poor sanitation, close contact, or particular customs favoring transmission. These reemerging infections have been related to large outbreaks of communicable diseases in the United States, often secondary to water contamination. Protozoal parasites were the most frequent etiologic agents detected in waterborne outbreaks from 1991 to 1994.187,209,217 In addition to spread by food, water, and person-to-person contact, mechanical vectors such as flies may spread these organisms. Transmission of intestinal protozoa is favored by a hardy cyst, which is passed in the feces of an infected host. In addition to an infective cyst, the life cycle for most intestinal protozoa includes a trophozoite, which is responsible for reproduction and pathogenicity. Only a single host is required, except for Sarcocystis, which requires ingestion of raw meat from an intermediate host. Zoonotic spread to humans has been documented for Giardia, Cryptosporidium, Entamoeba polecki, and B. coli. Treatment of intestinal protozoal infections is summarized in Table 62-11.

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TABLE 62-11. Antiparasitic Therapy for Infectious Diarrhea in Adults DIAGNOSIS Giardiasis

Entamoeba histolytica excretion (asymptomatic) Entamoeba histolytica diarrhea

Cryptosporidiosis

Cyclosporidiosis Isosporiasis

Microsporidiosis

RECOMMENDATION Metronidazole 250 mg tid (15 mg/kg/day for children), albendazole* 400 mg qd, or quinacrine† 100 mg tid for 7 days; or tinidazole* 2000 mg single dose; or nitazoxanide 500 mg bid for 3 days (100 mg bid for 3 days for children 1 to 4 years of age; 200 mg bid for 3 days for children 4 to 11 years of age) Iodoquinol 650 mg tid for 20 days or paromomycin 500 mg tid for 7 days Metronidazole 750 mg tid for 5 to10 days or tinidazole* 1000 mg bid for 3 days, followed by iodoquinol 650 mg tid for 20 days or paromomycin 500 mg tid for 7 days Nitazoxanide 500 mg bid for 3 days; in severe cases or patients with AIDS, consider nitazoxanide 500 mg bid for 2 weeks, paromomycin 500–750 mg tid or qid for 2 weeks; or azithromycin 1200 mg qd for 4 weeks TMP/SMX 160 mg/800 mg bid for 7 days, followed by 160 mg/800 mg 3 times per week in patients with AIDS TMP/SMX 160 mg/800 mg qid for 10 days, followed by 160 mg/800 mg bid for 3 weeks, or pyrimethamine 75 mg qd with folinic acid 10 mg qd for 2 weeks Albendazole* 400 mg bid for 2 to 4 weeks, followed by chronic suppression in patients with AIDS

*Albendazole and tinidazole were recently approved and are available in the United States. † Quinacrine is not commercially available in the United States. bid, twice daily; qd, daily; qid, four times daily; tid, three times daily; TMP/SMX, trimethoprim and sulfamethoxazole.

Giardia lamblia G. lamblia (also known as Giardia intestinalis or Giardia duodenalis) is a flagellate protozoan that was first observed in 1681 by Leeuwenhoek. In the last 40 years, it has gained recognition as an important human pathogen.103,197 The classification of Giardia species remains controversial. Giardia is the most common protozoal intestinal parasite isolated worldwide. All age groups are affected.103,177,237 Giardiasis usually represents a zoonosis, with cross-infectivity from animals to humans, and vice versa. Giardia has been found in stools of beavers, cattle, dogs, cats, rodents, and sheep.237 The infective dose of Giardia for humans is low: 10 to 25 cysts caused infection in 8 of 25 subjects; more than 25 cysts caused infection in 100%. Person-to-person spread may be the most common means of transmission for humans. Twenty-five percent of family members with infected children become infected.103 Areas and populations with poor hygiene and close physical contact have higher rates of infection. Venereal trans-

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mission occurs among homosexuals through direct fecal–oral contamination. Epidemics and carrier rates of 30% to 60% have been found among children in daycare centers and in Native American reservations. Water is a major vehicle of infection in community outbreaks.209 Cysts retain viability in cold water for as long as 2 to 3 months. In the United States from 1964 to 1984, 90 outbreaks (24,000 cases) of giardiasis were linked epidemiologically to water, and it is still the most frequently identified cause of waterborne diarrhea outbreaks. Most of these occurred in small water systems that used untreated or inadequately treated surface water.194,195,209 Clear and cool mountain water has been so often associated with giardiasis that the illness has been called backpacker’s diarrhea or beaver fever (although fever is not usually seen). An outbreak in Aspen, Colorado, in 1964 was the first well-documented waterborne outbreak in the United States, and recent outbreaks around the same area indicate that this area remains endemically infected with Giardia. In the northeastern states, large outbreaks have occurred in the mountain communities of Rome, New York, and Berlin, New Hampshire. Every U.S. region has experienced waterborne outbreaks, but the western mountain regions (Rocky Mountains, Cascades, Sierra Nevada) have reported the majority, and giardiasis must be considered endemic there.103,144,209,237 Giardia accounts for a small percentage of TD.249 It has been identified in a large percentage of cases among travelers to St. Petersburg, Russia, where tap water is the usual source. Because of the relatively long incubation period and persistent symptoms, Giardia is more likely to be found as the cause of diarrhea that occurs or persists after returning home from travel to any developing region.90 The pathophysiologic mechanisms of diarrhea and malabsorption in giardiasis are poorly understood.237 Reversible malabsorption of fats, vitamins A and B, folate, and disaccharides has been demonstrated in some patients with diarrhea. Malabsorption may result from (1) physical blockade by large numbers of trophozoites blanketing the intestinal mucosa, (2) deconjugation of bile acids, (3) bacterial or fungal overgrowth in the small intestine, (4) increased turnover of cells on the mucosa of the villi, which do not absorb normally, and (5) epithelial damage. Altered gut motility and hypersecretion of fluids, perhaps through increased adenylate cyclase activity, may play a role. Histologic changes of villous atrophy and inflammatory infiltrates with epithelial cell destruction have been observed. In some series, these changes correlated with degree of malabsorption and reverted to normal after treatment. However, most small bowel biopsies in human patients demonstrate minimal or no changes, with only occasional mucosal invasion (with trophozoites found intracellularly and extracellularly) and no local inflammatory response.103 Enterotoxins have not been found. More than one mechanism is probably involved. Most infections are asymptomatic, and in endemic areas, Giardia is found in healthy people. The attack rate for symptomatic infection in the natural setting varies from 5% to 70%.237 Asymptomatic carrier states with high numbers of cysts excreted in stools are common. Correlation between inoculum size and infection rates has been noted, but not with numbers of cysts passed or severity of symptoms. Infectivity apparently depends on both host and parasite factors.237 Hypochlorhydria, certain immunodeficiencies, blood group A, and malnutrition apparently predispose to symptomatic infection.103,237

Figure 62-2. Giardia lamblia trophozoite seen by methylene blue wet mount staining under oil (×1000).The finding of cysts or trophozoites in a patient with diarrhea is sufficient to make a tentative diagnosis of giardiasis.

The incubation period averages 1 to 2 weeks, with a mean of 9 days and a wide clinical presentation. A few people experience abrupt onset of explosive watery diarrhea accompanied by abdominal cramps, foul flatus, vomiting, low-grade fever, and malaise. This typically lasts 3 to 4 days before transition into the more common subacute syndrome. In most patients the onset is more insidious and symptoms are persistent or recurrent. Stools become mushy, greasy, and malodorous. Watery diarrhea may alternate with soft stools and even constipation. Upper GI symptoms, typically exacerbated postprandially, accompany stool changes, but they may be present in the absence of soft stool. These include mid-abdominal and upper abdominal cramping, substernal burning, acid indigestion, sulfurous belching, nausea, distention, early satiety, and foul flatus. Constitutional symptoms of anorexia, fatigue, and weight loss are common. Unusual presentations include allergic manifestations, such as urticaria, erythema multiforme, and bronchospasm. Some Giardia infections are associated with a chronic illness. Adults may have a longstanding malabsorption syndrome and marked weight loss, and children may have a failure-to-thrive syndrome.103,237 Laboratory confirmation of giardiasis can be difficult. Stool examination used to be the primary means of diagnosis (Fig. 62-2) but is being replaced by newer immunodiagnostic tests. Trophozoites may be found in fresh, watery stools but disintegrate rapidly. Although trophozoites remain in fresh stools for at least 24 hours, stools should be preserved in a fixative such as polyvinyl alcohol or a formalin preparation if not immediately examined. Cyst passage is extremely variable and not related to clinical symptoms.237 In the office, fresh stool can be mixed with an iodine solution (e.g., Gram’s iodine) or methylene blue and examined for cysts on a wet mount. Many antibiotics, enemas, laxatives, and barium studies mask or eliminate parasites from the stools, so examinations should be delayed for 5 to 10 days after these interventions. Trichrome stain is better than the formalin–ether concentration technique for identification of protozoal cysts and trophozoites. The current recommendation is to examine three samples taken at intervals of 2 days. Another noninvasive office test is duodenal mucus sampling, using a string test (Enterotest), which has a reported sensitivity of 10% to 80%.112,237 Duodenal biopsy is rarely necessary but may be the most sensitive test.112

Chapter 62: Infectious Diarrhea from Wilderness and Foreign Travel A commercial enzyme immunoassay (EIA) has shown the same sensitivity as microscopic examination, but its specificity is 100%, making it a convenient screening method. EIA is much easier and requires less experience than microscopy, but it cannot be used to differentiate between cysts and trophozoites.9 Immunofluorescent techniques using monoclonal antibodies could detect low numbers of organisms in a short time but require centrifugation of the sample,113 and molecular techniques need further development.226,237,322 Immunologic responses to Giardia infection are complex. Epidemiologic studies show acquired resistance, with lower rates of infection and illness (1) among residents of endemically infected areas compared with visitors and (2) among adults compared with children. However, reinfection does occur. Levels of IgG antitrophozoite antibodies rise with both symptomatic and asymptomatic infections, helping to clear the infection. Hypogammaglobulinemic patients have a higher incidence of symptomatic giardiasis, implying an important protective function of immunoglobulins.237 Effects of mucosal secretory antibodies in humans have not been clearly demonstrated, although mouse studies show a protective effect of IgA secretory antibodies. Both cellular and humoral responses to Giardia have been demonstrated. Immunologic responses are effective in the majority of infections because spontaneous clinical recovery is common with or without the disappearance of organisms. The average duration of symptoms in all ages ranges from 3 to 10 weeks.237 Because of the difficulty and expense of confirming the diagnosis in some patients, a therapeutic trial of drugs may be attempted when suspicion is high. Imidazole derivatives (e.g., metronidazole) affect bacterial flora as well, so they are less specific but still better for empiric (unproven diagnosis) therapy because of their wide activity. Symptomatic patients should be treated for comfort and to prevent the development of chronic illness. Asymptomatic carriers in nonendemic areas should be treated when identified because they may transmit the infection or develop symptomatic illness. No drug is effective in all cases. In resistant cases, a longer course of two drugs taken concurrently has been suggested. Relapses occur up to several weeks after treatment, necessitating a second course of the same medication or an alternative drug. Malabsorption usually resolves with treatment, but persistent diarrhea may result from lactose intolerance or a syndrome resembling celiac disease rather than from treatment failure.237 Three groups of drugs are currently being used: nitroimidazoles (metronidazole, tinidazole, albendazole, ornidazole, nimorazole), nitrofuran derivatives (furazolidone), and acridine compounds (mepacrine, quinacrine). Metronidazole (Flagyl, 250 mg three times a day for 5 days for adults) is often used in the United States. Cure rates of 85% to 90% are comparable to those with quinacrine but with better tolerance. Tinidazole (Fasigyn, 2000 mg in a single dose) has the same success rate with better compliance but was not approved for this use in the United States in 2004. Nitazoxanide (Alinia) has comparable efficacy to metronidazole and is available in suspension for children as young as 1 year of age (100 mg twice a day for 3 days for younger than 4 years, 200 mg twice a day for 3 days for ages 4 to 11 years, 500 mg twice a day for adults).108a Quinacrine (Atabrine, 100 mg three times a day for 5 days for adults and 7 mg/kg/day in three divided doses for 5 days for children), achieves cure rates of about 95%. Unfortunately, it is no longer

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available in the United States because it produces more frequent side effects, especially in children. No pediatric liquid form is always available. For use in severely symptomatic individuals or pregnant women, the nonabsorbable drug paromomycin (Humatin, 25 to 30 mg/kg in three divided doses for 5 to 10 days) has been effective.103,114,135,197,234,237

Entamoeba Lösch described the trophozoite form of Entamoeba in 1875 and Quincke and Ross the cyst form in 1893. Recently, molecular biologic studies confirmed the existence of an invasive parasite (E. histolytica) and a noninvasive, commensal organism (Entamoeba dispar).158,162,198,292 Isoenzyme analysis has recognized 22 different zymodemes of E. histolytica, which may explain the pathogenic and commensal strains and the geographic differences in rates of invasive disease.36,162,258 E. histolytica is found worldwide. Approximately 12% of the world’s population is infected.258 The higher prevalence (30% to 50%) in tropical countries (Mexico, India, Africa, Central and South America) is related to increased risk of fecal–oral contamination, which depends on sanitation, cultural habits, crowding, and socioeconomic status.36,162,292 It is the second most important cause of death by parasitic infection worldwide. Similar conditions create pockets of endemic infection in the United States among institutional inmates, Native Americans on reservations, and homosexuals. Importation of infections by travelers and immigrants accounts for most cases in the United States and other temperate countries.117 Attack rate and prevalence are difficult to determine because the majority of infections are asymptomatic, and screening with single stool samples is likely to identify only 20% to 50% of cases.36,162 The 10% to 15% of the U.S. population once infected with E. histolytica has decreased to 1% to 5% overall, primarily because of adequate water and sewage treatment.177,188 Between 1946 and 1980, six waterborne outbreaks of amebiasis were reported in the United States.199,209 Amebiasis accounts for less than 1% of TD.162,292 The pathogenicity of E. histolytica is not well understood.162,292,333 Invasion may be a function of motility, soluble toxins, cysteine protease, or lytic enzymes. The cecum and ascending colon are most frequently involved, followed by the rectum and sigmoid colon. Five different lesions of increasing severity can be distinguished in the colon: (1) diffuse inflammation with cellular infiltrate and an intact epithelium, (2) superficial erosions, (3) early invasion followed by shallow ulceration, (4) late invasive lesions forming the classic flask ulcers with skip lesions, and (5) loss of mucosa and muscularis, resulting in exposure of underlying granulation tissue. Extraintestinal spread is hematogenous. Abscesses containing acellular debris develop primarily in the liver but may involve the brain and lung.101,162,292 Although 80% to 99% of infections result in asymptomatic carriers, a spectrum of GI diseases may result. The incubation period ranges from 1 to 4 months, depending on the area of endemicity. Most often, colonic inflammation without dysentery causes lower abdominal cramping and altered stools, sometimes containing mucus and blood.162,258 Weight loss, anorexia, and nausea may be present. Symptoms commonly fluctuate and continue for months. The subacute infection may evolve into a chronic, nondysenteric bowel syndrome, with intermittent diarrhea, abdominal pain, weight loss, and flatulence. Dysentery may develop suddenly after an incubation period of 8 to 10 days

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or after a period of mild symptoms. Affected persons may have frequent passage of bloody stools, tenesmus, moderate to severe abdominal pain and tenderness, and fever. There is considerable variation in severity.292 Humoral antibodies increase with invasive disease and persist for long periods. Although they do not protect against reinfection or bowel invasion, they show antiamebic action in vitro and may prevent recurrent liver infection, which is uncommon. Once the infection is cleared, recurrence is unusual, but asymptomatic cyst shedding and active GI illness may persist for years, indicating lack of consistent immune response in the intestinal lumen.162,292 The fatality rate for amebic dysentery and its complications is about 2%. Complications of intestinal involvement develop in 2% to 20% of cases and include perforation, toxic megacolon, and ameboma. An ameboma is an annular inflammatory lesion of the ascending colon containing live trophozoites. It may be improperly diagnosed as a pyogenic abscess or a carcinoma. A postdysenteric syndrome can occur in patients with acute amebic dysentery and can be confused with ulcerative colitis. The diagnosis of intestinal amebiasis is made by identification of cysts or trophozoites in stool. Mucus from fresh stools or sigmoidoscopic scrapings and aspirates mixed with a drop of saline may show trophozoites if examined within an hour. For delayed examination, stool must be preserved in polyvinyl alcohol or other fixative and may be examined later with trichrome stain.162,292 The same limitations and problems discussed with Giardia apply to E. histolytica. Fecal shedding of cysts is irregular. Three stools on alternate days identify most infections. Overdiagnosis may result from misidentification of leukocytes. Sigmoidoscopy or colonoscopy is useful for viewing the pathologic lesions and obtaining selective samples of mucus and biopsies of mucosal ulcers, which usually contain organisms.112 Finding cysts does not confirm the diagnosis of symptomatic intestinal amebiasis. The key to establishing the diagnosis is finding motile trophozoites with ingested red blood cells. Culture techniques have been developed that identify infection in some cases when small numbers of cysts are missed in stool examinations, but these techniques are expensive and time consuming.112 Serologic tests are not useful for identifying asymptomatic carriers but are positive in 85% to 95% of patients with dysentery and 90% to 100% of patients with liver abscess.112,137,248 New antigen detection techniques can differentiate between E. histolytica and E. dispar.158,162,180,292 Recently, PCR techniques have been developed and show greater than 95% sensitivity and specificity.2,109,322 Treatment of amebiasis is based on the location of infection and the degree of symptoms. Medications are divided into tissue amebicides, which are well-absorbed drugs (e.g., metronidazole, tinidazole, emetine, dehydroemetine, chloroquine) that combat invasive amebiasis in the bowel and liver, and poorly absorbed drugs (e.g., iodoquinol, paromomycin, diloxanide furoate) for luminal infections. In general, treatment is effective for invasive infections but disappointing for intestinal colonization. U.S. guidelines suggest that asymptomatic carriers should be treated, because a cyst passer represents a potential health hazard to others, and reinfection in the United States is uncommon. Routine screening of asymptomatic persons of high-risk groups is not cost effective, except perhaps for food handlers and persons returning from extended stay in endemic countries.292

The current drug of choice for asymptomatic carriers is iodoquinol (650 mg three times a day for adults and 40 mg/kg/ day in three divided doses for 20 days for children). Side effects are mild and consist of abdominal pain, diarrhea, and rash. Diloxanide furoate (Furamide) is another drug of choice (500 mg three times a day for adults and 20 mg/kg/day in three divided doses for 10 days for children), but in the United States it is classified as an investigational drug, available only through the CDC. Side effects are limited to flatulence and other mild GI symptoms.124 Paromomycin is also effective (500 mg three times a day for adults and 30 mg/kg/day in three divided doses for 7 days for children). Although metronidazole has been used in asymptomatic carriers with 90% success, most reserve this drug for invasive and symptomatic infections. Invasive disease is treated with a tissue-active drug, followed by a luminal agent (in the same dosages as just listed). For oral therapy, metronidazole is the drug of choice (750 mg three times a day for adults and 50 mg/kg/day in three divided doses for 5 to 10 days for children), followed by iodoquinol. Tinidazole (1000 mg twice daily for 3 days) appears to be effective and is well tolerated for intestinal and hepatic amebiasis. Emetine and dehydroemetine (1 mg/kg/day, maximum 90 mg/day) are used parenterally in severe cases of amebiasis, primarily extraintestinal, followed by iodoquinol for 20 days. These two drugs have frequent systemic side effects, including the development of cardiac arrhythmias requiring hospitalization for cardiac monitoring. Because this class of drugs is related to ipecac, the drugs also cause vomiting.198,292 Another species, Entamoeba polecki, although usually nonpathogenic, has been suspected of causing lower intestinal symptoms in sporadic cases involving heavy infection.268 Cysts are passed in stool and may be confused with E. histolytica, which they closely resemble. Successful resolution of symptoms has been reported with metronidazole followed by diloxanide furoate in the same dosages as for amebiasis and balantidiasis.

Cryptosporidium Cryptosporidium is a coccidian parasite that belongs to the phylum Sporozoa. It is a reemergent enteric pathogen in humans. Cryptosporidium parvum, the only human pathogen of this genus, was originally described in 1912 but was first identified in humans in 1976.45,58,59,128,151,234 C. parvum causes a ubiquitous zoonosis with a worldwide distribution. Cryptosporidium infects a wide variety of young animals, including domestic calves, birds, piglets, horses, pigs, kittens, puppies, and wild mammals, such as raccoons, beavers, squirrels, and coyotes.45,128 The prevalence of infection in human populations varies from 0.1% to 3% in cooler, developed countries (in Europe, North America) to 0.5% to 10% in warmer areas (Africa, Asia). The infection has been described in those who have contact with animals, such as veterinarians and farmers; infants in daycare centers; travelers to endemic areas; and patients who have AIDS or who are otherwise immunocompromised. It may infect large numbers of individuals in community-wide waterborne outbreaks.45,59,128 The infective dose of Cryptosporidium for humans is low, similar to that seen with Giardia species. Sporulated oocysts are infective when passed in the stool, so fecal–oral contamination is the mode of transmission.128 The different routes of transmission are waterborne, especially in large community outbreaks; person to person, especially in daycare centers, custodial institutions, and

Chapter 62: Infectious Diarrhea from Wilderness and Foreign Travel hospitals; food-borne, through apple cider, uncooked sausage, and raw milk; sexual, with no association with specific behavior; and zoonotic.45,110,128,194,195 In 1993 in Milwaukee, Cryptosporidium caused the largest waterborne outbreak of protozoal parasites in the United States.203 The pathophysiologic mechanisms of diarrhea and malabsorption are not completely understood. The initial invasion of parasites may activate cellular and humoral immune and inflammatory responses, leading to cell damage with villi atrophy and crypt hyperplasia, ultimately producing malabsorption and osmotic diarrhea.45,75,123,128,235 The clinical manifestations depend on the patient’s immune status, but asymptomatic infection occurs in both normal and immunocompromised hosts.45,128 In immunocompetent persons, the usual incubation period of Cryptosporidium is from 5 to 28 days. Symptoms consist of watery diarrhea associated with cramps, nausea, flatulence, and, at times, vomiting and lowgrade fever. The syndrome is generally mild and self-limited, with a duration of 5 to 6 days in some groups (range, 2 to 26 days). In contrast, immunocompromised hosts experience more frequent and prolonged infections, with profuse chronic watery diarrhea, malabsorption, and weight loss lasting months to years. Fluid losses can be overwhelming in a fulminant choleralike illness, with high mortality. Cyst passage in stool usually ends within 1 week of resolution of symptoms but may persist for up to 2 months after recovery. Reinfection of an immunocompetent person has been documented. Rarely, Cryptosporidium can infect the respiratory system, which may be fatal in the immunocompromised host. The other extraintestinal manifestations relate to involvement of the liver and biliary system, particularly in immunocompromised persons. Cholangitis may not respond to common luminal agents used to treat intestinal cryptosporidiosis, requiring sphincterotomy for therapy.45,128 Diagnosis in initial case descriptions was made by small bowel biopsy, but oocysts can be found in the stools routinely in intestinal infections, even though shedding may be intermittent. Concentration techniques, such as formalin-ether or sucrose flotation, and subsequent staining with modified acidfast, Giemsa, or Ziehl-Neelsen techniques facilitate identification of Cryptosporidium oocysts. The Enterotest is also useful in the diagnosis of cryptosporidiosis. Newer immunologic techniques are faster and have adequate sensitivity and excellent specificity. Several other methods (flow cytometry using monoclonal antibodies, PCR, restriction fragment length polymorphism [RFLP] analysis) have been developed, but their efficacy in the clinical setting is not yet known.39,45,113,128,183,329 No clearly effective treatment has been found for cryptosporidiosis. Because this disease is usually mild and selflimited in immunocompetent hosts, only supportive care is needed. Anticryptosporidial agents, such as paromomycin (500 to 750 mg three or four times a day for 2 weeks), azithromycin (1200 mg daily for 4 weeks), and nitazoxanide (500 mg two times a day for 3 to 14 days)108a may be used in immunocompetent persons with persistent infection and in immunocompromised patients. Paromomycin, azithromycin, roxithromycin, ionophores, sulfonamides, and mefloquine have been tested against cryptosporidiosis, especially in patients with AIDS and chronic diarrheal disease, with variable but generally positive effects.11,45,128,265,286,324 Further studies with these and other new agents, including clinical trials using immunotherapy options, are in progress.

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Isospora belli Isospora belli is a coccidian protozoal parasite. The first description of Isospora was in 1915. More recently, I. belli was identified as the pathogenic species for humans. It is an uncommon cause of diarrhea in humans, but its prevalence, like that of Cryptosporidium, has been increasing in immunocompromised patients.57,123,206,209,323 Humans are the only host (although there are a few reports in dogs), and infections are transmitted by fecal–oral contamination through direct contact of food and water. I. belli is endemic in areas of South America, Africa, and Asia. The prevalence is not precisely known but ranges from 0.2% to 3% in United States patients with AIDS and from 8% to 20% in Haitian and African patients with AIDS. This parasite has also been associated with outbreaks in custodial institutions, in daycare centers, and among immigrants. Infection rates in otherwise healthy persons with diarrhea are usually low. Most cases have been identified in tropical regions among natives, travelers, and the military.123,209 The life cycle and pathogenesis of I. belli are similar to those of Cryptosporidium. The organism invades mucosal cells of the small intestine, causing an inflammatory response in the submucosa and variable destruction of the brush border.123 In immunocompetent persons, the I. belli infection may be asymptomatic or cause mild transient diarrhea and abdominal cramps. Other symptoms include profuse watery diarrhea, flatulence, anorexia, weight loss, low-grade fever, and malabsorption.123 Generally, infection is self-limited, ending in 2 to 3 weeks, but some persons have symptoms lasting months to years, clinically similar to giardiasis. Recurrences are common. Infections in immunocompromised patients tend to be more severe and follow a more protracted course.206 Rarely, acalculous cholecystitis or reactive arthritis has been reported in isosporiasis.21 Diagnosis can be made by identification of immature oocysts in fresh stool. However, excretion may occur sporadically and in small numbers, so concentration techniques are usually required. Staining with modified Ziehl-Neelsen and auraminerhodamine can also be useful. When stools are negative, the organism can be recovered from the jejunum through a biopsy or string test. Unlike the other intestinal protozoa, I. belli may cause eosinophilia.112 Successful treatment has been reported with TMP/SMX (160/800 mg four times a day for 10 days, then twice a day for 3 weeks in normal hosts). Other options are pyrimethamine (75 mg daily for 14 days) with folinic acid, metronidazole, and nitazoxanide (for patients allergic to sulfonamides). In patients with HIV infection, chronic lifetime suppression therapy is indicated with either TMP/SMX (160/800 mg three times a week) or pyrimethamine (25 mg) plus folinic acid (5 mg) daily.108a,123,206

Cyclospora cayetanensis Cyclospora species were first discovered in moles in 1870 and were identified as human pathogens in 1979. They were initially thought to be blue-green algae (cyanobacteria-like organisms).92,114,207,238,288,328 The life cycle and pathogenesis of Cyclospora cayetanensis are not completely understood. The organism has been shown to be an important cause of acute and protracted diarrhea. C. cayetanensis is endemic in many developing countries in all continents, with the highest rates occurring in Nepal, Haiti, and Peru. In the United States, most of the native outbreaks have been from areas east of the

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Rocky Mountains, usually associated with ingestion of contaminated imported raspberries.27,41,92,123,140,141 Fecal–oral transmission also occurs through water and soil.288 Cyclospora infection is closely associated with diarrhea in travelers to endemic areas.92,114,145,207,238,288,328 The onset of diarrhea is usually abrupt, with symptoms lasting 7 weeks or even longer.92,123 In patients with AIDS, the duration may be longer and the severity greater.206 Small spherical organisms can be detected in fresh or concentrated stool, and they show variable staining with acid-fast methods. C. cayetanensis stains best with carbolfuchsin.328 Phase-contrast microscopy and autofluorescence are also useful in the diagnosis.112 A PCR method is still used only for research.209 The treatment of choice is TMP/SMX (160/800 mg four times a day for 10 days). This treatment provides more rapid clinical and parasitologic cure, with fewer recurrences.92,114,207,238,288 In patients with AIDS, chronic suppression with TMP/SMX may be required.206

Miscellaneous Parasitic Agents Microsporidia. More than 100 genera and 1000 species of microsporidia exist in the phylum Microspora. Most species infect insects, birds, and fish. Since the first description in humans in 1985, only 12 species have been reported to infect humans: Enterocytozoon bieneusi, three Encephalitozoon species, three Nosema species, two Trachipleistophora species, Pleistophora, Vittaforma corneae, and microsporidial species. Microsporidia cause a wide spectrum of disease, but only two, E. bieneusi and Encephalitozoon intestinalis, have been found to cause diarrhea in humans.66,123,321,323 Transmission is thought to be fecal–oral or urinary–oral66,67 and the infection zoonotic. Waterborne transmission also occurs.209 Prevalence of microsporidiosis in patients who have AIDS and chronic diarrhea is 7% to 50%.17,67,321 The clinical manifestations of intestinal microsporidiosis are chronic diarrhea, loss of appetite, weight loss, malabsorption, and fever.17,321 Acute self-limited diarrhea has been reported in immunocompetent hosts. Other infections include keratoconjunctivitis, hepatitis, peritonitis, myositis, CNS infection, urinary tract infections, sinusitis, and disseminated disease. Diagnosis involves trichrome staining of concentrated stools or intestinal biopsy sampling, but electron microscopy is considered the gold standard. Immunologic and molecular biologic techniques are still under evaluation.105,321 The most effective drug is albendazole (400 mg twice a day for 2 to 4 weeks). It is effective against most species, but results

are variable with diarrhea from E. bieneusi.68 Other drugs show different efficacy and include thalidomide, fumagillin, atovaquone, metronidazole, furazolidone, azithromycin, itraconazole, and sulfonamides.55,66

Sarcocystis. Few human infections with Sarcocystis have been reported. Infection may be asymptomatic or associated with diarrhea, abdominal pain, nausea, and bloating. Symptoms typically improve within 48 hours of onset of illness. Diagnosis is based on identification of cysts in concentrated feces. No specific treatment has been established, but TMP/SMX and furazolidone have had variable efficacy.280,323 Balantidium. Balantidium coli is a rare pathogen in humans.297,323 Although many aspects of the epidemiology are unclear, pigs appear to be the primary reservoir and source of human infection. Clinical features also resemble amebiasis, with a spectrum including asymptomatic infection, chronic intermittent diarrhea of variable intensity, acute dysentery with mucosal invasion, and, rarely, metastatic abscesses. Diagnosis is made by observing the organism in stool. Trophozoites are seen much more often than cysts. Recommended treatment is tetracycline (500 mg four times a day for 10 days) or metronidazole (750 mg three times a day for 10 days).280,323 Blastocystis. The role of Blastocystis hominis in diarrheal disease is still controversial, although it is often identified in stool samples. B. hominis has not been directly correlated with symptoms,280,323 which could be caused by other undetected pathogens. When found in large numbers as the sole pathogen, B. hominis is suspected as the potential etiologic agent of diarrheal illness. Dientamoeba. Dientamoeba fragilis occasionally causes diarrhea, occurring characteristically in residents of or visitors to developing tropical regions. It may be found in stools of persons without enteric symptoms. Because cyst forms have not been identified, the mode of transmission remains unknown. Illness caused by the parasite typically resembles giardiasis, but treatment of these two parasitic infections is different. Iodoquinol and tetracyclines are effective against D. fragilis.280,323 The references for this chapter can be found on the accompanying DVD-ROM.

Chapter 63: Nutrition, Malnutrition, and Starvation

Nutrition, Malnutrition, and Starvation

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63

E. Wayne Askew

How does it feel to starve? I am hungry. I am always hungry. . . . At times I can almost forget about it but there is nothing that can hold my interest for long. . . . I am cold. . . . My body flame is burning as low as possible to conserve precious fuel and still maintain my life processes. . . . I am weak. I can walk miles at my own pace in order to satisfy laboratory requirements, but often I trip on cracks in the sidewalk. To open a heavy door it is necessary to brace myself and push or pull with all my might. I wouldn’t think of throwing a baseball and I couldn’t jump over a twelve inch railing if I tried. This lack of strength is a great frustration. It is often a greater frustration than the hunger . . . and now I have edema. When I wake up in the morning my face is puffy. . . . Sometimes my ankles swell and my knees are puffy. . . . Social graces, interests, spontaneous activity and responsibility take second place to concerns about food. . . . I lick my plate unashamedly at each meal even when guests are present. . . . I can talk intellectually, my mental ability has not decreased, but my will to use my ability has. Observations by a test subject, Minnesota Starvation Study, after 24 weeks of semi-starvation (1570 kcal/day, 24% weight loss) (In The Biology of Human Starvation, vol. II43)


IMPORTANCE OF NUTRITION IN STRESSFUL ENVIRONMENTS

Nutrition has a profound underlying importance to proper human physiology and functioning on a day-to-day basis in everyday life; it becomes even more important when humans work or recreate in environmental extremes.10 The central role of nutrition is often unappreciated in wilderness expedition planning and may even be thought by some to be of minor importance. Many enthusiasts do not consider food as critical as gear and equipment, medical supplies, physical fitness, and other logistical considerations. In temperate environments, where food and water are plentiful and re-supply is feasible, the importance of nutrition may seem to diminish compared with other aspects of wilderness medicine. However, when a stressful physical environment is superimposed on the physically demanding tasks associated with wilderness activities, the role of nutrition rapidly becomes of prime importance for mainte-

nance of performance and for prevention of disease and injury, as evidenced from the description of Napoleon’s disastrous 1812 winter retreat from Moscow: The ice and deep snow with which the plains of Russia were covered, impeded . . . calorification in the capillaries and pulmonary organs. The snow and cold water, which the soldiers swallowed for the purpose of allaying their hunger or satisfying their thirst . . . contributed greatly to the destruction of these individuals by absorbing the small portion of heat remaining in the viscera. The agents produced the death of those particularly who had been deprived of nutriment. Baron D. J. Larrey, Inspector General, Napoleon’s Military Medical Staff (In Hypothermia and Warfare, Napoleon’s Retreat from Moscow, 181261) Fortunately, situations encountered in wilderness activities are usually less grim than those faced by Napoleon’s army. There is usually some food available, and few enter these environments unprepared. However, misfortune, combined with suboptimal or haphazard nutritional planning, can spell disaster for even the best-prepared adventurer. A wrong turn on the trail, an injury, unanticipated terrain, an unexpected storm, or a downed airplane can deplete or isolate a victim from anticipated food sources. Food becomes an overriding consideration in a survival situation, particularly as the supply is exhausted. Although a shortage of food is certainly of concern, it does not necessarily imply impending disaster. Humans are remarkably adaptable and can subsist on non-ideal dietary patterns for prolonged periods without disastrous effects on health and performance. As long as some baseline level of energy intake is present, at least a minimal intake of vitamins and minerals will be ensured, forestalling the eventual onset of malnutrition and clinical nutrient deficiency states. Hunger is not comfortable; weight loss results, and performance may suffer, but a fooddeprived individual can still function for an extended period of time. One purpose of this chapter is to review some of the consequences of suboptimal nutrition that might be anticipated under various degrees of food restriction. The medical planner might use this information to anticipate limitations in expedition progress or capabilities and to recognize the state of health of victims of starvation or food restriction. Equally important is the proper way to re-aliment a victim after a prolonged period of unintentional starvation. This can be critically important in a rescue situation, where transport of a victim to a medical facility requires several days of refeeding en route.

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Although the goal of expedition food planning is to meet daily energy and micronutrient requirements, it is not always possible to provide optimal nutrition because of logistical or situational constraints. Three nutritional states or situations may be encountered in the wilderness: (1) optimal nutrition for effective functioning in environmental extremes, (2) malnutrition or suboptimal nutrition, and (3) starvation, or lack of nutrition. Dietary planning for both wilderness expeditions and emergencies will be discussed.

Environmental Stress and Nutrient Requirements The physical and physiological condition of an individual (e.g., bodyweight, strength, coordination, fluid and electrolyte balance, and core temperature) plays a significant role in determining nutritional requirements to maintain homeostasis. It also directly influences survival time in the absence of food or water. In the short run, the most important nutrient is water.9 If an adequate supply of water is not available, all discourse on the physiology of starvation and malnutrition is pointless, because death from dehydration will occur prior to depletion of energy stores. Humans can survive food deprivation for extended periods of time, weeks or even months, depending on their level of body fat. A non-obese adult may live as long as 60 to 70 days while fasting in a clinical setting.37 At the end of this time, almost all body fat and a third of the lean body mass would be lost.36 James Scott, a victim of unintentional situational starvation, was marooned in a snow cave in the Himalayas with water but no food. He survived 43 days without food while losing one third of his bodyweight, although he was near death at the time of rescue.67 Death from starvation in non-obese individuals is imminent if approximately 50% of bodyweight has been lost. This usually corresponds to a body mass index (BMI) of 12 kg/m2, although under some circumstances, a BMI of as low as 11 may be encountered prior to death.25 Time to death after complete water deprivation is measured in days—estimates run from 6 to 14 days, depending on the rate of water loss.36 Water is critical because it maintains the homeostasis of the internal environment.9 It provides an aqueous

Increased energy requirements

Increased water requirements

Inappropriate thirst response

Inappropriate appetite response Decreased availability of food

medium to transport heat from cells to blood, to solvate and pass nutrients between blood and cells, to serve as a medium for intracellular reactions, and to transfer metabolic products for redistribution or excretion via urine. Both the quantity of reactants and the volume of fluid in which they are dissolved influence cellular chemical reaction rates; hence, imbalances in hydration status can alter cellular and tissue function, such as the body’s ability to regulate temperature. Muscular contraction is dependent on the transformation of chemical energy (ATP) to mechanical energy. Nearly three fourths of the energy used for muscular contraction is released as heat. Unless localized heat production from metabolism and muscular contraction is dissipated, the heat burden can be structurally damaging to enzymes or other proteins. Water absorbs heat produced at the cellular level and transfers it to the surface of the skin, where it can be dissipated to the external environment. The importance of water is discussed in Chapter 64. The focus here is on energy restriction and assumes an adequate supply of water. For planning purposes, most wilderness expeditions require 3 to 5 L (about 3 to 5 qt) of potable water per person per day. As a result of advances in food processing, preservation, and nutrient fortification, modern camping foods and the military equivalent, field rations, can support health and performance in a variety of temperate environments, even if not consumed to complete caloric adequacy.50 However, nutrition that was marginally adequate in a temperate environment may rapidly become inadequate in wilderness environments characterized by extreme temperatures and terrain.49,51 Rodahl and Issekutz65 state, “While short-term nutritional deficiencies in men at room temperature appear to have little or no detrimental effect on the capacity to do short-term, heavy work, there is a marked reduction in physical work capacity when a nutritional deficiency or nutritional stress is superimposed on a cold stress.” Superimposed stressors, such as extreme heat, cold, altitude, sleep deprivation, physical exertion, and food restriction, influence nutrient requirements7 and can jeopardize performance.10,29,46,49,51,53 The complex interrelationship between environment and nutrition, and its effect on human physiology and performance, is depicted in Figure 63-1. Stressors in the form of environmental extremes can have serious consequences on health and performance.

Extreme environments (heat, cold, altitude)

Negative energy balance

Decreased availability of water Dehydration

Impaired thermoregulation Depleted muscle glycogen Deterioration of fine motor coordination Impaired effectiveness Diminished work capacity

Figure 63-1. The influence of extreme wilderness environments on food and fluid intake and on physical and mental performance. (Redrawn from Askew EW: In Hickson JF Jr, Wolinski I [eds]:Nutrition in Exercise and Sport.Boca Raton, FL, CRC Press, 1989, pp 367–384.)

Chapter 63: Nutrition, Malnutrition, and Starvation Energy and fluid deficits arising from the interaction of environment and nutrition can negatively impact both physical29 and mental53 performance. Volitional physical activity suffers under caloric deprivation. Motivation may be more acutely influenced by undernutrition than actual physical performance is.53 Nutritional deficits may have a greater effect on what individuals are willing to do (i.e., on their perceived mood, symptoms, and self-motivation) than on what they can do (psychomotor performance).71

Nutritional Considerations in Planning for Wilderness Activities Cold and altitude stressors and their influence on macronutrient and vitamin requirements have been a focus of considerable military and civilian research.8 Research conducted primarily in the era since World War II (WWII) and the Korean conflict has established that vitamin and mineral requirements are not significantly increased by cold exposure, although caloric requirements for thermogenesis may be elevated.51 Work in cold environments can be adequately supported by various combinations of fat, carbohydrate, and protein, although certain combinations of macronutrients may be more beneficial than others in helping a person withstand cold exposure.4 As an example, Mitchell and colleagues55 demonstrated that cold tolerance (the length of time body core temperature could be defended during a controlled cold challenge) was favored by previous diets high in fat as opposed to diets higher in carbohydrate or protein. Subsequent research has indicated that the macronutrient source is less important in the cold than consuming enough total calories to support activity and thermogenesis.4,33 However, when wilderness activities shift from a sea-level, cold-weather environment to a moderate- or highaltitude, cold-weather environment, the macronutrient diet should be reconsidered. Fat is an efficient and well-tolerated energy source during relatively low-power-output, cold-weather activities at sea level; however, it is not as well tolerated at high altitude.5 Substituting carbohydrate for fat and, to a certain degree, for protein can theoretically provide metabolic advantages to oxygen economy when an individual is working at altitude.3 Carbohydrate is a more efficient fuel at altitude than fat, because it is already partially oxidized (i.e., it contains a higher ratio of oxygen atoms to carbon atoms) and therefore requires less oxygen to combust its carbon skeleton to CO2, H2O, and energy. Metabolizing carbohydrate for energy requires approximately 8% to 10% less inspired oxygen than is required to obtain a similar amount of calories from fat. A highcarbohydrate diet can reduce the symptoms of acute mountain sickness, can enhance short-term high-intensity work as well as long-term submaximal efforts, and can lower the effective “felt” elevation by as much as 300 to 600 m (984 to 1969 ft) by requiring less oxygen for metabolism. Initial altitude exposure frequently results in anorexia and subsequently reduces energy and carbohydrate intake.20 Anorexia (and thus food intake) usually improves with time and acclimatization (3 to 7 days at altitude), but, depending on the altitude, may never match that at sea level. Weight loss and performance decrements are quite common under these conditions. Carbohydrate supplementation of the diet at elevations exceeding 2200 m (7218 ft) is usually an effective method to increase carbohydrate and total energy intakes.3,20,27 Some,26 but not all,77 studies of carbohydrate supplementation at altitude have demonstrated a decrease in the adverse symptoms resulting

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from acute altitude exposure. Enhancement of short-term, highintensity performance,26 as well as long-term, submaximal performance,3 by carbohydrate supplementation has also been noted in some studies involving altitude exposure. The beneficial effects of carbohydrate at altitude most likely depend on the type of exercise performed (intensity and duration) and the degree of prior muscle glycogen depletion experienced by the test subject. Muscle glycogen is related to the caloric adequacy of an individual’s prior diet; carbohydrate intake usually parallels the dietary intake of the antecedent diet.83 It is reasonable to consume a mixed diet with snacks high in carbohydrate. The most effective form of carbohydrate supplementation is usually liquid beverages; people will drink even when they are reluctant to eat.20,27 Increasing fluid intake along with carbohydrate intake is also beneficial at altitude, where increased fluid losses occur as the result of diuresis and of respiration in the dry (lowrelative-humidity) atmosphere.9 National nutritional recommendations have been established. The dietary reference intakes (DRIs) are reference values for nutrient intakes that can be used to assess and plan diets for healthy people. Publications that list DRIs can be obtained through the National Academy website (http://newton.nap. edu/category.html?id=fn) and the National Institutes of Health website (http://ods.od.nih.gov/Health_Information/Dietary_ Reference_Intakes.aspx). The DRIs include four categories: estimated average requirement (EAR), recommended dietary allowance (RDA), adequate intake (AI), and tolerable upper limits (UL). EAR is the nutrient intake level estimated to meet the needs of 50% of the individuals in a population group. RDA is the nutrient intake level sufficient to meet the needs of 97% to 98% of the individuals in a population group. AI is an estimate of adequate intake when an EAR cannot be established. The AI and the RDA are similar but not identical. The UL is the highest daily consumption level of a nutrient; when the UL is exceeded, the nutrient poses a risk of adverse health effects.

Special Nutritional Requirements for Female Wilderness Travelers Although our understanding of the differences between male and female nutritional requirements is incomplete, sex differences do exist for certain nutrients, such as iron, calcium, folate, and vitamin B6 under normal environmental living conditions.56 Differences are particularly notable for women using oral contraceptives52 and those who are pregnant or lactating.23 The health implications for pregnant travelers planning a trip to altitude are beyond the scope of this chapter; these individuals should consult a knowledgable pediatrician or obstetrician. Investigations of nutritional requirements at environmental extremes have been conducted on men, but comparatively little research has been directed toward women. The few studies that have been done suggest that dietary nutrient intakes of women at moderate altitude are similar to those at sea level,44 implying that specific sex requirements that exist at sea level may be even more important at altitude, particularly if there is scarcity of nutrient-dense foods or if appetite is blunted. Some sex-specific nutrient requirements are known. For example, research conducted in the late 1960s identified that female service members deployed to places at moderate to high altitude required supplemental dietary iron to optimally support the hematopoietic response to hypoxia.34 Subsequently, research on iron require-

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ments and the thermogenic response to cold have also identified iron as a key micronutrient for women in a cold environment.17,48 Women, because of their reduced body size, usually consume fewer total food calories than men. They are therefore at an increased risk for reduced vitamin and mineral intake. Fortunately, the need for these vitamins and minerals (with the exception of iron) is related to lean body mass, and women usually have a lower lean body mass than men. Because the choice of available foods may be limited during expeditions into the wilderness, female travelers should include a multivitamin supplement in their provisions. It should contain at least 50% of the female RDA for iron, zinc, folate, vitamin B6, and calcium. Antioxidant nutrients (see Vitamins and Their Relationship to Health and Physical Performance, later), including extra vitamin C and E and perhaps certain carotenoids, such as lutein and zeaxanthan, provide additional insurance against oxidative stress. The compositions of some typical multivitamin and mineral supplements are shown in Figure 63-2. The values shown reflect the daily value (DV) of the nutrients—that is, the recommended daily amount for most adults needing 2000 to 2500 kcal/day. Multivitamins often contain relatively low amounts of calcium compared with the female RDA of 1000 to 1300 mg/day, so it may be beneficial for female travelers to include an additional bioavailable calcium supplement containing 250 to 500 mg of calcium per dose. Commercially available chocolateor caramel-flavored calcium “chews” are convenient and contain a small amount of carbohydrate, as well as “bonefriendly” nutrients such as vitamins D and K. The U.S. RDA for calcium intake for adults under age 50 is 1000 mg daily, and people over 50 should ingest 1200 mg daily. Calcium supplements are best taken in small (no more than 500 mg) divided doses throughout the day. If an iron supplement is being taken in a multivitamin or by itself, it is best not to take it at the same time as the calcium supplement, because the absorption of each is unpredictable and may be less than optimal in the presence of the other.64 The nutrients in a vitamin–mineral supplement should be present at close to the DV level (100% or less). This ensures an adequate intake of major micronutrients with minimal risk of adverse nutrient interactions. To avoid unpredictable absorption conflicts, such as between iron and calcium, the recommended dose should not be exceeded. Synthetic vitamins are structurally the same as, and cost less than, so-called natural vitamins. Generic brands are also generally less expensive and equally effective. The addition of herbs, enzymes, or amino acids accomplishes little but adds cost. Some supplements containing phytonutrients extracted from plants may be appropriate when the logistics of the trip offer little or no chance to secure fresh fruits and vegetables. A source of information on vitamin and mineral supplements is ConsumerLab, which provides independent test results and information to help consumers and health care professionals evaluate health, wellness, and nutrition products. The results of its tests, including brands that have passed testing, are available at www. consumerlab.com. Supplements can lose potency over time, so check the expiration date on the label. Figure 63-3 provides guidance for reading and interpreting supplement labels. The initials USP (for the testing organization U.S. Pharmacopeia) or words such as “release assured” or “proven release” indicate that the supplement is easily dissolved and absorbed.

Energy: How Critical Is It? When planning for a prolonged wilderness outing, the following question should be asked: “If we run short on food, will we suffer severe consequences in our progress along our route and experience difficulty carrying our heavy packs?” For optimal performance, it is total energy intake, especially carbohydrate intake, that is the key for sustaining high-level work capacity for extended periods. However, performance across a broad spectrum of back-country tasks, including load-bearing work, is not always severely degraded by short periods of suboptimal energy and carbohydrate intake. A review of the effect of energy restriction on military work performance indicated that soldiers can maintain relatively normal work capacities for short time periods (