Clinical update on emergency medical care in the wilderness

Transcription

1 Wilderness and Environmental Medicine. 10,20-24 (1999) CLINICAL UPDATES IN WILDERNESS MEDICINE Clinical update on emergency medical care in the wilderness CAROL S. FEDERIUK, MD, PhD From the Department of Emergency Medicine. Oregon Health Sciences University. Portland. Wilderness emergency medical care differs from urban prehospital care in many ways. Definitive medical care may be up to days away, physician control by radio may be unavailable, limited medical equipment can be carried by rescuers, and the environment may present physical hazards. In addition, illnesses seldom seen in the urban setting, such as acute mountain sickness and frostbite, may be encountered [1]. Despite these obstacles, wilderness emergency medical care is a vital necessity, owing to the large number of people who participate in outdoor activities in the backcountry. The delivery of optimal emergency medical care in remote areas requires knowledge of all aspects of wilderness medicine. First, the epidemiology of wilderness injuries and illnesses must be understood. Defining the types of injuries sustained and the populations at risk is crucial for estimating medical need. Second, the necessary scope of medical response must be determined. The need for medical skills, especially advanced life support (ALS) techniques, must be balanced against the constraints of training and skill maintenance. Finally, this information must be synthesized to design an emergency medical care system that is able to provide effective wilderness care. This clinical update reviews the current medical literature regarding the occurrence of injury and the provision of emergency medical care in the wilderness. The evidence regarding ALS training for wilderness medical providers is also presented. Epidemiology of wilderness injuries The literature contains a limited amount of data regarding injury and illness occurring in US wilderness areas. The acquisition of data on wilderness injuries is complicated by the fact that the events occur in remote areas and may not be reported to a specific agency. An additional obstacle to obtaining data is the lack of comput- '. erized records and databases. Sources for studies of wilderness injuries include surveys of hikers, records from organizations that teach wilderness skills, and National Park Service (NPS) records. Although many older studies concentrate on one wilderness activity, several recent reports have added to the general knowledge base of wilderness epidemiology. The most comprehensive recent study reviewed morbidity and mortality data from eight NPS parks in California over a 3-year period [2]. There were 1708 morbidities with an occurrence rate for nonfatal events of 9.2 per visits. Musculoskeletal and soft tissue injuries accounted for more than 70% of nonfatal events. The lower extremity was the most common site of injury, followed by the upper extremity and head and neck. Most injuries were due to common activities, such as hiking, walking, skiing, and driving. Activities such as rock climbing and wild animal attacks accounted for fewer injuries than assaults and substance abuse. Illnesses, including shortness of breath, pain without trauma, dizziness, vomiting, dehydration, intoxication, anaphylaxis, and altitude illness, accounted for 25% of the incidents. Seventy-eight deaths were reported, reflecting a mortality rate of 0.26 per visits. Cardiac events were the most common cause of death, as is true nationally. The next most frequent causes of death were drowning, falls, and motor vehicle accidents. Environment-related incidents such as avalanche and shark attack, accounted for less than 4% of all mortalities. The study does not report the proportion of medical emergencies that took place in the backcountry versus near roads. Thus, the proportion of deaths that occurred in park visitors who did not venture into remote areas is unknown. The authors note that collection of data for this study was timeconsuming and difficult, because NPS records are neither computerized nor kept in regional or national databases. Several studies of wilderness injuries have centered on activities oforganizations that teach outdoor activities and skills. A 5-year prospective study was carried out to

2 Clinical update determine injury patterns and occurrence rates among students and instructors of National Outdoor Leadership School (NOLS) courses [3]. Activities of participants ranged from rock climbing to expedition mountaineering, Nordic skiing, and water sports, including kayaking and sailing. The injury rate was 2.3 per 1000 person days of exposure. Sprains, strains, and soft tissue injuries accounted for 80%, and fractures and dislocations comprised 5% of the 839 injuries. The illness rate was 1.5 per 1000 person-days of exposure. Diarrhea and viral illnesses accounted for 60% of the illnesses. Environmental illnesses, such as acute mountain sickness, heat illness, and hypothermia were relatively uncommon. Evacuations were required in 43% of the incidents, but only 2% of victims were unable to evacuate under their own power. Sprains, strains, and fractures accounted for most of the evacuations, along with two cases of altitude illness and three other unspecified illnesses. Incidents requiring evacuation occurred at the rate of 1.8 per 1000 person-days of exposure. There was one fatality from rock fall, for a death rate of 0.28 per person-days of exposure. Two studies of participants in US Outward Bound schools have been performed. Self-reported injury and illness data were collected from participants at the end of 23-day alpine courses at the Colorado Outward Bound school [4]. Course activities included backpacking, rock climbing, and peak ascents. Of the 343 participants, 85% to 94% sustained an injury and 69% became ill during their wilderness experience. Lacerations, blisters, and bruises were the most common injuries. Headache, diarrhea, and abdominal complaints were the most common illnesses. Only 10% of females and 5% of males sustained injuries serious enough to result in loss of participation. An earlier retrospective review of the safety reports of five US Outward Bound schools determined injury rates associated with wilderness education [5]. The Outward Bound schools offer courses that include hiking, backpacking, mountaineering, canoeing, sailing, crosscountry skiing, and caving. Over a lo-year period, injuries occurred at a rate of 0.75 per 1000 student-days of exposure, somewhat lower than that in the NOLS study. Sprains, contusions, and lacerations were common in all of the schools. Infections and gastrointestinal problems were also seen frequently. The evacuation rate was not reported in this study. However, it is noted that the course group is responsible for transporting injured students to an area accessible to transportation, and helicopters are used only for life-threatening injuries. The injuries and illnesses of backpackers have been addressed in several studies. A field survey of backpackers in Yosemite National Park was performed in 1994 to assess the emergency preparedness of wilderness hikers [6]. Of the 319 backpackers who participated, 18 (6%) reported having to shorten their trip for health reasons. Illnesses, such as upper respiratory infections, and fatigue accounted for half of the cases. Injuries, including ankle sprains, blisters, and shoulder injuries, along with one instance of hypothermia, accounted for the remaining cases. Since this survey was carried out at campsites in the backcountry, injuries requiring immediate medical attention or evacuation were not captured. Backpackers who completed a hike of the 2100-mile Appalachian trail were surveyed by mail to assess their health care needs [7]. Injury or illness was experienced by 82% of the 219 participants. Musculoskeletal complaints were most common (62%), followed by minor trauma (17%), such as lacerations and abrasions. Medical attention was sought for 25% of the injuries reported, most commonly for sprains, contusions, fractures, and lacerations. Three hikers required hospitalization for their injuries. Diarrhea was experienced by 63% of hikers during the course of the trip. Respiratory complaints were experienced by 10% and allergic reactions by 3% of hikers. This study included only hikers who completed the trail; thus, any hikers with injuries preventing completion of the trip would not have been surveyed. Wilderness emergency medical care Wilderness emergency medical care may be provided by a variety of individuals and groups, such as other wilderness users, search and rescue organizations, and ski patrollers. The level of medical skill in the United States commonly ranges from first aid knowledge to paramedic. In some areas, responders may be required to complete a specific wilderness emergency medical technician (EMT) course [1]. Emergency physicians are used less frequently in wilderness areas in the United States than in more highly populated countries, such as Switzerland [8]. The data in the medical literature regarding emergency medical care in the North American wilderness are limited to a few studies from US National Parks and wilderness areas and a Canadian military study. These studies are all unique in that the emergency responders in each system have different levels of training and different protocols. A 5-year retrospective study described the experiences of backcountry paramedics in Oregon [9]. The Reach and Treat (RAT) team paramedics provide advanced life support care in the wilderness area that surrounds Mt. Hood, Oregon. Their scope of practice includes all paramedic skills, as well as treatment of altitude illness and field reduction of extremity dislocations. The RAT team was involved in 114 missions during the study period, 21

3 22 averaging 22 wilderness calls per year. Of the 74 patients treated, 55 (90%) received ALS care. Advanced life support care was defined as starting intravenous catheters, fluid administration, medication administration, and endotracheal tube placement. Eight patients were intubated, four with the assistance of paralytic agents. Fiftytwo patients had an intravenous line established, 24 patients received morphine sulphate, and 13 received droperidol. The most common injuries were to the head and extremities. The most common illness was hypothermia, and cardiopulmonary resuscitation was performed twice. The RAT team is also used on urban calls (over 95% of all calls), allowing the paramedics to maintain their ALS skills. The experiences of Canadian Forces search and rescue technicians (SAR Techs) were described in another recent article [10]. The SAR Techs are used as first responders to both civilian and military accidents and to rescue scenes in Canada. Despite undergoing only 8 weeks of medical training, the SAR Techs have a broad scope of practice, which includes intravenous therapy, medication administration, splinting, oropharyngeal airway and respiratory bag/mask use. Endotracheal intubation skills are not included. The SAR medical action reports from over a 4-year period were retrospectively analyzed to determine the adequacy of the medical training. Of the 272 cases treated, 56 cases required advanced medical intervention techniques, which were defined to include oropharyngeal airways (seven cases), pneumatic shock trousers (five cases), cardiopulmonary resuscitation (two cases), medication administration (41 cases), urinary catheterization (one case), and cricothyroidotomy and needle thoracostomy (zero cases). Trauma calls comprised over half of all cases. Nineteen patients received morphine, five received nitroglycerine, one diazapam, one naloxone, and one subcutaneous epinephrine. The authors felt that endotracheal intubation skills would not have altered the outcome of the two patients who underwent cardiopulmonary resuscitation. It is not reported whether the other five patients who required oropharyngeal airways had any respiratory complications. Two studies of wilderness emergency medical services in Sequoia and Kings Canyon National Parks have been published. Prehospital care providers in this system are first responders, basic EMTs (EMT-Bs), or parkmedics (EMT-intermediate with an extended scope of practice). One study reported the results of administration of epinephrine to patients by NPS rangers with EMT-B training [11]. A specific protocol for subcutaneous epinephrine use was implemented after an epinephrine training course was completed by all EMT-Bs. Eight cases involving the use of epinephrine by EMT-Bs were Federiuk documented during a l5-month period. Clinical improvement was noted in all cases, and there were no deaths. One patient was reported to be in extremis and might have died without administration of epinephrine. The only complication was one case of near syncope. Another study from Sequoia-Kings Canyon National Parks reports on the parkmedic program [12]. Parkmedics are rangers with at least 1 year's experience as an EMT, who undergo 120 hours of didactic training followed by emergency department experience and a prehospital internship. Parkmedics must pass the national EMT-intermediate examination, but have additional training and an expanded scope of practice. Parkmedic training includes use of military antishock trousers (MAST), the esophageal obturator airway, and intravenous medication. They may administer medications such as diazapam, nitroglycerine, epinephrine, and morphine. Over a I-year period, the service handled 434 calls. Extremity trauma was the most common complaint, followed by head trauma. The most common diagnoses were abrasions and lacerations, and minor extremity trauma. These results are similar to those of the recent California National Parks study previously discussed. Forty-four patients 00%) received ALS care. The most common ALS interventions were administration of intravenous lactated Ringer's solution and 50% dextrose (D50) solution. Seven patients were treated with intravenous medications: furosemide (n == 1), diazapam (n = 1), naloxone and D50 (n == 1), D50 (n == 1), lidocaine (n == 1), atropine (n == 1), and sodium bicarbonate (n == 1). There were three fatalities, including two cardiac arrests and one drowning. The parkmedics arrived on the scene of both cardiac patients within 6 minutes. The patients were hypotensive and arrested after the arrival of parkmedics. The parkmedics at Sequoia-Kings Canyon National Parks are not routinely trained in advance cardiac life support, and intubation and defibrillation are not listed in the description of their scope of practice. It is unknown whether additional interventions would have altered the outcome in these patients. Discussion The epidemiologic data reviewed here reflect both selfreported and emergency medical responder-reported injury data. The self-reported data, such as those from backpackers, described mostly benign illnesses and injuries that generally did not impact the emergency medical services (EMS) system. Although not reflective of serious incidents, this information has useful applications, such as in the design of first aid kits. The EMS data capture more critical wilderness incidents. Most seriously ill or injured patients will eventually be trans-

4 Clinical update ported by an EMS agency to an emergency department. Auerbach [13] has proposed a national database for the collection of field run reports, while Martinez [14] has advocated an emergency department database. These databases would be useful in determining standards of care needed in the wilderness and in the training of wilderness medical care providers. In addition, analysis of epidemiologic data is an excellent tool for the identification of teaching points for injury prevention. The epidemiologic data presented in these studies suggest that musculoskeletal injuries comprise the majority of wilderness injuries. Sprains, strains, soft tissue injuries, lacerations and abrasions, and fractures were common in all studies. Thus, wilderness medical responders should be well versed in the management of these injuries. In both the Canadian SAR Tech study and the Mt. Hood RAT team study, morphine was the most common medication administered, suggesting that narcotic pain relief has a place in wilderness medicine. Further studies may better define the need for other advanced skills, such as reduction of extremity dislocations and wound management. The pattern of wilderness illnesses differed between outdoor activity participants and National Park visitors. Diarrhea and viral illnesses were most common in the outdoor course participants. In the National Parks, other complaints, such as cardiac distress, dizziness, and shortness of breath, occurred more frequently. In the Mt. Hood study, the most common illness was hypothermia. There are several explanations for these results. The Mt. Hood paramedics generally respond to backcountry calls that require medical care and evacuation. The NPS data report only incidents serious enough for assistance to be requested. The outdoor school and backpacking data reflect more self-reported problems for which outside assistance may not have been needed. Therefore, different degrees of injury severity were captured. It is likely that these results also reflect the phenomenon of "front country" versus backcountry events. Front country calls have been defined as those accessible by land vehicle [15]. Visitors to the National Parks may include the elderly and persons in poor health who drive to the park and never venture into the backcountry. In contrast, most participants in the outdoor courses were young healthy individuals, who were able to hike into the backcountry [3]. The Mt. Hood patients represented young injured patients, who were unable to self-evacuate from remote areas. Thus, the epidemiology of National Park illnesses may more closely resemble urban patterns than backcountry patterns. The data on advanced medical care in the wilderness suggest that subcutaneous epinephrine is an important intervention. The medication can successfully be admin- istered by EMT-Bs under a strict protocol with minimal risk to patients and potential life-saving benefits. The data regarding other ALS interventions are less clear. Intubation is the definitive method of airway management for increasing oxygenation and preventing aspiration in patients with respiratory failure or loss of consciousness. In the studies reviewed here, airway management was a skill that was used infrequently. In the Mt. Hood study, only eight patients (7%) were intubated on wilderness calls in 5 years. Four of these patients required paralysis for the procedure. There were no reported complications of intubation. In the Canadian SAR study, seven patients (3%) received oropharyngeal airways over 4 years. The authors mentioned that no patient outcome was altered because of lack of intubation. However, most patients who tolerate an oropharyngeal airway do not have a gag reflex and are at risk for aspiration. These patients likely could have tolerated a more definitive airway, such as an esophageal obturator airway or dual lumen device. Despite inclusion of the esophageal obturator airway in the scope of practice of the Sequoia-Kings Canyon park medics, there were no reported uses of the device, even in the cardiac arrest patients. The argument can be made that intubation requires specialized training and repeated practice to maintain proficiency, and that the call volume of many wilderness response systems is insufficient to maintain skill levels. In addition, the complications of missed intubation, such as esophageal intubation, may result in worse patient outcomes than alternative airway management techniques. Also, the rescue team may not have the resources to manage a ventilated patient during a prolonged evacuation. On the other hand, lack of a patent airway can quickly result in hypoxia and death. The use of alternative airways, which require less training and have fewer complications than endotracheal intubation, should be considered for nonparamedics. Additional studies are needed to further evaluate the complications of airway management in the wilderness. Use of defibrillation was not reported in any of the studies, although all of the EMS studies reported treating cardiac arrest victims. Defibrillation can be a life-saving procedure if performed early in cardiac arrest. The issues of importance in deciding whether to use defibrillators are the presence of an at-risk patient population, such as the front country park visitors; scene response times; and evacuation times. Obviously, these devices cannot be carried easily in the backcountry. Defibrillators may be life-saving instruments, however, in wilderness areas of high visitor concentration and good accessibility by road or helicopter. Training issues can be minimized through the use of automatic external defibrillators. 23

5 24 The current studies of wilderness medical care do not provide outcome data regarding the benefits of ALS treatment in the wilderness. This omission is not unexpected since little is known about whether urban ALS interventions improve outcomes. Pending further research, common sense should dictate the design of a wilderness EMS system. Common injuries and illnesses, response times, available methods of evacuation, and available training and equipment are all important factors in directing the medical training of wilderness responders. References 1. Bowman WD. The development and current status of wilderness prehospital emergency care in the United States. J Wilderness Med. 1990;1: Montalvo R, Wingard DL, Bracker M, Davidson TM. Morbidity and mortality in the wilderness. West J Med. 1998; 168: Gentile DA, Morris JA, Schimelpfenig T, Bass SM, Auerbach PS. Wilderness injuries and illnesses. Ann Emerg Med. 1992;21: Twombly SE, Schussman LC. Gender differences in injury and illness rates on wilderness backpacking trips. Wilderness Environ Med. 1995;4: Paton Be. Health, safety and risk in Outward Bound. J Wilderness Med. 1992;3: Federiuk 6. Kogut KT, Rodewald LE. A field survey of the emergency preparedness of wilderness hikers. J Wilderness Med. 1994;5: Crouse BJ, Josephs D. Health care needs of Appalachian Trail hikers. J Fam Pract. 1993;36: Durrer B. Rescue operations in the Swiss Alps in 1990 and J Wilderness Med, 1993;4: Schmidt TA, Federiuk CS, Zechnich A, Forsythe M, Christie M, Andrews C. Advanced life support in the wilderness: 5-year experience of the Reach and Treat Team. Wilderness Environ Med. 1996;3: Popp1ow JR. A review of Canadian Forces Search and Rescue Technician medical training and operations, Aviat Space Environ Med, 1996;67: Fortenberry JE, Laine J, Shalit M. Use of epinephrine for anaphylaxis by emergency medical technicians in a wilderness setting. Ann Emerg Med. 1995;25: Johnson J, Maertins M, Shalit M, Bierbaum TJ, Goldman DE, Lowe RA. Wilderness emergency medical services: the experiences at Sequoia and Kings Canyon National Parks, Am J Emerg Med. 1991;9: Auerbach PS. Wilderness medicine epidemiology, J Wilderness Med. 1992;3: Martinez R. Injury control and wilderness medicine: a scientific frontier. J Wilderness Med. 1993;4: , 15. Kaufman TI, Knopp R, Webster T. The parkmedic program: prehospital care in the National Parks. Ann Emerg Med. 1981;10: