Wilderness Medicine



Although many definitions of wilderness medicine have been suggested, one of the most used definitions derives from transport time, and is usually described as longer than one or two hours away from definitive care. This definition suggests an inclusive nature of wilderness medicine which can be superimposed upon other subsets of prehospital care such as austere, expedition, rural EMS, and disaster medicine. In defining it as such, wilderness medicine encompasses quite an area of significance that extends into the very core of emergency medical services.

Much like tactical EMS, wilderness medicine has seen a surge in academic progress recently, and shares the same sense of pride and accomplishment that comes from practicing in a rich, maturing subspecialty. Indeed, advances in the science of wilderness medicine can be applicable to everyday EMS care—from a remote rescue dispatch to an urban medical call.



  • Define wilderness medicine and describe various types and facets.

  • Discuss wilderness search and rescue and discuss essential personnel, specialized techniques/equipment, and proper interface with IC and EMS.

  • Discuss basic principles of operational EMS in austere environments.

  • Contrast philosophies concerning readiness versus improvisation with equipment and supplies examples.

  • Describe types of wilderness medicine practitioners.

  • Discuss wilderness medicine training, certifications, societies, and fellowship status.

  • Define expedition medicine and describe applications of this type of operational medicine.

  • Discuss planning process for medical support of expeditions.

  • Discuss operational concerns that may arise during the expedition and how to respond to these challenges.

  • Briefly discuss contractual arrangements and terms that are important to successful medical support of expeditions.



Although a commonly used definition of wilderness medicine is described above, in practice, the subspecialty tends to be defined using an additional, circumstantial descriptor which helps exclude some of the overlapping scope of other EMS subsets. These descriptors can be based on a type of location such as “in the woods” or “on a mountain,” a type of activity such as hiking or skiing, or a specifically prolonged transport time usually defined as one to two hours.

Further characterization can be made based on the interaction of several of these factors. Commonly, patients are recreating in the wilderness at the time of the illness or injury. For example, snow blindness (UV keratitis) might occur in a mountaineer who has spent significant time on a glacier without eye protection. Although it would be rare, UV Keratitis could conceivably occur in a nonwilderness setting and may not be considered wilderness medicine. Thus this situation is defined as wilderness medicine by the type of injury, the location, and the activity during which it occurred. Many other “typical” wilderness medicine problems can be considered where the illness or injury most commonly occurs in a nonurban area.

Wilderness medicine may also be defined by the need to improvise or use a specialized body of knowledge. For example, the makeshift connection of a Foley catheter to a latex glove creating a hydration reservoir and proctoclysis system which was used to save the life of a critical patient trekking in the Himalayas describes the quintessential anecdote of wilderness medicine practice with improvisation. 1

In summary, there are many factors to consider when defining wilderness medicine, but the most commonly considered ones are location, activity, time to care, and type of injury. Thus a more robust definition has been put forth that wilderness medicine involves “injuries and illnesses caused by the interaction between humans and their natural environment occurring in potentially austere and threatening environments.” 2 Despite these definitions describing wilderness medicine as being borne from the wilderness, there also do exist several common sets of illness and injury germane to wilderness medicine even though they are frequently encountered in the urban setting. The common theme among these involves the direct interaction of humans with their environment. Typical examples are hypothermia, hyperthermia, lightning, and drowning. Toxic exposures to plants and animal-related injuries may also occur in a nonwilderness environment. Animal bites and stings fall under the rubric of wilderness medicine, and are commonly felt to be under the purview of the wilderness medical practitioner.


Given these varying definitions of wilderness medicine as well as the clear overlap with other areas of prehospital care, what makes wilderness medicine unique? There are situations that may be encountered in typical prehospital care, but are more common in the wilderness setting (lightning strike, hypothermia, etc). There are also situations that will never be encountered in urban EMS whereas they are common in wilderness medicine (snow blindness, HAPE). The elements that comprise this austere medical practice environment are some of the key aspects that make wilderness care unique (Box 67-1).

Box 67-1 Unique Factors That Define Wilderness Medicine

  • Lack of resources

  • Effect of environment on the patient

  • Effect of environment on the rescuers

  • Transport logistics



While national and state guidelines list specific equipment that should be stocked on any registered ambulance there is no definitive list for the wilderness rescuer. Furthermore much of the equipment that is considered commonplace or even essential to typical prehospital care may be difficult or impossible to utilize in the wilderness setting. A typical example of this is tanked oxygen which is administered to a majority of EMS transported patients; however, bringing oxygen to a patient in the wilderness is rarely possible. Only small tanks are light enough to be transported and these would be empty so quickly as to be nearly useless in most scenarios. Another classic example is electronics. While GPS and computer documentation is commonplace in the urban or suburban prehospital setting, in the wilderness such limitations as waterproofing and the need for extra batteries often prove prohibitive. The importance of documentation in the backcountry should not be underestimated simply because of the low-tech manner in which it need be performed.



The austere environment may naturally wreak havoc on supplies and equipment, rescuers responding to a patient, and the physiology of the patient as well. In fact, the environment may be an even more important factor on medical supplies, many of which are not designed to withstand extremes of environment. For example, intravenous fluids are of limited benefit in a cold winter type environment due to freezing or their effects on patient core temperature. Conversely many medications degrade with heat and may not function in a hot desert type environment.

Consider the effects of environment on a patient. A middle-aged male who sustains a femur fracture from a fall in an urban setting is rapidly covered with blankets and then moved to a heated ambulance. Wet clothes are removed and warm blankets are added at the hospital. In the wilderness the same patient is forced to lie in the snow for many minutes or even hours awaiting the assistance of his climbing partners. He is then placed on an insulating pad and covered with down, but may spend hours generating his own heat before he is evacuated and offered external warming. Meanwhile blood loss and impending shock are complicated by early hypothermia which provides further physiologic insult to his initial injury.

Environmental factors affect rescue personnel as well. Cold hands lack dexterity, making technical skills such as IV starts or laceration repairs very difficult. Extremes of temperature limit work performance of rescue personnel who must spend time and energy caring for themselves to prevent hyper- or hypothermia in the rescuers. This need to consider the health and safety of the rescuers often takes significant time during a rescue and requires considerable pre-rescue preparation.



As can be expected, transport times are significantly protracted and can be divided into two portions: evacuation and transport. The primary portion, evacuation, is the wilderness-specific portion and is laid out in Figure 67-1; this is followed by a more traditional ground or air-based transport to the hospital. Oftentimes the difficulty of moving the patient imparts extra risk to the providers, such as a patient injured on a mountain that requires rappelling to descend. Because of the added complexity, more resources and certainly more time are required for evacuation than urban- or suburban-based transport. 3 This added time has given birth to the concept of the “Golden Day,” which replaces the traditional “Golden Hour” that is so central to front-country EMS (Figure 67-1).

FIGURE 67-1.

Rescue and evacuation.

Similar to EMS transport priorities, evacuations can be described by their priority and acceptable risk to effect that evacuation. Emergent evacuation is the type most familiar to the EMS or prehospital provider as it references the situation when a patient must be brought from the backcountry to definitive care as soon as possible and even a relatively high risk rescue may be acceptable. This may range from patients with environmental injuries (HACE) to toxin exposures (snake bites) to medical problems (ACS/MI). A convenient evacuation is undertaken when a patient has a condition that warrants termination of their involvement in the trip and further care in the urban setting but may occur in a more time convenient manner such as after a storm or in the comfort of daylight. Typical examples of these situations are nonimproving gastroenteritis or an expanding cellulitis.

The number of rescuers is often fewer than one would desire, and the need for rescuers is typically much higher. It is estimated that it will take 6 to 12 rescuers per mile to transport a patient who requires carrying. Thus a 2-mile transport would require at a minimum 12 rescuers, and 4 miles would require 24 to 48 rescuers. Such rescuers may be search and rescue (SAR) team members who are typically volunteers and will be driving in from various locations. Alternatively, the number of rescuers may be limited to the trip or event with which the victim was traveling. In either case, obtaining more rescuers may not be feasible.

Regardless of the number of personnel available the amount of prior preparation required is often much higher than that for street-based prehospital providers. While the medical knowledge may be similar, other skill sets are required to keep the providers functional. These may include rope handling skills, ski skills, avalanche knowledge, desert survival, river travel experience, or boat handling skills on the ocean. The intricate interplay between rescue skills, medical capabilities, as well as operational and survival abilities is also a defining element of wilderness medicine. Training in these specialized rescue skills must be maintained in addition to medical training. 4

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Jan 22, 2019 | Posted by in EMERGENCY MEDICINE | Comments Off on Wilderness Medicine
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