Wilderness medicine is a rapidly evolving field, and has benefitted from expanded research efforts. Within the last decade, the Wilderness Medical Society (WMS) has aggregated research findings and created guidelines on prevention measures and therapeutic options for acute altitude illness, frostbite injuries, heat-related illness, and avalanche and non-avalanche snow burials. As new research emerges, some guidelines have been updated to reflect the most current and sound scientific conclusions.
What’s new in wilderness medicine research?
Frostbite injury, which can cause deep tissue damage in severe cases, is a common occurrence in those who travel to cold climates or high altitudes where temperatures are often below freezing.
Acute altitude illness, a term that encompasses syndromes such as acute mountain sickness (AMS), high altitude cerebral edema (HACE) and high altitude pulmonary edema (HAPE), refers to illness related to ascent to high altitude, which commonly manifests as symptoms of headache, weakness, altered consciousness, and even neurological and cardiopulmonary complications. Optimal strategies to prevent AMS and HACE include gradual ascent, as well the use of acetazolamide and dexamethasone. New evidence has questioned the benefit of budesonide and acetaminophen use, ultimately calling for more conclusive research in the form of large-scale clinical trials. Conversely, hypoxic tents are now recognized as a valid method of pre-acclimatization. Therapeutic strategies for treating AMS and HACE include descent from altitude and supplemental oxygen use, and new evidence has highlighted the potential of continuous positive airway pressure but further research is required. The use of salmeterol nor acetazolamide are no longer recommended by the WMS as a prevention method against HAPE due to accounts of unwarranted side effects.
Frostbite injury, which can cause deep tissue damage in severe cases, is a common occurrence in those who travel to cold climates or high altitudes where temperatures are often below freezing. The WMS has recognized classification of frostbite injuries by the depth of tissue damage as the most appropriate in emergency settings. Updated guidelines also recommend classification by anatomical extent of injury and amputation risk as diagnostic tools within hospital settings. Recommendations for prevention of frostbite injuries include increasing peripheral circulation and protection from the cold. As well, thawing frozen tissue is still identified as the primary therapeutic measure. New evidence has introduced the therapeutic potential of intravenous thrombolytics and iloprost, a potent vasodilator, for treating deep frostbite injuries. Additionally, new guidelines advocate for use of single photon emission computed tomography as means of assessing amputation dimensions in severely injured patients.
With a mortality rate of up to 10%, heat illness can affect people who are exposed to sunlight and high temperatures for a prolonged period of time. Heat illness constitutes a spectrum of disease ranging from heat edema, which is swelling in extremities due to heat exposure, to heat stroke, which is characterized by a core temperature of over 40 degrees Celsius and manifests as neurological abnormalities such as seizure. The most effective way to prevent heat illness is through mitigation planning according to factors such as the intensity and duration of outdoor activities, and the frequency of breaks that prevent an individual from overheating. The most effective field and in-hospital treatment for heat illnesses is cold water immersion therapy, which involves immersion of the body in cold water. In accordance with recent findings, guidelines recognize the detrimental effects of heat illness on the cardiovascular system, and recommend screening for such complications after an episode of fainting/passing out.
With a mortality rate of up to 10%, heat illness can affect people who are exposed to sunlight and high temperatures for a prolonged period of time.
In 2017 the WMS released their first set of evidence-based guidelines on avalanche and non-avalanche snow burial. Avalanche snow burial can have a mortality rate of 70% if the victim is not rescued within the first 15 minutes. As such, the most effective preventative measures include avalanche avoidance, burial avoidance, trauma minimization, and asphyxia avoidance, and it is highly recommended for anyone at risk of avalanche burial to be adequately trained in prevention and escape strategies. Equipment such as helmets, backpacks, and specialized avalanche airbags have shown potential for trauma minimization but require further research to validate their use. Rescue guidelines recommend adherence to algorithms that involve establishing a team and team roles, ensuring their own safety, performing searches with transceivers or other methods, strategic shovelling and extraction of victims. Following rescue, resuscitation guidelines outline conditional protocols for cardiopulmonary resuscitation and advanced life support based on duration of burial, core temperature, obstruction of airway, and return of circulation, followed by trauma and hypothermia care when necessary. Non-avalanche snow burial, which is composed of head-first immersion into tree wells or deep powder snow, is less represented within published literature, prompting guidelines that recommend avoiding outdoor activities near tree wells or deep snow as the most optimal means of prevention.
Future steps and Conclusions
As WMS guidelines are carefully synthesized based on existing literature as well as expert opinion, more representative research with sound methodology of equal strength and quality as randomized controlled trials is needed, specifically for the topics of heat injuries and snow burials, which are two areas where it would be unethical to directly replicate the conditions for research purposes. Along with that, further investigation into adjunctive therapies and prevention strategies – both pharmacologic and non-pharmacologic – is recommended to expand care options.
In 2019, the updated WMS guidelines on the prevention, treatment and long-term management of acute altitude illness, frostbite injuries, and heat illness were published. As well as this, they have reviewed literature pertaining to avalanche and non-avalanche snow burial to generate prevention and treatment guidelines. These graded guidelines, which have been reviewed and graded based on level of supporting evidence as well as their risk to benefit ratio, not only serve as systematically-derived medical recommendations, but also highlight the need for expansion of research efforts to alleviate gaps in knowledge within the field of environmental medical science.