Explore the essentials of Wilderness Medicine and prepare yourself for austere environments as we discuss Altitude Sickness, Frostbite, Animal Bites, Thermoregulation, Wound Care and the proper way to apply a tourniquet.
Thinking about outdoor escapes and vacations now more than ever? Listen as our esteemed guest Dr. Thomas DeLoughery @Bloodman (Oregon Health & Science University) takes us through the fascinating, and at times chilling, world of Wilderness Medicine. This episode will empower you to explore the great outdoors as safely as possible. We discuss the breadth of wilderness medicine, multiple unique clinical entities encountered in austere environments, and practical ways to protect yourself and others on your adventures. This episode is truly wild!
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At its core, wilderness medicine is practicing medicine in an austere environment, including everywhere from space to disaster scenarios. While it has taken on this broad definition over the years, outdoor adventure is the mainstay of wilderness medicine. The Wilderness Medical Society offers fellowships, education, research support, and conferences. Travel medicine is a close sibling of wilderness medicine and has its own organization, the International Society of Travel Medicine.
While there is no shortage of premade wilderness first aid kits, it is worth creating your own to suit your specific needs; a wilderness first aid kit should be tailored to the type of trip, climate of the locale, number of participants, and length of trip. Some of the basics are: analgesia (acetaminophen and NSAIDs), oral rehydration salts, anaphylaxis management (antihistamines and EpiPen®), bandages, gauze/absorbent pads, materials for sprinting (ace bandage), and medicine useful for high altitude (acetazolamide and dexamethasone). Antibiotics can be useful for longer trips, with amoxicillin-clavulanic acid (Augmentin), trimethoprim-sulfamethoxazole (Bactrim), or doxycycline being particularly well suited to treat infected scrapes or UTIs.
Don’t forget to bring your home medications and remind your expedition partners to bring their own home medications. Know how to keep medications, like insulin, safe with changes in temperature and altitude! For example, prevent insulin from freeezing and vent insulin bottles to prevent shattering as pressure changes! Separate guidance exists for hiking with chronic illnesses (Auerbach’s textbook chapter 92 “Older Adults in the Wilderness”).
When going into the wilderness, always prepare for the unexpected. The best wilderness medicine is not practicing wilderness medicine. A common mistake is assuming a best-case scenario and only preparing for such. Be prepared to stay overnight unexpectedly. Another mistake is being too strongly goal directed or cutting corners; too many injuries begin with trying to take a shortcut. Why treat a sunburn when you can wear sun protection? Always bring extra clothing, food, and water. Beware of overreliance on technologies; have the ability to navigate without cell phone reception. Similarly….don’t bring a stethoscope. However, is there a role for POCUS?
Dr. DeLoughery’s expert opinion: “space can be better used for bandaids”.
Sudden altitude ascension (>2500m or 8200ft) without allowing for time to acclimatize can lead to altitude sickness.
Acute mountain sickness (AMS) comprises a constellation of symptoms including headache, nausea, vomiting, and fatigue (Luks et al. 2019). High altitude cerebral edema (HACE) represents a severe form of acute mountain sickness. Risk stratification can be a useful tool to determine who needs altitude sickness prevention (Campbell et al, 2015). Individuals are low risk if they have no history of altitude sickness and gradually ascend to <2800 meters. Moderate risk individuals have a history of AMS and plan on ascending no higher than 2500-2800 m in 1 day. Having a history of AMS and ascending to >2800 m in 1 day is considered high risk. Additionally, ascending >3,500 m in 1 day regardless of AMS history is high risk. HACE affects younger individuals more, perhaps due to behavioral factors or larger baseline brain volume. Gradual ascent as well as sleeping at an altitude below maximum altitude reached during waking hours (“Climb high, sleep low”) are preventative measures. Dr. Hackett, a key researcher in altitude physiology, is also the coauthor on a high yield Up-to-Date article on the subject.
A survey of adults traveling to resort communities in the Rocky Mountains (6300–9700 feet elevation) found that 25% of these individuals developed acute mountain sickness with an odds ratio favoring acute mountain sickness of 3.5 for individuals whose permanent residence was below 3000 feet (Honigman et al 1993). Acute mountain sickness happens at medical meetings, too (Montgomery et al 1989; Dean et al, 1990)!
Acetazolamide speeds acclimatization. 125mg BID helps prevent altitude sickness or HACE (Low et al 2012); continue for 2-3 days after reaching maximum altitude. Acetazolamide 250mg BID can be used for treatment (Luks et al. 2019). However, it may reduce exercise performance.
Dexamethasone can be used for AMS and HACE treatment (4-8 mg q6 hours) as well as prevention in high risk patients or situations (Luks et al. 2019).
Although also caused by altitude, high altitude pulmonary edema (HAPE) is a separate clinical entity than acute mountain sickness/HACE. HAPE has been reported even at altitudes as low as ski resorts. It carries individual susceptibility, and if you have it once, you would likely get it again. There is little consensus on genetic risk factors. Nifedipine can be used for prevention or treatment, working as a pulmonary vasodilator and accentuating hypoxic vasoconstriction (Luks et al. 2019). Treatment can also include a portable hyperbaric bag (ex. The Gamow® bag), which is an inflatable pressure bag that a person can fit inside. The bag can be pressurized to an effective altitude thousands of feet lower than current altitude within minutes.
Hypothermia can be insidious (Dow et al, 2019). Paradoxical reactions can occur as the brain gets cold but one perceives being warm. The adage “cotton kills” is important–cotton saturated by sweat can lose the ability to provide insulation. Shivering increases metabolism five times so the shivering response is important to the body trying to maintain temperature. Make sure your hypothermic patient is well fed so they can generate an adequate shivering response.
Separate a person from the ground to avoid additional temperature loss (by conduction). If their clothing is wet and there isn’t dry clothing available, wrap them in additional insulation to prevent evaporative losses.
Hypothermic patients need to be physically handled very carefully, as cardiac arrest can occur when warm core blood begins to circulate and rapidly cools. Keep them horizontal! Follow the Cold Card.
Frostbite is very common (McIntosh et al, 2019). Frostnip is a superficial injury. Frostbite is tissue damage. At first glance, frostbite does not look bad as it is often just pale hard skin. However, the tissue can then blister and is susceptible to gangrene.
A cycle of thawing-refreezing is bad. Definitive help is important.
The proper way to rewarm is with 40 degrees Celsius warm water to thaw the affected limb. It can be painful. Aspirin and NSAIDS could be useful to deal with pain. There is some thought that the antiplatelet effect prevents thrombosis and further damage, and tPA is being studied as treatment (Hutchinson et al, 2019). There are prediction rules for the ultimate severity of damage (Cauchy et al, 2001), and the acute appearance doesn’t equal final disability.
Heat exhaustion reflects a spectrum of injury related to overheating, starting with heat cramps and heat syncope. Heat stroke is the end stage when people are unable to thermoregulate >104 F with CNS depression (Lipman et al, 2019). End organ damage, including brain, liver, and renal damage, can occur. Medications can predispose, including tricyclics, anticholinergics, amphetamines, ephedra, and antipsychotics. Older patients are prone. Acclimatization, by gradually increasing exercise intensely over a couple of weeks, is warranted.
Drink to thirst to avoid hyponatremia (Bennett et al, 2020). Hyponatremia from excess water intake is more common than dehydration (i.e. hypernatremia) during exercise.
Bat bites are subtle, and rabies can also be transmitted through bat scratches. A high percentage of bats carry rabies. If bitten/scraped, start by washing the site with soap and water then pursue appropriate post-exposure prophylaxis. The CDC has a list of local contacts to help in the case of possible rabies exposure. Dr. DeLoughery has personal experience with bat bites.
Approximately nine thousand snake bites present to EDs in the USA annually, with about a third reflecting bites from venomous snakes (Kanaan et al, 2015). However, very few people die of snake bites in the USA annually compared to other countries. Wikipedia keeps a list of fatal snake bites in the United States. Most bite victims are young men 18-34 years old bitten on an extremity because they were messing with the snake…often while intoxicated. Even decapitated or dead snakes can bite and release venom due to residual bite reflexes. Snakes, young men, and alcohol are the three component parts of the DeLoughery Triad of Doom. Taking a picture of the snake after a bite can provide information to the healthcare providers. Antivenom is the only definitive therapy; first aid in the field should not delay transfer to a facility where antivenom can be administered. There can be cardiac effects, but complications are usually DIC and thrombocytopenia. Cobras and coral snakes have neurotoxic venom.
Expert opinion: don’t mess with snakes.
Although simple, old fashioned direct pressure is a simple and often effective method to achieve hemostasis, tourniquets may have a role in acute bleeding (Drew et al, 2015). They need to be tight enough to stop arterial bleeding in addition to venous bleeding. Instructional videos abound. After around 2 hours, remove to see if the bleeding has stopped. Local hemostatics like QuikClot ®, which are bandages impregnated with procoagulants, are available. For big dirty wounds, prophylactic antibiotics can be used, especially if there is going to be a delay to definitive care.
Clean wounds with soap and water!
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Listeners will learn the basics of wilderness medicine and how to approach a few common conditions.
After listening to this episode listeners will…
Dr DeLoughery reports no relevant financial disclosures. The Curbsiders report no relevant financial disclosures.
O’Glasser AY, Gorth D, Deloughery T, Williams PN, Watto MF. “#242 Wilderness Medicine: Prfor Disaster”. The Curbsiders Internal Medicine Podcast. http://thecurbsiders.com/episode-list Original air date November 16, 2020.
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