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Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.

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Frostbite: Latest Updates from the Wilderness Medical Society

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This is the eighth post based upon educational sessions and syllabus material presented at the Wilderness Medical Society Annual Meeting & 25th Anniversary held in Snowmass, Colorado from July 25-30. For this post about frostbite, we are grateful to be offered the wisdom of Luanne Freer, MD, FACEP, FAWM, who founded and directs the Everest Base Camp Medical Clinic, which operates each spring climbing season in Nepal.

From a historical perspective, frostbite has been known since ancient times, with indications of frostbite being present in a 5000-year-old pre-Columbian mummy discovered in the Chilean mountains. Napoleon’s surgeon general, Baron Dominique Larrey, described mechanisms of frostbite in 1812, during his army’s retreat from Moscow. He noted the harmful effects of the freeze-thaw-freeze cycle when soldiers warmed frozen hand and feet over the campfire at night, only to have them refreeze when they were removed from the warmth of the fire.

Frostbite has traditionally been considered a military problem, but it is now also a civilian one, as climbers, adventurers, explorers and others have put themselves into cold environments where they are susceptible to exposure and extremely cold external temperatures. It afflicts predominately males aged 30 to 49 years, attributable more to their activities than to their physiology. Dr. Freer reports that 10 to 15 cases per year require treatment on Everest, which represents 3% of persons who reach the summit.

The anatomy and physiology related to frostbite relate mostly to the organs that become frozen, namely, the hands, feet, nose, and ears. These all contain microsopic junctions between tiny arteries and veins, known as AV anastomoses. Within these junctions, adjustments in diameter and blood flow rates can cause flow to vary, say in the hands from 3 milliliters per minute to 180 milliliters per minute, an amazing 60-fold difference. In a cold environment, the body will sacrifice peripheral blood flow to maintain core temperature. Thus, determined by the temperature, state of hydration, degree of exposure, nervous control, and other factors, the blood flow through exposed skin can drop precipitously, setting the stage for a freezing injury.

Frostbite is tissue freezing and death, created by cellular damage, microscopic blood vessel insufficiency, formation of ice crystals inside and outside of cells, and permanent alteration of cell function, akin in devastation to a very severe burn wound. When frostbite occurs, it may be graded as 1st through 4th degree, depending on the depth, or more simply, as superficial (skin and subcutaneous tissues) or deep (muscle, bones, joints, tendons), which is a simpler classification to remember.

Predisposing factors to frostbite include blood vessel insufficiency, tight boots, trauma, being in a cramped position for a prolonged period, vascular disorders (such as Raynaud’s disease), high altitude, prolonged exposure to cold, wet skin, poor cold-induced vascular dilatation (CIVD can be protective), systemic dehydration, the period immediately after meals when blood is shunted to the gastrointestinal system, tobacco use, alcohol use, previous cold injury, and old age.

Frostbitten tissue is rewarmed in water (gently agitated or stirred, if possible) at around 40 to 42°C (under 44°C) if there is no danger of refreezing the tissue after it is thawed. This usually takes about 15 to 30 minutes. The thaw is completed when the tissue is red or reddish purple, and pliable (soft).Thawed tissue is intensely painful. Rarely, the previously frozen tissue may appear relatively normal; it is usually intensely red, mottled blue, yellowish-white, or “waxy.” Some degree of pain may persist for weeks or months, even after the tissue appears completely dead. The frostbitten limb may be numb or feel clumsy. Approximately 3 hours after the tissue is rewarmed, it begins to swell from edema (tissue fluid). This swelling may last for 5 or more days. Within 10 to 15 days, dead tissue blacken, and begins to turn hard and wither.

If possible, the victim of frostbite should move out of the wind and seek shelter. He or she should be given warm fluids to drink. Boots can be removed, but remember that it may be difficult to put them back on if swelling occurs. Wet gloves and socks should be replaced with dry garments. Ibuprofen 400 mg may be given by mouth. If the feet were frostbitten and sensation returns after rewarming, the victim may walk. If sensation does not return, then bring the victim to the nearest warm shelter, and do not allow walking if at all possible, because the lack of sensation may allow undetected injury, or in the worst case, another episode of freezing, which would be catastrophic to the tissues.

Blisters containing clear or milky-colored fluid is rich in substances that cause inflammation and should be drained, which bloody blisters are felt to be more protective than injurious, and are left intact. Aloe vera gel or lotion should be applied to all frostbitten tissue, blistered or unblistered, as it is felt to have a real anti-inflammatory effect. Continue administering ibuprofen in a dose of 12 milligrams per kilogram (2.2 pounds) of body weight per day.

Upon return to civilization, the victim of frostbite should be referred to a frostbite specialist, who will understand the different options (such as special scans) to determine the extent of the injury, as well as routine and experimental treatments, such as pharmacotherapy, neurostimulation, hyperbaric oxygen therapy, the desirability and timing of surgery, rehabilitation, and so forth.

Prevention of frostbite is essential, and even more important in tissue that has been previously frostbitten, because it is more susceptible to further injury. Methods available to prevent frostbite include, among others, heated insoles for footgear and heated gloves, wearing protective clothing in layers that are loose and heat-insulating, adequate nutrition and hydration, staying dry, wearing mittens instead of gloves, avoiding constrictive clothing and tight boots, and perhaps taking prophylactic aspirin or ibuprofen.

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Dr. Paul S. Auerbach is the world’s leading authority on wilderness medicine.

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