Frostbite

Frostbite is an injury to skin or other living tissue that is allowed to freeze,^[1] commonly affecting the fingers, toes, nose, ears, cheeks and chin.^[6] Most often, frostbite occurs in the hands and feet,^[7][8] often preceded by frostnip, a paling or reddening in an area of skin as its blood vessels constrict that tingles, feels very cold, or simply feels numb.^[9][2][10] This may be followed by clumsiness and white or bluish, waxy-looking skin.^[1][11] Swelling or blistering may occur following treatment.^[1] Complications may include hypothermia or compartment syndrome.^[2][1]

People who are exposed to low temperatures for prolonged periods, such as winter sports enthusiasts, military personnel, and homeless individuals, are at greatest risk.^[7][1] Other risk factors include drinking alcohol, smoking, mental health problems, certain medications, and prior injuries due to cold.^[1] The underlying mechanism involves injury from ice crystals and blood clots in small blood vessels following thawing.^[1] Diagnosis is based on symptoms.^[3] Severity may be divided into superficial (first and second degree) and deep (third and fourth degree).^[2] A bone scan or MRI may help in determining the extent of injury.^[1]

Prevention consists of wearing proper, fully-covering clothing, avoiding low temperatures and wind, maintaining hydration and nutrition, and sufficient physical activity to maintain core temperature without exhaustion.^[2] Treatment is by rewarming, immersion in warm water (near body temperature), or body contact, and should be done only when a consistent temperature can be maintained so that refreezing is not a risk.^[2][1] Rapid heating or cooling should be avoided since it could potentially cause burning or heart stress.^[12] Rubbing or applying force to the affected areas should be avoided as it may cause further damage such as abrasions.^[2] The use of ibuprofen and tetanus toxoid is recommended for pain relief or to reduce swelling or inflammation.^[1] For severe injuries, iloprost or thrombolytics may be used.^[1] Surgery, including amputation, is sometimes necessary.^[1][2]

Evidence of frostbite occurring in humans dates back 5,000 years.^[1] Evidence was documented in a pre-Columbian mummy discovered in the Andes.^[7] The number of annual cases of frostbite is unknown.^[5] Rates may be as high as 40% a year among those who mountaineer.^[1] The most common age group affected is those 30 to 50 years old.^[4] Frostbite has also played an important role in a number of military conflicts.^[1] Its first formal description was in 1813 by Dominique Jean Larrey, a physician in Napoleon's army, during its invasion of Russia.^[1] Frostbite reports were largely military until the late 1950s.^[13]