Frostbite

Areas that are usually affected include cheeks, ears, nose and fingers and toes. Frostbite is often preceded by frostnip. The symptoms of frostbite progress with prolonged exposure to cold. Historically, frostbite has been classified by degrees according to skin and sensation changes, similar to burn classifications. However, the degrees do not correspond to the amount of long-term damage. A simplification of this system of classification is superficial (first or second degree) or deep injury (third or fourth degree). • In the weeks after injury, pain persists and a blackened crust (eschar) develops. • There can be long-term ulceration and damage to growth plates. Fourth degree • In fourth-degree frostbite, structures below the skin, like muscles, tendon, and bone, are involved. • Early symptoms include a colorless appearance of the skin, a hard texture, and painless rewarming. • Later, the skin becomes black and mummified. The amount of permanent damage can take one month or more to determine. Autoamputation can occur after two months. and was unable to properly dry feet. ==Causes==

Risk factors The major risk factor for frostbite is exposure to cold through geography, occupation and/or recreation. Inadequate clothing and shelter are major risk factors. Frostbite is more likely when the body's ability to produce or retain heat is impaired. Physical, behavioral, and environmental factors can all contribute to the development of frostbite. Immobility and physical stress (such as malnutrition or dehydration) are also risk factors. Disorders and substances that impair circulation contribute, including diabetes, Raynaud's phenomenon, tobacco and alcohol use. Homeless individuals and individuals with some mental illnesses may be at higher risk. ==Mechanism==

Freezing In frostbite, cooling of the body causes narrowing of the blood vessels (vasoconstriction). Prolonged exposure to temperatures below may cause ice crystals to form in the tissues, and prolonged exposure to temperatures below may cause ice crystals to form in the blood. Ice crystals can damage small blood vessels at the site of injury. Typically, prolonged exposure to temperatures below may cause frostbite. Rewarming Rewarming, though vital, causes tissue damage through reperfusion injury, which involves vasodilation, swelling (edema), and poor blood flow (stasis). Platelet aggregation is another possible mechanism of injury. Blisters and spasm of blood vessels (vasospasm) can develop after rewarming. Pathophysiology The pathological mechanism by which frostbite causes body tissue injury can be characterized by four stages: Prefreeze, freeze-thaw, vascular stasis, and the late ischemic stage. • Prefreeze phase: involves the cooling of tissues without ice crystal formation. • Freeze-thaw phase: ice-crystals form, resulting in cellular damage and death. • Vascular stasis phase: marked by blood coagulation or the leaking of blood out of the vessels. • Late ischemic phase: characterized by inflammatory events, ischemia and tissue death. == Diagnosis ==

Frostbite is diagnosed on the basis of signs and symptoms as described above, and by patient history. Other conditions that can have a similar appearance or occur at the same time include: • Frostnip, a precursor to frostbite with a similar appearance, but without ice crystal formation in the skin. Whitening of the skin and numbness reverse quickly after rewarming. • Trench foot, damage to nerves and blood vessels that results from exposure to cold wet (non-freezing) conditions. This is reversible if treated early. • Pernio or chilblains, inflammation of the skin from exposure to wet, cold (non-freezing) conditions. They can appear as various types of ulcers and blisters. It does not require exposure to cold to develop. • Levamisole toxicity, a vasculitis that can appear similar to frostbite. == Prevention ==

infographic video about frostbite prevention The Wilderness Medical Society recommends covering the skin and scalp, taking in adequate nutrition, avoiding constrictive footwear and clothing, and remaining active without causing exhaustion. Supplemental oxygen may also be of use at high elevations. Repeated exposure to cold water makes people more susceptible to frostbite. Additional measures to prevent frostbite include: • Avoiding temperatures below −23 °C (-9 °F) • Avoiding moisture, including in the form of sweat and/or skin emollients • Avoiding alcohol and drugs that impair circulation or natural protective responses • Layering clothing • Using chemical or electric warming devices • Recognizing early signs of frostnip and frostbite ==Treatment==

Individuals with frostbite or potential frostbite should go to a protected environment and get warm fluids. If there is no risk of re-freezing, the extremity can be exposed and warmed in the underarm of a companion or the groin. If the area is allowed to refreeze, there can be worse tissue damage. If the area cannot be reliably kept warm, the person should be brought to a medical facility without rewarming the area. Rubbing the affected area can also increase tissue damage. Aspirin and ibuprofen can be given in the field The first priority in people with frostbite should be to assess for hypothermia and other life-threatening complications of cold exposure. Before treating frostbite, the core temperature should be raised above 35 °C. Oral or intravenous (IV) fluids should be given. According to Handford and colleagues, "The Wilderness Medical Society and State of Alaska Cold Injury Guidelines recommend a temperature of 37–39 °C, which decreases the pain experienced by the patient whilst only slightly slowing rewarming time." Warming takes 15 minutes to 1 hour. The faucet should be left running so the water can circulate. Rewarming can be very painful, so pain management is important. Blood vessel dilating medications such as iloprost may prevent blood vessel blockage. A systematic review and metaanalysis revealed that iloprost alone or iloprost plus recombinant tissue plasminogen activator (rtPA) may decrease amputation rate in case of severe frostbite in comparison to buflomedil alone with no major adverse events reported from iloprost or iloprost plus rtPA in the included studies. Surgery Various types of surgery might be indicated in frostbite injury, depending on the type and extent of damage. Debridement or amputation of necrotic tissue is usually delayed unless there is gangrene or systemic infection (sepsis). If symptoms of compartment syndrome develop, fasciotomy can be done to attempt to preserve blood flow. == Prognosis ==

Tissue loss and autoamputation are potential consequences of frostbite. Permanent nerve damage including loss of feeling can occur. It can take several weeks to know what parts of the tissue will survive. == Epidemiology ==

There is a lack of comprehensive statistics about the epidemiology of frostbite. In the United States, frostbite is more common in northern states. In Finland, annual incidence was 2.5 per 100,000 among civilians, compared with 3.2 per 100,000 in Montreal. Research suggests that men aged 30–49 are at highest risk, possibly because of occupational or recreational exposures to cold. == History ==

Frostbite has been described in military history for millennia. The Greeks encountered and discussed the problem of frostbite as early as 400 BC. Researchers have found evidence of frostbite in humans dating back 5,000 years, in an Andean mummy. Napoleon's Army was the first documented instance of mass cold injury in the early 1800s. According to Zafren, nearly 1 million combatants fell victim to frostbite in the First and Second World Wars and the Korean War. == Society and culture ==

in hospital after developing frostbite when benighted on Denali in 1999. His nose, fingers and toes were subsequently amputated. Several notable cases of frostbite include: • Captain Lawrence Oates, an English army captain and Antarctic explorer who in 1912 died of complications of frostbite • Harold Bride, the junior wireless operator of , who suffered severe frostbite on his feet as he and other survivors stood for over an hour on the back of a capsized lifeboat knee-deep in freezing water—Bride had to be carried off from the rescue vessel after it arrived in New York • Noted American rock climber Hugh Herr, who in 1982 lost both legs below the knee to frostbite after being stranded on Mount Washington (New Hampshire) in a blizzard • Beck Weathers, a survivor of the 1996 Mount Everest disaster who lost his nose and hands to frostbite • Scottish mountaineer Jamie Andrew, who in 1999 had all four limbs amputated as a result of sepsis from frostbite sustained after becoming trapped for four nights whilst climbing Les Droites in the Mont Blanc massif ==Research directions==

Evidence is insufficient to determine whether or not hyperbaric oxygen therapy as an adjunctive treatment can assist in tissue salvage. Cases have been reported, but no randomized control trial has been performed on humans. Medical sympathectomy using intravenous reserpine has also been attempted with limited success. ==References==