Frostbite

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Jaspinder Kaur, MBBS[2]

Synonyms and keywords:

Overview

Frostbite (congelatio in medical terminology) is the medical condition whereby damage is caused to skin and other tissues due to extreme cold. At or below 0º C (32ºF), blood vessels close to the skin start to narrow (constrict). This helps to preserve core body temperature. In extreme cold or when the body is exposed to cold for long periods, this protective strategy can reduce blood flow in some areas of the body to dangerously low levels. The areas where this occurs will freeze over. The combination of cold temperature and poor blood flow can cause severe tissue injury by freezing the tissue. Frostbite is most likely to happen in body parts farthest from the heart, and those with a lot of surface area exposed to cold. The initial stages of frostbite are sometimes called "frostnip". Mountains or high altitudes with snow are most dangerous to cause frostbite. If frostbite is not treated immediately then the damage and the frostbite become permanent. Nerve damage will occur because oxygen doesn't get to the areas. Frostbitten areas will turn discolored, purplish at first, and soon turn black. After a while nerve damage becomes so great that feeling is lost in the frostbitten areas. Blisters will also occur. If feeling is lost in the damaged area, checking it for cuts and breaks in the skin is vital. Infected open skin can lead to gangrene and amputation may be needed.

Differentiating Frostbite from other Diseases

Differential disease	Clinical characteristics
Cutaneous burns	Caused by exposure to heat or chemicals rather than cold. Clinical diagnosis.
Frostnip	Frostnip is the mildest and most common form of freezing cold injury. Symptoms: Pain and pallor followed by numbness of exposed areas such as cheeks, nose, ears, and digits. Treatment: Rewarming the tissues results in return of sensation and function without further damage. The presence of frostnip is an indicator that environmental conditions are severe enough for frostbite, so necessary precautions must be followed. Clinical diagnosis.
Raynaud phenomenon	Skin changes are reversible. No evidence of tissue damage. Clinical diagnosis.
Chilblains (Pernio or Perniosis)	Chilblains are an inflammatory nonfreezing skin condition due to an abnormal vascular response to cold. Clinical presentation: Tender, pruritic red or blue lesions on the fingers, ears, toes, and nose. They have also been reported on the thighs and buttocks; however, they are less common in these locations. The lesions typically appear within 12 to 24 hours after cold exposure and resolve spontaneously in 1 to 3 weeks. Etiology: More than half of cases are idiopathic; however, studies have found an association of up to 20% to 40% with more concerning conditions, including systemic lupus erythematosus, cryoglobulinemia, antiphospholipid syndrome, macroglobulinemia, and chronic myelomonocytic leukemia. Treatment: Avoiding cold exposure is the best way to prevent chilblains. Treatment is best accomplished by drying and gently massaging the affected areas. The lesions are more painful upon rewarming. Active rewarming above 86°F (30°C) may significantly worsen the pain, so should be avoided. Chilblains are a diagnosis of exclusion. Clinical evaluation involves complete blood count, antiphospholipid antibody panel, cryoglobulins, cryofibrinogen, cold agglutinins, antinuclear antibodies, and serum protein electrophoresis. Chronic cases may require a biopsy to rule out other inflammatory processes. Histology shows papillary dermal edema, perivascular lymphocytic infiltrates, and blood vessel wall edema.
Immersion foot (trench foot)	Trenchfoot, also known as cold immersion foot, is a nonfreezing cold injury caused by prolonged exposure (between 12 hours and 4 days) to cold and wet conditions. Military personnel are particularly prone to this condition. The suspected mechanism of action is alternating periods of vasoconstriction and vasodilation in the affected tissues. Prolonged exposure to near-freezing temperatures results in anesthesia followed by hyperemia, the latter of which can last for up to 3 months after the initial injury. The pain can recur with even slight re-exposure to cold, including commercial food lockers or freezers. In contrast to frostbite, rapid rewarming in trenchfoot may lead to worsened hyperemia and poor outcomes. Therefore, treatment involves slow rewarming. Clinical diagnosis.

Risk Factors

Risk factors for frostbite include using beta-blockers and having conditions such as diabetes and peripheral neuropathy.

Natural History, Complications and Prognosis

Frostbitten hands

Diagnosis

History and Symptoms

Generally, frostbite is accompanied by discoloration of the skin, along with burning and/or tingling sensations, partial or complete numbness, and possibly intense pain. If the affected areas and blood vessels have been severely damaged, gangrene may follow, and amputation may eventually be required. If left untreated, frostbitten skin gradually darkens and blisters after a few hours. Skin destroyed by frostbite is completely black, and looks loose, flayed and flexible. The black skin looks burnt. Frostbitten areas are cold to the touch.

Treatment

Medical Therapy

To treat frostbite, move the victim to a warm location and seek medical help. Soak frostbitten areas in warm (not hot) water, or, if in wilderness, warm by contact with the skin of a non-frostbitten person. Continue until the victim has regained sensation and movement in the afflicted region; this often follows great pain as the nerves thaw. Never rub, slap or shake the stricken region as ice crystals in the frostbitten skin will damage surrounding tissue. Follow the treatment with a period of constant warmth: refreezing following thawing worsens the damage.

Primary Prevention

Factors that contribute to frostbite include extreme cold, wet clothes, wind chill, and poor circulation. This can be caused by tight clothing or boots, cramped positions, fatigue, certain medications, smoking, alcohol use, or diseases that affect the blood vessels, such as diabetes. Moreover employees working in chemical laboratories should take precautions to wear gloves and other safety equipment as liquid nitrogen and other cryogenic liquids can cause frostbite even with brief exposure. If caught in a severe snowstorm, one should find shelter early or increase physical activity to maintain body warmth. People susceptible to frostbite should wear woolen socks/gloves/caps in extreme cold. For frostbite in the feet, keeping feet in warm saline water will provide relief. Diabetes can also sometimes lead to frostbite, so diabetics should take precautions as to avoid trips to ice-cold places.

Related Chapters

• Hypothermia
• Epidermis
• Wilderness First Aid

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