Frostbite

Frostbite– Localized cold injury.

Causes and Incidence

Frostbite is caused by exposure to damp cold temperatures around freezing or to dry cold temperatures well below freezing. Susceptibility is increased by dehydration, exhaustion, hunger, substance abuse, impaired circulation, and impaired consciousness. Factors that promote heat loss (e.g., wet clothing, contact with wet metal, wind chill, radiation) increase the severity of injury, as does prolonged exposure to cold. The very young and the elderly are more prone to frostbite, as are those from warmer climates who are not acclimated to cold.

Disease Process

Cold exposure can cause cellular injury either by direct formation of ice crystals in the cells or by vascular spasm and occlusion, which result in inadequate tissue perfusion. Cell dehydration leads to vasoconstriction and increased blood viscosity, with sludge and thrombus formation. As thawing takes place, venous stasis occurs at the sites of injury, obstructing the vascular bed and causing edema and tissue necrosis. Tissue damage may range from superficial (skin and subcutaneous tissue) to deep (muscle, tendon, and neurovascular structures).

Symptoms

Superficial
Injured area is white, waxy, soft, and numb while still cold; as thawing occurs, area becomes flushed, edematous, and painful, and may become mottled and purple; in 24 hours, large blisters form that remain about 2 weeks before turning into a hardened eschar that remains for about a month before separating, leaving painful, sensitive new skin that often sweats excessively

Deep
Injured part remains hard, cold, mottled, and blue-gray after thawing; edema forms in entire limb and may remain for months; blisters may not form or may form after a delay of several weeks; after several weeks, dead tissue blackens and sloughs off; a line demarcates dead from live tissue

Potential Complications

Loss of digits, ears, nose, and extremities is possible, as is secondary infection.

Diagnostic Tests

The diagnosis is made by clinical examination plus a history of exposure to cold.

Treatments

Surgery
Escharotomy; sympathectomy for severe vasospasm; debridement after retraction of viable tissue (34 months after injury; amputation of nonviable extremities several months after injury).

Drugs
Immunologic agents (tetanus) and antiinfective drugs for prophylaxis; analgesics for pain; plasma expanders to reduce sludge and thrombus formation.

General
Rapid rewarming by immersion in water (37.8o to 43.3o C [100o to 110o F]); fluid and electrolyte replacement; whirlpool baths; precautions with injured area to prevent dislodgment of eschar and further damage; counseling for altered body image from loss of limbs; exercise to prevent joint restriction.