Frostbite

Overview

This StatPearls review by Basit, Wallen and Dudley, last updated in June 2023, covers frostbite (freezing cold injury), tissue damage from cold exposure at temperatures below 0 °C. The feet, hands, ears, lips and nose are most often affected. Homeless people, children, older people and people active outdoors are especially vulnerable, and risk rises with wind chill, altitude, wet conditions, alcohol or drug use, altered mental status, malnutrition, smoking and conditions such as diabetes, peripheral vascular disease and Raynaud disease. The goal of treatment is to save as much tissue and function as possible.

Pathophysiology

Vasoconstriction reduces blood flow, ice crystals form in and around cells and membranes are damaged, and stasis, microthrombi and reperfusion injury add ischaemia. The injury has a zone of coagulation (irreversible), a zone of stasis (potentially reversible) and a zone of hyperaemia. Repeated thaw and refreeze makes the injury worse.

Examination and evaluation

The skin is blanched and white and may later turn dark or purplish. Superficial frostbite blisters with pale fluid on rewarming, whereas deep frostbite becomes haemorrhagic and may turn gangrenous. The first examination does not predict the final depth. After rewarming, oedema appears within 3 to 5 hours, blisters within 4 to 24 hours, eschar at 10 to 15 days and mummification with a line of demarcation at 3 to 8 weeks. Diagnosis is clinical, and technetium-99 triple-phase scans and MR angiography can help predict the level of amputation and identify candidates for thrombolysis. Staging is by degrees like burns (first to fourth) or by a four-grade scheme based on the extent of cyanosis, in which a higher grade means a greater risk of amputation.

Treatment

The patient is protected from further cold, and rewarming in the field is done only if there is no risk of refreezing. Wet clothing is replaced and rubbing is avoided. In hospital the limb is placed in a warm water bath at about 40 to 42 °C, after hypothermia has been corrected (core temperature above 35 °C). Ibuprofen is used, with stronger analgesics if needed. White blisters may be drained and haemorrhagic ones are left intact, and debridement and amputation are delayed (up to 6 weeks) until viability is clear, except in compartment syndrome. Patients with full-thickness injury and no reperfusion after rewarming may be candidates for tPA, which can reduce digit amputation, and intravenous iloprost is not available in the United States.

Prognosis and prevention

Recovery takes 5 to 30 days depending on severity. Unfavourable signs include haemorrhagic blisters, non-blanching cyanosis and firm skin after rewarming. Long-term problems include cold intolerance, paraesthesias, nail loss, chronic pain and complex regional pain syndrome, and cold exposure should be avoided for up to a year. Prevention depends on proper clothing, shelter, hydration, keeping clothing dry and avoiding alcohol.