Frostbite is tissue freezing resulting from heat loss sufficient to cause ice crystal formation in superficial or deep tissue. Frostbite usually affects the extremities, nose, or ears (and the scrotum and penis in joggers). A sensation of numbness with accompanying sensory loss is the most common initial complaint. Often, by the time the patient arrives in the ED, the frozen tissue has thawed. The initial appearance of the overlying skin may be deceptively benign. Frozen tissue may appear mottled blue, violaceous, yellowish-white, or waxy. Following rapid rewarming, there is early hyperemia even in severe cases.
Favorable signs include return of normal sensation, color, and warmth. Edema should appear within 3 hours of thawing; lack of edema is an unfavorable sign. Vesicles and bullae appear in 1 to 24 hours. Early formation of large clear blebs that extend to the tips of affected digits is a good indicator. Small dark blebs that do not extend to the tips indicate damage to subdermal plexi and are a poor prognostic sign. When seen early or soon after rewarming occurs, frostbite may be indistinguishable from nonfreezing cold injury such as immersion foot. Mixed injuries are common. Tissue loss is rare in uncomplicated nonfreezing cold injury.
Management and Disposition
If other injuries are ruled out by history and physical examination, rewarm frostbitten areas in warm water bath (37°C-39°C [98.6°F-102.2°F]). If associated with severe hypothermia, active core rewarming should precede frostbite rewarming. If swelling occurs, surgical consultation is advisable to determine the need for fasciotomy. Admit all patients with associated hypothermia or in whom swelling occurs. Patients with superficial frostbite (minimal skin changes and erythema) may be treated by home care with nursing instructions. Patients with deep superficial frostbite (clear, fluid-filled blebs, swelling, pain) may be treated by home care in a reliable patient. The presence of deep frostbite (proximal hemorrhagic blebs, no swelling, no pulses) mandates hospital admission.
Thawed Frostbite. Appearance of frostbite soon after rewarming. Deep frostbite was caused by wearing mountaineering boots that were too tight in extreme cold at high altitude. Note the deceptively benign appearance of this devastating injury, which ultimately resulted in bilateral below-the-knee amputations. (Photo contributor: Ken Zafren, MD.)
Deep Frostbite. Deep frostbite at Everest Base Camp in Nepal, at 5360 m (17,585 ft), 3 days after exposure at 6400 m (21,000 ft). Dusky appearance and lack of distal blistering are poor prognostic signs. The great toe eventually required partial amputation. (Photo contributor: Chris Imray, MD.)
Frostbite Blebs. Intact proximal blebs, both clear and hemorrhagic, indicate deep frostbite and a poor prognosis. (Photo contributor: Scott W. Zackowski, MD.)