Frostbite is injury from tissue freezing and formation of ice crystals in the tissue. It can be divided into four tiers, or "degrees" of injury, which can be established by differences in imaging after rewarming. Alternatively, a two-tier classification may be used in the field after rewarming and before imaging. First-degree frostbite results in numbness and erythema; injured areas may show mild epidermal sloughing without gross tissue infarction. Second-degree injuries exhibit superficial skin vesiculation with clear or milky fluid filled blisters surrounded by erythema and edema. Third-degree frostbite results in deeper hemorrhagic blisters, extending beneath the dermal vascular plexus. Fourth-degree injuries extend completely through the dermis with necrosis extending into muscle and bone. The two-tier classification (similar to thermal burns) includes superficial (first- and second-degree injuries) with no or minimal anticipated tissue loss; and deep (third- and fourth-degree injuries) with anticipated tissue loss. Most tissue destruction follows reperfusion of the frozen tissues, with damaged endothelial cells and progressive microvascular thrombosis resulting in further tissue damage. In mild cases, only the skin and subcutaneous tissues are involved. Symptoms include numbness, prickling, itching, and pallor (eFigure 37–1). With increasing severity, deeper structures become involved; the skin appears white or yellow, loses elasticity, and becomes immobile. Edema, hemorrhagic blisters, necrosis, gangrene, paresthesias, and stiffness may occur (eFigure 37–2).
Digital ischemic lesions without necrotic tissue suggestive of superficial frostbite within all of the toes. (Used, with permission, from Dean SM, Satiani B, Abraham WT. Color Atlas and Synopsis of Vascular Diseases. McGraw-Hill, 2014.)
Deep frostbite, with the first and second toes showing an ischemic eschar with well-demarcated borders and clearcut margins, and hemorrhagic bullae on the second toe, the third toe showing a clear bulla and surrounding erythema, and the fourth toe showing complete necrosis. (Used, with permission, from Dean SM, Satiani B, Abraham WT. Color Atlas and Synopsis of Vascular Diseases. McGraw-Hill, 2014.)
Evaluate and treat the patient for associated systemic hypothermia, concurrent conditions, and injury. Early use of systemic analgesics is recommended for nonfrozen injuries. Fluids and electrolytes must be monitored. Hydrate the patient orally or parenterally to avoid hypovolemia and to improve perfusion.
Rapid rewarming at temperatures slightly above normal body temperature may significantly decrease tissue necrosis and reverse the tissue crystallization. If there is any possibility of refreezing, the frostbitten part must not be thawed. Refreezing results in increased tissue necrosis. Ideally, the frozen extremity must not be used, but if required for evacuation, the affected frozen extremity must be padded and splinted to avoid additional injury. Rewarming is best accomplished by warm bath immersion. The frozen extremity is immersed in a moving water bath ...