Frostbite of the upper extremity.

Human capacity for physiologic adaptation to cold is minimal; we survive by insulating ourselves with protective clothing. In addition to the irreversible direct injury caused by ice crystallization, the authors have outlined four possible mechanisms by which indirect injury may damage tissue. Other than rapid rewarming, there is no uniformly accepted protocol for the treatment of frostbite injury. Attempting to sort out the world's literature on frostbite in an effort to present a comprehensive treatment protocol is a daunting task. In addition to the probably irreversible direct injury caused by ice crystallization, the authors have outlined at least four possible mechanisms by which indirect injury may damage tissue. The literature is full of various treatment protocols that allegedly are beneficial despite addressing different mechanisms. Mills described 10 different categories of medications, each addressing one of four possible mechanisms, used in the clinical treatment of frostbite injury over a 30-year period. Analyzing this information is even more confusing when one realizes that there is little uniformity in animal models employed to generate these data. This is further complicated by the lack of clinical correlation with the most common experimental model--liquid nitrogen rapid freezing. The risk of frostbite is highest when psychiatric disturbance, intoxication, or unplanned circumstances lead to cold exposure without adequate protective clothing. As tissue freezes, both direct and indirect factors cause injury. Most therapies have been aimed at limiting indirect injury, in an attempt to limit progressive tissue loss. Rapid rewarming is universally accepted, but the benefits of other modalities are still controversial. Traditionally, observation and delayed amputation have been employed to manage frostbite. More recently, triple-phase bone scans have been used to distinguish between tissue that is irreversibly destined for necrosis and tissue that is at-risk for necrosis, but potentially salvageable. Early operation can be used to provide at-risk tissue with a new blood supply and preserve both function and length in the upper extremity.