injuries poisoning
Frostbite
Introduction
Frostbite is injury due to freezing of tissue. Initial manifestations may be deceptively benign. Skin may appear white or blistered and is numb; rewarming causes substantial pain. Gangrene may develop. Severely damaged tissue may autoamputate. Treatment is rewarming in warm (37 to 40° C) water and local care. Surgical amputation is occasionally necessary, but a decision, often guided by imaging results, should usually be delayed until after definitive demarcation of necrotic tissue. (See also Overview of Cold Injury .) Frostbite usually occurs in extreme cold, especially at high altitude, and is aggravated by Hypothermia . Distal extremities and exposed skin are affected most often. Ice crystals form within or between tissue cells, essentially freezing the tissue and causing cell death. Adjacent unfrozen areas are at risk because local vasoconstriction and thrombosis can cause endothelial and ischemic damage. With reperfusion during rewarming, inflammatory cytokines (eg, thromboxanes, prostaglandins) are released, exacerbating tissue injury. Depth of tissue loss depends on duration and depth of freezing. 