burn [AS, baernan] , any injury to tissues of the body caused by hot objects or flames, electricity, chemicals, radiation, or gases in which the extent of the injury is determined by the nature of the agent, length of time exposed, body part involved, and depth of burn. The treatment of burns includes pain relief, careful asepsis, prevention of infection, regulation of body temperature, maintenance of the balance in the body of fluids and electrolytes, and good nutrition. First priority with burns of the airway is airway control. Severe burns of any origin may cause shock, which is treated before the wound. Burns are sometimes classified as first, second, third, and fourth degree. First-degree burns involve only a superficial layer of epidermal cells. Second-degree burns may be divided into superficial partial-thickness and deep partial-thickness wounds. Damage in second-degree burns extends through the epidermis to the dermis but is usually not sufficient to prevent skin regeneration. In third-degree burns the entire thickness of the epidermis and dermis is destroyed. Fourth-degree burns are full-thickness injuries that penetrate the subcutaneous tissue, muscle, and periosteum or bone. See also chemical burn, electrocution, thermal burn.
