FLAME BURNS AND SCALDS

Flame burns are the most common burns in adults. They are usually caused by the mishandling of flammable liquids, ignition of clothing, and house fires and result in an injury of variable thickness: charred, leathery full-thickness burns are intermixed with areas of partial-thickness injury. Sometimes focal areas of uninjured skin in the axilla, groin, antecubital space, and palm are found within the burn. In children younger than 5 years of age, spill scalds are the most common form of injury.

ELECTRIC BURNS

The risk of high-voltage electric injury is greatest in electricians, construction workers, farm workers who move irrigation pipes, oil field workers, truck drivers, and antenna installers. The damage to the tissue is due to heat produced by the resistance of tissue to the passage of electric current. The cell damage is greatest at the site of cutaneous contact but also includes the subcutaneous tissues and organs in the path of the electric current flow. Extensive devitalization of muscle may occur beneath deceivingly small cutaneous lesions. Current arcing also causes severe cutaneous injury at the flexor surfaces of joints, such as the wrist, elbow, and axilla. Claw hand deformity with inability to extend the fingers indicates severe and irreversible damage to the tissues of the hand and forearm and commonly predicts the need for amputation.

Formation of edema beneath the investing fascia of injured tissue may result in impaired blood supply to the distal unburned tissue, necessitating a fasciotomy to reduce the fluid pressure in soft tissue and prevent ischemic necrosis of unburned tissue.

CHEMICAL BURNS

Chemical agents cause exothermic reactions, dehydration, liquefaction necrosis (alkalosis), and delipidation in tissue. The severity of a chemical burn is related to the concentration of the chemical and the amount and duration of contact with tissue. In patients with chemical injury, immediate wound care is the priority, unlike treatment of all other burn patients, in whom systemic support takes precedence. All contaminated clothing should be removed immediately and copious water lavage begun to dilute the chemical agent and reduce the heat in the injured tissue. Strong acids may produce profound tanning of the skin, and strong alkalis penetrate tissue rapidly, causing characteristic liquefaction necrosis of soft tissue.

Formation of edema in the burn area is the result of increased vascular permeability and alterations in the relationships of transvascular pressure. Effects of edema are particularly marked in the loose areolar tissues of the face and oropharynx. The eyelids swell rapidly and may obstruct vision, even though the globe is typically protected by the blink reflex. Swelling of the tongue and other oropharyngeal tissues may compromise the supraglottic airway, necessitating endotracheal intubation to ensure adequate ventilation.

The magnitude and duration of physiologic changes are proportional to the extent of second- and third-degree burns, expressed as a percentage of the body surface. The extent of the burn can be most easily estimated using the rule of nines. In the adult, the surface area of specific anatomic parts represents 9% or a multiple thereof of the total body surface: head and neck, 9%; each upper limb, 9%; each lower limb, 18%; anterior trunk, 18%; posterior trunk, 18%; and genitalia, 1%.