Pathophysiologic events related to thermal injury of skin

Acute thermal injury of skin equivalent to second-degree injury and involving approximately 25% of total body surface results in a series of pathophysiologic events which lead to both local and distant tissue/organ injury. The distant effects involve intravascular hemolysis and acute lung injury, both of which can be attributed to complement activation and intravascular stimulation of neutrophils, resulting in oxygen radical production, which results in injury of red cells and pulmonary vascular endothelial cells. At the local site of thermal injury, the progressive increase in vascular permeability is linked to complement activation and histamine release, the outcome of which is interaction of histamine with xanthine oxidase, resulting in enhanced catalytic activity of the enzyme. Toxic oxygen products of xanthine oxidase, including H2O2 and its conversion product, the hydroxyl radical, appear to be linked to the damage of dermal vascular endothelial cells, resulting in progressive vascular permeability. The increased vascular permeability can be greatly attenuated by the use of inhibitors of xanthine oxidase, the inhibitor of histamine release (cromolyn), catalase, an iron chelator (deferoxamine), or scavengers of the hydroxyl radical. Interestingly, neutrophils appear to play little if any role in dermal vascular injury in this animal model of thermal trauma. Those studies suggest that pathophysiologic events following local thermal trauma are complex and involve a variety of mediator pathways.