Review: acute versus chronic response to burn injury.

The acute response to burn injury is referred to as the ebb, or shock, phase. It is characterized as a hypodynamic state, with both cardiac output and metabolic rate being depressed. Hyperglycemia is evident, owing both to an increased rate of production of glucose and a peripheral "insulin resistance." Lactate production is markedly elevated, whereas the FFA response is variable. Clinically, the predominant concern is repletion of the plasma volume that was lost as a consequence of increased capillary permeability. If adequate fluid resuscitation is administered, recovery from burn shock can usually be accomplished. The chronic response to burn injury, or flow phase, may last for many weeks. It is a hyperdynamic state, with both cardiac output and metabolic rate being elevated. Without appropriate nutritional therapy, severe protein wasting can occur as a consequence of an accelerated rate of protein catabolism. The increase in protein catabolism is associated with an increase in the rate of glucose production. There appear to be changes in fat metabolism as well, but more quantitative studies are needed in this area. In general, improved emergency room treatment has greatly improved survival from burn shock, and the focus of much of the study of the response to burn injury has consequently shifted to the flow phase. In that regard, many important questions still remain unanswered. The most pressing problem to those interested in metabolism and nutrition is probably the identification of the signal for the metabolic response evident in the flow phase.