Is endotoxin responsible for the cardiopulmonary lesions seen during acute burn wound sepsis?

Acute burn wound sepsis is a common clinical entity resulting from a showering of the circulation with gram-negative organisms which grow abundantly in the burn. We duplicate this state in our laboratory by creating 40%, third degree burns (anesthetic burns) in chronically instrumented sheep. Three days following the thermal insult, the burn wound is infected by injecting gram-negative organisms (3 X 10(10)) into it. Cardiopulmonary variables and pulmonary lymph flux data are monitored two hours prior to the injection of organisms and for three hours following it. Three different organisms were used in this study; Pseudomonas aeruginosa (N = 12), Escherichia coli (N = 9), and Klebsiella pneumoniae (N = 2). The injection of all three organisms resulted in a similar response; an early marked pulmonary hypertension and a late increase in microvascular permeability. These changes occur concomitantly with an elevation in hematocrit and an early marked fall in neutrophils. The cardiac output gradually falls over the period of observation despite vigorous body shivering associated with a febrile response. The data from the sheep were compared to similarly instrumented animals (N = 12) which were not burned, but received a very small dosage of E coli endotoxin (0.75 micrograms/kg). The cardiopulmonary response was qualitatively identical to that seen with live organisms. However, the quantitative changes in several of the cardiopulmonary variables were much more marked with endotoxin. It is concluded that the cardiopulmonary response noted with burn wound sepsis is produced by endotoxin.