Gram-negative sepsis in thermally injured sheep

Burn wound sepsis was studied for four days in awake, unanesthetized sheep. Each of the animals was given a 40% third-degree burn, and the wound was infected with Pseudomonas aeruginosa. According to their cardiopulmonary response, the animals were divided into three groups: hyperdynamic, normodynamic, and hypodynamic. The hyperdynamic group had an increased cardiac index and a decreased total peripheral resistance index. The hypodynamic group was characterized by the following: decreased cardiac index, increased total peripheral resistance index, increased hematocrit, decreased PaO2, increased pulmonary vascular resistance index, and decreased neutrophils (P less than or equal to 0.05). The hypodynamic group was inoculated with more P aeruginosa, had more positive cultures for P aeruginosa, and had a greater mortality rate than the other two groups. It is suggested that the hypodynamic group was hypovolemic as a result of a fluid shift from the vascular compartment, that this fluid shift may be important in preventing the animals from responding to sepsis with an elevated cardiac index, and that the derivation of the cardiovascular response to sepsis is related to the severity of the initial septic insult.