Comparison of ketamine and pentobarbital anesthesia with the conscious state in a porcine model of Pseudomonas aeruginosa septicemia

Live Pseudomonas aeruginosa (2.5.10(9).kg-1.h-1) were administered to awake (Group A, n = 10) and anesthetized piglets, which were given intravenous ketamine (Group K, 10 mg.kg-1.h-1, n = 8) or pentobarbital (Group P, 15 mg.kg-1.h-1, n = 8). The anesthetized animals were mechanically ventilated. In addition, a pentobarbital group (Group CP, n = 6) and a ketamine control group (Group CK, n = 6) were studied. The mean survival time was 10.5 +/- 3.0 h in Group A, 10.6 +/- 2.8 h in Group K, and 1.8 +/- 1.3 h in Group P. In Group P the arterial pressure, the cardiac output and the systemic vascular resistance declined soon after start of the bacterial infusion, whereas the pulmonary artery pressure increased. The animals died of irreversible circulatory failure. In Group K pronounced pulmonary hypertension and lethal pulmonary edema developed. There was no circulatory failure in Group A, but the animals also died of marked pulmonary edema. Groups CP and CK exhibited stable hemodynamics for a period of 8 h. The results of this study suggest a deleterious effect of pentobarbital on hemodynamics and survival time, and a minor suppressive action of ketamine on the circulation in septicemia. Therefore, data obtained from septic shock studies applying pentobarbital have to be evaluated carefully. Investigation of the effects of gram-negative bacteria or endotoxin should be performed in unanesthetized or, if anesthesia is necessary, in ketamine-anesthetized animals.