The effect of ketamine on endotoxin-induced lung injury.

We investigated the effects of ketamine HCl on endotoxin-induced pulmonary injury in 20 chronically instrumented sheep with lung lymph fistulas. The caudal mediastinal lymph node was cannulated in 20 ewes (45-55 kg). The catheter was externalized and the lymph allowed to drain freely. Pulmonary injury was induced by an intravenous infusion of Escherichia coli endotoxin (1.0-1.5 micrograms/kg body wt) over a 5-min period in 11 animals. The injury was characterized by an increase in pulmonary arterial pressure, pulmonary arterial wedge pressure, and lung lymph flow. There was no change in mean systemic arterial pressure. These changes were significantly attenuated by intravenous administration of ketamine HCl (5 mg/kg) following endotoxin injury in 9 other animals. When ketamine was given, the pulmonary arterial pressure decreased 32%, lung lymph flow decreased 27%, and systemic blood pressure increased 22%. Potential mechanisms for the hemodynamic effects of ketamine HCl in sepsis are discussed with particular reference to the pulmonary microvasculature.