Effect of ibuprofen on the pulmonary and systemic response to repeated doses of endotoxin.

We infused 10 doses of Escherichia coli endotoxin, 1 microgram/kg, during a 5-day period, into eight unanesthetized sheep with lung and systemic lymph fistulas. The animals were then monitored for an additional 5 days. We noted an attenuation of the lung microvascular permeability changes with the later endotoxin doses. However, a 50% increase in cardiac index and oxygen consumption and a leukocytosis were seen beginning with the ninth endotoxin injection; these persisted throughout the 15-day postendotoxin period, as did an increase in pulmonary artery pressure. The hyperdynamic state was present when plasma prostanoids were only modestly increased, and there was no evidence of increased lung or systemic vascular permeability. Postmortem lung findings, 5 days after endotoxin administration, showed a marked interstitial inflammatory response, with infiltration of macrophages, neutrophils, and some lymphocytes and an increase in interstitial fibrous tissue. Six sheep were then given ibuprofen, 12.5 mg/kg, intravenously before the ninth and tenth doses and on the subsequent day. Ibuprofen significantly attenuated the hyperdynamic state and the pulmonary hypertension. In addition, the lung inflammation and fibrous tissue deposition was markedly attenuated. We conclude that a systemic hyperdynamic state develops that corresponds in time with lung inflammation but not with increased permeability. The lung and systemic changes may be blocked by ibuprofen. The ibuprofen effect may be due to a response other than prostanoid production.