Propofol Selectively Attenuates Endothelium-dependent Pulmonary Vasodilation in Chronically Instrumented Dogs

Abstract

Background The objective was to investigate the effects of propofol anesthesia on the pulmonary vascular response to endothelium-dependent and -independent vasodilators, compared with the responses measured in the conscious state. Methods Twenty-six conditioned, male, mongrel dogs were instrumented long-term to measure the left pulmonary vascular pressure-flow relation. Pressure-flow plots were measured on separate days in conscious and propofol-anesthetized (5.0 mg/kg plus 0.5 mg. kg-1. min-1 intravenously) dogs at baseline, after preconstriction with the thromboxane mimetic U46619, and during the cumulative intravenous administration of endothelium-dependent (acetylcholine and bradykinin) and -independent (proline-nitric oxide) vasodilators. Results Propofol had no effect on the baseline pressure-flow relation compared with the conscious state. A lower (P < 0.05) dose of U46619 was necessary to achieve the same degree of preconstriction during propofol anesthesia. The pulmonary vasodilator responses to bradykinin and proline-nitric oxide were similar in the conscious and propofol-anesthetized states. In contrast, the pulmonary vasodilator response to acetylcholine was markedly attenuated (P < 0.01) during propofol anesthesia. The intralipid vehicle for propofol had no effect on the acetylcholine dose-response relation. Conclusion These results suggest that propofol causes a specific defect in the signal transduction pathway for acetylcholine-induced pulmonary vasodilation. This defect involves the endothelial and not the vascular smooth muscle component of the response.