Volatile anesthetics constrict pulmonary artery in rabbit lung perfusion model

Volatile anesthetics are generally considered to possess a vasodilator action. Some of their actions on pulmonary vessels, however, are not clearly understood. We examined the effects of various volatile anesthetics on pulmonary vessels using an in situ rabbit isolated-lung perfusion model. We prepared a rabbit constant-flow lung-perfusion model by sending blood to the pulmonary artery and removing blood from the left atrium, and observed the changes in pulmonary arterial perfusion pressure caused by inhalation of 0.5, 1, 2, and 3 minimum alveolar concentration (MAC) volatile anesthetics: halothane, enflurane, isoflurane, and sevoflurane, in random order. These volatile anesthetics increased pulmonary arterial perfusion pressure in a dose-dependent manner and caused the pulmonary arteries to constrict. In particular, halothane at all concentrations induced significantly greater pulmonary vasoconstriction than the other volatile anesthetics. Therefore, it is suggested that volatile inhalation anesthetics induce the pulmonary arteries to constrict, and halothane exhibits the most potent pulmonary vasoconstrictor effect among the volatile anesthetics tested.