We examined the effects of the pericardium on diastolic function of the right and left ventricles during isoflurane anesthesia. The diastolic properties of the ventricles were assessed by indices of isovolumetric relaxation such as -dP/dt, -dP/dt25, and time constant for relaxation, and by end-diastolic pressure. In seven mongrel dogs, anesthesia was initially induced by the administration of pentobarbital and maintained with α- chloralose. Two 7F microtipped pressure transducers were inserted into the right and left ventricles, and a flow-directed pulmonary artery catheter was placed in the pulmonary artery. After a left thoracotomy, opening and closing the pericardium was performed at 0% isoflurane, 1.3% isoflurane, and 2.6% isoflurane. Isoflurane 1.3% and 2.6% produced a decrease in cardiac output in association with a decrease in -dP/dt and an increase in time constant for relaxation of both ventricles, suggesting that isoflurane may depress isovolumetric relaxation of both ventricles. Isoflurane also increased end- diastolic pressure of the left ventricle. With 0% isoflurane, pericardial opening did not significantly change the diastolic properties of either ventricle and other hemodynamics. Pericardial opening at 1.3% and 2.6% isoflurane increased cardiac output without any significant changes in - dP/dt and time constant of either ventricle, but with significant decreases in end-diastolic pressures of both ventricles. We conclude that the pericardium may have a constraining effect on the diastolic properties, especially end-diastolic pressure, but not on isovolumetric relaxation of both ventricles during isoflurane anesthesia.
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