CARDIOVASCULAR DEPRESSION BY ISOFLURANE AND CONCOMITANT THORACIC EPIDURAL-ANESTHESIA IS REVERSED BY DOPAMINE

Interactive effects between exogenous dopamine (DA) and isoflurane (I) combined with thoracic epidural blockade (TEA) were studied in dogs d uring chloralose anesthesia. The I-TEA intervention per se decreased h eart rate (HR; 28%), mean arterial pressure (MAP; 63%), cardiac output (CO; 54%), left ventricular dP/ dt (LVdP/dt; 75%) and LVdP/dt/systoli c arterial pressure (SAP; 42%). Prior to tile I-IEA intervention, dopa mine increased MAP, CO, LVdP/dt, LVdP/dt/SAP and stroke volume (SV) al ready at the dose 10 mu g kg(-1) min(-1) and, additionally, increased mean pulmonary artery pressure (MPAP) at the dose 20 mu g.kg(-1).min(- 1). During the I-TEA intervention, the DA-induced increases in MAP and systemic vascular resistance (SVR) were significantly higher than pri or to I-TEA, as indicated by significant ANOVA interactive effects. At the dose 10 mu g.kg(-1).min(-1), DA restored MAP, CO, LVdP/dt, LVdP/d t/SAP and SV to levels found before the I-TEA intervention, while HR w as restored first at the dose 20 mu g.kg(-1).min(-1). At the dose 20 m u g.kg(-1).min(-1), DX also increased MAP (39%), LVdP/dt (119%), LVdP/ dt/SAP (73%), SVR (28%) and MPAP (70%) above levels prior to I-TEA. To conclude, exogenous dopamine effectively and dose-dependently counter s cardiovascular depression induced by the anesthetic technique of com bining I and TEA. The presser and systemic vasoconstrictor actions of dopamine are potentiated by conjoint administration of I and TEA.