Cardiovascular depression by isoflurane and concomitant thoracic epidural anesthesia is reversed by dopamine

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Abstract
Interactive effects between exogenous dopamine (DA) and isoflurane (I) combined with thoracic epidural blockade (TEA) were studied in dogs during chloralose anesthesia. The I–TEA intervention per se decreased heart rate (HR; 28%), mean arterial pressure (MAP; 63%), cardiac output (CO; 54%), left ventricular dP/ dt (LVdP/dt; 75%) and LVdP/dt/systolic arterial pressure (SAP; 42%). Prior to the I–TEA intervention, dopamine increased MAP, CO, LVdP/dt, LVdP/dt/SAP and stroke volume (SV) already at the dose 10 μg–kg-1. min-1 and, additionally, increased mean pulmonary artery pressure (MPAP) at the dose 20 μg–kg-1. min-1. During the I–TEA intervention, the DA–induced increases in MAP and systemic vascular resistance (SVR) were significantly higher than prior to I–TEA, as indicated by significant ANOVA interactive effects. At the dose 10 μg–kg-1 min-1, DA restored MAP, CO, LVdP/dt, LVdP/dt/SAP and SV to levels found before the I–TEA intervention, while HR was restored first at the dose 20 μg–kg-1 –min-1. At the dose 20 μg–kg-1–min-1, DA 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 counters cardiovascular depression induced by the anesthetic technique of combining I and TEA. The pressor and systemic vasoconstrictor actions of dopamine are potentiated by conjoint administration of I and TEA.