ARE THE CARDIOVASCULAR ACTIONS OF DOPAMINE ALTERED BY ISOFLURANE

Dopamine seems theoretically to be a rationale choice when adrenergic support is needed to counter undesired cardiovascular depressant effec ts of isoflurane. Although the cardiovascular effects of isoflurane (I SO) and exogenous dopamine (DA) are well documented, there are no repo rts on their pharmacological interaction. The effects of ISO 1.4% (MAC 1.0) on the cardiovascular response to exogenous DA were studied in d ogs during chloralose anesthesia. Instrumentation included catheteriza tions of the femoral artery (for aortic pressures and heart rate, HR), the pulmonary artery (for thermodilution cardiac output, CO, and pulm onary arterial pressures) and the left ventricle (for tip-manometer me asured left ventricular end-diastolic pressure, LVEDP). ISO per se dec reased HR (-16%), mean arterial pressure (MAP; -33%), CO (-29%), left ventricular dP/dt (LV dP/dt; -51%), and increased pulmonary artery occ lusion (PAOP; +64%) and LVEDP (+28%). Prior to ISO, DA increased MAP, CO stroke volume (SV), LV dP/dt and LV dP/dt/SAP (systolic arterial pr essure) at the dose 10 mu g . kg(-1). min(-1). At the dose 20 mu f . k g(-1). min(-1) DA, besides these effects, increased PAOP and mean pulm onary artery pressure (MPAP). During ISO, DA at the dose 10 mu g . kg( -1). min(-1) restored MAP, CO, and SV to pre-ISO control levels, while LV dP/dt was increased to +96% above the pre-ISO control level. At th e dose 20 mu g . kg(-1). min(-1), DA increased MAP (+33%), LV dP/dt (172%), PAOP (+132%) and MPAP (+50%) above pre-ISO control levels. The cardiac effects of DA were similar to when it was given alone. However , the increase in SVR (at the dose 20 mu g . kg(-1). min(-1)) and MAP (at the 10 and 20 mu g . kg(-1). min(-1) doses) by DA was significantl y more pronounced with ISO than without ISO. In conclusion, the presse r effects of DA seem to be potentiated by ISO. DA restores systemic ar terial pressure during ISO anesthesia by attenuating the cardiac depre ssant effects of ISO and by increasing SVR above pre-ISO control level s.