Combined effects of halothane anesthesia and verapamil on systemic hemodynamics and left ventricular myocardial contractility in patients with ischemic heart disease.

The interaction of halothane anesthesia and intravenous verapamil (0.15 mg/kg over 10 min) was investigated in eight patients scheduled for coronary artery bypass surgery. All patients had a normal left ventricular (LV) function at rest and were on chronic beta-blocker therapy. Halothane produced a marked reduction in mean arterial pressure (MAP), cardiac index, and in LV contractility as documented by a decrease in LV peak positive dP/dt. Verapamil caused an additional depression (16%) of LV peak positive dP/dt accompanied by a small increase (3 mm Hg) in LV end-diastolic pressure. The combined negative inotropic propensities of halothane and verapamil did not produce any overt untoward effects even in the presence of chronic low dose beta-blocker therapy. The predominant hemodynamic effect of verapamil was a systemic vasodilation resulting in a further reduction in MAP (12%) while heart rate remained unaffected. Despite reducing myocardial oxygen demand, caution must be exercised in dose selection in each drug to avoid regional myocardial ischemia due to the combined hypotensive effects of halothane and verapamil.