Cardiovascular Interactions of Halothane Anesthesia and Nifedipine in Patients Subjected to Elective Coronary Artery Bypass Surgery

Abstract

The effects of intravenous (iv) nifedipine (7.5 micrograms/kg over 10 min) on systemic hemodynamics and myocardial contractility were investigated under steady state conditions of halothane anesthesia (0.5 MAC) in 8 patients scheduled for elective coronary artery bypass surgery. All patients received long-term medication in the form of beta adrenergic receptor blockers and had a normal global left ventricular function at rest. Halothane produced a marked reduction in left ventricular contractility as documented by a considerable fall in LV max dP/dt. Nifedipine caused a small additional depression of LV max dP/dt without affecting LVEDP significantly. The slight myocardial depressant effect of nifedipine was counterbalanced by a concomitant reduction in left ventricular afterload due to a decrease in the systemic vascular resistance resulting in unchanged or even improved cardiac output. The results indicate that iv nifedipine in the doses used here is safe for patients with ischemic heart disease, even in the presence of already compromised myocardial contractility due to halothane anesthesia and chronic low-dose beta blocker therapy.

Pharmacotherapeutic Considerations in Anesthesia

“…Given the additive effects of general anesthetics and calcium-channel blockers in reducing left ventricular dP/dT and decreasing afterload, one should be careful in using this combination of drugs in patients with impaired cardiac function or hypovolemia. 15, 16 The PR interval should also be carefully monitored in these patients.…”