The effects of intravenous (iv) nifedipine (7.5 μg/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.
Anesthesia - Inhalation - Calcium antagonists - Exogenous - Coronary disease - Therapy
