Effects of short-term infusion of nifedipine or verapamil on systemic hemodynamics and left ventricular myocardial contractility in patients prior to coronary artery bypass surgery.

The effects of short-term infusion (10 min) of nifedipine (7.5 micrograms . kg-1) or verapamil (0.15 mg . kg-1) on left ventricular (LV) contractility and on systemic hemodynamics in patients with coronary artery disease, chronically treated with low-dose beta-adrenergic blocking drugs, exhibiting a normal LV function at rest, are presented. In order to analyze the interaction between calcium entry blocking drugs and halothane, the results are discussed in light of data, obtained in similar patients during halothane anesthesia, using identical experimental conditions, which have already been reported. LV dP/dtmax and LV end-diastolic pressure (LVEDP) remained unaffected when nifedipine was infused in the awake patients. Verapamil significantly decreased LV dP/dtmax in patients while awake, but LVEDP did not change. Both calcium entry blocking drugs caused decreases in blood pressure and systemic vascular resistance, accompanied by increases in heart rate. The only significant differences between the awake and the anesthetized patients were the absence of changes in heart rate and the greater reduction in LV dP/dtmax following administration of the calcium entry blocking drugs during anesthesia. Possible explanations for this may include the drugs' combined interference with calcium ion fluxes within the myocardial and smooth muscle fibers, the ability of halothane to modify the response of the autonomic nervous system to the calcium entry blocking drugs and altered kinetics of the calcium entry blocking drugs induced by the volatile anesthetic. It is impossible to determine from the present investigation which of these mechanisms is predominant.