Patients (20) undergoing coronary artery bypass grafting under fentanyl-pancuronium anesthesia were studied. Continuous ECG recording by a Holter Monitor was utilized to determine the incidence of ECG changes of myocardial ischemica during the precardiopulmonary bypass period and to determine the efficacy of an i.v. nitroglycerin (i.v. NTG) infusion for preventing ischemic ECG changes. Patients in group 1 (n = 9) received a 0.5 .mu.g .cntdot. kg-1 .cntdot. min-1 i.v. NTG infusion 20 min prior to induction of anesthesia and throughout the study. Patients in group 2 (n = 11) received placebo. A randomized double-blind protocol was employed. Anesthesia was induced with fentanyl 3 .mu.g .cntdot. kg-1 .cntdot. min-1. After fentanyl 25 .mu.g/kg and pancuronium 0.1 .mu.g/kg, the trachea was intubated. After fentanyl 50 .mu.g/kg surgery commenced. Prior to induction of anesthesia, i.v. NTG caused significant decreases in mean arterial pressure and pulmonary capillary wedge pressure, whereas placebo had no effect. However, subsequent to induction of anesthesia, hemodynamics in the 2 groups were identical. Of patients, 50% developed ECG changes of myocardial ischemia during the period from induction of anesthesia to commencement of cardiopulmonary bypass. The incidence of ischemic ECG changes was virtually identical in group 1 (5/9) and group 2 (5/11). Ischemic ECG changes were associated with increases in heart rate, mean arterial pressure, and rate pressure product, and decreases in the endocardial viability ratio (DPTI/SPTI). Increases in pulmonary capillary wedge pressure were not associated with myocardial ischemia. Fentanyl-pancuronium anesthesia, as administered in this study, was associated with a high incidence of myocardial ischemia. Ischemia was related to deteriorating myocardial O2 balance resulting from the cardiovascular effects of anesthetic induction, endotracheal intubation, and surgery. I.v. NTG was not superior to placebo for the prevention of ECG changes of myocardial ischemia during fentanyl-pancuronium anesthesia for coronary artery surgery.