Failure of Intravenous Nitroglycerin to Prevent Intraoperative Myocardial Ischemia during Fentanyl–Pancuronium Anesthesia

Twenty patients undergoing coronary artery bypass grafting under fentanyl-pancuronium anesthesia were studied. Continuous electrocardiographic (ECG) recording by a Holter Monitor was utilized to determine the incidence of ECG changes of myocardial ischemia during the precardiopulmonary bypass period and to determine the efficacy of an intravenous nitroglycerin (iv NTG) infusion for preventing ischemic ECG changes. Patients in Group 1 (n = 9) received a 0.5 microgram . kg-1 . min-1 iv 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 micrograms . kg-1 . min-1. After fentanyl 25 micrograms/kg and pancuronium 0.1 microgram/kg, the trachea was intubated. After fentanyl 50 micrograms/kg surgery commenced. Prior to induction of anesthesia, iv 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 two groups were identical. Fifty per cent of patients 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.(ABSTRACT TRUNCATED AT 250 WORDS)