Myocardial metabolism and coronary sinus blood flow during coronary artery surgery: effects of nitroprusside and nifedipine

The effects of nitroprusside and nifedipine on hemodynamics, coronary dynamics, and global myocardial metabolism were compared in two groups of patients undergoing elective coronary artery surgery, who were anesthetized with fentanyl, 100 micrograms/kg. After induction of anesthesia, either nitroprusside or nifedipine was started as follows: group S (n = 11) received nitroprusside at an initial rate of 1.3 micrograms/kg/min; group N (n = 9) received nifedipine at an initial rate of 0.7 micrograms/kg/min. Infusion rates were adjusted to maintain systolic blood pressure (SBP) between 80% and 120% of preinfusion (control) values. Control measurements were obtained 10 minutes after intubation. Then vasodilator infusion was started. Additional measurements were obtained 10 minutes after the start of infusion (before surgery) and after sternotomy. The mean (+/- SD) total dose requirements were: nitroprusside, 1.6 +/- 0.3 micrograms/kg/min; and nifedipine 1.1 +/- 0.7 micrograms/kg/min. The mean (+/- SD) total infusion time was: nitroprusside, 32 +/- 5 minutes; and nifedipine, 37 +/- 7 minutes. After 10 minutes of infusion there were decreases in SBP (p less than 0.001) and diastolic blood pressure (DBP; p less than 0.01) in group S. In group N only SBP decreased (p less than 0.01). At this time there were no significant changes in coronary sinus blood flow (CSBF) or myocardial oxygen consumption (MVO2) in either group. After stenotomy DBP remained decreased (p less than 0.05) in group S.(ABSTRACT TRUNCATED AT 250 WORDS)