Haemodynamic and metabolic effects of prophylactic nitroglycerin infusion in the immediate period following coronary artery bypass grafting.
This is a preliminary report of work in progress to assess the effects of prophylactic nitroglycerin infusion in patients undergoing coronary artery vein grafting. So far 14 patients have been studied. They were divided into two groups to receive either nitroglycerin (1 microgram kg-1 min-1) or placebo (5% dextrose). The infusion was commenced on removal of the aortic cross-clamp after completion of the distal anastomoses of the grafts. During cardiopulmonary bypass myocardial protection was provided by cold potassium cardioplegia and systemic hyopthermia. For 2 hours after cessation of cardiopulmonary bypass simultaneous samples of coronary sinus and femoral arterial blood were taken to estimate lactate concentrations and oxygen saturation. No differences were found between the groups. At the same times haemodynamic measurements were made. There was a statistically significant increase in cardiac index in the nitroglycerin group up to 30 minutes post cardiopulmonary bypass. There was also a statistically significant fall in systemic and pulmonary vascular resistances with no differences in systemic or pulmonary arterial pressures. There was no difference in central venous or pulmonary capillary wedge pressures. Patients receiving nitroglycerin seemed more stable cardiovascularly than those receiving placebo. In conclusion nitroglycerin improves cardiac output in the immediate post bypass period following cold potassium cardioplegia.