The effect of sublingual nifedipine on coronary venous graft resistance immediately following cardiopulmonary bypass.

The purpose of this study was to determine the effects of sublingual nifedipine administered immediately after discontinuation of cardiopulmonary bypass on coronary graft resistance and systemic hemodynamics. Twenty patients were prospectively randomized into two groups; one given 10 mg sublingual nifedipine after weaning from bypass, the other given a placebo. Coronary graft blood flow was measured under blinded conditions and graft resistance calculated from measurements obtained with an electromagnetic flow probe applied directly to the graft prior to and 15 minutes after drug administration. Serum nifedipine levels were determined immediately before and 15, 30, and 60 minutes after sublingual administration. All patients receiving nifedipine had therapeutic serum levels. Graft resistance in patients given nifedipine decreased a statistically significant average of 27% and increased slightly, but not statistically significantly so, in patients given sublingual placebos. There were no differences between the two groups in cardiac index or pulmonary capillary wedge pressures. We conclude that the administration of sublingual nifedipine to patients in the immediate postbypass period results in therapeutic serum nifedipine levels and decreases coronary graft resistance without affecting cardiac performance.