Objectives: To evaluate the effects on renal function of continuously administered nifedipine during cardiopulmonary bypass (CPB) in patients undergoing cardiac surgery.
Design: The study was prospective, randomized, and controlled.
Setting: The study was performed in the Department of Anesthesia and intensive care unit of a regional hospital in Italy.
Participants: Thirty-four patients scheduled for elective coronary artery surgery; all patients had preoperative renal and hemodynamic function within normal limits.
Interventions: The patients were randomly divided into two equal groups: nifedipine and control. Twenty patients were included in the study: 10 patients in the nifedipine group (group A) and 10 patients in the control group (group B). In group A, nifedipine was continuously administered during CPB at an infusion rate ranging from 0.24 to 0.59 micrograms/kg/min to maintain the mean systemic arterial pressure (MAP) between 60 and 70 mmHg. In group B, increases of MAP above 70 mmHg were treated with IV boluses of urapidil (5 mg).
Measurements and main results: Renal function was studied using creatinine clearance (CRCL), determined before, during, and after the operation, and the glomerular filtration rate (GFR) was measured the day before and after the operation by plasma and urine clearance of 51-chromium edetic acid (51Cr-EDTA). Hemodynamic monitoring was performed using a pulmonary artery catheter. In comparison with preoperative determinations, CRCL and GFR values increased significantly after CPB (p < 0.001) and after the operation (p < 0.01) in the patients treated with nifedipine, whereas the two parameters showed a small and not significant reduction at the same times in the control patients. Hemodynamic function was well maintained in all patients throughout the study.
Conclusions: It is concluded that, besides the maintenance of adequate hemodynamics, a continuous infusion of nifedipine during CPB can be an additional therapeutic tool to protect renal function in cardiac surgical patients.