Effects of nimodipine on cerebral blood flow and neuropsychological outcome after cardiac surgery. Thirty-five patients undergoing cardiac surgery requiring cardiopulmonary bypass (CPB) were allocated randomly in a prospective double-blind study to receive either nimodipine 0.5 micrograms kg-1 min-1 or placebo. Cerebral blood flow (CBF) was measured during and immediately after CPB. Neuropsychological tests were performed 6 months after surgery to determine any relationship between ischaemic damage and CBF and administration of nimodipine. There were no differences in CBF between the nimodipine (n = 18) and placebo groups (n = 17). Significant changes in neuropsychological tests were found in six patients tested 6 months after surgery but there were no conclusive signs of ischaemic damage. The nimodipine-treated group performed better in tests of verbal fluency and visual retention, suggesting that some memory functions were preserved better in this group. 