[Effects of open-heart surgery on renal function]

Effects of open-heart surgery on renal function were studied in 38 patients who had uneventful postoperative course with no sign of acute renal failure. Of these, 19 underwent aorto-coronary bypass grafting (Group 1) and 19 underwent valve replacement (Group 2). During cardiopulmonary bypass (CPB), renal plasma flow (RPF) and glomerular filtration rate (GFR) significantly decreased in both groups as compared to the preoperative values. The decreased GFR remained significantly low on the day of operation in both groups and returned to the preoperative level on the 1st postoperative day (POD) in group 1 and on the 3rd POD in group 2. On the other hand, plasma antidiuretic hormone (ADH) level markedly increased during CPB and remained significantly higher than the preoperative level through the 1st POD. Despite the decreased GFR and increased ADH, however, urinary flow markedly increased during CPB in both groups and remained at significantly higher level than the preoperative values through the 3rd POD in group 1 and through the 5th POD in group 2. Fractional excretion of sodium significantly increased during CPB in both groups and remained high through the 1st POD in group 1 and through the 3rd POD in group 2. These data demonstrate that the renal function of urine concentration is disturbed in the early phase following open-heart surgery even in the patients who have uneventful postoperative course.