CARDIOPULMONARY BYPASS TIME AND RENAL-FUNCTION

Abstract

Patients undergoing open-heart surgery were divided into 2 groups according to cardiopulmonary bypass time: in group 1 the bypass time was less than 60 min (25 patients) and in Group 2 more than 60 min (25 patients). Renal function parameters were investigated preoperatively, during the operation and for 2 days postoperatively. The urine volume and excretion of Na and K increased significantly in both groups during the bypass period compared to the values of the pre-bypass period. Significant differences (P < 0.001) were seen during the bypass period in free water clearance: -0.8 .+-. 0.6 ml/min in Group 1 and -0.2 .+-. 0.2 ml/min in Group 2, and in creatinine clearance: 114 .+-. ml/min in Group 1 and 60 .+-. 12 ml/min in Group 2. The inter-group differences in free water and creatinine clearances were significant (P < 0.001) from the bypass period to the 2nd day period. In group 2 urine osmolality was significantly lower and serum osmolality significantly higher from the bypass period to the 3rd day period compared to the values of Group 1. The excretion of Na and K was higher in Group 1 during bypass and postoperatively, and this was reflected in the serum values of Na and K. Signs of functional renal impairment were seen in the group with the longer perfusion. In this group the patients were older and had a higher preoperative serum creatinine mean value than the patients with the shorter perfusion. The mechanism of functional renal impairment was discussed.