The effect of nitrous oxide on renal function in open heart surgery

Abstract

The renal function of 20 patients undergoing open-heart surgery was investigated pre-, per- and postoperatively. The patients were anaesthetized with a combination of morphine, halothane, oxygen and nitrous oxide (the nitrous oxide group), and the remaining ten with a combination of morphine, halothane, oxygen and air (the air group). The renal function tests included urine flow, sodium and potassium excretion, and creatinine and free water clearance. As a consequence of the anaesthesia, the mean arterial pressure declined half an hour after induction, being lower than the preoperative level by 15% (p less than 0.001) in the nitrous oxide group and lower by 11% (p less than 0.05) in the air group. At the same time the urine sodium/potassium ratio was 1.3 in the nitrous oxide group and 1.9 in the air group. Free water clearance was significantly (p less than 0.01) greater in the air group. During the perfusion the sodium/potassium excretion ratio was 1.7 in the nitrous oxide group and 4.1 in the air group (p less than 0.01). On the second day, creatinine clearance was significantly lower in the nitrous oxide group than in the air group (p less than 0.05). On the third day, urine flow was significantly higher and urine osmolality significantly lower (p less than 0.05) in the air group than in the nitrous oxide group.