Renal function in children undergoing cardiac operations.

Because we sometimes observed large amounts of uric acid crystals in the urine of infants and children after open-heart operations and since renal insufficiency from any cause can be a serious complication of cardiac procedures, 8 acyanotic and 5 cyanotic children were studied prospectively by comparing several preoperative and postoperative measures of renal function. There were no significant differences between the acyanotic and cyanotic groups in terms of age, time on cardiopulmonary bypass, or other preoperative variables. Postoperatively, children in both groups had a wide range of free water clearances (CH2O), with some values in the range reported to be diagnostic of renal insufficiency in adults. Since none of these children had renal insufficiency by other criteria, CH2O may not be as reliable an indicator of renal insufficiency in children. The major difference between the cyanotic and acyanotic groups was seen in postoperative serum uric acid levels (SUA); the mean SUA levels in the acyanotic and cyanotic groups were 5.3 +/- 0.5 mg/dl (+/- standard error of the mean) and 10.4 +/- 1.7 mg/dl (range, 8.0 to 15.5 mg/dl), respectively. Since the hyperuricemia in the cyanotic children could not be related to increased exogenous administration or decreased renal excretion, it is probably caused by increased endogenous production and may be related to the resolution of the cyanotic state.