[Effect of cardiopulmonary bypass on the renal tubular cell--the importance of the changes in the ratio of creatinine to blood urea nitrogen].

We examined the effect of cardiopulmonary bypass on the renal tubular cell in 19 adult patients undergoing cardiac surgery. The ratio of creatinine to blood urea nitrogen (BUN/Cr) decreased in the early period of cardiopulmonary bypass, because of increased serum creatinine and unchanged blood urea nitrogen. N-acetyl-beta-D-glucosaminidase (NAG) index in the intra- and postbypass period was higher than that in the preoperative period. Creatinine clearance (CCr) on the 7th postoperative day and the difference of BUN/Cr between preoperative period and 30 min after initiation of cardiopulmonary bypass (delta BUN/Cr 30 min) correlated significantly with the postoperative NAG index. The results suggest that cardiopulmonary bypass impaired the renal tubular cell, and renal tubular injury deteriorated the glomerular filtration in the postbypass period, and that creatinine production increased in the early period of cardiopulmonary bypass. delta BUN/Cr 30 min may predict the intraoperative renal tubular injury.