TUBULAR NEPHROTOXICITY AFTER CARDIAC-SURGERY UTILIZING CARDIOPULMONARY BYPASS

Markers of renal tubular injury were examined in 21 patients (16 male, 5 female, mean age 57.4 years) undergoing cardiac surgery utilising c ardiopulmonary bypass. Postoperative urine outputs were very high (200 -250 ml/h at 1-2 h), decreasing to 100 ml/h by 6 h. Although creatinin e clearances did not vary significantly in the postoperative period (P = 0.16), significant changes were noted in the urinary concentrations of three tubular markers relative to creatinine concentration (P < 0. 001). Urinary Pz-microglobulin increased from negligible levels (media n 0.01 mg/mmol creatinine) to peak at 4 h (median 4.55 mg/mmol), in pa rt due to interference with its reabsorption by the plasma volume expa nder Haemaccel. Concentrations of the brush border antigen adenosine d eaminase binding protein increased 6-fold, from a median of 5.03 arbit rary units (AU)/mu mol to 31.2 AU/mu mol at 48 h. The lysosomal enzyme N-acetyl-beta-D-glucosaminidase increased nearly 4-fold, from 0.68 un its/mmol to 2.64 units/ mmol at 48 h. Our results suggest that cardiac surgery utilising cardiopulmonary bypass is associated with acute tub ular injury which can occur in the absence of overt changes in creatin ine clearance.