EFFECTS OF EXTRACORPOREAL-CIRCULATION ON RENAL-FUNCTION IN CORONARY SURGICAL PATIENTS

We prospectively studied perioperative changes of renal function in 12 previously normal patients (plasma creatinine <1.5 mg/dL) scheduled f or elective coronary surgery. Glomerular filtration rate (GFR) and eff ective renal plasma flow (ERPF) were measured with inulin and I-125-hi ppuran clearances before induction of anesthesia, before cardiopulmona ry bypass (CPB), during hypo- and normothermic CPB, after sternal clos ure, and 1 h postoperatively. Renal and systemic vascular resistances were calculated. Urinary N-acetyl-beta-D-glucosaminidase (NAG) and pla sma and urine electrolytes were measured, and free water, osmolal, and (creatinine clearances, and fractional excretion of sodium and potass ium were calculated before and after surgery. I-125-hippuran clearance was lower than normal in all patients before surgery. During hypother mic CPB, ERPF increased significantly (from 261 +/- 107 to 413 +/- 261 mL/min) and returned toward baseline values during normothermia. GFR was normal before and after surgery and decreased nonsignificantly dur ing CPB. Filtration fraction was above normal before surgery and decre ased significantly during CPB (038 +/- 0.09 to 0.18 +/- 0.06). Renal v ascular resistance (RVR) was high before surgery and further increased after sternotomy (from 18,086 +/- 6849 to 30,070 +/- 24,427 dynes . s . cm(-5)), decreasing during CPB to 13,9647 +/- 14,662 dynes . s . cm (-5). Urine NAG, creatinine, and free water clearances were normal in all patients both pre- and postoperatively. Osmolal clearance and frac tional excretion of sodium increased postoperatively from 1.54 +/- 0.0 6 to 12.47 +/- 11.37 mL/min, and from 0.44 +/- 0.3 to 6.07 +/- 6.27, r espectively. We conclude that renal function does not seem to be adver sely affected by CPB. Significant functional alterations, such as decr eased ERPF and increased RVR, were found before and during surgery, pr eceding CPB. These periods could contribute to postoperative renal dys function.