Changes in glomerular filtration rate after cardiac surgery with cardiopulmonary bypass in patients with mild preoperative renal dysfunction

Background. Cardiac surgery with cardiopulmonary bypass (CPB) is commonly perceived as a risk factor for decline in renal function, especially in patients with preoperative renal dysfunction. There are few data on the effects of CPB on renal function in patients with mild preoperative renal dysfunction. The purpose of this study was to evaluate renal function in patients with pre-existing mild renal dysfunction undergoing cardiac surgery with CPB.Methods. In a multicentre study cohort we measured prospectively the glomerular filtration rate (GFR) by radioactive markers both before operation and on the 7th postoperative day in cardiac surgical patients with preoperative serum creatinine > 120 mu mol l(-1) (n=56). In a subgroup of patients (n=14) in addition to the GFR, the effective renal plasma flow (ERPF) and the filtration fraction (FF) were measured.Results. While preoperative GFR [77.9 (25.5) ml min(-1)] increased to 84.4 (23.7) ml min(-1) (P=0.005) 1 week after surgery, ERPF did not change [295.8 (75.2) ml min(-1) and 295.9 (75.9) ml min(-1), respectively; P=0.8]. In accordance, the FF increased from 0.27 (0.05) (before operation) to 0.30 (0.04) (Day 7, P=0.01).Conclusion. Our results oppose the view that cardiac surgery with CPB adversely affects renal function in patients with preoperative mild renal dysfunction and an uncomplicated clinical course.