After approval of the regional ethics committee, patients (n=16) undergoing combined cardiac surgery procedures during normothermic CPB will be included after informed consent. Systemic and renal variables will be measured by pulmonary artery and renal vein catheters. Glomerular filtration rate (GFR) will be measured by renal extraction of 51Cr-EDTA and renal blood flow (RBF) by the infusion clearance technique for para-aminohippuric acid (PAH) corrected for by renal extraction of PAH. Repeated measures ANOVA followed by Fisher's PLSD post-hoc test were used for statistical analyses