Extracorporeal circulation reduces renal blood flow and function during cardiac surgery

Objectives: Acute renal dysfunction is a problem after extracorporeal circulation (ECC) with an incidence of 2.5–16%. We studied the influence on monoatrial and bicaval cannulation of renal function parameters and renal blood flow in a randomised, controlled clinical study.

Material and Methods: After ethical approval and written informed consent, 30 pts participated. In 15 pts monoatrial cannulation was performed (Gr. A), whereas in 15 pts bicaval cannulation (Gr. B) was used. Measurements were performed before and after induction of anaesthesia, during ECC and postoperatively. Renal blood flow (RBF) was measured by the Argon wash in technique. In addition glomerular filtration rate (GFR), renovascular resistance (RVR), filtration fraction (FF), renal plasma flow (RPF) and creatinine clearance (CC) as well as the renal excretion index (REI) were measured. Statistical analysis was performed by multivariate analysis of variance for repeated measures (MANOVA)

Results: In both groups, a decrease in renal plasma flow (p=0.04) was observed during the perioperative period. RBF decreased significantly in Gr. A (p=0.007), but remained unchanged in Gr. B. RVR increased to 80 dyn s cm-5 in Gr. A and to 150 dyn s cm-5 in Gr. B, however the difference between groups failed to reach statistical significance. Glomerular filtration rate, FF and CC were unchanged in both groups. Diuresis per minute and the free water clearance increased in both groups (p<0.05), whereas the urin osmolality significantly decreased.

Conclusions: Renal function was impaired after ECC, independent from the type of venous drainage. Decreased renal blood flow was observed in both groups. The results suggest that the entrance of cardioplegic infusion into the systemic circulation should be avoided in pts who are at risk for development of acute renal failure.