The effect of preoperative renal dysfunction with or without dialysis on early postoperative outcome following cardiac surgery

Abstract

Objectives: Although previous studies have shown increased mortality in renal dysfunction patients undergoing cardiac surgery, there is lack of data on the pattern of postoperative complications that occur in such patients and their distribution among dialysis and non-dialysis dependent renal dysfunction. Methods: This is a retrospective review of prospectively collected data over 8 year period of cardiac surgery patients. Our cohort consisted of 3598 consecutive patients divided into: normal kidneys (n = 3276, 91%), renal dysfunction (n = 277, 8%) and dialysis (n = 45, 1%). Postoperative complications and mortality were analysed. Multivariate analysis was conducted to adjust for the potential confounders in the association between renal dysfunction and postoperative complications. Results: Univariate analysis showed increased risk of the following complications among renal dysfunction and dialysis patients: low cardiac output, arrhythmias, reoperation, prolonged ventilation, readmission to intensive care, blood transfusion and prolonged hospital stay. Mortality rate was highest in dialysis patients compared to renal dysfunction and normal kidney patients (11% vs. 7% vs. 3%, respectively p-value <0.001). Multivariate analysis showed that renal dysfunction with or without dialysis is an independent predictor of postoperative low cardiac output, blood transfusion, prolonged ventilation, and mortality. The odd ratios were higher for dialysis than non-dialysis dependent patients. This effect persisted after adjusting for potential confounders such as age and gender. Conclusion: The presence of renal dysfunction preoperatively increases the rate of postoperative complications and mortality following cardiac surgery. Prior knowledge of these complications can help in developing preventative strategies to reduce the associated risk.