The long-term effects of developing renal failure post-coronary artery bypass surgery, in patients with normal preoperative renal function

Abstract

Renal failure post-cardiac surgery is associated with an increased in hospital morbidity and mortality. We investigated the effect of new onset renal risk, injury or failure [risk, injury, failure, loss and end-stage kidney disease (RIFLE)] post-coronary artery bypass graft (CABG) on long-term survival, in patients with normal preoperative renal function. The effect of developing postoperative renal risk, injury or failure as defined by the RIFLE criteria on the long-term survival of patients undergoing isolated CABG with a normal renal function was studied. Two separate multivariate analyses were performed based on preoperative serum creatinine or glomerular filtration rate (GFR). Univariate, multivariate, interaction and confounding factor analyses were performed. A total of 4029 isolated CABG patients were included in the study. 46.5% of patients had chronic kidney disease (CKD) stage 1 (GFR ≥90 ml/min/1.73 m(2)), 50.4% had CKD stage 2 (GFR 60-89 ml/min/1.73 m(2)) and 3.1% had CKD stage 3 (GFR 30-59 ml/min/1.73 m(2)) on admission, despite having a normal serum creatinine. The study group had a median follow-up of 3.6 years (95% CI 0-13.7). Renal risk, injury and failure were associated with a significantly reduced long-term survival (P < 0.001). In patients with normal preoperative serum creatinine, Cox regression analysis revealed that age (P = 0.026), preoperative creatinine (P =0.006) and logistic EuroSCORE (P < 0.0001) were significant factors in addition to the development of postoperative renal risk, injury or failure (P < 0.0001), with regard to determining long-term survival. A confounding factor analysis revealed that discharge creatinine (P = 0.0001) and discharge GFR (P = 0.0006) were significant determinants of long-term survival. In patients with a preoperative GFR >90 ml/min, Cox regression analysis revealed that diabetes (P = 0.004) sex (P = 0.019) and logistic EuroSCORE (P < 0.0001), were also significant factors in addition to the development of postoperative renal risk, injury or failure (P = 0.0001) with regard to determining long-term survival. A significant interaction between diabetes and the development of renal risk, injury or failure exists (P = 0.04). A confounding factor analysis revealed that discharge creatinine was a significant determinant (P = 0.0001) of long-term survival, and discharge GFR was not. Despite being a biochemically reversible process, the development of renal risk, injury and failure as defined by the RIFLE criteria post-cardiac surgery in patients with a normal preoperative renal function is associated with a significantly worse long-term outcome.