Objectives: 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.
Methods: 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.
Results: 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.
Conclusions: 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.