Impact of preoperative occult renal dysfunction on early and late prognosis in elderly patients with coronary artery bypass in China

Background Renal dysfunction is related to the poor outcomes of cardiac surgery. Preoperative occult renal dysfunction (PORD) is defined as patients with normal serum creatinine (Scr) but the glomerular filtration rate (GFR) less than 60 ml/min/1.73m2. However, there is no report on prognosis of elderly PORD patients undergoing coronary artery bypass grafting (CABG). This problem deserves further exploration. Methods Totally 1103 patients undergoing CABG with normal Scr and age ≥ 70 years old were enrolled. The estimated GFR (eGFR) of each patient was monitored using the Berlin initiative study formula. The patients were divided by eGFR into PORD group and control group. Propensity score matching was used to adjust preoperative characteristics. Univariate and multivariate analyses were performed to identify risk factors for postoperative acute kidney injury (AKI) and postoperative mortality. The Kaplan-Meier method was applied to estimate survival rates. A multivariate cox regression model was used to analyze the impacts of factors on long-term survival. Results Elderly patients with normal Scr had high PORD proportion (27.65%). The PORD group had significantly higher preoperative Cr (99.20 ± 12.74 vs. 71.57 ± 11.96), postoperative AKI rates (39.13% vs. 17.75%) and postoperative mortality (5.80% vs. 1.81%) compared with control group. PORD was a significant risk factor for postoperative mortality (OR = 11.648) and postoperative AKI (OR = 2.731). PORD was also a significant risk factor for long-term death after CABG (HR = 1.724). Conclusions PORD is a risk factor for postoperative AKI and short- and long-term death in elderly patients undergoing CABG. eGFR shall be used to assess preoperative renal function.