Improvement of cardiac function after coronary artery bypass grafting surgery reduces the risk of postoperative acute kidney injury

BACKGROUND: Pre‐existing renal dysfunction is an independent risk factor for cardiac surgery‐associated acute kidney injury (AKI). We aimed to investigate whether the improvement of postoperative cardiac function after coronary artery bypass grafting (CABG) surgery would affect the risk of AKI in patients with different levels of baseline renal function. METHODS: Data were collected from patients who underwent CABG surgery from January 2018 to April 2019. Patients were divided into normal (GFR ≥ 90 ml/min/1.73 m(2)), non‐CKD (60≤GFR < 90 ml/min/1.73 m(2)), and CKD (GFR < 60 ml/min/1.73 m(2)) groups. Improvement in cardiac function was defined as △LVEF (postoperative LVEF–preoperative LVEF) ≥ 10% preoperative LVEF. Patients were further divided into subgroups according to postoperative cardiac function improvement. RESULTS: A total of 1365 patients were enrolled, including 793 (58.1%) in the normal group, 476 (34.9%) in the non‐CKD group, and 96 (7.0%) in the CKD group. The AKI incidence in the normal, non‐CKD, and CKD groups was 22.2%, 28.4%, and 40.6%, respectively. Patients with improved cardiac function in the non‐CKD and CKD groups had significantly lower AKI incidence than those without improved cardiac function (22.8% vs. 36.9%, p = .002% and 32.8% vs. 54.3%, p = .037, respectively). For non‐CKD patients with improved cardiac function, the serum creatinine at discharge was significantly lower than its preoperative serum creatinine (0.8 ± 0.5 vs 1.2 ± 0.9 mg/dl, p = .002). Multivariate logistic regression analysis showed that the improvement in cardiac function could reduce the risk for postoperative AKI in non‐CKD patients but not in CKD patients. CONCLUSIONS: For patients with renal dysfunction and mildly reduced eGFR (60≤GFR < 90 ml/min/1.73 m(2)), improved cardiac function after CABG surgery can reduce the serum creatinine level and reduce the risk for postoperative AKI.