Risk Factors for Acute Kidney Injury after Coronary Artery Bypass Surgery and Its Detection Using Neutrophil Gelatinase-Associated Lipocalin

Abstract

Introduction: Acute kidney injury (AKI) is an important complication of cardiac surgery due to its high mortality. The aim of the present study was to detect the factors leading to AKI in patients who underwent coronary artery bypass surgery (CABS) and also to determine the optimal timing for detecting AKI using the biomarker neutrophil gelatinase-associated lipocalin (NGAL). Materials and Methods: The records of 375 patients who underwent CABS were reviewed in this case-control study. Ejection fraction (EF), common carotid artery intima-media thickness (CCA-IMT) and cross-clamp (C-C) time of the patients were recorded. Blood samples were taken from all patients on preoperative day 1 as well as 6, 12, 24, 36, 48 h and 7 days after operation. Biochemical parameters were studied in patients with and without AKI. Results: According to the Risk Injury Failure Loss End Stage criteria, 24 patients had renal risk, 17 had injury and 4 had failure. Postoperative 24-hour serum creatinine levels indicated the risk of renal dysfunction for only 4 patients in the AKI group. CCA-IMT, C-C time, haematocrit (HCT) and preoperative interleukin-6 levels were significantly higher in the AKI group than in the non-AKI group. Postoperative 6- and 12-hour NGAL levels in the AKI group correlated with postoperative 36-hour serum creatinine levels. The optimal cut-off values for postoperative 6- and 12-hour NGAL test were 310 and 283 ng/ml, respectively. The area under the curve was higher in the 12-hour NGAL test (p < 0.0086). Conclusion: The number of stenotic coronary arteries, EF, CCA-IMT and HCT are all important risk factors. Early postoperative NGAL results were highly specific for the early recognition of AKI.