Association between red cell distribution width and acute kidney injury in adult patients after coronary artery bypass grafting

DU Liu-yi; GU Xiao-lin; XU Xiao-feng; ZHANG Han-jun; XIE Xue-jun

doi:10.3969/j.issn.1009-8933.2025.04.003

Abstract：Background Acute kidney injury (AKI) is a common and serious complication following coronary artery bypass grafting (CABG), with reported incidence rates ranging from 4% to 28%. Red cell distribution width (RDW), calculated as the standard deviation of erythrocyte size divided by mean corpuscular volume, reflects the heterogeneity in red blood cell volume. Easily obtained from routine blood tests, RDW is increasingly recognized as a prognostic marker for various adverse clinical outcomes. Previous studies have also indicated a correlation between elevated RDW levels and declining renal function, as measured by estimated glomerular filtration rate. However, the specific relationship between RDW and the risk of AKI in patients undergoing CABG remains inadequately characterized. This study aimed to investigate the association between RDW and AKI incidence in this surgical population. Methods In this secondary retrospective cohort study, data of patients who underwent CABG were extracted from the Medical Information Mart for Intensive Care (MIMIC)-IV database (2008-2019). The primary outcome was the occurrence of AKI as a postoperative complication following CABG, which was identified after intensive care unit (ICU) admission. RDW was measured within 24 hours on admission to ICU. AKI was defined according to Kidney Disease Improving Global Outcomes (KDIGO) criteria. Multivariable logistic regression models were used to adjust for demographics, comorbidities, and critical laboratory markers. Patients were stratified into RDW tertiles (T1: ≤13.1%; T2: 13.1%-13.8%; T3: ≥13.8%). Multivariate logistic regression and subgroup analyses were applied to explore the association of the RDW with the risk of AKI. Furthermore, we also examined the association of RDW with AKI by employing restricted cubic splines (RCS). Results A total of 3,388 patients who underwent CABG were included in this study, of whom 2563 (75.65%) had AKI. According to the multivariate regression models, the RDW demonstrated a significant positive correlation with the risk of AKI after comprehensive covariate adjustment. When each unit of RDW was increased, the risk of AKI in patients with CABG increased 10% (OR: 1.10, 95% CI: 1.03-1.18, P=0.0063). In addition, when the RDW was analyzed by tertiles, patients in the high tertile (OR: 1.33, 95% CI: 1.08-1.64, P=0.0072) presented a progressively higher risk of AKI than those in the low tertile, with a significant dose-response trend (P for trend <0.01). The subgroup analysis demonstrated that the positive association between elevated RDW and increased risk of AKI following CABG was robust and consistent across most major patient subgroups defined by demographics and comorbidities. The strength of this association was notably amplified in patients with pre-existing renal disease and in older patients (>65 years) and White race (P<0.05), suggesting a particularly prominent relationship between RDW and AKI risk in these specific populations. The lack of statistical significance in peripheral vascular disease subgroups required further investigation (P>0.05). Conclusions In ICU patients who received coronary revascularization by CABG, an elevated RDW demonstrated a positive correlation with the risk of AKI.