Association between estimated plasma volume status and acute kidney injury in adult patients after coronary artery bypass grafting

FU Bing-rong; HE Hai-lin; GU Xiao-lin; BAO Rong-xing; LI Jie

doi:10.3969/j.issn.1009-8933.2025.04.005

Abstract：Background Acute kidney injury (AKI) is a common and serious complication following coronary artery bypass grafting (CABG), with an incidence rate ranging from 4% to 28%. The estimated plasma volume status (ePVS)—a novel marker calculated from routine hematocrit and hemoglobin levels—reflects both volume overload and hemodilution, which are potential contributors to renal impairment. Nevertheless, the relationship between ePVS and AKI in patients undergoing CABG remains poorly understood. Therefore, this study aimed to investigate the association of ePVS with the risk of AKI in adult patients who underwent CABG. Methods This retrospective cohort study utilized data from the Medical Information Mart for Intensive Care (MIMIC)-IV database, covering the period from 2008 to 2019. The primary outcome was the occurrence of AKI following admission to the intensive care unit (ICU). Hematocrit and hemoglobin levels were measured within 24 hours after ICU admission. The ePVS was calculated using the Strauss-derived Duarte formula: ePVS = [100 - hematocrit (%)] / hemoglobin (g/dL). AKI was defined in accordance with the 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 three groups based on the ePVS tertiles (low: ≤6.30; middle: 6.30-8.08; high: >8.08). Multivariate logistic regression and subgroup analyses were applied to explore the association of the ePVS with the risk of AKI. Furthermore, we also examined the association of ePVS with AKI by employing generalized additive models. Results A total of 3,388 patients were included in the final analysis, of whom 2,573 (75.94%) developed AKI. Following multivariable adjustment, each unit increase in ePVS was associated with a 9% increase in the odds of AKI (OR: 1.09, 95% CI: 1.05-1.14; P < 0.001). When analyzed by ePVS tertiles, the highest tertile demonstrated a significantly elevated AKI risk compared with the lowest tertile (OR: 1.48, 95% CI: 1.18-1.86, P = 0.0007), with a significant dose-response relationship observed across tertiles (P for trend < 0.001). Subgroup analyses further indicated that the association between ePVS and AKI was more pronounced among patients with pre-existing renal or peripheral vascular disease and was statistically significant only in White patients. Conclusions ePVS was independently associated with an increased risk of AKI in adults undergoing CABG. These findings supported the potential utility of ePVS as a simple, economical clinical tool for early identification of patients at high risk for AKI following cardiac surgery. [S Chin J Cardiol 2025;26(4):249-258]