Association between estimated plasma volume status and risk of sepsis-associated acute kidney Injury: a retrospective cohort study using the MIMIC-IV database

Estimated plasma volume status (ePVS) is a simple, useful tool for assessing volume status. However, its prognostic value in sepsis-associated acute kidney injury (SA-AKI) remains unclear. This retrospective cohort study analyzed data from 15,789 patients with SA-AKI extracted from the MIMIC-IV database. The association between ePVS and mortality was evaluated using Cox regression and Kaplan-Meier analysis. Logistic regression was employed to assess the relationship between ePVS and renal recovery. All models were adjusted for demographics, comorbidities, laboratory values, and illness severity scores. Restricted cubic spline (RCS) model was applied to examine potential nonlinear relationships between ePVS and mortality risk. Among 15,789 eligible patients with SA-AKI, the 28-day mortality rate was 23.2%. Multivariate Cox regression analysis revealed that higher ePVS was associated with increased 28-day mortality (HR = 1.05, 95% CI 1.03-1.07, <i>p</i> < 0.001) and logistic regression analysis further indicated that elevated ePVS was correlated with reduced renal recovery (OR = 0.96, 95% CI: 0.94-0.99, <i>p</i> = 0.002). RCS demonstrated a nonlinear relationship between ePVS and mortality, with an inflection point identified at 5.47 dL/g. Using this cutoff, the high-ePVS group exhibited significantly higher 28-, 60-, and 180-day mortality and lower renal recovery than the low-ePVS group. ePVS is an independent risk factor for 28-day mortality in SA-AKI, showing a U-shaped association. These findings suggest ePVS may serve as a useful prognostic marker to guide fluid management strategies in SA-AKI.