Fluid Creep as an Independent Predictor of Fluid Overload and Mortality in Critically Ill Patients: A Cohort Study

Background: Fluid overload (FO) is a frequent ICU complication and an important predictor of adverse outcomes. While classically attributed to resuscitative fluids, recent data emphasize the contribution of non-therapeutic “fluid creep” from medication diluents and carrier infusions. This study examined associations between fluid creep, FO, acute kidney injury (AKI), and mortality, and explored the predictive value of the modified Renal Angina Index (mRAI) for early AKI risk stratification; Methods: A retrospective cohort of 250 critically ill adults (ICU stay ≥72 h) admitted to a mixed medical–surgical ICU between May 2021 and November 2024 was analyzed. All fluids administered during the first 72 h were categorized and indexed to ideal body weight. Fluid creep included drug diluents, carriers, and flushes. FO% was calculated as [(Cumulative Fluid Balance)/IBW] × 100; Results: Fluid creep was higher in non-survivors (5,183 ± 2,541 vs. 4,354 ± 2,171 mL; p = 0.008) and correlated with FO, cumulative balance, and total input (r = 0.41–0.43; p < 0.001). Creep and FO independently predicted ICU mortality. Abnormal mRAI scores were associated with FO and early AKI; Conclusions: Fluid creep and FO were independent mortality predictors. Routine monitoring and minimization of creep, along with structured de-resuscitation protocols, may improve outcomes in critically ill adults.