Association of fluid creep and maintenance fluids on major adverse kidney events in critically ill patients – An observational cohort study

Background Fluid accumulation is a known risk factor of adverse renal outcomes in critically ill patients. A substantial proportion of the fluid burden in intensive care unit (ICU) patients arises from maintenance fluids and fluid creep. Whether these non-resuscitation fluids affect renal outcomes remains uncertain. Methods Retrospective cohort study of adult ICU patients admitted to a tertiary care center in Switzerland between January 2014 and December 2017. The primary objective was the association of fluid creep/maintenance fluid intake with major adverse kidney events within 30 days (MAKE30). Secondary endpoints included the individual components of MAKE30: mortality, renal replacement therapy (RRT), and persistent renal dysfunction. Associations were analysed using multivariable logistic regression adjusted for typical confounders. Results 12,716 patients were included, of whom 1812 (14%) experienced MAKE30. The median total volume of fluid creep/maintenance fluids until ICU discharge was 716 mL (Interquartile range IQR 329; 2128), corresponding to a median daily intake of 8 mL/kg (IQR 4; 15). Each additional milliliter of fluid creep/maintenance fluids per kilogram body weight per day was associated with MAKE30 (adjusted odds ratio aOR 1.004, 95% confidence interval CI 1.001–1.008; p = 0.016) and all its components, including 30-day mortality, RRT, and persistent renal dysfunction. Conclusion In a large mixed ICU cohort, higher exposure to fluid creep/ maintenance fluids was consistently associated with MAKE30 and its components. Fluid creep should be recognized as a modifiable component of fluid therapy. Future studies are needed to determine how reducing the dose of hidden fluids affects clinical outcomes.