How a positive fluid balance develops in acute kidney injury: A binational, observational study

Abstract

PurposeA positive fluid balance (FB) is associated with harm in intensive care unit (ICU) patients with acute kidney injury (AKI). We aimed to understand how a positive balance develops in such patients. MethodsMultinational, retrospective cohort study of critically ill patients with AKI not requiring renal replacement therapy. ResultsAKI occurred at a median of two days after admission in 7894 (17.3%) patients. Cumulative FB became progressively positive, peaking on day three despite only 848 (10.7%) patients receiving fluid resuscitation in the ICU. In those three days, persistent crystalloid use (median:60.0 mL/h; IQR 28.9–89.2), nutritional intake (median:18.2 mL/h; IQR 0.0–45.9) and limited urine output (UO) (median:70.8 mL/h; IQR 49.0–96.7) contributed to a positive FB. Although UO increased each day, it failed to match input, with only 797 (10.1%) patients receiving diuretics in ICU. After adjustment, a positive FB four days after AKI diagnosis was associated with an increased risk of hospital mortality (OR 1.12;95% confidence intervals 1.05–1.19;p-value <0.001). ConclusionAmong ICU patients with AKI, cumulative FB increased after diagnosis and was associated with an increased risk of mortality. Continued crystalloid administration, increased nutritional intake, limited UO, and minimal use of diuretics all contributed to positive FB. Key pointsQuestionHow does a positive fluid balance develop in critically ill patients with acute kidney injury?FindingsCumulative FB increased after AKI diagnosis and was secondary to persistent crystalloid fluid administration, increasing nutritional fluid intake, and insufficient urine output. Despite the absence of resuscitation fluid and an increasing cumulative FB, there was persistently low diuretics use, ongoing crystalloid use, and a progressive escalation of nutritional fluid therapy.MeaningCurrent management results in fluid accumulation after diagnosis of AKI, as a result of ongoing crystalloid administration, increasing nutritional fluid, limited urine output and minimal diuretic use.