Weight-adjusted fluid balance and its impact on days alive without life support in critical illness - an observational cohort study.

Abstract

BACKGROUND: Fluid accumulation (FA) and fluid depletion (FD) are associated with worse outcomes in critically ill patients. However, it is not known at what threshold a positive or negative fluid balance leads to impaired organ function and impacts outcomes. The aim of this study was to investigate the association between the degree of weight-adjusted fluid balance (wFB) and the days alive without life support (DAWOLS) and to identify proposed wFB thresholds. METHODS: Retrospective, single-centre cohort study including adult ICU patients. The association between wFB three days after ICU admission and DAWOLS was examined. The lowest positive / highest negative wFB with a statistically significant and relevant association with DAWOLS was determined as threshold for a significant FA and FD, respectively. In addition, we analysed the association between FA / FD and mortality, organ support, length of stay, and delirium. RESULTS: In the 17'956 patients included in this analysis, we identified a wFB cut-off of +7% and -4% to be significantly associated with DAWOLS (p < 0.001). Using these cut-offs, FA (regression coefficient β -3.92 (95%-CI -4.37; -3.46), p < 0.001) as well as FD (-0.95 (-1.35; -0.54), p < 0.001) were significantly associated with DAWOLS. Furthermore, FA and FD were significantly associated with mortality, the need for organ support, a longer length of ICU and hospital stay, and delirium. CONCLUSIONS: When assessing the relationship between wFB and DAWOLS, the threshold for FA was a wFB ≥+7%, while FD could be defined with a wFB cut-off of ≤-4%. Both FA and FD were significantly associated with reduced DAWOLS, with a less robust association for FD.