Association between fluid balance and weaning outcomes in patients with mechanical ventilation: a systematic review and meta-analysis.

BACKGROUND: Fluid balance during mechanical ventilation weaning has gained increasing attention, yet its association with weaning outcomes across different time windows remains unclear. OBJECTIVES: This systematic review and meta-analysis aimed to evaluate the association between fluid balance across different time windows and weaning outcomes in patients with mechanical ventilation. METHODS: This study was implemented according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Observational studies were systematically reviewed. The study protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO) (CRD420251109816). PubMed, Embase, Web of Science, and Cochrane Library were retrieved from inception to July 2025. Study quality was assessed using the Newcastle-Ottawa Scale (NOS). Meta-analysis was performed in Stata 15.0. RESULTS: Twenty-six studies encompassing 13,665 patients were included. More positive 24-hour pre-weaning fluid balance was associated with a higher risk of weaning failure in both continuous (standardized mean difference (SMD) = -0.31, 95% confidence interval (CI): -0.50 to -0.12, P = 0.001) and dichotomous adjusted analyses (odds ratio (OR) = 2.28, 95% CI: 1.89 to 2.74, P < 0.001). Cumulative fluid balance showed a consistent association (weighted mean difference (WMD) = -823.45 mL, 95% CI: -1189.65 to -457.25, P < 0.001). CONCLUSIONS: More positive fluid balance, particularly in the 24 h prior to weaning, was associated with an increased risk of weaning failure. Given the observational study designs, substantial heterogeneity, and potential residual confounding, the findings should be utilized to generate hypotheses rather than to provide a basis for clinical recommendations.