Perioperative fluid accumulation and clinical outcomes after cardiac surgery: a systematic review and Bayesian...

Fluid accumulation is common in critically ill patients and has been associated with adverse outcomes. However, its impact on postoperative outcomes in cardiac surgery remains unclear.

To assess the association between perioperative fluid accumulation and clinical outcomes in adults undergoing cardiac surgery.

We conducted a systematic review and meta-analysis of observational studies and randomized controlled trials. PubMed, Embase, and the Cochrane Library were searched through February 2025. Eligible studies enrolled adults (≥ 18 years) undergoing cardiac surgery and compared liberal versus restrictive fluid strategies or fluid-positive versus fluid-restrictive states. Outcomes included all-cause mortality, acute kidney injury (AKI), hospital and intensive care unit (ICU) length of stay, duration of mechanical ventilation, ICU readmission, and postoperative atrial fibrillation (POAF). Certainty of evidence was assessed using the GRADE framework.

Eighteen studies (15,052 patients) were included. In pooled analyses, fluid accumulation was associated with increased mortality (OR 1.65; 95% CI 1.03-2.63; p = 0.04), and fluid restriction was associated with decreased hospital stay (MD -1.02 days; 95% CI -1.67 to -0.37; p = 0.002). Bayesian analysis supported these findings, showing a 98.8% probability that restrictive fluid strategies reduce mortality and a 98.6% probability of shorter hospital stay. For AKI, the Bayesian model showed an 84.7% probability of benefit despite non-significant frequentist results. No significant associations were found for POAF, ICU stay, mechanical ventilation duration, or ICU readmissions. The certainty of evidence was low for randomized evidence and very low for observational data when assessed with GRADE.

Perioperative fluid accumulation may be associated with worse postoperative outcomes, but the certainty of evidence is limited by heterogeneity and methodological variability across studies. These findings should be interpreted as hypothesis-generating and underscore the need for high-quality randomized trials to clarify safe fluid exposure thresholds and the role of individualized perioperative fluid management.