The determinants of fluid accumulation in critically ill children: a prospective single-center cohort study.

Background: Fluid accumulation (FA) is associated with morbidity and mortality in intensive care. We aimed to determine sources of FA in critically ill children admitted to pediatric intensive care.

Methods: Prospective cohort study of children in a university affiliated tertiary pediatric intensive care unit. Primary outcome was to describe contributors to fluid intake. Secondary outcomes were independent associations between fluid intake and FA > 5%, ventilator-free days, and intensive-care-free days.

Results: Of patients admitted to intensive care, 99/120 (83%) met eligibility criteria. Median total fluid intake was median [interquartile range (IQR)] 46.9 [30.3, 72.1] ml/kg/day, and median [IQR] fluid output was 26.3 [15.1, 49.8] ml/kg/day. The largest contributors to fluid intake were maintenance (37.4%; IQR 20.0, 57.3), nutrition (23.2%; IQR 6.8, 58.1), medications (7.8%; IQR 2.9, 21.8), and resuscitative fluid (4.2%; IQR 0, 18). Children with peak FA > 5% versus FA ≤ 5% had higher total fluid intake (67.8 vs. 30.3 ml/kg/day; odds ratio (OR) 1.09 [95% confidence interval (CI), 1.06, 1.14)] and output [36.9 vs. 19.5 ml/kg/day; OR 1.04 (95% CI, 1.02, 1.06)], and higher volumes of maintenance, nutrition, and medications, but not resuscitative fluid. Total fluid intake was independently associated with FA > 5% (OR 1.09; 95% CI 1.05, 1.14; p < 0.001). At 28 days, peak FA% was independently associated with fewer intensive-care-free days [Effect Size - 0.30 (95% CI - 0.45, - 0.16), p < 0.001)].

Conclusions: Higher fluid intake, rather than reduced output, was the predominant factor in FA, with maintenance fluid being the largest source of intake. Future research should evaluate the impact of optimized maintenance fluid calculations.