Reliability of the fluid balance in neonates

To assess the reliability of fluid balance charts in neonates.

An observational study in 170 nonbreastfed neonates, requiring continuous monitoring on a high-care unit, but not critically ill. The fluid balance was compared to daily body weight changes using Bland-Altman analysis. Differences more than 20% of daily fluid intake were considered clinically relevant.

The mean gestational age was 36 + 2 weeks (SD 18.7 days) and mean birth weight 2782 g (SD 749 g). The mean difference between 394 fluid balances over 24 h (in mL) and daily weight changes (in g) was -12.1 (limits of agreement -128.1 to 103.8). In 40% of comparisons, the difference with daily weight change was more than 20% of daily fluid intake.

Fluid balance charts both over- and underestimate body weight changes in an unpredictable pattern and are therefore unreliable as a single measure of fluid status in neonates.