Assessing fluid balance in critically ill pediatric patients

Monitoring fluid balance (FB) in a pediatric intensive care unit (PICU) is crucial to assess fluid overload. Pediatric intensivists (PI) frequently use the fluid intake minus output (FIMO) or FIMO with adjustments for insensible fluid loss (AFIMO). However, the accuracy of FIMO/AFIMO has never been tested in critically ill children. We designed a prospective, monocentric cohort study in a PICU of a university hospital. Body weight (BW) was measured in all children consecutively admitted to PICU and 24 h later. Every 12 h, the nurses calculated FIMO/AFIMO. Time burden and convenience of each procedure (median; [interquartile range]) were recorded and compared using a Wilcoxon test. Data were analysed using linear regression (r ² coefficient) and the Bland-Altman plot (mean difference ± standard deviation; absolute mean difference), with a 300-ml variation of FB considered clinically relevant. Sixty consecutive patients, 304-day [39–1,565] old with admission weight of 9.2 kg [4.4–17.8] were included. Although correlations between FIMO/AFIMO and BW changes (BWC) were strong (r ² _FIMO = 0.63, p < 0.0001 and r ² _AFIMO = 0.72, p < 0.0001, respectively), agreement between FIMO/AFIMO and BWC were over 300 mL (−0.305 ± 0.451, 0.382 L and −0.007 ± 0.447, 0.302 L, respectively). No significant differences were noted between FIMO/AFIMO and BWC measurements for time burden (5 min [5–10] vs. 5 min [5–10], p = 0.84) or convenience (1 min [1–2] vs. 1 min [0–1.3], p = 0.13).Conclusion: Because agreement between FIMO/AFIMO and BWC is poor during the first 24 h after admission into PICU, PIs may reserve FIMO/AFIMO to monitor FB in patients with absolute contraindications of BW measurements.