Divergence Between Net Fluid and Weight-Based Evaluation in Calculating Cumulative Fluid Balance

Area of Science:

• Pediatric critical care medicine
• Clinical fluid management
• Intensive care unit (ICU) research

Background:

• Standardizing fluid balance calculations in the ICU remains a challenge.
• Understanding the relationship between different fluid balance calculation methods is limited.
• Accurate fluid balance is crucial for managing critically ill patients.

Purpose of the Study:

• To quantify the agreement between cumulative fluid balance calculated from fluid intake and output (CFBf) and from serial weights (CFBw).
• To analyze these differences in critically ill children during their first week of ICU admission.
• To identify potential discrepancies in fluid balance assessment methods.

Main Methods:

• Retrospective, multicenter, federated observational study across six pediatric ICUs.
• Analysis of 8,895 pediatric patients representing 12,388 ICU encounters.
• Bland-Altman analyses to assess agreement between CFBf and CFBw, stratified by ICU day and patient subgroups.

Main Results:

• Cumulative fluid balance from fluid intake/output (CFBf) consistently exceeded cumulative fluid balance from weights (CFBw) across all subgroups.
• The mean difference between CFBf and CFBw increased significantly over time (days 0-3: 2.7% vs. days 4-7: 8.1%).
• Greater divergence was observed in neonates and patients with early anchor weights.

Conclusions:

• CFBf consistently overestimates fluid balance compared to CFBw, with increasing divergence during the ICU stay.
• Clinicians must recognize these method-specific differences and prioritize frequent patient weights.
• Future research should correlate fluid balance methods with patient outcomes to determine the most clinically relevant approach.