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Agreement Between Measured Weight and Fluid Balance in Mechanically Ventilated Children in Intensive Care
Ben Gelbart1, Vanessa Marchesini2, Sudeep Kumar Kapalavai3
1Paediatric Intensive Care Unit, University of Melbourne, Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, VIC, Australia.
Insights
Weighing mechanically ventilated infants showed moderate agreement with fluid balance changes, though limits were wide. This method is safe and precise for estimating fluid status in intensive care.
Area of Science:
- Pediatric critical care medicine
- Neonatal physiology
- Medical device technology
Background:
- Accurate monitoring of fluid balance (FB) is crucial for critically ill infants, especially those on mechanical ventilation.
- Body weight (BW) changes are often used as a surrogate for FB, but their agreement and the safety of BW measurement in this population require investigation.
Purpose of the Study:
- To assess the agreement between changes in body weight (BW) and fluid balance (FB) in mechanically ventilated infants.
- To evaluate the precision and safety of BW measurement in this vulnerable patient group.
Main Methods:
- A prospective observational study was conducted in a tertiary pediatric intensive care unit (PICU).
- 61 infants following cardiac surgery were included, with BW and FB measurements taken at baseline, 24, and 48 hours.
- Bland-Altman analysis was used to assess the agreement between BW and FB changes.
Main Results:
- The mean bias between BW and FB changes exceeded 1% of baseline BW at 24 and 48 hours, with wide limits of agreement.
- Paired BW measurements demonstrated high precision (median difference ≤1% of BW).
- Weighing was safe, with no device dislodgments or changes in vasoactive therapies; however, connected device weight represented a significant proportion (2.7-3%) of infant BW.
Conclusions:
- Moderate agreement exists between changes in FB and BW, but the wide limits of agreement necessitate cautious interpretation.
- BW measurement is a safe and precise method for estimating fluid status changes in mechanically ventilated infants.
- The substantial weight of connected devices should be considered when interpreting BW measurements in this population.
Objectives:
To investigate the agreement between change in body weight (BW) and fluid balance (FB), and the precision and safety of BW measurement in mechanically ventilated infants in intensive care.
Design:
Prospective observational study.
Setting:
Tertiary PICU.
Patients:
Infants following cardiac surgery, at baseline, 24 hours, and 48 hours.
Interventions:
BW and FB measurement at three time points.
Measurements And Main Results:
Between May 2021 and September 2022, we studied 61 children. The median age was 8 days (interquartile range [IQR], 1.0-14.0 d). The median BW at baseline was 3,518 g (IQR, 3,134-3,928 g). Change in BW was -36 g (IQR, -145 to 105 g) and -97 g (IQR, -240 to -28 g) between baseline and 24 hours, and between 24 and 48 hours, respectively. Change in FB was -82 mL (IQR, -173 to 12 mL) and -107 mL (IQR, -226 to 103) between baseline and 24 hours, and between 24 and 48 hours, respectively. In Bland-Altman analyses, the mean bias between BW and FB at 24 and 48 hours was 54 g (95% CI, 12-97) and -43 g (95% CI, -108 to 23), respectively. This exceeded 1% of the median BW, and limits of agreement ranged from 7.6% to 15% of baseline BW. The precision of paired weight measurements, performed sequentially at each time interval, was high (median difference of ≤1% of BW at each time point). The median weight of connected devices ranged from 2.7% to 3% of BW. There were no episodes of tube or device dislodgments and no change in vasoactive therapies during weight measurements.
Conclusions:
There is moderate agreement between the changes in FB and BW, albeit greater than 1% of baseline BW, and the limits of this agreement are wide. Weighing mechanically ventilated infants in intensive care is a relatively safe and precise method for estimating change in fluid status. Device weight represents a relatively large proportion of BW.
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