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Variability in Pediatric Ideal Body Weight Calculation: Implications for Lung-Protective Mechanical Ventilation
Shan L Ward1, Carson M Quinn2, Martina A Steurer1
1Division of Critical Care, Department of Pediatrics, UCSF Benioff. Children's Hospital San Francisco, San Francisco, CA.
Insights
Determining ideal body weight in children is challenging, with significant variations among calculation methods. The McLaren method is recommended for calculating ideal body weight in pediatric acute respiratory distress syndrome (PARDS) due to its consistency and impact on tidal volume.
Area of Science:
- Pediatric Critical Care Medicine
- Respiratory Physiology
- Clinical Nutrition
Background:
- No universally accepted standard exists for determining ideal body weight (IBW) in pediatric populations.
- Accurate IBW is crucial for appropriate medical interventions, particularly in critically ill children.
Purpose of the Study:
- To compare four common IBW calculation methods in children.
- To assess the agreement between these methods.
- To evaluate the impact of IBW variance on tidal volume (TV) settings in mechanically ventilated children with pediatric acute respiratory distress syndrome (PARDS).
Main Methods:
- Post hoc analysis of data from four multicenter PARDS studies involving 589 patients across 26 academic pediatric intensive care units (PICUs).
- Calculated IBW using National Center for Health Statistics (NCHS), McLaren, Moore, and Body Mass Index (BMI) methods.
- Compared methods by assessing calculation success rates, Bland-Altman analysis for agreement, and differences in prescribed TV (6 mL/kg IBW).
Main Results:
- Only 55% of patients had IBW calculable by all four methods; BMI method succeeded in only 61% due to lack of validation in children under 2 years.
- NCHS, McLaren, and Moore methods calculated IBW in >=90% of subjects.
- Significant IBW variance observed, especially in children >=10 years, with greatest discrepancies between Moore and BMI methods.
- The McLaren method demonstrated the best agreement with other methods and resulted in similar TV for 2-10 year olds and lower TV for those >=10 years.
Conclusions:
- Substantial variation exists in calculated IBW among common methods, particularly in adolescents.
- Discrepancies in IBW can lead to significant differences in PARDS management.
- The McLaren method is recommended for calculating IBW in children with PARDS pending validation of a gold standard method.
Objectives:
No gold standard for ideal body weight determination in children exists. We aimed to compare four methods of ideal body weight calculation and determine level of agreement between methods and impact of measurement variance on tidal volumes prescribed in mechanically ventilated pediatric acute respiratory distress syndrome.
Design:
Post hoc analysis of four multicenter pediatric acute respiratory distress syndrome studies.
Setting:
Twenty-six academic PICUs.
Patients:
Five hundred eighty-nine patients.
Interventions:
None.
Measurements And Main Results:
Ideal body weight was calculated by four common methods: National Center for Health Statistics, McLaren, Moore, and body mass index, and compared in three ways: 1) determine the proportion of the cohort for which each method could successfully calculate ideal body weight; 2) compare the level of agreement between the ideal body weight methods by Bland-Altman analysis; and 3) evaluate the difference in tidal volume when 6 mL/kg ideal body weight was prescribed. We a priori defined the better method to be one that could calculate ideal body weight in most subjects, had good agreement with other methods, and led to a lower tidal volume. Only 55% could have ideal body weight measured by all four methods. National Center for Health Statistics, McLaren, and Moore methods could calculate ideal body weight in greater than or equal to 90%, whereas body mass index method was successful in only 61% because of no body mass index validation in less than 2-year-olds. In comparing each method to the others, there was great variance, particularly in greater than or equal to 10-year-olds. This variance was greatest between Moore and body mass index methods with greater than or equal to 10 kg difference in ideal body weight in some subjects. The McLaren method had the best agreement with all other methods, and yielded similar prescribed tidal volume in 2- to 10-year-olds and lower tidal volume in greater than or equal to 10 years old.
Conclusions:
There is substantial variation in calculated ideal body weight among four commonly used methods, particularly in adolescents. Since varying ideal body weight may lead to discrepancies in pediatric acute respiratory distress syndrome care, a standard approach to ideal body weight measurement is needed. We recommend the McLaren method to calculate ideal body weight in children with pediatric acute respiratory distress syndrome until a gold standard method is validated.
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