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Variability in Pediatric Ideal Body Weight Calculation: Implications for Lung-Protective Mechanical Ventilation Strategies in Pediatric Acute Respiratory Distress Syndrome*

Ward, Shan L. MD, MAS1; Quinn, Carson M. BS2; Steurer, Martina A. MD, MAS1; Liu, Kathleen D. MD, PhD3; Flori, Heidi R. MD4; Matthay, Michael A. MD3,5,6

Pediatric Critical Care Medicine: December 2018 - Volume 19 - Issue 12 - p e643-e652
doi: 10.1097/PCC.0000000000001740
Online Clinical Investigations

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.

1Division of Critical Care, Department of Pediatrics, UCSF Benioff. Children’s Hospital San Francisco, San Francisco, CA.

2School of Medicine, UCSF, San Francisco, CA.

3Department of Medicine, UCSF Medical Center, San Francisco, CA.

4Division of Pediatric Critical Care Medicine, C.S. Mott Children’s Hospital, Ann Arbor, MI.

5Department of Anesthesia, UCSF Medical Center, San Francisco, CA.

6Cardiovascular Research Institute, UCSF Medical Center, San Francisco, CA.

*See also p. 1179.

Drs. Ward, Steurer, Liu, Flori, and Matthay conceived of and designed the study. Dr. Ward, Mr. Quinn, and Dr. Flori participated in data acquisition. Drs. Ward, Steurer, and Flori conducted the data analysis. All authors contributed to the interpretation of the analysis results. Dr. Ward prepared the first draft of the article, and all authors revised the draft critically. All authors have approved the final article for publication.

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Supported, in part, by National Institutes of Health grants 5T32HD049303-08 (to Dr. Ward), K12HD047349 (to Dr. Ward), National Heart, Lung, and Blood Institute HL51856 (to Dr. Matthay), and K24 DK113381 (to Dr. Liu).

Dr. Ward’s institution received funding from the National Institutes of Health (NIH)/National Institute for Child Health and Development. Drs. Ward, Flori, and Matthay received support for article research from the NIH. Dr. Liu’s institution received funding from the NIH/National Heart, Lung, and Blood Institute (NHLBI) and the National Institute of Diabetes and Digestive and Kidney Disease, and she received funding from Achaogen, Durect (consulting), Z S Pharma (Advisory Board participant), Theravance (consulting), Quark (consulting), Potrero Med (consulting), Amgen (stockholder), the American Society of Nephrology (funding for travel), the National Kidney Foundation (Advances in Chronic Kidney Disease Associate Editor), and National Policy Forum on Critical Care and Acute Renal Failure (funding for travel). Dr. Flori’s institution received funding from the NIH, and she received funding from Genentech, expert testimony reimbursement from a private law firm, and honoraria for educational lectures at referring hospital. Dr. Matthay’s institution received funding from the NIH/NHLBI/Food and Drug Administration, the Department of Defense, Bayer Pharmaceuticals, and GlaxoSmithKline, and he received funding from consulting for CS Berhling, Boerhinger-Ingelheim, Cerus Therapeutics, Quark Pharmaceuticals, and Thesan Pharmaceuticals. The remaining authors have disclosed that they do not have any potential conflicts of interest.

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