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Weight estimation in resuscitation: is the current formula still valid?


Objectives: To gather data on the ages and weights of paediatric patients between 1 and 10 years of age, and to compare these data with the current weight estimation formula weight(kg) = 2(age+4). If a significant difference was found, the data would be used to derive a more accurate formula.

Design: Retrospective study using data collected from paediatric attendances at an emergency department (ED).

Setting: A large ED in a major UK city, treating both children and adults.

Patients: 17 244 children aged 1–10 years, attending the ED between June and December 2005.

Main outcome measures: Weight difference between the measured weight and the expected weight, the latter given by weight = 2(age+4).

Results: The weights of seriously ill children were recorded in only 41.5% of cases, necessitating a weight estimate in the remainder. The formula weight = 2(age+4) underestimated children’s weights by a mean of 18.8% (95% confidence interval (95% CI) 18.42% to 19.18%). Using linear regression and analysis of each individual age group, ten new formulas were tested. Of these formulas, weight(kg) = 3(age)+7 proved the most accurate with a mean underestimate of just 2.48% (95% CI 2.17% to 2.79%).

Conclusions: Weight estimation remains of paramount importance in paediatric resuscitation. This study shows that the current estimation formula provides a significant underestimate of children’s weights. When used to calculate drug and fluid dosages, this may lead to the under-resuscitation of a critically ill child. The formula weight(kg) = 3(age)+7 provided a safe and more accurate estimate of the weight of today’s child.

  • APLS, advanced paediatric life support
  • 95% CI, 95% confidence interval
  • ED, emergency department
  • EPLS, European paediatric life support
  • MAC, mid-arm circumference
  • PICU, paediatric intensive care unit
  • child
  • weight
  • estimation
  • formula
  • resuscitation

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  • Précis
    BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health
  • Atoms
    Howard Bauchner
    BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health