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

MARK DAVID LUSCOMBE ^1* and BEN DAVID OWENS ²

¹ Sheffield Teaching Hospitals NHS Trust, United Kingdom
² Queens Medical Centre, Nottingham, United Kingdom

^* To whom correspondence should be addressed. E-mail: paruabay{at}btinternet.com.

Accepted 14 December 2006

Abstract

Objectives: To gather data on ages and weights of paediatric patients aged between 1 and 10 years old, and to compare this 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: 17244 children aged 1 to 10 years, attending the ED between June-December 2005.

Main Outcome Measures: Weight difference between the measured weight and the expected weight, the latter given by Weight=2(Age+4).

Results: Seriously ill children’s weights 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% CI = 18.42% to 19.18%). Using linear regression and analysis of each individual age group, ten new formulae were tested. Of these formulae, "Weight (kg) = 3(Age)+7" proved 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. It is a simple, safe estimate of the weight of today’s child. Notes: 95%CI = 95% Confidence Interval.

Keywords: child, estimation, formula, resuscitation, weight

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