Elsevier

Resuscitation

Volume 81, Issue 9, September 2010, Pages 1105-1110
Resuscitation

Clinical paper
Mid-arm circumference can be used to estimate children's weights

https://doi.org/10.1016/j.resuscitation.2010.05.015Get rights and content

Abstract

Introduction

Accurate measurement of children's weight is rarely possible in paediatric resuscitation, and rapid estimates are made to ensure appropriate drug and fluid doses and equipment selection. Weight is commonly estimated from formulae based on children's age, or from their height using the Broselow tape. Foot-length and mid-arm circumference have also been suggested as the basis of weight-estimation formulae.

Objectives

To determine which of age, height, foot-length or mid-arm circumference had the strongest relationship with weight in healthy children, to derive a simple weight-estimation formula from the strongest correlate, and to compare its performance with existing weight-estimation tools.

Methods

This was a population-based prospective observational study of Hong Kong Chinese children aged 1–11 years old last birthday. Weight was measured to the nearest 0.2 kg; height, foot-length and mid-arm circumference to the nearest 0.1 cm. Multiple regression analysis was used to determine the strongest independent relationships with weight, and linear regression analysis derived a weight-estimation formula. Accuracy and precision of this formula were compared with standard age-based and height-based weight-estimation methods.

Results

Mid-arm circumference had the strongest relationship with weight, and this relationship grew stronger with age. The formula, weight [kg] = (mid-arm circumference [cm]  10) × 3, was at least as accurate and precise as the Broselow method and outperformed the age-based rule in school-age children, but was inadequate in pre-school children.

Conclusion

This weight-estimation formula based on mid-arm circumference is reliable for use in school-age children, and an arm-tape could be considered as an alternative to the Broselow tape in this population.

Introduction

In paediatric resuscitation, it is necessary to know the child's weight in order to provide appropriate drug and fluid doses, equipment selection and ventilator settings. Because measurement of weight itself is rarely possible in time-critical situations, and because there is often no one available who knows the child's weight, rapid and accurate methods of estimation need to be applied. Most commonly, weight can be estimated from formulae based on the child's age,1 or from the child's height using the Broselow tape.2

Other suggested methods include weight estimation according to foot-length, or mid-arm circumference (MAC).3, 4, 5 Neither is currently used in clinical practice for weight estimation in paediatric resuscitation. However, a formula including MAC and knee height has recently been validated in geriatric patients in the emergency department.6 MAC has also been used for many years in the assessment of malnutrition in the developing world.7

One of the most widely used age-based estimation method is that recommended in the UK-based Advanced Paediatric Life Support course1: weight in kg = 2 × (age in years + 4). It has been criticised for under-estimating children's weight, and new formulae have been derived.8, 9 The Broselow tape has consistently been found to outperform age-based formulae in estimating weight,8, 10, 11 but both the Broselow tape and age-based weight estimation methods are less precise in older and heavier children.2, 8, 10, 12, 13 Systematic underestimation of childhood weight is likely to be due to the increasing actual weights, especially of older, Western children. The US National Health and Nutrition Examination survey has demonstrated a steady increase in childhood obesity: data from 1999 to 2002 found that 16% of 6–19 year olds, and 10.2% of 2–5 year olds, were overweight (≥95th centile body mass index).14 In 6–18 year olds in Hong Kong, the proportion increased from 7.1% to 10.1% between 1993 and 2006.15

It is not known whether a weight-estimation method based on foot-length or MAC might be more appropriate than either the Broselow tape or age-based methods, especially in older children.

The objectives of this study were to determine which of age, height, foot-length or MAC had the strongest relationship with weight in healthy children, to derive a simple weight-estimation formula from the strongest correlate, and to compare its performance with existing weight-estimation tools.

Section snippets

Methods

This was a population-based observational study, part of the prospective “Healthy Children's Vital Signs and USCOM study”, which also included physiological and ultrasound cardiac output monitor (USCOM) measurements. It was conducted in primary schools and kindergartens in Hong Kong, and recruited healthy Chinese children aged 1–11 years on their last birthday.

Head teachers of all relevant institutions in the Shatin area of Hong Kong were asked for permission to have their schools participate

Results

1391 Chinese subjects aged 1–11 years on their last birthday were recruited from 14 schools and kindergartens. In the six institutions which recorded how many consent letters were distributed, 48% of invited parents consented. The time constraints of school timetables prevented us from obtaining all four anthropometric measurements in 21 children, who were excluded from further analysis. 1370 (98.5% of the eligible sample) were therefore included, of whom 55% were boys. There were 448 children

Discussion

We have shown that MAC is the strongest correlate with children's weight, in all age-groups, and that this relationship strengthens with age. Height, foot-length and age are also correlated with weight, but this relationship weakens with age, and only height remains an important correlate in older children, alongside MAC. We have derived a weight-estimation formula based on mid-arm circumference: weight = (MAC  10) × 3. This rule out-performs the Broselow tape and the APLS age-based formula in older

Conclusion

Weight correlates more strongly with mid-arm circumference in children, than with age, height or foot-length. We have derived a weight-estimation formula based on mid-arm circumference: weight = (MAC  10) × 3. This rule out-performs the Broselow tape and the APLS age-based formula in older children, but is less suitable in children under 6 years old. A colour-coded arm-tape could be developed for rapid assessment of paediatric weight in the resuscitation room for use in older children.

Conflict of interest statement

None of the authors has any competing interests to declare.

Funding

We received a Direct Grant, ref. 4450252, of HK$72,000 (approximately US$10,000) from the Chinese University of Hong Kong to conduct the “Healthy Children's Vital Signs and USCOM Study”. We also received a grant of HK$100,000 (approximately US13,000$) from the Hong Kong College of Emergency Medicine.

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  • Cited by (0)

    A Spanish translated version of the abstract of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2010.05.015.

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