One of the most important variables in paediatrics is development, and one important measure of physical development is weight. This is used for all sorts of things, including drug doses, fluid calculations and body surface area estimation. Normally of course we can weigh children, so this should be pretty accurate.
Unfortunately, sometimes we can’t do this, most notably in emergency situations; and in such cases it is necessary to estimate the child’s weight. While this is never going to be as accurate as weighing the child, a good estimate is the best that can often be achieved. However, this obviously requires two things:
- A formula for estimating weight
- That the person using it can remember it and use it correctly.
A number of methods for estimating weight exist, however a recent letter published in Archives of Disease in Childhood describing a survey among 25 paediatric trainees suggest that this may be a cause of some confusion. The authors start by reviewing the current Advanced Paediatric Life Support (APLS) Guidelines, which contain three methods of estimating weight:
· Infants from 1-12 months (0.5 x age in months +4)
· Children aged 1-5 years (2 x age in years +8)
· Children aged 6-12 years (3 x age in years +7)
These replace the previous Guidelines which had one formula for children aged 1-10 years, and which still used in some Guidelines.
The study found that only 2 of the participants (8%) were able to correctly apply the new formulae to examples that they were given, and that around half used the old formula. The extent to which this matters is debatable, but clearly someone thought it was worth changing the guidance on this, and this is what is now taught, so one would expect that paediatric trainees at least would know them.
The lesson from this is that Guidelines should always be as simple as possible if we expect people to remember them. For parents, it might be worth knowing roughly how much your child weighs!