An aid to drug dosing safety in obese children: development of a new nomogram and comparison with existing methods for estimation of ideal body weight and lean body mass

Anaesthesia. 2015 Feb;70(2):176-82. doi: 10.1111/anae.12860. Epub 2014 Oct 7.


The risk of accidental over-dosing of obese children poses challenges to anaesthetists during dose calculations for drugs with serious side-effects, such as analgesics. For many drugs, dosing scalars such as ideal body weight and lean body mass are recommended instead of total body weight during weight-based dose calculations. However, the complex current methods of obtaining these dosing scalars are impractical in the peri-operative setting. Arbitrary dose adjustments and guesswork are, unfortunately, tempting solutions for the time-pressured anaesthetist. The study's aim was to develop and validate an accurate, convenient alternative. A nomogram was created and its performance compared with the standard calculation method by volunteers using measurements from 108 obese children. The nomogram was as accurate (bias 0.12 kg vs -0.41 kg, respectively, p = 0.4), faster (mean (SD) time taken 2.8 (1.0) min (vs 3.3 (0.9) min respectively, p = 0.003) and less likely to result in mistakes (significant errors 3% vs 19%, respectively, p = 0.001). We present a system that simplifies estimation of ideal body weight and lean body mass in obese children, providing foundations for safer drug dose calculation.

Publication types

  • Comparative Study
  • Validation Study

MeSH terms

  • Analgesics / administration & dosage
  • Analgesics / metabolism
  • Anesthetics / administration & dosage
  • Anesthetics / metabolism
  • Body Mass Index*
  • Body Weight
  • Child
  • Dose-Response Relationship, Drug
  • Drug Dosage Calculations*
  • Drug Overdose / prevention & control
  • Female
  • Humans
  • Ideal Body Weight*
  • Male
  • Nomograms*
  • Patient Safety / statistics & numerical data*
  • Pediatric Obesity / metabolism*
  • Reproducibility of Results
  • Time Factors


  • Analgesics
  • Anesthetics