S. Ismail, S. Setty

Royal Free NHS Trust, London, UK

Introducing an innovative Paediatric Drug Dose Calculator to calculate anaesthetic drug doses and equipment sizes for both normal-weight and obese children.


Administering paediatric anaesthesia is challenging due to variations in equipment sizes and drug doses among children. Calculating these adjustments is time-consuming and error-prone, especially in emergencies where doses may not be written down. Additionally, the rising prevalence of obesity further complicates dosing, as certain medications require adjustments using adjusted or ideal body weight.


This project aimed to design and implement an online paediatric drug dose calculator to:

  1. Increase speed and ease in paediatric anaesthetic drug calculations.
  2. Improve team communication of these doses.
  3. Reduce drug prescribing errors, particularly in obesity.


The development process followed a Plan, Do, Study, Act (PDSA) cycle, beginning with a survey to evaluate current dosing methods and staff confidence in paediatric anaesthesia. Additionally, research was conducted into existing paediatric calculators and best practice guidelines.

An online paediatric calculator was created and presented in a department Audit meeting and received a positive response. Following this, the calculator was rolled out on 06/12/23 to be accessible to staff via QR codes or weblinks for testing.

Key features of the calculator included WETFLAG, Tube and LMA size calculations, an option to use Actual, Calculated or Ideal Body weight, adherence to SOBA guidelines for obesity, safety caps for drug doses, use of anaesthetic colour layout and printable sheets for convenience.

In January 2024, the calculator was re-audited, and a follow-up survey was undertaken to assess the effectiveness of the intervention.


Between 06/12/23 and 15/01/24, the calculator was accessed 56 times with 18% of uses occurring out-of-hours (8pm-8am). The calculator was utilized for ages between 3 weeks to 16 years.

The baseline survey had 40 responses (50% from the consultant level), whilst the re-audit survey had 30 responses (43% from the consultant level).


The follow-up survey showed overwhelmingly positive feedback, with several staff members reporting it was very easy to use. There were no calculation errors reported, and 60% of staff members said it would make them more likely to write down paediatric drug doses.

Comparing the surveys, staff reported it was quicker for them to calculate drug doses with a 6% reduction in the reported calculation times. Additionally, confidence in calculating paediatric drug doses for ‘Under 1 year’ and for ‘5-10 year olds’ increased, with 4% and 5% more staff members reporting they felt quite /extremely confident respectively.


Overall, this intervention has positively changed practice, particularly by reducing drug calculation times and increasing the likelihood of drug doses being written down.

To build on from this positive feedback, ongoing collaboration is being conducted with key stakeholders to develop a validated app/website available for clinical use.


1- Society for Obesity & Bariatric Anaesthesia. Anaesthesia for Children living with Obesity - Single Sheet Guideline. Available from: https://www.sobauk.co.uk/guidelines-1 (accessed 26 Jan 2024).

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