Calculation skills for nurses: paediatrics

Abstract

T is the second article in this series featuring calculation skills for nurse prescribers. The topic for this second instalment is paediatrics. In 2004, the Chief Pharmaceutical Officer listed prescribing for children as a common source of calculation errors (Smith, 2004). Prescribing for children often involves calculation of doses according to body weight. Children may additionally fall into other risk categories. For example, they may require highrisk and/or high-alert medicines to be prescribed, notably in secondary care, but also in primary care settings (Best Practice Journal (BPJ), 2010). Factors contributing to medication errors in children include (BPJ, 2010; WHO, 2010a): n Individual dose calculation according to age, weight and clinical condition, often leading to multiple opportunities for error n Small-dose volumes, requiring accurate measurement n Monitoring difficulties associated with lack of or underdeveloped communication skills, particularly in younger children n Inaccurate recording of the child’s weight, both initially and as it changes over time n Lack of evidence-based dosing information due to a lack of supporting clinical trials in children n Immature body systems for metabolizing and/or excreting drugs in the very young. The World Health Organization’s (WHO) evidence-based model formulary for children (WHO, 2010b) provides dosing advice on 240 common drugs for children up to 12 years. However, the guidance is global and not UK-specific. The recommended reference source in the UK is the British National Formulary (BNF) for Children (Joint Formulary Committee, 2010). In the example given below, however, the dosage advice in the BNF for Children (Joint Formulary Committee, 2010) and the WHO formulary for children (WHO, 2010c) is very similar. Prescribers must be vigilant in checking the suggested dosage statements. They must also consider whether the calculated dose makes sense. In general, the cut-off point for dose calculation according to body weight is 40 kg (BPJ, 2010). After this, the adult dosage is usually indicated. For larger or older children, the prescriber should confirm that the calculated dose does not exceed the recommended adult dose. The nature of the dosage statement may also vary. For example, the following dose statements in effect mean the same thing: 1 mg/kg four times a day 4 mg/kg daily in four divided doses.