Weight-based N-acetylcysteine dosing chart to minimise the risk of calculation errors in prescribing and preparing N-acetylcysteine infusions for adults presenting with paracetamol overdose in the emergency department

Abstract

Management of paracetamol overdose (POD) is common in the emergency department (ED) and forms part of the clinical effectiveness audit programme of the British Association for Emergency Medicine. N-acetylcysteine (NAC) infusion regimens for the treatment of POD are complicated and prescribing and administration errors have been well documented. This study assessed the ability of doctors and nurses to calculate correct doses using manual calculation skills and a weightbased NAC dosing chart when prescribing and preparing NAC infusions. With manual calculations, errors were made by doctors and nurses in 26% of cases collectively. No errors were made using the dosing chart. The dosing chart ensured 100% accuracy in dose calculations, which may translate into improved patient safety.T reatment of paracetamol overdose (POD) with N-acetylcysteine (NAC) prevents hepatic failure. Suboptimal treatment may adversely affect patient outcome. NAC infusion regimens require complex calculations to be made by both prescribers and nurses preparing infusions. 1Errors with intravenous medicines requiring multiple step preparation or complex calculations have been highlighted.2 3 The use of dosing charts to prevent medication errors associated with complex calculations has been proposed by the Department of Health as a risk reduction strategy. 4 Typically, doses of NAC, diluent fluids and their volumes and durations of infusions are prescribed by doctors on intravenous infusion charts. In the UK, the preparation and administration of parenteral treatment is usually performed by trained nurses who calculate volumes of a 20% NAC solution (ParvolexH) required to prepare infusions based on doctors' prescriptions. When preparing NAC infusions, calculation errors have resulted in doses varying by more than 50% from the intended dose. 4 In 2005, there were 112 000 attendances to our emergency department (ED). Approximately 80 patients per month presented with a POD and 25% of these were treated with NAC. The infrequency with which NAC dose and volume calculations are performed in our department may increase the risk of medication errors. Most NAC prescribing for POD is initiated in EDs where pharmacists do not routinely check prescriptions or drug administration to ensure safe medicine use. Incorrect prescriptions for NAC infusions initiated in the ED have been identified and corrected by pharmacists when patients have been reviewed following admission to wards.The aim of this study was to compare the accuracy of doses and volumes calculated manually by ED staff when prescribing and preparing NAC infusion regimens with those derived from a weight-based NAC dosing chart. METHODSA weight-based NAC dosing chart (fig 1), based on the standard treatment regimen for POD in adults (http:// www.spib.axl.co.uk; http://emc.medicines.org.uk/emc/industry/ default.asp?page = displaydoc.asp&documentid = 1127), 5 was designed by pharmacists in conjunction with ED practitioners. Doctors and nurses of all grades involved in NAC prescribing and administrat...

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