It is estimated that one in 1,333 members of the English population has experienced a severe allergic reaction during their lives. Anaphylaxis affects the airway, breathing, circulation or a combination of the three.
For 20 people in the UK each year, it is fatal.2 Its fast onset and potentially life threatening consequences is such that the National Institute for Health and Clinical Excellence recommends all patients who present at accident and emergency with anaphylaxis symptoms should subsequently be prescribed an adrenaline auto-injector (AAI) as a “first aid” treatment before seeking emergency medical care.3
However, care should be taken by formularies and prescribers to select an AAI that is likely to be effective in use, based on current evidence and recommendations, rather than simply following the status quo.
Concerns about effective use of AAIs
Concerns have been raised regarding the performance capabilities of some AAIs, triggered by the death of a patient following an anaphylactic episode, despite the use of two devices.
It is particularly important for prescribers to be aware that the injection should be into the anterolateral (outside) mid thigh, with the needle tip within the muscle4 - a subcutaneous (beneath the skin) injection is unlikely to be effective. Yet research suggests 87 per cent of women have a skin to muscle depth (STMD) too great for the 15mm needle currently used in many AAIs to reach the muscle.5
Meanwhile, a study of paediatric allergy patients in Manchester found that 29 per cent of children weighing more than 30kg and 16 per cent of those under 30kg are likely to have a mid thigh STMD greater than the length of the needle in their current AAI.6
The Resuscitation Council recommends a 25mm needle for intramuscular injections, to increase the probability that the medication reaches the muscle.7
It also recommends that the standard dose of adrenaline for adults and adolescents over 12 years of age should be 500 micrograms.8 Yet most patients are still prescribed lower dose AAIs with shorter needle lengths, possibly putting them at greater risk of treatment being ineffective in speedily reversing the reaction.
Recent evidence also suggests that a more intuitive device design can significantly increase likelihood of correct usage.
While the numbers affected by anaphylaxis may be relatively small, the potential for fatalities means it is an important issue.
Prescribers should be empowered to select an AAI that administers the recommended adrenaline dose in an easy to use device that uses a needle long enough to ensure intramuscular delivery. By making this more informed choice, the device is likely to be effective and outcomes can be improved.
1 Sheikh A, et al. “Trends in national incidence, lifetime prevalence and adrenaline prescribing for anaphylaxis in England” J R Soc Med. 2008;101:139-43. Available at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2270246/pdf/139.pdf. Accessed July 2015.
2 Pumphrey RS (2000) “Lessons for management of anaphylaxis from a study of fatal reactions.” Clinical and Experimental Allergy 30(8): 1144-50.
3 National Institute for Health and Care Excellence (2011) “Anaphylaxis: assessment to confirm an anaphylactic episode and the decision to refer after emergency treatment for a suspected anaphylactic episode”. Available via https://www.nice.org.uk/guidance/cg134. Accessed July 2015.
4 Pumphrey R, et al. (2014) “Tissue distribution of dye marker following autoinjector use”, Poster abstract 367, European Academy of Allergy and Clinical Immunology (EAACI) Annual Congress
5 Johnstone J, et al. (2015) “Excess subcutaneous tissue may preclude intramuscular delivery when using adrenaline autoinjectors in patients with anaphylaxis”. Allergy 70(6):703-6.
6 Bewick DC, et al. (2013) “Anatomic and anthropometric determinants of intramuscular versus subcutaneous administration in children with epinephrine autoinjectors. J Allergy Clin Immunol Pract 1(6):692-4.
7 Resuscitation Council UK (2008, updated 2012) “Emergency treatment of anaphylactic reactions: guidelines for healthcare providers”. Available via https://www.resus.org.uk/anaphylaxis/emergency-treatment-of-anaphylactic-reactions/. Accessed July 2015.
9 Knibb R, Morton K (2014) “Preference for adrenaline auto-injector use in an emergency situation by non-allergic adults: A comparison of Jext, EpiPen, Emerade and Auvi-Q”, British Society for Allergy & Clinical Immunology (BSACI) Annual Meeting