Editorials

Managing acute anaphylaxis

New guidelines emphasise importance of intramuscular adrenaline 

Acute anaphylaxis is all too often poorly recognised and treated. Reasons for this include the wide (and sometimes surprisingly subtle) clinical manifestations; the rarity of presentation to any individual medical practitioner; and confusion arising from conflicting advice about the role, route, and dose of adrenaline (epinephrine). Adrenaline may not be given at all, even when it is clearly indicated. Although reliable epidemiological data on the incidence of acute anaphylaxis are lacking, emergency departments and emergency specialists have the biggest collective expertise and experience in its management. Against this background the new guidelines for the emergency treatment of acute anaphylactic reactions from the United Kingdom Resuscitation Council, published this month,¹ are most welcome.

The guidelines provide clear guidance for first responders in general practice or emergency departments. Although they are not intended to replace specific guidelines developed for defined subgroups of patients receiving treatment with anaesthetic agents, contrast materials, or immunotherapy (desensitisation), they may well become popular among clinicians dealing with these patients.

The team that drew up the guidelines represented all the relevant clinical disciplines; this is important because, as the team points out, there is little evidence with which to provide an evidence base, so the wealth of clinical experience that underlies the team's consensus view demands respect. Their approach is pragmatic and they are wise to delete the distinction between anaphylactic and anaphylactoid reactions. This causes confusion and may be another factor leading to inadequate treatment. The guidelines detail the protean clinical features of acute anaphylaxis and the variation in speed of onset. There is a timely reminder of the often forgotten difficulties that may occur in patients taking  blockers: these drugs may increase the severity of an anaphylactic reaction and antagonise the response to adrenaline. Reliance on a good history and examination is confirmed. Emphasising all these points should lower the threshold for diagnosis. There is also recognition that patients experiencing anaphylaxis may present with dominant symptoms of acute severe asthma or laryngeal oedema.

Investigations to determine the nature of the reaction are irrelevant to acute treatment but can be started within the first hour. This is important for long term management and retrospective diagnosis and helps the specialist clinician.

Adrenaline is given its due importance. It is good to see that the subcutaneous route of administration is ceremoniously laid to rest. Let's hope we do not see it again. The safety of the intramuscular route is clearly stated; such encouragement of the use of this route may, on its own, lead to an increased use of this first line drug. The recommendation to repeat the drug within five minutes if there is no improvement or if the patient's condition deteriorates is not based on any evidence but is purely empirical. In view of the safety of the intramuscular route this seems sound advice. The role of the intravenous route is probably one of the more hotly debated topics in the literature and the courts. The consensus from the UK Resuscitation Council is that with an appropriate strength of solution (1/10 000 or 1/100 000, and "never 1/1000") it is an acceptable route for patients with profound shock that is immediately life threatening, although some users of this guideline would probably feel happier with more precise instructions than "should be given as slowly as seems reasonable." In light of the confident statements elsewhere it seems inconsistent that the guidelines are not more dogmatic here. We agree, however, that patients receiving intravenous adrenaline should undergo electrocardiographic monitoring and that the drug should be given by someone appropriately experienced.

The paediatric dosages recommended are based on grouping children into one of three age ranges rather than on an individual mg/kg basis, which is contrary to the teaching of the advanced paediatric life support course.² However, when treating an anaphylactic emergency many first responders will probably prefer to give standardised doses rather than to experience the additional stress of estimating or calculating the weight of a child.

There is no mention of the use of nebulised adrenaline for treating stridor in adults or children, although it is covered in the advanced paediatric life support course, and some clinicians use it in adults. Although the lack of mention is surprising, it does reflect the lack of good evidence for either using or withholding nebulised adrenaline, and also allows the responder to concentrate on giving parenteral adrenaline.

Another practical issue for doctors who rarely see acute anaphylaxis is a failure to give enough intravenous fluid. This is rightly addressed. The current crystalloid-colloid debate is acknowledged, with a suggested preference for crystalloids.

The reference in the guidelines to patient self-administration devices is of particular importance to general practitioners who may find that using the patient's own syringes is more efficient than trying to open their bags and prepare an adrenaline injection. The Epipen device, for example, has been shown to give more consistent and rapid adrenaline absorption than that obtained with subcutaneous adrenaline.³ Finally, the guidelines give due recognition to the importance of prevention through reducing exposure to suspected allergens. Preventive measures include, for example, the removal of peanuts from in flight refreshment menus; rapid identification of sufferers from anaphylaxis, who should wear appropriate information bracelets; and their assessment at a specialist allergy clinic.

These guidelines are welcome. They offer sound and pragmatic advice that will enable doctors to prescribe adrenaline and intravenous fluids with more confidence. We are sure that the guidelines will soon be seen adorning the walls of emergency departments, general practitioners' surgeries, and outpatient clinics, just as cardiac resuscitation guidelines now do.

Geoff Hughes, Clinical director. 

Emergency Services, Wellington Hospital, Wellington, New Zealand (wemgh{at}mash.wnhealth.co.nz )

Penny Fitzharris, Clinical immunologist and allergist. 

Department of Medicine, Wellington School of Medicine, Wellington, New Zealand (pfitzharris{at}wnmeds.ac.nz)