Anaphylaxis is a severe life threatening reaction involving the respiratory and cardiovascular systems, with or without cutaneous skin reactions (approximately 20% of reactions occur without skin/mucosal features) and gastrointestinal symptoms. Most anaphylactic reactions occur within half an hour of allergen exposure, but may take up to two hours to develop and as a result can often make diagnosing anaphylaxis difficult.
Anaphylaxis may be caused by a number of external stimuli, the most common being food, insect venom and medications. Medications account for 57% of anaphylaxis deaths, and the most common causative medications are antibiotics, non-steroidal anti-inflammatories, opiates and anaesthetics.
The clinical features of anaphylaxis include:
- Any acute onset of hypotension or bronchospasm or upper airway obstruction, with or without typical skin features (or any acute onset illness with typical skin features) such as urticarial rash, erythema, flushing and/or angioedema, and
- Respiratory and/or cardiovascular involvement and/or persistent gastrointestinal symptoms.
It is important that anaphylactic reactions or suspected anaphylaxis are managed quickly and effectively. The recommended management of anaphylaxis is:
- Remove the allergen, call for assistance and lay the patient flat. Allow them to sit if they are having difficulty breathing – DO NOT allow them to stand or walk.
- Intramuscular adrenaline is the first line immediate treatment – dosing will vary depending on the setting and the available formulations (Figure 1).
- Repeat doses of adrenaline may be required due to its short duration of action (about 15 minutes). If necessary, repeat doses may be administered every five minutes.
- Call an ambulance if required (Note: once adrenaline has been administered the patient must be monitored for four hours after the last dose administered).
Figure 1. Dosing guidelines for adrenaline.
1:1000 (1mg in 1mL)
Supportive management should also be undertaken, including;
- Monitor blood pressure, pulse rate, respiratory rate and pulse oximetry (if available)
- Use high flow oxygen and airway support if required
- If hypotensive, use intravenous 0.9% normal saline and a bolus dose of glucagon 1-2mg for adults.
In addition to these measures, it may be necessary to further treat specific symptoms. If airway obstruction, consider the use of nebulised adrenaline 5mL of 1:1000 ampoules. If persistent wheeze, administer salbutamol preferably 5mg/2.5mL via nebuliser, or 8-12 puffs of 100mcg metered dose inhaler, using a spacer.
Following a severe reaction, it may also be necessary to provide the patient a short course of oral corticosteroids such as prednisolone dosed at 1mg/kg (up to a maximum dose of 50mg per day) for two days.
It is important to note that antihistamines have no role in the treatment of cardiovascular or respiratory symptoms relating to anaphylaxis, and injectable promethazine should not be used in anaphylaxis as it can worsen hypotension and cause muscle necrosis.
In 2011 the Australian Prescriber published an “Anaphylaxis: Emergency Management for Health Professionals” wall chart for use in healthcare settings, detailing the recommendations for anaphylaxis emergency management. It can be found at www.australianprescriber.com/magazine/34/4/artid/1210.
- Anaphylaxis: Emergency management for health professionals [Wallchart]. Aust Prescr 2011; 34: 124.
- Australasian society of clinical immunology and allergy inc (ASCIA). ASCIA acute management of anaphylaxis guidelines. Balgowlah: ASCIA; 2011.
- Kirkbright SJ, Brown SGA. Anaphylaxis: Recognition and management. Aust Fam Physician 2012; 41(6): 366-70.
- Laemmle-Ruff I, O’Hehir R, Ackland M. Anaphylaxis: Identification, management and prevention. Aust Fam Physician 2013; 42 (1): 38-42.
- Management of Anaphylaxis. In: Rossi S, editor. Australian Medicines Handbook 2013 [online]. Adelaide: Australian Medicines Handbook Pty Lty; 2013 July.