Immediately on diagnosis of anaphylaxis, administer adrenaline via intramuscular (IM) injection into the mid-anterolateral thigh using a needle of appropriate length. Subcutaneous or inhaled routes for adrenaline are not recommended as they are less effective. Pregnant women experiencing anaphylaxis require the same dose of IM adrenaline as other patients. The recommended doses for IM adrenaline are indicated in Table 3.
Delayed administration of adrenaline is a risk factor for fatal anaphylaxis. If anaphylaxis is suspected in the presence of an allergy or anaphylaxis history, or following exposure to a potential allergen, it is safer to administer adrenaline early than to wait for progression, which may be hard to reverse. There are no absolute contraindications to adrenaline administration in anaphylaxis.
In most situations, IM adrenaline is preferred and is safer than the intravenous (IV) route. Adverse events have been reported in adult patients who received overdoses of IV adrenaline, but these are rare with IM adrenaline.
An IV adrenaline infusion should only be administered when clinically appropriate, and:
- By clinicians trained in the use of IV adrenaline
- In a critical care setting where there is appropriate haemodynamic monitoring available.
Repeated IM adrenaline injections can be given at five-minute intervals if the patient’s symptoms are not improving. Escalate care as per organisational protocols if the patient’s condition is not improving after two to three doses of adrenaline.
Do not administer corticosteroids or antihistamines first-line, as they are not effective in treating anaphylaxis. Corticosteroids have a delayed effect of 4–6 hours and are adjuncts in the management of anaphylaxis – they do not replace adrenaline. Antihistamines are only helpful for relieving associated urticaria (hives), angioedema and itch. Do not give promethazine or other sedating antihistamines, as the sedating effect can mask deterioration or a biphasic reaction. Injecting promethazine can worsen hypotension and cause muscle necrosis.
Consider the implications of the treatment provided in the healthcare facility and what this communicates regarding adrenaline use. Avoiding adrenaline use in the case of a severe allergic reaction, or preferentially using corticosteroids, bronchodilators or antihistamines, may inadvertently give a message to patients that they should delay using their adrenaline injector, thus increasing potential risk in a subsequent anaphylaxis.
Include a ‘when required’ (prn) order for IM adrenaline on an admitted patient’s medication chart if they have a known allergy and have been prescribed an adrenaline injector. This can expedite the administration of IM adrenaline if the patient experiences anaphylaxis while in care.
