Articles / Common GP emergencies: Anaphylaxis
Anaphylaxis is most commonly triggered by foods, drugs, insect bites and stings. Less commonly, it can be caused by latex, cold temperature or in 20% of cases, there may be no clear trigger at all. Symptoms usually commence within one to two hours of exposure. Biphasic reactions (delayed recurrence of symptoms) occur in 3-20% of cases of anaphylaxis and 90% of these occur within four hours of the initial reaction).
Clinical features
ASCIA defines anaphylaxis as:
Any acute onset of hypotension, bronchospasm or upper airway obstruction where anaphylaxis is considered possible, even in the absence of skin features OR
Any acute onset illness with typical skin features (urticaria, flushing or angioedema) PLUS symptoms from the respiratory (dyspnoea, wheeze, stridor), cardiovascular (chest pain, presyncope, diaphoresis) or gastro-intestinal systems (nausea, vomiting, abdominal pain).
Adrenaline dose chart (1:1000 ampoules containing 1mg adrenaline per 1 mL |
||
Age | Weight (kg) | Adrenaline volume 1:1000 |
<1 | 5-10 | 0.05-01 mL |
1-2 | 10 | 0.1 mL |
2-3 | 15 | 0.15 mL |
4-6 | 20 | 0.2 mL |
7-10 | 30 | 0.3 mL |
10-12 | 40 | 0.4 mL |
>12 and adult | >50 | 0.5 mL |
1. Call for help from staff and 000
2. Remove precipitant if known
3. Lay the patient flat – do not allow them to stand or walk
4. Give INTRAMUSCULAR ADRENALINE without delay into outer mid thigh
Adrenaline injector dose chart |
||
Age | Weight (kg) | Dose |
Children 1-5 years | 7.5kg – 20 kg | 0.15 mg (Anapen or EpiPen) |
Adults and children age >5 | Over 20 kg | 0.3 mg (Anapen or EpiPen) |
Adults and children age >12 | Over 50 kg | 0.3 mg (Anapen or EpiPen) or 0.5 mg (Anapen) |
Bronchospasm/wheeze
Note that bronchodilators don’t prevent or improve upper airway obstruction, hypotension or shock, and therefore should never be used first line treatment.
Upper airway obstruction (stridor)
Hypotension
Steroids
Antihistamines
Severe anaphylaxis and cardiac arrest
Patient resource: |
Allergy & Anaphylaxis Australia (www.allergyfacts.org.au) supports people to manage everyday life with anaphylaxis risk, with information on label reading, travel, starting school, school camp, workplace management and more. Their helpline is staffed by trained allergy educators on 1300 728 000. |
For more information
ASCIA Guidelines for Acute Management of Anaphylaxis
This content was reviewed by ASCIA in October 2023.
References
R., Dunn. et al. (2006) “Anaphylaxis,” in The emergency medicine manual. Tennyson, South Australia: Venom Publishing, pp. 401–404.
Acute management of anaphylaxis – allergy.org.au. (n.d.). Retrieved March 1, 2023, from https://allergy.org.au/images/ASCIA_HP_Guidelines_Acute_Management_Anaphylaxis_2023.pdf
Anaphylaxis: Emergency management for health professionals. (2018, April 01). Retrieved March 1, 2023, from https://www.nps.org.au/australian-prescriber/articles/anaphylaxis-emergency-management-for-health-professionals
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