Anaphylaxis
Anaphylaxis may be defined as a severe, life-threatening, generalised or systemic hypersensitivity reaction.
Anaphylaxis is one of the few times when you would not have time to look up the dose of a medication. The Resuscitation Council guidelines on anaphylaxis have recently been updated. Adrenaline is by far the most important drug in anaphylaxis and should be given as soon as possible. The recommended doses for adrenaline, hydrocortisone and chlorphenamine are as follows:
Adrenaline can be repeated every 5 minutes if necessary. The best site for IM injection is the anterolateral aspect of the middle third of the thigh.
Common identified causes of anaphylaxis
Sometimes it can be difficult to establish whether a patient had a true episode of anaphylaxis. Serum tryptase levels are sometimes taken in such patients as they remain elevated for up to 12 hours following an acute episode of anaphylaxis.
Key Points
- Mortality from anaphylaxis in the UK is <1%.
- Management is based on ABCDE approach.
- Primary treatment is IM adrenaline
- Anaphylaxis is IgE mediation of the inflammatory response.
- All those who have had an anaphylactic episode should see an anaphylaxis specialist as per resus council guidelines.
Anaphylaxis is one of the few times when you would not have time to look up the dose of a medication. The Resuscitation Council guidelines on anaphylaxis have recently been updated. Adrenaline is by far the most important drug in anaphylaxis and should be given as soon as possible. The recommended doses for adrenaline, hydrocortisone and chlorphenamine are as follows:
| Adrenaline | Hydrocortisone | Chlorphenamine | |
|---|---|---|---|
| < 6 months | 150 micrograms (0.15ml 1 in 1,000) | 25 mg | 250 micrograms/kg |
| 6 months - 6 years | 150 micrograms (0.15ml 1 in 1,000) | 50 mg | 2.5 mg |
| 6-12 years | 300 micrograms (0.3ml 1 in 1,000) | 100 mg | 5 mg |
| Adult and child > 12 years | 500 micrograms (0.5ml 1 in 1,000) | 200 mg | 10 mg |
Adrenaline can be repeated every 5 minutes if necessary. The best site for IM injection is the anterolateral aspect of the middle third of the thigh.
Common identified causes of anaphylaxis
- food (e.g. Nuts) - the most common cause in children
- drugs
- venom (e.g. Wasp sting)
Sometimes it can be difficult to establish whether a patient had a true episode of anaphylaxis. Serum tryptase levels are sometimes taken in such patients as they remain elevated for up to 12 hours following an acute episode of anaphylaxis.