Not all Allergies are Anaphylaxis!
Anaphylaxis is defined as:
- Severe life-threatening systemic hypersensitivity reaction
- Where BOTH of the following criteria are met:
- Sudden onset & rapid progression
- Life-threatening compromise of ONE or MORE of: Airway/Breathing/Circulation
- Skin/Mucosal changes (flushing, urticaria, angioedema) often occur but are absent/subtle in 20% of cases.
- Gastro-intestinal symptoms (vomiting, diarrhoea, abdominal pain) can be associated anaphylaxis.
Note: Skin/mucosal or GIT signs WITHOUT Airway/Breathing/Circulatory compromise DO NOT constitute anaphylaxis
Note: The recommendation to “lie patients flat”, may not be tolerated esp. if if the patient presents with airway or breathing compromise, and they should be allowed to sit in a comfortable position.
Look for precipitants and remove if possible.
Common precipitants include:
- Idiopathic in up to 20%
Rapidity of onset from stimulus varies according to the stimulus type. As you would suspect injection/sting has a faster onset time compared to ingestion, however, there is significant overlap.
We should send mast cell tryptase, in suspected anaphylaxis at the following time points
- As soon as possible after emergency treatment has started
- Within 1–2 hours (but no later than 4 hours) from the onset of symptoms.
However, if the patient presents late we may only get sample 2
Observation (for Biphasic reaction):
The data on biphasic reactions is poor, and highly varied. Studies quote rates between 1-20% and onset times from 1hr – 72hrs. Biphasic reactions are thought less likely among people with food-induced anaphylaxis, but those presenting with hypotension or idiopathic anaphylaxis may be at increased risk.
NICE note the following:
- 60% of biphasic reactions will occur within 8hrs of initial reaction.
- Patients should be observed in hospital for 6-12hrs minimum.
Resus council suggest prolonged (24hr) observation in these groups:
- Severe reactions with slow onset caused by idiopathic anaphylaxis.
- Reactions in individuals with severe asthma or with a severe asthmatic component.
- Reactions with the possibility of continuing absorption of allergen.
- Patients with a previous history of biphasic reactions.
- Patients presenting in the evening or at night, or those who may not be able to respond to any deterioration.
- Patients in areas where access to emergency care is difficult.
If the patient is Discharging/Self-discharges from ED:
We need to ensure that patient is aware of the possibility of a biphasic reactions, and document safety netting given.
- Use one adrenaline auto-injector and then call 999, ask for an ambulance, and state ‘anaphylaxis’, even if symptoms are improving.
- Lie flat with the legs raised in order to maintain blood flow. If the person has breathing difficulties, they should sit up to make breathing easier.
- Use the second auto-injector if they don’t start to feel better 5 to 15 minutes after the first injection.
Prescribing Adrenaline Injectors:
This will typically happen from the ward after an observation period. NICE recommend that patients with a documented anaphylaxis should receive the following:
- a demonstration of the correct use of the adrenaline injector and when to use it
- a prescription for 2 adrenaline injectors, with advice to carry the injectors with them at all times