Monitoring

Biphasic reactions or symptom recurrence may occur after resolution of the initial presentation. There is no reliable predictor for biphasic or protracted anaphylaxis; differing observation periods, or the effect of these on relevant patient outcomes, have not been studied.[52][149]

Follow your local protocol for observing patients following a suspected anaphylactic reaction. Observation should occur in a clinical area with facilities for treating life-threatening airway, breathing, and circulation problems.[32]

Based on the available evidence, the Resuscitation Council (UK) recommends observation:[32]

  • For at least 2 hours after resolution of symptoms (consider fast-track discharge) if there is:

    • A good response (within 5-10 minutes) to a single dose of adrenaline given within 30 minutes of onset of reaction

      and

    • Complete resolution of symptoms

      and

    • The patient has unused adrenaline autoinjectors and has been trained how to use them

      and

    • There is adequate supervision following discharge

  • For at least 6 hours after resolution of symptoms if 2 doses of intramuscular adrenaline were given or there was a previous biphasic reaction. 

    • Some patients may be discharged after 2 hours despite needing 2 doses of intramuscular adrenaline, for example, following a supervised allergy challenge in a specialist setting.

  • For at least 12 hours following resolution of symptoms for patients with:

    • Severe reaction requiring >2 doses of adrenaline

    • Severe asthma or reaction involved severe respiratory compromise

    • The possibility of continuing absorption of the allergen (e.g., slow-release medicines)

    • Presentation late at night

    • Possible inability to respond to deterioration

    • Difficulty accessing emergency care.

The National Institute for Health and Care Excellence in the UK recommends observing patients after suspected anaphylaxis for 6 to 12 hours from the onset of symptoms, depending on their response to emergency treatment.[52]

  • Consider a shorter observation period if the reaction was controlled promptly and easily.

  • Admit children younger than 16 years with suspected anaphylaxis to the paediatric service in hospital.

Refer patients to an age-appropriate specialist allergy service for accurate investigation, diagnosis, monitoring, ongoing management, patient education, and possible immunotherapy.[32][52][59]

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