Monitoring
Biphasic reactions or symptom recurrence may occur after resolution of the initial presentation. In patients presenting with severe anaphylaxis and/or those who need >1 dose of epinephrine (adrenaline), prolonged observation might be necessary, following complete resolution of all signs and symptoms, to monitor for a potential biphasic reaction. The optimal duration of observation has not been established. One meta-analysis determined that the negative predictive value for a biphasic reaction was 95% at 1 hour which increased to 97.3% after a 6 hour observation.[74] In patients with a higher risk of biphasic reaction or risk factors for anaphylaxis fatality (e.g., cardiovascular comorbidity, lack of access to epinephrine, lack of access to emergency medical services, limited ability to self-manage), extended observation of up to 6 hours or longer might be appropriate.[28][70][71]
Patients who respond well to treatment and whose symptoms do not return within the observation period can be discharged home with close follow-up and instructions to return if symptoms reappear. The patient’s ability to recognize symptoms and to self-administer epinephrine should inform this decision.[75] Patients should notify their primary care physician about their condition and obtain prompt follow-up with an allergist.
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