When should a patient be admitted to the hospital after an anaphylactic reaction?

Hospital Admission Criteria After Anaphylactic Reaction

Patients with severe anaphylaxis or those requiring more than one dose of epinephrine should be admitted to the hospital for extended observation due to the risk of biphasic reactions. 1

Risk Stratification for Hospital Admission

High-Risk Patients (Require Admission)

• Patients with severe initial anaphylactic reaction 1
• Patients requiring >1 dose of epinephrine 1, 2
• Patients requiring fluid resuscitation 2
• Patients with wide pulse pressure 1
• Patients with cardiovascular comorbidities 1
• Patients with poorly controlled asthma 1
• Patients with unknown anaphylaxis trigger 1
• Children with drug-induced anaphylaxis 1
• Patients with poor access to emergency medical services 1
• Patients with poor self-management skills 1

Observation Duration Guidelines

• High-risk patients: Hospital admission with observation for at least 6-24 hours 1
• Moderate-risk patients: Extended observation in emergency department for 4-6 hours 1
• Low-risk patients: Observation for at least 1 hour after symptom resolution 1

Rationale for Extended Observation

Biphasic reactions occur in 1-20% of anaphylaxis cases and typically develop around 8 hours after the initial reaction, though they can occur up to 72 hours later 1, 3. The number needed to monitor with extended observation to detect one episode of biphasic anaphylaxis is:

• 13 patients (range 7-27) for those requiring multiple epinephrine doses 1
• 41 patients (range 18-195) for those with severe initial presentation 1

Research shows that patients who received >1 dose of epinephrine and/or fluid bolus have a significantly higher risk of developing biphasic reactions (58% vs. 22%, p=0.01) 2. The absence of these factors has an excellent negative predictive value of 99% for biphasic reactions 2.

Discharge Criteria

Patients may be considered for discharge when:

• Complete resolution of all anaphylactic symptoms has occurred 1
• Appropriate observation period based on risk factors has been completed 1
• Patient has received education on:
  • Anaphylaxis emergency action plan 1
  • Proper use of epinephrine auto-injector 1
  • Recognition of anaphylaxis symptoms 1
  • Avoidance of triggers 1
• Two doses of epinephrine auto-injector have been prescribed 1
• Follow-up with an allergist has been arranged 1

Common Pitfalls to Avoid

1. Premature discharge: Failing to observe patients long enough after symptom resolution, especially those with risk factors for biphasic reactions 1, 3

2. Overreliance on antihistamines/glucocorticoids: These medications are not reliable interventions to prevent biphasic anaphylaxis and should not influence admission decisions 1

3. Failure to recognize severity markers: Wide pulse pressure, need for multiple epinephrine doses, and fluid resuscitation are important indicators of potential biphasic reactions 1, 2

4. Inadequate discharge planning: All patients must leave with epinephrine auto-injectors, action plans, and follow-up arrangements regardless of admission status 1

By following these evidence-based guidelines for hospital admission after anaphylaxis, clinicians can optimize patient safety while appropriately allocating healthcare resources based on individual risk factors for biphasic reactions.