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Clinical Summary

Anaphylaxis: fewer biphasic reactions with earlier epinephrine

Takeaway

  • For patients with anaphylaxis, minimal delays to epinephrine treatment may reduce risk for biphasic reaction.
  • Administration upon emergency department (ED) arrival vs beforehand was associated with 3-fold risk for repeat reaction.

Why this matters

  • Risk factors for biphasic reaction are poorly understood, complicating disposition decisions.

Key results

  • Biphasic reactions occurred in 7.2% (n=31; 95% CI, 5.0%-10.2%).
  • Clinically significant (CS) biphasic reactions occurred in 5.1% (n=22; 95% CI, 3.3%-7.8%).
  • Biphasic vs uniphasic reaction:
    • Median time to first epinephrine dose: 78 vs 45 minutes (P=.005).
  • Factors associated with biphasic reactions (ORs):
    • History of food allergy: 0.38 (P=.02).
    • First epinephrine in ED vs prehospital: 3.72 (P=.007).
    • Arrival by ambulance: 0.18 (P=.002).
    • ≥30-minute delay between symptom onset and epinephrine: 3.39 (P=.02).
  • Factors associated with CS biphasic reactions (ORs):
    • Age ≥18 years: 0.39 (P=.029).
    • Arrival by ambulance: 0.08 (P=.002).
    • First epinephrine in ED: 3.32 (P=.03).

Study design

  • Prospective cohort study of patients of any age presenting to 2 EDs with anaphylaxis (430 visits).
  • Outcome: incidence of biphasic reaction (repeat anaphylaxis within 72 hours, without known reexposure); risk factors.
  • Funding: None.

Limitations

  • Few biphasic reactions, limiting power.
  • 1 in 4 could not identify trigger, making reexposure a possibility.

References


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