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
References