Protocol for Managing an Allergic Reaction
The management of allergic reactions should follow a graded approach based on severity, with epinephrine as the first-line treatment for anaphylaxis, administered immediately upon recognition of symptoms. 1
Classification of Allergic Reactions
Grade I (Mild)
- Localized cutaneous signs: flushing, urticaria, angioedema
Grade II (Moderate)
- Moderate multi-organ involvement
- Cutaneous signs with moderate hypotension, tachycardia, bronchospasm, or GI symptoms
Grade III (Severe/Life-threatening)
- Life-threatening mono- or multi-organ involvement
- Severe hypotension, tachycardia/bradycardia, severe bronchospasm
Grade IV (Cardiac/Respiratory Arrest)
- Cardiac or respiratory arrest
Emergency Management Protocol
For Grade I (Mild) Reactions
- H1 antihistamines: Diphenhydramine 50 mg orally/IV every 6 hours for 2-3 days 1
- Consider non-sedating second-generation antihistamines as alternatives 2
- H2 antihistamines: Ranitidine 50 mg IV 1
- Observe for progression to more severe symptoms 1
For Grade II (Moderate) Reactions
- Administer IV epinephrine 20 μg if vasopressor/bronchodilator indicated 1
- Increase to 50 μg at 2 minutes if unresponsive to initial dose 1
- If IV access unavailable, administer IM epinephrine 300 μg 1
- Administer crystalloid 500 mL rapid bolus, repeat if inadequate response 1
- H1/H2 antihistamines as above
For Grade III (Severe) Reactions
- Administer IV epinephrine 50 μg immediately 1
- Increase to 100 μg if unresponsive to other vasopressors/bronchodilators 1
- Escalate to 200 μg at 2 minutes if unresponsive to initial dose 1
- Administer crystalloid 1 L rapid bolus, repeat as needed 1
- H1/H2 antihistamines as adjunctive therapy 1
- Corticosteroids: Methylprednisolone 1-2 mg/kg IV every 6 hours 1
For Grade IV (Cardiac/Respiratory Arrest)
- Administer epinephrine 1 mg IV 1
- Repeat as per Advanced Life Support guidelines 1
- Consider extracorporeal membrane oxygenation if available 1
- Begin cardiac compressions if systolic BP <50 mmHg or end-tidal CO2 <3 kPa 1
For Refractory Anaphylaxis (>10 minutes after symptom onset)
- Double epinephrine dose 1
- Consider epinephrine infusion 0.05-0.1 μg/kg/min after three boluses 1
- Consider additional agents:
Dosing Guidelines
Adults and Children ≥30 kg
- IM epinephrine: 0.3-0.5 mg (0.3-0.5 mL of 1:1000) in anterolateral thigh 3
- Repeat every 5-10 minutes as necessary 3
Children <30 kg
- IM epinephrine: 0.01 mg/kg (0.01 mL/kg of 1:1000) in anterolateral thigh 3
- Maximum 0.3 mg per injection 3
- Repeat every 5-10 minutes as necessary 3
Post-Reaction Management
Observation
- Monitor all patients who receive epinephrine for 4-6 hours 1, 2
- Consider longer observation or hospital admission for severe reactions 2
- Monitor for biphasic reactions, which can occur up to 72 hours later 2
Follow-up Care
- Provide an emergency action plan 1, 2
- Prescribe epinephrine auto-injector and provide training 1, 2
- Continue medications for 2-3 days:
- Schedule follow-up with primary care provider and consider allergist referral 1, 4
Critical Pitfalls to Avoid
Delaying epinephrine administration - This is associated with increased mortality; administer promptly when anaphylaxis is suspected 2, 4, 5
Using antihistamines alone for anaphylaxis - Antihistamines are not a substitute for epinephrine in anaphylaxis 2, 6
Insufficient observation time - Monitor patients for potential biphasic reactions 2, 7
Inadequate patient education - Provide clear instructions on allergen avoidance and proper use of epinephrine 2, 4
Failing to prescribe autoinjectors - Patients at risk should carry two doses of epinephrine at all times 2, 5
Repeated injections at the same site - This can cause tissue necrosis due to vasoconstriction 3
Remember that epinephrine is the cornerstone of anaphylaxis treatment, with no absolute contraindications when indicated for a life-threatening reaction 2, 5.