What is the immediate treatment for an anaphylactic reaction?

Immediate Treatment of Anaphylaxis

The immediate first-line treatment for anaphylaxis is prompt administration of intramuscular epinephrine, which should be given without delay at the first signs of a systemic allergic reaction. 1, 2

Initial Management Algorithm

1. Administer epinephrine immediately:

   • Adults and children ≥30 kg: 0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution) intramuscularly in the anterolateral thigh 3
   • Children <30 kg: 0.01 mg/kg (0.01 mL/kg of 1:1000 solution), up to 0.3 mg, intramuscularly in the anterolateral thigh 3
   • Repeat every 5-10 minutes as necessary if symptoms persist 2, 3

2. Position the patient appropriately:

   • Place in recumbent position with legs elevated 2
   • For pregnant patients, position with left uterine displacement to avoid aortocaval compression 2

3. Establish and maintain airway:

   • Administer oxygen if available 1
   • Monitor oxygen saturation
   • Be prepared for intubation if severe respiratory distress occurs

4. Administer IV fluids for hypotension:

   • Crystalloid 500-1000 mL rapid bolus for adults 2
   • 20 mL/kg for children, repeated as needed 2

Severity-Based Management

Grade II reactions (systemic reaction without life-threatening features)

• IV epinephrine 20 μg if clinically indicated
• If unresponsive after 2 minutes, administer 50 μg IV epinephrine 2

Grade III reactions (life-threatening hypotension or bronchospasm)

• IV epinephrine 50-100 μg
• If unresponsive after 2 minutes, administer 200 μg IV epinephrine 2

Grade IV reactions (cardiac or respiratory arrest)

• Follow advanced life support protocols
• IV epinephrine 1 mg
• Initiate cardiac compressions for inadequate cardiac output 2

Refractory Management (inadequate response after 10 minutes)

• Escalate epinephrine dose (double the bolus dose)
• Start epinephrine infusion (0.05-0.1 μg/kg/min)
• Consider epinephrine infusion after three bolus doses
• Escalate fluid administration up to 20-30 mL/kg 2

Special Considerations

• Patients on beta-blockers: Consider IV glucagon 1-2 mg if poor response to epinephrine 2, 1
• Pregnant patients: Early treatment with IV epinephrine is recommended; consider emergency cesarean section if persistent hypotension despite resuscitation 2
• Mastocytosis patients: Use caution with histamine-releasing agents; premedication with H1/H2 antagonists and corticosteroids may be beneficial 2

Adjunctive Therapies (only after epinephrine)

• Antihistamines: May be administered after adequate epinephrine and fluid resuscitation, but not a priority 2
• Corticosteroids: May be given after adequate resuscitation 2
• Bronchodilators: Consider for persistent bronchospasm 2

Common Pitfalls to Avoid

1. Delayed epinephrine administration: The most common and dangerous error in anaphylaxis management 1, 4
2. Relying solely on antihistamines: These should never replace epinephrine as first-line treatment 1
3. Improper route of administration: Intramuscular injection in the anterolateral thigh achieves higher and more rapid plasma concentrations than subcutaneous or intramuscular injection in the arm 2, 5
4. Insufficient monitoring: Observe patients for at least 6 hours after symptom resolution due to risk of biphasic reactions 2, 1
5. Epinephrine overdose: Can cause serious adverse effects; follow recommended dosing 4

Post-Treatment Observation

• Monitor in a supervised setting for a minimum of 6 hours or until stable with regressing symptoms 2
• Longer observation (up to 24 hours) may be warranted for patients with severe reactions, those requiring multiple epinephrine doses, or those with risk factors for biphasic reactions 1, 6

Remember that there are no contraindications to epinephrine administration in patients experiencing anaphylaxis, and the benefits far outweigh the risks even in patients with cardiovascular disease 2.