What is the immediate treatment for anaphylaxis?

Immediate Treatment for Anaphylaxis

Intramuscular epinephrine is the only first-line treatment for anaphylaxis and must be administered immediately—all other interventions are secondary and should never delay epinephrine. 1, 2

Primary Intervention: Epinephrine Administration

Administer intramuscular epinephrine 0.01 mg/kg (1:1000 concentration) into the vastus lateralis (anterolateral thigh) immediately upon recognition of anaphylaxis. 1, 3

Dosing specifics:

• Adults and children >50 kg: 0.5 mg maximum single dose 1
• Children 25-50 kg: 0.3 mg (or 0.3 mg autoinjector) 1
• Children 10-25 kg: 0.15 mg (or 0.15 mg autoinjector) 1
• Repeat every 5-15 minutes if symptoms persist or progress 1

Critical administration details:

• The lateral thigh (vastus lateralis) is the mandatory injection site because intramuscular administration in the thigh achieves higher peak plasma concentrations more rapidly than subcutaneous or deltoid injection 1
• There are no absolute contraindications to epinephrine in anaphylaxis, including cardiac disease, advanced age, or frailty 1, 2
• Epinephrine autoinjectors should be used if available to minimize dosing errors when staff experience is limited 1

Immediate Concurrent Actions

While preparing or immediately after epinephrine:

1. Activate emergency medical services (call 911) 1
2. Position patient supine with legs elevated (if tolerated and no respiratory distress) 1
3. Stop any ongoing allergen exposure (e.g., stop IV medication infusion) 1

Secondary Interventions (After Epinephrine)

Fluid resuscitation for hypotension:

• Administer rapid IV crystalloid bolus: 500-1000 mL in adults, 10-20 mL/kg in children 1, 2
• Hypotension in anaphylaxis results from massive fluid shifts and requires aggressive volume replacement 1

Supplemental oxygen:

• Provide 6-8 L/min via face mask for respiratory symptoms 1, 2

Bronchodilators (only after epinephrine):

• Nebulized albuterol 2.5-5 mg (adults) or 1.5 mL (children) for persistent bronchospasm despite epinephrine 1

Antihistamines (adjunctive only):

• H1 antihistamine: Diphenhydramine 25-50 mg IV (1-2 mg/kg in children, max 50 mg) 1
• H2 antihistamine: Ranitidine 50 mg IV over 5 minutes (1 mg/kg in children) 1
• The combination of H1 + H2 antihistamines is superior to H1 alone, but these only address cutaneous symptoms and have no role in life-threatening manifestations 1, 2

What NOT to Do: Critical Pitfalls

Never administer antihistamines or corticosteroids before or instead of epinephrine—this practice is associated with increased mortality 1, 2, 4

Do not give glucocorticoids for acute anaphylaxis treatment—they have no role due to slow onset of action (hours) and do not prevent biphasic reactions 1, 2

Avoid IV epinephrine in initial management unless the patient is in cardiac arrest or profound shock unresponsive to multiple IM doses, as IV administration carries higher risk of cardiac complications 1

Do not delay epinephrine administration—fatalities are directly associated with delayed epinephrine, and early administration reduces risk of biphasic reactions 1

Refractory Anaphylaxis Management

If symptoms persist after 2-3 doses of IM epinephrine:

• Consider IV epinephrine infusion (1:10,000 concentration) with continuous hemodynamic monitoring 1
• For patients on beta-blockers: Consider glucagon 1-5 mg IV over 5 minutes, followed by infusion (5-15 mg/min), as epinephrine may be less effective 1
• Escalate vasopressor support (dopamine 2-20 mcg/kg/min) for refractory hypotension 1

Observation and Disposition

All patients must be observed in a monitored setting for minimum 4-6 hours after complete symptom resolution 1, 2

Extend observation to 24 hours or admit patients who: 1, 2

• Required >1 dose of epinephrine (odds ratio 4.82 for biphasic reaction) 1
• Had severe initial presentation
• Have significant comorbidities (asthma, cardiovascular disease)

Biphasic reactions occur in 7-18% of cases, with mean onset at 11 hours (range up to 72 hours), making extended observation critical for high-risk patients 1

Discharge Requirements

Every patient must leave with: 1

• Two epinephrine autoinjectors (one may be insufficient)
• Written anaphylaxis emergency action plan
• Education on trigger avoidance and autoinjector use
• Referral to allergist for definitive evaluation