What is the first line of treatment for a patient experiencing anaphylaxis?

First-Line Treatment for Anaphylaxis

Intramuscular epinephrine is the only first-line treatment for anaphylaxis and must be administered immediately upon recognition—there are no absolute contraindications to its use, and all other therapies are secondary. 1, 2, 3

Immediate Epinephrine Administration

Epinephrine must be given intramuscularly into the mid-outer thigh (vastus lateralis) as soon as anaphylaxis is suspected—delays in administration are directly associated with increased mortality and biphasic reactions. 1, 2, 3

Dosing Protocol

• Adults and adolescents >50 kg: 0.3-0.5 mg of 1:1000 concentration (1 mg/mL) intramuscularly 1, 2, 3
• Children 25-50 kg: 0.3 mg epinephrine autoinjector 1
• Children 10-25 kg: 0.15 mg epinephrine autoinjector 1
• Weight-based dosing: 0.01 mg/kg (maximum single dose 0.5 mg) 1, 2
• Repeat every 5-15 minutes if symptoms persist or recur—approximately 6-19% of patients require a second dose 1, 2, 3

Why Intramuscular Route in the Thigh

The vastus lateralis produces higher and more rapid peak plasma epinephrine levels compared to deltoid (arm) or subcutaneous injection, making it the only recommended site. 2, 3 Subcutaneous administration delays onset of action, and intravenous administration increases risk of adverse cardiac effects except in intensive care settings with continuous monitoring. 1, 4

Critical Patient Positioning

Place the patient supine with lower extremities elevated immediately after epinephrine administration—never allow the patient to stand, walk, or run, as upright positioning can precipitate sudden cardiovascular collapse. 2, 3 If the patient has respiratory distress or is actively vomiting, position for comfort while maintaining safety. 2

Adjunctive Treatments (Only AFTER Epinephrine)

These interventions occur concomitantly with epinephrine but are never substitutes for it and should not delay epinephrine administration: 1, 2

• Supplemental oxygen at 6-8 L/min for respiratory symptoms 1, 2, 3
• IV fluid resuscitation with normal saline in large volumes (5-10 mL/kg in first 5 minutes for adults; up to 30 mL/kg in first hour for children) for hypotension or incomplete response to epinephrine 1, 2
• Albuterol (4-8 puffs MDI for children, 8 puffs for adults, or nebulized 1.5 mL for children, 3 mL for adults) for persistent bronchospasm 1
• H1 antihistamines (diphenhydramine 1-2 mg/kg, maximum 50 mg)—oral liquid formulations are absorbed more rapidly than tablets, but these only address cutaneous symptoms which are not life-threatening 1, 2
• H2 antihistamines (ranitidine 1-2 mg/kg, maximum 75-150 mg) 1

Antihistamines and corticosteroids should never be given before or instead of epinephrine—this is a common and potentially fatal error. 3

Common Pitfalls to Avoid

• Waiting to "see if symptoms improve" before administering epinephrine—this delay is associated with fatalities 1, 3, 4
• Administering antihistamines or corticosteroids first—these are not life-saving and delay definitive treatment 3
• Using subcutaneous route or injecting into the arm—these routes are less effective 2, 3, 4
• Failing to recognize anaphylaxis due to absence of skin symptoms—while urticaria, angioedema, and pruritus occur in most cases, their absence does not rule out anaphylaxis, especially when cardiovascular or respiratory symptoms are present 1

Distinguishing Anaphylaxis from Vasovagal Reactions

Vasovagal reactions present with immediate bradycardia, pallor, weakness, and diaphoresis WITHOUT skin manifestations (no urticaria, angioedema, flushing, or pruritus). 1 In contrast, anaphylaxis typically presents with tachycardia initially, and skin symptoms are present in most cases. 1 This distinction is critical because delayed epinephrine administration in true anaphylaxis increases mortality risk, while vasovagal patients do not benefit from epinephrine and are not candidates for premedication. 1

Mandatory Observation and Transfer

All patients who receive epinephrine for anaphylaxis must be transferred to an emergency department, preferably by EMS vehicle, regardless of symptom resolution. 1, 2, 3

• Minimum observation period: 4-6 hours after symptom resolution 1, 2, 3
• Extended observation or admission is warranted for severe reactions, requirement of multiple epinephrine doses, refractory symptoms, or history of biphasic reactions 1, 2, 3

Discharge Requirements

Before discharge, ensure: 1, 2, 3

• Two epinephrine autoinjectors prescribed with hands-on training in proper use
• Written anaphylaxis emergency action plan provided
• Referral to allergist for trigger identification and long-term management
• Education on biphasic reaction risk (can occur 4-12 hours after initial event) and when to re-administer epinephrine

High-Risk Populations Requiring Heightened Vigilance

Adolescents and young adults, patients with concomitant asthma (especially poorly controlled), those with previous anaphylaxis history, and peanut/tree nut allergies are at increased risk for fatal anaphylaxis. 1, 2 These patients require epinephrine autoinjector prescriptions and aggressive early treatment at the onset of even mild symptoms. 1

Special Considerations for Refractory Anaphylaxis

For persistent hypotension despite epinephrine and IV fluids, consider continuous IV epinephrine infusion (1:10,000 concentration) with continuous hemodynamic monitoring. 1, 2 For patients on beta-blockers who are resistant to epinephrine, glucagon 1-5 mg IV over 5 minutes followed by 5-15 mcg/min infusion may be necessary—note that rapid glucagon administration can induce vomiting. 2