What is the immediate treatment for a patient experiencing anaphylaxis?

Immediate Treatment for Anaphylaxis

The immediate first-line treatment for anaphylaxis is intramuscular epinephrine administration in the mid-outer thigh (vastus lateralis muscle), which should be given without delay, followed by activation of emergency medical services. 1, 2

Initial Management Algorithm

1. Recognize anaphylaxis signs and symptoms:

   • Lip and facial swelling
   • Sensation of throat closing
   • Difficulty breathing
   • Skin manifestations (rash, urticaria)
   • Gastrointestinal symptoms (vomiting, diarrhea)
   • Signs of hypotension (altered consciousness, pallor, dizziness)

2. Administer epinephrine immediately:

   • Adults and children ≥30 kg: 0.3-0.5 mg IM (maximum 0.5 mg)
   • Children <30 kg: 0.01 mg/kg IM (maximum 0.3 mg)
   • Administer into vastus lateralis (mid-outer thigh) for optimal absorption 1, 2
   • Use autoinjector if available or draw from ampule using syringe 1

3. Activate emergency response system/call 911 simultaneously 1, 2

4. Position the patient appropriately:

   • Supine or Trendelenburg position if hypotensive
   • Sitting up if experiencing respiratory distress 1, 2

5. Establish IV access and administer fluids:

   • Use large-bore catheter
   • Administer 0.9% saline or lactated Ringer's for hypotension 1, 2

6. Administer supplemental oxygen as needed for respiratory symptoms 1, 2

Secondary Interventions (after epinephrine)

• Repeat epinephrine every 5-15 minutes if symptoms persist or worsen 1, 2
• Consider adjunctive medications (only after epinephrine administration):
  • H1 antihistamines (e.g., diphenhydramine 25-50 mg IV/IM)
  • H2 antihistamines (e.g., ranitidine 50 mg IV)
  • Note: Antihistamines only address cutaneous symptoms, not life-threatening manifestations 1, 2
• Consider nebulized albuterol (2.5-5 mg) for persistent bronchospasm 2
• For refractory cases:
  • IV epinephrine infusion (1:10,000 concentration) may be necessary 1
  • Vasopressor infusion for hypotension unresponsive to fluids and epinephrine 2
  • Glucagon (1-5 mg IV) for patients on beta-blockers with poor response 2

Important Considerations

• No absolute contraindications exist for using epinephrine to treat anaphylaxis, even in patients with cardiac disease, advanced age, or frailty 1
• Delay in administering epinephrine has been associated with increased mortality and morbidity 1, 2, 3
• Glucocorticoids have no role in treating acute anaphylaxis given their slow onset of action 1
• Biphasic reactions can occur up to 72 hours after initial symptoms resolve, with a mean of 11 hours 1
• Extended observation (4-6 hours minimum) is recommended after symptom resolution 2
• Consider longer observation or hospital admission for severe reactions or those requiring multiple epinephrine doses 1, 2

Common Pitfalls to Avoid

• Delaying epinephrine administration to administer antihistamines or steroids first 2, 3
• Discharging patients too early without adequate observation for biphasic reactions 1, 2
• Relying on antihistamines or steroids as primary treatment instead of epinephrine 4, 5
• Administering epinephrine via incorrect route (should be IM in vastus lateralis) 1
• Failing to recognize anaphylaxis due to atypical presentation 5

The evidence consistently demonstrates that early administration of intramuscular epinephrine is the cornerstone of anaphylaxis management, with all other interventions being secondary and supportive 1, 2, 4. Epinephrine is the only medication shown to reverse the pathophysiological effects of anaphylaxis, and its prompt administration is associated with reduced mortality and morbidity 6, 3.