What is the treatment for anaphylaxis?

Treatment for Anaphylaxis

The first-line treatment for anaphylaxis is immediate administration of epinephrine via intramuscular injection in the mid-outer thigh (vastus lateralis muscle) as soon as anaphylaxis is recognized. 1, 2

Immediate Management Algorithm

1. Recognition and Initial Response

   • Recognize anaphylaxis symptoms: skin manifestations (hives, swelling), respiratory symptoms (difficulty breathing, wheezing), cardiovascular symptoms (hypotension, tachycardia), and/or gastrointestinal symptoms (vomiting, abdominal pain) 1
   • Call for emergency assistance (911/EMS) 3
   • Position patient appropriately: recumbent with legs elevated if hypotensive 1

2. Epinephrine Administration

   • Dosing:
     • Adults and children ≥30 kg: 0.3-0.5 mg (0.3-0.5 mL of 1:1000 concentration) 1, 3
     • Children <30 kg: 0.01 mg/kg, maximum 0.3 mg (0.01 mL/kg of 1:1000 concentration) 1, 3
   • Route: Intramuscular injection in the mid-outer thigh (vastus lateralis) 1
   • Timing: Repeat every 5-15 minutes if symptoms persist or worsen 1

3. Airway Management

   • Establish and maintain airway 1
   • Administer oxygen at 6-8 L/min 1
   • Monitor for signs of airway compromise; endotracheal intubation may be necessary in severe cases 1

4. Fluid Resuscitation

   • Establish intravenous access 1
   • Administer normal saline for fluid replacement (1-2 L may be required for adults) 1

Secondary Interventions

After epinephrine administration, consider the following adjunctive therapies:

1. Antihistamines

   • H1 antagonists (e.g., diphenhydramine 25-50 mg IV/IM) for cutaneous symptoms 3
   • H2 antagonists (e.g., ranitidine 50 mg IV or famotidine 20 mg IV) may be added 3

2. Bronchodilators

   • Albuterol 2.5-5 mg via nebulizer for persistent bronchospasm 3

3. Corticosteroids

   • Methylprednisolone 1-2 mg/kg IV or prednisone 0.5 mg/kg orally to potentially prevent biphasic reactions 3

4. Vasopressors

   • For refractory hypotension, consider dopamine (2-20 μg/kg/min) titrated to maintain systolic BP >90 mmHg 1

Monitoring and Follow-up

• Monitor vital signs continuously, including blood pressure, heart rate, and oxygen saturation 3
• Observe patients for at least 4-6 hours after symptom resolution due to risk of biphasic reactions 3
• High-risk patients (severe initial reaction, requiring multiple epinephrine doses) may need extended observation (≥6 hours) or hospital admission 3

Important Considerations and Pitfalls

• Delayed epinephrine administration is associated with increased mortality. Never delay giving epinephrine while administering secondary medications. 1, 4

• Route matters: Intramuscular injection in the thigh produces higher and more rapid peak plasma levels compared to subcutaneous or arm injections. 1, 5

• Epinephrine autoinjectors (e.g., EpiPen) can be used through clothing into the lateral thigh for rapid administration. 1

• Biphasic reactions can occur in up to 20% of cases, with symptoms recurring hours after initial resolution without re-exposure to the trigger. 6

• Avoid standing or walking during acute anaphylaxis as this can worsen hypotension and accelerate vascular collapse. 1

• No absolute contraindications exist for epinephrine use in anaphylaxis, even in patients with cardiovascular disease. The benefits outweigh the risks. 1

• Patient education is essential, including prescription of epinephrine autoinjectors (typically 2), training on their use, and development of an emergency action plan. 7, 8