What is the management of anaphylaxis?

Management of Anaphylaxis

Epinephrine is the first-line treatment for anaphylaxis and should be administered immediately at a dose of 0.01 mg/kg of 1:1000 (1 mg/mL) solution intramuscularly into the anterolateral thigh, with a maximum of 0.3 mg in children and 0.5 mg in adults. 1

Immediate Management Algorithm

1. Recognize anaphylaxis using validated clinical criteria:

   • Acute onset of illness with skin/mucosal involvement plus
   • Respiratory compromise or reduced blood pressure
   • The more rapidly anaphylaxis develops, the more likely it is to be severe 1

2. Administer epinephrine immediately:

   • Dose: 0.01 mg/kg of 1:1000 (1 mg/mL) solution
   • Route: Intramuscular (IM) into anterolateral thigh
   • Maximum dose: 0.5 mg for adults, 0.3 mg for children 1
   • Repeat every 5-15 minutes if symptoms persist 1

3. Position the patient appropriately:

   • Supine position with legs elevated for hypotension
   • Sitting position if respiratory distress predominates

4. Administer adjunctive therapies (after epinephrine):

   • Corticosteroids: Prednisone 0.5-1 mg/kg orally or hydrocortisone 200 mg IV 1
   • H1 antihistamines: Diphenhydramine 1-2 mg/kg IV/IM (max 50 mg) 1
   • H2 antihistamines: Ranitidine 1 mg/kg IV 1

5. Provide supportive care:

   • Oxygen therapy if needed
   • IV fluid resuscitation for hypotension (crystalloids initially)
   • For bronchospasm resistant to epinephrine: Albuterol 2.5-5 mg in 3 mL saline via nebulizer 1
   • For patients on beta-blockers with refractory hypotension: Consider glucagon 1-5 mg IV 1

Mechanism and Importance of Epinephrine

Epinephrine acts on both alpha and beta-adrenergic receptors to counteract the life-threatening effects of anaphylaxis 2:

• Alpha-adrenergic effects: Reduces vasodilation and vascular permeability, preventing intravascular fluid loss and hypotension
• Beta-adrenergic effects: Causes bronchial smooth muscle relaxation, alleviating bronchospasm and respiratory symptoms
• Also relieves urticaria, pruritus, angioedema, and gastrointestinal symptoms 2

Observation Period and Monitoring

• Monitor patients for at least 4-6 hours after initial symptoms resolve 1
• Longer observation (8-24 hours) recommended for:
  • Severe initial reactions
  • Patients requiring multiple doses of epinephrine
  • Patients with risk factors for biphasic reactions 1

Common Pitfalls and Caveats

1. Delayed epinephrine administration: Epinephrine should be given immediately upon recognition of anaphylaxis, as delays may be fatal 3, 4

2. Incorrect route or dose: Studies show widespread confusion among clinicians regarding proper epinephrine administration 5

   • Avoid IV route except in extreme cases under continuous hemodynamic monitoring
   • Do not confuse anaphylaxis dosing with cardiac arrest dosing

3. Over-reliance on antihistamines: Antihistamines are not effective for respiratory or cardiovascular manifestations and should not be used as first-line treatment 1

4. Failure to recognize anaphylaxis: Be aware that presentation can vary, and symptoms may evolve rapidly 6

5. Special populations:

   • Infants <15 kg may require careful dosing as standard autoinjector doses may be too high 1
   • Patients on beta-blockers may have more severe reactions and may require glucagon 1

Discharge Planning and Follow-up

1. Prescribe epinephrine autoinjectors (2 devices) with proper training on use 1

2. Create a personalized anaphylaxis emergency action plan 1

3. Arrange follow-up with an allergist-immunologist for:

   • Identification of triggers
   • Consideration of immunotherapy if appropriate
   • Long-term management plan 1

4. Patient education on:

   • Trigger avoidance
   • Recognition of early symptoms
   • Proper use of epinephrine autoinjector
   • Importance of carrying autoinjectors at all times 1, 3

The evidence strongly supports that prompt administration of epinephrine is the cornerstone of anaphylaxis management, with all other interventions being secondary and supportive 3, 4, 6.