Anaphylaxis

Anaphylaxis – Treatment Overview

Introduction
Anaphylaxis is a rapid-onset, severe, systemic allergic reaction that can be life-threatening. It usually follows exposure to allergens such as foods (peanuts, shellfish), insect stings, medications (penicillin, NSAIDs), or latex. The reaction involves massive histamine and mediator release from mast cells and basophils, leading to airway compromise (bronchospasm, laryngeal edema), cardiovascular collapse (hypotension, shock), and skin/mucosal symptoms (urticaria, angioedema).

Immediate recognition and prompt treatment with epinephrine are essential.

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First-Line Emergency Treatment

Epinephrine (Adrenaline) – cornerstone of therapy

• Adults: 0.3–0.5 mg IM (1:1000 = 1 mg/mL) into the mid-outer thigh. May repeat every 5–15 minutes as needed.

• Children: 0.01 mg/kg IM (max 0.3 mg per dose).

• Use auto-injector (e.g., EpiPen, Jext, Auvi-Q) if available.

• IV epinephrine infusion only for refractory cases, under continuous monitoring.

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Adjunctive Management

Airway and Breathing

• High-flow oxygen.

• Prepare for advanced airway management (intubation or surgical airway if severe swelling).

Circulation

• Place patient supine with legs elevated unless respiratory distress.

• Rapid IV fluids (normal saline or Ringer’s lactate):

  • Adults: 1–2 L bolus.

  • Children: 20 mL/kg bolus.

Additional Medications (after epinephrine, never as substitute):

• Antihistamines:

  • Diphenhydramine 25–50 mg IV/IM for H1 blockade.

  • H2 blockers (ranitidine, famotidine) may be added.

• Corticosteroids:

  • Methylprednisolone 1–2 mg/kg IV or equivalent; not immediate but reduces biphasic/protracted reactions.

• Bronchodilators:

  • Inhaled albuterol for bronchospasm unresponsive to epinephrine.

• Glucagon:

  • 1–5 mg IV bolus then infusion if patient is on beta-blockers and not responding to epinephrine.

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Observation and Follow-Up

• Monitor vitals continuously.

• Observation period:

  • Mild reactions: at least 4–6 hours.

  • Severe or biphasic risk: 12–24 hours.

• Prescribe two epinephrine auto-injectors for all patients after an episode.

• Educate on recognition of recurrence and proper injector use.

• Refer to an allergist for trigger identification and long-term prevention.

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Prevention

• Avoid known allergens.

• Wear a medical alert bracelet/necklace.

• Carry epinephrine auto-injectors at all times.

• Allergen immunotherapy may be considered (e.g., insect venom).