Anaphylactic Reaction (Anaphylaxis)

Anaphylactic Reaction (Anaphylaxis) – Treatment Overview

Introduction
Anaphylaxis is a severe, life-threatening systemic hypersensitivity reaction that occurs rapidly after exposure to an allergen such as food, insect stings, medications, or latex. It involves IgE-mediated mast cell and basophil degranulation, leading to massive release of histamine and other mediators. Clinical features include airway compromise (laryngeal edema, bronchospasm), circulatory collapse (hypotension, shock), and skin manifestations (urticaria, angioedema).

Immediate recognition and treatment are critical to prevent death.

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Emergency Treatment (First-Line)

1. Epinephrine (Adrenaline) – cornerstone therapy

• Adults: 0.3–0.5 mg intramuscularly (IM) into the mid-outer thigh, 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) if available.

• IV epinephrine infusion only in refractory cases, with close monitoring.

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Adjunctive Management

2. Airway and Breathing

• High-flow oxygen.

• Prepare for advanced airway management (intubation or cricothyrotomy if severe laryngeal edema).

3. Circulation

• Place patient supine with legs elevated unless respiratory distress prevents.

• Establish IV access, give rapid IV fluids (normal saline or Ringer’s lactate) – 1–2 L in adults, 20 mL/kg in children if hypotension persists.

4. Medications (after epinephrine, never delay for these):

• Antihistamines (H1 blockers): Diphenhydramine 25–50 mg IV/IM; helps cutaneous symptoms but not life-saving.

• H2 blockers: Ranitidine or famotidine may be added.

• Corticosteroids: Methylprednisolone 1–2 mg/kg IV or equivalent; not immediate but may reduce biphasic reactions.

• Bronchodilators: Inhaled albuterol for bronchospasm unresponsive to epinephrine.

• Glucagon: For patients on beta-blockers with refractory hypotension – 1–5 mg IV bolus followed by infusion.

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Observation and Follow-Up

• Observe patient for at least 4–6 hours (mild cases) or 12–24 hours (severe cases, history of biphasic reactions).

• Prescribe epinephrine auto-injector on discharge and educate on use.

• Refer to allergist for evaluation and identification of triggers.

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Prevention

• Avoid known allergens (foods, drugs, stings).

• Wear medical alert bracelet.

• Carry two epinephrine auto-injectors at all times.

• Consider allergen immunotherapy (e.g., for insect venom allergy).