Anaphylactic Shock (Anaphylaxis)

Anaphylactic Shock (Anaphylaxis) – Treatment Overview

Introduction
Anaphylactic shock is the most severe form of anaphylaxis, characterized by circulatory collapse, airway obstruction, and multi-organ dysfunction. It results from widespread mast cell and basophil mediator release after allergen exposure (foods, insect stings, drugs, latex). Rapid recognition and immediate treatment with epinephrine are essential to prevent death.

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Emergency Management (First-Line)

1. Epinephrine (life-saving drug, never delay)

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

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

• Auto-injector (e.g., EpiPen) if available.

• IV infusion: Consider only in refractory shock, under continuous monitoring.

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Adjunctive Emergency Measures

Airway

• High-flow oxygen (6–8 L/min).

• Prepare for intubation or emergency cricothyrotomy if severe laryngeal edema/airway obstruction.

Circulation

• Place patient supine with legs elevated (unless respiratory distress).

• IV access → rapid isotonic fluids (normal saline or Ringer’s lactate):

  • Adults: 1–2 L bolus.

  • Children: 20 mL/kg bolus, repeat as needed.

Medications (secondary, after epinephrine):

• Antihistamines:

  • Diphenhydramine 25–50 mg IV/IM (H1 blocker).

  • Ranitidine or famotidine IV (H2 blocker, optional).

• Corticosteroids:

  • Methylprednisolone 1–2 mg/kg IV (not immediate effect, prevents biphasic reactions).

• Bronchodilators:

  • Albuterol via nebulizer for bronchospasm not relieved by epinephrine.

• Glucagon:

  • 1–5 mg IV bolus, then infusion if patient is on beta-blockers and unresponsive to epinephrine.

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Observation and Monitoring

• Continuous monitoring: BP, HR, O2 saturation, ECG.

• Observe for 4–6 hours after mild episodes, 12–24 hours after severe/shock episodes due to risk of biphasic anaphylaxis.

• Admit to ICU if hypotension persists or airway compromise occurred.

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Long-Term Management and Prevention

• Prescribe two epinephrine auto-injectors upon discharge.

• Educate patient and family on recognition and prompt use of auto-injectors.

• Avoid known allergens.

• Medical alert identification (bracelet/necklace).

• Refer to allergist for evaluation, testing, and possible immunotherapy (e.g., insect venom).