Management of Anaphylaxis

Anaphylaxis Alert - Spotting the Storm

• Definition: Severe, life-threatening allergic reaction. NIAID/FAAN criteria involve rapid onset with skin/mucosal signs + respiratory compromise OR ↓BP; OR ≥2 systems (skin, respiratory, CVS, GI) involved post-allergen.
• Triggers: Foods (peanuts, tree nuts, shellfish), drugs (penicillin, NSAIDs), insect stings.
• Pathophysiology: IgE-mediated mast cell/basophil degranulation → histamine, tryptase release → vasodilation, ↑permeability, bronchoconstriction.
• Clinical Features (📌 ALARM):
  • Airway: Stridor, wheeze, dyspnea.
  • Look (Skin): Urticaria (>80%), angioedema, flushing.
  • Abdomen: Nausea, vomiting, cramps.
  • Reduced BP (CVS): Hypotension, tachycardia, syncope.
  • Mental: Anxiety, doom.
• Biphasic Reaction: Symptom recurrence 1-72 hrs later (up to 20% cases).

⭐ Serum tryptase levels peak 1-2 hours after onset, aiding retrospective diagnosis (baseline in 6-24 hrs).

Adrenaline Rush - The First Punch

• First-line: Adrenaline (Epinephrine) - immediate, life-saving.
• Mechanism: α1 (vasoconstriction, ↓edema), β1 (↑heart rate/contractility), β2 (bronchodilation, ↓mediator release).
  • 📌 Mnemonic: "Adrenaline's Action Boosts Circulation & Breathing": Alpha, Beta-1, Beta-2.
• Route: IM, anterolateral mid-thigh. (Superior to SC).
  • 
• Dose (1:1000 solution):
  • Adults: 0.3-0.5 mg (max 0.5 mg)
  • Children: 0.01 mg/kg (max 0.3 mg)
• Repeat: Every 5-15 mins if needed.
• Positioning:
  • Supine, legs elevated (if hypotensive).
  • Sit up if severe respiratory distress or vomiting.

⭐ Exam Favourite: IM adrenaline in the anterolateral thigh achieves faster and higher peak plasma levels than SC injection.

Backup Brigade - Supporting Cast

• Oxygen: High flow 8-10 L/min.
• IV Fluids: Crystalloids (NS/RL) 10-20 ml/kg rapid bolus.
• Antihistamines:
  • H1 Blocker: Diphenhydramine 25-50 mg IV/IM or Cetirizine 10 mg IV/PO.
  • H2 Blocker: Ranitidine 50 mg IV.
  • For cutaneous symptoms; no effect on BP/airway.
• Corticosteroids:
  • Hydrocortisone 100-200 mg IV or Methylprednisolone 1-2 mg/kg IV.
  • Onset 4-6 hrs; prevent biphasic/protracted reactions.
• Bronchodilators:
  • Salbutamol nebulized (5 mg) for persistent wheezing.

⭐ Antihistamines & corticosteroids are second-line; NEVER delay adrenaline administration.

Tough Cases & Twists - When It Gets Tricky

• Refractory Anaphylaxis: Persistent hypotension or bronchospasm despite ≥2 appropriate adrenaline doses.
  • Management:

• Biphasic Reactions: Symptoms recur hours later. Management similar to initial episode.
• Observation Period: Minimum 4-8 hours post-symptom resolution. Longer for severe reactions or biphasic risk.
• Discharge Planning: Crucial for future safety.
  • Comprehensive Adrenaline Auto-Injector (AAI) training.
  • 
  • Prompt allergy referral, detailed written action plan.

⭐ Glucagon is crucial for anaphylaxis in patients on beta-blockers refractory to adrenaline, due to its positive inotropic/chronotropic effects independent of beta-receptors.

High‑Yield Points - ⚡ Biggest Takeaways

• Intramuscular Adrenaline is life-saving and first-line; administer into anterolateral thigh.
• Dose: Adults 0.3-0.5 mg (1:1000); Children 0.01 mg/kg. Repeat q5-15 mins PRN.
• Prioritize airway management; early intubation for severe angioedema/respiratory compromise.
• Antihistamines (H1/H2) & corticosteroids are adjunctive, not primary treatment.
• Manage hypotension with IV crystalloids; administer supplemental oxygen.
• Consider glucagon for patients on beta-blockers refractory to adrenaline.
• Observe 4-8 hours post-resolution for potential biphasic reactions.