Anaphylaxis

Anaphylaxis: Definition & Pathophysiology - Shocking Speed Reaction

• Definition: Severe, life-threatening, generalized or systemic hypersensitivity reaction with rapid onset.
• Pathophysiology:
  • Primarily Type I Hypersensitivity (IgE-mediated).
  • Mechanism: Allergen cross-links IgE on mast cells & basophils → degranulation.
  • Mediators Released:
    • Preformed: Histamine (vasodilation, ↑vascular permeability), Tryptase.
    • Newly Synthesized: Leukotrienes (bronchoconstriction), Prostaglandins, Platelet-Activating Factor (PAF).
  • Non-IgE mediated (Anaphylactoid): Direct mast cell/basophil degranulation (e.g., radiocontrast media, opioids, NSAIDs).

⭐ Serum tryptase levels peak 1-2 hours after onset of symptoms and can be a useful diagnostic marker.

Anaphylaxis: Triggers & Risk Factors - Culprit Countdown

• Top Triggers (📌 FILM):
  • Foods: Peanuts, tree nuts, milk, eggs, shellfish. (Common in children)
  • Medications: NSAIDs, penicillins, contrast media. (Common in adults)
  • Insect Stings: Bees, wasps, ants.
  • Latex.
• Key Risk Factors:
  • Atopy (asthma, eczema).
  • History of previous anaphylaxis.
  • Mastocytosis.
  • ⚠️ Beta-blockers/ACE-inhibitors may worsen severity.

⭐ Food is the most common trigger of anaphylaxis in children, while medications are more common in adults.

Anaphylaxis: Clinical Features & Diagnosis - Symptom Storm Signs

Rapid onset (mins-hrs) multi-system reaction.

• Skin/Mucosal (~90%): Urticaria, angioedema (lips, tongue, larynx), pruritus, flushing.
• Respiratory (~70%):
  • Lower: Dyspnea, wheeze.
  • Upper: Stridor, hoarseness (⚠️ laryngeal edema).
• Cardiovascular (~45%): Hypotension (SBP <90 mmHg or >30% drop), tachycardia, shock.
• GI (~45%): Nausea, vomiting, abdominal pain.
• Other: Sense of impending doom.

Diagnosis: Clinical. NIAID/FAAN criteria key. Lab (supportive): ↑ Serum tryptase (peaks 1-2 hrs).

⭐ Biphasic anaphylaxis (symptom recurrence 1-72 hrs later without re-exposure) occurs in up to 20% of cases.

Anaphylaxis: Acute Management - Epi Pen Power Play

• Immediate: Assess ABCs. Call help. Position supine, legs elevated (respiratory distress: semi-recumbent).
• IM Epinephrine (1:1000): First-line! STAT to anterolateral thigh.
  • Dose: 0.01 mg/kg.
    • Adult: 0.3-0.5 mg.
    • Child: 0.01 mg/kg (max 0.3 mg).
  • Repeat 5-15 min if symptoms persist/recur.
• EpiPen®:
  • Adult (>30kg): 0.3mg.
  • Child (15-30kg): 0.15mg. 📌 Jr. for 0.15mg.
• Adjuncts (after Epinephrine):
  • Oxygen: High flow 6-8 L/min.
  • IV Fluids: NS/RL 10-20 ml/kg rapid bolus.
  • Antihistamines: H1 (Diphenhydramine) + H2 blockers (Ranitidine).
  • Corticosteroids: Hydrocortisone to prevent biphasic reaction (onset 4-6 hrs).
  • Bronchodilators: Salbutamol for persistent wheezing.

⭐ β-blocker refractory anaphylaxis: Glucagon 1-5 mg IV over 5 min, then infusion.

Anaphylaxis: Long-term & Prevention - Allergy Armor Up

• Epinephrine Auto-Injector (EAI): Prescribe TWO devices. Train patient & family on correct use (e.g., technique, expiry).
• Allergen Avoidance: Strict, educated avoidance of identified triggers. Emphasize food label reading.
• Written Anaphylaxis Action Plan: Clear emergency steps for patient/caregivers.
• Specialist Referral: To Allergist/Immunologist for evaluation & potential immunotherapy.
• Medical Alert Jewelry: Strongly recommended.

⭐ Biphasic anaphylaxis occurs in up to 20% of cases, typically 1-72 hours (commonly 8-12 hrs) after initial resolution; mandates adequate observation post-treatment.

High‑Yield Points - ⚡ Biggest Takeaways

• Anaphylaxis: Severe, rapid-onset systemic hypersensitivity reaction, potentially life-threatening.
• Key triggers: Foods (milk, peanut), drugs (penicillin), insect stings.
• Pathophysiology: IgE-mediated mast cell degranulation releasing histamine.
• Clinical: Multi-system (skin, respiratory, CV, GI); biphasic reaction possible (1-72 hrs).
• Treatment cornerstone: IM Adrenaline (0.01 mg/kg, 1:1000) in anterolateral thigh.
• Adjuncts: Corticosteroids (prevent biphasic), antihistamines, oxygen, IV fluids.
• Diagnosis: Primarily clinical; serum tryptase may be elevated post-reaction (peaks 1-2 hrs).