Anaphylaxis

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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. IgE-mediated mast cell degranulation in anaphylaxis

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. Anaphylaxis: Allergens, Symptoms, and Treatment

⭐ 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).

Anaphylaxis Diagnostic Criteria (NIAID/FAAN)

⭐ 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.

EpiPen administration steps

Anaphylaxis: Long-term & Prevention - Allergy Armor Up

Anaphylaxis Action Plan and EpiPen Use

  • 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).

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