⚡ Emergency Reminder: In suspected anaphylaxis give Adrenaline (Epinephrine) immediately. Dose: 0.5–1 mg (0.5–1 mL of 1:1000) IM into the lateral thigh using a long needle to reach muscle. 💉 Adrenaline is life-saving – do not delay for IV access or investigations.

🚑 Initial Management Summary
📞 Call for senior/anaesthetic help early. 🛑 Remove allergen (stop drug or blood transfusion). 💨 High-flow oxygen (15 L/min) & maintain airway; patient flat unless severe dyspnoea. 💉 Adrenaline (IM 1:1000) into lateral thigh: Adult / child >12 yr: 0.5 mL (0.5 mg) Child 6–12 yr: 0.3 mL (0.3 mg) Child <6 yr: 0.15 mL (0.15 mg) ⏱️ Repeat every 5 min if no improvement. 💧 IV fluids: Adults 500–1000 mL rapid bolus (0.9% NaCl); children 20 mL/kg. 📝 Adjuncts (not first-line in UK/Resus Council guidelines, but often used): Hydrocortisone 200 mg IM/slow IV Chlorphenamine 10 mg IM/slow IV Salbutamol (Albuterol) 5 mg neb if wheeze; escalate if refractory

🚑 Initial Management Summary

📞 Call for senior/anaesthetic help early.
🛑 Remove allergen (stop drug or blood transfusion).
💨 High-flow oxygen (15 L/min) & maintain airway; patient flat unless severe dyspnoea.
💉 Adrenaline (IM 1:1000) into lateral thigh:
- Adult / child >12 yr: 0.5 mL (0.5 mg)
- Child 6–12 yr: 0.3 mL (0.3 mg)
- Child <6 yr: 0.15 mL (0.15 mg)
⏱️ Repeat every 5 min if no improvement.
💧 IV fluids: Adults 500–1000 mL rapid bolus (0.9% NaCl); children 20 mL/kg.

📝 Adjuncts (not first-line in UK/Resus Council guidelines, but often used):
- Hydrocortisone 200 mg IM/slow IV
- Chlorphenamine 10 mg IM/slow IV
- Salbutamol (Albuterol) 5 mg neb if wheeze; escalate if refractory

🔎 About

These reactions resemble acute anaphylaxis but are non–IgE mediated.
Unlike true allergy, risk does not increase with repeat exposure.
Some drugs may be cautiously reintroduced if essential (e.g. acetylcysteine in paracetamol overdose).

🧬 Aetiology (Pathophysiology)

No cross-linking of IgE antibodies on mast cells.
Instead there is direct mast cell degranulation → histamine & mediator release.
This explains why skin, gut, and cardiovascular features look identical to IgE reactions.

💊 Common Causative Agents

Opiates (e.g. morphine)
Aspirin & NSAIDs
Acetylcysteine (Parvolex)
Radiocontrast media (CT, angiography)
Exercise, cold-induced reactions

🩺 Clinical

Indistinguishable from IgE anaphylaxis: urticaria, hypotension, bronchospasm, GI upset.
Key learning point: manage identically in the acute phase.

🔬 Investigations

⬆️ Raised mast cell tryptase (peaks at 1–2 hrs, supports diagnosis).
❌ Negative specific IgE tests (helps differentiate from true allergy).

🛠️ Management

💉 Same acute management as anaphylaxis – adrenaline is first line.
✅ Once stabilised, careful review: drug may be restarted under supervision if essential.
📋 Always document the event and advise patient about future precautions.

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Acute Anaphylactoid Reactions