Makindo Medical Notes

⚠️ Safety: Nitrous oxide (N₂O) should not be given continuously for >24 hours ⏱️ or more frequently than every 4 days without close supervision and haematological monitoring. ❌ Chronic exposure can cause profound vitamin B12 inactivation → neurological 🧠 and haematological 🩸 injury.

📘 About

• 🌫️ Colourless gas with analgesic and anaesthetic properties.
• 🩺 Commonly used in medical anaesthesia and emergency analgesia (e.g. “entonox” mix).
• 🍰 Commercial catering use (whipped cream canisters).
• 💉 Toxicity treated with cessation + high-dose intramuscular vitamin B12 replacement.

⚙️ Mode of Action

• Acts as an NMDA receptor antagonist → analgesic effect.
• ⚡ Oxidises cobalt in vitamin B12, irreversibly inactivating it → impaired DNA synthesis 📖 and myelin formation 🧠 → haematological & neurological syndromes.

💊 Indications / Dose

• 😷 Anaesthesia: 50–66% inhaled with oxygen via anaesthetic apparatus.
• 🤰 Analgesia: Up to 50% inhaled with oxygen, titrated to need (e.g. labour, trauma care 🚑).

🔄 Interactions

• See BNF.

⚠️ Cautions

• 👩‍⚕️ Must only be given by trained staff with airway skills + full resuscitation equipment.
• 📆 Prolonged/repeated exposure → ↑ risk of B12 deficiency & neurotoxicity.

🚫 Abuse & Toxicity

• 🎈 Recreational use as “whippits” (balloons, ~8 g canisters).
• 🔬 Mechanism: Vitamin B12 inactivation (cobalt oxidation).
• 🧠 Neurological: peripheral neuropathy, subacute combined degeneration of cord.
• 🩸 Haematological: megaloblastic anaemia, low WCC, low granulocytes.
• 💀 Severe: impaired hypoxia/hypercapnia response → collapse & death reported.

🚫 Contraindications

• 🫁 Pneumothorax.
• 🧠 Intracranial or intraocular air.
• 🫧 Air embolism or severe bowel distension.

💥 Side Effects

• 🔹 Acute: euphoria 😊, abdominal distension 🤢, dizziness, nausea.
• 🔹 Chronic: megaloblastic anaemia 🩸, neuropathy 🧠, psychiatric disturbance 🌀.

🛠️ Management of Abuse

• ⛔ Stop nitrous oxide use.
• 💉 High-dose IM hydroxocobalamin (vitamin B12).
• 🧪 Monitor methylmalonic acid & homocysteine (normalise rapidly after treatment).
• ♻️ Neurological recovery can be slow, sometimes incomplete despite B12 therapy.

📖 References

• Whippits, nitrous oxide and the dangers of legal highs – BMJ Practical Neurology