Nitrous oxide (N2O) should not be given continuously for longer than 24 hours or more frequently than every 4 days without close supervision and haematological monitoring.
- Check BNF or equivalent for UpToDate prescribing advice
- Nitrous oxide is a colourless gas used medically with analgesic and anaesthetic properties
- Used commercially in the catering industry to produce foamed cream.
- Treat by cessation of nitrous oxide use and high dose IM vitamin B12 supplementation.
Mode of action
- Nitrous oxide is a NMDA receptor antagonist
- It irreversibly binds and inactivates vitamin B12 and causes B12 deficiency-related haematological and neurological syndromes
- Anaesthesia in conjunction with other anaesthetic agents: inhalation: Nitrous Oxide 50-66 %, to be administered using suitable anaesthetic apparatus in oxygen.
- Analgesia: inhalation Nitrous oxide Up to 50 % administered using suitable anaesthetic apparatus in oxygen, adjusted according to the patient's needs.
- Must be given or under the direct supervision of, personnel experienced in its use, with adequate training in anaesthesia and airway management, and when resuscitation equipment is available
Abuse and Toxicity
- Nitrous oxide is used recreationally - Available in nightclubs at low cost
- taken as ‘whippits’ (aerosol chargers used in canisters of whipped cream, each containing 8 g of nitrous oxide from which it is discharged into a balloon and then inhaled.
- The toxic effects are mediated through oxidation of cobalt ions in vitamin B12 and hence cause its inactivation.
- Death has also been reported, with evidence suggesting N2O impairs physiological responses to rising hypoxia and hypercapnia
- Intracranial air
- Abdominal distension, Euphoria, Nausea
- Chronic use : Megaloblastic anaemia due to B12 deficiency
- Subacute combined degeneration from B112 deficiency
- Low WCC, Low granulocytes, dizziness
Management of abuse
- High-dose intramuscular B12 replacement is recommended
- Methylmalonic acid and homocysteine concentrations return rapidly to normal
- Recovery from nitrous oxide neuropathy may be slow and incomplete even with high-dose vitamin B12 replacement