Suspected nitrous oxide toxicity in emergency departments: Royal College of Emergency Medicine best practice guideline review

Nitrous oxide (N2O) or more commonly known as ‘laughing gas’ is a short-acting anaesthetic agent. It has been used both in medicine and recreationally for over 200 years for its analgesic and antianxiety properties. In the year ending March 2020, use in the last 12 months was reported by 2.4% of adults aged 16–59, and 8.7% of adults aged 16–24. There is inconsistent national data regarding N2O use and reported deaths. However, more recent anecdotal evidence suggests an increase in hospital admissions related to N2O chronic toxicity, although mortality rates are low. A guideline on suspected N2O toxicity in emergency departments (EDs) was produced by the Royal College of Emergency Medicine (RCEM) in April 2023 to promote emergency medicine clinicians to consider N2O toxicity as a differential and how to appropriately investigate this early to support diagnosis. No previous guidelines existed specifically for suspected N2O toxicity in the emergency setting, although N2O use is mentioned in guidelines on sensory neuropathy and anaemia—B12 and folate deficiency.1 ### Remember to consider N2O toxicity as a differential Patients following either long-term high frequency use or short-term high amounts of N2O may consequently present with neurological abnormalities in the form of sensory, motor or coordination deficits, or with haematological abnormalities consistent with pernicious anaemia (box 1). Neurological symptoms are …