See also:

Recreational drug use and overdose
Poisoning - acute guidelines for initial management
Resuscitation

Key points

1. Chronic high-level recreational N₂O exposure impedes vitamin B12 function, leading to neurological dysfunction and rarely myelosuppression
2. Patients often present with symptoms and signs consistent with subacute combined degeneration of the spinal cord
3. Measured vitamin B12 may be normal and does not reflect ‘functional vitamin B12’ concentration
4. Discontinuation of N₂O and administration of intramuscular vitamin B12 and oral methionine are the mainstays of management

For 24 hour advice, contact the Poisons Information Centre 13 11 26

Background

• N₂O is a short-acting anaesthetic agent, also used as an aerosol spray propellant in food preparation (eg cream ‘chargers’ or cannisters for manufacturing whipped cream)
• Deliberate inhalation of N₂O bulbs (‘nangs’) for recreational purposes is known as ‘nanging’
• Acute exposure results in short-lived and reversible CNS effects including euphoria and sedation
• Chronic N₂O exposure results in dose-dependent inactivation of vitamin B12, which is a co-factor required for methionine synthesis. Methionine is required for DNA synthesis and maintenance of nervous system myelin sheaths
• Loss of methionine leads to demyelination in the peripheral and/or central nervous system and bone marrow suppression
• User surveys suggest the likelihood of reporting paraesthesia varies from 1-4% in individuals who regularly (at least weekly) use 1-2 N₂O bulbs per session. This increases to 16% in users reporting exposure to 100 or more N₂O bulbs per session.

Children requiring assessment

• All children with deliberate self-poisoning
• Any child with neurological symptoms and a history of N₂O misuse

Risk Assessment

History

Assessment in relation to chronic use

Presentations due to acute toxicity are rare, but may include short-lived confusion, hallucinations or falls as a result of temporary ataxia. Pneumothorax may rarely occur as the result of forceful inhalation

• History of recreational misuse of N₂O
  • Higher doses, and chronic use are more likely to produce toxicity.
  • Regular daily misuse or misuse of greater than 100 bulbs per session, are often reported in cases where there is clinical evidence of neurological dysfunction
• Progressive onset of symptoms (over days or weeks)
• Altered sensation
• Muscle weakness
• Gait disturbance
• Rarely: depression, irritability, personality change

Examination

• Sensory deficits, may be dermatomal but can be patchy (akin to findings in multiple sclerosis)
• Impaired proprioception and coordination (affects dorsal columns first)
• Sensory ataxia
• Reduced power in limbs
• Reduced reflexes

Investigations

Pathology

• FBE and blood film for macrocytic anaemia or other evidence of bone marrow suppression
• Total vitamin B12 and active vitamin B12 (holotranscobalamin) concentrations may be low or undetectable and methylmalonic acid concentration is usually raised.
• Vitamin B12 and methionine treatment should not be withheld if concentrations are normal in patients with clinical signs of toxicity and a history of N₂O misuse

MRI Brain and/or Spine may demonstrate demyelination

Nerve conduction studies may demonstrate impaired signal transmission

Management

Consult with Toxicology via the Victorian Poisons Information Centre (13 11 26)

Treatment

Admission to hospital is required if a patient is unable to walk independently or has evidence of haematological or psychiatric sequelae

• Administer 1 mg vitamin B12 IM daily for 2 weeks, weekly for 4 weeks and monthly until maximal recovery
  • High doses of vitamin B12 via intra-muscular injection weekly leads to swifter resolution of toxicity and may improve recovery
• Administer 1 g methionine oral TDS for 2 weeks
• Consult with haematology service if evidence of bone marrow suppression
• Consider the presence of other nutritional deficiencies due to poor intake

Consider consultation with local paediatric team when

• Any child or adolescent presents with intentional overdose as admission should be considered
• Advice required regarding escalation of care

Consider transfer when

Children require care beyond the comfort level of the current hospital  

For emergency advice and paediatric or neonatal ICU transfers, see Retrieval Services.

Consider discharge when

• Patient is able to walk safely and independently
• Improvement in haematological dysfunction (if present)
• Safe for discharge from a mental health perspective, with appropriate referrals to alcohol and drug services made where relevant
• Education has been provided regarding the dangers of N₂O misuse

Assessing risk and connecting to community services

• Prior to discharge, adolescents who present with deliberate ingestions need a risk assessment regarding the likelihood of further ingestions or other attempts to self-harm
• Assessment of other drug and alcohol use should also be undertaken
• If, after risk assessment, it is deemed safe to discharge a patient from hospital, but ongoing mental health or drug and alcohol needs are identified, the adolescent should be linked with appropriate services (see links below for services in the State of Victoria)  

Discharge information and follow-up:

Parent Information: Poisoning prevention for children
Prevention of poisoning (Victorian Poisons Information Centre)

Poisons Information Centre: phone 13 11 26

Victoria
Poisons Information Centre
Child & Adolescent Mental Health Services (CAMHS): Victorian government mental health services are region-based
Orygen Youth Health: Specialist mental health services for people aged 15 – 25 years, residing in the western and north-western regions of metropolitan Melbourne. Triage/intake - 1800 888 320.
Headspace: National Youth Mental Health Foundation with local headspace centres
YSAS (Youth Support and Advocacy Service): Outreach teams across Melbourne and regional Victoria for young people experiencing significant problems with alcohol and/or drug use
YoDAA: Victoria’s Youth Drug and Alcohol Advice service - provides information and support for youth AOD needs or anyone concerned about a young person
Infoxchange Service Seeker: Search for local community support services eg local doctor, dentist, counselling services, drug and alcohol services.

Last updated February 2021