Management overview for carbon monoxide poisoning

Note: Contact a clinical toxicologist or poisons information centre if carbon monoxide poisoning is suspected.

Carbon monoxide is a colourless, odourless gas produced by incomplete combustion of pyrolised material. Carbon monoxide displaces oxygen by binding reversibly to haemoglobin (to produce carboxyhaemoglobin) and other oxygen-carrying protein molecules, such as myoglobin and mitochondrial cytochromes. This reduces oxygen delivery to and uptake by the tissues.

Accidental carbon monoxide poisoning can result from:

  • use of machines or appliances that emit carbon monoxide in enclosed spaces with inadequate or faulty ventilation (eg gas heaters, charcoal burners, petrol or diesel generators or power tools)
  • petrol or diesel motor exhaust fumes (eg boat engines leaking exhaust fumes into cabins; exhaust fumes accumulating in workshops or factories; liquid petroleum gas-driven forklifts)
  • smoke inhalation after exposure to domestic or industrial fires.

Concurrent cyanide poisoning is common in the setting of industrial fires; see here for treatment, if suspected.

Regular cigarette smoking (more than 10 cigarettes per day) can result in a persistently high carboxyhaemoglobin fraction of up to 15%. Recreational hookah pipe (Middle Eastern tobacco-water pipe) smokers can develop an acute rise in their carboxyhaemoglobin fraction to as high as 30%. Although the health effects of a chronically high carboxyhaemoglobin fraction have not been well evaluated, cases of syncope and acute confusional states have been reported after sustained heavy hookah pipe smoking.

Deliberate self-poisoning from carbon monoxide commonly results from channelling motor vehicle exhaust fumes into an enclosed vehicle cabin or garage. Older vehicles without catalytic converters (which remove carbon monoxide from the exhaust gases) pose a greater risk.

An uncommon source of carbon monoxide exposure is ingestion of methylene chloride, a halogenated hydrocarbon metabolised by the liver to carbon monoxide.

If carbon monoxide poisoning is suspected, contact a clinical toxicologist or poisons information centre (13 11 26). The mainstay of management is high-flow oxygen therapy.

The risks of long-term complications in patients with carbon monoxide poisoning are increased by:

  • pre-existing cardiovascular or cerebrovascular disease
  • exposure to carbon monoxide for more than 15 hours
  • sustained loss of consciousness
  • neurological abnormalities after waking from coma.