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Carbon monoxide poisoning - Management
Basis for recommendation
Removal from potential sources of poisoning and establishing a working diagnosis
Admit pregnant women
- Some experts recommend admission for all pregnant women with suspected low level carbon monoxide poisoning for assessment of the fetus [Wolf et al, 2008].
- The fetus is at a relatively greater risk of harm than the mother, because fetal haemoglobin has a higher affinity for carbon monoxide than maternal haemoglobin [HPA, 2007a].
- Maternal symptoms cannot therefore be used to estimate the level of risk to the fetus.
Managing people with suspected lower level poisoning
- CKS found no evidence or published expert opinion relating to the appropriateness of hospital admission or treatment for people with suspected low-level carbon monoxide poisoning.
- CKS recommends managing people with suspected lower level poisoning in primary care based on the following considerations:
- CKS considers it impractical to recommend hospital admission for all people with suspected lower levels of carbon monoxide poisoning, because many common conditions cause non-specific mild symptoms such as headache and nausea.
- People with mild non-specific symptoms are unlikely to have high levels of poisoning from carbon monoxide. The correlation between symptoms and carboxyhaemoglobin levels has been examined by a number of studies of people immediately after exposure to carbon monoxide. A number of reviews of these trials found that people with carboxyhaemoglobin levels of [Varon and Marik, 1997; HPA, 2007a]:
- Less than 10% are likely to be asymptomatic.
- Less than 20% may be associated with equivocal non-specific symptoms such as headache.
- Between 20–30% are likely to have more severe symptoms and signs such as confusion and loss of fine motor control.
- Greater than 30% become breathlessness and may loose consciousness.
- People with lower level carbon monoxide poisoning are likely to be at low risk of harm. This is based on limited evidence from people after lower level acute and long-term exposure sufficient to cause no more than mild non-specific symptoms [Micromedex, 2008; Smollin and Olson, 2008].
- Logically, the benefit of hospital treatment with oxygen is likely to be very limited for people at low risk of harm.
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