Carbon monoxide
Incidents of carbon monoxide poisoning are particularly concerning. They are a major cause of preventable deaths and may involve multiple exposures and be under-diagnosed, due to non-specific symptoms.
During 2010/11, there were 286 telephone enquiries (290 in 2009/10) made to NPIS regarding confirmed or suspected carbon monoxide exposures. In 38 enquiries multiple individuals were involved, so that the total number of patients was at least 385 (in some cases the number of individuals exposed was not known). The maximum number of individuals exposed in a single incident was 12 and involved the smoking of a 'water pipe' in a poorly ventilated bar.
Most enquiries (242 of 286 or 85%) during 2010/11 involved carbon monoxide exposure at home, compared to just 6% occurring in the workplace and 4% reported in a public area. The suspected source of carbon monoxide in the domestic setting is known in 71% of cases; central heating boilers were implicated most often.
Of the 286 enquiries, 251 were reported to be accidental, 19 were deemed intentional and, in the remaining 16, the intention was uncertain but was probably accidental in ten. Of the 251 accidental exposures, 225 had a poisoning severity score of 0 or 1 (minor toxicity) at the time of the enquiry, 12 had features of moderate toxicity (PSS 2), and seven were graded PSS 3 indicating features of severe poisoning; a PSS was unavailable in the remaining seven enquiries. Six out of seven severe cases involved patients who had been exposed to carbon monoxide through smoke inhalation during a domestic fire, so factors such as thermal injury may also have contributed to their features. Carboxyhaemoglobin concentrations in these patients ranged from 11–48%. Follow-up was attempted in all cases: one patient recovered completely and two died; in four cases either no or insufficient follow-up data were available.
Of the 19 intentional exposures, 13 involved attempts at suicide using vehicle exhaust fumes, three were attempted suicides which involved the lighting of a barbecue in a confined space, and two involved house fires. The carboxyhaemoglobin concentrations at presentation were known in 13 of 19 cases and ranged from 4.8% to 39.9%, with values of 30% or higher in four cases.
In two further cases involving victims of house fires, the circumstances of exposure were classified as ‘unknown’ but it was considered possible that the fires had been started deliberately. In both these cases, cyanide poisoning was also a factor and most probably contributed to the severity of the cases.
Information from the NPIS Annual Report 2010/11
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