Investigations

In addition to clinical assessment, some specific and non-specific investigations should be considered in symptomatic patients:

  • Measure COHb – arterial or venous (caution should be taken in interpreting the results after the administration of therapeutic oxygen)
  • Blood glucose to exclude hypoglycaemia
  • FBC, U&E, CK, Trop and ABGs
  • Lactate (also in the context of combustion, a high lactate (>10 mmol/L) may suggest concurrent cyanide exposure)
  • 12 lead ECG

For low level and chronic exposures, it is unlikely that a confirmatory level of COHb will be found.

Some responders may have access to exhaled breath CO monitoring, although this assessment has not been validated.

Indications of severity

Indications of severity include one or more of the following:

  • Any new objective acute neurological signs e.g increased tone, upgoing plantars, coma
  • Need for ventilation
  • ECG indication of infarction or ischaemia
  • Clinically significant acidosis
  • Initial carboxyhaemoglobin greater than 30%

Learning bite

The COHb for patients with mild or chronic exposure, or who have been treated with high flow oxygen may be normal.

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