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For further information, see CMDT Part 38-26: Carbon Monoxide Poisoning

Key Features

  • Avidly binds to hemoglobin, which results in reduced oxygen-carrying capacity and altered delivery of oxygen to cells

Clinical Findings

  • At low carbon monoxide levels (carboxyhemoglobin [COHb] 10–20%)

    • Headache

    • Dizziness

    • Abdominal pain

    • Nausea

  • With somewhat higher levels (COHb 20–50%)

    • Confusion

    • Dyspnea

    • Syncope

  • With high levels (COHb > 50–60%)

    • Hypotension

    • Coma

    • Seizures

  • Permanent neurologic or neuropsychiatric deficits may develop in survivors of acute severe poisoning


  • Suspect in the setting of severe headache or acutely altered mental status

  • Diagnosis depends on

    • Specific measurement of the arterial or venous COHb saturation

    • However, the level may have declined if high-flow oxygen therapy has already been given

    • COHb levels do not always correlate well with clinical findings

  • Routine arterial blood gas testing and pulse oximetry are not useful because they may give falsely normal PaO2 or oxygen saturation levels


  • Remove victim from exposure

  • Administer 100% oxygen by tight-fitting high-flow reservoir face mask or endotracheal tube

  • Hyperbaric oxygen (HBO)

    • Can provide 100% oxygen in higher than atmospheric pressures, further shortening the half-life

    • May also reduce incidence of subtle neuropsychiatric sequelae

  • Indications for HBO treatment after acute carbon monoxide exposure

    • Loss of consciousness

    • Metabolic acidosis

    • COHb > 25%

    • Age > 50 years

    • Cerebellar findings on neurologic examination

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