Carbon Monoxide Poisoning

KEY FEATURES

• Poisoning may occur as a result of suicidal or accidental exposure to automobile exhaust, smoke inhalation in a fire, or accidental exposure to an improperly vented gas heater, generator, or other appliance

• Carbon monoxide can be generated during degradation of some anesthetic gases by carbon dioxide adsorbents

• 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

• A fetus and newborn may be more susceptible because of high carbon monoxide affinity for fetal hemoglobin

DIAGNOSIS

• 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

• Some specialized pulse oximetry devices are capable of distinguishing oxyhemoglobin from carboxyhemoglobin

TREATMENT

• Emergency and supportive measures

  • Remove patient from exposure

  • Maintain a patent airway and assist ventilation

• Specific treatment

  • 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