What is the treatment for carbon monoxide (CO) exposure?

Treatment for Carbon Monoxide Poisoning

The first-line treatment for carbon monoxide poisoning is immediate administration of 100% high-flow oxygen via non-rebreather mask or endotracheal tube for intubated patients, with hyperbaric oxygen therapy (HBO₂) considered for severe cases. 1

Initial Management

• Immediate oxygen therapy:

  • Administer 100% normobaric oxygen via non-rebreather mask or endotracheal tube
  • Continue until symptoms resolve (typically for about 6 hours)
  • Oxygen accelerates CO elimination, reducing half-life from ~320 minutes on room air to ~74 minutes 1
  • Target SpO₂ of 94-98% for standard patients; 88-92% for those at risk of hypercapnic respiratory failure

• Assessment and monitoring:

  • Measure carboxyhemoglobin (COHb) levels to confirm exposure (not to guide treatment decisions)
  • Perform arterial blood gas analysis to assess acid-base status
  • Monitor for cardiac involvement with ECG and cardiac enzymes
  • Neurological evaluation including mental status assessment

Hyperbaric Oxygen Therapy (HBO₂)

HBO₂ should be considered for patients with any of the following:

• Loss of consciousness at any point
• Neurological symptoms (confusion, seizures, focal deficits)
• Pregnancy (regardless of symptoms)
• Severe poisoning with persistent symptoms despite normobaric oxygen
• Age ≥36 years with prolonged exposure (≥24 hours) 1

Treatment protocol:

• Initial treatment at 3.0 atmospheres absolute (atm abs)
• Up to three treatments for persistently symptomatic patients 2
• The goal is prevention of long-term neurocognitive dysfunction, not just enhancement of short-term survival 2

Special Considerations

• Intentional CO poisoning:

  • Perform toxicology screening for co-ingestions
  • At minimum, measure blood alcohol level 2
  • Mandatory psychiatric follow-up due to high risk of subsequent suicide

• CO poisoning from house fires:

  • Consider empiric treatment for concomitant cyanide poisoning if:
    • Severe metabolic acidosis (pH < 7.20)
    • Plasma lactate ≥ 10 mmol/L
  • Hydroxocobalamin is the specific antidote with few side effects 2

• Cardiac involvement:

  • Monitor for myocardial injury and transient left ventricular dysfunction
  • Provide supportive care for cardiovascular instability

Follow-Up Care

• Schedule clinical follow-up 1-2 months after exposure for all patients with accidental CO poisoning 2
• Have a family member accompany the patient to provide observations
• Screen for delayed neurological sequelae, which can occur 2-21 days after exposure
• Refer patients not recovered to baseline for formal neuropsychological evaluation
• Refer patients with evidence of cardiac damage for cardiology evaluation

Prevention of Re-Exposure

• Identify and eliminate the CO exposure source before discharge
• Educate patients about CO risks and prevention strategies
• Consider home safety evaluation if exposure occurred in the residence

Common Pitfalls to Avoid

• Do not rely on COHb levels to determine treatment: COHb levels may be low if several hours have elapsed since exposure, and they do not reliably predict clinical outcomes 3
• Do not discharge patients prematurely: Even patients who appear to recover may develop delayed neurological sequelae
• Do not overlook co-exposures: Especially in house fires or intentional poisonings
• Do not miss the diagnosis: CO poisoning presents with non-specific symptoms that can mimic other conditions (headache, nausea, dizziness, confusion)

By following this treatment algorithm and being vigilant for complications, clinicians can significantly improve outcomes for patients with carbon monoxide poisoning.