What is the treatment for carbon monoxide poisoning?

Treatment of Carbon Monoxide Poisoning

The primary treatment for carbon monoxide poisoning is immediate administration of 100% normobaric oxygen by mask or endotracheal tube, which should be continued until carboxyhemoglobin levels normalize (<3%) and symptoms resolve, typically for about 6 hours. 1

Initial Management

• Administer 100% normobaric oxygen immediately to any person suspected of having CO poisoning while awaiting confirmation of diagnosis 1
• Oxygen accelerates the elimination of carboxyhemoglobin (COHb), reducing its half-life from approximately 320 minutes on room air to about 74 minutes on 100% oxygen 1
• Confirm diagnosis with laboratory measurement of COHb levels, especially for patients being considered for hyperbaric oxygen therapy 1
• Assess for severe metabolic acidosis (pH <7.20) or elevated lactate (≥10 mmol/L) in patients exposed to CO from house fires, as this may indicate concomitant cyanide poisoning requiring specific treatment with hydroxocobalamin 1

Hyperbaric Oxygen Therapy (HBOT) Considerations

HBOT should be considered for patients with:

• Loss of consciousness during or after exposure 1
• Neurological deficits 1
• Ischemic cardiac changes 1
• Significant metabolic acidosis 1
• COHb levels >25% 1
• Pregnancy with any symptoms of CO poisoning 1

The optimal protocol for HBOT remains undefined, but:

• Treatment at 3.0 atmospheres absolute (atm abs) is common practice 1
• Persistently symptomatic patients may benefit from up to three treatments 1
• HBOT should ideally be initiated within 6 hours of exposure for maximum benefit 2
• HBOT reduces COHb elimination half-life to approximately 20 minutes 1

Special Considerations

• For intentional CO poisoning, perform toxicology screening to assess for coingestions, which are present in up to 44% of cases 1
• At minimum, check blood alcohol levels in intentional poisoning cases with disproportionate mental status changes 1
• In patients with CO exposure from house fires, consider empiric treatment for cyanide poisoning if severe metabolic acidosis (pH <7.20) is present 1
• For patients with burns and CO poisoning, the decision for HBOT should be evaluated case-by-case, considering factors such as patient stability, severity of burns, and availability of specialized equipment 1

Follow-up Care

• All patients with accidental CO poisoning should have clinical follow-up 1-2 months after exposure to assess for delayed neurological sequelae 1
• Delayed cognitive impairments may include memory disturbance, depression, anxiety, calculation difficulties, vestibular problems, and motor dysfunction 1
• Patients not recovered to baseline functioning should be referred for formal neuropsychological evaluation 1
• Patients with evidence of cardiac damage should receive appropriate cardiology follow-up 1
• Patients with intentional CO poisoning require mandatory psychiatric follow-up due to high risk of subsequent suicide 1

Common Pitfalls and Caveats

• COHb levels correlate poorly with symptoms or prognosis and may be normal or low if several hours have elapsed since exposure 1, 3
• Do not withhold oxygen therapy while awaiting laboratory confirmation of CO poisoning 1
• Do not withhold HBOT solely because a patient appears to be doing well clinically 1
• Ensure the CO exposure source is identified and eliminated before discharging the patient to prevent re-exposure 1
• Recognize that CO poisoning survivors have increased long-term mortality compared to the general population, suggesting possible residual brain injury 1

The evidence for HBOT remains controversial due to methodological limitations in studies, but current guidelines support its use in selected patients with more severe poisoning to prevent neurocognitive sequelae 1, 2.