Management of Carbon Monoxide Poisoning
The front-line treatment for all cases of carbon monoxide poisoning is immediate administration of 100% normobaric oxygen by mask or endotracheal tube while awaiting confirmation of diagnosis. 1, 2
Initial Management
- Administer 100% normobaric oxygen immediately to any person suspected of having CO poisoning while awaiting confirmation of diagnosis 1
- Confirm diagnosis with laboratory measurement of carboxyhemoglobin (COHb) levels, especially for patients being considered for hyperbaric oxygen therapy 1
- Continue 100% normobaric oxygen until COHb is normal (<3%) and the patient's presenting symptoms have resolved, typically for about 6 hours 1
- Oxygen accelerates the elimination of COHb, reducing its half-life from approximately 320 minutes on room air to about 74 minutes on 100% oxygen 1, 2
- Identify and eliminate the CO exposure source before discharging the patient to prevent re-exposure 1, 2
Hyperbaric Oxygen Therapy (HBOT) Considerations
Consider HBOT for patients with any of the following 1, 2:
- Loss of consciousness during or after exposure
- Neurological deficits
- Ischemic cardiac changes
- Significant metabolic acidosis
- COHb levels >25%
- Pregnancy with any symptoms of CO poisoning
HBOT reduces COHb elimination half-life to approximately 20 minutes 1
Treatment at 3.0 atmospheres absolute (atm abs) is common practice, and persistently symptomatic patients may benefit from up to three treatments 2, 3
The most recent high-quality study showed that three hyperbaric-oxygen treatments within a 24-hour period reduced the risk of cognitive sequelae at 6 weeks (25% vs. 46.1%, p=0.007) and 12 months after acute CO poisoning 3
Special Considerations
- For CO exposure from house fires, assess for severe metabolic acidosis or elevated lactate, which may indicate concomitant cyanide poisoning requiring specific treatment 1, 2
- For intentional CO poisoning, perform toxicology screening to assess for coingestions, which are present in up to 44% of cases 2
- COHb levels correlate poorly with symptoms or prognosis and may be normal or low if several hours have elapsed since exposure 1, 2, 4
- Do not withhold oxygen therapy while awaiting laboratory confirmation of CO poisoning 1, 2
Follow-up Care
- All patients with accidental CO poisoning should have clinical follow-up 4-6 weeks after exposure to assess for delayed neurological sequelae 1, 2
- Patients with intentional CO poisoning require mandatory psychiatric follow-up due to high risk of subsequent suicide 1, 2
- Patients not recovered to baseline functioning should be referred for formal neuropsychological evaluation 2
- Patients with evidence of cardiac damage should receive appropriate cardiology follow-up 2
Common Pitfalls and Caveats
- Increasing alveolar ventilation by adding CO2 to O2 is unreliable and risky as it may exacerbate acidosis in patients with ventilatory depression 1
- Do not withhold HBOT solely because a patient appears to be doing well clinically, as delayed neurological sequelae can occur 2, 4
- Recognize that CO poisoning survivors have increased long-term mortality compared to the general population 1, 2
- The cherry red skin discoloration classically associated with CO poisoning is rarely observed in clinical practice 1