What is the treatment for carbon monoxide poisoning?

Treatment of Carbon Monoxide Poisoning

Immediate Oxygen Therapy

Administer 100% normobaric oxygen immediately via tight-fitting face mask to any person suspected of CO poisoning, without waiting for laboratory confirmation. 1

• Oxygen accelerates carboxyhemoglobin (COHb) elimination, reducing its half-life from approximately 320 minutes on room air to about 74 minutes on 100% oxygen 1
• Continue oxygen therapy for greater than 6 hours 2
• Hyperbaric oxygen (HBO2) further reduces the elimination half-life to approximately 20 minutes at 2.5-3.0 atmospheres absolute 3, 1

Diagnostic Workup

• Confirm diagnosis with laboratory measurement of COHb levels, particularly for patients being considered for hyperbaric oxygen therapy 1
• Obtain ECG and measure cardiac biomarkers in patients with severe poisoning to assess for myocardial ischemia 4
• Assess for severe metabolic acidosis or elevated lactate in patients exposed to CO from house fires, as this may indicate concomitant cyanide poisoning requiring hydroxocobalamin treatment 1, 5
• For intentional CO poisoning, perform toxicology screening (present in up to 44% of cases) and check blood alcohol levels 1

Important caveat: COHb levels correlate poorly with symptoms or prognosis and may be normal or low if several hours have elapsed since exposure—do not withhold treatment based on low levels 1, 6

Hyperbaric Oxygen Therapy Indications

HBO2 should be administered for the following high-risk presentations: 1

• Loss of consciousness during or after exposure
• Ongoing neurological deficits or altered mental status 3
• Ischemic cardiac changes or evidence of myocardial injury 3
• Significant metabolic acidosis 3
• COHb levels >25% 1
• Any pregnant woman with symptoms of CO poisoning (treating the potentially more severely poisoned fetus) 1

HBO2 Treatment Protocol

• Treat at 3.0 atmospheres absolute for the first treatment 1
• Persistently symptomatic patients may benefit from up to three treatments 1
• Initiate HBO2 within six hours when indicated 4
• Common complications include anxiety and middle ear barotrauma (0-8% of cases), with major complications occurring in only 0.10% of patients 3

Controversial Indications

While evidence remains mixed, consider HBO2 for patients with: 3

• Transient loss of consciousness (even if awake on arrival) 7
• Metabolic acidosis, hypotension, or ataxia 3
• Various treatment algorithms propose COHb thresholds of 15%, 20%, 25%, or 40% regardless of symptoms, though this remains controversial given poor correlation between COHb levels and outcomes 3

Clinical reality: Despite heterogeneous evidence from multiple trials, the decision for HBO2 should prioritize patients with serious intoxication manifestations (unconsciousness, altered neurologic function, cardiac instability) to reduce mortality and prevent delayed neurological sequelae 4, 7

Special Populations

Pregnant Women

• Recommend HBO2 for any symptoms of CO poisoning due to risk of fetal demise, limb and vertebral abnormalities, and brain injury 1
• Maternal COHb levels of 15%, 20%, or 25% have been proposed as thresholds for empiric therapy 3

Patients with Burns

• Evaluate HBO2 case-by-case, considering patient stability, burn severity, and equipment availability 1

High-Risk Patients

• Patients at extremes of age (very young and elderly) warrant more aggressive treatment 7
• Those with pre-existing cardiovascular or pulmonary disease require closer monitoring 7

Follow-Up Care

All patients with accidental CO poisoning require clinical follow-up 1-2 months after exposure to assess for delayed neurological sequelae (DNS). 1

• DNS occurs in 12-68% of cases and may appear after a latent period of 2-40 days 3
• Assess for memory disturbance, depression, anxiety, calculation difficulties, vestibular problems, motor dysfunction, and sleep disorders 1
• Refer patients not recovered to baseline for formal neuropsychological evaluation 1
• Patients with cardiac damage require cardiology follow-up 1
• Mandatory psychiatric follow-up for all intentional CO poisoning cases due to high subsequent suicide risk 1
• Spontaneous recovery from DNS occurs in 75-100% of cases, with most recovering within 1 year 3, 2

Critical Pitfalls to Avoid

• Never withhold oxygen therapy while awaiting laboratory confirmation 1
• Do not withhold HBO2 solely because a patient appears clinically well—patients unconscious at the scene but awake on arrival still warrant HBO2 7
• Ensure the CO exposure source is identified and eliminated before discharge to prevent re-exposure 1
• Do not rely on COHb levels alone to stratify severity or predict prognosis 3, 6
• Recognize that CO poisoning survivors have increased long-term mortality compared to the general population, suggesting possible residual brain injury 1