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

Treatment for Carbon Monoxide (CO) Poisoning

The treatment for carbon monoxide poisoning is immediate administration of 100% high-flow oxygen therapy for all patients, with hyperbaric oxygen therapy (HBO₂) considered for severe cases involving loss of consciousness, neurological symptoms, pregnancy, or persistent symptoms despite normobaric oxygen. 1, 2

Initial Management

Oxygen Therapy

• First-line treatment: 100% normobaric oxygen via non-rebreather mask or endotracheal tube for intubated patients 1, 2
• Continue oxygen therapy until:
  • Carboxyhemoglobin (COHb) levels normalize (<3%)
  • Presenting symptoms resolve
  • Typically for about 6 hours 1
• Oxygen accelerates CO elimination:
  • Half-life on room air: ~320 minutes
  • Half-life on 100% oxygen: ~74 minutes 1

Clinical Assessment

• Focus on clinical assessment rather than serial COHb measurements 2
• Monitor for resolution of symptoms:
  • Headache, dizziness, nausea, confusion
  • Neurological status throughout treatment 2

Hyperbaric Oxygen Therapy (HBO₂)

Indications for HBO₂

Consider HBO₂ for patients with:

• Loss of consciousness at any point
• Neurological symptoms
• Pregnancy
• Severe poisoning
• Persistent symptoms despite normobaric oxygen 1, 2

Evidence for HBO₂

The evidence for HBO₂ remains controversial 1:

• Several studies have shown conflicting results (see Table 1 in 1)
• The most rigorous study by Weaver et al. (2002) showed reduced cognitive sequelae (25% vs. 46%) at 6 weeks with HBO₂ compared to normobaric oxygen 1
• The European Committee of Hyperbaric Medicine (ECHM) strongly recommends HBO₂ for high-risk patients regardless of COHb level 1
• American College of Emergency Physicians notes ongoing controversy 1

HBO₂ Protocol

• Optimal dose and frequency remain unknown 1
• Common practice:
  • Initial treatment at 3.0 atmospheres absolute (atm abs)
  • Up to three treatments for persistently symptomatic patients 1

Special Considerations

Co-exposures

• For intentional poisonings, consider toxicology screening for co-ingestions (44% of intentional cases) 1
• For CO poisoning from house fires with severe metabolic acidosis (pH <7.20):
  • Consider empiric treatment for concomitant cyanide poisoning
  • Consider hydroxocobalamin if plasma lactate ≥10 mmol/L 1

High-Risk Patients

• Pregnant women (HBO₂ recommended regardless of symptoms) 1
• Children with impaired consciousness or neurological symptoms 1
• Patients with pre-existing cardiovascular or pulmonary disease 2

Follow-up Care

Short-term Follow-up

• All patients with accidental CO poisoning should be seen 1-2 months after exposure 1, 2
• Screen for delayed neurological sequelae, which can occur 2-21 days after exposure 1, 2
• Family member should accompany patient to provide observations 1

Long-term Considerations

• Patients not recovered to baseline should be referred for formal neuropsychological evaluation 1
• Patients with cardiac damage should receive cardiology evaluation 1
• Patients with intentional CO poisoning require mandatory psychiatric follow-up due to high risk of subsequent suicide 1

Prevention of Re-exposure

• Critical to identify and eliminate the CO source before discharge 2
• Educate patients about CO risks and prevention measures 2

Pitfalls to Avoid

• Don't rely solely on COHb levels to determine treatment duration or severity
• Don't discharge patients without ensuring their home environment is safe
• Don't overlook the possibility of delayed neurological sequelae even in initially well-appearing patients
• Don't forget to consider co-exposures, especially in house fires (cyanide) and intentional poisonings

The evidence strongly supports immediate administration of 100% oxygen for all CO poisoning cases, with consideration of HBO₂ for severe cases based on clinical presentation rather than COHb levels alone.