Carbon Monoxide

Carbon monoxide is a toxic gas that has high affinity for haemoglobin, displacing oxygen from haemoglobin binding sites resulting in a significant fall in blood oxygen carrying capacity and cellular hypoxia.

Carbon monoxide is also:

  • Odourless
  • Colourless
  • Less dense than air
  • Flammable

Epidemiology and Risk Factors

Pathophysiology

Carbon monoxide:

  • Has 240 times the affinity for haemoglobin than oxygen
  • Has a half-life of ~320 minutes breathing air
    • ↓ To 75 minutes on 100% O2

Aetiology

Clinical Manifestations

Symptoms vary with the proportion of COHb:

Smokers may have a COHb level up to 10%.

  • Mild (10-25%)
    • Weakness
    • Dizziness
    • Confusion
  • Moderate (25-40%)
    • Nausea
    • Arrhythmia
  • Severe (>40%)
    • Coma → Seizure

Cyanosis is much more common than “cherry-pink” skin.

Diagnostic Approach and DDx

Investigations

Bedside:

  • ECG
    • ST segment changes

Laboratory:

Imaging:

Other:

Management

Resuscitation:

  • A
    • Intubation indicated if no longer protecting airway
  • B
    • Supplemental oxygen

Specific therapy:

  • Pharmacological
  • Procedural
  • Physical
    • Hyperbaric oxygen
      Often used though no strong evidence of benefit.

Supportive care:

Disposition:

Preventative:

Marginal and Ineffective Therapies

Anaesthetic Considerations

Complications

Prognosis

Key Studies

References

  1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.