Fire/smoke, headache, confusion; normal PaO₂, ↑COHb
ABCDE
Remove from source; 100% O₂; ECG/troponin; hyperbaric for severe/pregnant.
Immediately: 100% oxygen (halves COHb in 60–90 min) + measure carboxyhemoglobin
Hyperbaric O₂ if: LOC, pregnancy, severe (COHb halved in 20–30 min)
Order set
- 100% O₂
- Carboxyhaemoglobin (co-oximetry)
- ECG, troponin
- VBG (pulse oximetry unreliable)
Criteria
AdmitSymptomatic / high COHb
ICU↓GCS, cardiac ischaemia
DischargeCOHb normal, symptoms resolved, delayed-sequelae advice
Clinical detail — differentials, red flags, pitfalls, disposition
Red flags
- LOC/neuro signs
- Cardiac ischaemia
- Pregnancy
Differentials
- Cyanide co-exposure
- Other causes of headache/collapse
Common mistakes
- Trusting pulse oximetry (pulse CO-oximetry/SpCO can screen, but co-oximetry ABG/VBG is definitive)
- Missing delayed neuro sequelae
- Missing cyanide co-exposure in smoke inhalation — treat empirically (hydroxocobalamin) if soot in airway + lactate >8–10
Disposition & follow-up
O₂ until COHb normal; hyperbaric for severe/pregnant.
Discharge package
Medications—
Follow-upFollow-up for delayed neuro sequelae; source (alarm/appliance check)
LifestyleInstall CO alarm; service appliances
Warning symptomsHeadache, confusion, memory problems
💊 Treatment detail — doses & preparation
100% Oxygendefinitive
DoseHigh-flow non-rebreather mask until COHb <5% and asymptomatic (half-life 80 min vs 320 on air)
PreparationNon-rebreather at 15 L/min
MonitorABG COHb serial; HBO if pregnant/neuro signs/COHb very high
📖 UHMS / poisons-centre guidanceReviewed July 2026