Approach
• Early airway assessment, determine need for intubation (AMS)
• 100% O2 or O2 by NRB mask until CO assessed
• Pulse oximetry not useful b/c it will detect carboxyhemoglobin (COHgb) as oxyhemoglobin
History
• Exposure to CO from combustion, faulty heating, closed-space fire, defective automobile exhaust; often multiple people exposed/symptomatic
• Mild poisoning: Frontal HA, N/V, DOE, dizziness/confusion
• Severe exposure: Syncope, coma, or sz
Findings
• Mild confusion progressing to agitation, sz, coma
• May have subtle psychomotor abnormalities: Ataxia, muscle rigidity, tachycardia, hypotension, retinal hemorrhage, ↓ visual acuity, cyanosis, or pallor
• Neurologic findings primarily cerebellar: Dysmetria, ataxia, etc.
Evaluation
• ABG alone not useful b/c pO2, a measure of dissolved oxygen, will be nl; check ABG for COHgb via co-oximetry
• Level is weakly correlated w/ tox but it confirms significant exposure
• Level of <10–15% may be nl in smokers
• Higher risk for myocardial injury: Check ECG esp if baseline CAD, risk fx or high CO
• Assess for suicidal gesture; may need psychiatry consult
Treatment
• Oxygen via NRB (60% oxygen) at least, ideally deliver 100% oxygen
• Airway management: If AMS, hypoxemia or shock → intubate
• Cardiac monitoring; admission if dysrhythmia or e/o ischemia on ECG
• Hyperbaric O2 tx controversial but recommended by Undersea & Hyperbaric Med Society
• Fetal Hgb has higher affinity for CO than adult Hgb; lower threshold for hyperbaric oxygen in pregnant women
Disposition
• Admission based on level & clinical findings; d/c asymptomatic pt w/ HbCO <10%
Pearls
• CO is the most common cause of death from acute poisoning & fires; reversibly binds Hb more avidly than oxygen → functional anemia
• May see delayed neurologic sequelae (personality Δ, HA, sz, parkinsonian changes) 2–40 d after exposure; virtually universally resolve w/i 6 mo
• Half-life of COHgb: 300 min on RA, 90 min on 100% NRB, 30 min hyperbaric
