Carbon monoxide poisoning: Rapid overview of emergency management

To obtain emergency consultation with a medical toxicologist, in the United States, call 1-800-222-1222 for the nearest regional poison control center. Contact information for poison control centers around the world is available at the WHO website and in the UpToDate topic on regional poison control centers (society guideline links).

Initial assessment

Ask about:

Duration and potential sources of exposure, if any other cohabitants or pets not feeling well, and if fire department tested air for presence of CO
Major symptoms: loss of consciousness, syncope, confusion, altered mental status, seizure, focal neurologic deficit, chest pain, dyspnea, respiratory failure, ventricular arrhythmia
Common symptoms: headache, nausea, vomiting, dizziness, weakness, malaise, visual changes, difficulty concentrating

Physical examination focuses on careful evaluation of mental status. The rest of examination is usually normal, but tachycardia and tachypnea can be present. The classic "cherry red" lips are not a sensitive or specific sign.

Initial interventions

Assess and stabilize airway, breathing, and circulation. Intubate as clinically indicated.

If patient appears clinically ill, attach cardiac and oxygen saturation monitors; provide supplemental oxygen as needed to maintain oxygen saturation >90%. Establish IV access.

In patients with suspicion for CO poisoning, apply high-flow oxygen regardless of pulse oximetry or arterial pO2.

Diagnostic evaluation

Check COHb level with co-oximetry of arterial or venous blood. Abnormal COHb is >3% (>10% in smokers).

In patients with any major symptoms, check acid-base status using (preferably arterial) blood gas.

In symptomatic patients, obtain ECG. Measure cardiac biomarkers in patients with significant cardiac risk factors, history of cardiac disease, or ECG evidence of ischemia.

Check urine or serum pregnancy test in female patients of childbearing age.

If the diagnosis of CO poisoning is not confirmed by COHb level, evaluate for other etiologies of symptoms (eg, influenza test, head CT).

Treatment

Direct fire department to assess for environmental exposure and remove victims.

In patients with smoke inhalation who have altered mental status, metabolic acidosis, or hemodynamic instability, we suggest concurrent empiric treatment for cyanide poisoning with hydroxocobalamin.*

We suggest HBO for:

COHb level >25% (>15% if pregnant)
Unconscious at scene or hospital, reported syncope
Persistent altered mental status, coma, focal neurologic deficit
Severe metabolic acidosis (pH <7.25) after empiric cyanide treatment if administered
Evidence of end-organ ischemia (eg, ECG changes, elevated cardiac biomarkers, respiratory failure, focal neurologic deficit, or altered mental status)

Other important considerations:

COHb levels do not always correlate with extent of poisoning, especially if time has passed since exposure and when the level was obtained due to physiologic clearance of CO. Any abnormally elevated COHb level with presence of major symptoms should be considered significant poisoning.
Goal of HBO is not just to increase clearance of CO but to also prevent delayed neuropsychiatric syndrome. HBO may benefit patients even up to 24 hours after exposure.

CO: carbon monoxide; IV: intravenous; pO2: partial pressure of oxygen; COHb: carboxyhemoglobin; ECG: electrocardiogram; CT: computed tomography; HBO: hyperbaric oxygen.

* Refer to UpToDate content on cyanide poisoning.

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Carbon monoxide poisoning: Rapid overview of emergency management