What are the diagnostic tests and treatment for a patient presenting with possible carbon monoxide (CO) poisoning in the Emergency Department (ED)?

From the Guidelines

For patients presenting with possible carbon monoxide poisoning in the Emergency Department, immediate administration of 100% oxygen via a non-rebreather mask and measurement of carboxyhemoglobin (COHb) levels through arterial or venous blood gas analysis are crucial steps in diagnosis and treatment. The diagnosis of CO poisoning is a clinical one, requiring a history of recent CO exposure, the presence of symptoms consistent with CO poisoning, and demonstration of an elevated carboxyhemoglobin level 1. Normal COHb levels are <3% in non-smokers and <10% in smokers, with levels >10% indicating significant exposure. Pulse oximetry is unreliable for CO poisoning as it cannot distinguish between oxyhemoglobin and carboxyhemoglobin 1.

Diagnostic Approach

• Measure COHb levels through arterial or venous blood gas analysis
• Use laboratory spectrophotometry for accurate measurement, as pulse CO oximetry may not be reliable 1
• Consider the patient's symptoms, such as headache, dizziness, nausea/vomiting, confusion, fatigue, chest pain, shortness of breath, and loss of consciousness, although no single symptom is sensitive or specific for CO poisoning 1

Treatment Approach

• Administer 100% oxygen via a non-rebreather mask to reduce the COHb half-life from 4-6 hours to approximately 60-90 minutes 1
• Consider hyperbaric oxygen therapy (HBOT) for patients with COHb levels >25%, neurological symptoms, cardiac involvement, severe acidosis, pregnancy with COHb >15%, or persistent symptoms despite normobaric oxygen 1
• HBOT typically involves 100% oxygen at 2.5-3 atmospheres for 90-120 minutes
• Supportive care includes cardiac monitoring, IV fluids if needed, and management of any concurrent injuries or complications
• Evaluate all patients for cyanide poisoning if they were in a fire, and consider empiric treatment if severe metabolic acidosis is present 1

Special Considerations

• Patients with intentional CO poisoning should be evaluated for coingestion of other toxins and receive psychiatric follow-up due to the high risk of subsequent completed suicide 1
• Pregnant women and young children are at risk for permanent sequelae of CO poisoning, and adult treatment criteria are generally applied to these patients 1
• Follow-up care is essential, with patients being seen in clinical follow-up 1-2 months after the event to screen for cognitive sequelae 1

From the Research

Diagnostic Tests for Carbon Monoxide Poisoning

• Measurement of carboxyhemoglobin (COHgb) levels is the primary diagnostic test for carbon monoxide poisoning 2, 3, 4
• COHgb levels can be measured directly from blood samples and expressed as a percentage of carboxyhaemoglobin 4
• Clinical signs and symptoms after known exposure to carbon monoxide should not be ignored, even if COHgb levels are not elevated 4

Treatment for Carbon Monoxide Poisoning

• Removal from the source of exposure is the first step in treatment 3, 5
• Immediate administration of 100% supplemental oxygen is recommended 2, 3, 4
• Hyperbaric oxygen therapy (HBO) may be considered for patients with serious intoxication, including those with unconsciousness, altered neurologic function, or cardiac instability 2, 6
• Aggressive supportive measures, such as cardiac and hemodynamic monitoring, may be necessary for patients with severe poisoning 3

Patient Assessment and Management

• Patients at the extremes of age, those with pre-existing cardiovascular and/or pulmonary disease, and pregnant women are at increased risk for carbon monoxide poisoning 2
• Any patient who has suffered an interval of unconsciousness, regardless of their clinical exam on arrival, warrants HBO therapy 2
• Treatment plans should be individualized and based on the patient's clinical presentation, rather than solely on COHgb levels 2