NCLEX Review Guide: Carbon Monoxide Poisoning

Understanding Carbon Monoxide Poisoning

• Carbon monoxide (CO) is a colorless, odorless gas that binds to hemoglobin with 200 times greater affinity than oxygen, forming carboxyhemoglobin (COHb).
• This binding prevents oxygen transport and delivery to tissues, leading to cellular hypoxia and metabolic acidosis.
• Common sources include faulty heating systems, car exhaust, improperly ventilated appliances, and house fires.

Clinical Manifestations

• Early signs: Headache, dizziness, nausea, vomiting, and fatigue - often mistaken for flu-like symptoms.
• Late signs: Confusion, altered mental status, seizures, coma, and cardiac arrhythmias.
• Cherry-red skin color is a classic but late sign seen in severe poisoning or death.
• Pulse oximetry readings appear falsely normal because the device cannot distinguish between oxyhemoglobin and carboxyhemoglobin.

Immediate Interventions

1. Remove patient from CO source immediately and ensure scene safety for healthcare providers.
2. Administer 100% oxygen via non-rebreather mask to accelerate CO elimination from hemoglobin.
3. Obtain arterial blood gas with CO-oximetry to measure actual carboxyhemoglobin levels.
4. Monitor vital signs, neurological status, and cardiac rhythm continuously.
5. Prepare for hyperbaric oxygen therapy if COHb levels >25% or neurological symptoms present.

Ongoing Care

• Continue oxygen therapy until COHb levels drop below 5% and symptoms resolve completely.
• Monitor for delayed neurological sequelae including memory loss, personality changes, and movement disorders.
• Assess for concurrent injuries from potential loss of consciousness or altered mental status.
• Provide emotional support as patients may experience anxiety about the poisoning incident.

High-Yield Facts

• Always suspect CO poisoning when multiple family members present with similar flu-like symptoms, especially in winter months.
• The half-life of CO in room air is 4-6 hours, but reduces to 1 hour with 100% oxygen therapy.
• Hyperbaric oxygen therapy further reduces half-life to 20-30 minutes and is indicated for severe cases.
• Prevention education includes proper ventilation, CO detectors, and annual appliance inspections.

Self-Assessment

• ☐ I can identify the pathophysiology of CO poisoning and why pulse oximetry is unreliable
• ☐ I understand the priority nursing interventions for CO poisoning
• ☐ I can differentiate CO poisoning from other types of poisoning
• ☐ I know the indications for hyperbaric oxygen therapy
• ☐ I can recognize high-risk populations and prevention strategies