Which of the following is NOT a symptom of carbon monoxide poisoning?

• A. Abdominal pain
• B. Nausea
• C. Headache
• D. Unconsciousness

Answer: (A)

Carbon monoxide poisoning causes tissue hypoxia because carbon monoxide binds to hemoglobin with a much higher affinity than oxygen, preventing oxygen from reaching the brain, heart, and other organs. This leads to symptoms driven by reduced oxygen delivery. The most common early signs include headache, dizziness, and weakness, with nausea, vomiting, confusion, and shortness of breath appearing as hypoxia progresses. Severe exposure can cause unconsciousness and seizures as the brain and other critical tissues become starved of oxygen. Abdominal pain is not a typical feature of CO poisoning, since the primary effects arise from hypoxic injury to oxygen-dependent tissues rather than acute GI irritation. In suspected cases, remove the person from exposure, call for emergency help, administer 100% oxygen, and consider hyperbaric oxygen if symptoms are severe or there is risk of ongoing hypoxia.