Carbon Monoxide Poisoning

Carbon monoxide (CO) is a colourless, odourless gas produced by incomplete combustion. Common sources include furnaces, generators, charcoal grills, vehicle exhaust, and fires. An enclosed-space exposure is particularly concerning because the patient may not recognise the danger before becoming symptomatic. CO binds haemoglobin with an affinity greater than 200 times that of oxygen, forming carboxyhaemoglobin (COHb). This both reduces the blood’s oxygen-carrying capacity and shifts the oxyhaemoglobin dissociation curve to the left, so the oxygen that remains attached to haemoglobin is released less readily. CO also interferes with mitochondrial cytochrome oxidase and triggers inflammatory injury. The result is cellular hypoxia even when the lungs are moving air normally. The first symptoms are often headache, dizziness, weakness, nausea, vomiting, or unusual fatigue. Confusion, ataxia, altered mental status, seizures, loss of consciousness, chest pain, dyspnoea, hypotension, and dysrhythmias indicate more serious poisoning or organ injury. The presentation can resemble influenza or gastroenteritis, but fever and an infectious explanation should not distract from a combustion exposure. A cluster is a major clinical clue. If several people from the same home develop headache or...