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It’s a busy Friday on a typical Portland rainy, cold and blustery day and the MA tells you your next patient is a 29-year-old pregnant woman who is here with headache, nausea and lightheadedness she experienced for a few days. She tells you

she is 16 weeks pregnant and that the pregnancy has been going well with no complications. She reports that over the past few days everyone in the house has been “under the weather “and she thought it was just a “cold going around”, but today she had a throbbing headache and felt sort of nauseous, light-headed and a little dizzy so she came in to get checked out. No fever, no vomiting no pelvic or abdominal pain, no spotting or cramping. Her exam and vitals are all normal. UA normal. She appears well now and reports that she actually feels much better now than she did a few hours ago. You ask about how they are keeping warm in the house. She reports that they have been using a space heater for the past few days to keep warm during the cold spell. During the winter season carbon monoxide (CO) poisoning can be confused with flu symptoms, food poisoning and other illnesses. Headache is an early symptom of CO poisoning, occurring at carboxyhemoglobin (COHb) levels of around 10%. Severe symptoms include shortness of breath, nausea, dizziness, chest pain, confusion, syncope and cardiac arrest. High levels of CO can be fatal, causing death within minutes. Patients with pre-existing cardio-pulmonary disease, infants, children and pregnant women are at greatest risk. Most carbon monoxide exposures happen in the winter and it is one of the most common causes of accidental poisoning. The most common household source is unvented or improperly vented space heaters that release the odorless, colorless and tasteless gas into the house. Multiple family members with symptoms or symptoms that improve when the patient leaves the house should prompt you to consider this diagnosis. Other common sources of exposure include: 

•Furnaces or boilers

•Gas stoves and ovens

•Fireplaces, both gas and wood burning

•Water heaters

•Clothes dryers

•Wood stoves

•Power generators

•Motor vehicles

•Power tools and lawn equipment

•Tobacco smoke

•Suicide attempt (intentional exposure)

So back to your patient. You suspect CO exposure and place her on 100% oxygen while you discuss the need for ED evaluation for rapid determination of a blood COHb level. Treatment of CO poisoning begins with inhalation of supplemental oxygen and aggressive supportive care. Hyperbaric oxygen therapy (HBOT) accelerates disassociation of CO from hemoglobin and may prevent delayed neurological complications. Absolute indications for HBOT for CO poisoning remain controversial, although most would agree that HBOT is indicated in patients who are comatose, are neurologically abnormal, have a history of loss of consciousness with their exposure, or have cardiac dysfunction. Pregnancy with an elevated COHb level (>15-20%) also is widely considered an indication for treatment.


Photo provided by By Santeri Viinamäki, CC BY-SA 4.0,


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