Woman’s blood turns navy blue after too much tooth-numbing medication

The woman's bluish-tinged hand, and a sample of blood from her veins. New England Journal of Medicine

A 25-year-old American woman went to the emergency room with discoloured skin — she was literally turning blue.

According to a case report published in the New England Journal of Medicine, the woman had been experiencing weakness, fatigue, shortness of breath and skin discolouration for a day before visiting the emergency room.

“I’m weak and I’m blue,” NBC News reported she told emergency room doctors.

She was also breathing a little fast, and even when given oxygen, the oxygen level in her blood wasn’t improving.

When doctors took blood samples, they discovered something shocking: her blood had turned a dark, inky blue.

Vials of the woman’s arterial and venous blood, both abnormally dark and tinged blue. New England Journal of Medicine

They diagnosed the woman with methemoglobinemia: a condition where the blood contains too much methemoglobin, a form of hemoglobin – the protein that carries oxygen to the body. Methemoglobin isn’t able to release oxygen to the body’s tissues very well, according to a 2001 paper on the condition.

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This lack of oxygen leads to headaches, lethargy, weakness and dizziness, as well as blue skin, according to a review in the Israel Medical Association Journal. The blood of affected patients often appears dark brown, or in this case, blue.

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Some people are genetically predisposed to methemoglobinemia, but most cases are as a result of medication, like some anesthetics.

In this case, the woman had been using “large amounts” of topical benzocaine to treat a toothache the night before developing symptoms.

She was treated — maybe ironically — with a medication called methylene blue and her symptoms resolved completely. She was sent home with a referral to go see a dentist.

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