A Successful Case of an Acquired Methemoglobinemia Treated with Methylene Blue

Abstract

Methylene blue has been advocated for multiple indications, but data reporting its use on intoxication is rare. Acquired methemoglobinemia can be caused by a wide variety of chemicals and toxins and on severe cases, with high methemoglobin levels (>20%), methylene blue is the first line treatment. We describe a case report of a 45-year-old man with acute methemoglobinemia due to involuntary exposure to n-propyl nitrate. The patient came into the emergency department conscious, with profound peripheral and central cyanosis and oxygen saturation of 88% on air, with no response to oxygen supplementation. Arterial blood gas showed methemoglobin of 22.9%. Methylene blue was administered intravenously and symptoms improved dramatically, with control arterial blood gas with 2.6% of methemoglobin. Despite the rarity of occurrence of methemoglobinemia in occupational set, and since methylene blue is highly effective, a high degree of suspicious and good training aiming for prompt diagnosis is crucial in treating this emergency situation.