A Real Pain in the Mouth: Acquired Methemoglobinemia

For patients presenting with hypoxia and cyanosis, acquired methemoglobinemia should be included on the differential. Dapsone and topical anesthetics are common offenders in methemoglobinemia, so a thorough medication history is pertinent to diagnosing and treating this condition.

 Methemoglobinemia

Methylene Blue - Give 1-2 mg/kg IV over 5 minutes. Clinical improvement should occur within minutes. However, methylene blue may cause transient drops in the measured oxygen saturation (due to its blue pigment). Cyanosis should resolve within an hour.

A Rare Culprit of Methemoglobinemia

While methemoglobinemia may be inherited, its acquired form occurs when hemoglobin is exposed to oxidizing agents and is far more prevalent. Nitrate-containing compounds have been classically described as causing methemoglobinemia, ranging from aniline dyes and pesticides to medications, such as nitroglycerin, nitroprussides, and silver nitrite.1,2 Other commonly used drugs include sulfonamides, dapsone, and benzocaine—the latter 2 accounting for up to 45% of all drug-induced methemoglobinemia cases.

Acquired methemoglobinemia in infants

Methemoglobinemia is an uncommon cause of cyanosis. It should be suspected in an infant with cyanosis who has no respiratory distress or cyanotic congenital heart disease.

Blue babies and nitrate-contaminated well water

The use of nitrate-contaminated drinking water to prepare infant formula is a well-known risk factor for infant methemoglobinemia. Affected infants develop a peculiar blue-gray skin color and may become irritable or lethargic, depending on the severity of their condition.

Code Blue: Life-threatening Methemoglobinemia

Methemoglobinemia should be suspected in all patients with sudden onset of cyanosis that does not improve with the administration of oxygen. Prompt administration of methylene blue should be the first-line treatment. Ascorbic acid can be used as adjuvant therapy when there is a contraindication to methylene blue, or when methylene blue is not available.

Homemade Baby Food: The Danger of Nitrates

Nitrates aren’t the only cause of methemoglobinemia. Certain antibiotics and the numbing agent found in teething gels can also convert hemoglobin to methemoglobin. And baby food isn’t the only dietary source of nitrates. Drinking water (especially well water) can contain high levels of nitrates from fertilizer run-off. In fact, the most common cause of methemoglobinemia in babies (including those older than 6 months of age) is the ingestion of infant formula made with nitrate-containing well water!

How to recognize and treat acquired methemoglobinemia

Pulse oximetry is inaccurate in the presence of significant methemoglobinemia and cannot be relied on.

Infant Methemoglobinemia (Blue Baby Syndrome)

Methemoglobinemia is a condition that some babies are born with (congenital) or some develop early in life (acquired). Acquired methemoglobinemia is more common than the congenital form. It can be caused by exposure to a variety of substances and by some health conditions.

Methemoglobinemia and Other Dyshemoglobinemias

Methemoglobin is a metalloprotein, in which the iron in the heme group is in the Fe3+(ferric), not the Fe2+(ferrous), state of normal hemoglobin (Hb). Methemoglobinemia occurs because of either increased production of oxidized Hb due to exposure to environmental agents or diminished reduction of oxidized Hb because of underlying germline mutations.

Methemoglobinemia: Cyanosis and Street Methamphetamines

Methemoglobinemia can be detected with a simple office test. After placing 1 drop of the patient's blood on a piece of filter paper next to a drop of blood from a normal individual, when dry, the methemoglobin-containing blood will turn a deep chocolate-brown or slate-gray color.

REBEL Core Cast 90.0 – Methemoglobinemia

Methemoglobinemia can result from exposure to a number of different medications. The most common are dapsone and topical anesthetic agents (i.e. benzocaine) Consider the diagnosis in any patient with cyanosis and hypoxia that doesn’t respond to oxygen administration. Administer methylene blue to any patient with abnormal vital signs, metabolic acidosis, end organ dysfunction or, a serum level > 25%.

Recommendations for diagnosis and treatment of methemoglobinemia

Acquired methemoglobinemia is the consequence of drug ingestion or toxic exposure that cause acceleration of Hb oxidization from the ferrous to the ferric state.. The drugs that cause methemoglobinemia are numerous, including sulfonamides, lidocaine and other aniline derivatives, and nitrites. The most common drugs are benzocaine and lidocaine. Nitrates and the nitrites contaminating water supplies or used as preservatives in foods can also be trigger agents.

The Blue Baby Syndromes

Did environment or infection cause a blood disorder in newborns?