methæmoglobin

Methaemoglobin (metHb) is a form of haemoglobin, the oxygen-carrying protein in red blood cells, in which the iron atom in the haem group is oxidized from the ferrous (Fe2+) state to the ferric (Fe3+) state. This oxidation prevents the haemoglobin from binding to oxygen, leading to a reduced oxygen-carrying capacity of the blood. Methaemoglobin is typically present in small amounts in the blood, but elevated levels can cause significant health issues.

Methaemoglobinemia is a condition characterized by an increased concentration of methaemoglobin in the blood. It can be caused by various factors, including certain medications, such as nitrates and nitrites, and exposure to chemicals like aniline dyes and certain drugs. Methaemoglobinemia can also result from genetic disorders, such as methaemoglobin reductase deficiency, where the body is unable to convert methaemoglobin back to haemoglobin.

Symptoms of methaemoglobinemia can range from mild to severe and may include cyanosis (bluish discoloration of the skin and mucous membranes), shortness of breath, and in severe cases, loss of consciousness. Treatment typically involves the administration of methylene blue, a drug that reduces methaemoglobin back to haemoglobin, restoring normal oxygen-carrying capacity.

Prevention of methaemoglobinemia involves avoiding exposure to known causes and using alternative medications when possible. Regular monitoring of blood oxygen levels and haemoglobin status can help in the early detection and management of methaemoglobinemia.