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The structure of cytochrome b5 reductase, the enzyme that converts methemoglobin to hemoglobin. [1]Methemoglobin (British: methaemoglobin, shortened MetHb) (pronounced "met-hemoglobin") is a hemoglobin in the form of metalloprotein, in which the iron in the heme group is in the Fe 3+ state, not the Fe 2+ of normal hemoglobin.
However, co-oximetry can distinguish the methemoglobin concentration and percentage of hemoglobin. [3] At the same time, the SpO2 concentration as measured by pulse ox is false high, because methemoglobin absorbs the pulse ox light at the 2 wavelengths it uses to calculate the ratio of oxyhemoglobin and deoxyhemoglobin.
Finger tip carboxyhemoglobin saturation monitor.. A CO-oximeter is a device that measures the oxygen carrying state of hemoglobin in a blood specimen, including oxygen-carrying hemoglobin (O2Hb), non-oxygen-carrying but normal hemoglobin (HHb) (formerly, but incorrectly, referred to as 'reduced' hemoglobin), as well as the dyshemoglobins such as carboxyhemoglobin (COHb) and methemoglobin (MetHb).
Methemoglobin is also formed in small quantities when the dissociation of oxyhemoglobin results in the formation of methemoglobin and superoxide, O 2 −, instead of the usual products. Superoxide is a free radical and causes biochemical damage, but is neutralised by the action of the enzyme superoxide dismutase.
An arterial blood gas (ABG) test, or arterial blood gas analysis (ABGA) measures the amounts of arterial gases, such as oxygen and carbon dioxide.An ABG test requires that a small volume of blood be drawn from the radial artery with a syringe and a thin needle, [1] but sometimes the femoral artery in the groin or another site is used.
Methemoglobin is an oxidized form of hemoglobin attached to a ferric-state iron (Fe3+), which can therefore not carry and deliver oxygen to tissues. [15] The formation of methemoglobin occurs when electrons are not returned to the iron of a normal state hemoglobin, which is not preferred for a functioning organism.
Initial oxidation to the ferric (Fe 3+) state without oxygen converts hemoglobin into "hemiglobin" or methemoglobin, which cannot bind oxygen. Hemoglobin in normal red blood cells is protected by a reduction system to keep this from happening. Nitric oxide is capable of converting a small fraction of hemoglobin to methemoglobin in red blood cells.
Hemoglobin M disease is a rare form of hemoglobinopathy, characterized by the presence of hemoglobin M (HbM) and elevated methemoglobin (metHb) level in blood. [1] HbM is an altered form of hemoglobin (Hb) due to point mutation occurring in globin-encoding genes, mostly involving tyrosine substitution for proximal (F8) or distal (E7) histidine residues. [2]