metHb
metHb
methaemoglobin
A haemoglobin that results when oxyhaemoglobin in a ferrous (Fe2+) state is transformed into a ferric (Fe3+) state, which cannot transport O2. Low levels of methaemoglobin are always present in the circulation, but markedly increase after exposure to certain anaesthetics, benzocaines, nitrates, nitrites, phenacetin, etc., resulting in methaemoglobinaemia.Ref range
• Normal, < 3% total MetHb.
• Cyanosis, 10–20% MetHb.
• Anoxia > 30% MetHb.
Specimen
Serum in sodium heparin (green top tube).
Method
Spectrophotometry.