Hemoglobin Derivatives
Alternate Names : Carbon Monoxide Poisoning, Carboxyhemoglobin, Methemoglobin, Sulfhemoglobin
DefinitionThis is a blood test to detect and measure the percentage of abnormal hemoglobin derivatives that result from drugs such as nitroglycerin or poisoning by carbon monoxide.
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Why is the Test Performed?
Hemoglobin is the substance in red blood cells that transports oxygen and carbon dioxide between the lungs and body tissues.
If certain chemicals or drugs are introduced into the blood stream, they can alter the hemoglobin so it no longer functions as a transport medium. Measuring abnormal hemoglobins can be helpful in diagnosing and monitoring exposure to these agents.
Carboxyhemoglobin is hemoglobin bound to carbon monoxide instead of oxygen or carbon dioxide. Carbon monoxide has a much higher affinity for hemoglobin than does oxygen (210 times more), and high percentages of carboxyhemoglobin in the blood impairs the normal transport of oxygen by the blood.
Sulfhemoglobin results from the union of hemoglobin with medications such as phenacetin or sulfonamides. This form of hemoglobin is unable to transport oxygen, and is untreatable. The only solution is to wait until the affected red blood cells are destroyed as part of their normal life cycle.
Methemoglobin occurs when the iron that is part of hemoglobin is altered such that it does not carry oxygen well. Certain compounds introduced into the blood stream can cause this problem:
- sulfonamides
- chlorates
- nitrates
- nitrites
- aniline
- phenacetin
There is also a congenital form of this disorder caused by a deficiency of NADH cytochrome b5 reductase, and another form caused by hemoglobin M disease.
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