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Alternative namesMethemoglobin; Carboxyhemoglobin; Sulfhemoglobin; Carbon monoxide poisoning
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.
How the test is performed
Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.
A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
How to prepare for the testIf your child is to have this test performed it may be helpful to explain how the test will feel, and even practice or demonstrate on a doll. The more familiar your child is with what will happen to them, and the purpose for the procedure, the less anxiety they will feel.
How the test will feelWhen the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is 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.
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.
Normal ValuesThe following values represent the percentage of hemoglobin derivatives based on total hemoglobin:
What abnormal results meanAs abnormally high levels of hemoglobin derivatives rise, there are increasingly detrimental effects. Since these forms of hemoglobin do not permit the transfer of oxygen, the effects on the body are related to lack of oxygen to the tissues, which can result in tissue death.
The following values, except sulfhemoglobin, represent the percentage of hemoglobin derivatives based on total hemoglobin:
What the risks areRisks associated with having blood drawn are slight:
Special considerationsVeins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Update Date: 9/3/2003Michael C. Milone, M.D., Ph.D., Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
Last updated: Tue, 06 Jan 2009 00:20:03 GMT