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Alternative names
SMA20; Sequential multi-channel analysis with computer-20; SMAC20; Metabolic panel 20Definition Return to top
Chem-20 is a group of 20 chemical tests performed on serum (the portion of blood without cells). Electrolytes are ionized salts in blood or tissue fluids (ions are atoms or molecules that carry an electrical charge). Electrolytes in the body include sodium, potassium, chlorine, and many others.
The rest of the tests focus primarily on chemicals related to the body's metabolism and the breakdown of various substances. These are tests that evaluate the function of the liver and kidneys.
How the test is performed Return to top
Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a 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.
Infant or young child:
The area is cleaned with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any continued bleeding.
How to prepare for the test Return to top
The patient should try not to eat overnight before the test.How the test will feel Return to top
When 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 Return to top
Blood chemistry measures the levels of a number of chemical substances that are released from various tissues in the body. The amounts of these chemicals in the blood may reflect abnormalities in the tissues secreting them.Normal Values Return to top
Key to abbreviations:
Electrolytes:
When an electrolyte test is performed, the measured ions usually include sodium, potassium, chloride, and bicarbonate. Calcium and magnesium levels are also obtained in many institutions as part of this test.
What abnormal results mean Return to top
See the individual tests.What the risks are Return to top
Special considerations Return to top
Veins 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: 8/7/2003 Updated by: Irfan A. Agha, M.D., Department of Medicine, Renal Division, St. Louis University, St. Louis, MO. Review provided by VeriMed Healthcare Network.
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Page last updated: 28 October 2004 |