Definition
This is a test that measures the amount of methanol in the blood.
How the test is performed
Blood is drawn from a vein 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.
For an infant or young child, the area is cleansed 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. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
The blood is then analyzed in a laboratory.
How to prepare for the test
No special preparation is necessary.
How the test will feel
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
This test is performed to detect the presence of methanol in the body.
Methanol is sometimes drunk mistakenly or intentionally as a substitute for grain alcohol (ethanol). Its presence in blood and body fluids can cause osmolality and electrolyte disturbance leading to toxic effects.
Of greatest concern is the fact that methanol is broken down in the body to formaldehyde, a highly toxic chemical that can damage the optic nerve, causing blindness, and damage the liver and the kidneys, potentially causing death.
Normal Values
No presence of methanol is normal.
What abnormal results mean
No amount of methanol is normally found in the body. Its presence indicates possible poisoning.
What the risks are
Collection of blood may be associated with:
- excessive bleeding
- fainting or feeling lightheaded
- hematoma (blood accumulating under the skin)
- infection (a slight risk any time the skin is broken)
- multiple punctures to locate veins
Special considerations
Oddly enough, the treatment for methanol poisoning is intravenous (directly into a vein) infusion of grain alcohol (ethanol). Because ethanol is broken down by the same enzyme in the liver that converts methanol to formaldehyde, adding ethanol to the blood stream slows down the production of formaldehyde to a rate at which the body can dispose of it in the urine or through other less common chemical reactions.
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.
| • | Osmolality |
| • | Electrolytes |
Reviewed By: Daniel R. Alexander, M.D., Department of Internal Medicine, St. Mary's Hospital, Leonardtown, MD. Review provided by VeriMed Healthcare Network.
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