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Ammonium ion How the Test is Performed:
Adult or child:
Blood is drawn from a vein ( venipuncture ), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (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 tourniquet 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 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.
How to Prepare:
Fast for 8 to 12 hours. The health care provider may advise you to withhold drugs that may affect test results.
Drugs that can interfere with the test include thiazide or loop diuretics, barbiturates, acetazolamide, neomycin, and oral kanamycin. Consult the health care provider before this test if you are taking any of these medications.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How it Feels:
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 .
Risks:
- 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
Why this Test is Performed:
This test is performed when a condition that may cause toxic accumulation of ammonia is present or suspected.
Ammonia (NH4+) is produced by cells throughout the body, especially the intestines, liver, and kidneys. In the kidneys, NH4+ plays a minor role in the acid/base balance but is otherwise a metabolic waste product (primarily the result of protein metabolism ). Most of the ammonia produced in the body is used by the liver in the production of urea. Urea is also a waste product but is much less toxic than ammonia. Ammonia is especially toxic to the brain even at concentrations 100 times less than the normal concentrations of urea.
Normal Values:
The normal range is 15 to 45 mcg/dl.
Note: mcg/dl = micrograms per deciliter
Abnormal Results:
Conditions that can increase ammonia levels include:
Cost:
The estimated cost is $35 to $87.
Special Considerations:
This test is about 90% accurate.
Patients with liver disease may have clotting problems. After the venipuncture , pressure may need to be applied to the puncture site for several minutes to ensure that bleeding has stopped.
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.
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