Arterial Blood Sample

Arterial Blood Sample

Definition

An arterial blood sample is a small amount of blood collected from an artery. The blood is then used for testing in the laboratory.

Who is a candidate for the test?

Arterial blood samples are most often used for an arterial blood gas, or ABG, test. ABGs are a series of blood measurements that are ordered as a single test. This test is primarily used to check lung function and acid levels in the body.
An arterial blood sample may also be done to obtain blood for a CHEM-20 or CHEM-7. These tests look at a number of chemicals in the blood serum. Blood cultures for aerobic or anaerobic organisms may also be done on an arterial blood sample. These tests look for bacteria and other organisms in the blood.

How is the test performed?

Arterial blood samples are drawn from an artery. Common sites include the wrist, elbow, or groin. The area is cleaned with an antiseptic. Sometimes a local anesthetic is injected to numb the area. A small sharp, hollow needle is carefully inserted into the artery at a steep angle directly over the pulse point.
Blood is collected using a syringe treated with heparin. Heparin is a blood thinner that keeps the sample from clotting in the syringe. Firm pressure is applied to the collection site for two or three minutes until it is certain that the artery will not bleed. This precaution, beyond that taken for an ordinary venous blood draw, is necessary because the blood pressure in an artery is so much higher than that in a vein.

What is involved in preparation for the test?

Usually no preparation is needed for an arterial blood sample.

What do the test results mean?

An arterial blood gas test can detect problems with the person's breathing and with the body's balance of acids and bases. Specifically, it measures the amount of oxygen and carbon dioxide in the blood. These measurements are particularly critical if a person is on a ventilator (breathing machine).
An analysis of oxygen and carbon dioxide levels and acid-base balance can reveal much about problems in specific cells and tissues. The healthcare professional will discuss results with the individual.

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