Arterial stick

• Alternative Names

  Blood sample - arterial

• How the test is performed

  Usually the blood is drawn from the wrist. However, it may also be drawn from the inside of the elbow, groin, or other artery. A heartbeat (pulse) is felt by pressing on the area above an artery. The doctor will usually check to make sure blood is flowing into the hand from the main arteries in the forearm (radial and ulnar arteries).

  The area is cleaned with antiseptic and a needle is inserted. A small amount of anesthetic may be injected or applied before the needle is inserted. The blood will easily flow into the specially prepared (heparinized) syringe.

  The needle is removed after there is enough of a blood sample. Pressure is applied to the puncture site for 5 - 10 minutes to stop the bleeding. You will be checked during this time to make sure the bleeding stops.

• How to prepare for the test

  Preparation varies with the specific test performed.

• How the test will feel

  Puncture of an artery may be somewhat more uncomfortable than puncture of a vein, because arteries are deeper than veins, have thicker walls, and have more nerves. Also, firm pressure must be placed over the site after the blood is drawn.

  When the needle is inserted, most people feel moderate discomfort or pain. Afterward, there may be some throbbing.

• Why the test is performed

  Blood transports oxygen, food, waste products, and other materials within the body. It also regulates body temperature, fluids, and the balance of acids and bases.

  Blood is made up of a fluid portion (plasma) and a cellular portion. Plasma contains various substances dissolved in the fluid. The cellular portion is made up mainly of red blood cells, but it also includes white blood cells and platelets.

  Because blood has many functions within the body, tests on the blood or its components may give valuable clues to help doctors diagnose many medical conditions.

  Blood in the arteries (arterial blood) differs from blood in the veins (venous blood) mainly in its content of dissolved gases. Testing arterial blood shows the make-up of the blood before any of its contents are used by the body tissues.

• Normal Values

  See specific tests, particularly the arterial blood gas test.

  Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

• What abnormal results mean

  An arterial stick is done to get blood samples from arteries. Arterial blood samples are mainly taken to measure arterial blood gases (which may indicate breathing problems or metabolic disorders). However, arterial sticks may sometimes be done to get blood culture or blood chemistry samples.

• What the risks are

  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.

  Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma (blood accumulating under the skin)
  • Bruising
  • Infection (a slight risk any time the skin is broken)

  There is a slight risk of damage to nearby tissues when the blood is drawn. Blood can be taken from lower-risk sites, and techniques are used to minimize tissue damage.

• Special considerations

  If blood is easier to get from one location or side of your body, let the person who is drawing your blood know before starting the test.

• References

  Mizma D, Janchar T. Arterial puncture and cannulation. In: Roberts JR, Hedges JR, eds. Clinical Procedures in Emergency Medicine. 4th ed. Philadelphia, Pa: Saunders Elsevier;2004:chap 20.

Review Date: 2/22/2009

Reviewed By: Linda Vorvick, MD, Family Physician, Seattle Site Coordinator, Lecturer, Pathophysiology, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.