Arteries Information and Courses from MediaLab, Inc.

If a plaque ruptures it will expose sub-endothelial tissue to blood cells and in so doing stimulate the formation of a clot. The clot is the body's attempt to seal off the crack but the clot itself can cause further obstruction to blood flow. This sudden increase in the blockage caused by the raised ruptured plaque and associated clot can transform a mild blockage into a critical one within a matter of hours. If it occurs within the blood vessels of the heart, the decrease in blood flow leads to severe and prolonged chest pain known as unstable angina. Such a patient is at obvious risk for a myocardial infarct should the blockage become any worse.Atherosclerosis typically begins in early adolescence, and is found in most major arteries but since it is asymptomatic during the early half of life we need cardiovascualr risk markers to help assess patient risk. If an at-risk patient is identified early, the hope is that medication, lifestyle changes or medical procedures can be used to avert a serious cardiovascular event. So, although the vast majority of us have some degree of atherosclerosis, risk markers can help identify those among us who are in more imminent danger or who have increased risk of an adverse cardiovascular event.

Deoxygenated (venous) blood flows from tiny capillary blood vessels within the tissues via progressively larger veins to the right side of the heart.Blood is routinely drawn from veins, but may also be drawn from arteries, or capillaries. Illustration this screen from LifeArt Collection 2000, with permission. © Lippincott Williams & Wilkins.

Hand position: It is best practice to position the patient's hand slightly downward with the top of the hand facing the phlebotomist. The fingers of the patient's hand should be rolled underneath and wrapped around the fingers of the phlebotomist's "anchoring" hand forming a loose fist. The phlebotomist should use his or her thumb to pull back gently on the surface of the skin, making the skin taut. The vein should be anchored adequately to proceed with venipuncture. The phlebotomist may have the patient roll his/her fingers over a pillow or a rolled up washcloth to make the hand vein more prominent.Tourniquet Position: The tourniquet should always be applied 3 - 4 inches above the needle insertion point. Therefore, when assessing for a usable vein in a hand, apply the tourniquet 1 - 2 inches above the wrist. If the tourniquet is on longer than one minute, release and reapply prior to venipuncture to avoid hemoconcentration.Cautions: Choose a straight section of the hand vein-- avoid the "intersection" or "V" where a vein branches into another vein. This juncture may contain a valve and could be damaged if punctured. Only use the top of a hand or thumb-side of the wrist for puncture. Avoid the fingers or the underside of the wrist. This will prevent the inadvertent puncture of hidden arteries, tendons or nerves in the area.