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Venipuncture How the Test is Performed:
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 .
How to Prepare:
Preparation may vary depending on the specific test. Some tests require overnight fasting, taking or refraining from drugs, or changing eating habits for short periods of time. Most tests do not require special preparation. As with any blood test, the health care provider may limit certain foods or medications shortly before the test to assure an accurate sample.
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:
Risks associated with venipuncture are slight: - 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:
Blood is used by the body for transportation of oxygen, food, waste products, and other materials within the body. It is also used for regulation of body temperature, regulation of fluids, and acid-base equilibrium. Blood is made up of a fluid portion (plasma) and a cellular portion. Plasma contains various substances dissolved in the fluid. Serum is what remains when fibrinogen has been removed from the plasma (this is the fluid that remains after blood is allowed to clot in a test tube). The cellular portion consists primarily of red blood cells, but also includes white blood cells and platelets . Because blood is used for multiple functions within the body, tests on the blood or its components may give valuable clues in the diagnosis of a multitude of medical conditions.
Normal Values:
Normal results vary with the specific test.
Abnormal Results:
Abnormal results vary with the specific test.
Cost:
The cost varies with the specific test.
Special Considerations:
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.
This is one "unit" of blood (approximately 500 cc) in a sterile plastic storage bag. The blood will be stored under tightly controlled refrigeration. All donated blood is screened for hepatitis and HIV. Very sensitive tests are used to insure that blood is not infected with HIV. Prior to being given, the blood will be "cross matched" against the individual that will receive it, to insure there are no matching problems.
This unit of blood has been typed, screened for disease, cross matched for blood type, and is now ready for infusion into the patient.
A blood centrifuge is used to separate donated blood into its components.
A needle has been inserted into a large vein in the forearm. Blood flows from the vessel through the tubing to the collection bag. Following donation the donor is given a large glass of juice, punch, or soda pop (not diet) and a heartfelt thanks. Donated blood has been responsible for saving millions of lives.
With the equipment shown here, a person can have blood drawn or blood can be given (transfusion).
Stored platelets after blood donation. Platelets are a very important component of blood. These tiny particles plug small holes in capillaries and vessels caused by the damage of everyday living. Platelets can be separated from blood and given to individuals who have low platelet counts and are at risk for serious bleeding.
This blood donor is being prepared for the procedure of donating blood. The skin is sterilized with an iodine preparation at the site where the needle will be inserted. This helps prevent the blood from being contaminated by bacteria living on the skin.
This bag has been filled with donated blood. The tubing is being heat-sealed to prevent entry of foreign bacteria or other infectious agents.
Donor chairs are usually comfortable. Modern chairs are motorized and can recline. Occasionally, a blood donor may become faint and the chair is then rotated to allow the donor to lie flat.
Individuals who are going to have surgery where significant blood loss is expected can donate blood to themselves. They may donate several times prior to their surgery. Their own blood provides a perfect match and there is minimal probability of contracting disease from the donated blood.
This is a typical blood storage refrigerator. The labels on the blood storage bags can be easily read through the transparent door, without opening the refrigerator and causing temperature changes. Extreme care is taken with this valuable life-saving material.
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