7-2 BLOOD COLLECTION

LEARNING OBJECTIVE: Identify the correct steps to perform blood collection by the finger puncture method and venipuncture method, and recall Standard Precautions and other safety precautions that apply to blood collection.

There are two principal methods of obtaining blood specimens: the finger puncture method and the venipuncture method. For most clinical laboratory tests requiring a blood specimen, venous blood obtained by venipuncture is preferred. Blood collected by venipuncture is less likely to become contaminated, and the volume of blood collected is greater. Infection control practices, equipment requirements, and step-by-step instructions on performing both of these blood collection methods will be discussed in the following sections.

STANDARD PRECAUTIONS

Under the concept of “Standard Precautions” outlined by the Centers For Disease Control and Prevention (CDC), blood and other bodily fluids should be considered as potentially infectious. To protect medical personnel from direct contact with blood during phlebotomy (blood collection), gloves are required to be worn. Gloves should be disposed of after each patient.

Needles and sharps used in the blood collection process should be handled with extreme caution and disposed of in biohazard sharps containers. Sharps containers should be conveniently located near phlebotomy work sites.

Absorbent materials, such as cotton 2 x 2’s used to cover blood extraction sites, normally contain only a small amount of blood and can be disposed of as general waste. However, if a large amount of blood is absorbed, the absorbent material should be placed in a biohazard waste container and treated as infectious waste.

Clean phlebotomy work site equipment and furniture daily with a disinfectant.

FINGER PUNCTURE

The finger puncture method is used when a patient is burned severely or is bandaged so that the veins are either covered or inaccessible. Finger puncture is also used when only a small amount of blood is needed.

Materials Required for Finger Puncture Procedure

To perform a finger puncture, the following materials are required:

Arrange your equipment in an orderly manner and have it within easy reach. Also, wash your hands before and after each procedure.

Finger Puncture Procedure

To perform a finger puncture, follow the steps given below.

  1. Explain the procedure to the patient.
  2. Using the middle or ring finger, massage or “milk” the finger down toward the fingertip. Repeat this “milking” five or six times.
  3. Cleanse the fingertip with an alcohol pad or povidone-iodine solution and let dry.
  4. Take a lancet and make a quick deep stab on the side of the finger (off-center). To obtain a large rounded drop, the puncture should be across the striations of the fingertip. See figure 7-3.

Figure 7-3.—Finger puncture.

  1. Wipe away the first drop of blood to avoid dilution with tissue fluid. Avoid squeezing the fingertip to accelerate bleeding as this tends to dilute the blood with excess tissue fluid, but gentle pressure some distance above the puncture site may be applied to obtain a free flow of blood.
  2. When the required blood has been obtained, apply a pad of sterile gauze and instruct the patient to apply pressure, then apply a bandage.

When dealing with infants and very small children, the heel or great toe puncture is the best method to obtain a blood specimen. This method is performed in much the same way.

VENIPUNCTURE (VACUTAINER METHOD)

The collection of blood from veins is called venipuncture. For the convenience of technician and patient, arm veins are best for obtaining a blood sample. If arm veins cannot be used due to interference from bandage or IV therapy, thrombosed or hardened veins, etc., consult your supervisor for instructions on the use of hand or foot veins.

NOTE

Do not draw blood from an arm with IV fluid running into it. Choose another site. The IV fluid will alter tests results.

Materials Required for Venipuncture Procedure

To perform a venipuncture, the following materials are required:

Arrange your equipment in an orderly manner and have it within easy reach. Also, wash your hands before the procedure.

Venipuncture Procedure

Position the patient so that the vein is easily accessible and you are able to perform the venipuncture in a comfortable position. Always have the patient either lying in bed or sitting in a chair with the arm propped up.

WARNING

Never perform a venipuncture with the patient standing up. If patients should faint, they could seriously injure themselves. Also, safeguards should be in place to prevent patients from falling forward when they are seated.

To perform venipuncture, follow these steps:

  1. Explain the procedure to the patient.
  2. Apply tourniquet around the arm approximately 2 to 3 inches above the antecubital fossa (the depression in the anterior region of the elbow, see figure 7-4) with enough tension so that the VEIN is compressed, but not the ARTERY. A BP cuff (sphygmomanometer) may be used instead of a tourniquet if a patient is difficult to draw.
  3. Position the patient’s arm extended with little or no flexion at the elbow.
  4. Locate a prominent vein by palpation (feeling). If the vein is difficult to find, it may be made more prominent by massaging the arm with an upward motion to force blood into the vein.
  5. Cleanse the puncture site with a 70% alcohol pad or povidone-iodine solution and allow to dry.

CAUTION

After cleaning the puncture site, only the sterile needle should be allowed to touch it.

  1. “Fix” or hold the vein taut. This is best accomplished by placing the thumb under the puncture site and exerting a slight downward pressure on the skin or placing the thumb to the side of the site and pulling the skin taut laterally (fig. 7-4).
  2. Using a smooth continuous motion, introduce the needle, bevel side up, into the side of the vein at about a 15-degree angle with the skin (fig. 7-4).

Figure 7-4.—Venipuncture.

  1. Holding the vacutainer barrel with one hand, push the tube into the holder with the other hand and watch for the flow of blood into the tube until filling is completed.
  2. Once all the specimens have been collected, hold the vacutainer with one hand and release the tourniquet with the other.
  3. Place a sterile gauze over the puncture site and remove the needle with a quick, smooth motion.
  4. Apply pressure to the puncture site and instruct the patient to keep the arm in a straight position. Have the patient hold pressure for at least 3 minutes.
  5. Take this time to invert any tubes that need to have anticoagulant mixed with the blood.
  6. Label specimens.
  7. Re-inspect the puncture site to make sure bleeding has stopped, and apply a bandage.