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Selecting the vein for venipuncture

Whenever possible, a blood specimen should not be obtained from an extremity when an IV is running (see page 29) or when dermatitis (skin inflammation) is present over the vein. If the patient has had a mastectomy with lymph nodes removed from the underarm area, a physician's authorization is required prior to performing phlebotomy on the involved extremity. The patient may offer specific information about arm preference, and it is important for you to listen to their specific needs. Follow any special instructions of the ordering physician or laboratory. Inspect the preferred arm first. If it appears good, attempt to draw from this arm. You may be able to see the vein. Veins appear blue and are slightly raised above the skin surface. Veins may be more difficult to see in obese people. Gloves can be put on at this point or they can be put on just before the venipuncture. Consult your institution's policy/procedure and follow the established guidelines. Always wash your hands or use an alcohol-based hand rub before you glove, and wear new, properly fitting gloves. Attach an unused sterile needle to the needle holder and assemble the necessary blood collection tubes. Always have extra evacuated tubes close at hand in case problems are encountered with the original tubes. Apply the tourniquet about 3 inches above the elbow, or midway between the elbow and shoulder, and have the patient make a fist.

The tourniquet must be applied with enough tension to compress the vein but not the artery. (An artery carries blood into the area, and if the tourniquet is too tight, blood flow will slow or stop.) Have the patient form a fist, which makes the veins more prominent, thus aiding in identification of the vein. There must not be any hand "pumping," which can alter some analyte concentrations. Have the patient keep their hand clenched until blood is flowing freely into the tube, and then ask the patient to unclench their hand. Some special tests may require that blood be collected without a tourniquet. Consult your phlebotomy manual or ask your supervisor for information. Do not leave the tourniquet on for more than 1 minute while you search for a vein. If more than 1 minute passes, release the tourniquet for at least 3 minutes. Then, re-apply the tourniquet. Inspect and palpate the area to find a vein. Prolonged obstruction of blood flow by the tourniquet (ie, tourniquet in place for longer than 2 to 3 minutes) changes some test results.

Always palpate or feel for the vein, even when the vein is seen. This procedure gives you practice in finding deeper, unseen veins. The vein will feel like an elastic tube that "gives" under the pressure of your finger. Arteries pulsate, so make certain the structure you feel is not pulsating.


So You're Going To Collect A Blood Specimen

If the vein has been used repeatedly for fluid injections and punctures, it may feel cord-like. Such a vein should not be used because it is difficult to obtain blood from it. If a vein is difficult to find, it may become easier to see after massaging the arm from wrist to elbow, which forces blood into the vein. Or, the area may be tapped sharply with the index and second finger 2 or 3 times, which may cause the vein to dilate. If necessary, a warm damp washcloth can be placed on the skin for a few minutes to make the veins stand out.

If you are not certain that you have found a vein, examine the other arm. Sometimes veins in one arm are small, while those in the other arm are larger. A patient who has had prior venipunctures may be able to tell you where a vein can best be found. A transilluminator or pocket pen light may be used to help visualize the vein in infants and children.

Performing the venipuncture

Starting from the point you have selected for the venipuncture and moving outward in a circular motion, clean the area for venipuncture with an alcohol or chlorhexidine gluconate/alcohol pad, as appropriate. If you accidentally touch the skin where you plan to draw blood, re-clean the area with alcohol. Allow the area to dry, or wipe dry in an outward circular motion with a gauze pad to prevent pain and hemolysis (the destruction of red blood cells) due to residual alcohol. Do not blow on the area as this will contaminate the site.


The vein should be "fixed," or held taut, during the puncture. To do this, place your thumb about an inch below where the needle is to enter and press down on the arm; at the same time, pull the skin toward the hand. The fingers of your hand should be around and underneath the patient's arm, grasping the patient's arm as your thumb stretches and holds the vein taut.

An Introduction To Phlebotomy



The needle should be in line with the vein. The needle should be at about a 15-degree angle with the skin (see figure).


Rubber Septum

Evacuated tube

After removing the protective cap, look at the needle to make sure it is free of burrs and nicks. Properly discard any suspicious needle and blood tube holder into an approved puncture-resistant sharps container. Insert the first tube into the evacuated tube holder resting on the inside needle. Do not push all the way down since this will prematurely break the vacuum seal of the tube. Under certain circumstances you may wish to use a syringe with a needle or a butterfly device (winged set) rather than an evacuated tube collection system.

Inform the patient that the venipuncture is about to occur. Introduce the needle with the bevel up. (The bevel is the flattened area that extends back from the tip.) The skin should be punctured with a clean, smooth motion. Do not hesitate.

Needle bevel up


When you introduce the needle, grip the holder firmly and keep it steady. As the needle enters the vein, a little "give" will be noted. After the vein is entered, decrease the angle of the needle and slide the needle further into the vein. When the needle is in the vein, push the collection tube all the way down into the blood tube holder, keeping the needle as stable as possible in the vein. Blood should flow into the tube due to the vacuum in the tube. As blood flows into the collection tube following the puncture, watch the flow until collection is completed and the tube has been filled.


Evacuated Tube


As soon as the tube is filled, hold the blood tube holder steady and carefully pull the tube out without dislodging the needle from the vein. If the tube contains an additive, mix the contents by gently inverting it 5 to 10 times before the next tube is inserted into the blood tube holder. There are important exceptions to this rule: light blue top sodium citrate tubes


So You're Going To Collect A Blood Specimen

should be inverted no more than 3 to 4 times; pearl white top EDTA tubes should be mixed 8 to 10 times.

If additional tubes are required, slide the next tube in and press the tube firmly so that the stopper is fully penetrated by the needle. Remove the last collection tube from the holder before removing the needle from the vein. If blood collection will require several minutes, the tourniquet should be removed as soon as there is good blood flow into the tube. Optimal recommended total tourniquet time, including prepuncture search, should not exceed 1 minute.


The tourniquet must be removed before withdrawing the needle from the puncture site. After removing the needle from the puncture site, immediately activate or deploy the safety device and discard the needle and blood tube holder into an approved puncture-resistant sharps container.

You have collected the blood specimen ... what next?

After collecting the specimen, place a dry, clean gauze pad or cotton ball over the needle puncture site and apply pressure. Instruct the patient to keep the arm in an extended straight position, and press the gauze pad or cotton ball against the puncture site for at least 5 minutes. Common errors The most common errors a beginner makes are failure to fix the vein or failure to insert the needle tip all the way within the vein. If the needle tip is only partly through the vein, blood flow will be inadequate. After the needle has been removed from the arm, some phlebotomists instruct the patient to bend the arm, but this is wrong. This practice keeps the needle puncture wound open, permitting blood to escape freely into the tissues, causing a bruise or hematoma. The proper procedure is to have the patient apply pressure to the site with a clean gauze pad. An alcohol pad should not be used to apply pressure. Instruct the patient on how to maintain pressure on the puncture site. If the patient cannot apply pressure to the gauze pad on the arm, you should press it on the arm as long as necessary to stop the bleeding (2 to 5 minutes). Never use an alcohol pad to maintain pressure and stop the bleeding. Finally, inspect the puncture wound. When the bleeding has stopped, apply an adhesive bandage. Instruct the patient to leave it in place for at least 15 minutes. Label the collection tubes in the presence of the patient. Information that should be recorded on the tube includes the patient's full name, unique identification number, date and time collected, and your initials.

An Introduction To Phlebotomy


If the patient has a low platelet count, a bleeding disorder, or is on anticoagulation therapy, the blood flow may not stop readily. This continued flow may be related to the patient's disease or therapy. In these cases, have the patient elevate the arm above shoulder level and keep the pressure on the site for 5 to 10 minutes or more. When bleeding has definitely stopped, apply a pressure adhesive bandage (folded gauze pad firmly held in place by appropriate tape). Inform the patient not to use the affected extremity for a short period of time and avoid strenuous activity using the extremity for 24 hours. If the bleeding continues, maintain pressure on the phlebotomy site and ask the nurse or your supervisor for help. Do not leave the patient until the situation is under control. An accidental arterial puncture will result in the pulsating flow of bright red blood, which will not stop readily. Immediately withdraw the needle, apply pressure until the bleeding has stopped. When bleeding has stopped, apply a pressure adhesive bandage. Notify the nurse or physician that an accidental arterial puncture has occurred. If the bleeding continues, maintain pressure on the phlebotomy site and ask the nurse or your supervisor for help. Do not leave the patient until the situation is under control. Do not leave any of your blood collection materials at the collection site, such as in the patient's room or home. Remove and properly dispose of your gloves, and wash your hands with either an alcoholbased hand rub (if hands are not visibly soiled) or soap and water (if hands are visibly soiled), before proceeding to the next patient.

Before phlebotomy, always ask patients if they are taking anticoagulants or if they have an inherited blood clotting problem. Patients who are taking medicine to prevent their blood from clotting (ie, anticoagulants such as coumadin, heparin, or aspirin) or patients who have inherited a blood clotting abnormality (eg, hemophilia) may continue to bleed from the punctured vein. If this bleeding is not stopped, blood may accumulate within the tissues of the arm, specifically in the enclosed area of the arm that surrounds the muscle. This bleeding can lead to a condition called "compartment syndrome" where the blood accumulates in a contained space within the arm such that the pressure produced can interfere with blood flow and pressure may injure the muscle. This is a rare but very serious complication and requires an emergency surgical procedure to open the compartment, relieve the pressure, and stop the bleeding.

Multiple specimen collection

In general, when multiple tubes are drawn during a single venipuncture, tubes without additives should be drawn before tubes with additives to avoid contamination. Common additive tubes are also drawn in a specific order to avoid potential additive cross-contamination (see chart on page 27).

Avoid hemolysis

Hemolysis, the destruction of red blood cells, should be avoided to ensure accurate results. Avoid hemolysis by allowing the venipuncture site to dry thoroughly after cleaning. Avoid prolonged use of a tourniquet or repeated fist clenching. Avoid using a needle that is too large


So You're Going To Collect A Blood Specimen

or too small (consult institutional policy), and avoid drawing blood from a site that has a hematoma. Hemolysis may be caused by slow blood flow into the tube due to a suboptimal venipuncture. If using a syringe, make sure the needle is fitted securely on the syringe to avoid frothing. Gently invert filled tubes (as directed by the manufacturer) rather than shaking the tubes, as shaking may cause hemolysis.

If blood fails to enter the evacuated tube

If the needle was not introduced far enough into the vein, lower the angle and advance it a little more. If the needle appears to have missed the vein, make sure the vein is fixed with the thumb, partially pull the needle back without removing it from the skin, and attempt to puncture the vein again. Positioning of the needle is critical. If you think that you have gone completely through the vein, slowly pull back the needle. As the needle moves back into the center of the vein, blood will flow. Be careful not to pull the needle back further once flow is established. Other needle positioning errors include:

Bevel against the wall of the vein, restricting blood flow into the needle. Partially inserted in the wall of the vein, allowing blood to leak into surrounding tissue. Collapsed vein. Thrombosed vein.

If at any time during the above maneuvers a hematoma appears, have the patient unclench their fist, release the tourniquet immediately, withdraw the needle, and apply pressure with a clean, gauze pad for at least 5 minutes (see page 23). Ensure that further bleeding has stopped, or continue to maintain direct pressure. If significant bleeding occurs, notify the supervisor, nurse, or physician.

An Introduction To Phlebotomy




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