Venipuncture: Definition, Indications, Preparation, Procedure and Safety Measures

It is the collection of blood from the veins.

It is most often done for the purpose of laboratory testing. It is done with a needle, and is usually done by a phlebotomist.

Venipuncture can also be done to remove extra red blood cells from the blood and treat various blood disorders.

There are many factors at play during a venipuncture procedure.

For example, the order of extraction is a vital concept that must be followed and understood in order to avoid additive cross-contamination between tubes.

Venipuncture is actually one of the most routine invasive procedures.

Reasons for Venipuncture

There are five main reasons to perform a venipuncture:

  • Obtaining blood for diagnostic purposes.
  • Monitoring of blood component levels.
  • Administration of therapeutic treatments (drugs, nutrition, chemotherapy).
  • Drawing blood due to excessive levels of iron or erythrocytes (red blood cells).
  • Collect blood for later use (donor transfusion).

Previous preparation for the venipuncture process

All necessary supplies should be gathered in a tray. The equipment used during the venipuncture test can vary, but the following are the most commonly used for routine venipuncture:

  • Latex tourniquet.
  • Individually packaged 70% isopropyl alcohol swabs.
  • Sharps disposal container. An acceptable puncture-proof container marked ‘Biohazard’.
  • Gloves.
  • Safety needles, 22g or less, butterfly needles. 21g or less.
  • Syringes
  • Vacutainer tube holder.
  • Transfer device.
  • Blood collection tubes. Vacuum tubes are designed to draw a predetermined volume of blood. Tubes with different additives are used to collect blood samples for specific types of tests. The color of the cap is used to identify these additives.

It is necessary to prepare the patient for the process and to verify that the diet or time restrictions have been met.

Hygiene measures

  • Maintain adequate hygiene in the utensils used.
  • Hand washing with antiseptic soaps.
  • Use of gloves.
  • Prepare the patient’s arm by cleaning the puncture site with the 70% alcohol pad or a chlorhexadine wipe by gently spiraling outward from the penetration site.
  • Allow to air dry before continuing.
  • Do not touch the puncture site after cleaning, dry the site with gauze, or blow on the area to dry it as this will contaminate the site. If this happens accidentally, the venipuncture site must be cleaned again.
  • Make sure the venipuncture site is dry.

Turnstile placement

Apply the 3- to 4-inch tourniquet over the selected puncture site and ask the patient to make a fist and assess the antecubital space.

Leave on for 1 minute and instruct the patient to make a fist and hold it, without pumping the hand.

The tourniquet should never be left on for more than 1 minute and if a tourniquet is used for preliminary vein screening, release it and reapply after two minutes.

Position the patient with the arm extended to form a straight line from the shoulder to the wrist.

Venipuncture sites

Phlebotomists do not always draw blood from the same area and site on the human body.

Venipuncture is most often done in the antecubital fossa, which is the inside of the elbow. In this region, phlebotomists will generally decide between three veins, including the middle ulnar vein, the cephalic vein, and the basilic vein.

If all of these veins in the inner elbow area do not look promising, then the phlebotomy technician may choose a dorsal vein in the hand or, in the worst case, a vein in the foot.

The most common problems include inadequate blood flow from the vein, causing phlebotomists to switch sites.

Select the venipuncture site by palpating with the gloved index finger.

The veins will become more prominent if the patient clenches his fist tightly.

Due to its proximity to the brachial artery and the median nerve, the basilic vein, which is located on the pink side of the arm, should be used only if there is no other more prominent one.

Places to avoid

The following sites should be avoided when performing a venipuncture:

  • Extensive scarring from burns or surgery.
  • The veins in the foot and ankle should be used only as a last resort.
  • At no time can phlebotomists perform venipuncture in an artery and veins in the lower part of the wrist should be avoided.
  • The upper limb on the side where a mastectomy was performed.
  • Venipuncture should not be performed on a bruise. Venipuncture should be done distal to (below) the hematoma.
  • In cases of IV therapy or blood transfusions, if the opposite arm cannot be removed, then blood should be drawn below (distal to) the IV, but never above the IV site.
  • In edematous extremities, since the accumulation of fluid in the tissues can alter the results of the test.
  • Sites with notable skin conditions, such as eczema or infection.
  • Samples should not be obtained from an arm that has a cannula, fistula, or vascular graft.
  • Wait 10-15 minutes after a transfusion is complete before obtaining a blood sample.
  • Do not attempt a venipuncture more than twice.

Inserting the needle

To properly anchor the vein and perform the venipuncture, the following should be taken into account:

  • Select the appropriate size needle and connect it to the syringe or vacutainer hub.
  • Firmly grasp the patient’s arm and squeeze the skin with the thumb to tighten the skin and anchor the vein, the index finger should not be used to pull the skin up as this increases the risk of sticking, the index finger should be just below the puncture site.
  • When using a syringe, be sure to pull the plunger in and out
  • Attach the appropriate needle to the hub by removing the plastic cap over the small end of the needle and inserting into the hub, turning firmly and holding the bevel up, at a 15-30 degree angle to the skin, toward the light of the come to.
  • Holding the needle in line with the vein, use a quick, small push to penetrate the skin and enter the vein in one smooth motion.

Holding the bucket securely, insert the first aspirator tube in the correct order of removal into the large end of the bucket that penetrates the stopper. Blood should flow into the evacuated tube.

If the patient complains of “shooting, electrical pain, or tingling or
numbness proximal or distal to the puncture site,” the needle should be withdrawn immediately. A nerve may have been pinched
and possibly damaged.

In the event of an incident, the venipuncture should be repeated at a different site and the incident should be documented.

If an arterial puncture is suspected, as indicated by a bright red, rapid, pulsating flow, with or without rapid development of a hematoma, the needle should be withdrawn immediately. Forceful direct pressure should be applied to the site for a minimum of five minutes or until the bleeding has stopped.

If the blood does not start to flow, it should:

  • Reposition the needle by gently moving the needle back or forward on the arm.
  • If the blood is flowing slowly, the angle should be gently adjusted to see if the needle is resting against the wall of the vein.
  • The tourniquet may also be loosened, as it may be blocking the blood.
  • If vacuuming, try another tube, there may be no vacuum in the tube.

After you have tried these options and the blood is still not flowing, remove the tourniquet, remove the needle, and begin the process with a new site.

Removal of the needle used in venipuncture

Once the process is completed, blood flow must be restored and the patient should be instructed to relax their hand and then release the tourniquet and place a gauze over the venipuncture site and remove the needle.

Apply adequate pressure to the puncture site to stop bleeding and prevent bruising.

The patient or companion should be asked to apply pressure for at least 2 minutes. Once the bleeding stops, apply a fresh bandage, gauze, or tape.

Additional Considerations When Performing Venipuncture

When performing a venipuncture, the following considerations should be taken into account:

For the prevention of a hematoma, only the upper wall of the vein should be pierced, and make sure that the needle fully penetrates the upper wall of the vein, a partial penetration can allow blood to leak into the tissue surrounding the vein .

The tourniquet must be removed before the needle is removed and pressure must be applied to stop the bleeding once the phlebotomy is performed.
A hematoma can cause a compression nerve injury after phlebotomy.

To prevent injury to a nerve, tendon, or muscle, careful palpitation and an appropriate entry angle should be used.

Excessive probing (not calculated from side to side) with the needle should be avoided.

To prevent dizziness or fainting and possible injury you must
ensure that the patient is sitting in a suitable traction chair or lying on a bed. Have appropriate support staff as available.

For infection prevention, proper infection control policies must be followed.

Draw order in a venipuncture

Following the draw order is important to avoid cross contamination by tube additives that could lead to erroneous results.

Once the blood has been drawn, the tubes should be filled according to the ‘Order of extraction for a venipuncture’ using the tubes according to the colors that identify it as follows:

  • Blood culture.
  • Light blue top (plasma) : 3.2% sodium citrate. These tubes are used for clotting tests and must be completely filled to ensure the proper ratio of blood to anticoagulant.
  • Red cap (serum) : normal and gel. Used for chemistry and benchmark tests.
  • Green cap (plasma): with and without gel, contains lithium heparin. These tubes are used primarily for chemistry tests.
  • Lavender or Pink Top (plasma): contains EDTA. Mainly used for hematology and blood bank analysis.
  • Gray Top (Plasma) : Contains Sodium Fluoride / Potassium Oxalate. Used by chemistry for glucose testing.
  • Yellow cap (plasma and cells) : Contains ACD solution A or B. It is used for genetic testing.

Remarks: When you use a winged blood collection set for venipuncture and a coagulation tube is the first tube needed, please remove a discard tube first (simple red top or light blue top. It is not necessary to fill the tube of discard completely.

Once the tubes are filled, each tube should be gently inverted according to color:

  • Light Blue Top: Invert 3-4 times.
  • Red and gold tops are reversed 5 times.
  • All other tubes containing an additive should be gently inverted 8-10 times.

Do not shake or mix vigorously. If multiple tubes are needed, follow the correct order of extraction.

Special handling techniques must be implemented, and samples must be transported safely and in an orderly manner to the laboratory for analysis.

Tube labeling

Tubes should be positively identified after filling with a firmly attached patient label. The label should include the patient’s first and last name, date of birth, date and time of collection, and collector’s initials.

If no patient labels are available, manually label the tubes with the required information. All labels must include two identifiers. The tube must be labeled before leaving the patient.

Security measures

  • Universal (standard) safety precautions must be observed.
  • All applicable isolation procedures must be observed.
  • Hand washing should be done with warm, running water with an appropriate hand washing product.
  • If hands are not visibly contaminated, a commercial foam hand wash product can be used before and after each patient collection.
  • Gloves should be worn during all phlebotomies and changed between patient collections.
  • Palpation of the phlebotomy site can be performed without gloves, as long as the skin is not broken.
  • A lab coat must be worn during blood collection procedures.
  • Needles and buckets are for single use only and are disposed of in a suitable ‘sharps’ container as a single unit.
  • The needles are never recapped, removed, broken, or bent after the phlebotomy procedure.
  • Gloves must be disposed of in the appropriate container immediately after the phlebotomy procedure.
  • All other items used for the procedure must be disposed of in accordance with proper biohazard waste disposal policy.
  • Contaminated surfaces should be cleaned with a freshly prepared 10% bleach solution. All surfaces are cleaned daily with bleach.
  • In the event of an accidental puncture, immediately wash the area with antibacterial soap, draw blood from the wound, and contact your supervisor