Clinical Skills Venepuncture Dr Brian Jenkins (Clinical Skills Lead) Sian Williams (Clinical Skills Manager)
Aims and Objectives Aims and Objectives The aim of this module is to facilitate learning regarding the purpose and procedure of venepuncture. The learning outcomes are: To understand the need for venepuncture. To understand the need for care in handling blood samples, and the potential infection hazards. To understand the need for care in labelling blood samples. To understand the process of venepuncture and the skills necessary for success.
Introduction (1 of 2) Introduction (1 of 2) Venepuncture is a common procedure, carried out in order to obtain venous blood for tests required in patient management, either for investigation or diagnosis. When handling blood, all necessary procedures should be followed in order to prevent contamination of the environment or yourself. All blood is potentially infective, and should be treated as such. In addition, all appropriate local procedures for disposal of sharps should be followed. Full discussion of each of these procedures is beyond the scope of this document, and many differ slightly between hospitals. Ensure that you are familiar with these policies before blood samples are obtained. A medium sized needle (21 gauge, green) is required. This provides the required flow rate so that a moderate amount of blood can be obtained and stored in sample bottles without it clotting.
Introduction (2 of 2) Introduction (2 of 2) There are many blood tests (too many to list here), but fortunately there are far fewer bottles than tests. The more common tests are urea and electrolytes, full blood count, clotting studies, blood cross match. These will require the use of four bottles, and about 15-20 ml of blood will be required. Obtaining blood for microbiological culture requires a rigorous approach to sterility. Failure to maintain strict aseptic standards will result in growth of skin commensals, invalidating the test, possibly producing misleading results and inappropriate antibiotic treatment. This document does not cover venous catheterisation or arterial blood sampling. These procedures are covered in other documents.
Anatomy (1 of 2) Anatomy (1 of 2) Veins in the antecubital fossa are most commonly used for obtaining blood. These are usually large with little variation in anatomy. However, there are structures in the antecubital fossa that may be damaged if care is not used.
Anatomy (2 of 2) Anatomy (2 of 2) The brachial artery lies on the medial side of the antecubital fossa, so this should be palpated before venepuncture in order to avoid inadvertent puncture. The median nerve is usually centrally located and deep to the veins, so care should also be taken to avoid damage to this structure. From these considerations, it can be concluded that the best place for venepuncture is on the lateral side of the antecubital fossa. If you ensure the needle is superficial at all times, damage to other structures should be easily avoided.
Procedure (1 of 14) Procedure (1 of 14) Consent Explain the procedure to the patient, including the reason for the procedure and any discomfort that may be experienced.
Procedure (2 of 14) Procedure (2 of 14) Prepare the blood bottles and equipment required and leave on a clean and stable surface (e.g clean kidney bowl on trolley), ensuring that a sharps bin is within reach.
Procedure (3 of 14) Procedure (3 of 14) Apply a tourniquet to the upper arm a few inches above the antecubital fossa. The pressure on the arm should be between the systolic and distolic, so the veins in the arm should start to distend.
Procedure (4 of 14) Procedure (4 of 14) Palpate a suitable vein. The vein should be easily palpable, and should refill rapidly when compressed.
Procedure (5 of 14) Procedure (5 of 14) Clean the area of skin overlying the vein with an alcohol wipe. Allow to dry.
Procedure (6 of 14) Procedure (6 of 14) Remove the vacutainer needle (green) from the grey sheath.
Procedure (7 of 14) Procedure (7 of 14) Insert the needle into the plastic hub and screw into place, remove needle sheath
Procedure (8 of 14) Procedure (8 of 14) Insert the needle with the bevel upwards, through the skin towards the vein at an angle of about 30-45 degrees. Applying some traction to the vein will help the process.
Procedure (9 of 14) Procedure (9 of 14) When the needle enters the vein, a loss of resistance will be felt. Advance the needle tip 1-2mm into the vein, and reduce the angle with the skin.
Procedure (10 of 14) Procedure (10 of 14) Push the blood sample bottle, bung end first into the hub. The needle in the hub will enter the bottle, and blood will be sucked into the vacutainer. Keep in place until blood ceases to flow.
Procedure (11 of 14) Procedure (11 of 14) Use other sample bottles if required. Remove the tourniquet from the arm. Remove the blood container from the hub.
Procedure (12 of 14) Procedure (12 of 14) Withdraw the needle from the vein, pressing on the puncture site with a gauze swab before removing completely.
Procedure (13 of 14) Procedure (13 of 14) Hold the gauze swab on the puncture site for 30 seconds to one minute. In patients with clotting problems, this may need to be longer.
Procedure (15 of 14) Procedure (14 of 14) Dispose of sharps safely, and throw gloves into a clinical waste bag. Label the blood sample bottles.
Tips Tips Once the vein is punctured, the main skill then required is to keep the non-dominant hand as still as possible. Even slight movement will displace the needle from the vein. This is more of a problem if large volumes of blood are required. If you are finding this difficult, try using a Butterfly to aspirate the blood. This is a small needle with attached tubing. The needle can be fixed to the skin via the plastic Butterfly, allowing both hands to be used with the Vacutainer sheath without needle displacement. For some types of sample (notably calcium estimates), a tourniquet should not be used during blood aspiration. This is because plasma calcium is largely bound to serum albumin, which concentrates in venous blood when a tourniquet is applied, leading to an over-estimate of the plasma calcium levels. Use the tourniquet to identify the vein, place the needle, then release the tourniquet before aspirating the blood. This is more likely to be successful if the arm is below the level of the heart, allowing gravity to dilate the arm veins.
Video (Summary)
Checklist (1 of 2) Checklist (1 of 2) Explain the procedure to the patient and seek consent. Apply tourniquet to the upper arm. Select vein. Put on gloves. Clean patient s skin carefully using an appropriate preparation and allow to dry. Do not re-palpate the vein or touch the skin at the puncture site. Anchor vein by applying traction on the skin a few centimetres below the proposed insertion site. Insert needle smoothly at an angle of approximately 30 degrees. Level off needle when puncture of the vein wall is felt. Advance needle a further 1-2 mm into the vein, if possible. Do not exert any pressure on the needle. Withdraw required amount of blood using Vacutainer system. Release tourniquet. Place sterile wool ball over puncture point.
Checklist (2 of 2) Checklist (2 of 2) Do not apply pressure until the needle has been fully removed. Apply pressure until the bleeding has ceased, (at least one minute). Mix specimens well if the tubes contain anticoagulant. Label bottles with relevant details. Inspect puncture point before applying dressing (if this is necessary). Ensure patient is not allergic to dressing adhesive. Ascertain whether the patient is allergic to adhesive plaster. Apply an adhesive plaster or alternative dressing. Discard waste, make sure it is placed in the correct containers, e.g. sharps into sharps box. Wash hands.