Venepuncture

The process of entering a vein with a needle. When not specified, the main purpose of venepuncture is to obtain blood for testing, but venepuncture is also required as a route for venous access.

See also paediatric venepuncture

Contents 1 Equipment 1.1 Needle, Syringes and Tubes 2 Preparation 3 Method 4 Troubleshooting 5 References

Equipment

Needle, Syringes and Tubes

The simple combination of needle and syringe is discouraged as this method involves more handling of sharps, especially when blood needs to be distributed into several different containers. When blood is drawn using a needle, remove the needle before putting the blood in the bottles. With Vacutainers, remove the cap, losing the vacuum, and after filling them replace the cap. If those samples would usually be sent by pneumatic tube the cap may need additionally securing, or perhaps are better despatched by hand.

To address this safety aspect, several proprietary systems exist. The most commonly used systems are the Vacutainer® and Monovette® systems. Once a single needle is inserted into a vein, different blood tubes can be sequentially attached to the needle, reducing the need to handle both blood and needle. Additionally, many of these systems can use 'pre-vacuumed' tubes that draw a fixed amount of blood when attached to a needle.

Different tubes contain different additives depending on what test is required. For a full blood count, tubes often contain potassium EDTA, which stops the blood from coagulating by chelating calcium. Many companies produce a coloured wall chart. You may find one in the store room for syringes and needles.

Preparation

• Equipment. Needles, syringes/barrels, blood bottles, cotton gauze. 1" squares of isopropyl alcohol pads are useless to stop bruising. Always take more than you will need to allow for loss of vacuum or dropping a tube or deciding you want another test. Carry it in a small tray.
• Tourniquet. As simple as possible. Velcro is easier to release than metal clips.
• Patient details. Sticky labels, the relevant form(s) and a pen to fill them in.
• Sticky tape to hold the cotton wool on for half an hour or so. 1cm elastoplast discs are useless for stopping bleeding. Microporous tape is sticky enough and easy to remove.
• Sharps box. Some have a fitted tray to leave you more hands.
• Nursing trolley. Some purists will insist on this. It gives you more room to carry stuff.
• Alcohol gel to wash your hands, particularly if there is infection in the ward or clinic.
• Gloves. Dealing with adhesive tape while wearing rubber gloves is not conducive to maintaining an even temper. Tear off a few 4-6 inch lengths and stick one end to the trolley for quick release when you need them. Do this before putting on your gloves.

Some people use an antiseptic alcohol swab (often propanol rather than ethanol) to prepare the skin. This may have benefit when taking blood cultures or in peripheral venous cannulation, but whether this influences infection rates in straightforward venepuncture is unclear.^[1]

Method

• Introduce yourself to the patient and check his/her name. This is common politeness and it means you take blood from the right person. It helps the patient to relax which makes the veins constrict less from their adrenaline
• If the room or patient is cold or the patient is known to have "poor veins" a warm moist face cloth placed over the vein for a few minutes can help it dilate.
• Apply the tourniquet firmly but not tight. Clean the skin if need be.
• Select your vein. Deeper ones are less obvious and are oftern better felt than seen. They are better supported by surrounding tissues which makes them more stable.
• Palpate the vein with the pad of your finger. A satisfactory vein feels "bouncy" like a soft bicycle wheel. A hard tender one may well have a clot in it so select another vein.
• Hold the barrel in line with the vein with the point of the needle next the skin at an angle of 20 or so degrees and push confidently into the skin. Once you are sure that you are in the vein then put the relevant bottles into barrel one after the other. If you are concerned that you may not get enough blood be sure to fill the most important bottle first.
• Once you have all the blood you need, remove the tourniquet, press a cotton wool ball over the site and withdraw the needle, putting it into the sharps box immediately.
• Put a strip of tape over the cotton wool. Bruising seems less likely if the patient can hold the limb up above the level of the heart for a minute or so.
• Some folk will take the cotton wool off and poke at the puncture site. You may have to tell them that this means the clot has to start from the beginning again and the bruising will be worse.

Troubleshooting

No flashback 

missed vein, or very mobile vein. Flashback does not occur with the Vacutainer system.

Haematoma 

The needle may have punctured vein or torn the wall or come out of vein allowing blood to seep out. You may get just that bit more blood that you need. You probably won't. Apologise and pick another vein.

Blood stops flowing 

needle may have come out of vein, or gone too far through other wall of vein. The vein may have gone into spasm so just wait some seconds and the vein may relax. It may be that the needle is in the vein but the suction from the vacuum has pulled the wall of the vein over the bore. Gently rotate the barrel and you may feel or hear a slurping as the vein wall comes free and blood flows. If you feel you may be too far in or only partly in push gently away from you. You can always withdraw a little from too far in. If you pull the needle right out the vein you are unlikely to get it back in.

References