Improving your blood taking skills

Daniel Sado, who is an experienced phlebotomist, gives some tips

As future doctors you can all expect to take venous blood (venesection) from many patients during your career. As junior doctors you will probably take blood nearly every day. But venesection is not given any priority at medical school. The adage of "see one, do one, teach one" could not be applied to a better procedure. Unfortunately, you need only to look at the arms of patients on hospital wards to see the results of poor venesection technique. Many of them will have extensive bruising. Although some of this bruising is inevitable, there are ways to try to limit it.

I was taught to take blood in an outpatient clinic in my local district general hospital (this is an excellent place to learn because the patients are "well" and so have good peripheral blood supply). After this, I worked as a phlebotomist at Northwick Park Hospital for three months in an outpatient clinic where I took over 2000 blood samples. For the past two years, I have been employed as a venesector by the medical directorate at Southampton General Hospital.

My tips are not evidence based because there is little in the published literature about venesection technique. What I aim to do is to make some suggestions that I have found useful in improving my own venesection technique that you may wish to try out yourselves. I have assumed that everyone who reads this article has had some experience of taking blood.

Introducing yourself to the patient

Always shake hands with the patients and ask them if it would be all right for you to take blood. If the hand is very cold ask the patient to open and close it a few times to try to increase the peripheral blood flow.

If the patient seems to be very nervous, use a butterfly needle as this is shorter and so looks less intimidating (see below).

If the patient is unconscious, get a helper to hold his or her arm down to ensure that it does not jerk up when you insert the needle.

Where to take blood from in order of preference

Antecubital fossa of the arm: the veins here tend to be big and stable. You should be able to get blood from about 90% of your patients at this site.

Forearm or back of the hand: it is particularly worth checking to see if the patient has a good houseman's vein (fig 1).

Feet: a good vein can often be found anterior to the ankle.

Central line: seek more experienced help before doing this.

Peripheral venous line: seek more experienced help before doing this.

Femoral stab: insert a needle just medial to the femoral pulse in the groin.

Vacutainer, syringe, or butterfly?

Vacutainer

The advantages are:

• No blood spilt.
• Decreased chance of needlestick injury.

The disadvantages are:

• No flashback of blood to tell you when you are in the vein; therefore you are reliant on feel.
• You can use only a 21 gauge green needle (see below).
• If the vein is missed much bruising will often occur if you probe around.
• The pushing force required to insert the vacutainer blood bottle on to the needle may cause the needle to be pushed through the back wall of the vein. Therefore it is vital to keep the needle still when using this method.

Figure 1: The houseman's vein

Syringe

The advantages are:

• Choice of needle sizes.
• Flashback of blood into the syringe can be seen when the vein is penetrated.

The disadvantages are:

• The pulling force on the plunger needed to withdraw the blood may cause the needle to move.
• There is an increased chance of needlestick injury compared with the vacutainer method.
• Sometimes a small amount of blood will be spilt when the needle is withdrawn from the skin.

Butterfly

The advantages are:

• It is useful in a nervous patient because the needle looks smaller (even though it is still 21 gauge!).
• It is useful for the nervous operator because the needle does not need to be held still once it is in the vein.
• It is useful on the back of the hand where there is nowhere to rest your supporting hand against for the other two methods.

The disadvantages are:

• Same as the second and third disadvantages of the syringe method.

Which needle to use?

Most operators use the 21 gauge green needle. You can use the smaller 23 gauge blue needle with the syringe method.

Blue is useful because (a) its smaller diameter will cause less damage to the vein. Therefore there will be less bleeding and bruising after venesection--this is particularly useful for patients on anticoagulation treatment--and (b) it will cause less pain to the patient.

The main disadvantages are that blood will come back more slowly and there will be a slightly increased chance of haemolysis.

How to make the procedure less painful for the patient

• Use a shallow angle (about 10 degrees) to give you more margin for error (fig 2).
• Insert the needle as quickly as possible to minimise the pain felt as the needle penetrates the skin.
• Make sure that you pull the skin tight before inserting the needle, or else the vein may move and you will find it more difficult to penetrate the skin, particularly in patients with loose, fragile skin.

Figure 2: Correct approach

After the procedure

• Place cotton wool over the venesection site.
• Apply pressure only to the cotton wool after the needle has been withdrawn from the skin.
• Press down on the cotton wool firmly to encourage the vessel to stop bleeding quickly.
• If you get the patients to press down on the cotton wool, encourage them to press as firmly as possible on it.
• Final thought: remember that practice makes perfect.

Daniel Sado, fourth year medical student, University of Southampton, and venesector, medical directorate, Southampton General Hospital