On this page, we’re going to show an excellent video from YouTube from Dr Todd Sawisch that gives a clear demonstration of the use of the common butterfly needle to allow the phlebotomists to collect specimens.
As explained, the butterfly needle is ideal for making handling the equipment as simple and straightforward as possible, and also means the tape can get a more comprehensive grip to prevent any wiggling motion in the needle as bloods are collected.
The video clearly shows the application of the tourniquet in order to encourage the vein to the surface, and provide a small element of tempering to the flow of blood. The tapping action further encourages the vein to ‘show’ allowing the accurate insertion of the needle.
Both of these techniques are occasionally challenged in terms of how essential they are, so the easiest way to explain why they’re used to patients is that any (very) minor discomfort from a tourniquet or tapping of the skin is far less distressing than repeatedly trying to find a hidden vein with a needle.
In the rare case that multiple failures to find a vein occur, it is good practice to offer patients the chance to return at a later time or date to retry the procedure. That of course may not be appropriate in the case that urgent medical attention is required, and the outcome of blood tests will determine how treatments are chosen.
Note that the skin is not touched after being cleansed, to prevent any contamination before the skin is broken. Although the risk of infection is low, the best practice methods are designed to reduce all risks to patients (and clinicians) as far as possible.
Finally, you will observe that the correct sequence is to remove the tourniquet before the needle. The doctor also covers the entrance point with sterile gauze prior to extraction of the needle in order to further reduce any opportunity for infection.