Intravenous Cannulation Procedure Explained

As a phlebotomist, you have the responsibility of collecting blood samples from patients to help determine illness or otherwise. The blood collected from patients are taken to a lab where they are examined to see if there are any diseases or conditions to be worried about.

Many people are frightened of needles, and it also falls upon you to assure them that the procedure is completely safe. Not only that, you also have to make sure they are perfectly calm before you start taking blood.

Apart from sticking to the procedure, there are many other things you have to look out for when getting a blood sample.

You have to make sure not to harm the patient.
You have to ensure any nursing care the patient is receiving isn’t disturbed.
You have to collect blood correctly so it can be used for testing.
You have to label the blood samples properly and carefully.
You have to store the blood samples correctly.
You have to send the blood samples to the lab promptly.

Collecting blood isn’t just about inserting a needle into the skin. It’s about finding the right vein and successfully gaining access to it for a blood sample. The technique for connecting to a vein for access is called intravenous cannulation. The connection is made using a cannula, which looks like a tap. It’s also not just used for collecting blood; it is also needed if medication or fluids need to be sent into the bloodstream.

Intravenous cannulation is a basic clinical skill, and one that you should be really good at given the nature of your job as a phlebotomist. There is a procedure to ensure this process is done right.

Equipment Needed for Intravenous Cannulation

IV cannula
alcohol cleanser
alcohol wipe
disposable tourniquet
plaster
syringe
saline
clinical waste bin

IV Cannulation Sites

Hand

Dorsal arch veins

Dorsal arch veins are best seen on the back of the hand, but are usually larger and easier to see and palpate over the back of the wrist. Skin entry should be more distally. IVs inserted here are easily splinted and any infiltration easily spotted, so these veins are the preferred site.

The feeder veins over the dorsum of the hand in the first interspace need to be treated with respect, as it is possible to cannulate an artery here, risking loss of a thumb, or part thereof. (princeps pollicis artery). This is present in about 10% of infants. If present it is usually the sole supply to thumb.

Cephalic vein, in anatomical snuffbox

The cephalic vein is often quite large and can often be felt better than it can be seen. It is one of the veins to try if you must cannulate ‘blind’ in a large baby. Cannulas in this position tend to last quite well, making this a good secondary site. It can also be used for insertion of percutaneous central venous catheters.

Wrist

Volar aspect

Veins are easily seen on the volar side of the wrist. They are usually quite small and fragile and whilst easily cannulated, do not last well.

They are useful secondary sites, but must be carefully watched when noxious substances (eg Dopamine, Vancomycin) are infused, as they are prone to ‘burn’.

Cubital fossa

Median antecubital, cephalic and basilic veins

Median antecubital, cephalic and basilic veins are easy to hit and tend to last quite well if splinted properly. These veins are the preferred sites for insertion of percutaneous central venous catheters. These should be avoided unless absolutely necessary in any infant likely to need long term IV therapy.

The median nerve and brachial artery are both in the same anatomical vicinity and therefore vulnerable to damage.

Foot

Dorsal arch

Dorsal arch veins are small, but easily cannulated and last surprisingly well. The vein on the lateral aspect, running below malleolus, is easy to access, but must be splinted carefully and watched for infiltration.

Veins leading up to short saphenous are often good options.

Saphenous vein, ankle

The saphenous vein runs reliably just anterior to medial malleolus and is large and straight. It is easy to access and lasts well although is not always readily visualized. These veins are also good sites for insertion of percutaneous central venous catheters and should again be avoided in an infant likely to need long term IV access.

Leg

Saphenous vein at the knee

The saphenous vein runs just behind the medial aspect of the knee and is often visible behind the knee and as it curves around the top of the tibia. Access is easy and lasts well if properly splinted. However, this vein is a good site for the insertion of percutaneous central venous catheters and should be avoided if possible in any infant likely to need long term IV access.

Scalp

Scalp veins should only be used once other alternatives are exhausted. Mostly at least partial shaving of the head is required. It may take 6-12 months for hair to grow back properly, which may cause significant parental distress.

Superficial temporal vein

The superficial temporal vein runs anterior to the ear and is accessible over a distance of 5-8 cm in most babies and lasts well if secured appropriately This vein is also a good site for the insertion of percutaneous central venous catheters and should be avoided if possible in infants likely to need long term IV access.

The proximity of the temporal artery, which runs beside it, is a hazard. In small infants it can be almost impossible to tell the difference, even when the catheter has been inserted. It is important to try to identify the vessels separately, by careful palpation and by observation in a good light (in the smaller infants one can see the artery pulsate). If the catheter is in an artery, it must be removed.

Intravenous Cannulation Procedure Step by Step

You don’t just go up to a patient and ask them to stick out their arm for a blood sample. There is a process involved that you have to be familiar with. This can be a stressful time for the patient so you have to do what you can to keep them calm. After all, the collection of blood or the administering of infusions is for their own good.

Make introductions and provide explanations

Although patients can be called into a room to provide a blood sample, it’s still good practice to clarify who they are. After all, no one wants test results to be jumbled up, with one person’s sample assigned to another.

Even if the world we live in doesn’t have time for niceties, introducing yourself to the patient helps put them at ease. Since cannulation can be an uncomfortable experience, you have to let them know about it but also assure them that the discomfort will only last for a short while.

Ensure that you have all the needed equipment ready

It reflects badly on you and the establishment you work for if you are disorderly in the carrying out of your duties. Keep in mind that this is a medical procedure – an invasive one at that – which means that you have to bring out a sense of calm, not one of dread.

Examine the hands and arms to find a spot to place the cannula

Before you examine, you can also involve the patient in the decision process. You can ask them which arm they prefer to put the cannula in. After that, you can start your examination to find a vein to attach the device to.

Put a tourniquet around arm

You need access to a vein to perform cannulation. As such, it is important to actually find one. Tying a tourniquet around the arm of a patient allows you to see veins a bit better.

Insert the cannula

Once you’ve found a suitable vein, use an alcohol wipe to clean the patient’s skin then let it dry. You might want to talk the patient through as you proceed to insert the cannula into the vein. Or, if they are scared, you can tell them to look away or look at other distractions (for example, a TV).