Paramedics Course – Cannulation


Micro-lecture by the Australian Paramedical College

In today’s micro-lecture, Australian Paramedical College Hon. Snr. Lecturer Sam Willis talks about the skill of peripheral cannulation.


In today’s micro-lecture, we’re going to talk about the skill of peripheral cannulation. Now, peripheral cannulation is something that you guys will have a play around with at the clinical workshops, so you’ll get lots of practice. From the paramedic’s perspective, you need to be thinking about why you would be undertaking the skill in the first place. So think about the different occasions when you would need to put a needle in. Now by today’s standards, you need to be able to justify your actions. The answer to when you would introduce a cannula into someone’s vein is only when there’s a direct medical need. No longer do we do precautionary cannulas on our patients, but instead replace a needle into our patients, if there’s a direct need, for example, if they’re in significant pain, the patient’s in cardiac arrest and they need fluids or other drugs, or any other situation where there’s a drug that you can actually give.

Historically, it never used to be that way. You used to be able to calculate just in case the patient went unconscious and became unwell. When it comes to the actual skill, you have to think about the size of the needle. That’s one of the most important things. Now, have a look at this here. This cannula, this needle that’s here, is a green one. So the green colour itself denotes a certain number, a certain gauge. Now, most cannulas, most ambulance services will have a 14 gauge as the largest one. Then as the number goes up, the size of the cannular goes down, so 16 gauges are grey, and then the 18 gauge is the green. We’re going to have a look in a moment or the different colours and the different sizes. Now, the reason we have different colours and different sizes is all to do with the flow rate, the amount of drugs, the amount of fluid we can administer over a certain period of time.

When you actually pierce a patient’s vein, and you pierce through the vein using the needle, the blood itself rushes up the catheter and into this flash chamber. Actually, that’s one of the ways that you recognise that you’re in the right place because blood will fill the flush chamber. Now, here are the different sizes. Now, notice how I said 14 gauge is usually the largest one. This used to be a brown colour, but now it’s orange. That’s fine, and you can give 240 millilitres per minute, so that really is a very large diameter. Whereas, most ambulance services in terms of the smallest needles, stop at the blue, and they say baby blue, 22. So as you can see, the flow rate goes down.

Violets a pretty small one, 26 gauge, 13 millilitres per minute. Remember what a millilitre looks like. We have 20 millilitre syringes that you’ll have a play around with at the workshop. In one minute, it can take a yellow needle, one minute to administer 20 millilitres of fluid. So let’s go through this from the top down once again. So 240 millilitres really is your patient who’s had some kind of trauma, and requires a large volume of fluid. Again, these two could probably be reserved for patients who have had trauma. The 18 gauge generally is is your general care needled? Ask most paramedics. It’s very much a personal clinical decision. Most paramedics will give that patient an 18 gauge, but of course, it very much depends on the size of the patient and how healthy the veins are Then these are reserved for children and elderly.

The micro-lecture on cannulation.

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