IV cannula insertion
The best way to get good at inserting cannulas is to practice, by and large it’s a feel thing, and one that you get better at as your motor-memory in your fingers improves. Like anything though, it helps to have the right technique and most of the mistakes you’ll make can be put down to forgetting to do one of the basics. The approach to getting good at cannula insertion, therefore, is to be very familiar with the basics and accept that you will miss and that so long as you stick to the basics you will get better. So I’ll go through some of the common pitfalls and tips to avoid those pitfalls.
- I almost always cannulate sitting down on a chair, it makes sense to optimise your environment and if you’re sitting down you’re sure to be balanced and in a position that is familiar and comfortable to you
- The arm should be positioned according to the vein you want to cannulate, for the cubital fossa a relaxed arm that is slightly bent is usually best; ideally resting on a pillow. In the wrist or the dorsum of the hand you should manoeuvre the arm so it is just above your lap. This may seem like a tedious point, but think about how much attention professional tennis players pay to the little bits and pieces, you want to negotiate the environment so it maximises your chance at success
- A couple of things need to be positioned next to the patient’s arm and within easy reach. These are: (1) the bung – lest blood flow all over the floor after you’ve taken the needle out, (2) the vacutainer if you’re taking bloods at the same time for the same reason, (3) gauze to place directly under the cannula access point to collect the blood that will inevitably drip between taking the needle out and attaching the bung (or if you miss and need to tape some gauze to the skin), and (4) the relevant blood tubes if you’re taking blood.
- I almost always have a paper towel or ‘bluey’ underneath the arm in expectation of blood dripping down on to the bed sheets or pillow. I find dripping blood very reassuring as it tells me I’m in the vein but having made many a bloody mess over the years and needed to ask many a nurse to change sheets I tend to be pretty particular on this point.
- The best vein is the one you can feel, not necessarily the one you can see. a easily palpable vein is always preferable to a easily visible vein
- Feel on your hand for your flexor and extensor tendons and muscles and note that at their edges they can feel a lot like a vein, you can avoid cannulating a muscle by feeling it as they flex or extend their fingers, and noting that while there is a compressible bit of tissue that feels like a vein it only has one edge whereas a vein has two. This sounds silly but it’s more deceptive than you think.
- There are veins on the anterior surface of the wrist that are usually very visible but also very small, and these are not a first choice cannulation point but some people are reluctant to cannulate them at all. If they feel good, they are a reasonable choice (but it’s an awkward position for the patient so it should not be your first choice).
- The best veins are the ones that are straight, and not tortuous and that bifurcate distal to the point of attempted insertion (this tends to anchor the vein and limit rolling), try to feel along the direction of the vein so that you are inserting the cannula in the same direction that the vein is travelling. Sometimes veins travel almost horizontal and you will miss if you insert the cannula in a strictly distal-proximal direction.
- Veins can ‘come-up’ with some rubbing or tapping, some people slap the vein to try and make it come up but this is unnecessary. The idea is to disturb the mast cell and get them to release histamine. I usually just give the vein a bit of a rub while I apply the alcohol antiseptic and thereby avoid needing to slap the patient’s arm.
- Some doctors who are very good at cannulas insert them fast, this does not mean you should, there is no added benefit from speed; do it slowly so you don’t go through the vein and end up out the other side. Advance slowly, until you see flashback in the container, advance another 1-2mm because the needle tip extends further than the cannula lumen and when the needle is first in the vein the cannula tip is not; at this point you should drop the angle of the cannula to avoid inserting through the vein and then advance the cannula lumen up the vein. If at any point you lose flashback (evidenced by the container not filling up with blood anymore or if the cannula lumen covering the needle is not red) you have lost venous access. You can try to manoeuvre the cannula to get back in but be aware that the vein may have burst. This is evidenced by a circular swelling or haematoma developing around the vein site. At this point you need to remove the needle and apply pressure with gauze as soon as possible.
More to come as I think of them. Contributions/comments/criticisms/thoughts welcome and gratefully received.