The best kept cannulation secrets | Follow up of stroke thrombolysis case

Our belief that we are good or bad at something tends to become self-fulfilling.

“I can’t cannulate” –> Avoiding cannulation wherever possible (Ever caught yourself asking yourself “I wonder if this patient could manage with PO amoxicillin?” on a patient who is clearly septic) –> De-skilling/never skilling –> “I can’t cannulate”

I found cannulation pretty difficult at the start. I owe a massive debt to all the patients who I have poked in my journey from total crap to where I am now, culminating today in getting a pink cannula in a patient with an Hb of 5.4 needing an urgent transfusion that the critical care outreach team could not cannulate on 3 attempts. There is still a long way to go, but at least I no longer feel like I am using patients as pinboards to practice on. It feels like I am providing patients with a service. This changes my whole approach, and I can feel a difference in how patients respond.

In the interests of reducing the international patient poke count (IPPC), I will share a few pearls I have learnt. I am really keen to hear your top tips.

1. Take your time.

The bloods/cannulas I have failed have almost inevitably been when patients were anxious, or told me they were sick of being poked. This made me anxious, and made me avoid hunting around too long as I could feel their lack of patience/loss of faith in me as I cycled between the same three areas over and over, feeling obliged to poke one of the sites pretty soon.

I now engage the patient in conversation very early on in the process, and ask how they are getting on. I try to talk about non medical things as much as possible. I keep the conversation away from cannulation and “which veins normally works?” unless I really need this information.

2. The antecubital fossa really is king.

I used to give up quickly on the ACF when doing bloods or cannulas, feeling more pro if I headed down to the hand/forearm like the seniors often do. A cannula lower down the forearm is preferable for comfort if possible, but this post is about the difficult veins, and beggars can’t be choosers. A phlebotomist once taught me that every patient must have a vein somewhere in the ACF. If she is completely stuck, she goes deep into the ACF over anything that feels springy, and it often works. Bottom line: There must be a vein somewhere there.

(Just make sure you are not going near the brachial artery.)

3. Do everything you can to maximise the vein

Does fist pumping work? Does slapping the vein work? I don’t know. I just do everything that I have been taught, as there is no harm to the patient. This includes fist pumping, rubbing the vein, tapping the vein, tourniquet about 5cm above the site. I make sure the tourniquet is as tight as the patient will tolerate. I used to neglect gravity, but now I make sure that I get the vein as low as possible. Sometimes giving it a little time with the tourniquet on helps, but anything greater than 2 minutes can invalidate certain blood results e.g. calcium and potassium.

4. Triple palpation

Try this right now. Feel your ACF. Feel it lightly, with your fingertips applying virtually no pressure to the surface, but rather rolling over the skin surface. Now feel it going about 2-3mm deep, rolling your fingers to feel the veins beneath. Finally, sink your fingers in about 5mm or more. On each palpation, you build up different tactile maps of the area. You will notice that the veins have a certain depth at which they are most palpable. That elusive vein in that tricky patient has often been hiding in just one of these depths, and I would have often missed it had I palpated at the same depth throughout.

5. See it in 3D

Once you think you have found a vessel, imagine you have x-ray vision. Use your sense of touch to build a 3D image of the vessel that becomes clearer and clearer the more you palpate it. Once I am confident in where exactly the vessel is, and how mobile it is, I like to keep my gaze fixed on my “xray” vision of the vessel as I clean the area, wait for it to dry and advance the needle.

What have you discovered works?

As for the thrombolysis patient in my 24th September post, the CT reported a clearly developing infarct, with more edema than previously. No haemorrhage was identified.

Lesson learnt: An ischaemic stroke can still progress despite thrombolysis. That is so unlucky.


2 thoughts on “The best kept cannulation secrets | Follow up of stroke thrombolysis case

  1. GTN spray on the vein. We used it once on nights. We did then get the cannula in, but i’m not necessarily sure it had much impact.
    I’ve decided that there’s no correlation between a patient telling you they are difficult to get blood from, and how difficult they actually are, so I never let their ‘no one can ever get blood from me’ comments put me off.

  2. I’ve finally got the hang of cannulation. Some tips:

    1) Vein selection is the most important step – select a big, palpable vein and the battle is already won. Only very rarely will you need to just ‘have a go’ (also I would consider this unethical, since you will likely fail and just harm the patient) – you just haven’t searched long enough. Apply the tourniquet for about 20 seconds, and start feeling (your ‘triple palpation’ advice is quite useful). Only once you are confident you have felt a decent vein should you attempt it. Ignore those tiny superficial veins on old women – a grey cannula will demolish them.

    2) Bigger cannulas can actually be easier to introduce, because they are less flimsy than the pink/blue venflons.

    3) Always palpate the direction of the vein and guide your needle in exactly the same direction.

    4) The angle of insertion must be very oblique – almost parallel to the skin.

    5) Keep the tourniquet on for a bit longer than you normally do (I note your point about keeping it less than 2 mins). I would recommend applying the chloroprep, putting the tourniquet on, and waiting until its dry (takes about 20 seconds). The science makes more sense than just ‘hitting’ the vein – the tourniquet does not compress the artery, so the vein continues to fill; therefore you have a plump and stable vein to cannulate.

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