Advice/tips for Cannulas

Hi I'm a 3rd year medical student and just thought I'd ask for some help from fellow students/doctors.

We are on clinical placement at the moment and I'm really keen to get hands on and practice what we've been tought out on the real world.
But I must say, one thing I've learnt is that there is a BIG difference between practicing bloods/cannulas on those mannequin arms they give you in med school and a real persons arm, where the veins are nowhere near as visible.
We had an OSCE in Yr2 (Finals one is in Yr4) but I don't think passing an OSCE actually prepares you for the real world of medicine.

Anyway I was on the wards this week and kindly asked if patients would allow me to take some bloods/try inserting a cannula.
Procedure wise it's not too difficult in terms of the steps and routine etc..
Just one bit I mess up on is when you have to actually insert the needle into the vein. It's easy to get blood/flashback if the vein is clearly visible like on most young healthy individuals, but on elderly patients or those with less visible veins it's really embarassing when you either completely miss the vein or don't get the flashblack !!!.
Obviously I apologise for causing the patient discomfort and thank them for allowing me to try and then stand in the corner as I watch the qualified nurse succeed nearly every time, still unsure on what I do wrong.

Lol the more I fail at this the more stubborn I become to succeed. I just really want to get good at this, but it's just one those things that you can't really practice without causing someone pain/discomfort.

I would really appreciate if people could share some tips and trricks they use to make sure they hit the vein nearly every time. I'm sure this is something that a lot of people including qualified doctors would struggle with.

Many thanks in advance

Don't automatically go for the ACF

Never trust a vein on vision alone, always palpate a vein. You can find veins that are a lot bigger by having a good press around some of the common areas. This is something a lot of people struggle with at first - jumping onto the first vein they see, half the time it probably is the best one you will find, but having a good check you can often find veins that are a lot better, even if you can't see them.

Now it can be quite a struggle to stab a vein you can't see, especially after you've cleaned the area and can't re-palpate (everyone does re-palpate, but you shouldn't really - and DEFINITELY NOT in an OSCE). So it's good to come up with some silly surface area landmarks. "Ok it's just below that mole", or "It's slight above that area of dry skin" this can help you be more sure when going in with the needle rather than just winging it.

Hope this helps!

Don't go for the visible veins, go for the most palpable ones. Palpate gently with your fingertips, you're looking to feel a vessel which bounces nicely under your touch.

Don't automatically go for the ACF - the dorsum of the hand and forearm can also have very good veins. It's always worth checking the houseman's vein. Lightly tap on the vessel to make it come up, or better yet, ask another student to squeeze proximal to the vessel you're aiming for, like they do in theatres - that works much better than a flimsy tourniquet imho.

Go in at a shallow angle and keep the skin taut as you enter so the vein can't "wriggle" away.

If you don't get immediate flashback don't immediately conclude it's a failed attempt and withdraw the needle. Instead try re-orienting the needle within the vessel - small changes in angle and depth can often yield a flashback and saves the patient from another poke.

Above all, stay enthusiastic, don't get disheartened and keep trying. You'll get it eventually, it just takes time and experience.

What if the patient is sent for an MRI or CT with contrast which needs to go into the ACF? Do you really want to have to waste your time (and everyone else's time) recannulating the patient and putting them through another invasive procedure?

It is far more likely that they will just need fluids/abx and it is far easier not to be in the ACF for these. The nurses and patient will thank you.

And contrast doesn't have to go through ACF. In my old trust they preferred the right arm, but that was simply due to the position of the machine. Generally they want a green, but that doesn't necessarily mean ACF.

What if the patient is sent for an MRI or CT with contrast which needs to go into the ACF? Do you really want to have to waste your time (and everyone else's time) recannulating the patient and putting them through another invasive procedure?

Lmao, so in that case then you should engage brain and cannulate a large vein in the ACF shouldn't you? So far, so obvious.

But that doesn't have to apply to maintenance fluids and standard drug infusions too. A blue cannula in the ACF is fine when you're practising as a student, but I think it's something that can be avoided much of the time as a doctor.

What if the patient is sent for an MRI or CT with contrast which needs to go into the ACF? Do you really want to have to waste your time (and everyone else's time) recannulating the patient and putting them through another invasive procedure?

So you have psychic powers to predict in 2 hours' time your reg decides to send the patient for a scan with contrast? The patient's condition could change or the team might have thought a scan would be a good idea for other reasons after they initially presented.

That's a terrible and stupid policy that I've never come across in any of the hospitals I've worked in. Contrast needs a decent sized cannula - they say green but I've used pinks multiple times - in a good-sized vein. Using the ACF for cannulation is a pain in the arse - they kink, they get sweaty and fall out, and they're a higher infection risk than other sites (my current trust has a policy that ACF cannulas must be removed after 48 hours but all others just need "reviewing" at 72). I would estimate <10% of my cannulas go in the ACF.

And if you stick a blue in the ACF for your ?ectopic I will hunt you down and destroy you.

Are you for real or are you just trying to start silly arguments? What if your patient is secretly pregnant, goes into labour and then has a massive APH/PPH and you didn't put in two grey cannulae into each ACF? Off to the GMC with you.

My sister is an A&E nurse and her trust refuses to do contrast scans through anything that's not the ACF, it's a trust policy and the radiographers will refuse to do the scan. If the patient is sent without an ACF cannula and radiographer is not trained to cannulate and/or refuses to/fails to cannulate the ACF then the patient is sent back to A&E without a scan untik tgeir ACF is cannulated, wasting everybody's time. Even if the radiographer agrees (and succeeds) to cannulate the ACF it's still a massive waste of time and puts the patient through another invasive procedure.

That is one trusts policy. My old trust preferred a green in the right arm but would settle for smaller in difficult patients.

The OP was talking about wards. Where the majority of patients will need cannulating for fluids or IV drugs. Anything that goes through a pump, you do not want going through the ACF if you can help it. The pump will stop and alarm every time the patient bends their elbow. The nurse will then spend the rest of her shift having to restart it unless the patient keeps that arm straight. If you do that in a confused patient you can guarantee those fluids will take twice as long and leave them dehydrated.

Yes it’s not pleasant having a cannula inserted but it’s hardly the most invasive or time consuming procedure. The simple fact is we are not going to base where to cannulate on the off chance a patient will need a contrast scan (the vast majority won’t). It will be the most easily palpable vein in a hopefully convenient position for staff and patients. If that’s the ACF and there are no better options, fine. But there are usually better options.

All I can say to that is when my sister does a bank shift in a ward there are always pumps beeping for 'down occlusion' where the patients bend their elbows and the nurses are constantly restarting them. It may be stupid but this trust does prefer to base decisions on where to cannulate on the chance the patient will need a contrast scan, I'm sure this can't be the only trust that does.

Perhaps those admitted via a&e. But For Doris or Fred admitted with urosepsis, or dehydration you definitely don’t need to cannulate the ACF.

P.s. how many contrast scans does your trust do? They must have money to burn and some rather lax radiologists.

They do an awful lot but they definitely don't have money to burn. They're being 'assisted' (controlled) by their neighbouring trust because they're in so much debt and their CQC ratings aren't great.