Top Tricks for Little Pricks
This is a thing about frustration. It’s a post about humility. It’s a post about annoyance and triumph that shouldn’t be treated as a victory.
It’s about cannulation.
Getting a cannula in the patient can be the most mundane, most satisfying or most frustrating part of a day at work for a kids’ anaesthetist. Cannulation is not just useful clinically. It has an excellent habit of keeping any practitioner from getting too far ahead of themselves, just when they are feeling like the supreme clinician.
Anyone who has worked with anyone else has also seen or heard lots of different tips and tricks that individuals have built into their practice over the years. Of course, if there was a single thing that worked in every single patient, we’d all do it that way.
It seemed useful to collect tips from a range of clever people to start building up a list of things that people make a point of doing when cannulation is a little difficult. Sometimes they’re really simple things. Sometimes they’re very particular. A lot of them are the setting of the anaesthetised child but there are also a few for when the patient is not already in the land of nod.
So here is a collection of tips from Stuart Ross, Justin Skowno, Gail Wong, Sue Hale, Mary Claire Avanis, Matt Hart, Sarah Johnston, Ian Miles and Andrew Weatherall, collected from their experiences spanning four continents.
Let’s go on a deep dive
1. Look everywhere
“If you can’t see a vein where you are looking, look somewhere else. You don’t have to stick it in on the side of the bed you happen to be at.” (SR)
“Sometimes when I’ve missed out, I go to look at another limb and realise there was a way better choice there. Maybe I went to the first spot because it was closer, or because it would be in a slightly better location once the patient was positioned. Those factors aren’t nearly as convenient as a cannula that’s in. So I try and remember to have a quick look everywhere.” (AW).
“If it looks like it might be difficult, spend as long you need to in identifying the best vein before actually starting your first attempt.” (IM).
“Knowing your anatomy of veins sounds obvious, but remembering what your colleagues don’t is gold. Some veins just get used less than they should. Just one example would be the vein on the inside surface of the wrist. Locally this is known as the “vein of Thirlwell” after the much celebrated Dr Jeanette Thirlwell [editorial note: some people also call it the “vein of Gail”]. It’s a good reminder to look for the less commonly used vein. (JS)
“When really pushed there are a few sneaky veins no one ever remembers. This includes those sneaky veins on the side of the big toe or on the fingers which are almost never touched by others.” (SJ)
“Don’t forget scalp veins. And remember to communicate well with the carers if you think this might end up as an option (or if you are going with that option).” (SH)
Do whatever is necessary to see everything possible
2. And don’t forget the usual suspects…
“Remember the consistent sites in kids – back of the hand over 4th metacarpal (even if you can’t see or feel it in chubby 1 year olds), the tiny but consistent and very superficial vein on the palmar aspect of the wrist (24G only), the saphenous vein, and the antecubital fossa veins in their various locations.” (JS)
“If you can’t see the vein, you can touch, palpate, poke, prod and ballot, tap, smack as much as you want, but unless it is the internal jugular vein, you are wasting your time - know your anatomy and just go for it.” (SR)
3. Proper preparation prevents poor performance
“Get comfortable – the worse your position, the lower your success rate. Sitting is ideal and preserves your back too. And set everything up, including the bandage and fresh cannulae for if you miss. This allows you to quickly move between attempts and reduces the stress of the whole affair.” (JS)
“Why is it that anaesthetists seem to pride themselves on not optimising the environment to get a procedure done? Better position improves your success rate. There’s a reason surgeons put the table in the position they need. It makes motor tasks easier to perform.” (AW)
“Particularly when cannulating the awake patient, preparation of everything you need makes a huge difference – have your extension, dressing, sharps disposal etc in easy reach.” (SH)
4. Take hold
“When cannulating veins on the back of the hand, hold the patient’s hand with a small amount of pressure from 2nd to 5th metacarpal, creating a small upwards arc/curve across the back of the hand. The slight lateral skin tension helps to anchor those mobile veins.” (IM)
“Babies and small children have loose skin and it’s helpful to pull the skin taut to minimise movement when you insert the cannula. The caveat is that stretching the skin too much squishes the veins underneath flat and in the end hinders you.” (SJ)
Hold things tight. But not this tight. .
5. Line Things Up
“Pretty often, particularly when trainees are starting, you can see that they are so focussed on their entry point the actual cannula isn’t lined up with the direction of the vessel they have chosen. So they haven’t lined up the vessel they’ve lined up. This pretty much guarantees you’ll be entering the vessel a bit oblique and be out of it pretty much the moment you’ve hit it. A a quick glance to check the whole cannula is in a straight line with the vessel can make life a lot easier.” (AW)
6. Tourniquet Tech
“In babies and infants it's easy to over-tighten the tourniquet. If the limb distal is pale and pulseless, no blood is getting into the veins and cannulation is hard. You don't need much to raise pressures above venous and it's worth checking this if nothing is coming up.” (MH)
“I always point out the over-tightened (ie: arterial) tourniquet to trainees as loosening it is important to maximise venous engorgement.” (GW)
7. Use extra eyes
“The only thing I've changed in the past many years is that if the usual suspects (hands/long saphenous) are not easily accessible for whatever reason, I will use ultrasound for the (usually untouched) forearm cephalic vein sooner than I did previously. Also, sometimes the weight of the probe is sufficient to collapse a small vein, so I make sure I have a light touch. ” (GW)
“The ‘squishing the vein with the probe’ issue can also be mitigated by a practiced short sharp jab through the skin and skin only, followed by a second move into the actual vein.” (JS)
“If using ultrasound in small humans, you can get a perfect view of a small vein, which is then obliterated by tissue distortion when you try to insert the cannula. If you make a small hole in the skin and subcutis with a sharp needle e.g. a 22Ga, then insert the cannula into this pilot hole, the problem of tissue distortion disappears.” (MH)
[Editorial note: there are many more bits of work coming on use of ultrasound for the many things. This is just the briefest nod to the idea of using ultrasound early.]
8. Clear the way
“When using a 24G cannula, consider making a separate skin incision with a 19G needle (bevel oriented to one side). The lack of skin “drag” with subsequent cannulation gives you a better chance of feeling the “pop” of cannula entering vein. (The slow flashback through these small cannulas makes the identification of timing of venous entry difficult, if the pop is masked by skin drag.)” (IM)
“For smaller patients and difficult cannulation in older folks I very frequently make a small hole in the skin that is larger than the cannula I intend to place. The lack of drag through the tissues sometimes helps by allowing the feeling of a “pop” as you enter that vein. But it also helps with keeping that vein stay at it its full size rather than compressing as the cannula approaches. You can really see the difference under ultrasound. It’s real.” (AW)
9. Short, sharp moves
“I’ve seen some people prefer to slowly advance the needle. I find that all too often the vein just seems to see it coming and shift slowly away. My success rate went up when I switched to a series of short, quick moves with a longer pause between. It works better for me.” (AW)
“When actually cannulating, practice getting through the skin quickly, but not going too far, whilst keeping the skin slightly tensioned with your supporting hand. This will reduce the chances of squashing the vein, not seeing the flashback and then wondering where all the blood is hosing from when you withdraw the supposed failure of a cannula.” (JS)
10. The Saline Trick
“Sometimes, particularly in the small veins (or small kids and small cannulas), it takes too long for that flashback to declare itself. I use this trick all the time – flick the back of the cannula off (I think this only works with a non-safety cannula). Then flush the whole needle hub with some saline. You get left with saline in the hub behind the needle. When you’re cannulating, the second you hit the vein, you see a sudden change in the saline then a thin ribbon of blood comes through. (This will sound nerdy but it’s one of those moments of quiet art in the middle of an anaesthetic). I feel like this trick has stopped me prematurely pushing on and ending out the back of many a small vessel.” (AW)
“If you are serious about seeing the flashback, prime the cannula with saline from the back wicking end, that reduces the surface tension for the hue of blood to rapidly flash back in the smallest of children.” (SR)
“For insertion of smaller cannulae, flushing the needle so that a column of saline fills the needle and hub prior to insertion means that when the bevel enters the vein, you get near instant flashback owing to the low resistance of a liquid-liquid interface compared to a liquid-air interface in a non-flushed cannula. This helps minimise the risk of not waiting long enough for some blood to come back and going through the back wall of the vein inadvertently.” (MH)
11. The Flashback Moment
“Once you get flashback (if you have not done the saline trick), in neonates and small children you are wasting your time waiting for continued growing of flashback to verify your intravenous position (like you might do in adults). Neonates and small children only have a minuscule microlitre to give back to your flashback, it’s not going to grow. The only way to know you are in, is to withdraw the needle component of the cannula and see the red hue flash between the needle and plastic cannula. If that doesn’t happen, you have either messed up and not advanced the last mm to get plastic in the vein - your attempt has failed - give up, ask for green gauze and move on - or better case scenario you have slightly transfixed and you can move onto salvaging by wire in the hub technique. (SR)
“When you get that flashback follow the standard advice to make sure you flatten the trajectory of the needle right out and advance a little to get the actual cannula fully in the vessel, not just the needle. But you can also get a bonus advance by rotating that needle in the cannula 180 degrees. Effectively the leading edge is now closer to the shallow surface of the vein and you can advance that tiny bit more without the pointiest part of the needle approaching the back wall. It’s like a bonus few millimetres of an advance.” (AW)
In a neonate - you felt a click, halted and didn’t see a flash back? Trust yourself - you are in - push forward and with no resistance, you are in. There simply wasn’t enough microlitres of blood to come back. Caveat - if you felt the wrong click, this vein is a goner. Give up asap.” (SR)
12. Fixing the transfix
“If you have transfixed the vein then pull back the cannula slowly with an appropriately sized wire in the hub to rapidly advance the wire to establish an intravenous connection the moment you get flashback … if this doesn’t work on the first go then give up. No amount of tapping, pushing, jiggling will work. Ask for green gauze and move on to the next vein. Rule number two in this situation - If having transfixed the vein you pull back the cannula with a wire in the hub, do this in one steady slow pull with wire ready to pounce. If you try pull and halt, pull and halt, pull and halt and then flashback and halt you will simply flick the plastic end of the cannula out of the vein in small chubby babies. Be smooth.” (SR)
“If you think you’ve gone through the vein in a neonate or infant, pull the needle back into the cannula whilst you steadily pull back. [Editorial note: the aim here is to have the needle inside the length of the cannula so it is providing rigidity to the plastic but not protruding beyond the plastic straw.] Otherwise you may have the joy of blood coming up the needle, but a cannula that is already out of the vein in smaller kids, with the subsequent attempt to thread it in failing miserably.” (JS)
13. Awake to good ideas (tips for the awake patient)
“In an awake, moving baby, local anaesthesia is your friend. Some intra dermal lignocaine in the dorsum of the hand or wherever else you are trying will sting briefly, but subsequently the baby is much less apt to wiggle while you manoeuvre your cannula into its desired position, making the job of you and your assistant a bit easier.” (MH)
“Set yourself up for a successful first go. Use EMLA, distraction and good positioning. There is also lots of value in thinking really hard about how you communicate and speak. There is a great video in this paper [video 2] with Dr Allan Cyna demonstrating this. Deceptively simple things like using dissociative language (‘the hand/that hand’ instead of ‘your hand’) along with general neutral language and positive suggestion might just ease your way.” (MCA)
“Consider your positioning options. One good option is positioning on the carer’s lap with the child’s arm tucked between parents arm and chest so that the hand you are cannulating is behind the parent’s back. Basically the child is hugging their carer and your attempt will be on that hand behind the carer’s back. Being in a good position does not mean forgetting distraction – your efforts there have to keep going. You will also be helped by using EMLA and being patient.
“Take time to explain to the carer and child if appropriate what’s going to happen. Expectations, how many attempts, and an escalation plan if attempts are unsuccessful are things that should be discussed. And I’d echo MCAs comments about considering carefully the language used. This communication is really important.” (SH)
The philosophical end to this post is here but the cannulation journey continues
Is that enough for now?
We can’t pretend this is an exhaustive list (though you can see a few come up again and again). Cannulation is a good example of a technical skill where there is more than one way to get it done. We could probably have listed “don’t be shy about getting someone else” too because sometimes it just needs a set of fresh eyes.
For us the best bit was hitting each other up for tips because quietly in the background we were all picking up new things to try. Which means now it’s over to you to give us more. Bring us your huddled masses of cannulation tips and tricks and teach us to be better. We’re keen.
Useful reading:
This is one of those bits on the site that is very much like the conversation you’d have with your colleagues over coffee. It’s not the spot for endless literature-based tips.
That said the very excellent Dr Mary Claire Avanis did mention this paper which includes a video with great examples of communication (video 2):
This is the blog version of these tips but we have given them a slightly more permanent pdf-style home over on this page of Practical Pearls.