Putting a cannula in kids can be… well, an experience. Dr Andrew Weatherall has a collection of tips and tricks that might just be useful.
Cannulas. Little people. Not always a match made in heaven. At the joint I work doing kids’ anaesthesia, we often note that they are the great leveller because it doesn’t matter how special you’re feeling, you’re just one lousy cannulation day away from feeling very, very mortal.
They are sort of essential for prehospital and retrieval work though. The thing is that we know that if you’re not working in a designated paediatrics job, the chances are that the little sprocket end of the market is by far the group you see the least. Which is not ideal for gaining and retaining skills.
So short of approaching random families in the street to see if the kids have always felt like their life was missing a cannula and would they like you to help with that (and that is a terrible start-up idea, don’t do that), you have to make your best of the opportunities you have and draw on thoughts from other people.
So collected here are a bunch of things that help me get those little cannulas in. It’s not an exhaustive list of everything everyone has ever come up with of course. It’s just stuff that works in my hands that I’m sharing, partly in the hope that other clever people will chip in with suggestions in response. There must be some experts out there that we just need to poke enough to make them vomit up their wisdom.
I’m even going to leave out the “give them an anaesthetic and get them to sleep” one because it feels a little like cheating for this scenario. And for the purposes of this post I’m not going into ultrasound stuff because that’s a whole extra thing. Let’s just put on record that if you’re cannulating for retrieval give it a strong thought.
So in a “not necessarily the most sensible order” kind of way, here’s how I’d think through that whole cannulation palaver:
1. What’s my aim here?
Knowing why you’re bothering with that cannula might seem like a dopey place to start but it sort of determines a bunch of decisions that follow. If you’re in a prehospital setting and you’re thinking of the cannula to get analgesia happening, do you have options you can start with first (intranasal or methoxyflurane etc) that will treat the clinical problem in the short-term and buy you time (plus help the kid, family and you) before getting to the cannula you might need long-term?
Are you adding one as a precaution for transfer? Is that the best choice for the patient and you? If it’s not time-critical do you have time for local anaesthetic options to do their thing?
Do you need the sort of urgent access that might befit an intraosseous option, then quick resuscitation and then an attempt at an IV once there are actually veins that have actual circulating volume in them to work with?
In this setting, it might well be that the IV is exactly what you need of course. But making that an explicit step in your thinking is a good thing. It makes you really prioritise the vital steps for management of the patient.
2. What’s my limit?
This flows from point 1. How many attempts would you consider before you try something new (like a different form of access, or asking someone else to have a go)? If it’s a cannula that must be done, your limits are going to be different than if you have nothing to start with. If you’re in a retrieval, rather than prehospital setting through there might be lots of clever people who can help (or who could do it while you do things that only you can do).
Setting some sort of soft limit where you will stop and reassess does stop you getting into the hole that comes with “I have to get this in” to the point where you forget the primary needs of the patient and it becomes mostly about pride. I’ve been there. A pride hole helps no one.
I don’t think you run the risk of mentally setting up with an assumption that your attempt will go wrong by having that limit either. It’s just about keeping whatever the primary goal of care (which is almost never the cannula itself, but what you can provide with the cannula) foremost in your mind.
3. Super prep
Preparation is pretty much everything here.
And whoever is helping them obviously but mainly the patient. If you’re with an awake patient, then telling them what you’re going to do and why is a pretty important place to start. The style that people employ for this can vary but one thing I’d be pretty firm on is that you can’t win by being dishonest. If it’s likely to hurt, don’t promise it won’t. If they’ll still feel pushing (like when you’ve used local anaesthetic cream), probably warn them. Let them know if you’re going to get someone to do the work of keeping a limb still. Explain steps as you go.
If you can, choose to work in a position you find comfortable. Removing any degree of strain from your own posture just makes it easier to keep your later movements refined and precise. Not always possible, but working at the right height or even sitting down can make all the difference.
Way too often over my career I’ve gone to put a cannula in a spot because it seems convenient and later realised there was a much more accommodating vein somewhere else. There is something even more convenient than a vein that is close to where you’re standing. The vein that will actually help you out that’s all the way over there. Over that other side.
Check all 4 limbs, every time you can.
Stuff for cleaning, stuff for doing, stuff for securing. Have it all ready to go (and that includes a back-up cannula ready in case you need to move on to another attempt). Once it’s in you want to be able to have it secured as quickly as possible. And once you’re under way you don’t want to be distracted by needing to reach for anything else.
A really good clean with an alcohol swab has an additional purpose. Sometimes it highlights a change in contour of the skin as the light picks it up and this reveals a vein. Sneaky and appropriate infection control.
4. The Actual Doing
Right. The pointy end. So to speak. Not so certain about this bit? Well these are all things I do or have seen others do. Comprehensive? Probably not. For everyone? Maybe not but worth a think I reckon.
Choose your cannula
First up, examine that vein and decide which cannula you think will actually go in it. We all love a cannula big enough to rehydrate a woolly mammoth (and think how dried out those codgers would be now), but the truth of paediatric patients is that you don’t need a massive cannula to achieve good fluid loading. And you can definitely resuscitate more effectively with a smaller cannula in the vein than a bigger one in the subcutaneous tissues.
I’d even cope with a not-super-huge cannula in the cubital fossa if that’s what you need to get things rolling. At the hospital we regularly resuscitate kids without a huge cannula. It just needs a syringe and a 3 way tap (and you can actually do with most lines without a 3-way tap). Mostly it’s actually about paying attention and doing it, rather than letting it run.
Line it up
Absolutely the commonest thing I see trainees do when they are struggling is not actually lining up the cannula with the vein it is supposed to slide into. The entry point is somewhere near, but if you look at the barrel of the cannula, it doesn’t line up with the direction of the vein. Good luck with that.
Don’t focus so much on the entry point you forget the rest of the thing.
Make a hole
OK this one is probably more for the retrieval setting (and particularly for tiny ones) though I guess in principle as long as you have good sharps management you could maybe consider it for prehospital work (I’ve never done it there though). Not sure I’d try it in an awake child without some local numbing happen either.
After you choose your cannula, get a needle bigger than the gauge of the cannula. Make a hole in the skin at your entry point. Now when your smaller cannula passes through the hole you shouldn’t have the skin dragged in with it at all. You should lose all resistance at that level actually. Do it right and pretty often you’ll feel the end of the cannula pop into the vein before any visual clue like a flashback tells you that you’ve made it.
Note that having gauze handy for any small amount of blood ooze that would obscure the entry point is helpful here.
The saline trick
I think this only works with non-safety cannulae. Basically you fill the hub with saline and when you hit a small vein you’ll see a super quick flashback (even just starting with a quick change in the light in the saline). This one’s particularly useful for getting early warning in tiny veins to avoid going straight through.
Short and sharp
You probably understand that you need to come really flat to the vein with your angle of approach (by all means be at a more acute angle to get through the skin, but approaching the vein should be pretty flat).
The other key bit though is short, sharp movements forward followed by a pause. I tend to find slow advancing just doesn’t do the job in little people’s veins. It’s like the slow distortion of the tissues encourages them to roll out of the way (you can even see it on ultrasound). A sharp move forward, then a pause, then repeat just seems to work better.
You get the flashback. Victory! Except you still need to advance and you’re worried it’s a bit small that there vein. So do a really small advance. Then rotate the whole cannula (as in the needle bit as well) 180 degrees. The leading edge of the needle is now closest to the skin, and the pointy bit isn’t going to go ahead and spear the back wall. Advance a little more. Now feed off the cannula.
This trick is more well known. Once you think you’re in that vein, twist the cannula off into the vein. In bigger kids it’s probably no help but in smaller veins it does seem to sometimes help get it not to catch up on the wall of the vessel.
Wired for Not Sound
This one is not really a prehospital thing but if in a retrieval-type situation you could consider this one. Have a think about getting familiar with wires for Seldinger options. There are manufacturers out there making short wires that will feed down a 24 gauge cannula. Arrow make one that is 0.018 inches (diameter) and Cook make one even smaller (at 0.015″). When you have one of those cannulae you really want but after you feed it off it’s all gloom, a wire can rescue you.
The technique (with appropriate cleanliness and wire precautions to ensure you don’t lose it in the vein all in place) is to gently start pulling back just the cannula until you have blood freely flowing back. If you gently advance the wire up the cannula at this point it will sometimes find its way perfectly up the vein. If so, you now have an introducer to place a cannula (maybe even one larger than the one used for access).
Not a technique to try in anger for the first time without someone who has done it nearby I’d say.
It’s also worth noting that not all wire/cannula relationships are without challenges. For whatever reason a Surflo 24 gauge cannula will absolutely not allow a 0.018 inch wire through. A 24 gauge Insyte? Well they were made for each other. Go figure.
4. The Strapping
Well that’s a completely different post. I only wish someone had good tips for things like that (like say, here).
For kids cannulas there are a lot of techniques out there and lots of strong opinions about tape. My main thoughts would be:
- The tape has to be in contact with the actual thing it is supposed to hold. Sometimes I see people holding tapes tight as they put it across the cannula, thereby guaranteeing the tape only contacts the top surface and is then stretched onto the skin. Form the tape closely to the cannula itself. Squeeze it right on there to get maximum tape-to-cannula contact. Then lay it across the skin (no stretching) and put some pressure on it to get adherence happening.
- Really think hard about things like boards. If they are not adding security for that cannula, you can almost guarantee they are adding annoyance for the patient.
So there’s a start. I bet people have more I’ve forgotten or don’t even know about.
You might just find some of these tips help though. And if that’s the case you will hopefully end up not being the big prick finding it a bit of a prick to get a little prick done for a little kid.
Little kid. What did you think I was going to say?
I am not kidding about hoping people will have better tips. That’s what the comments bit is for. Go nuts. Or share the post and see if someone else has one.
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The images here were from vandys (the speed limit one) and Petras Gagilas (the tunnel thing) and used unchanged from their spot on flickr under Creative Commons.