Under Pressure – Hitting that Arterial Line

It’s been a while since we’ve had a tips and tricks post. Having covered things about peripheral cannulation, thoughts on central lines, insights into bag-mask work and pointers for laryngoscope use it seems like time to get the finger on the pulse. Putting in an arterial cannula can be a pretty tricky exercise. There is more than one tactic out there to make it work. So here’s a collection of thoughts from a bunch of paediatric anaesthetists that might help. Insights here come from Neil Street, Sarah Johnston, Ian Miles, Su May Koh, Sue Hale and Andrew Weatherall. Oh, and you if you care to share clever things in the comments.

The Site

“Children’s arteries are more forgiving. You can try to access radial and ulnar arteries on the same arm without fear of ischaemia. Femoral vessels are also fair game in all age groups. In terms of order of priority/safety, I’d grade it as radial, then ulnar, then femoral, then posterior tibial, then dorsals pedis, then axillary. If you really need it and you feel it’s life or death you can go to the brachial artery. The superficial temporal artery is one for the in extremis situation only.” (NS)

“My preference would be radial > ulnar > femoral > axillary.” (SH)

“It’s pretty rare that you absolutely have to have that arterial cannula in a specific location. Feel for the pulse in all the preferred sites quickly and choose the one that feels the best as your starting location.” (AW)

Positioning – You First

“Sit down and get comfortable.” (SH)

“Sit down so you are comfortable and can brace your arms/hands if you need to. Any millimetre shift may make you lose the line in a baby.” (SJ)

“Good cannulation requires control and that quickly becomes impossible if you’re holding a tensed position. Grab a seat. Relax.” (AW)

“Ergonomics will sometimes favour a particular hand for cannulation vs palpation. I am right-handed but I often use my left hand for cannulation as my finger tip sensation is better on the right.” (IM)

Positioning the Patient

“For the wrist, have a support or roll under it and then tape with extension at the wrist so the skin is taut.” (SJ)

“Have something under the wrist to allow extension and tape the hand down.” (SH)

“Access techniques are highly varied. Some strap the whole wrist down with the wrist in extension. Others use a freehand technique. Develop your own consistent technique as we all have different dexterity.” (NS)

“For the femoral artery in small babies, place a roll under the hips.” (SJ and SH)


Look, there’s lots of them. How can it even be difficult?

“X” Marks the Spot

“If by feel you can either fix that spot in your mind and stab or mark the spot. Transillumination is a good option either to mark the spot or use live in the really little ones. And of course there’s ultrasound.” (NS)

“For the wrist, feel the artery and mark it’s course with your fingernail then trace its path a bit up the wrist so you can see the direction it runs in. Then take your non-cannulating hand off the wrist so you are not compressing the artery when you insert the needle. For the femoral artery, palpate well and mark it, then remember it’s likely to be heading for the umbilicus.” (SJ)

“I like to mark it out, then go back and feel again to make sure my uncoordinated drawing matches where the pulse is. Even if it’s just offline, I still have a visual reference point I can use rather than ‘it’s at that patch of skin’ and then I use the skin markings for the cannulation phase.” (AW)

Cannulating Up Front

“Approach slowly watching for a flash back. Once you have that, drop your hand and advance in the line of the vessel watching for the continued flash. You can also rotate the bevel 180 degrees once you get the flash so that the long leading point of the bevel doesn’t head out the back wall.” (NS)

“Advance super slowly once you hit the artery and advance another millimetre to ensure the cannula tip is in the vessel before you try to slide the cannula off the needle. If the cannula doesn’t slide easily then transfix the artery and pull the cannula back slowly with a wire ready to insert down the cannula when you get blood flowing back.” (SJ)

“I’ll pretty much always try to primarily cannulate rather than transfix. Once I have that flashback it’s a slow, flat advance and a 180 degree rotation to try and get that cannula nicely in the vessel before I advance.” (AW)


“Transfixing the artery is generally a better option in little ones. Once you remove the needle come back very slowly with the cannula until there is good flow. Be sure to have a guide wire poised and ready though!” (SMK)

“I aim to transfix and find the lumen on the way back out. Rotate the bevel downwards before withdrawing (the bevel is then closer to parallel to the posterior vessel wall and you are more likely to get the flash only when the entire orifice (and entire cannula tip) is within the vessel lumen). Once flashback is achieved, try rotating the cannula and advancing it off the stationary needle. If it won’t advance easily or isn’t in the vessel lumen after advancement, get that wire ready.” (IM)

Safety Signs and Taping

“Remember to label it as arterial.” (SH) [Editor’s note: this one really matters.]

“With smaller cannulae, strap the catheter with the stylet or needle still partially in the cannula. They can kink easily at the skin otherwise. I’d also avoid just going with a  simple clear dressing (like Tegaderm for example). They aren’t strong enough to stop cannula movement.” (NS)

Sound Waves that See

“The use of ultrasound enables you to determine the position and size of the artery and almost always helps with first pass success – especially in small babies.” (SMK)

“Ultrasound provides a fantastic fall back position. If you are using it as your primary method, feel for the vessel first then mark it and confirm with the ultrasound. Not the other way round.” (NS)

“In cases where palpation is tricky I reach for ultrasound much more quickly now. I also used it to retrain my fingers and brain recently when I had a run of poor success with arterial lines. I would palpate, mark and construct a picture in my head of the size, course and depth of the artery and then follow with the ultrasound. It just helped me focus with much more clarity on what I was feeling.” (AW)


“If you strike the artery when the cannula is almost fully inserted, exchange it for a longer cannula with the aid of a guide wire. It will fail.” (NS)

“For the femoral artery in neonates I use a 24 G cannula with a 3 mL syringe attached to access the vessel and then change to a 5 cm 22 G cannula over a wire. It needs to be longer than the standard 24 or 22 G cannula.” (SH)

Patience and Time

“Put a time limit on how long you will try for. If you can’t access the chosen artery quickly go to another vessel rather than persist. After the time limit get help or do something else.” (NS)

“I usually set a time limit or maximum number of attempts and ask the nurse I’m working with to keep me to it. It stops me getting tunnel vision when it’s proving difficult and forces me to make positive decisions about how we’ll keep moving forwards.” (AW)


Is that all of them? Probably not even barely. But tips and tricks posts are to share the sort of things that people do in practice. Maybe people like you if you have a minute to share them.

It might be that one of those tips is the one that takes the pressure off when we’re trying to get that pressure monitor.



That image is from the Creative Commons area on flickr and is unchanged from Marty Gabel’s original post.

Oh, and if you liked this post,  you can follow and every time something new goes up you’ll get an email to let you know that fresh stuff is up. Have a look around on this page. It’s there.













5 responses to “Under Pressure – Hitting that Arterial Line

  1. Pingback: Under Pressure – Hitting that Arterial Line — Songs or Stories | Prehospital and Retrieval Medicine - THE PHARM dedicated to the memory of Dr John Hinds·

  2. Hi Andrew

    nice work as always. Can I ask regarding the reluctance of brachial artery cannulation is this due to concerns over median nerve injury or ischaemic complications? In neonates/ infants I worry more about the potential for leg loss with a femoral arterial line versus hand loss with a brachial line given the good colateralisation:

    There are a couple of large case series documenting this – for some reason I always remember the one from 2005 (maybe because then I was more diligent at reading journals..) by Schindler et al (Paed Anaesth 2005;15:677-…..

    thanks mate



  3. Thanks Don. I’ll go back to Neil to ask for his particular rating on that one, but for me it’s one of those ones where I’d just always been taught that the brachial and femoral are both “end arteries” but at least the femoral is a bigger calibre and the cannula is likely to take up less of the lumen. I wasn’t familiar with that series though. Good recall. Thanks for picking it up, I’ll get back to you.


  4. Pingback: What Will You Do With This Tiny Person? | Songs or Stories·

  5. Pingback: Looking Back Before Looking Forward | Songs or Stories·

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