In this episode, episode 47, I welcome back Dr. Stephen Freiberg, one of our chief residents, to discuss all you ever wanted to know about arterial lines. We discuss the indications, contraindications, complications, placement technique, and how to interpret the waveform.
Slides with figures mentioned in the podcast can be found here: Arterial Line Podcast Images
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11 thoughts on “Episode 47: Arterial Lines with Stephen Freiberg”
I was wondering, you mentioned people inserting a single lumen CVL in a brachial artery because of the length. Doesn’t this interfer with the accuracy, since the catheter should normally be ‘short, wilde and and stiff’?
Hi Nicole. That’s a great question. I would say that in my experience I don’t think it has much effect on the accuracy of the reading though in truth it would be hard to know for certain unless you had both catheters in at the same time to compare. It probably gives you a bit more dampening than you would get with a shorter stiffer catheter, but I doubt it’s very clinically significant. If you ever have a short radial aline and a long brachial aline in a patient at the same time let us know if they correlate!
First, I would like to say that I listen to your podcasts frequently and thank you for making these. I have a few comments on this episode that I was surprised. Arterial lines are placed so frequently, that it becomes routine and we can become complacent and not think of what an arterial line can tell you about the patient.
Inserting arterial lines in the radial is where the majority of A lines placed. When the patient is transferred is to the ICU, do the A Lines from OR last longer than a day or two? Could the A line going bad have anything to do with the A line being placed with the hand/wrist under dorsiflexion? Brachial A lines seem to last longer in the ICU with excellent waveforms? Also, there is always a debate in regards to suturing the A line in place? What is the practice at Hopkins? Usually A lines placed in OR are not sutured, and A lines placed at bedside are sutured in place in the institutions I visit. In the OR what are the sterility conditions that A lines are placed? I have seen from sterile gloves only and chlorhexidine prep all the way to full sterility?
NIBP’s are so frequent in the hospital now, I think there are some perceptions that NIBP’s are always accurate. However, upon further research this is what I have found about them. NIBP’s have been shown to be inaccurate in states of hypotension. With rapid succession of NIBP measuring BP’s, this can increase the BP falsely. I have done the calculation on bedside monitors when an NIBP goes off. The MAP never equals up to the SBP and DBP shown. How an NIBP calculates a BP is finding the peak flow with oscillation that is the MAP and calculates out the SBP and DBP.
Using the arterial waveform for fluid responsive. The area under the curve is also the pulse pressure. The pulse pressure is proportional to the stroke volume. For technologies that measure the area under the curve they measure the stroke volume. Stroke volume variation or pulse pressure variation has limitations that Dr. Freiberg stated. It is also contraindicated in patients with an open chest, a. fib, large amount of ectopy. If a provider is unable to use SVV/PPV because the patient does not meet the criteria, you can use the change in SV. Using a fluid challenge or a PLR and looking for a greater than 10% change in SV means that the patient is fluid responsive.
Thanks for you comments Ami. You make some great points. To answer your questions sometimes we do see a-lines from the OR stop working after a day or two but others will last weeks. I agree, sometimes when it fails it may be due to the wrist extension used in the OR which doesn’t continue in the ICU. But it also relates to clot forming and vasospasm of the artery at times which is why the brachial or femoral artery is more reliable (it’s bigger and less likely to clot or spasm). We almost never suture radial a-lines but we do suture femoral and sometimes brachial or axillary lines. We place all alines under fully sterile conditions which I recommend because why take any risk of infection?
All the best,
I completely agree about using full sterility to place any invasive line, especially an arterial line. Thanks for the reply.
First of all- wonderful podcast! I am a huge fan, and find it a very pleasant and calming way of learning anesthesia, reinforcing important concepts and making myself feel like I’m being productive if I’m just not in the mood to crack open a book.
I am a soon-to-be pediatric anesthesiologist, and thought I would comment briefly on some “pedi a-line pearls”, specifically radial and pedal a-lines in babies.
1) like in adults, but even more importantly have all your equipment not on standby, but immediately available- multiple 22G or 24G angiocaths, floppy wire out of package + ready, ultraound machine.
2) use an ultrasound, and just “float” the probe on the jelly over the artery- even gentle pressure is enough to compress the artery making it invisible on the screen. Be sure to not accidently compress the proximal arm with the hand holding hte ultrasound probe, as again gentle pressure can occlude arterial flow in baby’s who have low mean arterial blood pressure (especially sick kiddos under general anesthesia)
3) be ergonomically comfortable- table height, chair if necessary, minimize others touch the baby as fine movements of the baby’s body can make the artery a moving target, and will decrease your chance of success.
4) follow the needle tip carefully on the u/s- this takes time and practice, but unlike in adults, simply following the needle “shadow” is not precise enough to actually hit the artery. If you don’t get flash, but you see the needle tip go through + through, it usually means you’re in the vessel, and can pass a wire as you SLOWLY withdrawal the catheter and look for flow.
5) Going through and through is common-practice, as it takes an almost superhuman ability to keep the angiocath still enough to pass a wire after hte initial flash…if you even get a flash 😉
6) If no ultrasound is available, you always use a sterile audbile doppler probe,of which one is usually available in a cardiac and/or vascular OR. Just “float” the probe gently over the skin and aim your angiocath over the point of the loudest flow.
7) Stay calm, and don’t let your frustrations build. Neonatal/infant a-lines are challenging, and it is natural- just as in the hard adult a-lines, to feel frustration and allow that feeling to affect your performance. When frustrating, take a deep breath, clear your mind, and only then re-focus. (SIDE NOTE: Dr. Wolpaw, I think it would be nice to have at least a short podcast on “finding the Zen in the practice of anesthesia.” I have found that intentionally keeping calm even in stressful situations helps my performance, both mentally and procedurally, and keeps others around me equally better-apt to contribute to crisis management.)
8) Refer to institutional practices, and nurses, regarding how to best dress your a-lines.
9) As always- be obsessed with de-bubbling everything!
Matt, these are great points, thanks so much for offering the peds perspective!
Thank you for this amazing podcast ,I love it so much, thank to all yr collages.
I’d like to start using 22g and maybe even 24g angiocaths for small arteries so I don’t have another thrombosis. I can safely avoid damage to the catheter during insertion and believe small catheters can still withstand 300mmHg without fracturing. I know aspiration for blood sample will be slower. Does anyone know if the under dampening is significant? Anyone who does pedi CV and has seen accuracy of a 24g compared to NIBP?
Wonderful useful and interesting presentations. I believe your presenter is mistaken in his description of stroke volume variation. The preload goes down with inspiration due to ppv. He described it as going up along with the stroke volume.
Thanks. Depends on positive or negative pressure. With positive pressure ventilation preload goes down with inspiration. The opposite with negative pressure ventilation.