EMCrit Live Show # 1 [which is Podcast 68] March 7, 2012 by Dr. Scott Weingart is a collection of topics:
Ultrasound Guided Central Line Placement
From 4:10 to 7:20 Dr. Weingart goes over how to use ultrasound for central vein catheterization in the transverse plane.
You need start entering the skin distal to where the probe is at a 45 degree angle so that the tip of the needle arrives to penetrate the vein where the ultrasound probe is.
If you put your needle tip right against the probe then you won’t ever be seeing the tip.
So look how deep the vein is on the ultrasound screen. Let’s say it is 3 cm.
So you want to put your needle tip three cm away from the probe. And if you go in at a 45 degree angle the tip of the needle will be [end up] directly under your probe head at the time you’re going to puncture the vessel. And then you’ll be able to walk that tip into the vessel.
What follows are thoughtful comments on ultrasound for vascular placement from Dr. Weingart’s listeners and his responses:
The first question about ultrasound guided central lines was a good one and represents a common problem.
Basically there are four ways to use ultrasound to assist in placing venous lines. For all of them you should first do a scan of the area and confirm that the ‘vessel’ you want to cannulate is indeed a vessel, is a vein and is patent. Then you can:
1) blindly access the vein you’ve found
2) as above but with the probe held over the vessel insertion point so that the last part of the needle’s path is visualised, this is Scott and the listener’s technique
3) use out-of-plane needle guidance or,
4) use in-plane needle guidance.
People tend to start with the first two techniques but they’re not reaping the full benefit of ultrasound. Nearly all adult central venous lines (including PICCs) can be done in-plane with real time visualisation of the needle tip through the tissues and real time confirmation of placement in the correct vessel through visualisation of the wire in the vessel. It looks very cool to see your needle tip go the whole way down and your wire come out of the needle tip in the vessel and it impresses bystanders no end. Oh, and it’s safer. Once you learn this technique it will be your default.
The only backup technique you will need is then out-of-plane guidance and the times you might need it are small veins and arteries, for some subclavian lines and on occasion where either the patient or the probe is very large making it hard to get a good in-plane view.
Dr. Weingart replies:
In-plane longitudinal is wonderful so long as the right vessel is in-plane. As ultrasonographers gain experience, this becomes the preferred technique as you mention.
What About Bicarb in An Adult DKA Patient
From 22:30 to 25:00 A listener asks: When do you pull the trigger on bicarp in patients with DKA in adults. Dr. Weingart states that he has no expertise in pediatric DKA. [For Pediatric DKA see Episode 63 – Pediatric DKA from Emergency Medicine Cases. And here is a 2015 review article on pediatric diabetic ketoacidosis – Diabetic ketoacidosis in children and adolescents].
Dr. Weingart says that the evidence in adults is never [give bicarb]. But realistically, there is some pH [6.6? 6.7?] at which you will feel almost forced to give bicarb. But Dr. Weinberg never gives a bolus of bicarb becauese it does bad things – it makes things worse.
Dr. W says that “when I do give it, I give it in a very different way from most people. I don’t ever push bicarb.”
I mix up a bicarb drip. And I drip that in over a half hour or so. Say three amps in a liter of D5W or one and a half amps in a half NS. What you are essentially doing is making an acid free resuscitation fluid -isotonic fluid – and I run that in and you look good because you’ve given bicarb. But what you’re really doing is giving a different form of plasmalyte or lactated ringers even more basic.
I think that that is a much safer way to go. It gives time for that CO2 to get expired.