AM I IN AN ARTERY OR A VEIN? - NICU Nuggets - Tala Talks NICU

Hello, welcome to Tala Talks NICU. Today we are doing a NICU nugget on how to tell the difference between whether you've hit an artery or a vein, whether you're doing a just a puncture or whether you're actually threading that vessel. So as usual please remember to like and subscribe and mention other topics you'd like us to talk about and go answer the multiple choice questions under the community tab. We think that they will really help that knowledge kind of stick. We mostly care whether we've hit an artery or a vein if we're actually threading that catheter. So obviously if you're getting a catheter placed inside that vessel you definitely want to know if it's an artery or a vein because obviously the substances that you put in that catheter are going to differ. Even if you're just doing a venipuncture or an arterial puncture, obviously you want to be extra certain that you're not always going to be hitting arteries. So let's go through five different ways to tell whether you have actually punctured an artery or a vein. The first way is that as you all know arteries are under much higher pressure than veins. So if you stick a catheter or a needle into an artery and then you pull back on that blood it will come out much easier and much faster than if you're drawing back on venous blood. Remember we're talking about babies here. Just like everything in medicine there are a few exceptions to this rule. So for example if you hit a really fat vein then sometimes that blood can flow out really really freely. Or you could end up not being able to get blood freely coming out of an artery. So this can kind of happen in different situations. Probably the most common is when you are creating too much pressure by pulling on normally a pretty fat syringe and so it causes the artery to collapse. So generally try to use kind of the more narrow syringes maybe the three ml syringes. If you pull too hard especially on like a big fat 10 ml syringe then that artery will collapse. This is especially true in babies with tiny arteries or micro preemies. So it doesn't take a lot for that artery to just collapse. Sometimes it isn't even really collapsing it just gets irritated by having a catheter in it and the artery itself will just spasm. So the blood doesn't want to draw out at all. In those cases you just have to give it a little bit of time and eventually the blood will start flowing freely again. The second way to differentiate arterial and venous blood you all know as well is that arterial blood is a much brighter red than venous blood. And you all know this because venous blood generally looks a little bit blue. If you look at your wrists you can see that all the veins are kind of that bluish color. So if your patient is fairly pink and healthy and their blood comes out looking really dark then it's probably venous blood. You can take point number two one step further and actually order a gas on the blood that you're drawing back on. So this is the third way to differentiate between arterial and venous blood and that is to order a blood gas. If you watched part two of the blood gas videos then you'll know that generally in venous blood the ph is lower and the co2 is higher compared to arterial blood. However because you don't really have anything to compare it to that isn't that helpful. The po2 could be helpful but again you don't really have anything to compare it to. So you could have a po2 of a hundred in venous blood if the baby's on a very high fiO2. So again it won't necessarily differentiate the arterial and venous blood for you. Another number that's also recorded on the blood gas is the oxygen saturation. Normally we don't really look at it because in most babies that you're getting a blood gas on they're going to be wearing a pulse ox probe. And as you all know the pulse ox probe will give you a continuous oxygen saturation on that baby on the monitor. So generally we don't really look at the oxygen saturation that we're given on the blood gas. But in this scenario if you're trying to figure out whether it's an artery or a vein then sending a blood gas could really help. Because if you get an oxygen saturation that correlates with the oxygen saturation on the monitor which is the arterial oxygen saturation then you know that this is an artery. So for example if you see an oxygen saturation probably in the 90s or the high 80s it's more likely to be arterial. Whereas if the oxygen saturation is in the 60s or the 70s it's more likely to be venous. This is something that we've all done a few times actually send a gas on a blood sample to check whether the PICC line for example is definitely in a vein and not in an artery. So that is a very helpful trick. So the fourth way to differentiate a artery versus a vein is the whole concept of blanching. Arteries by definition provide the surrounding area with oxygen. So if you're flushing something rapidly through an artery then by definition for a few milliseconds the surrounding areas are not going to be getting the oxygen that they need. In babies when you flush an arterial line sometimes you'll see blanching or that just brief whiteness around the path of the artery. That honestly is a very good sign that you are in the arterial system. Veins are much less likely to blanch so if you do see blanching after you're flushing then it's much more likely that you're in an artery. And the last way to differentiate whether you're in a vein or an artery is also incredibly useful and we've had to do this a few times to make sure that the PICC line that was placed is definitely in a vein. And the way we do that is by attaching a transducer. So the line needs to be actually primed and hooked up to fluids and then a transducer needs to be attached to it. A transducer measures the pressure within that line. So if you have an arterial line and it's attached to the monitor then you will see the up and down wave like pattern. So the ups represent the systole or the higher pressures that the artery is experiencing and the valleys will represent diastole or the lower pressures that the artery is experiencing. Which is why if it's an arterial line you will see a wavy pattern like that on the monitor. If there are no peaks and valleys on the monitor and everything's functioning normally, check that out, and it's just really just a flat line then it means that there really isn't any pressure differences. It's not kind of this pulsatile flow and you just have the flat line of the continuous pressure that you would be seeing in venous blood. So that's a very effective way of being able to tell whether the catheter is in the artery or the vein. So as a quick recap, the way to tell whether it's an artery or a vein, arteries are under higher pressure so you'll be able to pull back the blood much easier. Two, arteries will have much brighter red blood. Three, the oxygen saturation that you get on a blood gas from the artery will be a lot higher. Four, there will be blanching around the artery when you flush fluid. And five, if you transduce that line, you'll get a wavy pressure pattern on your monitor if it's an artery. Well, thank you for watching. Remember to like and subscribe and tell us what you'd like us to talk about next. Thank you.