 So first off, I want to thank you. Thank you to Deb for the opportunity to speak here. As Sanjay mentioned, I'm a graduate at Texas Heart, and I'm a very proud graduate. I'd like to thank previous instructors, and especially Terry Kareem, for the excellent education and experience that I have here. I wish all the students a future successes, and I think that Texas Heart is a great place to prepare you for a wonderful career. So today, I am going to be talking with you about recirculation and VVEC help. So I have no disclosures. I have, I will be speaking specifically about a unique device made by Transonic, but I have no affiliation with them, no financial things that I need to discuss with you. They have generously donated a few of their slides so that I'm able to talk about this device. We specifically used this for the first time during the COVID-19 pandemic, and we found a lot of interesting and useful utility to it, and I think it's worth talking about. We'll talk a little bit about VVEC mode. Of course, this is for patients that have severe respiratory failure. They're not responding to conventional modalities, proning, venting, all of that sort of thing. Their cardiac function is still intact, but we must address the hypoxemia. Recirculation and VVEC mode, it's a known complication. We want to obviously get as much blood flow from the re-infusion canula out to the tricuspid valve so that it is able to go through the normal outflow track to the patient. Indications that recirculation is occurring have historically been left up to the specialist at the bedside to determine, and we'll go over some of those techniques to be able to recognize that. A little bit about cannulation configurations. So these are just some basic ones. Of course, there are additional exotic cannulations that can be used as needed, but the first diagram A is, of course, bifemoral. B, you've got femoral and IJ, and then the last one is the dual lumen cannula through the IJ. So we'll talk a little bit about the femoral jugular cannulation. You have two single lumen cannulas. Drainage cannula, of course, is on a femoral site and then terminates in the IBCRA junction. Re-infusion cannula enters through the right IBC and terminates at the right atrium. And you can see in B where the cannulas have a small area where the infusion and the access could interact depending on, first off, how close the cannulas are and how much turbulence you might have. Here's an x-ray just showing the two tips and how it really is a very small area. And so obviously it's important to make sure that the cannulas are in the correct spot, otherwise you can visually see what kind of problem you would have. Bifemoral cannulation, two single lumen cannulas, both femoral veins are accessed. The drainage cannula is in the distal IBC so you're advancing it further. Your re-infusion cannula terminates within the right atrium and the femoral veins are large, obviously easily accessible and this is a quick way to just go ahead and get on ECMO. In addition, when we get to talk about the dual lumen cannulas, there's a little bit more technique involved. And so if you're a surgeon, it does not have a lot of experience with that. You may choose the bifemoral cannulation as a quick way to go ahead and just get on ECMO and provide support. Here's the VV cannulation with the bifemoral and you can see in the x-ray that we've got, let's see, use the mouse here. We've got the return cannula is being, is terminating right up here and then the access cannula is right here. If you can see that there. Okay, dual lumen cannulation, catheter, there's only one catheter. It's placed in the right IJ, highly utilized early on in the neonatal and infant populations but has become increasingly more common in the adult populations. As I said, there is a little bit of technique involved in the actual cannula positioning. We have to make sure that the outflow, which you can see in B, is facing the tricuspid valve so that the SBC and IBC drainage ports are not just simply sucking that return blood back into the ECMO circuit, therefore making just a circle and not really providing the support that we're intending for the patient. The drainage ports are located distal and proximal into the cannula and the re-infusion port is in the middle. Okay, and here's an x-ray just kind of showing. We've superimposed so that you're able to clearly see the drainage and then the access. Here's some examples of dual lumen cannulas. They're all fairly similar. I only have experience with two. This is typical. How the cannula will look on your patient. The MC3 Crescent and the McKay Avalon are both the ones I've had experience with and they both look very similar. You'll see there's also some additional cannulas that may be popular in other parts of the country or the world. I do not have experience with those, but from what I've seen, they operate very similarly. Specifically speaking about orientation of the cannula for the Crescent and the McKay Avalon, you can see that we have the dark blood obviously on the coming out for the access. And that is the orientation for the cannula when it is a visual inspection on the patient should be towards the bottom and then the re-infusion on the top. And the reason why is that's just a quick, easy way to hopefully the rest of the cannula that we're not able to see is pointing in the right direction because a twisting of that cannula can then change the orientation of the re-infusion port and therefore it will not be pointed at the tricuspid valve. Here's some recirculation clues. So if your patient's arterial saturation is going down, trending down, one of the things you can do, of course, is do a pre-oxygenator a sample. If that saturation is going up, that's a clue to you, a very easy clue to determine that one, maybe you're not having extraction from your patient, so that would be a separate issue. But two, if your patient is extracting, but they're not getting the chance to get all of the re-infusion blood, then it's gonna be coming back to your circuit, which will thereby increase your pre-oxygenator saturation. So that's something to look at. And you can look at that, and then you can compare that to a patient sample of their SBO2 and how different are they and what are the trends for that? So that would be a real easy way for you to determine, do I have some recirculation problems? So here's a graph that just goes over showing the change in effective pump flow and recirculation compared to the set pump flow and VV support. The main point of this slide is just to notice that if you do have a recirculation problem, increasing the pump flow and providing more flow to the patient, which sounds like that would be a good idea because I just need to get more oxygenated blood to them, actually does the opposite, because the higher flow, the more turbulence, the more likely you're to have swirling, the more likely you are to actually steal more blood back away from the patient and into the circuit. So as your increased pump flow increases, recirculation will increase linearly. Effective pump flow initially will increase the effective flow, but then it will plateau and then it will actually start to decrease. This is an idealized curve and the actual curve will vary with the catheter size and position. So if you're looking at your patient, your bedside, and you're trying to figure out, do I have a recirculation problem? Here's some of the things that you can look at. You're at your max RPMs and you have little increase in your SAO2. Your venous and arterial ECMO lines show similar coloring. Your patient's oxygen saturations remain low. Your mixed venous saturation monitoring rates high. Your patient requires a similar amount of inotropic support prior to cannulation. Your patient's nears monitor readings are suboptimal. Your arterial blood gas, PO2, remains low and your ventilator settings remain elevated on 100% oxygen. So how I've seen this occur is we start noticing patient saturations are trending down. And this can be for a number of reasons. You may have zero recirculation initially, but things change within your patient. So this is something that you need to be checking. If not every day, then every few days for sure if you see any indications because something that is going to occur, especially now that mobilizing and getting these patients up, walking, doing all sorts of things that we didn't used to do with ECMO, at least not out in the community centers, right? Is they're going to be moving and that's going to move that cannula. In addition, the patients initially might have been very large patients. They might have had a lot of volume, but now the longer they're on ECMO, we're using diuretics. We're changing how their body is, which can then change where the cannula is in relationship to where it needs to be for the outflow tract. So these are things to understand that this is fluid. You may have zero recirculation or next to zero and that can definitely change even if the cannula looks as if it is advanced in the same area that it was initially, which a lot of times, if you're going to be taking care of these patients, I like to take a picture of where the cannula is and what it looks like in the neck initially, and then I can use that as a reference over time. With the COVID patients, we were having some patients be on 12 weeks and that's a long time to have a lot of changes occur. So it's nice to have a baseline. Let's see, so those are some of the things that you can look at at the bedside. Now, if you happen to have access to this particular device, this is another tool that can help you identify recirculation and it actually quantifies it. So this is the transonic ELSA monitor. It has dual flow measurements by transit time indicator dilution theory. A saline bolus is given through the ECMO circuit to determine recirculation percentage. Flow sensors, just like our regular flow probes, acknowledge the difference in velocity to quantify the recirculation measurement. The recirculation measurement is provides the information we need at the bedside to know exactly how much recirculation is occurring. With your saline, the ELSA meter is going to detect and quantify recirculation by displaying a percentage. And you can see here that on your access line, you'll have this blue flow probe. And then on your return line, you have the red. When you do the saline bolus, it measures the amount of time and the amount of saline that actually comes back to the circuit. So your bolus will be post the blue flow probe and then it'll make it through the red, it reads it. And then once it comes back through the blue, then it's going to do a calculation and quantify that. And you can see here that the recirculation on this patient is 41%. So although I'm flowing 3.6 liters, the patient is actually only seeing 2.1 liters. That is their effective flow. Clinical relevance, the optimization of the pump flow this can help you optimize the pump flow for the best ECMO treatment delivery. So you subtract the recirculation and calculation to get your effective cardiac flow. This can help you optimize cannula positioning to improve treatment delivery. And you can identify potential low volumes. And in addition to that, you can help determine, assign a potential cardiac failure. Effective flow and recirculation with the SBC and IBC cannulas. So the amount of oxygenated blood delivered into the ECMO, from the ECMO into the heart is your effective flow. And you can see here that on this diagram, where the effective cardiac flow is reading once it's actually passing through the heart. And you can see the other red arrow is just going right back into the axis cannula. Just a second, a little technological difficulty here. I'm not able to advance. Okay, thank you. Okay, and then the measurement is achieved via dilution technology. It was introduced by Dr. Gravinsky in 1995, published in ASIO. Currently there's about 200 papers published in the fields of hemodialysis, ICU and ECMO fields with dilution technology. And so just briefly, the ultrasound velocity of saline is 1533 milliseconds and then our meters per second rather, and blood is 1580 meters per second. And that is the basis for how dilution technology works. In addition, the altimeter also gives you some additional information, your oxygenator blood volume. You might be curious, why do I care about that? I know what my oxygenator blood volume is because it's published depending on which oxygenator I use. Well, this is where you might find it useful. This is a typical oxygenator. This is what you might see bedside. We all know the techniques of how we're checking our circuits. We're using the flashlight method. We're looking for clots. We might do a de-timer test. It might tell us that there's clotting going on, but we won't know exactly how much clot is in the oxygenator. We can use transmembrane pressures and we can look at the different pressures across the oxygenator. And, but remember that measurements taking before and after don't tell you how much and also don't equate to flow. So depending on where clots might exist depends on whether or not you might actually have something in a delta P that would make you concerned. Diminished oxygenation or when post oxygenation, post oxy saturations are starting to decline, it's kind of late in the game as far as determining that you have clot in your oxygenator. This is that same oxygenator that's now been washed out and you can see there's a substantial amount of clots. There is no way to predict when an oxygenator will fully clot off, but the ELSA is a tool that we can use to help us determine how much actual volume we have and when it's decreasing. So when you initially set up this device, you're going to tell it what is the published volume that this oxygenator can hold. So it can be used on any type of oxygenator and you then do a one minute measurement and then it gets a baseline. Then what you can use as as you do your recirculations, which we were doing them on patients that we were very concerned about about once a day on patients that we weren't concerned about, it might just be requested once a week or something like that. This device is mobile, so you're able to take it from one patient and just put it to the next. But you can use a trending for your oxygenator blood volume and see, oh, I started out at 210 and now we're down to 178, what's going on here? And you can start thinking about that you might start having a clotting problem in your oxygenator so that you're able to go ahead and do changeouts in a controlled fashion that are planned. Troubleshooting recirculation. So of course, you're gonna look at cannula placement and you're going to get a chest X-ray or an echo. You're gonna confirm the security of the cannula and dressing. In fact, I highly recommend, especially in the neck cannulas that you are looking at that every shift and you're making notations. Sutures have come loose, the cannula is twisted, et cetera. Those are very important in early determination that you may have a problem. Does the cannula need a position adjustment as verified on the echo or on the chest X-ray? And what is the patient's position? These patients are awake, sometimes they're sitting up, sometimes they're walking, sometimes they're not awake, but we're moving them around to make sure that we're changing their positioning. All right, got five minutes. Changing their positioning. So this is something that you wanna be checking frequently. Single looming cannulas, of course, could be positioned too close together. Dual looming need to just be malpositioning. Identify your optimal RPMs and ECMO flow. Remember, increasing RPMs without change in flow is not optimal, it actually causes problems. You can have homolysis, which can lead to increased inflammation. You can have effects on coagulation, links to acute renal failure. You would have increased volume requirements if you just decided to go up on the flow and you can also have increased recirculation. Optimizing your ECMO flow for the best treatment, just keep in mind that one liter per minute, increased ECMO flow only adds about 200 milliliters of oxygenated blood with the remaining 800 milliliters being recirculated here. So you can see the first graph, there is no recirculation, which typically you don't see zero recirculation, but you might see 5% to 10%, and that's considered acceptable. And then you'll see, as we increase the pump flow, now we're up to 23% recirculation. And then in the last graph, we've increased the pump flow a lot, but we're already up to 32% recirculation. Consider, are you hypo or hypervolemic? The patient's volume status can change your effective pump flow. So do you need to fluid resuscitate? Do we have excessive urine output? Do we not have any urine output? Are we using diuretics? The first graph shows you that recirculation was 41% on this patient. And then after fluid resuscitation, we got the recirculation down to 8%. And that was mainly because we were overflowing with the volume that we had, so that was causing cavitation. Look at, is cardiac failure something that we need to look at? If everything with the volume appears to be okay and the position of the cannula seems to be fine, then we may start looking at that the patient's cardiac function is worsening. When there is not enough forward flow through the heart, the oxygenated blood is easily gonna get drained back into the drainage cannula, so you wanna consider an ECMO. Just keep in mind that if you are overflowing for what the heart can actually squeeze and deliver the blood, then you're going to recirculate. That blood is going to come back to the circuit. The realization of recirculation, you can quantify recirculation of VV ECMO patients with the ELSA. There will be a quicker response time by perfusionists and ICU teams. And this leads to improved oxygen delivery for the patient. Improved oxygen delivery after all is the overall goal of VV ECMO. Thank you.