Intraoperative Hypotension with Bernd Saugel and Thomas Scheeren | ESAIC 2023

Desiree Chappell: Hello, and welcome to Euroanesthesia 2023, the annual meeting of the European Society of Anaesthesiology and Intensive Care. It's Top Med talk on the Edwards booth. I'm Desiree Chappell and I'm joined by Monty Mythen, my co-host. Hello Monty.

Monty Mythen: Desiree, great to see you. Great to be here.

Desiree Chappell: It is! Day one of Euroanesthesia. It's fun here in Glasgow.

Monty Mythen: I know it's a recurring theme since post-COVID where we say what a buzz there is and how it's like... But actually, I think this is the busiest trade exhibition we've been in in the post-COVID period.

Desiree Chappell: It's busy. It is.

Monty Mythen: Which is great.

Desiree Chappell: Yes, I know. I love it. And lots of familiar faces, lots of friends that we're seeing. It's hard to walk just down one row without seeing somebody that you know.

Monty Mythen:  And everyone has made a great effort to give lots of engagement opportunities, I think is the thing. There's lots of reasons for people to be in here looking at the amazing technologies on display.

Desiree Chappell: I think that's probably been one of the most exciting things for me is actually getting out and seeing what we could not see for a couple of years. You know new technology, new drugs, new conversations.

Monty Mythen: Not to undermine how brilliant the program is that takes place outside the breaks. Yeah, wonderful lunchtime session today that we were in. Some of your guests you're about to introduce. And I had to walk away from something I wanted to say, which is about the microcirculation, a pro-con debate about microcirculation.

Desiree Chappell: Oh, my goodness. Yeah, that is something right up your alley. Well, we'll have to dive into that a little bit later. Monty, we've had some great conversations on Top Med Talk today, numerous. Some we will be putting out tonight, some we're going to hold on and put out some teasers over the next couple of weeks. So do check those out on topmedtalk.com. We do want to take a minute and thank all of our sponsors, Monty, for helping keep Top Med Talk lights on, free, open access to the world.

Monty Mythen: Absolutely. So, we have a whole raft of sponsors now. We couldn't keep it, as you say, free, open access. But a very big shout-out, as always, to Edwards. Not only were at the moment on their booth, but they were also on the GE HealthCare booth earlier, another great sponsor. But Edwards are our original sponsor. We wouldn't be here today if it wasn't for them bravely sponsoring our first attempt at podcasting.

Desiree Chappell: They took a chance. Podcast was fairly new back in 2017, whenever you started.

Monty Mythen: Exactly. I've just checked. We've just got over 1,700 podcasts.

Desiree Chappell: Yeah.

Monty Mythen: I'm not sure if that was a great idea. If you just look at the main podcast website, you're just shy of two million downloads. I know we keep talking about the two million thresholds. If you add in the other ones, the other subcategories, we're already over two million. But we've got to get that primary one over two million, and we're just about there.

Desiree Chappell: I'll say we're on the precipice. It's happening anytime. Well, it might be this podcast that takes us over the years. It is. We are very, very close. Well, without further ado, we wanted to bring in our next guest to continue conversations that we've been having over the years about numerous studies that have come out recently. And here at ESA, we've had some great conversations as well. So happy to welcome back, Bernd Saugel. Bernd, it's so wonderful to see you again.

Bernd Saugel: Thank you very much. Thank you for having me. It's a pleasure to be here again and to join you.

Desiree Chappell: Yeah, we were sitting... So over in 2022, we were at ASA, so the American Society of Anaesthesiologist in New Orleans. So fun meeting. We got to have a good conversation there. And at the ESA in Milan, we started our conversation there where we first met.

Bernd Saugel: Absolutely. And now we're here in Glasgow.

Desiree Chappell: And here we are. So, Bernd, just really briefly, we can talk about this a little bit later. When we met you the first time at ESA in 2022, we were talking a lot about blood pressure and trying to figure out where we should be targeting blood pressures. Any more revelation that you can share with us on that?

Bernd Saugel: Well, as everybody probably knows, in the meantime, Hoyes III was published a couple of weeks ago. So, a hypotension avoidance strategy versus a hypertension avoidance strategy with an outcome of cardiovascular complications. And basically, the intraoperative management consisted of maintaining mean arterial pressure of around about 60 versus around about 80. So, two different fixed blood pressure targets and no difference in the primary outcome. Not clinically important difference, no statistically significant difference.

Bernd Saugel: But this trial shouldn't be misinterpreted. Does not mean that hypotension is not important because of course, nobody was randomized to hypotension. There was very little hypotension. As I always said, I still think that the blood pressure target should not be fixed, but personalized and individualized to each individual patient. This is why I'm happy to announce that we already started our improved trial, a large German multicenter trial in 16 centers, including more than 1,300 patients, and testing the hypothesis that personalized blood pressure management based on ambulatory preoperative monitoring compared to routine care, which usually is 65 millimeters of mercury at the lower intervention threshold, improves post-operative outcomes in patients having major surgery. We included the first over 100 patients. Two centers are already actively recruiting and all the other 14 going to join the next couple of weeks.

Bernd Saugel: We are very proud that we got that trial running. I'm very, very excited about the results that we will probably have in around about two years.

Desiree Chappell: Wow, you've been busy, Bernd. Congratulations on that. Well, good. Questions still not answered, but it sounds like we're moving in a direction where we may have more information.

Bernd Saugel: Yeah, we still don't know the magic number for each individual patient, but I still at the moment would say maintain mean arterial pressure above 65. There is no evidence that you should universally target higher pressures and what we do with patients who have chronic arterial hypertension, we would probably know more about with the improved trial.

Desiree Chappell: Yeah.

Monty Mythen: And we're not going to go into all of the detail of what we recorded you about last time about recording the ambulatory blood pressure properly and getting a real target and nighttime blood pressures and nocturnal dippers. We'll put it in the show notes to link to all those great conversations. But we've got two studies to discuss in greater detail today. One of them published relatively recently that we discussed at our lunchtime session and beyond that, and another one which is literally published, let's call it today, in the last 24 hours. So, let's take those sequentially, Desiree.

Desiree Chappell: Yeah. So, we're just to start with detect. Quite- Oh, the first one? Okay. Well, first before we dive in, I do want to introduce our next guest who's sitting here so patiently, but a friend of ours, Thomas Scheeren. Thomas, it's so wonderful to see you.

Thomas Scheeren: Thank you very much. Thank you for having me. This time in a new role, because I changed after 30 years of being a clinician and working in the field as an anesthetist and intensivist, I changed roles last year joining Edwards Life Sciences, the company we are at the booth at right now, which is dedicated to patient safety and hemodynamic monitoring. It was quite an interesting step, and I'm happy about my new role. So, first time after all these years in the new role at Euro Anesthesia.

Desiree Chappell:  Oh, yeah, that's true. Well, congratulations. Thank you. I'm sure it's been an interesting transition, but this has been your life's work anyway.

Thomas Scheeren: Yes, it is. It was a logical transition for me. As I said, I enjoy it very much. Yeah, to work with great clinicians like Bernd, no longer competing, but collaborating.

Bernd Saugel: We never competed. We collaborated and we´re friends

Desiree Chappell: Absolutely.

Monty Mythen: We've had numerous wonderful interviews with Thomas over the years as well.

Desiree Chappell: Yeah, absolutely. On Top Med Talk, you can see all those again, we'll link out. So, gentlemen, you've talked a little bit today about HYPROTECT, and that's what we want to dive into next. So, Bernd, tell us a little bit about that study. 

Bernd Saugel: So, we will start with HYPROTECT or speak about the other trials that we spoke about in the lunch symposium?

Monty Mythen: I would go for the EU HYPROTECT first, because that's been published relatively recently. Okay, perfect. Very good. And then we'll talk about the one that was published in the last 24 hours.

Bernd Saugel: Perfect. Very good. We start with EU HYPROTECT. That was an interesting study. It was a European multicenter prospective observational registry in patients having major non-cardiac surgery. It was a large observational study that we started in 2021. The aim of the study was to investigate the incidence, duration, and severity of intraoperative hypotension when you use predictive monitoring that is supposed to predict hypotension from advanced analysis of the arterial blood pressure waveform.

Desiree Chappell: Wonderful. What was the primary outcome that you were looking at?.

Bernd Saugel: The primary outcome is hypotension. Our hypothesis was that the incident's duration and severity will be low when you use predictive monitoring.

Desiree Chappell: Okay. Monty, you can jump in, because you're much better at diving into this.

Monty Mythen: Let's call us the academic snobs, are going to immediately say it's not a large multicenter, pragmatic, randomized, controlled trial.

Monty Mythen: But then you say, well, hang on a second, we've actually got enough reference data about hypotension. We can come to your own data in a second, Desiree, that everybody who's looked seems to has consistently found a large amount of intraoperative hypotension.

Desiree Chappell: True.

Monty Mythen: So at some stage you sort of have to turn around and say before we get to any alternative trial design or interventions or variability, let's do some robust evaluation to see if we just reduce the incidence of that a lot.

Desiree Chappell: Yeah.

Monty Mythen: Now to put it in context, you and your group has relatively recently reported on the incidence of IOH using a measure in the United States of America, which is an approved quality measure.

Desiree Chappell: It is.

Monty Mythen: Which is a cumulative 15 minutes. 15 minutes of hypotension below a threshold of 65.

Desiree Chappell: Yeah.

Desiree Chappell: So, we partnered with another large anesthesia group. So, I'm vice president of Clinical Quality for North Star, anesthesia large national anesthesia group in the US. Almost 3000 providers partnered with US anesthesia partners, another large anesthesia group, and we looked at 127,000 patients and for a mean less than 65 for greater than 15 minutes in that 127,000 patients, we saw 29% hypotension for those patients.

Monty Mythen: And that was and we'll come back to when we talk about the second study, we're going to talk about it was more common, if anything, in lower risk patients.

Desiree Chappell: Lower risk patients around 2 to 3 hours. We actually saw a large population or a large percentage of hypotension in our ASCs (ambulatory surgery center).

Monty Mythen: So certainly, in most people's experience, hypotension is commonly available. And we're going to talk about the time weighted average. So, we want to give that some context. The time weighted average is looking at, let's call it the area under the curve of the burden of hypotension adjusted for time because obviously the longer a case goes on for the greater the opportunity to be hypotensive. Do you have the number for the time weighted average because you want to put the results from this study in context?

Desiree Chappell: Yes.

Monty Mythen: What was your TWA - time weighted average?

Desiree Chappell: The whole 127,000 patients our time weighted average was 0.67 mmHg.

Monty Mythen: Which doesn't sound very much, but to put it in context, the reference point we're going to refer to is 0.67.

Desiree Chappell: Yes.

Monty Mythen: Okay, but what was the time weighted average for your study? Which is different in a number of ways, but the severity of the patients, if anything, is more severe patients, what was your time weighted average? Because this number doesn't make a sense to a lot of people, but we put it in context. Yours is about 0.7, for oddness sake. Yours was?

Bernd Saugel: I don't tell you yet. I tell you a little bit about the study before that.

Monty Mythen: Keep attention up. But what we have is a reference point.

Desiree Chappell: We'll come back to us.

Bernd Saugel: We will remember the 0.6. The first of all, I think I would disagree with you because regarding the trial design, at least it was large. So, I agree that it was not a randomized.

Monty Mythen: I was being provocative about this. I think it's a great trial.

Bernd Saugel: So, it was not a randomized control trial. I agree. So, it was an observational registry, kind of reflecting what happens in the real world in the operating rooms. And this is the advantage of this study design. It enabled us to include a lot of patients in a short period of time. So, we included 749 patients. So, it is large. And yeah, we included adults having non cardiac surgery, major non cardiac surgery, defined as an expected duration of surgery of more than 120 minutes. And all of those had intra-arterial blood pressure monitoring and, on top of this predictive monitoring, with this HPI technology.

Bernd Saugel: We didn't include patients having emergency surgery, we didn't include patients having atrial fibrillation. But besides of this or a couple of other exclusion criteria, we included a broad range of patients having a broad range of major inpatient surgeries. And yeah, well, all of those patients had intraarterial blood pressure monitoring, had their predictive monitoring in place. The primary endpoint was the time weighted average. Again, this is the area under a blood pressure threshold. This was 65 in our study, as in many other studies. And this was normalized or divided by the duration of monitoring simply because the monitoring time, which usually is the same as the duration of surgery, of course, differs among different patients.

Bernd Saugel: And we had a couple of secondary endpoints that we may talk about, but for the primary endpoint and now you can repeat the reference that you observed in your study.

Desiree Chappell: 0.7

Bernd Saugel: The median time weighted average minute blood pressure below 65 in the hypertext registry was 0.03 mmHg and the interquartile range was 0-0.2.

Desiree Chappell: Wow, impressive.

Thomas Scheeren: So this is substantially lower than in that reference that you gave us.

Desiree Chappell: Yeah.

Thomas Scheeren: How can you explain that Bernd? Or what is your interpretation? Why did you find such a low incidence?

Bernd Saugel: Well, now the trial design comes into play again, or the study design, of course. So, with these results, we cannot claim that using predictive monitoring causes that there is basically no hypotension. But what we can say is that in this real-world registry, more than 700 patients in centers who used predictive monitoring before. So, all of those centers and clinicians working there were experienced with using the technology. When you give that technology to clinicians who are able to use it, obviously there is very little hypotension. This may be confounded by other factors. Maybe they are very interested in hemodynamics. Maybe they are very well aware of the association between Hypotension and outcomes. This is something that we could only answer if we would have done a randomized trial. But what we take from this is that in this real-world evidence registry, the amount of hypertension was very, very low when patients had predictive monitoring treated by clinicians who were experienced with this type of monitoring.

Thomas Scheeren: So, can we put it in other words, or would you agree when I say in the hand of experienced users, the HPI technology can almost eliminate hypertension because 0.3 is close to zero, so there is very little or almost no hypertension. Would you agree with that?

Bernd Saugel: I would not claim that there is a causal relation between the monitoring and the primary endpoint of the time weighted average of hypertension. I would be descriptive here as a researcher, and I would say, given that study design in this real world evidence in the hands of experienced clinicians patients who had monitoring with this predictive technology and who were treated by those clinicians, they had very, very little hypertension during surgery.

Thomas Scheeren: And what evidence would you need to make that statement that cause a relationship between the monitoring and the reduction of hypertension?

Bernd Saugel: If you don't just want to look for an association or just be descriptive, as I try to be now, you would still need some kind of a randomized trial. It may be a randomized trial, randomizing individual patients. It could also be a randomized trial, like a cluster, randomized trial, crossover trial, where you use monitoring for three months and don't use it for another three months and go back and forth between those two clusters. But you would need to have a comparison group that is not monitored with the HPI. And if you can then show that there is a difference, then you may assume that there is a causal relation.

 

Monty Mythen: We were just we just literally finished interviewing Joyce Jung, who had a paper co published with Paul Miles, etc. today. Joyce being one of the leaders in the United Kingdom in clinical research, the head of the Clinical Trials Network there, the National Institute of Academic Anesthesia. This concept of adaptive platform trials, because this was done quickly, because it's real-world evidence, non RCT with a lot of endeavor and a lot of information out of it. But the classical pragmatic RCT to address the question has typically taken very many years.

Thomas Scheeren: And it's very expensive.

Monty Mythen: Very expensive. So, can we find a middle ground there? Do we think the possibility is there with the adaptive platform Bayesian analysis, making interim analyzes and adapting, that we can accelerate this whole process?

Monty Mythen: Has typically taken very many years.

Bernd Saugel: And it's very expensive.

Monty Mythen: Very, very expensive. Can we find a middle ground there? Do we think the possibility is there with the adaptive platform, Bayesian analysis, making interim analyzes and adapting that we can accelerate this whole process?

Bernd Saugel: Well, those new study and trial designs are fascinating, of course. We've seen that during the COVID pandemic that you can include a huge number of patients on the trial designs. You can answer numerous different questions in one patient population. As soon as you know that one treatment works or doesn't work, you can switch to the next one. So, in theory, that would also be possible for a monitoring and treatment management strategy like this one. I agree with you that a classic randomized control trial takes time, is expensive, enrollment rates are usually low. Just to give you an impression here for this registry, for this real-world evidence, it took us only nine months to include all of those patients. From the first patient into the publication of the paper, it was around about 18 months. This is something I spoke about our randomized trial before, so it will take us at least one and a half years to include those 1,300 patients. Here we were very quickly because we had motivated centers on board, but still it was an international study, five European countries, and still we were able to get all the contracting and all the stuff done and include the patients.

Bernd Saugel: It was a good example that we are able to include patients quickly when we work together in a collaborative network.

Desiree Chappell: Oh, absolutely. Thomas, did you have a question?

Thomas Scheeren: Yeah, if you compare that with a RCT that is just finished, and Monty, you were involved in that. I'm talking about that. Optimized too. How long did that take from the planning?

Monty Mythen: Five-plus years into the whole thing. Exactly. But now that was disrupted by COVID. But even despite that, once you have complex interventions in complex patients and the other challenges because they're incredibly expensive to do, you tend to reduce your number, even though that's going to be 2,000-plus patients, you tend to go for the not necessarily the upper limit of the confidence intervals, which might give you 10,000 patients. You say, well, I hope we're okay with two and a half thousand. The other advantage of adaptive platforms is the same rigor is in there, but at least you have a chance to adapt. It's a long way to go all the way to the 2,000-plus patients and then open the parcel to open the envelope, when you could say, Oh, man, we're not there yet. But if we'd only done this, if we'd only done that.

Desiree Chappell: I'm sorry to interrupt, but I have a lot of questions because this is definitely something that I'm actually dipping my toe in a little bit. Our organization and one of our facilities, we are enthusiasts for HPI and advanced hemodynamic monitoring, really. And so, when we've looked at it and we're doing interventions or starting to use it, we are very enthusiastic and follow protocol. In HYPROTECT, did you actually have a protocol that you used, or it was just people who knew how to use the monitor and they used it to avoid hypotension?

Bernd Saugel: There was no study related protocol, but because clinicians working in those centers were experienced with using the technology, I assume that they were also familiar with the secondary screen

Desiree Chappell: It's protocolized.

Bernd Saugel: Which gives you an idea of the underlying root cause of hypotension. I would assume that hypotension in patients in this registry was treated more causally, more by the root cause than in other studies or trials, where when you have a blood pressure target, clinicians tend to simply use a Vasopressor to increase the number on the screen. I would assume, but this is nothing that we can prove that in that registry, patients were treated or had causal treatment for intraoperative hypotension, simply because as part of the predictive monitoring screen, you have the secondary screen suggesting you potential reasons and causes for hypotension.

Thomas Scheeren: I can add on that because we did ask the centers retrospectively when the study was done, did you use a protocol? And if so, which protocol? As far as I remember, eight of the centers did use a co-directed therapy protocol, if you will, and four centers used actually an HPI-specific protocol. So, they did use a protocol, but the protocol differs between.

Monty Mythen: Hospital to hospital. But could you get a sense as to whether the fundamentals were the same? In other words, address, pre-load, contractility, after-load.

Thomas Scheeren: Most protocols had volume optimization as the first step, and then looking into other courses.

Monty Mythen: Because to give that some context, you do report in the paper roughly how much fluid was given.

Desiree Chappell: That's what I was going to ask.

Monty Mythen: What type of drugs were given. I've obviously read it in detail. We had another look earlier today. The amount of fluid that was given is in line with the moderately liberal message. It didn't look restrictive. It looked moderately liberal. And the use of Vasam active agents was, which we've talked about the phenylephrine pandemic, where you see phenylephrine infusions...

Monty Mythen: It goes on everybody.

Monty Mythen: ...been run to maintain blood pressure and these larger reports of no fluid and a phenylephrine infusion. As I remember, phenylephrine was relatively infrequently used compared to other vasoactive agents, and almost all the other vasoactive agents had some beta activity as well. There's a lot of nuances in there to have a look at.

Bernd Saugel: That is true and that is specifically interesting because it's a European trial. It was five different European countries, and I know from my own experience that when you travel to different countries, routine care is quite different. We always compare our interventions to routine care, but routine care varies substantially between different centers and even between different clinicians within centers. For example, in our institution, norepinephrine is the first line vasopressor that we basically use in every patient. But I know that in the US it's different and in different European countries it's different. Therefore, the HYPROTECT database will be a very valuable source to look deeper into those issues, how hypotension was treated.

Thomas Scheeren: And even the availability of drugs differs between countries. Oh, for sure. In many countries, phenylephrine that you mentioned is not available in Europe. On the opposite, we have other, for example, in Germany, we have this combined Acrinol thing that is not available in other countries.

Monty Mythen: There was one in there that sounded like a caffeine substitute. Exactly. This is the one I mean.

Desiree Chappell: Okay. Yeah. Well, what I thought was really interesting, too, is that, was it 95 % of patients actually did receive a Vasopressor? Is that right?

Monty Mythen: A vasoactive agent.

Desiree Chappell: A vasoactive agent.

Monty Mythen: The other trials like Optimize One, for example, which collected the detail in great detail from patients, you usually find 98-100 % of patients get a bit of something. So, I don't think that's that right. It was about 95 % got something.

Bernd Saugel: I don't really remember, but it may be around this year. But this is something that we see in many of our own trials too. So, for example, in trials that we do at our institution, like 100 % of the patients literally have no epinephrine because it's simply we prepare it even before induction. Like every patient has no epinephrine.

Desiree Chappell: What I thought was interesting, I'm sorry to interrupt, but to talk over you, but from my lens in the US, most people will say, oh, well, they just put neosinephrin on. So, I'm doing the right thing. I put it on everybody. Where that may not actually be the answer. We don't use Norepi very often in the US, low dose hardly at all unless you're in a cardiac center working with heart. So sometimes I get a little bit nervous about statements like that.

Bernd Saugel: It's finding the right balance between hypotension, which is associated with organ injury, you need to find the balance between the dose of Vasopressor, the amount of fluid, and you need to identify those patients who benefit from an inotrope. So myocardial depression is one major cause of hypotension. We shouldn't forget about this. Despite all the literature on blood pressure during the last decades, we should keep in mind that blood flow and blood pressure are related and that we need to treat all of those different cardiovascular components, and that we... During every single episode of hypotension, need to think does my patient need volume?

Desiree Chappell: What is the cause? Yeah.

Monty Mythen: So, we want to go into the next study in a second. But executive summary to close out, when you compared it with other studies in the space, you had by far the lowest amount of hypotension. You had the least hypotension by a long way compared to other comparators in this space, including RCTs of using HPI. And it's difficult, but your outcomes look pretty good. So that's always tricky. But if you look at your acute kidney injury rate, for example, and compare it to other published studies in this space, you've got the lowest acute kidney injury rate. Now we have to be careful with association, causation, etcetera, etcetera. That certainly sets us up to say this is a journey that we're on. This is a journey we should be traveling. We've got some important variables in there, like the amount of fluid and the choice of norepinephrine, etcetera, etcetera. But I want just to jump to, if that's okay, is to you disagree with any of that?

Bernd Saugel: Is that okay? I agree with it, yeah. I think the amount of hypotension is impressively low. We started looking at the control groups of the randomized trials on the HBI because we wanted to have a comparison, and then we noticed that we even can start looking at the intervention groups in the previous randomized control trials, and the amount of hypotension was substantially lower even compared to those intervention groups. About the reasons, we discussed this before, but I agree it was very low, and the rate of acute kidney injury is around about 9%. It's lower as that described in many other studies, but here we would need a propensity-matched analysis to really make the claim that the rate of AKI was lower than in other studies or trials.

Desiree Chappell: Fair.

Monty Mythen: So, in the interest of time, if that's all right with you, then we should jump to the hottest news.

Desiree Chappell: Hot, off the press.

Thomas Scheeren: Which is?

Bernd Saugel: The DETECT trial. We spoke about the DETECT trial before, but it was now co-published for that Euroanesthesia conference. So, it was accepted in Anesthesiology, and we spoke with the interim editors in chief, and we were able to get that published just now during that conference to be able to show those results and to simultaneously publish it in Anesthesiology. The detect trial was a trial to test the hypothesis that continuous finger-cuff monitoring compared to intermittent oscillometric monitoring reduces hypotension both during the induction of general anesthesia and during surgery in patients having major non-cardiac surgery. There were two hierarchical primary endpoints. One was the area under minute pressure of 65 during induction, and the second one was the time-weighted average. Again, the area normalized for the monitoring time during surgery.

Bernd Saugel: We randomized 242 patients. All of those patients had continuous finger cuff monitoring, so they were randomized to either unblinded finger-cuff monitoring or to intermittent oscillometric monitoring with blind finger-cuff monitoring. The results are just published now. During both periods, so during both periods. During the induction period and during surgery, patients assigned to continuous finger cuff monitoring had substantially less hypotension duration and severity compared to patients who were assigned to intermittent oscillometric monitoring, bringing us to the conclusion that continuous monitoring reduces hypotension or helps clinicians reduce hypotension.

Bernd Saugel:  We need larger randomized trials to see whether this also translates into a benefit improvement in outcomes. But in the meantime, I would say that we, as clinicians, should consider using continuous monitoring instead of intermittent monitoring in patients having non-cardiac surgery, both during induction and during surgery. You need to decide whether you need a material catheter or whether you can use a finger cuff. Yeah.

Desiree Chappell: I want to back up for just a second and talk about the finger cuff technology, because I don't know if a lot of people understand exactly how that works and how that's different than a blood pressure cuff.

Bernd Saugel: Yeah. Well, the blood pressure cuff, the basic measurement principle is oscillometry. You have an occluding upper arm cuff that you wrap around an extremity, usually the upper arm. This, by definition, gives you blood pressure in an intermittent way. So, you can cycle the measurement, of course, like every 2.5 minutes. Usually, it's done every five minutes. That is what in the US guidelines. It tells you that blood pressure should be measured at least every five minutes. It doesn't make sense to do it like every 30 seconds because the measurement per se can influence the measurements.

Monty Mythen: And it's very hard to do it.

Monty Mythen: You can't, absolutely.

Desiree Chappell: Especially if you have changes.

Monty Mythen: Those of us who have higher blood pressures may have one at home that we're encouraged to use on a regular basis, true. You hit the button, you're a bit disappointed your blood pressure is higher than you expected it to be because it hurts when it goes up the first time. And then you hit it again and then already a few minutes have passed and then you don't like the second one. So, you hit it a third time. Does that happen in clinical practice as well?

Bernd Saugel: Well, of course, but the other way around, often you don't believe that there is hypotension. So, you have an oscillometric measurements and it's lower, then you repeat the measurement and it's low, then you repeat the measurement, and you can lose a couple of minutes just trying to confirm your measurements.

Desiree Chappell: Or you don't get a measurement at all. If you're going into a hypotensive state or something like that, maybe 10 minutes before you actually have a blood pressure, right?

Bernd Saugel: That is true. But even if it works perfectly well, then you usually have a blood pressure like every three or five minutes. Well, the finger cuff, the main difference is that it provides blood pressure continuously. Those finger cuff technologies are also called vascular and loading technology or volume clamp method. The basic principle is that you have a finger cuff that has an integrated infrared light source and detector, and this can measure the blood volume that is in the finger arteries. Then this finger cuff adapts its pressure very high frequently and tries to keep the blood volume in the finger arteries constant throughout the cardiac cycle, where it would change all the time. From the pressure that is needed to keep the blood volume constant, you can indirectly derive a continuous non-invasive arterial blood pressure waveform that you hardly can distinguish from a waveform that you record with an arterial catheter.

Desiree Chappell: Were there any limitations? Personally, I've used this, so I know there are sometimes where it's not absolutely 100% perfect blood pressure cuffs on the arm or not either. What are some of the limitations that we have to worry about when you use a finger cuff and that you experienced in the study?

Bernd Saugel: Well, in the study, the number of patients in whom the measurement was not possible was very low. But in general, of course, the system requires intact finger perfusion. So that is a clear prerequisite for the measurement. So, you shouldn't do it in patients in septic shock in the ICU on high doses of Vasopressors or patients with severe cardiovascular morbidity. But those are not the patients who are the target population for that monitoring, because in those patients you would use an arterial catheter anyway. We studied this in another trial. In the awake trial, we showed that continuous inter-arterial monitoring is able to reduce hypotension compared to intermittent. But here we focused on patients who were supposed to have oscillometric intermittent monitoring. This is intermediate risk patients. In those patients, the visibility of the measurement was good. We could measure in very little patients where the measurement really was not possible. I think the strategy behind those finger cuff methods should be to replace the intermittent upper arm cuff and not to find niche indications where you could use it in patients who now have an arterial catheter. I'm still a believer in the arterial catheter, and I think that the finger cuff should replace the intermittent upper arm cuff.

Desiree Chappell: Personally, I have started to use it so much more on cases where we have a large obese population that we take care of in our facility. We're tucking their arms. It's very tough to get a blood pressure cuff when you have a surgeon leaning on it. I put a finger cuff on all those patients or someone that I'm on the fence where I probably don't need an arterial line, but it would be nice to have a continuous blood pressure line. And it has saved, again, all anecdotal, my experience, but it has saved me many times to have that.

Monty Mythen: With the Edwards technology, all the other variables are available.

Desiree Chappell: Yeah. And that's true. So, you have everything.

Monty Mythen: You have everything, so you have volume, SVR, DP, DT, and so on. Because you've now got an arterial waveform, you can have the whole lot. Is that right?

Desiree Chappell: And so many and being in a quality role and looking at the larger perspective of adverse outcomes because of issues with monitoring and technology and not necessarily having continuous blood pressure, this is very enlightening to me to see this because if we could have continuous blood pressure that was accurate, reliable, that would be wonderful to have.

Thomas Scheeren: I have a question to Bernd. Because you showed a study earlier this day in our symposium about the reliability of the upper anchor, which is still used in 95% of the cases, let's say, and I'm not sure if clinicians this study is more than ten years old that you showed, and I'm not sure if clinicians are aware of that. What you were showing is that this study showed if you compare these measurements to the gold standard being intra-arterial measurement, that you underestimate high blood pressures and you overestimate low blood pressures, which is quite dangerous. How can it be that these important results and it was not a small study, are not aware in our community?

Bernd Saugel: Well, confidence in measurement systems is a complicated issue, and sometimes the method that is around for the longest is considered the most reliable. So, everybody is just used to it. And the study you are referring to is indeed, it's more than ten years old, and it's a retrospective method comparison study in more than 15,000 patients having surgery. And they compared intra-arterial measurements with a catheter to the simultaneously oscillometric ones, and they show that there is the risk of substantially overestimating low pressures. And this is something that you can see in clinical practice basically every day, because everybody has seen the situation that you place or someone places an arterial catheter, you induce anesthesia, and then the blood pressure on the monitor from the arterial catheter that you just inserted is very low. And people won't believe it. And they say, okay, I'm going to check this, and I will do an oscillometric measurement. And then let's say the mean arterial pressure from the arterial catheter is 35, and from the oscillometric cuff, it is 55. And then people feel reassured that there's no hypotension. This is not true. The real blood pressure from the intra-arterial catheter that you just inserted is 35, and you just overestimate it with your oscillometric measurement.

Monty Mythen: We're getting the flashing red lights.

Desiree Chappell: Oh, is it time?

Monty Mythen: Yeah.

Desiree Chappell: All right. Well, anything else, Thomas, Monty, that we need to cover on those.

Monty Mythen: We could talk for hours about this.

Desiree Chappell: I know. Every time.

Thomas Scheeren: We will. Interesting topic. And relevant for patient care.

Desiree Chappell: Yeah, absolutely. Patient safety. I mean, that's what I keep do.

Bernd Saugel: We have the time for 20 more seconds?

Monty Mythen: Do it.

Bernd Saugel: Because when we speak about oscillometric measurements, what we always forget, and I don't mention it because it means diving very, very deep into this technology. We don't even know what those systems do because the algorithms are usually proprietary. So, if we say we compare oscillometric to anything, we basically don't know what oscillometry is. So, you would really need to say we used this type of monitor with this type of cuff and this software version, and then we could make a claim that it's good or it's bad. So, it's a black box. We don't even know what those monitors do.

Monty Mythen: It's a blacker box, isn't it?

Desiree Chappell:  It's so interesting. If you look at the mean that is on the blood pressure cuff versus what's on any other technology.

Monty Mythen: Exactly. We'll do that next time.

Desiree Chappell: We will. All right.

Thomas Scheeren: Excellent.

Desiree Chappell: Bernd, it's wonderful to talk to you so much. Thank you so much. Thomas, thanks for joining us today.

Bernd Saugel: Thanks.

Thomas Scheeren: It was my pleasure.

Desiree Chappell: And thank you for joining Top Med Talk here at Euro anesthesia 2023. It's been a pleasure, gentlemen. Enjoy the rest of your day. Enjoy the rest of your time here at the meeting, and we'll talk to you soon. Cheers.

Bernd Saugel: Thank you.

Thomas Scheeren: Thank you. Thank you. Bye bye.

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