Central Line

Episode Number: 128

Episode Title: Subspecialty: Perioperative Strokes and Thrombectomy

Recorded: April 2024

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VOICE OVER:

Welcome to ASA’s Central Line, the official podcast series of the American Society of Anesthesiologists, edited by Dr. Adam Striker.

DR. ADAM STRIKER:

Welcome to Central Line. I'm Dr. Adam Striker, your editor and host. I'm excited to welcome two guests to the show today. Dr. Paul Picton will share some information on perioperative stroke, and Dr. Matt Whalen will speak to the topic of thrombectomy for stroke. Both of our guests are members of SNACC, the society for Neuroscience in Anesthesiology and Critical Care, and both have expertise on this topic, so I'm looking forward to learning from both of them today. Welcome to the show.

DR. MATTHEW WHALIN:

Thanks. I'm happy to be here.

DR. PAUL PICTON:

Yeah. Me also. Thank you so much.

DR. STRIKER:

Well, let's start off as we usually do with brief introductions. Do you mind both telling our listeners a little bit about yourselves and your practices?

DR. PICTON:

Sure. Well, firstly, thank you greatly for the invitation to be here today. And thank you to all of the listeners. I very much appreciate the opportunity and look forward very much to the discussion. So essentially, I'm a hepatobiliary and liver transplant anesthesiologist from the University of Michigan. And for most of my career, I also practice vascular anesthesiology. And it's, um, really related to my clinical practice that I developed an interest in cerebral blood flow, cerebral oxygenation, cerebral monitoring, particularly as it relates to cerebral hypoperfusion. And more recently interest has broadened somewhat to include perioperative stroke in general. Um, I became a SNACC member just last year, and really, because I believe my interests can find a pretty good home in this society. Uh, so despite the full disclosure that I'm not a neuro anesthesiologist, I'm really excited to be involved, to learn from SNACC members, and look forward to be a participant in that society.

DR. STRIKER:

Dr. Whalin?

DR. WHALIN:

I'm Matt Whalin, I'm an associate professor at Emory University in Atlanta, and I practice at Grady Memorial Hospital, which is a very busy stroke center doing over 300 thrombectomies a year. Um, and so stroke has been kind of my, uh, area in Neuroanesthesia since I began, but I've been involved in SNACC for a long time, and it's a tremendous organization. And like Paul said, a really big tent, um, that accommodates people with all kinds of interests that intersect with the brain. I've been fortunate enough to work with snack on some of their stroke guidelines and a consensus statement that we put out about stroke anesthesia during thrombectomy during the Covid pandemic. And just really excited to be here today and talk about this important topic.

DR. STRIKER:

Dr. Picton, I want to come to you first. Stroke is devastating for patients and families, and the cost is enormous. I want to remind listeners of why this topic is so important. Do you mind speaking to that?

DR. PICTON:

Yeah, I most certainly can. Um, firstly, stroke is certainly devastating. Injuries to relatively small areas of the brain cause marked disability or can cause marked disability, which is oftentimes permanent. And of course we have no way to fix that damage.

My own first hand account really pertains to my own father, who had a stroke before last Christmas, and he developed a dense, hemiparesis marked, expressive dysphasia and safe swallowing. So he became rapidly bedbound. The hemiparetic limbs swelled. He required intensive inpatient nursing care. And this was really for all his basic activities of daily living. And so he lost an awful lot of dignity, also suffered recurrent aspiration events, developed aspiration pneumonia. And it was pretty heartbreaking, I think, for him and and for us as a family and we try to figure out decisions about, do we do we place a peg tube for feeding or continue with at risk oral nutrition in the hope of neurological recovery? And this is in someone who was becoming very rapidly, very, very frail and in whom, you know, communication was very, very difficult. Um, so this was a, you know, an expensive event and ongoing care outside of the hospital, uh, required lots of resources and so expensive and devastating.

Um, if we look at the national picture, the projections for cost are really quite striking. Also, by 2030, the annual cost of stroke care is projected to increase to a whopping $240 billion in the US annually.

And of course, we're here to talk about perioperative stroke. And if a stroke does occur in the perioperative setting, it is also certainly equally as catastrophic. Hospital stay is prolonged. Relative mortality is increased by up to eight times. In fact, the outcome of perioperative stroke is worse actually than a stroke occurring in the community. Why? This is I think is multifactorial, but it's it's certainly difficult to diagnose in the perioperative period. The clinical features may be confounded by the recovery event from anesthesia and pain, pain medications, immobility. And so, um, one really needs to be very clinically vigilant to detect this. And, uh, most of the available guidelines do rely heavily on clinical vigilance in the perioperative period to detect stroke. Although approximately 90% occur within 72 hours following surgery, many occur much later. And this may have include the post discharge period, which does complicate detection. So it's a really important subject and there's much work to be done. Uh, currently prediction, detection, prevention -- they all remain problematic. I think also in no small part because we don't have a, you know, a great way to monitor the identification of modifiable risk factors. And tailoring anesthetic choices to individuals to help reduce the incidence of perioperative stroke is kind of a, I think, a a hope for the future. I have optimism, but it's certainly not exactly a reality for today.

DR. STRIKER:

I really appreciate you sharing your story. That must have been so hard for you and your family. I think your response spoke to both the personal cost and the economic costs of of something like this. And as you say, we want to zoom in on perioperative stroke. Can you remind our listeners how perioperative stroke is defined, and perhaps remind them of the various types of perioperative strokes and how common they are?

DR. PICTON:

So I think a perioperative stroke is defined similarly to, you know, normal stroke, as any embolic, thrombotic or hemorrhagic cerebral event with motor, sensory or cognitive dysfunction which lasts at least 24 hours. And specific to the, you know, the perioperative relative diagnosis, it has to occur either interactively or within 30 days of surgery. So that's kind of a basic definition. Most relative strokes are ischemic. And in patients undergoing noncardiac non-neurological surgery, there's a reported incidence that's somewhere between 0.1 and 1%.

Now these are overt strokes. These overt strokes are clinically apparent. But also of great concern is covert stroke. And covert strokes are not apparent and detectable as of now, only really by advanced imaging. So the the best exemplar of this is the, by far all the data really comes from this study was a study called the Neurovision study. So it's important. It was a multicenter, prospective study including over 1000 subjects. And the the investigators conducted MRI evaluation in this group of patients who were all over 65 years of age following noncardiac surgery. And they revealed a staggering, I think, 7% incidence of covert stroke post-operatively. So these are not, you know, clinically obvious.

Specific risk factors were not identified. And we still don't really know, I don't think, exactly what this means, but the risk of covert stroke is certainly higher following surgeries with higher risk of overt stroke. For example, carotid revascularization or cardiac surgery. And covert stroke is certainly not benig. There is an increased incidence of postoperative delirium. And it's also a cognitive decline, transient ischemic attack, and overt stroke are all much more common following the detection of a covert stroke. Also, pertaining to covert stroke, which is of interest, certainly isn't practical to routinely conduct MRI evaluation in the post operative period. And so other methodologies would be very useful to apply both to research and clinical practice. We did conduct a study in high risk patients to evaluate for other strategies for the prediction and detection of this neurologic vulnerability. Um, we measured cognitive function testing, interoperative cerebral oximetry and brain injury biomarkers. And we actually didn't detect a signal with any of these methodologies. Uh, one patient in the study actually suffered a major cerebral ischemic event on the ICU and intubated, so it was a severe event, but there was no perturbation in the cerebral oximetry or any of the biomarkers tested. So we we certainly do not have a troponin equivalent for the brain. And novel research in this area is definitely warranted.

DR. STRIKER:

Do we have a sense of the key causes for perioperative stroke? Are there common comorbidities, or does the nature of the surgery have a bearing on perioperative stroke? Can we identify risk factors to help alleviate this at all?

DR. PICTON:

There is a lot of rich data concerning that question, and some surgeries definitely carry an increased risk of overt perioperative stroke. For example, cardiac surgery with the inherent risks of cardiopulmonary bypass, carotid revascularization, which requires the manipulation of the carotid artery or interruption of the cell blood flow, and neurosurgical procedures were of course, the primary site of the surgery, is the brain. All of these are known to be high risk of stroke, and in some subgroups where the aforementioned, the incidence approaches 10%. So that is a really noteworthy.

Pertaining to other specific procedures. The beach chair or sitting position is worth a mention here. We conduct large volumes of orthopedic surgery in this fashion. So it's a it's relevant to an enormous number of anesthesiologists throughout the country. And there have been multiple case reports describing catastrophic neurological injury in this patient group, which have been mostly attributable to several hypoperfusion. It's actually is recommended by SNACC now to consider the difference between the blood pressure measurement site, which is typically a noninvasive cuff on the arm, and the base of the brain for patients undergoing surgery in the sitting position. This is to provide a more conservative cerebral perfusion pressure. Following other major non-cardiac non-neurological surgery, non-modifiable independent predictors have been defined in a number of studies, and these include things which are perhaps not surprising, like age, ischemic heart disease, renal failure, any history of cerebrovascular disease, hypertension, smoking, COPD. The risk actually increases as the number of risk factors increase. And so preoperative risk stratification is critically important. Other known conditions, such as symptomatic severe carotid artery stenosis, for which revascularization should be considered before other elective surgeries are carried out, and conditions such as atrial fibrillation, patent …. are all highly relevant. Antithrombotic medications are often prescribed for many of these conditions. And there's always the debate between, you know, continuation versus cessation. And it is a difficult balance and a common problem facing anesthesiologists.

A number of published guidelines are helpful in this regard. Beta blockers have also been implicated to increase the risk of operative stroke. But the most striking data is from the Poy study. This was a a large randomized study, randomized preoperative metoprolol to placebo. The metoprolol was actually quite high dose, and the study revealed a higher mortality and double the stroke rate in the the metoprolol group. In the real world view into a number of large retrospective studies have not necessarily shown the same relationship. And the the latest large cohort study, published last year, failed to show any association with any beta blocker with stroke. So the situation is definitely, definitely complex. Intraoperative hypotension and either low or high end tidal carbon dioxide concentrations have also been identified as independent predictors for overt stroke. This work was done by Phil Belisthes who is also at Michigan and and others. And it's really exciting because these risk factors are not only biologically plausible, but they're also potentially modifiable. So we also conducted a series of studies in various patient groups, including those exposed to cerebral hypoperfusion, such as patients with carotid artery stenosis, patients undergoing and end up discectomy, surgery of the beta deposition, secondary cerebral tumor excision, and found that simple changes in ventilation strategy, i.e. increasing inspired oxygen fraction in combined with moderate hypercapnia reliably and predictably increased cerebral oxygenation. And they certainly support the recommendation which have been made in guidelines to avoid hypercapnia during anesthesia in patients at high risk of stroke. And similarly, avoiding hypotension is a very sensible that has been strongly recommended.

DR. STRIKER:

Well, let's talk a little bit more about the guidelines. Previous stroke is one risk factor you mentioned. And I know there's some debate about when that risk decreases. Anesthesiologists have to make decisions about how long to wait after stroke for surgery. Can you share any recent guidelines or findings that speak to this? Dr. Whalin. Why don't you speak to this one, if you don't mind?

DR. WHALIN:

I think that a lot of our early data was based on some studies out of Denmark from around 2014 by Jorgensen, which suggested that, you know, after someone having suffered a stroke is at very high risk of a recurrent stroke. And that surgery can kind of magnify that. And in that older data, from ten years ago, it was suggested that the risk will remain elevated throughout life, but that it's quite high immediately after the stroke and then decreases to sort of a nadir around nine months. So based on that study, there was a suggestion by SNACC that when possible, for an elective surgery, waiting for nine months could be preferable. This was then later echoed, I think, in some American College of Surgery guidelines to say when possible to wait nine months. But just in the last few years, I think it was in 2022, there was a newer paper on base that I think a Medicare database by Glance and Jama surgery that looked at maybe a more high risk population where you're kind of, um, you know, risk of stroke in general was higher versus the Denmark study that was nationwide and had a lot of people who were very low risk to begin with. Um, in that study, interestingly, showed that there was very high risk within the first three months. But the difference in risk between, like the period from 91 to 120 days or longer wasn't really significant. So their results were that there was no advantage to waiting 6 or 9 months, compared to 3 to 6 months. So I think that, you know, at some point we may be revising our guidelines based on this newer data, but it remains, always, I think, a judgment call for the anesthesiologist based on the urgency of the surgery and the perceived risks and benefits in conversation with the surgeon and the patient.

DR. STRIKER:

Are there emerging factors or trends we should know about? For example, what role could auto regulation play in filling the measurement gap? Is this on the horizon? Are there other solutions on the horizon we should know about? Dr. Whalin, can you start here? And then Dr. Pickton, we’ll ask you about adding your thoughts as well.

DR. WHALIN:

Yeah. I think you bring up a great point. And I think, uh, a lot of where the field of anesthesiology is moving is to try to have more personalized medicine, where we are really tailoring our management to a particular patient and their needs during a particular surgery. And so, you know, I think in terms of mitigating the risk of stroke, things that Dr. Picton already brought up about, how do we make sure that there's adequate cerebral perfusion is really the big question. And, um, you know, as we currently practice, we're a bit limited in that we're mostly, as you said, measuring blood pressure, oftentimes with a noninvasive device on the arm. And it's a little bit harder to know what's happening in the brain. Um, and so we know that the brain is usually pretty good at auto regulating and maintaining that constant, uh, cerebral blood flow across a range of blood pressures. But the exact limits of that autoregulation, um, right now are a little bit difficult for us to, to know. And so I think, you know, going forward, if we had better ways of defining the autoregulatory range for a particular patient could potentially help us tailor our hemodynamic management for the patient in an effort to minimize the risk of hypoperfusion and perhaps decrease their chance of of suffering a perioperative stroke.

DR. PICTON:

Yeah, that's that's absolutely right, man. This is really important because there's also enormous interindividual variation in the lower limit of autoregulation. And so very difficult to know if it's even appropriate to apply a mean for population, which is essentially what we have, to individuals. And you know, as Matt described, when cerebral autoregulation is intact, there is some safety provided to the brain in order to cope with differences in pressure. But, you know, there comes a point where the blood pressure falls below the lower level of autoregulation, at which point blood flow will then vary with mean arterial blood pressure. Um, this is this is interesting because you can also measure when those two different things, cerebral blood flow or a proxy mean arterial blood pressure, start to correlate. And so this measure of correlation can be used to identify a transition. And for individual patients actually has the potential to detect, point, and then one can institute treatments to restore blood flow to a safe value. So some groups have used this you know, they've used it with cerebral oximetry, which is a non-invasive oxygen monitor that can be used as a proxy for cerebral blood flow. And, uh, you know, they've produced something called the cerebral Oximetry Index, which is a measure of the correlation between the cerebral oximetry and the mean arterial blood pressure. And they publish some really promising data in different, um, surgical populations as a, as a measure of autoregulation. We're actually looking, in Michigan, to evaluate cerebral impedance used in a similar fashion. Data from pig models has been pretty promising going forward in human subjects undergoing surgery as the next step, just really from a feasibility point of view. And so, um, although I'm fairly optimistic and there's been some progress, I think we're still, you know, a good ways away from having a perfect monitor to for tailored care for individual patients.

DR. STRIKER:

So, Dr. Whalin, I do want to turn to you to ask you a few questions. But first, if you don't mind, let's take a short patient safety break. Stay tuned.

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DR. JEFF GREEN:

Hi, this is Doctor Jeff Green with the ASA patient Safety editorial board. Communication gaps during patient handoffs in the perioperative setting increase the risk of patient harm. While electronic tools can improve communication and patient safety during handoffs, low tech strategies can go a long way toward ensuring continuity of care and accurate information exchange. These include standardized checklists and templates, as well as patient safety communication techniques such as read back, repeat back, and other closed loop approaches. Formalized structured templates ensure that key information is communicated to all personnel involved in care transitions, such as for O.R. to PACU or O.R. to ICU transfers. For shift changes in the O.R., a less formal and more portable three by five note card with key safety information can be handed to the clinician, assuming care of the patient. With both approaches, face to face communication between providers is essential for a safe handoff. There is no one size fits all strategy to safe handoffs, but adopting a standardized process may improve patient outcomes.

VOICE OVER: For more patient safety content, visit asahq.org/ patientsafety.

DR. STRIKER:

Well, we're back. And, Dr. Whalin, I want to turn to you. If you suspect a patient has had a stroke, what are some steps you might take to avoid long term morbidity and mortality?

DR. WHALIN:

Well, I think that, um, in some of his opening comments, Dr. Picton really mentioned how in the perioperative setting, detecting stroke is quite challenging just because the residual effects of, uh, anesthesia and the recovery from anesthesia can obscure certain signs. And so, as he mentioned, I think it's really key to be vigilant and always have a high index of suspicion. Certainly, if the patient has any evidence of any kind of focal findings on their exam post-operatively, you should really think about getting expert consultation and potentially, you know, starting a workup for acute stroke. It can be challenging in some settings outside of a hospital environment where maybe you don't have ready access to neurology consultants or advanced imaging. But I think because, as we mentioned, the consequences of this disease are so dire and the possibility of of avoiding them, if you can detect stroke early by getting the patient's thrombectomy, is so impactful, you really want to be, I think, a low threshold to try to initiate consultation for a code stroke or potentially a transfer to a facility where where a patient could be evaluated for it.

DR. STRIKER:

Well, how important is early detection and timing here?

DR. WHALIN:

You know, we often have heard the phrase that time is brain. And that remains true. Certainly. Um, different people have different capabilities to have collateral blood flow, and those with poor flow really need to be treated very, very quickly. Um, those who have better collateral flow may be able to still get benefit from clot retrieval later on, but certainly the earlier the better, especially in the perioperative setting where we might, you know, attribute a patient's change in neuro status after surgery to just residual effects of anesthesia. You can lose valuable time and potentially miss a window to intervene. So I think it is very important to ask for a code stroke evaluation if you have any suspicion, just because the consequence of being wrong and ignoring your sort of gut feeling can be quite high.

DR. STRIKER:

Well, we all know that medicine is personal, but we're all operating in a framework of broad guidelines when it comes to certain pathologic processes. I'd like to get your opinion on a controversial question: what anesthesia is best, general or Mac? And do trials shed any light on this? What do we know? What don't we know? How should we proceed when we're trying to apply broad recommendations to to each patient, Dr. Whalin?

DR. WHALIN:

Well, it's certainly you've hit on one of the most controversial aspects of anesthetic management of thrombectomy and something that's been a long term interest of mine. You know, it's a long story with a lot of back and forth. I think that, you know, things really changed, uh, a few years ago with the publication of a couple single center trials out of Europe, which showed, you know, in broad sense that the the outcomes for either general anesthesia or sedation were pretty similar. And that flew, uh, you know, went counter to the conventional wisdom before that, which was that generally anesthesia was associated with worse outcomes. I think most of that older data was based on retrospective studies, where there was a lot of selection bias. The sicker patients tended to get general anesthesia. And, you know, they did worse, um, because they were sicker to begin with. Um, and so I think those single center trials really, uh, showed us that general anesthesia, when performed carefully, is a very safe type of anesthesia to provide for these procedures. Now, what was sort of interesting that came out of those studies was that, by some metrics, maybe general anesthesia showed some advantages. Um, the most notable one is probably the rate of successful reperfusion. And since the reason for the procedure is to pull the clot out, one would feel like anything that gave you an advantage for that would be preferred. Um, most recently, I think we've had two multicenter studies, both out of France. One was the Admetus trial most recently, and before that, the gas trial. And again, both of those showed really equivalent outcomes between sedation and general anesthesia. There was a small advantage in rate of successful reperfusion for general, but that didn't translate to differences in three month outcomes. The way I look at this is the goal of the procedure is to remove the clot. If you're working with an Interventionalist that doesn't have a lot of experience doing that with patients who are sedated, you know, and who's used to working with general anesthesia, then general anesthesia is probably the right choice in that setting. Um, in my hospital, we have a long history of working under Mach, and we have very high rates of reperfusion under Mach over 90%. And so for us, I think there's not any compelling reason to switch over. You know, with our practitioners and our particular practice model, Mach works great. I think if you're a lower volume center or you work with Interventionalists who just aren't comfortable doing these procedures on patients who are quote unquote awake, then general anesthesia may be preferred in those settings. You know, no matter what you choose. The bottom line is that you want to be very intentional about maintaining that cerebral perfusion, as we've been discussing and, uh, just trying to provide good conditions for the interventionalists.

DR. STRIKER:

Well, I don't want to let you go without getting your thoughts on the effectiveness of thrombectomy for stroke.

DR. WHALIN:

Yeah. Well, I think that there are certain, you know, environments where there's not a lot of anesthesia support for thrombectomy. In those settings, anesthesiologists haven't always been involved for staffing reasons or other issues. But what I'd like, you know, all of our listeners to appreciate is that this is one of the most effective and impactful procedures in all of medicine. You know, the number needed to treat to prevent or reduce disability is something like 3 or 4 patients, and there's really nothing else in medicine that can come close to that level of impact. Dr. Picton spoke at the beginning about the huge financial burden that this has. And so if you think about, you know, what is the impact of us helping out if we are involved in ten stroke cases, maybe there's an additional cost to the hospital to have that x ray anesthesia coverage. But if you're saving two people out of those ten from having lifelong disability, I think that there's a huge cost savings to society. And probably even at the hospital level with shorter hospital stays, patients who are difficult to place into rehab and things of that nature. So I would ask everybody out there to really try to embrace an opportunity to be a part of what is a tremendously effective intervention that really changes lives for patients, for their families and for society.

DR. STRIKER:

Such a great point. I do just have one last question for both of you. Can you tell our listeners about SNACC and the role it plays in your practices? Dr. Picton, why don't you go first?

DR. PICTON:

I'm a a really new member. So I'm excited to get your different perspectives on this subject and many others I, you know, value the society for helping to advance the field. Ultimately, and as Matt was just describing, for thrombectomy to improve patient outcomes and prevent harm. So, you know, that is really what I'm looking to learn from the society. Matt is a long standing member, may be able to give a more in depth perspectives.

DR. STRIKER:

And Doctor Whalin?

DR. WHALIN:

Yeah, well, I think one thing that Paul's case illustrates well is that, you know, SNACC is a big tent. And we really welcome people from all different realms of anesthesiology who may not work in neurosurgical rooms every day but have an interest in the brain, even in the critical care setting or the operating room or anywhere else. And I think for me personally, I really value SNACC because it's been such a tremendous boon to my career. I started off early on. I had some mentors who got me involved. I found that the SNACC leaders have always been very generous in trying to provide mentorship and support to to young anesthesiologists who are just getting started in their career. And so it's really been a tremendous home for me, a place where there's a lot of great advice and help to kind of expand yourself as a provider and as an academician. And so I think I would encourage certainly anybody who has an interest in the brain at all to go ahead and give SNACC a look. And, you know, you may decide that you don't want to be an active member, but please take advantage of all the great work that's done at SNACC to put out information to help anesthesiologists, you know, in all settings, whether it's in academics or in the community, help try to take the best care that we can of our neurosurgical patients.

DR. STRIKER:

Well, that's great to hear. The subspecialty societies do great work. We're happy to shine a light on the subspecialties on the show, and we hope to continue to do so as we move forward. This specifically was a really interesting conversation. I certainly learned from both of you, and I hope our listeners do as well. And I really appreciate you joining us today.

DR. PICTON:

Thank you for having me.

DR. WHALIN:

Yes, this has been a wonderful conversation. I really appreciate the opportunity.

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DR. STRIKER:

For listeners who are interested, you can certainly learn more about this topic about SNACC at S-N-A-C-C.Oorg and join us again soon for more Central Line. Thank you. Take care.

VOICE OVER:

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