CLE Care of Aortic Disease: Aortic Dissection

Podcast Transcript

Announcer:

Welcome to the Talking Tall Rounds series, brought to you by the Sydell and Arnold Miller Family Heart, Vascular and Thoracic Institute at Cleveland Clinic.

Eric Roselli, MD:

Our next speaker is Dr. Venu Menon, who's going to talk about the preoperative hyperacute phase of care for aortic dissections.

Venugopal Menon, MD:

Thanks, Eric. It's a great opportunity to be here, and I think it was a nice case highlighting how once you have an acute aortic dissection, it's not just the acute care, you're patient for life and you need to really take care of the patient, and your decisions really have downstream consequences. But let me start with talking a little bit about pre-operative hyperacute phase, and I would say the salient features of care in this setting are early recognition, and I will not talk too much about it in the emergency room, recognizing acute aortic dissection. One of the things that certainly helped with this, is the readily availability of CT scans, and also, I think an over exuberance of doing CTP protocols where even when the ER physician sometimes doesn't suspect it, we do come across plenty of aortic dissections recognized in this fashion. But I want to pay more attention in this stock to immediate and safe transfer, bringing the aortic team together, and initiating definitive therapy, as cardinal features and our goals when we see a patient.

Venugopal Menon, MD:

And I want to emphasize that the treatment of this really begins with, if you have a patient at three o'clock in the morning tomorrow, what are you going to do? And you better know what you're going to do now, because if your story starts when you first recognize dissection and then you're deciding what to do, then I think the game is lost. And so, let me put that in some perspective here. I think the first thing you really need to do, is try to create an acute aortic network. And we learned this from our STEMI experience in acute intervention. When STEMI is about 300,000 patients a year, really time sensitive emergency, and within five to 10 years everywhere in the United States, we can quite comfortably ensure that when you have chest pain and you call 911, an emergency room, ED ambulance, comes to your door, gets an EKG done, and you get door-to-balloon time in less than 90 minutes in nearly all zip codes of this country.

Venugopal Menon, MD:

In contrast to STEMI, acute aortic syndrome is a little different. The incidence is lower. We don't have a diagnostic test like an EKG to do on the field. We really depend in this day and age on an imaging study of a CT scan that needs you to be in an emergency room. The holy grail of a biomarker is still a holy grail. We can diagnose STEMI on the field. You need to be transferred to an imaging capable facility to get the diagnosis of a dissection. We have a very well defined time window for myocardial salvage with acute aortic emergencies, that time window is a little more nebulous, the sooner the better, but really no time dependent relationship that we can yet elucidate. The treatments are very common in terms of a STEMI. We can get a friendly cardiologist nearly everywhere to do a primary PCI on you in this nation, but open heart surgery is far and few, and especially someone who's dedicated to treating the aorta. Those are exceptions.

Venugopal Menon, MD:

And as a result, I want to emphasize that while you do create a network, the STEMI is a small area given that time dependence, but the aortic network can really have a much larger hinterland. Here's an early example. This is our STEMI network when we first started more than two decades ago. You can see that here in the main campus, we serviced a number of hospitals when we started here shown in green, many of which were as far as 58 miles away. And we did that by really being able to create an emergency transport team that was able to ship them immediately on recognition to our cath lab with activation done by the outside emergency room, and no intervention on the part of the cardiologist here in terms of having any blocks to coming to the cath lab.

Venugopal Menon, MD:

This acute transfer line really helped us. And when we thought of creating an acute aortic network, it seemed a pretty easy jump to say, "Why do you restrict that activation to STEMI alone?" We have a number of time sensitive emergencies like stroke and acute aortic syndrome fit into the bill. And as a result, what we did when we started this process, was create a emergency network where if you were to activate our acute care transfer line, regardless of what the diagnosis was, there would be some sort of transport moving towards you, whether a diagnosis was confirmed or not. And here on main campus, we were made aware of something in our neighborhood that was going to come into our unit in a couple of hours. And this really highlights what that experience was like. This is an early experience from the early 2010, 2012 time period. And you can see, unlike STEMI where you're treating six hospitals three times a week, when you're doing something like an acute aortic network, you're treating multiple rural hospitals, large hinterland, one to two patients per site, 84 different hospitals with a median distance of 40 miles, absolutely no deaths on transfer.

Venugopal Menon, MD:

And I think what this does, is buy you time and buy you efficiency and also buy you a destination. When the outside ED sees this patient, all they want is, can this patient leave my emergency room? And when you have systems like this, that certainly gets facilitated. One of the things we realized early on, and again going from our door-to-balloon time experience, is that if you did create some sort of a transfer system like this, you didn't want it to be a passive process. You want it to be an active process with active metrics where you actually were able to measure what you were doing. And so, this is an early paper of ours really highlighting how we look at total transfer time and handover time, which was a time, and let's say you went into a helicopter to an outside community hospital with a dissection, how long did you take to get in there, get that patient and ship that patient back into your helicopter to start flying back to your home base?

Venugopal Menon, MD:

And this was important in terms of our ability to know how far we could stretch our range in terms of delivering effective acute aortic dissection care. The second most important thing is, what do you do with that time? That transfer time is clearly not a passive time. It's a time when you should be trying to garner as much information. So in our setup, the minute a dissection is activated, both the vascular surgery as well as cardiothoracic surgery is intimated about that patient coming to the unit within the next half an hour or 45 minutes, so that we have them by the bedside. I think the biggest struggle is, what are we dealing with? And usually, there's obviously a diagnostic CT scan that's been done at the primary institution where the patient presented.

Venugopal Menon, MD:

And we've worked a whole lot on trying to create some sort of a cloud network where we actually have access to those images way before the patient reaches our CCU, so that we actually know what we can do with the patient when he or she arrives at the bedside. And so whether we are experimenting with something like this, which is a pack system on a cell phone, we've done a number of things to try to facilitate the knowledge of what that initial image is done in a emergency room where the radiologists may not be experienced in this, especially if there's endovascular stents and prior endovascular treatment. And then of course, creating within the institution dissection protocols and other things on CT that are standardized. And this will be discussed in other talks dedicated to imaging that will follow my presentation later today and tomorrow.

Venugopal Menon, MD:

This is an example of what happens at 3:20 in the afternoon. This is 9/17/2019. There's a patient coming in from an outside hospital with a Type A dissection. But this is what someone like Eric or Frank gets to see when they get a page saying, there's a dissection that's coming. One of our radiologists has already looked at the scan while the patient is in transfer. And you can see we know where the entry tear is, we know where the status of the false lumen is, we know whether there's any signs of malperfusion, we know exactly what we are dealing with. When the patient arrives to the bedside, the images proceed the patient. And I think developing these kinds of systems remain the most challenging issue as we go from one health system to another, but this is the key to delivering effective care in acute aortic dissection, is having access to imaging.

Venugopal Menon, MD:

When the patient comes to the bedside, in this kind of a scenario, what we are able to create and deliver, is multidisciplinary care. So in that case that was just noted, it's an obvious Type A dissection, the patient emergently needs to go to the operating room. But even in that kind of a situation, what we do is, the cardiac intensivist, the cardiothoracic surgeon and the vascular surgeon all come by the bedside to really make a decision based on what we see and what we have in terms of imaging, to really plan for early immediate definitive therapy. And this really buys us time. So when we actually look at our time to the OR for acute ascending aortic dissection, the mean time to go to the OR after coming to the CICU is probably somewhere between 30 and 45 minutes. And I think that is one of the keys to really succeeding when we are dealing with this complication.

Venugopal Menon, MD:

Here's an example of why it's useful to have a multidisciplinary team. This is a 90-year old person who comes in with a what looks like a large intramural hematoma in the ascending aorta arch, and descending thoracic aorta. The patient really was a poor candidate for open heart surgery, but when you have a group team taking a look at something like this, you can clearly see this extravasation of dye here in the descending thoracic aorta. And this is a retrograde propagation of a hematoma in this setting, and so you could cover that with a stent and you can see over time resolution of the dissection in this patient of the hematoma, and this patient did fairly well. So at three in the morning, to have these kinds of resources where you're flexible, where you're malleable and you can change course, I think is the key to success in this field.

Venugopal Menon, MD:

The other early goals of care clearly are blood pressure and heart rate control. We emphasize this during transfer. So we've written a lot about controlling blood pressure and heart rate in our helicopters and in our transport systems as patients come in to the unit. Clearly an assessment for malperfusion, not just on imaging, but on clinical grounds, establishment of venous and arterial access. And we always perform a bedside echo, because clearly, not in this audience, but the presence of aortic regurgitation and pericardial effusion are really signs that you better be in the operating room right away in this situation. And finally, to have this group by the bedside, really gets your consensus on definitive treatment and downstream treatment. So you know what you're dealing with today, and you already know before you go in there, what you're going to deal with, or expect to deal with tomorrow, and that was highlighted in the example that was presented before my talk.

Venugopal Menon, MD:

One of the things that we discovered, if you do follow this strategy, is that you do create new disease, we learned this again in the acute coronary syndrome population. When you open your cath labs to everyone, we do get false positive activation. Some of these are for real reasons where the EKG shows SD elevation and is a mimic, in others it may be the inexperience of the outside provider. I think this is part of the course and you want to be constructive when you report back to your referral base, you got to support these decisions.

Venugopal Menon, MD:

And in our setting, we found at least a 15% of false positive activation rate when we use this kind of a strategy to really have people shipped into our CICU. The main reason for this, is the non-gated CT scan that looks at the artifact of the aortic base and calls that a Type A dissection. And then you can clearly appreciate for Type B dissections with all that endovascular stenting. A radiologist in a small outside hospital with no images nearly always says, cannot rule out an acute pathology. And the patient gets transferred to us, and the images are consistent, and we don't have to do anything for it. So I'll end with that in that situation. The lessons we have learned in the management of STEMI are pertinent, but what we need for dissection is urgent activation, critical transfer, image acquisition and multidisciplinary input. Thanks for your attention. Thanks.

Eric Roselli, MD:

Once they leave, they go to the ICU, and there's a whole nother field of expertise that happens in the intensive care unit. Our next speaker is Ran Lee. He's a cardiologist who's critical care trained, heart failure trained, and takes care of so many of these sick patients after we operate them. He's going to talk to us about what happens for these dissection patients in the postoperative ICU. Thanks Ran.

Ran Lee, MD:

Thanks Dr. Roselli. Thanks to you and Dr. Menon for the invitation to speak here today. So basically, we'll be going over today the goals of postoperative care, and really emphasizing a systems-based approach to how we take care of these patients with these following considerations. And the other thing I want to really emphasize, is the prevention of complications as they head out of the ICU onto the floor. So the goals of post operative care are really rooted in systems. We usually focus a lot on neurologic status, the ability to deliberate from the mechanical ventilator, the preservation of hemodynamics and preserving hemodynamic targets, and at the end of the day, preservation of end-organ function and limiting metabolic arrangements.

Ran Lee, MD:

So to emphasize an example of systematic protocol based care, this is an example of our CVICU summary report handoff that occurs between the OR as well as the nurse practitioners and the CT anesthesiologists who take care of these patients in the postoperative ICU in conjunction with the surgeons. You have an indication for surgery, you have preoperative cardiac assessment, post cardiopulmonary bypass cardiac assessment, relevant past medical and surgical history, and a preoperative narrative hospital course, comments on airway difficulties, pacing wires, whether to retain or cut them. And then a chronologic list of major surgeries, events, procedures, need to be listed. And then for our colleagues who take care of these patients on a continuous 24/7 basis, having a summary of significant events over the last 24 hours and active assessment and plans and things to watch for, gets to be really important in the medical record. To focus on neuro assessment, early emergence from anesthesia is preferable to assess the neurologic status of these patients, given the aforementioned concerns with cerebral perfusion that we've done really well to mitigate from an intraoperative perspective.

Ran Lee, MD:

But stroke incidence can still be up to 14% of cases. So if that occurs, fast neurology consultation, CT and MRI if possible, and minimizing sedation are the goals to really get a true accurate neuro assessment in compared to last known normal. And then while doing that, optimizing blood glucose hemodynamics and anticoagulation status. Spinal cord injury, we see more commonly with Type B or thoracic abdominal repairs, but it is worthwhile to mention here as well as focusing on delirium and pain. So this is from Kaplan's Cardiac Anesthesia, but these are some factors that contribute to paraplegia after either thoracic or thoracic abdominal aortic procedures to the extent of the aneurysm preceding shock, emergency surgery, presence of rupture, the duration of aortic cross clamp, any potential sacrifice of segmental artery or intercostal branches, prior repairs and anemia, heading into the surgery.

Ran Lee, MD:

And then wanted to focus on a couple of things that we can do in the postoperative ICU setting to minimize this risk. So the presence and placement of lumbar cerebral spinal fluid drainages to maintain cerebral spinal fluid pressure less than 10, and maintaining your meaner shear pressure greater than 85 so that you can achieve a cerebral profusion pressure greater than 75, is of utmost importance to protect the brain. And then, as with any good steward of ICU care, just serial neurologic assessments get to be important as well. Prevention and treatment of delayed onset spinal cord ischemia, focuses on that, and any augmentation of the map with pharmacologic therapy, whether it be vasopressors or inotropes. Delirium and pain in the postoperative setting is not foreign to the postoperative aortic dissection patients. In the postoperative cardiac surgery patient in general, delirium prevalence approaches 50 to 60%. So we always go back to basics and remove or avoid benzodiazepines, opioids, antihistamines, anything that can be centrally acting that we know to be detrimental.

Ran Lee, MD:

Constant reorientation, family support, sleep normalization, and then the real key gets to be nutrition, early mobilization and management of pain. And we have different strategies now from IV medications to regional blocks, to be able to manage that in a more conservative manner. From a pulmonary perspective, standard of care is load tidal volume ventilation, targeting six to eight CC's per kilogram to avoid Barotrauma or Volutrauma, and keeping plateau pressures less than 30 millimeters of mercury and optimizing PEEP. And when weaning the ventilator, making sure that we prevent acidosis and hypoxemia with pH and PAO2 targets. When liberated hyperinflation and early mobility to prevent atelectasis and derecruitment, gets to be very important in pulmonary hygiene to progress these patients in the next phase of their care. From a hemodynamic target in the ICU, the MAP goal should be 65 millimeters of mercury at a minimum, but we have higher risk patients, older folks, folks with kidney disease, preexisting hypertension, preexisting coronary disease or stroke.

Ran Lee, MD:

And so, considering a minimum meaner shear pressure target of 80 millimeters of mercury to preserve that end-organ perfusion, is important. And if there's vasoplegic postoperatively, the use of vasopressors get to be crucial in our armamentarium. But oftentimes, we have the opposite problem where we don't have vasoplegic postoperatively, but we have excessive hypertension because of the preexisting medical problems that the patient came in with. So with excessive hypertension, there could be suture line bleeding, and if there's residual dissection propagation and further damage. So anti-impulse control, antihypertensives, as important as they are in the preoperative setting, still get to be something not to forget in the postoperative setting, targeting a systolic blood pressure of 120 millimeters of mercury or less. Here are some higher risk features to consider. In those types of patients are residual pain and false lumen, multiple or large fenestrations, a lack of an arch replacement at the time of initial Type A repair.

Ran Lee, MD:

IV medications can be utilized, IV beta-blockers, metoprolol, labetalol, esmolol, then IV vasodilators. IV beta blockers are used to decrease the aortic shear stress, the velocity of contractility or the DP over DT. And so, we target heart rates around 60 and blood pressures less than 120 over 80. In transitioning IV to PO, we really aim for beta-blockers or combined alpha-beta-blockers like carvedilol, dihydropyridine, calcium channel blockers like amlodipine or nifedipine. We tend to avoid RAS blockade in the initial setting, due to tenuous renal function that needs to be stabilized before that can be considered, but can be targets at a later on point in time. From a renal perspective, preservation of renal function is paramount. There are postoperative anatomic considerations really depending on the extent of the dissection itself. So minimizing hypotension, tubular necrosis, and avoiding any nephrotoxic agents. And there are some evidence that early renal replacement therapies, if necessary, can be helpful in this setting.

Ran Lee, MD:

This is a scientific statement on prevention of complications in the cardiac intensive care unit, so more of a preoperative setting, but I included it, because it's as applicable to the postoperative ICU setting as well, if not even more so from a postoperative perspective, specifically around number one, which is monitoring for prevention of healthcare-associated infectious pathogens, multi drug resistant organisms, utilization of meticulous hand hygiene, bundles of care to prevent these complications such as CLAPSIs, central line-associated bloodstream infections where catheter associated UTIs or ventilator associated pneumonias, screening for delirium, using pain assessment, and I talked about the regional blocks and other non-pharmacologic pain management that we can do, and optimizing therapies for sedation if they are still on the ventilator, and minimizing the use of neuromuscular blockade.

Ran Lee, MD:

From a ventilation perspective, low tidal volume ventilation, early extubation, daily spontaneous awakening trials and breathing trials, early mobilization once extubated, early nutrition, stress ulcer prophylaxis, and making sure that we have a multidisciplinary approach with daily checklists on our indwelling lines and mobility and pain. And all of these things mentioned here, get to be as important in the postoperative setting as the preoperative setting.

Ran Lee, MD:

So in summary, postoperative ICU care for the aortic dissection patient must be integrated, must be systematic, must be protocolized, and must be multidisciplinary. We emphasize early extubation when enabled to assess neurologic status early and to minimize adverse neurologic outcomes postoperatively. And we have hemodynamic targets to control the blood pressure to prevent any further postoperative complications, but they also must be balanced with maintaining adequate end organ perfusion. And above all, minimizing complications, delirium and pain are paramount, not for every patient, but specifically for the aortic dissection patient. Thank you.

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