Pharmacologic Considerations After Aortic Surgery

Podcast Transcript

Announcer:

Welcome to Cleveland Clinic Cardiac Consult, brought to you by the Sydell and Arnold Miller Family Heart, Vascular and Thoracic Institute at Cleveland Clinic.

Francis Caputo, MD:

I'd like to invite Dr. Cameron up here to talk about what do we do with this patient.

Scott Cameron, MD, PhD:

Thanks, Dr. Caputo. So we're now at the open stage, which makes it easy for me, and we've got an atrial arrhythmia to deal with, so the clot thickens. I'll focus a little bit on the pharmacology and things to think about depending on the type of repair. Just disclosure, I'm a cardiologist and vascular medicine physician, so some of the nuances will obviously reflect that type of background. Although I did care for many of these patients in the cardiac ICU previously. But you want to obviously make sure that the integrity of whatever repair doesn't ... all the good work doesn't get undone, basically. And then I'll talk a little bit about the care pathway that we have at Cleveland Clinic.

Scott Cameron, MD, PhD:

The immediate concerns that you obviously want to have is as follows: hemodynamics after the patient comes out of the OR, and there's going to be blood pressure excursions. Once the patient's awake, they're certainly going to be in pain and so sympathetic tone is going to be augmented. And so if you don't control pain as appropriately as you should, that's just going to be an additional barrier for the patient.

Scott Cameron, MD, PhD:

Secondarily, not so much germane to an open repair, I think, but maybe for an endovascular repair. If someone's got low blood pressure, that's certainly a bit more concerning because you don't want to cause ischemia to the spinal cord. But essentially the pharmacology is what I would encourage keeping your mind on in this particular phase. So if someone's had a suprarenal clamp, for example, the kidneys are going to be ischemic and the kidneys don't like that. And so when there's less pressure going through the kidney, the juxtaglomerular apparatus is going to see that, and then it's going to start pumping out renin like gangbusters as soon as you take that clamp off. And that might actually last for quite some time.

Scott Cameron, MD, PhD:

And so in the immediate postop phase, while it's tempting to use angiotensin receptor antagonists and also ACE inhibitors, the kidneys are also being boxed for a little bit, so you might want to be a little bit gentle and have a light hand in that case. Diuretics similarly, you're not really going to use that, particularly if it's an open procedure. There's been a certain amount of blood loss that you might have to work with. Calcium channel blockers and beta blockers are a good idea for a few reasons, which I'll show you. So please don't ever use clonidine, we really don't like patients on this medication. It is a centrally acting alpha two agonist, and so you'll basically induce a negative feedback at the presynaptic bouton, but it's really intolerable to patients and once we get them outside the hospital, it's incredibly difficult to wean them on it.

Scott Cameron, MD, PhD:

They have blurry vision, dry mouth, urinary retention, orthostasis, and we really don't like this medicine, but I do appreciate it does make things a little bit easier in the first part. Second thing is I really don't like to use hydralazine very often. Again, great medicine, but the issue with this is secondary reflex tachycardia, and if you were to ask me the hemodynamic issues that you have on the aorta that already is compromised, certainly, increased blood pressure is one thing, but increased heart rate is pretty dangerous. And then my own practice is I've noticed that there's a lot of off-label prescription of this, and quite often it's not given thrice daily as it should be. So we really don't like those medications

Scott Cameron, MD, PhD:

So what can we use? Well, one of the things that I used to always keep in mind is, of course, if you've got high heart rate and blood pressure, there's going to be a lot of wall shear stress. And when that happens, the endothelium doesn't like it, it'll stop making nitric oxide and it'll become inflamed. So what can you do about that? Well, one of the things that you could consider doing is using esmolol as a drip. Esmolol is a fantastic medication. Its half-life is only about nine minutes, and so if a patient becomes bradycardic, it's going to leave the body very quickly. If it's an older patient, which a lot of patients with aneurysms will be, you'll also have intrinsic conduction defects that you want to take care of. But it's a good medicine to use at least for the first half of the treatment.

Scott Cameron, MD, PhD:

And then once the patient is hopefully a bit more stable, you can think about transitioning them over to a beta blocker that has alpha one antagonistic properties. And the one that I like to use, it's an old one, but labetalol is a great medicine. You can use it in a very high dose 1,200 milligrams twice daily if you need to. Carvedilol is another possibility, but certainly you want to control that systolic blood pressure. And, as I think we were hearing, to around about less than 130 millimeters of mercury.

Scott Cameron, MD, PhD:

So in terms of uncontrolled pain, there's not really high quality data about this. There was one Cochran analysis that I found where they looked at epidural versus opioid anesthesia, and it turns out the mortality is actually similar at 30 days. There was one study that we did find in about 2,000 patients, it was observational where they looked at epidural anesthesia as well as general anesthesia comparing that to general anesthesia alone. And I was actually surprised to learn this: there is a mortality benefit that goes out to about eight years. But what they found is that if you did use epidural with general anesthesia, there was a mortality benefit. And it's unclear to me if the epidural being used, you were somehow affecting sympathetic tone, which those medications do in the postoperative environment, and perhaps you were preserving a bit more integrity of the procedure that was done.

Scott Cameron, MD, PhD:

Okay, so what do we do in terms of hypertension in the hospital and postop? So the care pathway that we have is, keeping in mind that the patient's going to be out to the world. And one of the things that Dr. Kirksey and Dr. Lyden brought up to me is that the patients, there's about a 10 to 15 percent issue where they'll come back to the emergency room with blood pressure excursions. Most of the time hypertension, but sometimes hypotension. And so if you educate the patient in the hospital, control blood pressure, and if you have them on an oral medication and after about five half lives, it should be relatively stable. And we're teaching the patients to take their own blood pressure and actually plug them in with the Vascular Medicine Clinic so that they'll log the blood pressure at home. If they're not feeling great or if there's very severe blood pressure excursions, they can call and actually have medication changes enacted over the telephone.

Scott Cameron, MD, PhD:

And in the immediate postop phase, again, we don't like to really use angiotensin receptor blockers or ACE inhibitors, but if you start with labetalol 100 milligrams twice daily, and then just look at their blood pressure after a couple of doses. If you see the systolic blood pressures greater than 130 or the diastolic blood pressures greater than 90, the next thing that we'd recommend doing is adding on a calcium channel blocker. You can use a non-dihydropyridine or a dihydropyridine calcium channel blocker. Amlodipine five or 10 milligrams is probably about right. Take another look at the blood pressure. If it's still much higher than 130 systolic, much higher than 90 diastolic, you can start escalating up the labetalol at that point, and then we'll see the patient in clinic and then take it from there. And that's sort of the point where we sort of think about getting them back over to antihypertensives that actually have better data such as chlorthalidone and some of the angiotensin receptor blockers.

Scott Cameron, MD, PhD:

Okay, so to deal with hypertension as an outpatient, this is where we'll start to think about giving other medications that we wouldn't immediately postop. So waiting a few days, particularly if it's been a suprarenal, and I think yours was a supraceliac clamp, so the kidneys are obviously going to be a little bit angry. You don't want to use a diuretic in that phase. But chlorthalidone is a great medication with really good data. And I think the SPRINT data, whenever that came out about 2015 or 2014, clearly showed that there's a mortality benefit in terms of preventing hemorrhagic stroke in those patients. So while we obviously want to protect the graft and we want to make sure they're not hemodynamically compromised, we also want to make sure that we continue to give them all those beneficial effects including preventing stroke.

Scott Cameron, MD, PhD:

So things to anticipate with ACE inhibitors and angiotensin receptor blockers is obviously a decline in renal function, particularly if the patient's seen renal ischemia. That goes without saying. So making sure that you get a basic metabolic panel within the first week of discharge. That's super important. And then the other thing is hyponatremia. I have had a couple of patients that had difficulty controlling blood pressure, get into a little bit of bother as an outpatient because their blood sodium was going down a little bit low. Even though it's asymptomatic, once you start to get down into the 120s, that should be a trigger to be concerned that you're actually over-diuresing them or they're having an off target effect, or something happened at the time of them having renal ischemia and their kidneys are just not used to handling sodium like they did. So watch out for that one.

Scott Cameron, MD, PhD:

And then of course, beta blockers. I've yet to put a patient into complete heart block, and I don't intend in ever doing that. I have had a couple of patients get a little bit bradycardic though an outpatient. And so again, labetalol is a good medicine. It is a beta blocker. It has really good alpha blocking effects, but just watch out for that. And so creativity is the main thing.

Scott Cameron, MD, PhD:

So coagulopathy, just talk a little bit about this. And so if you have a patient with an infrarenal aneurysm, everyone in the room knows, I think, that patients with infrarenal aneurysms quite often have a thrombus. I can count on probably one hand the number of times I've seen this in the thoracic aorta over the last couple of weeks and couple of years, in fact. But a lot of them have this. And if you look through the data, it turns out that they're in this sort of pre-DIC state. And we had started to sort of ask, Well, is that thrombus just there because there's, there's a lot of disturbed blood flow, or is there something fundamentally different about the blood of patients with infrarenal aneurysms that you would not see in a thoracic aneurysm?

Scott Cameron, MD, PhD:

And it turns out that both of them might be true because if you extract thrombus, they actually have enzymatic activity. Thrombus is not inert. It's actually biologically active. And if you use a chromogenic substrate, specifically for MMP-9 if it's an arterial thrombus, and some of these came from the aorta versus a venous thrombus, you make a different amount of it, but it's actually secreting it. And so part of the cure in my mind, even though there's not that much data on this, which is why we're working on it, is that, yeah, you're preventing dissection and rupture, but I actually think that thrombus is further remodeling the aorta. And so we should probably be doing something about that. There is a little bit of data out there that shows if you look at D-dimer, and if you look at fibrin degradation products, those are actually higher in patients with aortic dissections as well as patients who have aortic aneurysms without dissection.

Scott Cameron, MD, PhD:

And so I do think that there's a lot of space here for us to consider, particularly after a big surgical procedure, if you've got a patient on antithrombotic therapy consisting of antiplatelets or an anticoagulant, if they've got a mechanical valve or atrial arrhythmias, you certainly want to be careful and maybe just think about some of the downstream effects you might have to deal with.

Scott Cameron, MD, PhD:

And then finally, exercise restrictions. No high quality data after infrarenal aneurysm repair. Mostly it's extrapolated from the weightlifting literature. I tell patients to avoid isometric exercises actually for the first couple of months, and then certainly if they do, they'll Valsalva, they'll decrease preload, and they'll affect their blood pressure adversely, which is what you don't want.

Scott Cameron, MD, PhD:

So to conclude, blood pressure excursions are most common in the post-discharge phase after infrarenal aneurysm surgery. A dedicated care pathway in our experience is very helpful in preventing recurrent visits to the ER and then re-hospitalizations. Medications in a perioperative environment, focusing mostly on the beta blockers and calcium channel blockers, is probably about right. The medications to consider as an outpatient, at least initially, are labetalol and carvedilol. And then infrarenal aneurysms, once again, have thrombi, and so there may be some space for us to try and figure out what's going on in terms of effects with anticoagulants and antiplatelets. Thank you so much.

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