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Anesthetizing Dogs and Cats with Common Cardiac Diseases - Part 2
181 Plays12 days ago
Welcome back, gas passers! It’s time to pick up right where we left off—because your heart (and your patients’) can’t afford to miss part two of our special cardiac anesthesia series on the North American Veterinary Anesthesia Society Podcast!
Host Dr. Bonnie Gatson returns with the fabulous Dr. Carolyn McKune of Mythos Veterinary LLC to continue our journey into the nuanced world of anesthetizing dogs and cats with cardiac disease. Now that we’ve covered the pathophysiology and prep in our first episode, it’s time to talk protocols: how do we tailor anesthetic plans for patients with mitral valve disease and hypertrophic cardiomyopathy? What intraoperative monitoring really matters? And how do we handle those dreaded hypotensive or arrhythmogenic moments? This episode is guaranteed to provide some heartfelt guidance on tackling anesthetic management for these commonly seen, but nevertheless challenging patients.
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Transcript
Introduction to Anesthetic Management of Cardiac Patients
00:00:06
Speaker
Hello, Gas Passers. Welcome to another episode of the North American Veterinary Anesthesia Society podcast, the show where we explore the fascinating world of veterinary anesthesia and pain management.
00:00:19
Speaker
Our goal with this podcast is to advance and improve the safe administration of anesthesia and analgesia to all animals. I'm your host, Dr. Bonnie Gatson, and today we are going to be finishing up our conversation with Dr. Carolyn McCune regarding anesthetic management of dogs and cats with cardiac disease.
00:00:40
Speaker
So if you haven't listened to part one, i would recommend pausing this episode and going back to our previous episode so that you are all up to speed.
Sponsorship and Society Membership
00:00:49
Speaker
But first, we need to thank the sponsor of this podcast, DECRA, for their generous contribution towards supporting our efforts here at the NavVest podcast and for supporting continuing education efforts in the field of veterinary anesthesia and pain management. Please consider visiting www.decra-us.com and checking out their fantastic line of veterinary anesthesia products.
00:01:13
Speaker
Second, if you feel that listening to this podcast is helping you learn more about veterinary anesthesia and you're looking for even more ways to educate yourself about anesthesia, please consider becoming a member of the North American Veterinary Anesthesia Society.
00:01:28
Speaker
As a member, you will get access to even more amazing virtual educational opportunities such as fireside chats, which act like roundtable discussions where you can ask anesthesiologists and specialty technicians all your burning anesthesia-related questions.
00:01:44
Speaker
Please visit www.mynavvass.org to learn more about all that NAVVS membership has to offer. And as always, please consider supporting us here on the NavVest podcast by liking and subscribing to this podcast on whatever format you use to access podcasts.
00:02:03
Speaker
Also, consider telling your friends and coworkers about this podcast because the world needs more gas passers like you and me.
Recap of Previous Episode
00:02:10
Speaker
We seriously appreciate any and all listener support.
00:02:13
Speaker
So in our last episode, we set the stage as we prepared to anesthetize our dog and cat patients with underlying cardiac disease. With the help of the unbeatable Dr. McKeown, we're now going to talk about our anesthetic approach to these patients, from how we can monitor these patients most effectively to medications that we carefully choose for these patients. Okay.
00:02:38
Speaker
We'll also talk about common complications we see in these patients while under anesthesia and how we troubleshoot them. And if you stick around to the end, Dr. McCune will share a story about a dog with cardiac disease that she recently anesthetized, and she'll provide some insights and thoughts on how she handled that case.
00:02:58
Speaker
So let's get our finger on the pulse when it comes to tackling patients with cardiac disease right here on the NABAS podcast.
Preparation for Induction
00:03:10
Speaker
Okay, so now we're going to have the patient like physically in front of us. And let's talk a a little bit about what we're doing to prepare that patient for induction. And we're going to get to like premedication agents in just a moment. But personally, i think from what I hear, you like to make sure these patients have a pre-anesthetic blood pressure, maybe we place the ECGs on them before we induce them as well.
00:03:36
Speaker
And you also mentioned that you like to have some sedative agents on board orally, either gabapentin and or trazodone, so that these patients are sedate enough that we can give less of our other pre-medication agents.
00:03:50
Speaker
Is there anything else that you like to do with that patient, like right before you induce them? Oh, yeah. Pre-oxygenation, I think, is a big part for patients. of our amesthesia cases, but in particular for anything that can ultimately impact the lungs specifically and the cardiac side secondarily. And so these guys are worth a good effort to to be able to pre-oxygenate for a full five minutes beforehand.
Premedication Preferences and Avoidances
00:04:16
Speaker
Are there any specific premedication agents you prefer to give or avoid for these patients? Yeah, I am a huge fan of certain agents for healthy dogs that I do not like to touch for our patients with cardiac disease.
00:04:33
Speaker
One of those agents is dexmedetomidine. I am not a big fan of dexmedetomidine for dogs who have mitral valve disease because we know that a resting heart rate or higher is going to be important to prevent an increase in regurgitant fraction. And so the slower the heart rate is, the more time that animal has and with that regurgitant disease that it builds up more additional fluids. And so I do like to keep my patients heart rates at resting or higher. And so I avoid dexmedetomidine in these cases.
00:05:02
Speaker
I realize this might be a little controversial because I do know some cardiologists that will discourage the use of this drug, but I am okay with a limited dose of acepromazine in combination with the foundational cornerstone for premedication, which is opioids,
00:05:18
Speaker
And so I do tend to combine a low dose of acepromazine, either 0.005 milligram or 5 microgram dose of acepromazine up to maybe a 10 microgram or 0.01 mg per kg dose of ace with these cases.
00:05:34
Speaker
When it comes to induction, what drugs tend to be the safest for patients with mitral valve disease?
Induction Agent Recommendations
00:05:42
Speaker
In the United States, we still have the availability of Atomidate, which when compared head to head with my ultimate second favorite induction agent is just a little bit safer. And so if I have a patient who is, you know, like a stage C and I'm physically doing the anesthesia, I might lean towards Atomidate.
00:06:01
Speaker
For the majority of these cases, alfaxilone becomes the more practical choice. And in North America, in Canada, for example, it is not available. And so alfaxilone becomes the best choice depending regionally on where you are at and what is available for you.
00:06:15
Speaker
With either of these agents, it's my preference to co-induce. And so I do like to give dose of midazolam alongside those agents and reduce the total amount of induction drug that I need to give altogether.
00:06:30
Speaker
What's your opinion about using ketamine as part of your either induction or premedication protocol? Now you're going to the old school there, Bonnie, because when I was in veterinary school in the 2000s, ketamine was the agent of choice we used for dogs with mitral regurgitation.
00:06:47
Speaker
And so oftentimes if I don't have alfaxalone in a clinic, it's a patient who has has relatively stable cardiac disease, so they're not a stage three or anything like that, I will intentionally include propofol ketamine protocol. And so, Ketofol is what we kind of lovingly call that combination as the next safest agent of choice in that canine patient. And so, I am not afraid or discouraging the use of ketamine.
00:07:14
Speaker
I'm I tend to use quite a bit more alfaxilom dazolam in my own hands. But if someone were to tell me that they're using alfaxilom and ketamine, I would not think that's awkward or unusual in any way, shape or form. Because when I was trained, ketamine was our agent of choice for these dogs.
00:07:31
Speaker
And how do you like to manage maintenance and and anesthesia in these cases?
Maintaining Anesthesia and Managing Heart Rate
00:07:37
Speaker
Yeah, I think you and I are both on the same page, always a local block in some way, shape or form. Local blocks are the only things that we can administer that stop pain transmission. And so if a local block can be incorporated, i try to make sure that is done. And then there's some other things that are very specific, I think, to the cardiac patient. For the patient with mitral valve disease, as we mentioned earlier, I like to keep the heart rate at resting or higher. Sometimes that means that I will incorporate an anticholinergic, either
00:08:05
Speaker
glycopyrrolate preferentially or atropine into these cases so that I can keep that heart rate at their best resting baseline or higher, which is usually higher than a dog who does not have cardiac disease.
00:08:17
Speaker
I'm also a big fan of trying to limit inhalant to the largest degree I can. And so we, again, don't have time to get into the technicalities of MAC values, but If you know the MAC for your agent and you know that's what your vaporizer is delivering, I try to stay at MAC or less for those agents.
00:08:35
Speaker
And that sometimes means I have to incorporate other things beyond just local blocks. So sometimes I do need an opioid CRI to allow me to turn that vaporizer down or even if you don't have the ability to give an opioid CRI, to give a second dose of your premedication if it's been a while, you know. So if we gave the premedication, we obtained the catheter, we had to call the owner, all of a sudden now that premedication was given an hour and a half ago and we're just in the middle of this procedure, well, we can always repeat that bolus if we don't have a CRI as an option.
Fluid Management and Inotropes
00:09:05
Speaker
As the cardiologists always ask us, we do usually try and be judicious with fluids. In other words, we try to tailor the fluid rate to the patient, which usually means reducing the amount of fluids that we would normally give to the patient in the OR.
00:09:21
Speaker
We try and keep the blood pressure, i try and keep the blood pressure at about 75% of what is normal. So if that dog is coming in systemically hypertensive at 160 millimeters of mercury, i really don't like that systolic to drop much below 120 before I'm starting to intervene With the other agent I'd like to have available or on hand, which is a positive inotrope. And so oftentimes dobutamine or dopamine as an option to be able to help to improve the contraction of the heart. So those are some things I like to do for the maintenance of my intraoperative cases.
00:09:58
Speaker
The other drug that I could think of that I might also consider incorporating into and ah ah a maintenance protocol are neuromuscular blocking
Neuromuscular Blocking Agents
00:10:10
Speaker
agents.
00:10:10
Speaker
I think those are drugs that have minimal cardiovascular effects, but they work synergistically lot of times with our inhalants so that we can get away with giving less inhalants. So that is another drug that I sometimes consider for these patients too. I don't know if you're using a lot neuromuscular blocking agents or not.
00:10:26
Speaker
I do not, but I do work oftentimes in remote settings, which means that then the big reason, and I'm sure for the listeners, they might be aware there's a lot of support that needs to come with the neuromuscular blocking agents. Generally, we try and monitor them in terms of nerve stimulation, and we have to have the potential for a reversal in case we have to discontinue before the neuromuscular agent has worn off. And because a lot of the either virtual places that I do a lot of the cardiac work through or some of the general practices that I might work through do not have that support. I don't tend to do a ton of those kind of things, but I can definitely see in referral or academic institutions, the utility of all of this. Yeah.
Anesthetic Approach for Cats with HCM
00:11:06
Speaker
Yeah. Okay. So let's move on to cats with HCM. So I can say, hopefully for both of us, you would agree that what we talked about with dogs with mitral valve disease, as far as utilizing oral sedatives like gabapentin beforehand and proxygenating, getting ECGs, doing a baseline blood pressure, those are all, should be all the same in my opinion for cats. I'd agree.
00:11:31
Speaker
Yeah. So let's focus a little bit on cardiac medications for the these patients, because oftentimes the cardiac medications that are being utilized to manage cash with HCM is going to be different from dogs with menstrual valve disease.
00:11:46
Speaker
So in your opinion, which cardiac medications do you recommend the patient continue up until like the morning before anesthesia versus which drugs do you recommend that they be discontinued beforehand?
Cardiac Medications for Cats with HCM
00:11:59
Speaker
yeah Yeah, I think the probably the big one that I prefer to have discontinued if possible if they are on something like clopridogil, and we know that there's a potential for hemorrhage, I do prefer that these cats are off the clopridogil for a good five to seven days beforehand. And so that's probably the one I have the most adamancy about with everything.
00:12:18
Speaker
Other than that, I think that the majority of times a tenolol is fine beforehand because my target goals for heart rate are going to be different for the HCM cat. And so I'm okay with them having a little bit of a lower heart rate.
00:12:30
Speaker
But just like we said, and with the dogs, there are some crossovers. If they're on any kind of ACE inhibitor or other blood pressure, reducing agents, same thing applies that we'd probably ask that 24 hours beforehand, they do not receive that medication.
00:12:46
Speaker
Are there any specific premedication agents you prefer to give or you know try to avoid for these particular patients with HCM?
Premedication Alternatives for Cats with HCM
00:12:56
Speaker
Yes. And so it's a controversial subject, but I am okay with the use of dexametetomidine as part of a premedication for these cats.
00:13:08
Speaker
But I want to reiterate to the listeners, the dose makes sense. the poison, right? We've been having that Latin phrase for a long time, the dose makes the poison. And so I use a conservative dosing strategy for patients who might have hypertrophic cardiomyopathy. In other words, in your normal, bouncy, happy, healthy cat that's coming in to be spayed, that we don't have any kind of specific concerns, although we know there can be underlying subclinical HCM, but is otherwise looks pretty happy and healthy, I'm fine with 8 to 10 microgram per kilo combined with an opioid for the premedication. So 8 to 10 microgram per kilo of dexamide combined with a premedication opioid dose.
00:13:48
Speaker
Whereas maybe in the patient who has hypertrophic cardiomyopathy, I'm looking at 2 to 3 microgram per kilo in combination, as we said before, coming in with perhaps gabapentin, maybe travisodone,
00:14:00
Speaker
as a sedative for that cat so that they become more handleable. And so I'm sure we'll talk about why that might be helpful later on with all of these things. But our target goals, again, are going to be different for cats than they are with dogs.
00:14:13
Speaker
Oh, and then other things that we can use as premedication would include alfaxalone can also be given IM. And so if we have a patient who is particularly challenging to handle and we are nervous about including dexmedetomidine for that patient, alfaxalone has been demonstrated to be given everything from IM. Obviously, we're most familiar with its IV route. It's got a multitude of different ways that we can administer that, and it might make that cat a much more handleable cat as part of the premedication rather than just the induction schematic.
00:14:48
Speaker
I tend to avoid ketamine as a premedication or induction agent for these cats because of the increase in heart rate that they can experience and the increase in blood pressure. And so that's one drug I probably don't administer at a dose that I would need to have for a premedication or induction.
00:15:08
Speaker
You know, I had a cat just last week that was a very angry bangle and had known cardiac disease already. think it was only like five years old or something like that and had known cardiac disease.
00:15:22
Speaker
And the cat was very angry. And so those are the cats I personally tend to use dexmetomidine on when you've decided that it's for the safety of everybody around us that we're going to include it.
00:15:35
Speaker
So I think for that cat, I did like methadone 0.2 mg per kg. alfax alone, one mig per kg. And I think I only gave two micrograms per kilogram of dexbenetomidine.
00:15:49
Speaker
And we just gave it one, like we held the cat down. We didn't even take it out of its carrier or do like a pre-anesthetic evaluation because the cat was so angry. And we just went ahead and gave that combination like through the carrier because it was one of those soft carriers you could push down.
00:16:06
Speaker
And the cat responded to it beautifully. And actually, when we escolted it after we took it out of the carrier, it didn't even have a heart murmur anymore. Yeah, because I think of what we talked about with the fact that SAM or systolic interior motion of the menstrual valve oftentimes causes these heart murmurs.
00:16:25
Speaker
And this cat had a component of SAM in its hypertrophic cardiomyopathy. And I think the dexminetomidine helps to reverse some of that, which is a bit of a complex physiology, but it has been shown that it does that. And so the cat just didn't even have a heart murmur anymore.
00:16:42
Speaker
And I've definitely had that same thing, Bonnie, where I've administered low doses of dexmedetomidine combination with other agents to these cats and that the heart murmur actually goes so away. And again, dexmedetomidine is reversible like our opioids are. And so if you don't like the outcome of that, we can go ahead and we can offload that particular drug.
00:17:02
Speaker
But we do know that we have recent work from 2024 looking at feline morbidity and mortality for these cases and that we see with those cases that dexmedetomidine is one of the things that reduces mortality for cats. And given the fact that hypertrophic cardiomyopathy is such a prevalent condition with them, i do not fear the use of dexmedetomidine in the cat that might have HTM, but I am thoughtful and conservative with doses.
00:17:31
Speaker
So beyond what you mentioned with using ketamine in cats with hypertrophic cardiomyopathy, when it comes to like induction agents or like maintenance of anesthesia, is there anything you're really doing differently than what you've already discussed about with dogs?
Anesthetic Management Adaptations for Cats
00:17:45
Speaker
Yeah, definitely. I'd say that we alter our management for cats considerably. Alfaxilone is still a great agent. I still do like to use co-induction. I know some people are concerned about the use of midazolam in cats.
00:17:59
Speaker
And really, i do feel if you have midazolam in your clinic, you really should probably also have a bottle of flumacinil as a reversal in the clinic for that agent because flumacinil now is like $4 a bottle. It used to be quite expensive, but now it's quite reasonably priced. And so have flumacinil available in case you don't like what happens with that. So I do a co-induction just like we did The management for me is very different for our feline cases We still limit the fluids. We still try and keep the inhalant to MAC for cats, which is a little higher than dogs. Then like we do, we always use a local block when we can.
00:18:35
Speaker
We still target resting blood pressure to be the goal around where we manipulate and try and target. But in these guys, we like what we call low and tight for the heart rate and the blood pressure. And so when it comes to their target heart rate, we've actually found that the more time they spend in diastole, like we talked about at the beginning of this discussion, allows them more time to perfuse those thickened, enlarged cardiac muscle tissues.
00:19:00
Speaker
So we want to try and make sure that their heart rate stays at the low end of their normal. Definitely cats have an aversion to being too bradycardic under anesthesia, but if their normal resting heart rate, especially if they're on a telenole is 180, then we're probably looking to target somewhere between 100 and 140 instead of 180 to 200. And so we want to try and keep their heart rate to be low heart rate.
00:19:27
Speaker
And then if I need to target something to improve blood pressure, instead of asking the heart to contract in a more prolific fashion, which these guys, if we look at their contractility, it's already quite high.
00:19:41
Speaker
I don't like to use dopamine or durbutamine for these guys. And so asking that heart to work any harder is a dangerous situation. We can definitely have cats that that may have a fatal response to that whole thing.
00:19:53
Speaker
So I tend to use phenylephrine. And so as you're talking about reaching out to the clinic that you might be working with. I've definitely had clinics where we've had to reschedule procedures so that they can get a bottle of phenylephrine with, but I've been surprised also at the creativity of some of these clinics for being able to obtain the drugs that they need to have. And so splitting the cost of phenylephrine amongst multiple clinics and locations so that everybody only has a couple bottles on hand.
00:20:19
Speaker
Those kind of things that we can make sure that there's maybe multiple people that benefit. And so if I have to use an agent for blood pressure support, I avoid dopamine or dobutamine and I rely predominantly on phenylephrine as my agent of choice for all of that.
00:20:34
Speaker
yeah it's interesting that you say that because i have a little bit of a different experience with that, which is fair because it shows you there's lots of different ways to do the same thing. But I agree with you. I think that using a presser is usually a little bit better than using an inotrope for these patients.
00:20:52
Speaker
That being said, I think there was a study that was done. It's very old now, but they were looking at comparing a drug like dopamine to a drug. I think it was phenylephrine.
00:21:02
Speaker
to increase blood pressure in cash with HCM that had anesthesia induced hypotension. And that both like while phenylephrine did a good job at increasing blood pressure, you know, the cardiac output was like reduced in those patients and that they were successfully able to increase blood pressure with patients with dopamine when that population of patients,
00:21:26
Speaker
So I still personally utilize dopamine. it also like dopamine is like my crutch a lot of times, like I'm just super comfortable with that drug. But the reason I'm okay with dopamine is because you can get that dose dependent, you know, alpha effect.
00:21:41
Speaker
So sometimes if I have a practice that can't get presser and but we've got dopamine, I personally will still continue to proceed. And I've been able to manage blood pressure issues successfully with dopamine in the past. But I hear your point with the issues with the contractility.
00:21:59
Speaker
So I just like your personal preference. But you know, having a way to manage blood pressure using pharmacologic agents, as opposed to but we're going to talk about in a minute, fluid therapy,
00:22:13
Speaker
is probably like the big takeaway from this discussion, in my opinion. Yeah, yeah, definitely. And I think you're right. There's multiple ways to do that. And part of it is that I'm colored from having a cat that died receiving dopamine, knowing he had underlying cardiac disease. And so Phenylephrine, I find very titratable in that you don't always have to give it as a CRI. And so anyways, I think you're right that there's a multitude of different ways to do this, but that it is probably best to, if you're working with an anesthesiologist, to maybe work with that person's comfort level and experience.
00:22:45
Speaker
Because I can definitely tell you the one thing that is probably not good is to ask somebody to use something that they're uncomfortable with. So yeah. Oh, 100%. Can you talk about the challenges of fluid therapy in cardiac patients and how you tailor your approach to fluid therapy in both dogs and cats with cardiac
Fluid Management Strategies
00:23:06
Speaker
disease?
00:23:06
Speaker
Yeah, yeah. I think fluid therapy is something that's received a lot of attention. We've had new guidelines that have come out regarding fluid therapy. And I think so the best part about these new guidelines is that they say that this is not a one and done. In other words, the fluid therapy is now tailored where We administer what we believe is our target fluid therapy, accounting for the fact that, for example, some of these patients might also have renal failure as a comorbidity.
00:23:34
Speaker
And so in those patients, I do like to have them come into the hospital and be the second case of the day or the third case of the day where they begin on a very conservative fluid therapy. But then we recheck, right? And so that's what the new guidelines really kind of hammer home is that it's not just that we set the fluid rate on the pump and that we then go ahead and keep moving with everything else.
00:23:56
Speaker
We try and make sure that at each hour or depending on how severe the cardiac disease for that patient is, in other words, if they're a stage C, it might be every 30 45 minutes. We do things like make sure we do a thorough auscultation and we might reset that fluid pump to a lower rate for those guys. And so my personal kind of preference for patients who do have comorbidities is to do a conservative dose for a longer period of time before they experience anesthesia so that I know that they're appropriately hydrated, and then to make sure that I'm rechecking on that regular basis so that they're not overloaded. And that same thing happens intraoperatively with the patients when they're set on a fluid rate that we recheck rather than just assuming that's going to be a good standard for them throughout the entire procedure.
00:24:42
Speaker
Yeah, for me, I totally agree with you there. And I think if I'm just like generically going to set a fluid rate, an anesthetic fluid rate for a dog with mitral valve disease, I usually pick somewhere between three and two and a half mils per kilo per hour. And I think it's just dependent on what stage of they're in with their mitral valve and how like enlarged their left atrium is. So obviously we're going to be more conservative if you like the the larger their left atrium is.
00:25:08
Speaker
And then for cats, I usually just do two, but I don't know, like like two mils per kilo per hour. But I don't know if you're doing something similar or not. Yeah, I think most of us probably start out at that two mils per kilo per hour and then continue to check. And then again, we're going to talk about the postoperative period, but the checking does not stop when anesthesia stops. It's going to continue to go on so that we can make sure that patient is safe and stable.
00:25:35
Speaker
Yeah, I think when I first started my residency, there was a push to be using half-strength saline for these patients for their fluid therapy, for anesthesia. And eye pretty much stopped doing that and almost immediately in my residency.
00:25:52
Speaker
So I've just continued to give these animals isotonic crystalloids, just LRS and plasmalite. I don't know how you feel about like the fluid choice to be used.
00:26:03
Speaker
Yeah, I would agree with you that I think that, you know, there might be some differences between anesthesiologists and either internists or cardiologists in terms of those fluid choices. But I would agree that I do not use hypotonic solutions because we do know that we're probably robbing Peter here to pay Paul. So we're stealing fluid from elsewhere and essentially dehydrating other important organs in order to be able to use that hypotonic solution. So my My preference is to be able to administer a normal isotonic crystalloid solution for these guys. I very rarely, i tend not to use any colloids in these patients just because I do worry that if we get into trouble, it would be hard for me to get rid of because the fail safe, if we do use crystalloids, maybe to a higher volume than we intended to for whatever reason, we do have in the patients who are not refractory to treatment, the option of using a diuretic to remove extra fluids. And so, yeah.
00:27:00
Speaker
Yeah, i mean this may be a little bit more esoteric, but I always get nervous, even though in theory, it should be the right thing to do. But I always get nervous about using low volume resuscitation in these animals whereby like maybe you have hemorrhage or maybe they are hypothalamic because any patient Any of these things can happen.
00:27:22
Speaker
So I feel like when I am thinking about using low volume resuscitation, because in theory, that would be a great thing to do for an animal. with cardiac disease. But if you're going to use something like hypertonic saline, you know, you're causing and increased salt load, which, you know, we didn't really get into like the neurohormonal components of cardiac disease, but increasing the salt load is not always like the best choice for these patients.
00:27:49
Speaker
But then if you're going to use a colloid, just like you said, so I oftentimes just go with like the regular old isotonic crystalloid boluses, like if I need to under anesthesia and then post-op, I'll treat their fluid overload as needed.
00:28:05
Speaker
I don't have like thoughts on that too. Yeah. Yeah. And I think that you're right that like, you know, this discussion isn't necessarily focused predominantly on fluid therapy, but that is why fluid therapy as a concept can be such an intriguing concept and I'd say that you and I probably have a similar management to that, but that you know that is another thing that I'm sure there's probably other criticalists and cardiologists out there that also have thoughts.
00:28:30
Speaker
Oh, I'm sure they do. so So as far intraoperative monitoring is concerned, I think we did a pretty good job at emphasizing what are our like treatment targets for monitoring parameters, whether that be blood pressure or heart rate for both mitral valve and of HCM.
Monitoring Anesthesia in Cardiac Patients
00:28:49
Speaker
But in your opinion, you know, what are the most critical parameters that we should be monitoring during anesthesia for cardiac patients? Yeah. So I think that we can all agree that most of us are tied to many of the things that are on the multi-parameter monitor, for example, end tidal CO2. When end tidal CO2 requires good cardiac output,
00:29:14
Speaker
to be delivered to the lungs. The only way we can measure an end tidal CO2 from a patient is if blood is flowing from the heart to the lungs. And so that can be a great value to tell us about whether or not we've got normal cardiac output.
00:29:28
Speaker
We definitely want to monitor for hypotension is our probably big hitter as well. And so in an ideal world, would it be great if every animal had an arterial line? Yes. But I think, as you said, kind of at the end of the day, when it comes down to this, the overall you know requirement is that we do monitor some form of blood pressure, whether that's with a Doppler for a cat or a metric unit that might be more suitable for some of our larger patients.
00:29:58
Speaker
There's a variety of different ways, but definitely making sure we monitor blood pressure. Pulse oximetry is definitely a great idea for patients who may have potential for your volume overload. And then ECG is vital to make sure we're not having any arrhythmias, especially in those patients where myocardial ischemia is a real possibility, like the cat who hate might have underlying HCM.
Postoperative Monitoring and Analgesia
00:30:22
Speaker
So postoperatively, like we've woken our patient up. Are there any specific complications you're watching out for either with dogs and mitral valve disease or cats with HCM?
00:30:34
Speaker
yeah I guess specific to their like cardiac disease. Yeah. And so definitely I think for most of these patients, I'm most comfortable to put them on a respiratory watch afterwards. And so simple things like counting the respiratory rate to make sure that is not elevated, but also especially in immediate postoperative period. One thing I do for any patient that has cardiac disease that I've anesthetized, I like to make sure I repeat the a thorough auscultation for them to make sure I don't hear at that very moment any adventitious lung sounds that might suggest that there is some sort of volume overload. And I do usually continue to monitor the pulse oximeter value for as long as that animal is tolerant of all of it as another kind of surrogate method, appreciating that there's probably not going to be in many clinics somebody who can dedicate
00:31:21
Speaker
sit there next to that patient for the full three hours of recovery. Sometimes that can do give you those values, like if the patient is becoming tachycardic and the saturation value is starting to fall on room air, I am worried that maybe that needs to be cued in as a reason to asculpt that animal again, even if maybe it's not that hour mark where that asculptation is recommended. So yeah, that's what I tend to do. How about you, Bonnie?
00:31:46
Speaker
I agree with you. And I also like to watch their heart rate as well. You know, I think something we didn't super harp on, but is very important for these patients is to eliminate other causes for these patients to be tachycardic. And that includes providing effective analgesia.
00:32:04
Speaker
So that's like so critical for these patients because as you mentioned earlier, especially cats, like stress can augment their cardiac disease so profoundly.
00:32:15
Speaker
So beyond just like making sure they're well-anneled G's is also just making sure they're comfortable in the hospital. And so sometimes these animals need like continuous administration of gabapentin or injectable sedative agents as well. So I'm not afraid of making sure that these animals are like,
00:32:33
Speaker
pretty sleepy, you know, or at least comfortable in the hospital while they're recovering. I would agree with you. And we had a cat where it did hip cardiac disease. It came in with gabapentin on board. And with that gabapentin, it was handleable with a little bit of finesse.
00:32:49
Speaker
But once that gabapentin were off, we had to re-sedate him to just get the catheter out to send him home. So I would agree that we can, especially if we see that patient initially sedated, maybe have a altered opinion on what the cat's real personality might be. And so we may need to be more aggressive in that postoperative period before they get to be too wakey, eggs, and bakey, that they are at an adequate level of handleability, which will hopefully then reduce the stress and the myocardial stress they'll experience.
00:33:19
Speaker
Yeah. And, you know, some of these procedures are going to be
Educating Pet Owners on Post-Surgery Care
00:33:22
Speaker
outpatients. And one thing I think is so important is because monitoring their respiratory rate post-op is like critical as far as watching them for potential fluid overload or complications from their cardiac disease.
00:33:35
Speaker
When you're sending the patient home, you know, oftentimes we'll tell the owners like, oh, just watch for like increased respiratory rate. Sometimes people like really just don't even know how to count a respiratory rate. So I tend to make sure that when I'm sending the animals home, I will literally ask the owners if they feel comfortable taking a respiratory rate.
00:33:55
Speaker
And sometimes I have to teach people how to do it because they've never done it before. Yeah, I think that's a great point. And then them being aware that if there is a respiratory emergency, it's best for them to go to a location that might have overnight care. So in other words, the temptation is to want to come back into their regular veterinarian, but that ultimately, if there is any kind of respiratory problems, whether that's in the immediate postoperative period or whether that is something that the owners experience at home later on,
00:34:22
Speaker
Having a facility that has overnight technicians is going to be vital. yeah Yeah. And on that same kind of note with all of those kind of things, I try and make sure the patients also when they're leaving are kind of a little bit bright and alert and so that the owner can be able to kind of have an assessment of what is normal, but also to know what might be.
00:34:43
Speaker
Dr. Jennifer L.
00:34:49
Speaker
we've placed an endotrical tube it's the only way for us to safely administer our inhaled agent and for us to protect that airway and so they will cough you know and so if the patient looks bright and alert but they're occasionally coughing That is potentially due to the presence of the endotracheal tube and so not to become very fearful. However, if that patient seems to look dull, unengaged with everything and respiratory rate is starting to increase, then that cough might be more significant. so I try and just let them know that the simple presence of coughing in a bright, alert, happy, engaged patient is not a cause for alarm as opposed to a patient who has other signs that things aren't going well.
00:35:27
Speaker
When do you recommend restarting cardiac medications in these patients if they've been discontinued?
Resuming Cardiac Medications Post-Surgery
00:35:33
Speaker
Yeah, I don't know about you, but I usually ask that when that patient begins to return to kind of normal eating, that that's when I try to recommend them begin the cardiac medications again. And so sometimes that means the next morning if they are quite a bit older, because I'm sure like myself, you probably end up doing some of these patients that are 15, 16, 17 years old. Anastasia really takes it out of them.
00:35:58
Speaker
And so they may be rather dull when they go home and it'll take them to the next morning before they start to regain kind of their more normal behaviors. And so for those guys, I do so like to see them starting to have that return before I begin the cardiac medications again.
00:36:13
Speaker
Yeah, I'm actually a little more aggressive because I've had at least two or three patients that I've lost in the like 24 hour period after anesthesia, whereby like they looked great when they left the hospital.
00:36:28
Speaker
But maybe they weren't like eating that night. And these are typically like dentistry patients. And so they're not eating super great. And so the owners like didn't give their Pimobendan. And then it's like the next day and they still didn't give the Pimobendan.
00:36:42
Speaker
And then those animals like acutely decompensate. So for some of my practices, we've had a discussion about this and we've gotten pretty aggressive about telling owners that they like need to give their dogs their like Pimobendan and diuretics.
00:36:58
Speaker
In the postoperative period. And since I've been a little more aggressive, you know, I haven't heard of as many of these cases, like, for lack of a better term, circling the drain after anesthesia.
00:37:10
Speaker
So I've been pretty pleased with that. Now, whether or not that's changed the game, like you know, it's hard to tell, but... you know, that could all be speculation, but I've been a little bit more aggressive about my recommendations. And also I've been more aggressive about informing people that if their dog has like pretty, or cat has pretty advanced cardiac disease and they're unable to medicate their patients postoperatively, that I usually write, just straight off the bat, tell them that they should take their patient to a place for 24 hour monitoring
00:37:44
Speaker
And it comes up to them if they want to comply with that or not. But those are usually my recommendations. yeah I definitely think that going to seek alternative care is a great idea if they don't feel comfortable. Even sometimes I've had dogs who have been otherwise seems pretty happy and bright and alert.
00:38:00
Speaker
But the owner is nervous about being able to administer to them the additional medications in that period. And then it's worth going over and spending the night at the yeah ER so the ER can do that for them.
00:38:12
Speaker
Yeah. And mean, you don't want to make people feel bad that they're nervous, but I think getting people to confess that they have some trepidation about their ability to manage their patients postoperatively, especially in an outpatient setting is like really important. And part of this like communication about how we're going to deliver information to these owners with animals with pretty complex coexisting diseases. Yeah.
00:38:37
Speaker
Before we leave, because we're like almost at the end, I just would love if you could share an example of a successful anesthetic case that you've done involving a dog with mitral valve disease or a cat with hypertrophic cardiomyopathy.
Case Study: Pomeranian with Mitral Valve Disease
00:38:52
Speaker
I appreciate the opportunity because this was one of my favorite cases. We did little Mr. March approximately ah maybe two, three months ago. He was a nine-year-old male neutered Pomeranian. Names have been changed to protect the innocent.
00:39:05
Speaker
He was a stage C patient with a grade three out of six heart murmur that was underlying mitral valve disease. And once you are a stage C patient, You are permanently a stage c So his veterinarian had prepared him that really anesthesia would not be a good idea for him in the future. That's what she felt more comfortable with. And I cannot say that was wrong.
00:39:27
Speaker
But unfortunately, he developed a urinary stone. And The owners tried to manage as many urinary tract infections and tried to keep him comfortable. But it was becoming clear that this stone, which was now quite large, was going to negatively impact his quality of life. And so the veterinarian reached out to me and asked if I could provide virtual anesthesia support. They live in a state which might seem weird to you and I, Bonnie, that in Florida we have many anesthesiologists, but in this particular state they have to go out of state if they want to see an anesthesiologist. There are no physical anesthesiologists that live there.
00:40:02
Speaker
So good on them for finding an alternative option. So we had this particular dog that we provided the anesthesia services for, and we had an outstanding technician who worked with this animal had worked with this dog for years. So the owners felt very comfortable with that technician being the physical presence and me coaching him along.
00:40:23
Speaker
March was on Pimobendan, and so we definitely made sure he received that. He was also on Cardalis, which is a Benazapril and Spironolactone combination, and Clopridogyl. With the cardiologist's blessings, we stopped the carpalatural week in advance.
00:40:36
Speaker
And we asked the owners to withhold that dose of Cardalis the previous day. We knew already what his average resting blood pressure was. And so we knew what the target for him would be. And so we could try and manage manage that as best that we could by making sure that we had brought in some dopamine to the practice for them to be able to use. And we discussed with that technician how that was created. And we created that CRI in advance so that we were ready.
00:41:02
Speaker
He came into us already having on board His premedication of gabapentin, was a pretty chill guy, and so he only needed the gabapentin. We really wanted to make sure, though, that we maintained that chill attitude because in addition to his cardiovascular disease, he also had tracheal collapse on radiographs. And so we didn't want to do anything that was going to stress him and worsen both a respiratory airway component as well as the cardiac component.
00:41:31
Speaker
He was pre-medded with hydromorphone at 0.1 mg per kg and acepromazine at 0.01 mg per kg. He was a very compliant patient after that, and the gabapentin for his catheter placement. And we were able to pre-oxygenate him without any problems.
00:41:44
Speaker
We began to induce and then prepped and clipped him so that we were ready. The induction was with alfaxalone and midazolam. And then the veterinarian did a great job of making sure she did a line block, which is what she was most comfortable with. And with not me being physically present to offer any other blocks, I was happy to have that block on board for him. He did great throughout the whole surgery. We needed maybe an additional dose of glycopyrrolate to keep his heart rate up, but he did really well. And especially because that stone clearly bothered him. And when they got to the cystotomy portion,
00:42:18
Speaker
He was quite stimulated with all of that. We repeated his dose of hydromorphone and he seemed to become much more quieter. But then like they love to do while we were closing,
00:42:29
Speaker
He started to have this decrease in heart rate. He started to have a decrease in blood pressure. And so we did end up putting him on dopamine for support. And as I coached the technician through doing all of this, blood pressures came up. We then took our time to wean him off that dopamine over a 15-minute period.
00:42:47
Speaker
Postoperatively, we listened and escolted the lungs. They sounded great. We kept him warm, dry, and comfortable made sure he had the analgesia that he needed with everything. And my favorite part of the story is that the owners had for years thought their dog could never have anesthesia again because of his stage C, which I don't think is unrealistic or unacceptable in any way.
00:43:09
Speaker
But now his teeth are so bad the owners are actually going to try and set him up for a dental appreciating that would also potentially be staged depending on how significant his disease was. And so for this particular dog, not only were able to successfully get him through, but we were able to determine that it's not that he can never have another anesthetic episode. It's just that we need to be thoughtful about it. So I really love this little guy and I look forward to potentially helping him again.
00:43:36
Speaker
I love that you were able to convince the owners that we can anesthetize him successfully so that we can improve his quality of life. So that's really, that's a nice story.
00:43:47
Speaker
Yeah. Yeah. so to wrap this rather lengthy discussion up, first of all, thank you so much for taking so much time to talk to us and educate us about how to anesthetize patients with cardiac disease
Top Recommendations for Veterinary Professionals
00:44:02
Speaker
successfully. So I just wanted to, first of all, just thank you so much.
00:44:07
Speaker
And second, if you were to take like your top three recommendations from this discussion, what are they? What are your top three tips you can give veterinary professionals on how to manage anesthesia in dogs and cats with cardiac disease?
00:44:24
Speaker
All right. Yeah. So, I mean, like most of us, I definitely have my top three things that I like. One of my first things is that I feel like oftentimes it's very wonderful in general practice to have a cardiologist who gives recommendations for those patients. And so that's a wonderful service to be able to have.
00:44:45
Speaker
But do remember, a cardiologist and an anesthesiologist are not the same. And one thing that I notoriously see missed in the cardiac recommendations is the asking the vaporizer setting to be conservative. And so cardiologists will often say, don't use acepromazine, don't use dexamethetomidine, don't use ketamine.
00:45:04
Speaker
They'll say limit the fluids, but they don't often say be as conservative as you can with the vaporizer setting. And I have consulted for cases where they have followed either an internist or cardiologist recommendation to a T and the animal has still gone into heart failure afterwards.
00:45:21
Speaker
And the vaporizer setting, as you look over the record, is 3% to 3.5% for an isofluorine, which is way above MAC. And probably using additional opioids would have been able to cut them back. So if your cardiologist does a review for you, just keep in mind it's from an anesthesiologist perspective.
00:45:37
Speaker
Limiting the vaporizer is also a good idea for patients who have cardiac disease. Next point that I would suggest, and this is like words that, you know, I'll probably have inscribed on my tombstone.
00:45:48
Speaker
Two short anesthesias are better than one long anesthesia, especially with a patient who has comorbidities. And so if you have a patient who has ah very complicated and disastrous mouth, rather than trying to plow through all of that and knowing the patient is not doing well and desperately trying to salvage the situation, it's by far better in advance to speak to the owner and to say, this animal has years worth of disease, which is what one of my dentists like to say, I can't undo years worth of disease in an afternoon.
00:46:23
Speaker
And so breaking those sessions up into two separate sessions is going to be safer for the patient. And then triaging those that that procedure, whether it's dental or another procedure,
00:46:36
Speaker
That's complicated. Start with whatever is the most critical piece and then discontinue anesthesia if the animal is not doing well. to re-approach it after the animal has had a recovery period. So that'd be my second piece of advice.
00:46:48
Speaker
And the third piece of advice is that there are people out there, including myself, but not just me, that will offer virtual anesthesia services. And so if you are in an area where you don't have a physical anesthesiologist as an option, that is a great opportunity to be able to still offer outstanding anesthetic care and management for that patient.
00:47:11
Speaker
to be able to bring in a virtual anesthesiologist in this new, wonderful age of Zoom that we are living in. Well, thank you so much again for your time and being here and talking with us about managing anesthetic patients with cardiac disease.
00:47:26
Speaker
I appreciate it. Thank you, Bonnie.
Conclusion and Future Episodes
00:47:34
Speaker
Thank you for joining us today. If you enjoyed this episode, we invite you to explore the North American Veterinary Anesthesia Society and consider becoming a member. For just $50 a year for technicians and $75 a year for veterinarians, membership to NAVS provides incredible benefits, including access to anesthesia and pain management CE events,
00:47:57
Speaker
informative blog posts, fireside chats with board-certified anesthesiologists and specialty technicians, and so much more. NAVAS members also enjoy VIN rounds, hour-long presentations on specific topics in veterinary anesthesia that offer valuable tips to use right away in practice.
00:48:16
Speaker
You can get access to these topic rounds without being a VIN member, as long as you are a member of NAVAS. If you're interested, visit www.mynavest.org to elevate your anesthesia journey today.
00:48:30
Speaker
If you've been enjoying our podcast, we'd love your support. Please consider liking, subscribing, writing review, or sharing the podcast with friends and colleagues. Every bit of listener support helps us reach more veterinary professionals like you.
00:48:45
Speaker
For questions about this episode or the podcast in general, or to suggest topics for future episodes, feel free to reach out to us at education at mynavast.org. We'd love to hear from you.
00:48:57
Speaker
Special thanks to our sponsor, DECRA, for making this podcast possible. To learn more about their veterinary anesthesia products, visit www.decra-us.com.
00:49:10
Speaker
And of course, a big thank you to our esteemed guest, Dr. Carolyn McCune, for finishing up our discussion on anesthetic management of patients with cardiac disease. This episode was produced by Maria Bridges, edited by Chris Webster of Chris Webster Productions, with technical support from Saul Jimenez.
00:49:28
Speaker
Finally, thank you to all our gas pastors out there for spending time with us today on the Navas podcast. Veterinary anesthesia is a lifelong journey of learning and growth, and we hope you'll join us next month as we continue exploring it together. I'm your host, Dr. Bonnie Gatson. Thanks for listening and stay tuned for next month for another episode of the North American Veterinary Anesthesia Society podcast.