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Digesting 2020 AAHA Anesthesia and Monitoring Guidelines with Dr. Ioannis Savvas
737 Plays1 year ago
What fasting recommendations are you making for your elective anesthetic procedures? Are you recommending that all your patients be fasted overnight? This has been recommended by veterinarians to countless dog and cat owners for years. However, our human counterparts have changed these recommendations in recent years to shorter episodes of fasting before general anesthesia. The most recent anesthesia guidelines provided by American Animal Hospital Association have suggested a different fasting protocol for small animal patients prior to general anesthesia that look awfully similar to the updated human recommendations. What is the evidence that veterinarians should follow suit, especially given the intricate differences between the human and animal gastrointestinal systems?
To help us digest this huge topic is Dr. Ioannis Savvas, Professor of Veterinary Anaesthesia, Analgesia, and Intensive Care at School of Veterinary Medicine, Aristotle University of Thessaloniki and dedicated researcher specializing in the complex details of how general anesthesia impacts the gastrointestinal tract of dogs and cats. With host Dr. Bonnie Gatson, they will discuss the impact of general anesthesia on gastrointestinal motility, how often reflux and regurgitation occur in anesthetized companion animals, and strategies to mitigate these gastrointestinal complications. And of course, they will discuss what we know and don’t know when it comes to preanesthetic fasting protocols for dogs and cats.
We invite our listeners to check out articles mentioned in today’s episode: 2020 AAHA Anesthesia and Monitoring Guidelines for Dogs and Cats
If you like what you hear, we have a couple of favors to ask of you:
Become a member at North American Veterinary Anesthesia Society (NAVAS) for access to more anesthesia and analgesia educational and RACE-approved CE content.
Spread the word. Share our podcast and FB/IG posts, re-tweet, post something on a network or a discussion forum, or tell a friend over lunch. That would really help us achieve our mission: Reduce mortality and morbidity in veterinary patients undergoing sedation, anesthesia, and analgesia through high-quality, peer-reviewed education.
We also ask our listeners to save the date for the NAVAS Virtual Spring Symposium on April 27th and 28th, 2024. For more information about the program, visit the NAVAS Spring Symposium website. Dr. Savvas will be one of our featured speakers during the symposium talking more about adverse gastrointestinal effects of general anesthesia.
Thank you to our sponsor, Dechra - learn more about the pharmaceutical products Dechra has to offer veterinary professionals, such as Zenalpha.
If you have questions about this episode or want to suggest topics for future episodes, reach out to the producers at education@mynavas.org.
All opinions stated by the host and their guests are theirs alone and do not represent the thoughts or opinions of any corporation, university, or other business or governmental entity.
The NAVAS Podcast is published monthly on or near the 15th of the month.
Special thanks to Chris Webster for editing, producer Maria Bridges, and Saul Jimenez for IT support in making this podcast a reality.
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Transcript
Podcast Introduction and NAVAS Symposium
00:00:07
Speaker
Hello, all you gas pastors out there. Welcome to another episode of the official podcast of the North American Veterinary Anesthesia Society sponsored by DECRA, where we explore the latest advancements and hot topics in veterinary anesthesia to help veterinary professionals and caregivers advance and improve the safe administration of anesthesia and analgesia to all animals.
00:00:29
Speaker
I'm your host,
Anesthetic Fasting Protocols Overview
00:00:31
Speaker
Dr. Bonnie Gatson, and today's episode, we are going to sink our teeth into anesthetic fasting protocols with an overview of anesthesia's effect on the gastrointestinal system. But before we bite into this topic, I want to remind our listeners that the Navas Virtual Spring Symposium will be held on April 27th and 28th of this year. There is program content for veterinary technicians, general practitioners, and specialty veterinarians.
00:00:59
Speaker
Registration will begin on February 1st. Please visit the NAVAS website at www.mynavas.org to learn more about the program and speaker lineup. In fact, our guests for this episode will be speaking at the symposium, so hopefully this episode will give you a little taste of what to expect at the NAVAS virtual spring symposium.
Impact of Anesthesia on GI System
00:01:20
Speaker
So back to our episode for today.
00:01:23
Speaker
How does general anesthesia impact the gastrointestinal system and what can we do as anesthetists to mitigate problems related to the system, such as perianesthetic nausea, vomiting, and regurgitation? Well, let's think about this question this way. What fasting recommendations are you making for your elective procedures?
00:01:46
Speaker
Are you recommending that all of your patients be fasted overnight? And if so, why are you recommending that? Should you be recommending that? If you have been ruminating on these questions, then you are not alone. I have also wondered if the traditional overnight fast is what we should be endorsing for all of our patients, but I never felt confident in suggesting a different fasting protocol without solid evidence that it should be changed.
00:02:13
Speaker
There are so many other issues related to the gastrointestinal system that not only impacts the overall well-being of our patients, but also poses some practical considerations for veterinarians and their team.
Insights from Dr. Yannis Savas
00:02:25
Speaker
To help us digest this huge topic and process the evidence is Dr. Yannis Savas, a professor of veterinary anesthesiology in Greece, and a dedicated researcher specializing in the intricate details of how general anesthesia impacts the gastrointestinal system of dogs and cats.
00:02:43
Speaker
Together, we will discuss its impact on gastrointestinal motility, how often reflux and regurgitation occur in anesthetized companion animals, and strategies to mitigate these gastrointestinal complications. And of course, we will be discussing what we know and what we don't know when it comes to pre-anesthetic fasting protocols for dogs and cats.
00:03:04
Speaker
So, if you are a veterinary professional eager to enhance your knowledge, stay tuned as we unravel the mysteries surrounding the gastrointestinal effects of general anesthesia. By the end of this episode, I hope you feel more confident recommending appropriate pre-anesthetic fasting protocols that suit each patient's needs.
00:03:22
Speaker
Understand how to judiciously include gastrointestinal protectants and antiemetics in an anesthetic protocol, and learn the best ways to prevent gastrointestinal reflux and regurgitation in dogs and cats undergoing general anesthesia. And please remember to subscribe to the NAVAS podcast on your favorite podcast platform to stay updated on the latest in veterinary anesthesia. Let's begin.
00:03:50
Speaker
Okay. Hi, welcome to the NABAS podcast. We can start off our conversation by telling me a little bit about yourself and what your current role is. Hello. I'm very glad to be here. My name is Ioannis Savas. I'm a professor of anesthesia and analgesia intensive care at the school of veterinary medicine. I studied at the University of Thessaloniki in Greece.
00:04:13
Speaker
So I'm very excited to be speaking with you because I'm all the way in Florida. So we're like on the opposite sides of the world. So I'm really excited to have you on today, not only because it's really cool to talk to somebody in a different part of the world, but also because we're going to talk today about a topic that we already talked about this before we started recording, but I feel a little bit behind personally on this topic.
00:04:41
Speaker
And sometimes I work as an anesthesia consultant. I feel like sometimes people call me and they want to update their fasting protocols. Sometimes I'm not sure exactly what to tell them outside of what I've traditionally recommended in the past, which is
00:04:59
Speaker
to fascinating animal for eight hours. So I'm just really glad that we can have you on to try to see what should we be recommending and what do we know and what we don't know. So before we jump into that conversation, I always ask all of my guests this question. Why are you interested in anesthesia? What drew you to anesthesia? That's very nice question. The first answer I comes to my mind is I don't know. I have no idea.
00:05:29
Speaker
I graduated from the veterinary school and anesthesia just popped up in front of me and I said, yes, I like that discipline and I will follow it. That's my answer. I have no idea why I'm interested in anesthesia. I like it very much, really very much. I like to do research in veterinary anesthesia. I like to teach veterinary anesthesia and I enjoy it very much.
00:05:51
Speaker
So, are you saying that you kind of fell into it in veterinary school and then as you were practicing more, you kind of fell in love with the topic more and more as you continued to practice? Yes. Yes, exactly. That's a lovely answer. I also relate to that. I'm sure guests have heard me say this before, but before I started veterinary school, I didn't even know anesthesia was a specialty.
00:06:16
Speaker
And then I found out there was actually a veterinary technician that pushed me into it. And I'm very grateful because I also feel very passionately about veterinary. So it was love at first sight for you as well. Yeah, honestly, it was.
00:06:33
Speaker
Yeah, I really enjoyed rotating through my anesthesia rotation, but I don't think it was until one of the technicians I was working with was like, you know, you could specialize in this, that it clicked.
Preoperative Fasting and GI Complications
00:06:46
Speaker
And I was like, yep. Yes, exactly. Yeah. Okay. So another part of this question, why did you focus your research career on the gastrointestinal effects of general anesthesia in small animals?
00:07:02
Speaker
Well, when I started to believe that I would be doing anesthesia for the rest of my life, I started to find some topic to do my PhD research.
00:07:14
Speaker
Looking at the front lines of veterinary anesthesia research, I found that there is a lack of information on preoperative fasting, on preoperative guidelines, on how would you, would we as anesthetists fast our patients before giving anesthesia. And that came from human anesthesia research
00:07:39
Speaker
which is a topic that where the human anesthetists had a big problem with preoperative fasting. And there's a lot of research in human medicine, so I started to search for evidence on preoperative fasting in veterinary medicine and I found nothing. There was a colleague before me that had done some preliminary research on this topic and I decided to follow him
00:08:09
Speaker
and make my own research on this topic. Preoperative fasting, gastric exposure, reflux, gastric contents, and gastric acidity. Okay, so I'm so glad that you jumped into this research because there really isn't very much out there in the veterinary literature. So whatever you have contributed has really, I think, helped us understand things, even if just a little bit.
00:08:38
Speaker
a little bit clearer. Let's jump into the gastrointestinal effects of general anesthesia. Do you think you can briefly summarize what we know about what effect general anesthesia has on the gastrointestinal system?
00:08:56
Speaker
Well, the main effect of general anesthesia on GI tract is the relaxation of the lower spageal sphincter. And this may affect how the gastric contents move. And during anesthesia, we well know that the lower spageal sphincter relaxes. So the gastric content passes through the lower spageal sphincter back to the esophagus.
00:09:24
Speaker
And this is a main concern for the veterinary anesthesia. The same phenomenon may be seen during the human anesthesia.
00:09:36
Speaker
And very interestingly, the same exact phenomenon can cause two different kinds of results to the patient. So in human medicine, the gastric spodum reflux and detection of anesthesia may cause aspiration of gastric contents into the trachea and the lungs. On the other hand,
00:09:58
Speaker
This is not very commonly seen in dogs and cats, but this gastrous audio reflects back to the esophagus. It does not cause any aspiration, but it can cause severe inflammation of the esophagus, severe esophagitis. And later on, days or weeks after the anesthetic episode, this inflammation may lead to esophagia stricture, which is a very serious condition in dogs and cats.
00:10:27
Speaker
I am sure most of our listeners have at least experienced one of these complications in their anesthetic patients. So we'll talk about how common it is, hopefully at some point. So even though it might be an uncommon, relatively uncommon effect, I'm sure that a lot of people have had personal experience with one of these pretty devastating complications.
00:10:50
Speaker
So what kind of role does visceral pain have on the gastrointestinal system? Well, when we are talking about pain, it's not exactly pain during general anesthesia. We are talking about nociception because we don't have consciousness during general anesthesia. So there's no perception of
00:11:11
Speaker
painful stimuli by the patient. So any manipulations in the abdominal cavity during surgical operation may affect the gastric tone, sympathetic and parasympathetic, and also can increase abdominal pressure. Because the main factor that
00:11:32
Speaker
affects the occurrence of gastrosophageal reflux is the barrier pressure. The barrier pressure is the difference between the lower esophageal pressure and the intra-gastric pressure. If for any reasons the lower esophageal sphincter pressure is lowered, all the intra-gastric pressure or intra-abdominal pressure is increased,
00:11:56
Speaker
then the barrier pressure is decreased and the gas recompense pass through the stomach, through the lower spudural sphincter to the esophagus. So any manipulation or any stimulation of the intra-abdominal organs, yes, may affect the development of gaseous spudural reflux during anesthesia.
00:12:18
Speaker
This is an offshoot question, but I just wanted to clarify. So the primary reason you're anesthetizing the patient has nothing to do with the GI tract, but just like being inside an animal's abdomen that leads to gastroesophageal reflux. Yes, exactly. Any manipulation we are done now have seen any organs can develop gastroesophageal reflux, the animal.
00:12:41
Speaker
Yeah, it's a really good point and one that I hadn't really thought of before.
Anesthetic Drugs and GI Effects
00:12:45
Speaker
One more question about the effects of general anesthesia on the GI tract is that many of the drugs we use for anesthesia in small mole patients affect gastrointestinal motility
00:12:57
Speaker
and the integrity of the lower esophageal and pyloric sphincter. So do you think this, I mean, this is a huge topic in and of itself. It could probably spend a lot of time talking about this, but I wonder if you could just give a few examples of some of the more commonly used medications.
00:13:13
Speaker
and just briefly summarize what their gastrointestinal effects are. Yes. There is a lot of work, a lot of research, mainly in humans, but in animals as well, on the effect of several drugs used periodically on the development of GOR or GER.
00:13:33
Speaker
There has been a lot of research on alpha-2 agonists, on aspromazine, on inhalation anesthetics, on induction agents like thiopendon or propofol. But the drugs that they mostly affect, the gastrocodial reflex, are atropine and opioids.
00:13:54
Speaker
So there has been a lot of research on these drugs and we have evidence that atropine and opioids affect the tone of the lower spodule sphincter and they are responsible for the development of GOR in dogs and cats. These are the main drugs.
00:14:15
Speaker
Interesting. Back when I used to work with a lot of internists who did lower esophageal and lower GI scoping procedures, they would be very strict about the fact that we could not use opioids, like full mu agonist opioids. They were only allowed to use things like butorphinol or an opioid-free protocol.
00:14:38
Speaker
in the animal's anesthetic protocol because their concern was their inability to pass the scope from the stomach into the duodenum. I'm curious if that, is that something that we should actually be concerned about? Well, there's not enough evidence on these, but definitely you can pass the scope from the lowers of the dual sphincter. This is for sure that the opioids, the full, we opioids make the lowers of the dual sphincter to relax.
00:15:06
Speaker
so you can pass the scope from the lower sphincter. Regarding the caloric sphincter, we don't have much evidence. I think that this is mostly observation of the internists. But when we anesthetize the animals, we give a lot of drugs. We give alpha-2s, we give induction agents, we give inhalation anaesthetics, and we also give some opioids. The net effect of the sphincters
00:15:35
Speaker
is not known. So I'm not sure that it's a real problem if we give some opioids in these cases.
Reflux Risks and Management
00:15:44
Speaker
Excellent. So now that we have a general understanding of what the effects of general anesthesia are on the gastrointestinal tract, we're going to focus in now
00:15:56
Speaker
on gastroesophageal reflux and regurgitation. And I think we need to start by defining some terms. So what's the difference between reflux and regurgitation? And I think instead of reflux, we're going to use G-O-R or G-E-R, depending on if you are European or American.
00:16:17
Speaker
Well, the gastric spudier reflex is the passage of gastric contents from the stomach to the esophagus. And this contents mainly stays there. So in case that the content is too much,
00:16:32
Speaker
and it goes upper and upper and it reaches the pharynx and then goes out from the mouth. This is regurgitation. It has been shown that the gaseous adrenal reflex incidence may be up to 50 or 60% during general season dogs, but the observation of gaseous contents out of the mouth is much, much less. It is less than 1%.
00:17:03
Speaker
So, in many, many cases, we have gastrosprogia reflux in our patients, but we never know it. We don't know this because it doesn't come out of the mouth. We don't have regurgitation. And this is a big problem because after some days and some weeks, the dog or the cat develops as a projectus.
00:17:24
Speaker
Yes. This would always kind of scare me as a resident. And it still kind of does to think that there's a huge percentage. Did you say 60 to 70%? 50 to 60. Yeah. Some, some researchers report more than 60%, especially when we, when there is an opioid, including the permittication. Yeah. So that's like a huge percentage of our patients that have silent reflux. Exactly. This is called silent reflux.
00:17:54
Speaker
So I always felt that when I was studying anesthesia as a resident, this would always scare me. Once I learned this fact, I started passing a lot of gastric tubes in my patients at the end of the procedure.
00:18:10
Speaker
And my mentors were telling me essentially that, you know, maybe this was not necessary because the percentage of animals that are actually developing clinical problems is very low. So do we know of the animals that are experiencing reflux, which is a huge percentage, how many of these animals go on to actually develop clinical esophagitis or aspiration?
00:18:36
Speaker
Yes, aspiration is very, very rare. We actually have only one case, as far as I know, in veterinary anesthesia literature. We have one case of aspiration, but we have some other cases like inflammation of the pharynx. We have some renitis, inflammation of the nose and the cavities, but we don't have aspiration, which is very, very common in human medicine, in human anesthesia.
00:19:04
Speaker
Regarding the incidence of esophagitis, we actually do not know because some patients after anesthesia, they're coughing for some hours or some days, or they have some dysphagia for some days, and we don't
00:19:21
Speaker
give anything, any medication of these, or the owners don't give anything, and it passes after a few days. These could be summer's phagitis, mildest phagitis. Severe phagitis with spodier stricture, yes, it's not so common, but it can develop. It may be up to 5% or 10% of the dogs that develop gastric spodier reflex during anesthesia.
00:19:48
Speaker
Well, exactly, we don't know the exact number, but there have been reports for up to 5% or 10% of these animals can develop severe phagitis, which may lead even to death or euthanasia.
00:20:02
Speaker
Yeah. I'm very fascinated by the idea that animals that are coughing after anesthesia, it might be reflux or just like a very mild piece of reflux. I feel like most of the time we blame the endotracheal tube. Yes. Yes. That's true. That's true. But it, it could be a GOR and in my dyspagitis.
00:20:27
Speaker
Yeah, that's really interesting. That's like an aha moment for me. Okay, so there's a huge percentage of animals that are experiencing the silent regurg that we've talked about. I know there's been some research looking into risk factors, like what we know, at least maybe drugs we use or certain breeds of dogs and things like that, or certain procedures.
00:20:52
Speaker
What risk factors do we know that increase the risk of perioperative reflux and regurgitation? Yeah, we've talked about the drugs, mainly atropine and opioids, full meopioids, agonists. And there are some other factors like the intra-abdominal operations. Anything that can increase the intra-abdominal pressure
00:21:18
Speaker
increases the possibility of development of GOR. So, interdominal operations or any manipulations during, you know, you try to move the patient from one table to another or you move the patient from the induction room to the diagnostic room
00:21:40
Speaker
Any manipulation that increases the intraodontal pressure may also increase the instant of GOR. And another factor could be the position of the animal for the surgical operation. If you put the animal with the head down position,
00:21:59
Speaker
then you increase the instant of GOR because the gravity may increase the instant of the Gaussian contents that pass through the lowest produce printer to the esophagus. Are there any other types of procedures? I feel like in my memory,
00:22:16
Speaker
there was some increased incidence of reflux associated with orthopedic procedures and also maybe hemilaminectomies. Is that true or am I just pulling that out of nothing? According to my research, we don't have enough evidence to say that the orthopedic operations are more related to GOR. It's probably the positioning of the animal.
00:22:44
Speaker
If you put the animal with the head down position or for any reasons you increase the intraabdominal pressure, even if you're doing an orthopedic procedure, you may affect the incident of GOR. So it's not the orthopedic operation per se.
00:23:01
Speaker
Yeah, that's what I was just about to say is I feel like it's more that a really good example is TPLOs. So I feel like the animals are initially in dorsal and then they're laying on their side. Exactly. And we're flipping them back and forth to get radiographs. So to me, I feel like it's way more the fact that we're just constantly rolling this animal around as opposed to the procedure itself. Even if you're not anesthetized, you will cause a reflex to these animals.
00:23:31
Speaker
Right. I want to focus on a little bit on breeds of dogs. I don't know if French Bulldogs are as popular in Greece as they are in the United States. They are very, very popular in Greece and in Europe.
00:23:47
Speaker
Yeah, I feel like every other case I have to work on is a French bulldog. I want to focus on French bulldogs and break use of phallic breeds for just a moment because I feel like that is a breed that has been labeled as one that has a higher incidence
00:24:04
Speaker
of developing regurgitation or aspiration pneumonia. So in your research, have you looked into specifically drugs or protocols that you're looking at to reduce the incidence of regurgitation in this breed, if that's even true?
00:24:21
Speaker
Well, first of all, I'm not convinced that the brachycephalic dogs in general, not on French bulldogs, are more prone to the development of GOR. Because we've done a systematic review two or three years ago, and we didn't find enough evidence to support this conclusion that the brachycephalics are
00:24:44
Speaker
develop more easily GOR. So I believe that it's more like the type of operations and not the breed itself. So there is a retrospective study that found that if we give some antiemetics in these dogs,
00:25:06
Speaker
In Brachycephalics, we reduced the incidence of reflux, but it is a retrospective study and we need more evidence with prospective studies. And according to my research, we also found that there is no difference between barrel-shaped and deep-chested dogs regarding the development of GOR during anesthesia in spinal cord surgery.
00:25:29
Speaker
So, and again, according to our systematic review, we cannot support that the brackets of our leaks are more sensitive to GOR. Oh, that's really fascinating because I feel like there's so much literature out there about different like anti-emetic protocols you can give to break style. But maybe you're challenging even the initial premise, which is fascinating. Yeah.
00:25:56
Speaker
Are there any known medications that can be used in the perioperative period that prevent or decrease the risk of perioperative reflux or regurgitation?
Research and Recommendations on Fasting
00:26:07
Speaker
Again, there is very little evidence, but I would say that the best evidence we have so far is the use of omeprazole.
00:26:16
Speaker
which is a percompound inhibitor. So there is at least one clinical research that says, that has shown that omicrosol may reduce the incidence of GOR during general anesthesia in dogs. So this is the only clear evidence we have so far, omicrosol.
00:26:36
Speaker
And that's really interesting because if you're going to use it at Brazil, my understanding is it takes a few days of administration to reach peak effect. So it's not really like a quick fix. If you're worried about, you have to worry about reflex, you kind of have to plan for it. Yes, exactly. That's really interesting. Do we have evidence about the use of metaclopromide and its role in general anesthesia at all?
00:27:02
Speaker
We don't have any clear evidence on metaglochromide. Metaglochromide is generally an antiemetic. And during general anesthesia, we're talking about reflux, not vomiting. So I'm not sure that has any effect on the reflux mechanism during general anesthesia. Anyway, it is supposed to increase the loss of adrenal sphincter pressure
00:27:27
Speaker
But we don't know the exact effect during general anesthesia, because there are other drugs affecting the lower soldier's finger as well. So we don't have clear evidence regarding the use of metropromide during general anesthesia. What do we know about cats? I feel like cats are often neglected in these conversations.
00:27:50
Speaker
What do we know about cats and their risk of reflux and regurgitation under general anesthesia?
00:27:58
Speaker
Yes, cats. I have to say that I'm a cat lover, so we have even less evidence on cats related to the incidence of gastrocipital reflex. We do have some evidence regarding the use of propofol and the opioids, but we have very, very few clinical research studies on cats.
00:28:26
Speaker
There is some evidence that the cats can develop spagitis post-operatively and the spagio-stricture. It is even less than the incidences, the incidence is even less than the dogs, but they can still develop spagitis and spagio-stricture post-operatively.
00:28:46
Speaker
So what I hear you saying is that if there's anybody out there who loves cats and is like a budding researcher, please reach out so we can learn more about cats and gaseous digital reflux. Yeah.
00:29:04
Speaker
So we're going to delve a little bit more into pre-anesthetic fasting protocols because I feel like this is a huge area of, I don't want to say like debate, but you do see a lot of people out there with very strong opinions on this. And I'm so glad to have you here so we can kind of talk about what the evidence shows as far as these are concerned. So I guess the first big question is, does the pre-operative fasting protocol
00:29:34
Speaker
decrease the risk or alter the risk at all of perioperative reflux and regurgitation? The answer here is yes. The duration of the preoperative fasting can affect the incidence of reflux during general anesthesia.
00:29:51
Speaker
I have to say here that the traditional preoperative fasting in humans is related to this phenomenon, the aspiration of gastric contents at the induction of anesthesia. We definitely know that the intubation in human patients is very difficult, much more difficult than the carnivores.
00:30:14
Speaker
and they use mass relaxation to intubate the patients. And during that time, at induction, there is a development of gastropodular reflux and aspiration of gastropodular components. This is the most dangerous time during induction of nephronosusia in humans. So traditionally, the human anesthetists were trying to reduce the incidence of gastropodular reflux at induction by inducing
00:30:44
Speaker
a long time of preoperative fasting. That was nothing by mouth after midnight rule. So traditionally there was a long fasting time preoperatively in humans. That was more than 8 or 10 hours or 12 hours in some cases. And we are talking about scheduled operations.
00:31:07
Speaker
So when we started to study guesses for zero reflects in dogs, we found that the same rules apply to dogs and cats as well. And it was nothing more than.
00:31:19
Speaker
the application of the human rules in veterinary medicine. So my main research was to see if the preoperative fasting time could affect the incidence of gaseous apogeal reflux. And we have found and we have strong evidence that the reduction of preoperative fasting may reduce the incidence of gaseous apogeal reflux in dogs.
00:31:49
Speaker
Not very strong evidence in cats, but in dogs, we can say that the reduction of preoperative fasting may affect the incidence of cancerous module reflux. We do not know yet the exact, the optimum preoperative fasting time. I had some research on three or four hours before anesthesia.
00:32:11
Speaker
and 10 to 12 hours before anesthesia. And we found that the group that fasted three to four hours before anesthesia, they had much more lower this gastric majority flex percentage. So we can say that the reduction of preoperative fasting may be beneficial. And this is the case also in humans. In human cases, the current preoperative
00:32:37
Speaker
fasting guidelines are for four to six hours with a light breakfast. The light breakfast means a toast with some juice or tea, something like that, four to six hours per opportunity. The main problem I can see with these rules and these guidelines is how we implement
00:33:05
Speaker
in the current scheduling of the operations in our clinic, because this is a problem in human medicine as well. There have been a lot of studies showing that even in humans, they cannot implement these guidelines in the everyday clinical practice. For instance, the anesthetists say, let's ask this patient for six hours,
00:33:31
Speaker
Okay, the nurse then applies eight hours of preoperative fasting. The patient themselves apply more than eight hours because they know about the aspiration and they are anxious for the operation. So they apply, they don't eat anything for more than 10, maybe 12 hours preoperatively. So they go to the operation room
00:33:59
Speaker
with long fasting and some of them even dehydrated. So this is the problem I see with the implementation of these guidelines in veterinary medicine as well. Let's say that you have scheduled an operation at 10 o'clock in the morning. If we apply a four or six hours preoperative fasting, that means that you have to wake up at four o'clock in the morning to feed the dog.
00:34:28
Speaker
It's not very easy, even if the dog is hospitalized. On the other hand, if we feed the dog at eight o'clock in the morning, then you have to do the operation in the afternoon.
00:34:41
Speaker
So this is the big problem with applying these guidelines to the everyday clinical practice. I don't know how we can cope with this, but definitely we need more research to define exactly the preoperative fasting time. And I find very, very interesting the guidelines of the American Animal Hospital Association. They recommend for four to six hours preoperative fasting.
00:35:09
Speaker
I agree with this, but I had to add here that when we are talking about a reduced preoperative fastened time duration, we have to make clear that that includes
00:35:24
Speaker
only half the daily dose of canned food, not dry food, because dry food needs a lot of time to pass through the stomach to the intestines. So we have to be very clear on this. If we apply four to six hours of probabilistic fasting, we have to give canned food or homemade food and half the daily dose, not the full dose.
00:35:51
Speaker
because we increase the gas and contents volume if we breathe the full dose. Yeah, I was going to, you covered a huge range of things that I'm going to ask about. I'm just going to break down a few of those things. So the first part of that I want to cover is about the consistency of the food. If the dog, for example, normally eats dry food, you would still recommend and the owner is just not going to feed canned food or the dog's picky or something like that.
00:36:21
Speaker
Would you at that point recommend the traditional like overnight fasting or would it be okay to like wet or create like a mush of the dry food and cut it in half you know four to six hours before the procedure? What do we know about that? I wouldn't recommend a 12-hour fasting for dry food.
00:36:40
Speaker
Long fasting is not good. Long fasting is not good. So I would recommend the last meal should be canned food or homemade food. Interesting. Okay. Or six hours beforehand. Okay. So I want to ask about these guidelines that just recently came out. They are the American Animal Hospital Association Anesthesia and Monitoring Guidelines. And they do suggest fasting protocols, as you kind of alluded to, for healthy patients,
00:37:08
Speaker
as compared to patients that are at risk of regurgitation, which we've talked about some of those risk factors now. And so for healthy patients, the recommendations are to withhold food for four to six hours without withholding water for healthy patients. I just want to emphasize that. But for patients with an increased risk of regurgitation, the guidelines recommend withholding food and water for six to 12 hours.
00:37:36
Speaker
So according to your research and what you've summarized, I just want to be clear, are you supporting these guidelines or are there more kind of nuances to that? And what I'm hearing so far is, and correct me if I'm wrong, you're saying you support these guidelines, but you find the implementation of these guidelines is going to be challenging.
00:37:58
Speaker
Yes, exactly. I agree with these guidelines for healthy patients for elective surgery, not emergency surgery of course, and four to six hours fasting period before induction of anesthesia with half a daily dose of canned or homemade food
00:38:18
Speaker
I believe is the best recommendation we have according to the evidence from our studies. I'm not sure about the high-risk patients because we don't really know which are these patients, the high-risk patients. Are they really the brachycephalic breeds? Maybe, but there's no clear evidence.
00:38:44
Speaker
I would say six hours for these patients is also okay. Okay. Not more than eight or 10 hours. It's too long.
00:38:56
Speaker
Right. That's really interesting because I do find, you know, sometimes in a busy surgery day, I'll have, if I'm, if I'm consulting somewhere, you know, I'll have like five or six patients ready to go. And we're not getting to the last patient until, you know, two, three, four o'clock in the afternoon. And these are animals that have been fasted overnight.
00:39:18
Speaker
And so these might be the patients that we might need to reconsider. Like if it's a healthy patient that's going at the end of the day, maybe giving them half their daily, like normal intake of food, maybe in the morning and let them sit over, you know, throughout the day and then they go in the afternoon, which would be interesting. I have not done that, but it might be something definitely to consider.
00:39:42
Speaker
Yes. That these animals with very long fasting times, maybe 12 hours at this point, possible 10 hours, that those are the animals that are actually at greater risk of developing reflux and regurgitation.
00:39:55
Speaker
Interesting. Because there's another factor that affects the development of GOR, and I forgot to say about that, it's the gastric pH. If you fast for a long time, the dog or the cat, the gastric pH goes down to two or even one, which is very, very acidic gastric content. And even a small amount of gastric content goes back to the esophagus,
00:40:21
Speaker
for even for half an hour or one hour, this extremely acidic content may do much more harm to the esophagus than food maybe, okay, which has a pH of four or five.
00:40:37
Speaker
after you ingest the canned food or the homemade food. So the long fasting is not good for the lower smogill sphincter and for the esophagus in case we have a GOR. Interesting.
00:40:54
Speaker
Okay, last question about this, but if you can't avoid this long fasting, which is possible, I mean, it's just a normal part of life. Like sometimes we're going to be enough sizing patients at the end of the day that's been fastened a long time.
00:41:10
Speaker
Would your recommendation or do we have any evidence that using antacids, maybe close to the perioperative period, might be helpful, like a dose of famotidine or something like that, if we know that there is going to be this long fasting time that's going to drop the gastric pH down?
00:41:30
Speaker
Again, we don't have very good evidence on this. We have some retrospective studies saying that if you give famotidine along with metropromate and a restrictive use of opioids may affect the incidence of GOR, mainly by altering the pH of the gastric contents. But I can say again that we don't have very clear evidence on this. We need more prospective clinical studies.
00:42:00
Speaker
Okay, so I'm going to jump now from fasting recommendations to use some anti-medic agents. This has become really popular, at least in America, is to include anti-medics in the perioperative period. I think the one that is most commonly used is Serenia.
00:42:24
Speaker
People love serenia and for good reason, it's a great drug. But I wanted to talk a little bit about your opinion on this. So what are the benefits of including anti-medics in the anesthetic protocol? Yeah, again, as I said before, these drugs are anti-medics. That means that they prevent or reduce the incidence of vomiting in awake animals.
00:42:51
Speaker
We really do not know what are the effects of these drugs during general anesthesia, because we use so many drugs for premedication, taction, and maintenance of anesthesia, and we don't know really the net effect of these drugs during general anesthesia. Yes, serenia is a good drug, more competent, and I use it periodically, but I'm not
00:43:16
Speaker
Sure, I don't have evidence on how it behaves during general anesthesia in dogs that are at risk of GOR. I cannot say anything.
00:43:31
Speaker
Yeah, I very much agree with what you were saying in that when I include serenia in my anesthetic protocol, I'm doing it potentially to prevent vomiting during the pre-medication phase, if I'm concerned about that. And also in the post-operative phase to prevent vomiting associated with general anesthesia. But I think the evidence
00:43:58
Speaker
shows that there's very little evidence that it has any effect on gastroesophageal reflux. Is that correct? Yes, exactly, exactly. I totally agree. I use the drugs and especially serrhenia periodically for the reduction of incidence of vomiting before anesthesia and after anesthesia. But during anesthesia, we don't have evidence.
00:44:22
Speaker
Yeah, excellent. My last question, at least about this topic, is that Serenia, at least in the United States, is really expensive.
Antiemetics and Anesthesia Protocols
00:44:30
Speaker
And so for very large breed dogs, I mean, we're talking like hundreds of dollars for a dose potentially, depending on where we're getting the drug and what the clinic is charging and things like that.
00:44:42
Speaker
So, for some practices, they're interested in looking at other antiemetic agents to serve a similar purpose, meaning to prevent vomiting in the preoperative or postoperative phase. Do you know if there are other drugs like, for example, like Reglin,
00:45:01
Speaker
or Zofran, for example, which I also very much love Zofran on dazetron. Do we know if other drugs are as effective as Threnia to prevent preoperative and postoperative vomiting? Do we have any evidence about that? Actually, no, I don't have any evidence. I have used some of them, but there is no clear evidence. I think that the best drugs we have to prevent vomiting is metropromide and maropitant.
00:45:25
Speaker
at this point. So I would recommend only these drugs if we need to reduce the incidence of vomiting periodically. Okay. So I want to pick your brain as far as to summarize what we've talked about. So what would your pre-anesthetic fasting recommendations be? You know, if someone picked up the phone and asked you your opinion, what would your pre-anesthetic fasting recommendations be for a healthy dog and cat?
00:45:55
Speaker
And then we're going to jump into critical patients after that. So let's just start with healthy patients. Yes. Healthy patients for elective surgery. I would recommend a four to six hours per operative fasting with half the daily dose of canned or homemade food.
00:46:13
Speaker
And that depends on how you schedule your operations during the day, but that would be the operation, that would be the recommendation file, four to six hours per operatively. And I would suggest not giving the opioid, if you use opioids, not giving the opioids with the premedication with the other premedicants. I mean, give an alpha two or as promising or whatever you give,
00:46:43
Speaker
for the sedation of the animal, then go to the induction. We have seen from our research that most of the cases of GOR occur during the first five or 10 minutes after induction from seizure. Interesting. So you intubate the animal, you start to prepare for the surgery and then give the opioid. Definitely before the first cat, before the surgery, but
00:47:12
Speaker
after a few minutes after the induction of anesthesia. I would suggest that that would be a good practice because maybe you reduce the incidence of gastric body reflux at the induction of anesthesia.
00:47:27
Speaker
For this healthy population, what about access to water? Do you give them access to water all the way up until the beginning of the procedure or when do you pull water for them? For healthy adults, dogs and cats up to two hours before anesthesia is okay. You know, if there's anesthetic emergencies, a lot of times these animals cannot be fasted. So how are you going to approach that situation clinically to minimize the chance of regurgitation and reflux in that population?
00:47:57
Speaker
Yes, in emergency cases, we cannot apply obviously fasting. So I would recommend a rapid sequence induction protocol so that you take control of the airway as soon as you can, so that you prevent the incidence of aspiration because this is your main concern in emergency cases. If you have a dog with full stomach, he had a car accident,
00:48:23
Speaker
and it has to be operated very, very fast, rapidly, then the only thing you can do is to intubate as soon as you can, as fast as you can, so that you prevent any aspiration of gaseous contents into the lungs. That's my recommendation for emergency
Handling High-Risk Anesthesia Cases
00:48:45
Speaker
cases. Rapid sequence detection or crash detection, as we say sometimes.
00:48:52
Speaker
So that's also what I recommend for animals that have a high chance of developing reflux and regurgitation. So another good example would be like cesarean sections. So I also like to do rapid sequence inductions in that population because they also, that's a populate pregnant animals. That's another population of animals at high risk of reflux.
00:49:14
Speaker
Last question is about your recommendations for the use of antacids and antiemetics in the perioperative period. Do you always include them? Do you include them sometimes in certain cases? I'm just curious what your recommendations are.
00:49:33
Speaker
We've talked about the antiemetics. I can use antiemetics for the reduction of the vomiting incidence preoperatively and postoperatively, but there's no evidence for what they can do during anesthesia on the incidence of gastrosophageal reflux. Regarding the antacids, we have some evidence, not very clear, but I don't routinely use antacids in my clinical practice in university.
00:50:02
Speaker
And I cannot recommend either the use or not use of these drugs. We still need more evidence on these drugs very openly. So here's another call for people to come into the realm of gastroesophageal effects of anesthesia, come study antacids. Yes, yes.
00:50:24
Speaker
Well, thank you so much for spending time speaking with me today about this topic.
Conclusion and NAVAS Promotion
00:50:30
Speaker
And I think you've given me a few things to think about even in my own clinical practice. So I just really appreciate you taking the time to speak with me. Thank you so much. It was very interesting and I enjoyed very much this conversation. Thank you very much for inviting me.
00:50:46
Speaker
I know you're also a podcaster, but I assume your podcast is in a different language. Well, yes, I'm a podcaster. The most episodes are in Greek, but I try to change in English as well, so I will be open to a greater audience. I'm going to put a link to your podcast into the show notes. Okay, well, thank you again so much.
00:51:14
Speaker
If you like what you heard today, I encourage you to check out NavAss and consider becoming a member. As a member of the North American Veterinary Anesthesia Society, you get tons of benefits, including access to CE events, focusing on anesthesia and pain management, blog posts, fireside chats with boarded anesthesiologists, as well as specialty technicians, and just so much more.
00:51:38
Speaker
visit www.mynavas.org to advance your anesthesia journey today. As a reminder, the Navas Virtual Spring Symposium will take place on April 27th and 28th of 2024. If you enjoyed this conversation, Dr. Savas will be a featured speaker at the Navas Symposium
00:52:00
Speaker
where he will be diving even deeper into the gastrointestinal effects of general anesthesia. For more information, including other speakers and topics that will be presented, visit www.mynavas.org slash 2024 dash spring dash symposium. Registration for the symposium will begin on February 1st.
00:52:25
Speaker
If you have been listening and enjoying this podcast, I would sincerely appreciate it if you would give us a like or subscribe to our podcast, write a review, or simply just tell a friend about this podcast. We appreciate any and all listener support.
00:52:43
Speaker
If you have any questions about this week's episode or the NAVAS podcast in general, or if you want to suggest topics you would like for us to discuss in future episodes, please reach out to us at education at mynavas.org. We would love to hear from all of you.
00:53:01
Speaker
Also, a huge thank you to our sponsor, Decra, without whom this podcast would not be possible. Visit their website, www.decra-us.com to learn more about their line of veterinary anesthesia products. This podcast was produced by Maria Bridges, edited by Chris Webster of Chris Webster Productions, and technical support was provided by Saul Jimenez.
00:53:28
Speaker
I want to thank our guest, Dr. Janice Savas for this insightful discussion. And lastly, a huge thank you to all the gas pastors out there who choose to spend their time with me today on the Navas podcast. Becoming a skilled anesthetist is a lifelong journey of learning and self-discovery, so I hope you consider listening in the future. I'm your host, Dr. Bonnie Gatson, and thank you for listening.