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A Deep Dive into Fluid Therapy with Dr. Jane Quandt - Ep. 13
551 Plays1 year ago
Water is life’s matter and matrix, and there is no life without it. Even the founding fathers of the US understood that water was essential to sustain life, with Benjamin Franklin being quoted as saying “When the well’s dry, we know the worth of water.”
Patients often present to veterinary hospitals with a dry well, and many of them may require diagnostics or surgery under sedation or anesthesia. You may have thought “I’ll give twice the fluid maintenance rate to this patient”, but where did this value come from? How do we empirically create an appropriate fluid therapy plan for anesthetized patients? Today’s guest on the NAVAS podcast, Dr. Jane Quandt, will guide our listeners through this very question.
Dr. Quandt is a long-time veterinary educator at the University of Georgia College of Veterinary Medicine and boarded in both Anesthesia and Emergency Medicine. With her expertise and unique perspective, we will cover a wide range of topics regarding fluid therapy in anesthetized patients, including using pulse oximeters to determine fluid responsiveness, how to use fluids to appropriately treat anesthesia-induced hypotension, when and should you use a colloid, how to use hypertonic fluids, and fluid resuscitating patients with elevated sodium values.
So, water-ver you do, be prepared to get your ears wet with this in-flow-mative conversation all about fluid therapy!
For more information on this episode’s topic, we invite our listeners to check out the 2013 AAHA/AAFP Fluid Therapy Guidelines for Dogs and Cats, specifically the section on Fluids and Anesthesia
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. Several speakers will discuss blood pressure management under anesthesia, which will include fluid therapy. Registration starts Feb. 1.
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
Introduction and Podcast Support
00:00:06
Speaker
Hello to all you gas pastors out there. Welcome to another episode of the Navas Podcast, the official podcast of the North American Veterinary Anesthesia Society, sponsored by DECRA. Our mission is to help veterinary professionals and caregivers
00:00:23
Speaker
advance and improve the safe administration of anesthesia and analgesia to all animals. I am your host, Dr. Bonnie Gatson, and this month's episode is a bit of a riff on our previous episode from last month all about managing blood pressure in anositized patients with Dr. Radehi Pranjapay.
00:00:42
Speaker
If you have not listened to it, I would strongly encourage that you take a short break from this episode, go back to last month's episode and take a listen because it is just a great segue into what we are going to discuss in this episode. And also Dr. Paranjapai is just so smart and so insightful
00:01:01
Speaker
You are just guaranteed to soak up some amazing anesthesia knowledge, so please go back and take a listen if you haven't done so already. Before we get into the nitty gritty of this episode, I have just a few small housekeeping items.
00:01:18
Speaker
If you are enjoying the content from this episode or previous episodes, please consider supporting the podcast by leaving us a like or review on whatever medium you choose to use. Listen to podcasts.
00:01:34
Speaker
and just simply tell a friend to listen. If you have any questions and or a topic suggestion, please write to me and the producers of this podcast at educationatmynavas.org. So far, I've been asked to cover some of the newer pain medications that have been recently introduced
00:01:57
Speaker
to the market in the US, including Salencia for cats and Librella for dogs.
Upcoming Events and Reflections
00:02:02
Speaker
There is a Salencia episode in the works, so please stay tuned for that one. We will work tirelessly to get an amazingly smart guest for all you gas passers to speak to me about Librella. Again, thank you all so much for your listener feedback. It is invaluable.
00:02:21
Speaker
Next, we want to give our listeners a heads up that the NAVAS virtual spring symposium will be held on April 27th and 28th of 2024. There is program content for veterinary technicians, general practitioners, and specialty veterinarians. Please visit the NAVAS website to learn more about the program and the speaker lineup.
00:02:43
Speaker
So, about this month's episode. Oh boy. Today's episode features a recording I made a long time ago when I was first dreaming about making this podcast. I was given the very fortunate opportunity to speak with an incredibly knowledgeable and
00:03:01
Speaker
self admittedly seasoned veterinary anesthesiologist who was at the time and actually still is teaching veterinary students all about anesthesiology at the university of georgia walking into this interview i had nothing prepared and i also had no idea what we were going to discuss.
00:03:21
Speaker
somewhat because it was a bit of an impromptu arrangement and also because I was a little starstruck at having the opportunity to sit across from a brilliant mind in the field of veterinary anesthesiology. And admittedly, the lack of preparedness definitely shows in the episode, given our meandering conversation.
Fluid Management in Anesthetized Patients
00:03:42
Speaker
However,
00:03:43
Speaker
The more I picked at her brain, the more I realized that she was the exact expert I needed to speak to about using fluids appropriately for anesthetized patients. In this episode, we are going to discuss using pulse oximeters to determine patient fluid responsiveness.
00:04:01
Speaker
How to give a fluid bolus appropriately to treat anesthesia induced hypotension? When and even should you use a colloid? How do you fluid resuscitate patients with wacky sodium values and many more hot topics on fluid therapy?
00:04:18
Speaker
We even dabble a bit in transfusion medicine. I just want to quickly mention that due to my lack of preparedness during the interview, you will hear several interjections from me embedded into the episode just to help give some context to our discussion. And also because I was a young interviewer at the point where I was just trying to figure out how to even use a microphone, I say, yeah,
00:04:44
Speaker
and like every 30 seconds. So if that annoys you, just know it annoys me too. And I promise that I've learned from my early interviewing antics, so please bear with me.
Dr. Jane Quarn's Career Journey
00:04:58
Speaker
So without much further ado, I hope you enjoy this conversation with professor of anesthesiology at the University of Georgia College of Veterinary Medicine, double-boarded veterinary specialist in both emergency and critical care,
00:05:13
Speaker
and anesthesiology, author of countless manuscripts and book chapters, and General Sparty Pants, Dr. Jane Quarn.
00:05:27
Speaker
Can you give me a little bit about your background and how you came about becoming a veterinary anesthesiologist? I knew I was going to be a veterinarian when I was eight. That was never a question. And I went to vet school. And when I was in vet school, we didn't have what's called tracking or specializing. You had to do everything, which I liked. I liked doing all the animals.
00:05:46
Speaker
And my first anesthesia rotation was pretty terrifying, like for any student. And I thought, well, I'm going to do this in practice. I should take a second one to get good at it. And then I did a third one. So I actually did three anesthesia rotations my senior year. I thought I really liked it. But to make sure I wanted to change my whole focus, I did a year of practice and said, yeah, I got to go to anesthesia.
00:06:06
Speaker
Oh, great. And the idea was then I could do all species and that was appealing to me. Yeah. You know, it's fascinating for me, it was like my track was something really similar. So I think I knew I wanted to specialize when I was in veterinary school. Cause I couldn't see myself doing like GP. Yeah. I had been a technician for a long time. So I was like, this is not really like my jam. And it was like, I took anesthesia rotations. Like that's how I figured it out. Yeah.
00:06:32
Speaker
So I think it's just really fascinating. Your, your path was kind of like mine was like, we wouldn't, we didn't know you're going to do anesthesia. You just get exposed to it. I think even like when I was a student, I, I never like wrap my head around the fact that you could specialize in anesthesia.
00:06:47
Speaker
The time I went to school, especially, civilization is so much more prevalent now. And there's so many specialists in private practice. So when I was exposed to veterinary medicine, it was just the general practitioner. There wasn't specialists like there are now. It's changed so much. So a lot of these students already come in knowing that I want to go into surgery. I had only been exposed to a general practitioner. I was going to be a general practitioner. So I do feel that the climate has changed a lot in the years since I went to vet school.
00:07:16
Speaker
And when you went to vet school, was there like, you said there was no tracking cause you just did like all animals. Oh, everybody had to do every rotation in the hospital. Yeah. And it was interesting. Now I see the kids, they get different groups. We had the same five kids through the whole year and they had a however many blocks and you're group one and you just go through the whole year, do all these rotations and group two is behind, you know, it just, yeah. So if you didn't like your classmate, man, you were in trouble for the whole year and you just did everything.
00:07:46
Speaker
So when you graduated various school, were you expecting mostly to be like a mixed animal practitioner? Yeah. Oh, that's fascinating. Like I couldn't even imagine that being a thing now. Yeah, it doesn't. Even specialized between equine and like small animal. Yeah, but so we had to do every rotation. Yeah. I graduated from Iowa State University and pigs. I did know I didn't want to do pig medicine. I definitely did not want to. I mean, we spent time in pigs. Right. Right.
00:08:14
Speaker
But it was a good... I mean, I anesthetize pigs now, but I really enjoyed the exposure to everything because I didn't know what I wanted to do. So it was good to see everything. When you teach anesthesia to students, what are the big takeaways you want your students to learn when they are leading your rotation? What are some things that you've seen? We talked a little bit about the MRI and a little bit about the fact that you have caps on your MRI
00:08:39
Speaker
because you've seen all these complications. When you have students that are on your rotation, what's the big takeaway? What do you want them to take away from anesthesia? The big ones? I think the biggest thing I wanted to take away is anesthesia can be done safely. That to me is important. Most students when they come into anesthesia, this is their most feared rotation because this is the one rotation where they personally could kill an animal.
00:09:01
Speaker
Yeah. Yeah. I want them to come out of that comfortable with anesthesia. They could do it safely. And guess what? Animals actually can live through anesthesia. Yeah. Because most of them are just terrified of anesthesia. Not saying that animals can't die under anesthesia, but if we know how to do it safely, they actually can survive. And they're going to do anesthesia every day in most general practices, spades, neuters, lumps, dentistry, whatever.
Pre-Anesthetic Evaluation and Blood Work
00:09:26
Speaker
Not all of them are healthy patients. The other thing I think we have to really
00:09:30
Speaker
make the student aware of, you have to do a physical exam and look at the animal. I know, and we have kind of guilty of it is too. We have a little formula, right? Every dog gets the same thing. Yeah. Right. But not every dog can handle the same thing. Right. And so here I never sign off on an anesthesia request and tell it, Hey, someone actually looked at the animal. Yeah. We've gotten heart rumors that some poverty has missed. We've done, you know, blood work and guess what? They're anemic.
00:09:56
Speaker
Things that could impact anesthesia that if we didn't actually look at them, you wouldn't have known that yeah, or the dog is actually a lunatic Nice quiet dog or he's trying to take your face off. Yeah. Yeah, absolutely. Yeah. Oh, let's just do the standard thing Okay, this dog has a heart murmur. He's anemic and he's vicious. Well, the standard thing may not work for him. Oh
00:10:16
Speaker
Right. You know, I want to go back to a little bit about the blood work because I think that there's this really interesting study that some of my mentors used to like float in front of me sometimes, which is like, how important is it truly to get pre-acetic blood work on a healthy patient? There's a study where they collected some blood on or just like a full blood work, like full CBC chemistry panel.
00:10:38
Speaker
on healthy animals that were eating like spades, neuters, simple orthopedic procedures. And they found that in like less than, I think it was like 1% of cases or 3%, some very low number, that the results of the blood work actually changed the anesthetic plan or had the case actually cancel whatsoever. So the question being like, how important is it to get that full CBC chemistry?
00:11:03
Speaker
Well, I think that's where you do the physical exam. Yeah. Right. But for me, I do like just, we call it the big four, PCV, total protein, BUN glucose. Yeah. And that's really all I need for a healthy animal because I do kind of like to know what the PCV and total protein is because a lot of animals can look good, but they could have parasites.
00:11:22
Speaker
Yeah, they could have some underlying low grade renal disease, something that I would know. So for me, a healthy animal, PCV, tall saws and BUN and glucose, not that big a deal. Yeah, right there. Yeah. And also you don't know, I mean, even simple procedures like TPLOs or spay, like these, those are animals that can potentially bleed significantly. Well, we've all had the spay that we dropped the stump, right? Yeah. Yeah. Well, then we've got severe blood loss. So to me, blood work, the full CBC cam,
00:11:51
Speaker
Yes, if they're geriatric, they have a really difficult disease. But the normal healthy, I don't think it's that out of line to ask for just a big four, just to see what I have to start with. At this point during our conversation, Dr. Kwant and I were talking about anesthetizing animals for respiratory emergencies.
Pulse Oximetry in Veterinary Anesthesia
00:12:12
Speaker
And I wanted to know her opinion on the accuracy and effectiveness of the pulse oximeter at diagnosing low blood oxygen levels in emergent anesthetized patients. And I was surprised to find that this really opened up our conversation towards discussing fluid therapy for anesthetized patients.
00:12:34
Speaker
If this sounds like those two ideas should have nothing to do with each other, I hear you, but well, just listen for yourself. And with that, I think, you know, going back to the patient, I think another really good topic to talk about, at least since we're on respiratory now, would be like the pole socks.
00:12:51
Speaker
which I think is a piece of my argument that is like wholly frustrating for many people. Yeah. I mean, unfortunately, the pulse ox, if it works, it's great, but there's so many things that can lead it astray. So when I have a pulse ox, if the heart rate doesn't match, then I don't believe the pulse ox. Yeah. Yeah. Right. And the first thing we do if a pulse ox doesn't work is what? Move it to another spot. Yeah. Move it to a different spot. Yeah. Until it gives you an answer you like. Maybe it was telling us that maybe we should look, if you say, look at the dog, maybe Chewie has that little,
00:13:19
Speaker
So to me, the pulse ox, and also we can have times where the pulse sock is working really well and the dog is completely hypotensive. Oh yeah. So it doesn't really tell us what we think it's telling us about perfusion, but I, I wouldn't say it does. Yeah. Because I've had dogs that they're so hypotensive, I'm actually treating them. Pulse ox is amazing. It's great. Oh, it's doing good. So I take the pulse ox with a grain of salt.
00:13:43
Speaker
Yeah. Do you have a perfusion index on your pulse
Fluid Assessment and Perfusion Indexes
00:13:46
Speaker
ox at all? Yeah. Do you ever like use that to try to tell you whether or not you think the pulse ox is working well? We use it to tell us if we think we need fluids. Ah, interesting. You know, if there's a percent differ change in it. Yeah. So that kind of helps because the other question is, you know, the pulse ox is telling us about perfusion. Well, that's a good question. But if that index is low, maybe they do need a, you know, fluid bolus to help improve the output, which in theory would improve the pulse ox.
00:14:11
Speaker
Yeah. Just so for people who like to, we're all on the same page with our listeners. Can you describe a little bit about what the Perfusion Index is? So we have the dog on a ventilator. So we have a consistent breath. Yeah. And so then in theory, you have also consistent Perfusion to that lung. And then you hit the little
00:14:30
Speaker
button to do that and if the perfusion index is like a 12 or so percent different from what you think it would have been normally like it's gone down then you feel like oh there's a lack of volume right so we would need to give some fluids like in human medicine you can do like oh let's tip his legs up so we get a kind of an automatic transfusion yeah yeah and then
00:14:53
Speaker
Maybe that's going to get better. And obviously in dogs and cats under anesthesia, we can't do that. So if we see that, because the question always is, do you need a fluid bolus and how much do you need a fluid bolus? Yeah, that's a really good bolus weight. So if I have this pulse variation index that says, hey, this is not normal, you're different from the standard, then we can try a fluid bolus.
00:15:13
Speaker
So I just want to take a moment to clarify what the perfusion index and the pulse pressure variation are in case your head was spinning after that last question. Both of these measurements are displayed on the monitor of some but not all pulse oximeters. And you may have seen this displayed somewhere on your own multi-parametric monitor
00:15:37
Speaker
maybe you just never really paid attention to it. The perfusion index, which will be displayed as PI on a monitor, is the ratio of pulsing to non-pulsing blood at the site of the probe measurement. In other words, it is a good indicator of the patient's pulse strength or blood flow through the tissue where your probe is located. The pulse pressure variation quantifies changes in arterial pulse pressure
00:16:06
Speaker
during mechanical ventilation and can be a predictor of fluid responsiveness or how likely that patient's stroke volume will be improved by giving a fluid bolus. This measurement, however, requires placing a catheter into an artery, which can be invasive and requires some technical skill. So there is an index that can be measured by the pulse oximeter that can be used as a more non-invasive way to detect the pulse pressure variation.
00:16:36
Speaker
and that is called the Pleth Variability Index or PVI. It ranges from 0 to 100 percent and studies show that, generally speaking, if a patient has a PVI greater than 14 percent, then a hypovolemic critically ill patient will likely see an improvement in their preload with a generous fluid bolus.
00:16:58
Speaker
This is what we might classify that patient as a fluid responder. At this point, my conversation with Dr. Quant turned firmly towards discussing fluid therapy for anesthetized patients.
Anesthetic Maintenance and Fluid Reassessment
00:17:11
Speaker
So what is the anesthetic maintenance rate that Dr. Quant recommends for healthy dogs and cats undergoing general anesthesia? And when giving a fluid bolus to anesthetized patient, what rate does she typically start at?
00:17:26
Speaker
We typically use fluids at five mils per kilo per hour in dogs. The recommendation in cats is around three mils per kilo per hour, because we know we don't need as high as we used to. We used to do 10 and 20. So our fluid bolus is typically, we give that five mils per kilo that we would give to the dog over an hour, and we give it probably over 10 to 15 minutes, but we reassess. We reassess in five minutes, reassess in 10 minutes. It's better. Okay. Turn it back down. Cat, we probably do the three mil bolus.
00:17:55
Speaker
Now, again, if the cat has heart disease, maybe you can't have that kind of a bolus. So you have to reassess that. So then do you have to go to vasopressors or inetropes? The other question is how many fluid boluses do you give? That is a really good question. Do you give two? Do you give four?
00:18:11
Speaker
Do you get until they drown? What's your cutoff? Typically, we're using crystalloids. Do you seek giving a crystalloid? Are you believer in colloids? Are you anti-colloids? If that doesn't work, where do you go next? At this point, maybe you're asking yourself, what is a crystalloid?
Crystalloid vs. Colloid Fluids
00:18:28
Speaker
What is a colloid? What are those two ladies even talking about?
00:18:33
Speaker
Well, these are terms for different broad categories of fluids. These categories we put these fluids into depend on the molecular makeup of electrolytes and other molecules, which determines the osmolarity of the fluid and the amounts of large heavy molecules contained within the fluid. There are other things that we can use in categories, these types of fluids, but those two things are the main things.
00:19:01
Speaker
When we put fluids into a blood vessel, a lot of different things can happen. The fluid may stay for a long period of time within the vascular space or it may quickly leave the blood vessel and enter into the space surrounding the cells or what we call the interstitial space.
00:19:20
Speaker
Or it's even possible that fluid from the interstitial space or from cells may enter back into the blood vessel. So here comes our definitions. A crystalloid is an isotonic saline solution, which means that it has a similar osmolarity to plasma, and it typically contains a balanced array of electrolytes that matches pretty well to the electrolyte components of the extracellular or interstitial space.
00:19:48
Speaker
This causes the fluid to leave the vascular space quite rapidly and it quickly enters into the interstitial space. You're probably very familiar with these types of fluids because we commonly administer them to anesthetized patients.
00:20:02
Speaker
And these include fluids like lactate ringers or LRS, plasmalite, normal cell R, or 0.9% saline. Colloids, on the other hand, contain high molecular weight molecules suspended in crystalloid carrier solutions and
00:20:20
Speaker
They don't freely distribute across the blood vessels and enter into the extracellular space, so they tend to stay within the vascular compartment for a long period of time. Examples of colloids include head of starch, bed of starch, fresh frozen plasma, or canine albumin. So back to the question, how many crystalloid boluses does
00:20:47
Speaker
Dr. Quant typically minister to her hypotensive patients. We typically here do two crystalline boluses and I'm done after two. So why two?
00:20:58
Speaker
Because at that time, I feel like if I do two five mil per kilo boluses, then I've given that 10 mils per kilo. Right. And that's kind of like a, I don't know if it's an imagine number, but we feel like when you start in shock, you think you're going to start at a 10 to 20 mil per kilo bolus and you're going to obviously monitor that. You shouldn't have to do a full blood volume. Right. So I've given 10 mils per kilo. Well, it didn't work.
00:21:21
Speaker
So is there any point to giving more of a lot of them? Now, if they're bleeding out, that's another story. Right. This is just like a classic. I'm on the table. I'm hypotense. I'm a TPLO. Why am I doing this? I've turned down the inhalant, obviously. Yeah. Two fluid bolusolites, crystallites don't work. I think you got to go on to the next step.
00:21:38
Speaker
So are you a call a giver? We use colloids here, but we use a low dose and we don't do like these CRIs. Okay. You might get a two to four mil per kilo bolus of colloids after your crystalloids. Yeah. Because our theory is it still would help hold the fluid in the vascular space. Yeah. But they don't get a CRI of it. Yeah. This little bolus. Yeah. Okay.
00:22:00
Speaker
That didn't work. Well, now are we talking dopamine, dopamine, norepinephrine? Right. I'm going to circle back to colloids because I think it's an interesting topic because I've had mentors who have very strong opinions on colloids. It's a good way to start an argument. Do you even call it? Do you give a colloid? Yeah. I was talking to earlier, I talked to Rachel Reid about opioids and I was like, oh, this is a way to really get people's opinions out there, very strong opinions about this. I think colloids is like another hot button issue.
00:22:29
Speaker
Let's just dive into the collides because I think it's interesting. So why are people so passionate about give collides or don't give collides? What is the big me argument? I think the biggest thing is we know in human medicine, collides can impact renal function and they can also impact clotting profiles.
00:22:45
Speaker
I do think when anything first comes out, oh, this is it. This is the panacea, right? So maybe we did do too high, you know, 20 mils per kilo per day or whatever that was, these constant CRIs. That may not have been ideal, but at the same time,
00:23:02
Speaker
We don't have a lot of good research on what colloids do to dog kidneys or cat kidneys. There's research out there. I know some projects have been done. We haven't seen the publications yet. So it's really hard. We know we can't easily extrapolate between species, right? So it affects the kidney of the human. Well, how old was the human? Did they have underlying disease? Now, is that the same as a cat with chronic kidney disease? I don't know that.
00:23:28
Speaker
Yeah, that's fair. I don't. And I still don't know that in a dog either. Now, if you can give me a paper that says you cannot do it because it creates this, I'm all in. I'll do that. I've modified my approach in that, like I say, we just give boluses for me under anesthesia and I don't do these big CRIs.
00:23:45
Speaker
Yeah. Like we used to do in the past because I'm not sure. It is a large molecule. It could affect, it doesn't get lodged in the kidney as it stick around for months. Yeah. Maybe. The flip side of that is if you're really hypotense and dying, well, that might affect renal function too. So I've given you as much crystalloid as I can. Do I keep flooding you with crystalloids till now your chemo diluted? Oh, then your clotting factors get diluted. Right. Then you get edema.
00:24:10
Speaker
cats don't like it because then they get pulmonary edema. I can't take you to the renal lab like in human medicine and pull all the fluids back off. So how much crystalloid can I give you? I can make you squeezy and all squishy. I don't know if that's good. Yeah, that's fair.
00:24:27
Speaker
I limit the colloids. Do I worry about clotting factors? Yeah, I'm going to go get plasma. Before I ask this next question to Dr. Quant, I feel like we have to take a step back and discuss a concept called oncotic pressure. This is going to be a very cursory and rather
00:24:45
Speaker
basic explanation, but when blood is flowing through very, very small blood vessels known as capillaries, there are competing forces at play that determine how much fluid leaves the capillary and enters the interstitial space of a given tissue.
00:25:01
Speaker
These opposing forces are known as starling forces. These forces exist both in the capillary and in the interstitial space. Depending on the interplay of all of these forces, we will see fluid exiting the vascular space and into the interstitial space, generally speaking.
00:25:23
Speaker
It's really important that these fluids are balanced correctly. For example, if too much fluid leaks from the capillary into the interstitial space because these forces are not well balanced, your patient may develop swelling and edema.
00:25:39
Speaker
On a very basic level, these opposing starling forces are known as hydrostatic pressure and oncotic pressure. Hydrostatic pressure is a force generated by the pressure of fluid, while oncotic pressure is a force generated by proteins or other heavy molecules. There are both hydrostatic pressures and oncotic pressures in the capillary and in the interstitial space that are all competing against one another.
00:26:07
Speaker
If we are focusing only on the capillary, hydrostatic pressures are responsible
Fluid Therapy in Liver and IBD Cases
00:26:13
Speaker
for fluids leaving the capillary, while oncotic pressure is responsible for keeping fluid within the vascular compartment. Within the vasculature, large proteins such as albumin are responsible for maintaining oncotic pressure,
00:26:27
Speaker
So conditions where albumin is lost can contribute to lowering the oncotic pressure within blood vessels. There are other factors determining how much fluid is lost across the capillary beyond starling forces, such as how permeable the capillary is or if the capillary lining has been damaged in some way. But for the purpose of this question, just remember that an appropriate oncotic pressure within the capillary is necessary to prevent the loss of too many fluids from the vasculature.
00:26:57
Speaker
Oh, and also another term for oncotic pressure is COP. I wanted to ask a little bit about that too. I'm not necessarily about patients with clotting disorders, but more about patients with liver insufficiency or patients who are hypoprotonemic for some other reason. How do you approach fluid therapy with those patients? Because
00:27:19
Speaker
I find that, you know, you have a patient with liver insufficiency or some hypopronemic patient and there's a desire to provide some kind of oncotic support. And a lot of times I go for colloids in those cases, or I might provide kind of a mixture of like colloids and crystalloids. How are you approaching those patients? So those are the ones that we commonly see that they're getting scoped, right? Because they've got IBD. Yeah. Right. They've got to be anesthetized for a while.
00:27:41
Speaker
Yeah, I'm going to scope and take multiple little bits and pieces and it's usually the 12 year old Yorkie that's already somewhat, you know, decrepit. Yeah. So we use half and half. I use half crystalloids. I cut the rate down now instead of five, it's getting two and a half, three mils per kilo per hour. And then I'll give some colloids.
00:27:59
Speaker
Yeah. Do you give it as a CRI or do you give it as? For those patients, we give it as a CRI just for the duration of the procedure. Okay. And do you give it as like the happiness at a great, or do you give it a different rate? So normally I would do like two mils per kilo per hour of the colloid, two and a half mils per kilo per hour of the crystalloid. Oh, that's good. So in total, they're getting five mils per kilo, but it's not the same. Yeah. Because we know if we give colloids and crystalloids at the same rate, we're going to give volume overload.
00:28:26
Speaker
Ah, okay. So I cut the crystalloids down. Now, if I wanted to do a fluid bolus, I do the fluid bolus with the crystalloid, not the colloid. Ah, okay. I feel so much justified because that's totally how I do it. Yeah. And to hear it from you, I feel like, yes. What we do know that if we give colloids long-term, then the body says, I don't need to make albumin because you're keeping my COP where it's at.
00:28:47
Speaker
Yeah. So I'm just doing it for the anesthetic thing. Because there's that whole thing about hypotension under anesthesia, that's not a good thing. So I'm using it transiently, just so they can get through the procedure. Yeah. And then when they recover, they go off the colitis and then I leave it to medicine to determine what kind of support they need once they leave my area.
00:29:07
Speaker
I'm also curious about the difference between the ability to provide oncotic support with things like colloids versus plasma. What's the big difference between there? As far as like potency or dose? What do you mean? Well, I think the artificial colloids are more potent as far as their COP. But if I have a little teeny animal and I'm worried about
00:29:28
Speaker
other factors, potentially clotting factors, depending on how bad the liver is. We know we can't give enough plasma to a big animal to affect their COP to the same extent we could with a colon. But if you're a teeny weeny, yeah, you could probably benefit from plasma and it'll affect your COP. Mastiff's different than a teacup chihuahua.
00:29:47
Speaker
Right. So what's different about this? So I feel like I can't get enough volume in the mastiff with plasma to affect the COP, but I can with the chihuahua. Yeah. Just because their, their blood volume is so much smaller. Now, if you had a septic abdomen and things are going bad, yeah, I'm probably going to reach for plasma because I'm also worried about coagulation abnormalities just related to the sepsis.
00:30:09
Speaker
That doesn't mean anyone gets some head starch while I'm getting the plasma. Right. Right. That to me, those dogs are probably going to need plasma sooner rather than later. Yeah. Where an IBD, they shouldn't have a clotting abnormality per se. They could just get by with a colloid.
00:30:26
Speaker
What about canine albumin? Have you used that at all? Or have you any opinions on it? I have seen it. We haven't used it very much. Obviously it's safer than human albumin in dogs. So I do think it's an alternative. Again, we have the ability here, you know, we can get plasma. Yeah. And whole blood. Yeah. But I think if you were in a practice where you didn't have access to that, I think that the canine albumin is an alternative. I just haven't used a lot of it.
00:30:55
Speaker
I think it probably is expensive if I had to guess. So for me, again, I'm at a university. I just go down and say, I want a unit of plasma thawed out and it happens. I know. I get it.
00:31:06
Speaker
It's nice. It is nice. But yeah, I can imagine where maybe some practices can't choose, you know, plasma versus colloids. You've got to just go with your colloids, right? Yeah. Cause they can stay on the shelf. Yeah, exactly. And the same way with the life of lies, canine albumin that can sit in the shelf till you need it. Yeah, exactly. So there is that advantage I think to those products. Yeah. So I want to ask you about a fluid that's like near and dear to my heart, hypertonic saline.
Hypertonic Saline and Resuscitation Strategies
00:31:33
Speaker
I like hypertonic saline. I certainly use it in hemorrhagic shock patients. I will say I have used it in dogs that we've given fluids and that's not responding. And they are probably a splenic mass. They're not bleeding out, but they've had blood loss.
00:31:50
Speaker
Yeah. Let's go ahead and give him some hypertonic saline. I use four mils per kilo one time. We certainly use it in our colic horses. There's no way you can get enough liters in a horse before he goes to the table. One or two liters of hypertonic keeps him alive while you get to the table and start your other fluids. And we use them obviously in brain trauma patients. You can use that potentially instead of mannitol.
00:32:14
Speaker
Yeah. And it's cheap. Oh, it's so cheap. It comes with these giant bottles. Yeah. Those giant bottles, one giant bottle per horse. But yeah, we use it. I like it. Yeah. So can you talk a little bit about how it works? Well, I think it's so hyperosmotic. The sodium is so high that it pulls fluid into the vascular space. The problem is, I think you have to realize with hypertonic is it increases urination.
00:32:38
Speaker
and it somewhat dehydrates your patient because it pulls fluid from the other tissues, the cells. We give hypertonic, but we are immediately giving a crystalloid as a chaser because you've got to fill a pump back up once they urinate. It buys you a golden hour, essentially. We think hypertonics knew it was used in the Vietnam War. That's where it first came into play. For hemorrhagic shock, it gives you an hour to get to the mass unit wherever you're going.
00:33:06
Speaker
So we give hypertonic, but you got to follow it with regular crystalline fluids.
00:33:10
Speaker
Yeah, I think it's a really important point. Is there any patients that you think hypertonic is like conjured decated? Well, one could argue that, again, this is if you are already hypertonic, do you need more salt? Yeah. It depends on why you're hypertonic. If you are hypertonic because you had your, here's the poor dog that the housekeeper forgot to give him water and he's hypertonic because he's lost free water. Yeah. And you're going to resuscitate that dog. You have to resuscitate him with hypertonic.
00:33:40
Speaker
Yeah, that's really interesting. He resuscitated with the same osmoality that he is, otherwise you will create his little brain. Yeah. Right. So that dog actually needs hypertonic. Now the heat stroke dog that is hypertonic because he's lost free water, that's an acute loss. He just needs LRS or plasma light. Right. He does not need hypertonic saline.
00:33:59
Speaker
Yeah. That's a good point about the chronicity as well. Like if you have a patient that's like chronically hyper-neutrismic or hyponetrismic, you have to be a lot more careful about flu-resustaining those guys. You can't change it too quickly because their cells can't tolerate that. Yeah. So like the heat stroke dog's acute. Yes. Just give him fluids, even though he's got a high salt. Yeah. He can do that. The chronic one can't do it. So there are times that actually hypertonic fluid is the fluid of choice.
00:34:26
Speaker
Yeah. What do we count as chronic? And I'm going to ask this. I had a case, I think like last week where I had this little dog come in and had a septic abdomen, also Addisonian, of course. That's a gem. That's a gem, right? So the dog was
00:34:42
Speaker
pretty profoundly hyponatremic. Then the question was, what fluid should we give? The question also being, what does chronic mean? This dog probably had borderline adhesins, but then also has this stress response. Now things have gone very badly for this dog very quickly. What does chronic mean?
00:35:04
Speaker
I think it depends on who you talk to, obviously, but to me, it depends. Chronic is how long does it take the body to try to resolve or set a new, okay, this is going to be my new level. Yeah. So I think for me, chronic is somewhere around two to three days.
00:35:19
Speaker
Okay. Then maybe that's short for some people, but the body is going to try to do something in that amount of time. So to me, 24 hours or less is probably acute. Okay. But anything starting to go past that, I feel, okay, this is probably more chronic than the dog didn't get water for one day. I can probably still give him fluids and he'll be fine. Three days, he's probably not going to be fine.
00:35:41
Speaker
Yeah. I will say this personally, I very rarely have given hypotonic fluids to dogs, like half-strain saline or anything like that under anesthesia, mostly because I feel like for anesthetic purposes, you know, might like actually like decrease my plasma volume in some way. Have you ever used those clinically in patients? Under anesthesia? Yeah. It's tough. So to me, there's kind of like, when you're talking those kinds of fluids, you're usually basing it on electrolytes.
00:36:10
Speaker
Yeah, right. They're either it's a sodium, right, or follows that. Yeah. So I sort of think there's two compartments. There's the sodium and then there's the water. I know it's just a little off the question. So if I have a question, hypertonic
Fluid Selection Based on Electrolyte Imbalance
00:36:25
Speaker
patient. Yeah. I'm going to resuscitate him with hypertonic fluid. Yeah. I'm also going to give him D5W, which is free water to change his sodium. Yeah. And let's say he's 190 and I want him at 140. Yeah. That's going to take 50 hours.
00:36:39
Speaker
Mm-hmm cuz I'm gonna change the sodium one milli equivalent per hour. Yeah, maybe even a half milli equivalent Yeah, I always thought it was a half but it depends. Yeah, probably a half to one. So let's just say 50 to 80 hours sure to change that so I set that rate and I'm watching the sodium over here Yeah, I'm still do I resuscitating with hypertonic as the sodium goes down with my d5w I'm changing this fluid over here
00:37:03
Speaker
Yeah, that's really fascinating. So I gave the resuscitation volume with the hypertonic here. Now I'm changing the sodium. Okay. I'm going to check that sodium in six hours, 12 hours. Okay. It's slowly coming down. Okay. Now I'm changing my hypertonic. Now it's getting more to match him.
00:37:20
Speaker
So over the next 50 to 80 hours, as this goes down, this fluid is also going to change. So at the end of it, I'm probably in on LRS. Yeah. So you're assessing with hypertonic and then you're treating the hypernatremium with D5W. And so there's two fluids going. Yeah, there's two fluids going. That's really cool. Because I don't think you can change, because you have to change it gradually, the sodium.
00:37:44
Speaker
Yeah. But you have to resuscitate him first. Yeah. Yeah. Right. Because there is no volume to work with. And then you change that volume as the sodium changes. Yeah. That's cool, actually. And that is going to take some time. So yeah, say he had to go to surgery. What am I going to do? I'm going to resuscitate him with the hypertonic. Yeah. And maybe I have my D5W going really slow at the same time. But he's going to stay on that as we transition. So the hypotonic, I would probably do it the same way.
00:38:10
Speaker
Yeah. I get my other question based off of sodium as well has to do with like Mac of inhalants. Yeah. Have you ever seen that like a change in inhalant max with changes in sodium? I know it's reported, but I don't know if you ever seen it clinically. Yeah. Cause usually I think probably I don't see that extremes.
00:38:28
Speaker
Yeah. I also have not seen it, but it's, you'll see it written in some articles that like extreme hypernatremia actually decreases Mac of inhalants. I could see why. Cause there's semi-comatose, some of those guys when they come in. So if I had this dog, I just talked about, no, let's guess what? He has a GDP at the same time. Yeah. I bet his Mac would be different.
00:38:46
Speaker
Yeah, I bet so. But probably for like a bunch of other reasons too. Yeah. But there has to be a reason they got to that stage. Yeah. Right? And so like they're already somewhat neurologically impaired because they didn't get free water, they were sick, whatever. So I do think it would affect Max. I think the sodium would be just part of it. I mean, it's hard for me to imagine that I had a hypertonic crisis without a disease that went with it. That's probably fair. And if the animal didn't get water, well, then the disease is lost in free water.
00:39:14
Speaker
Right. Right. Right. True. And his brain isn't perfused normally. Yeah. So what's your crystalloid of choice? We use LRS. You use LRS? So again, I don't crystallize a crystalloid in some sense. Yeah. Should you use plasmalite or LRS? Plasmalite, I have seen it because acetate is supposed to be better, right? Yeah. But under anesthesia, big boluses of plasmalite, the acetate can actually cause a little hypotension.
00:39:42
Speaker
Yeah, I've seen that as well before. For me, that's why I use LRS. I think the fear of using LRS, especially in like emergent patients, is like, if you have a patient that is hypoperfused for some reason, has elevated lactate, how much is that like the lactate that's in lactated ringers can actually contribute to prolonged hyperlactate? I think it's very little, honestly. Because if I can start perfusing the liver, I think it's going to function and do its thing.
00:40:09
Speaker
If I make it more hypotense by giving a flute, I haven't done any favors there either. But honestly, if I had a choice, I take LRS. If all I had was plasma light, I use the plasma light. Yeah. But I honestly don't think the lactate in LRS is that high to make that big a difference. Now liver failure. Yeah. I was going to ask you about that next.
00:40:27
Speaker
Liver failure, yeah, then I probably would go for the plasma. How like fulminating of liver? There's a difference between liver insufficiency and liver failure, right? Yeah, I've used LRS with liver insufficiency. To me, failure is like they're yellow, their enzymes are all over the place and it's like, oh, this is like a disaster. So yeah, I'll go get plasma light for those guys. That's fair. I think my last question I want to ask
Blood Transfusions and Anemia Management
00:40:49
Speaker
about, this is just something I saw once and I wanted to get your opinion. Okay.
00:40:54
Speaker
So like cats in particular, yellow cats. There was somebody that I used to work with a long time ago that anytime you were sending a cat to the OR for cholecystectomy, they were like immediately also getting whole blood, like immediately or some kind of blood transfusion. And I didn't know if you had any like thoughts. I mean, I guess the thought process is like, these are patients that are usually have chronic disease. So they're usually anemic already anyway.
00:41:21
Speaker
and you know we're dealing with issues with clotting factors so you must just give them whole blood like just right off the bat just do it and i don't know if you've ever heard of that or thought had any thoughts about that i have not heard of just automatically doing it so again this this one i would want blood work on yeah so if they were truly anemic and i thought the procedure is going to be of some duration
00:41:40
Speaker
Yeah, I probably would give him blood. But I would base it on blood work. Right. As opposed to just giving it any yellow cap, getting a cholecystectomy blood. Well, maybe they're right. Maybe they are all anemic, but I would base it on the blood work. So if they're anemic and we're worried about clotting factors, yeah, that whole blood. If they're anemic, do we just start with PAC cells and then give plasma later? Yeah.
00:42:07
Speaker
You know, some of it, it depends on how easy it is to get whole blood. Okay. That's fair. It's like for some of us have cats available, we can go bleed and get whole blood and we also have components. So yeah, it'd be okay. Let's start with a component. Yeah. If I were in private practice and I just grabbed a cat and bled it, you know, fresh. Yeah, that's great. Yeah. Fresh whole blood is the elixir of life, but it's not always easy to get.
00:42:29
Speaker
It's true. I actually find that a lot of general practitioners, sometimes they actually have an easier access of getting whole blood. So you could just like pull a cat and bleed it, you know, and then immediately transfuse it as opposed to ordering red sauce. Yes, of course. You know, that would be the one thing. Cause when I was in practice, we had a cat, that was his job to be the blood donor. He's an A cat.
00:42:49
Speaker
Yes. Yeah, you're right. He lived there for free because he was a blood donor. Right. Yeah, that's cool. I want to talk about transfusions for a little bit. Yeah. Because I think the big question mark that I get from a lot of people is like, how do I know that my patient needs a transfusion? So to me, that's what's your transfusion trigger? At what PCV would you a transfusion? To me, chronic versus acute, also the procedure. Yes. Right. So I have the 19-year-old cat
00:43:15
Speaker
They're semi-mummified, right? They're all kind of tied up. Yeah. And he's getting a feeding tube. Yeah. His PCV is 15. Is he going to get a blood transfusion? No. Because it's a feeding tube. It should take him about 20 minutes, right? And there's going to be minimal blood loss because it's a esophagostomy tube, right? If they do it right. If they do it right. If they do it right. We're going for that. And he's used to it. Yeah. So no, he's not going to get one. Okay. Right.
00:43:41
Speaker
Five-year-old cat, hit by a car, femur fracture, bleeding, PCP is 15. Oh yeah, he needs blood. It's an acute loss. He's going to surgery. He's in shock. He's in stress. Yeah, he gets blood. Yeah. So different scenario. My transfusion trigger typically is if they're 25% or less. Oh, interesting. We're going to have a conversation with the surgeon. Like 25 going in, right? Because we know under anesthesia, we're probably going to go 3% to 5% low in that.
00:44:11
Speaker
And so I'm talking to the surgeon, oh, I'm never going to lose any blood. Well, actually you are going to lose some blood. So yeah, we have that conversation. So that's how I want that pre-op blood work. Have I ever taken interrupt blood work and say we need a PCV total sods to see if we need blood now? Sure. Yeah. Or I just look, I don't even need a PCV. Okay. You hit something big with a name and it's bleeding all over. Yes. He was slightly anemic before we started. Now we're going to go get blood.
00:44:37
Speaker
Yeah. Do you find you have different transfusion triggers for cats and dogs? I'll go a little bit lower with cats. I think they tolerate it better than dogs. Why do you think that is? I don't know why I think that is. This is like your clinical acumen. Yeah. They're just different species. Yeah. I don't know. They're lean squeeze better. I don't know. They just seem like they can tolerate anemia better.
00:44:59
Speaker
My other question too is that I always have this argument with the surgeons, which is like, let's say we hit a bleeder, right? Like some major organs like spewing out. Let's say the dog was or was not, or the animal was or was not anemic beforehand. And they're like struggling to get the bleeder under control. They finally get it under control. And their first reaction is like, what's the animal's PCV? Measure it right now. How much value do you think that has? Well, I mean, it depends on how...
00:45:23
Speaker
sometimes I think because of fluid distribution, it may not be a lot of value. But if it was normal, and now it's 10, well, yeah, that really because I probably hemodeluted them. Yes, exactly. So that then that question is if it's truly super low, I probably will give blood that if it's okay, it went from, let's say they were 45 to start with. Yeah. Okay, now it's 27.
00:45:45
Speaker
Yeah. I'll wait and we're going to wait for a couple hours. We're going to get into recovery and we're going to take it again. And usually by then it's come up a little bit. Maybe now it's 32. Great. We don't need blood.
00:45:56
Speaker
If after a couple hours it's actually 25 or less, okay, now we do need blood. So sometimes we give blood because they're not recovering well. Yes. Right? So yeah, they'll say, do we need to give blood? Maybe I'll wait a little bit. It came down. I know, but you're going to have fluid redistribution. They're going to squeeze their spleen. Let's look at it in two hours because they're not going to die from 42 to 27.
00:46:18
Speaker
Yeah. If there's like a healthy animal. Yeah. Okay. But if it went from 42 to 10, yeah, you're going to get blood. Yeah. Yeah. I think it's fair. I think it's an argument I have with our surgeons too is like, Oh, well it dropped from 40 to 25 blood. And you're like, well, you know, like.
00:46:33
Speaker
We can wait a bit. We can wait a little bit. I mean, also healthy going in. Yeah. And of course also look at your patients under anesthesia too. Like is your patient getting hypotensive? Are they getting tachycardic? Is there lactate going up? You know, things like that. So I try to encourage them to look at other things. I mean, our surgeons, cause blood's expensive. It's like, do you think we need blood? Can we try going without blood? Yeah. So I feel like it's the opposite for us.
00:46:54
Speaker
I'll wait till we get into recovery. Yeah, that's a good point. That doesn't mean I can't get blood later. We can always get blood for recovery. Yeah, of course. Yeah. Well, thanks for talking to me. You are welcome.
00:47:13
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.
00:47:37
Speaker
visit www.mynavass.org to advance your anesthesia journey today.
00:47:45
Speaker
As a reminder, we ask that you save the date for the NAVAS virtual spring symposium taking place on April 27th and 28th of 2024. More information, including the speaker lineup and topics that will be presented are available now on the NAVAS website. If you liked the discussion from this episode, there will be an entire day dedicated to managing anesthesia induced hypotension.
00:48:12
Speaker
and one of the featured speakers presenting on fluid responsiveness will be our previous guest, Dr. Vadehi Peranjapai. To learn more about the Navas Virtual Spring Symposium, visit www.mynavas.org forward slash 2024 dash spring dash symposium.
00:48:36
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.
00:48:54
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. 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
00:49:21
Speaker
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 Sal Hymanes. I want to thank our guest, Dr. Jane Quant, for this insightful discussion on providing appropriate fluid therapy for both healthy and unstable critical anesthetized patients.
00:49:45
Speaker
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. Until next time, I'm your host, Dr. Bonnie Gatson, and thank you for listening. I hope you consider tuning in next month for another episode of the Navas Podcast.