Baa's and Bleat's - The AASRP Podcast
Baa's and Bleat's - The AASRP Podcast
Blood Glucose Monitoring With Dr. Munashe Chigerwe
Join us for a discussion about continuous blood glucose monitoring and its use in evaluating pregnancy toxemia with Dr. Munashe Chigerwe. Dr. Chigerwe is a Professor of Medicine and Epidemiology at the University of California at Davis's College of Veterinary Medicine.
In this episode, Dr. Chigerwe discusses the efficacy of using continuous blood glucose monitoring for detecting changes associated with pregnancy toxemia in goats. The paper covered in this months episode can be found at the following link: https://avmajournals.avma.org/view/journals/ajvr/85/9/ajvr.24.03.0076.xml
If your company or organization would like to sponsor an episode or if you have questions about today's show, email Office@AASRP.org
Hello, and welcome to the next episode of Baas and Bleats, the podcast hosted by the American Association of Small Ruminant Practitioners. I'm your host today, Dr. Sarah Lowry, coming from you in very, very snowy Buffalo this morning. Today we have all the way from California Dr. And I'm going to try really hard to say your name correctly, Dr. Lunash Chigerway. Am I close?
unknown:Yes.
Sarah:Okay, he's giving me a thumbs up. All right. Like I said, Dr. Chigerway is um from UC Davis out in California. Um he's currently a professor of livestock medicine and surgery. Uh he does research that focuses on dairy cows, but he also says he likes to do research with his students on small ruminants because they're the best. Oh no, that's not what he said. He said because they're easy to work with. Um Welcome, welcome. Thank you so much for being here.
Munashe:Thank you for having me.
Sarah:Great. All right. So today, um, if you could start us off with just a little bit of background about where you came from, where you went to school, um, some of the research you've done in the past, just a little bit of an intro so we can get to know you a little bit.
Munashe:Thank you, Dr. Lowry. Uh, my name is Monasha Shigeru, as you mentioned. Um I graduated from uh vet school in 2001, and I grew up in Africa. I was born in Zimbabwe, and I went to vet school over in Zimbabwe, and I graduated from vet school in 2001. Um I worked there for about two years in mixed animal practice, which was approximately 60% um large animal and 40% small animal. Um, I moved to the United States in 2003 as an intern in food animal medicine and surgery at the University of Missouri. Um, and then I stayed uh at the University of Missouri for another four years, completing my residency in food animal medicine and surgery as well as a PhD in immunology. And my focus uh on research was mostly on um the development of the immunity in calves. Um and I was in Missouri up to 2008, for which I moved to the University of California, Davis, uh, where I became a professor since 2008. So I've been um at Davis for just over um 16 years now. I'm still doing research in uh involving uh dairy calves, but I also really enjoy doing research on small units, particularly when I'm working with students or some of our residents that work in the uh in our teaching hospital. So it's really great to be here and um I'm really appreciative of the uh association letting me um uh participate in this podcast.
Sarah:Great, yeah, thank you so much. So today we're gonna be talking about your 2024 paper that was published in the American Journal of Veterinary Research. And the title of that paper is The Evaluation of a Continuous Glucose Monitoring System in Healthy Dairy Calves and Adult Goats. Um, so I just before we jump in, I just kind of wanted many of us know what these monitors are. If you don't do mixed animal practice, because we do use them in cats pretty often, you've seen them on people, on the back of people's arms, um, people who are diabetic, these are the little white um circle monitors that you see, um maybe you've used that um constantly is monitoring for diabetics, and they do work fabulously on cats. Um, cats can wear them, they hate getting poked for uh glucose monitoring. So there's there's been a bunch of research already on cats, but bringing them into our large animal species, we do not have enough, like side, you know, call them cow side testing, stuff like that. So this is a really um exciting addition. Um so what was your catalyst? Like, kind of how did you how did you think about looking at this?
Munashe:Yeah, so um that that is very interesting because I think one of the uh motivations for us to test these devices in uh in calves and and goats was that you know, you know, just like you know any other species, we tend to have some very tiny patients, especially kids and lambs. So um, and most of the current tests that we have were basically you need a blood sample to do that. So you can imagine if we trying to check the glucose level six, seven times a day, it also means that you're gonna have to pull blood six to seven times a day. And obviously, for smaller patients, that's quite a bit of blood, you know, for uh in a single day. So we wanted to find a device that would sort of bypass the need to collect blood each single time. And um also the other thing was that um some of the patients, I mean, they really get stressed out from being handled so many times to get a blood sample. Um, so we wanted to find a device that would sort of um try and minimize handling, but at the same time um allowing us to monitor the blood glucose. And we're also looking at very specific diseases that we're interested in in the future on where we can monitor the glucose, particularly in young calves or kids or lambs that have diarrhea and they're losing so much glucose, or in our uh expecting doors and youth, sometimes they do have pregnant toxemia. So we really want to monitor our glucose either in the clinic or even at home. So that was kind of like our motivation to try and test these devices in goats as well.
Sarah:Yeah, when I first read this paper, I was super excited. You know, I have all like I was telling you before we started, I I have most of my clients are pets. Um, and so I have those 10-year-old boar goat does that always get pregnancy toxemia. So the thought of, you know, being able to just put a monitor on them and the owner, you know, watch them and see when they might need some boost, because as we know, with pregnancy taxemia and any of this stuff, prevention is so much better than treatment. Um, so as soon as those levels start getting off, I can just, I can see this being very applicable. And I want everyone to know, before we started, I looked this up from my supplier at MWI, whatever supplier you use, and they actually carry them. So it's very easy to order them. They had them for like $90. So, I mean, if this is a beloved Shogun or even a pet, like I don't think it's like financially unreasonable. And we can get into that. You definitely talked about that, about the financial aspect of this. But um, so why don't we just jump into the paper? And actually, maybe that's where we want to start. But um uh yeah, so go ahead. Where where do you kind of, I mean, I guess we can just jump into kind of the price point of this and how um, you know, maybe not for every dairy calf on a 5,000 cow dairy, but I think there's lots of applicable app places that this can be used.
Munashe:So yeah, so I mean there's a few places or a few patients that we can use this, and you probably alluded to some of them already. So when you have um, you know, animals that are either in the hospital or when you want the client to continue monitoring the glucose at home, and one of the advantages of these devices is that they can stay onto the on the skin for up to 14 days. So, really that's that's an advantage that um the client can do that at home. I think the other aspect, you know, although you know the device itself initially, when you purchase it, you know, as you mentioned, you know, just over $90, uh, within a day you can check the glucose as many times as you want over the next 14 days. And so we thought on average, actually, you'd only be spending $6 or less just to monitor the glucose. So that's really reasonable. Um, I think the other thing that we also um uh looked into using these devices was that um, you know, the you know, the clients can actually place this on as well, you know, if they're trained to do it. So it's it's something that they can do at home as well. So there were some advantages of you know using these devices. Um the other thing that we also found out is that you know, if a client has just one um god at home that they need to check the glucose, rather than uh buying you know one of the readers, they can actually just download the app and so they can just use their phone to monitor the glucose without having to buy you know an extra um device to um um or a reader to to check the glucose using these devices. So you can only you can only pair one patient and um with your phone, so which is which is as well.
Sarah:Okay. I've had many small animal clients that can easily apply it to their spicy cats. So I feel like if owners can put it on spicy cats, I think they can definitely put it on their goats and their especially their goat kids and stuff like that, also for sure. So I'm excited to get to the results, but one step at a time, so we know if this is something we can actually use in these species. So what what was your hypothesis to start?
Munashe:Our hypothesis was just, you know, we wanted to see, you know, our hypothesis was that, you know, can these devices be as good as, you know, the regular uh testing method that we use for testing the amount of glucose in patients. So we kind of uh went ahead and tested the device against, you know, sort of like the main or the reference method for testing glucose. So we had one, we're using just a regular big machine that we find in the lab to test for glucose. And we're also using an intensive care unit machine, you know, that will allow us to get a result within 15 minutes. And then the third method that we're using or comparing with the devices were just the regular glucose strips that you have to uh get a tiny drop of blood samples and measure that. And I think I'll just talk about a little bit about what's the advantages of each of those compared to what we're trying to test, which is the device. So the two main machines, the intensive care unit machine or the machine in the lab, they tend to be costly. So I'll give you, for instance, testing glucose using the bigger machine costs somewhere between 45 and $60 for each test. Testing using the intensive care unit costs about $47 for each test. Although the little glucose strips, you know, are cheaper, one of their biggest drawbacks is that they were designed for humans and their readings are based on the amount of blood the animal has. Now, because they were they were meant for humans, humans tend to have more cells in their blood that give the blood its red color compared to goats or sheep. So they tend to give errors when it comes to reading the glucose. So we also felt that, you know, even though we charge $5, it's $5 per test, which means if you do five tests in a day, you're charging the client $30 for those tests. So in addition to them not being very accurate, they are also more costly than the device that we were testing in this case. So we found that the device, you know, if it's placed on the ANMO, the initial $90 and having as many tests as you need to in a day, over 14 days was cost effective compared to the other methods. So that's kind of like we set out to compare this device alongside the other method that we've used in the past and sort of like try and make recommendations based on that.
Sarah:Awesome. Yeah. So you guys had a lot of data, a lot of information that was collected. So we're gonna focus on the goats, but you you had calves also and goats. So tell us a little bit about the materials and methods, about what animals you use, how they were kept, all of that.
unknown:Yeah.
Munashe:The way we designed the the study was that we were we were getting a single blood sample and testing that blood sample uh for the amount of glucose across all the four methods. So for the goats, we we apply the devices, and it takes about an hour for the device to get ready. So at each time point, we'd get a blood sample and then test it with the bigger machine in the lab, the intensive care unit machine, the glucose strips, as well as getting a reading from the device as well. And then the goats were pretty much in their normal environment, they were like in a pen, and then we'll put the device and put a bandage over the device. And actually, the device can read the amount of glucose over the over the bandaging material because we knew that probably goats were gonna try and remove uh some of those devices either themselves or they'll try and remove the device on the other goats. So we had eight GOATs and um they were staying uh in two pens, four in each pen, and they were given the regular food and everything. However, one of the things that we wanted to see is was that was the device able to detect the changes in the glucose when we do something to the animal. So one of the things that we did was to try and force the animals to have a lower amount of glucose, which we call hypoglycemia. And one way to do that was to give them insulin, and insulin is a hormone that's gonna drive the glucose levels very low. So we wanted to see if the device can pick up those changes. We also wanted to see how the device works when we increase the amount of glucose in the blood, and one way to do that in GOAT is to give them a sedative, which is xylosine, and then that will actually raise their glucose levels to above normal levels. So we wanted to see whether the device will also be able to pick up those changes. So we kind of like had three changes that we're making. One was to increase the amount of glucose, the second was to reduce the amount of glucose in the blood, and then the third was just to see how the device works when we don't make any changes. In other words, the sort of the changes in the glucose throughout the day we wanted to see if it's also able to pick up those compared to the to the regular machine. So within 24 hours, with a lot of time points that we're collecting glucose and then measuring the amount of glucose across all the four devices that we used.
Sarah:So just to clarify, the machine doesn't look at blood. It at the monitor that we're placing on them, it actually looks at uh interstitial fluid. Was that any concern? I mean, I'm sure there's been studies done on this in humans and the difference between blood and the interstitial fluid.
unknown:Yeah, absolutely.
Munashe:The body itself is a tiny needle that goes under the skin, and so it is measuring the interstitial glucose or sort of like the amount of glucose within the fat. However, we know that the amount of glucose that is within that interstitial fluid or the tissue under the skin sort of has an equilibrium with the blood. In other words, when there's glucose in the blood, the glucose will move from the blood and go into that interstitial fluid. And it takes, you know, a couple minutes, depending on the species, for that to sort of happen. And that was the point that, you know, despite the device not measuring exactly what's in the blood, does the amount of glucose under the skin on the interstitial fluid sort of like correlate to what's in the blood? And that's kind of like the advantage of the device in the sense that you know you don't need to get to the blood to measure the glucose. So you're absolutely right. The um the device measures the interstitial fluid glucose, or which is the tissue under the skin, compared to to the glucose in the blood. So you would would think that you know, if a device is really good, it should be able to really pick up the amount of glucose under the skin or in the interstitial fluid that is also related to the glucose in the blood. So they should be close enough, you know, in a in a healthy or in an unhealthy animal.
Sarah:Because really the main thing that's important is the change, right? Like, I mean, we're more with most of these tests, we're more concerned about the glucose change than like, I mean, obviously we want to know the actual level, but if you're if you're looking to keep these animals healthy, it's the ups and downs that are the most important.
Munashe:Yeah, absolutely, because the changes are what makes us change our decisions as well. You know, do we need to give this patient more glucose? Do we need to give it carrot syrup? Do we need to give it molasses? Or is the glucose change enough that we don't need to do anything else? So, to your point about pregnant stoxemia, if we are to supplement glucose to these animals, you know, when do we do that? You know, or when do we see a dramatic change that we need to do something about it? Or the the client needs to do something about it.
Sarah:Right, right, exactly. Okay, so we have our animals, they have their monitors, you're also collecting blood samples to check, you know, the other things. So so then you did your hypo normal and and hyper trial. How did that how'd that go?
Munashe:You know, interestingly, that was kind of like the fun part of the research because when we when we gave the insulin to try and drop the glucose, part of it was because these these animals were normal, you know, they were able to bring up their glucose very quickly, just because you know their body responded to that insulin, so they were able to bring it up. So we didn't get a really big dramatic drop in the glucose. It did drop, but I mean not dramatically. For most of the ghosts, it was still within the range of what we'd consider as normal. When it came to increasing the glucose, the sedative did increase the glucose quite dramatically. And the most of them did urinate quite a bit just because there was a lot of glucose in the in the urine, so it was pulling water into the urine as well. So that was kind of like interesting to see, you know, again, you also bring up a good point that, you know, because we're using normal anmos, you know, that might be slightly different to an animal that's sick, that's not able to manage its glucose, you know. So interestingly, you know, when we gave insulin, the the glucose went down just for only a short time, just because the animal were able to raise it again after the insulin.
Sarah:Right, just to throw out some numbers for people. Um, I looked it up. Q and um Baird in their textbook, they list uh normal glucose levels between 50 to 75, which is a big range. Is that kind of what you guys would use?
Munashe:Yeah, so we used we use the reference ranges that we have in our clinic, which is 45 to 70, so it's pretty consistent with from the textbook as well.
Sarah:Okay, and all these those their kind of normal levels were in the high 60s, low 70s.
Munashe:Correct.
Sarah:And so, and even with the insulin, they stayed right in the 60s, they didn't really go down too much. Yeah, yeah, it shows how well our bodies like to maintain us at a certain level. They're like, no, get rid of that glucose, we're just gonna pee it out. And so, and so then, okay, I had no idea that xylosine. I'm sure I learned this in vet school, but I had not remembered that xylosine did that. I mean, and that's something to definitely, you know, keep in your mind when you're using xylosine on sick patients, that it's gonna, you know, it's gonna make them hyperglycemic.
Munashe:Yeah, and and and it's it's kind of like a model that is used in in ruminant species, that it will really increase the glucose. And one of the reasons it does that is because it inhibits insulin. So insulin doesn't get a chance to drive the glucose out of the blood. So the the amount of glucose that stays in the blood is quite high. And and also that becomes a quite a significant point, especially when you talk about you know patients with other diseases, like you know, if they are. Blocked if they're not able to pee. It means if we're to use xylazine as a sedative, it means it's going to increase the amount of glucose in the blood and then in the urine, so they're going to fill up their blood even more. And if they're not able to pee, that actually could be detrimental to their health as well, because now they're filling up their blood with all this glucose that's pulling water into the blood, and yet they're not able to urine.
Sarah:I always use ACE instead of xylosine and a blocked goat. And so now I remember, relearned whatever you want to say, the mechanism a little bit more. So good for us. This is why I'm so excited that we're going over these papers and you know bringing some old new information to those of us with our boots out in the field. But the it was a very significant increase, right? Like you guys were absolutely able to cause these goats to become hyperglycemic.
Munashe:Yeah, I think, you know, we had some that went even, oh, they were up to 400, you know, from you know 70, 80 up to 400 within that first hour. Yeah. Some of the animals did get a little sedated, obviously. But I mean, they were still most of them were standing, some of them lay down, you know, on their chests, but then within a couple of minutes, they were they were up again. So and then when you look at the dose, it's quite, you know, it's it's a good amount of dose that we gave to to cause that glucose to rise. But within within 30 minutes, all of them, you know, had recovered from from the sedation.
Sarah:I bet those were the easiest blood draws for your students.
Munashe:Those were the easiest blood draws for sure. And you know, we were the whole time when we gave the medications, we're there watching them and monitoring them and everything. So yeah, they were not chewing on anything when we're trying to get the blood, you know. But then after they were feeling good, I mean we're chasing them down again.
Sarah:Were these goats at the UC Davis goat farm?
Munashe:Yeah, so we used the goats from our from our dairy, and all of them they were pre-bred, so they were pretty young, and usually I think they were about 12 months of age, so they're pretty active. And we we use more than one breed because those are the ones that were available. There's been some studies, you're probably aware of this, maybe in dogs and cats, that the thickness of the skin has some effect on you know how much glucose you can detect in the interstitial fluid. We didn't we didn't measure the the skin thickness in this study, but obviously it's something that we'll think about next time because you know that potentially can have an impact on the the amount of glucose that you can read when the skin is thick versus you know when the the skin is not as thick, you know, among the the braids that you you'll be you'll be measuring.
Sarah:I bet that would be very different in camelids, they have such thick skin. That would be interesting to look at. Yeah. I have very fond memories of that goat farm. That was my first experience with goats. I went to underground at UC Davis, and that was the first time I ever worked with small ruminants. Well, I raised sheep in 4-H, but this was my very first experience with goats was on that farm. So I have very fond memories of that. It's a good one. Yeah, it is. It's good. I mean, that was in the 90s, but it was still great. Okay, so we caused them to be hypo, we caused them to be hyper, we measured it, looked at it. Are we ready to jump into the results? We're all on the edge of our seats.
Munashe:Yeah, sure, sure. So, I mean, our the you know, to summarize, our results was mostly focused on, you know, does this device uh measure the glucose to the point that we can make decisions based on the result that we get? And this is compared to, you know, the big machine in the lab. So our main outcome is to ask the question: can we actually use this device on patients or on animals? Or can clients do that at home while they're munching their glucose? Because we want to make sure that it is accurate enough that when a client or a veteran sees the reading, they'll actually believe it and actually make good decisions based on that on that reading. So for us to do that, there's sort of like the there's two types of accuracy, if you will, that we look at. So one accuracy, or which we call the analytical accuracy, basically compares a reading from the device and the reading from the big machine. And all it simply says is that is it close enough? In other words, if I got a value of 50 on the device and I get a value of 55 on the big machine, you know, are they close enough? So that was the first type of accuracy that we're looking at. However, the closeness of those numbers doesn't say anything about whether we can make a decision based on that. It doesn't tell us more than just those two numbers. So the second type of accuracy that we're looking at was what we call a clinical accuracy. And that basically means that when we look at those numbers and plot them on a graph, are those numbers good enough for us to make a change on how we're treating that animal? In other words, we could say, well, if the value is in this in this range, I think we're good. We don't need to give anything extra. But if the value is within this range, I think we need to give that god with pregnancy toxemia some kerosyrup or some dextrose into the vein. So when we look at that analytical accuracy, which is just comparing the two numbers, the devices were not really accurate. But again, that those two numbers don't give us much. They don't say anything about whether they it's we can make a decision or not. But when we looked at the clinical accuracy, the devices were very, very good. In other words, we can we can use that value we get from the device to actually make clinical decisions, or for the client to say, oh, I think we need to give something extra to uh boost the glucose, or whatever we're doing right now, I think it's enough. Let's just stay with that until the next the next check again. So it's kind of like in summary, that's kind of like what we're looking at. So the device was pretty good on clinical accurates for both calves as well as God. So we're pretty happy about that result. That you know it tells us that, you know, if we're to use the device, at least in healthy animals, we can believe the value that we get and we can actually make clinical decisions based on that, on that range of values that we have.
Sarah:And you feel like it's accurate enough at both the hyper, the hypo and the normal to make decisions. Like it was fine at all. I know they didn't really become super hypoglycemic, so I guess that's still a question mark.
Munashe:Yeah, so for the analytical accuracy, which is just the numbers, you know, it's not great. But for the clinical accuracy, I think it's it is fair, you know, for both you know the high and the lows of the of the glucose as well. But again, you bring up a good point that you know we're looking into healthy animals that are able to sort of like get themselves back to the normal glucose. The question is, is this good for animals that are sick? You know, that are not able to adjust their glucose as fast because they are sick. And that's kind of like that's the big next question that we're looking at. You know, our focus in this study was to say these devices have been uh shown to work in cats, whether with diabetes and in dogs as well as in in in horses. Can we even consider it in you know in our in our goats and cats as well? So at least from the results that we have right now, I think it's fair to say that you know we should investigate it further when we have uh sick patients.
Sarah:Yeah. I will say one thing I was kind of disappointed in that you reported is that it's only good from well, you report it in Celsius, but 50 to 113 degrees Fahrenheit. 50 degrees. It's not 50 degrees in Buffalo for a lot of, especially during kidding season. So that's definitely something, you know, unless you have a warm barn, you know, all of my borgoats are kidding right now, and it's we're having a heat wave today at 34. So it, you know, that's one thing that I just wanted to put out there that, you know, that it's not at least what the company for the Free Centa Libre is reporting, I assume, is where that came from, is that it's not, it hasn't been tested or they don't think it's accurate in cold weather, which makes sense, but that is a little disappointing for those of us that live in the north.
Munashe:Yeah, yeah. So I mean it it is temperature sensitive and and it kind of makes sense because the devices were meant for humans, and obviously in other species, like in dogs and cats and in force, I mean, most likely, you know, they can move the animal inside, you know, and when it's when it's too cold or in the shade when it's too hot. Um, we did the research in summer, so it was pretty warm. So there was instances during the day that you know it would be 115 degrees outside. So in those cases, we'd actually have to move the animals inside um so that you know it would be cooler, or at least they'll be close to the fan so that we can actually get a reading. And if the temperature is really hot, you know, when you try and get a reading, you'll actually say on the on the reader that you know the temperature is too hot, and then you have to move the animal into a cooler place. And you bring up you know something that I never thought about. I mean, because as you know, you grew up in California, we we don't we don't get a lot of cold here. So I can imagine that on the East Coast, maybe when it's really, really cold, you know, you probably have to warm the patient up a little or keep them inside until you know it's warm enough that you can you can get a reading.
Sarah:Yeah, but the question is with it like right up against the animal's body, you know, it might be warm and like the device might be warm enough because it's right up against you know the 100-degree animal. Um I don't know. Yeah, I don't know.
Munashe:And I think they talk about you know the sensor itself, I think that's the one that's sensitive to temperature changes. So, and I wonder if you know putting bandaging material would help to keep it warm, because you know, we found that in goods you can actually get a reading, you know, even when you put a bandaging over the over the device as well. So, I mean it'll be it'll be interesting to see, you know, if you know, if you had in your practice, if we had clients that actually would use that and see, you know, what kind of cold temperatures, you know, do you not get readings, or do you get readings? So in our case, we're doing the extreme, which was the heat. So we didn't want to experience when it's really cold.
Sarah:Right, yeah. You'd have to reach reach out to your uh friends at Cornell and see if they'll do. Dr. Smith, or maybe what some of our can Canadian colleagues.
Munashe:Absolutely, yeah, yeah, yeah.
Sarah:All right, so it works. Like you we you would recommend it. Like we can absolutely do this. You just there's a few caveats. Well, if I use it on any of my pages, I'll let you know. I'll send you the data. But I won't have blood work to compare it to. I don't have a glucometer, but I do use the the other strips. Um, not for glucose, but for um ketone more more often than glucose. Well, thank you so much for joining us today. We'll see you next month.
