Hey guys and welcome back to another video from The Modern Vet. I have a special guest here whose name is Emmy. She does snore so if you hear a little weird noise in the background it's more than likely her.
Sorry. So this is going to be part two to the fluid therapy series. Alright, so let's get started. So crystalloids versus colloids.
What's the difference between the two and when do we use them? Crystalloids can be broken down into hypotonic solutions such as 0.45% saline, isotonic solutions such as LRS or lactated ringers, plasmalite, or even normosol. and then hypertonic solutions such as 7.5% saline. With colloids, we have plasma, we have albumin, we have vet starch, we have heta starch.
Those are some options. Of course, there are more, but... But as far as what's commonly used in our field, those are the ones that I listed.
So again, when are we going to use one over the other? It obviously depends on your patient's clinical status, because remember, fluids are treated. drug. So one size does not fit all. Okay.
It really depends on the situation. It depends on the state of hydration. How dehydrated are they? Are they in hypovolemic shock?
Are they both dehydrated and hypovolemic? Are we using this just for maintenance? Things like that.
Now, the difference between the crystalloid, so the isotonic, hypotonic, and hypertonic, really depends on obviously what your patient needs. For the most part, we tend to grab isotonic. crystalloid formulations such as LRS and plasmolyte for instance.
In very special circumstances will we use 0.45% saline or usually it's in the case of a dog that's cardiac compromised right so significant cardiovascular disease and they need fluid therapy but they you know we obviously have to watch how much we give them because we can eat. easily overload their heart. And then for hypertonic solutions such as hypertonic saline, 7.5%, a situation in which we would use it is usually in the case of head trauma. So the average patient that walks through a door is really going to need isotonic fluids.
Of course, you have to recognize when you would deviate from that, but again, isotonic fluids are usually where you can start. The difference between plasmolyte and LRS and 0.9% saline really boils down to to potassium constituents, sodium chloride, et cetera. Those are the biggest things we look for. And really the difference between LRS and plasmalite and even normosol, the difference is as far as the ions or should say the ion concentration is, dare I say, negligible. Okay.
Sometimes it really just doesn't matter unless you're really, really being picky for whatever reasons. Now for colloids, again, it is mainly albumin or plasma or fat starch or head of starch, things like that. and we're not going to just reach for them right off the bat.
The only time, I shouldn't say the only time, but really we use them whenever we're dealing with a case of hemorrhage and the blood pressure is really low or some kind of significant loss of volume and we need to expand the intravascular space as quickly as possible. And not just that, but to make sure that it stays expanded. If you don't want to jump to colloids immediately, you can always use hypertonic saline, okay?
Because hypertonic saline is a very important ingredient. saline is obviously very concentrated given its high amount of sodium. So remember in my previous video I said that water follows solute and so if you can imagine the gradient if you're saturating the intravascular space with a lot of sodium molecules what's going to happen is that you're going to draw fluid out of the interstitium and put it into the intravascular space and so that's a great way to help boost the volume but at the same time it doesn't last as long as it would if you were using colloids so going back to chrysaloids where do they go where do they end up and again why are we using them over colloids so when we're using chrysaloids they are able to obviously go into the intravascular space, so they go into our vessels, and then they disperse through the semi-permeable membrane of the endothelium, and then they go into the interstitial space.
So whenever we are dehydrated, that means that our interstitium is dry as a Sahara. And you want to know something, the intracellular space actually bears the brunt of that dehydration. So if you can imagine the cells in a very concentrated hypertonic...
environment because the interstitium is dry. So what's going to ultimately happen if we're super dehydrated? The water from the cells is actually going to go into the interstitium and then the cells suffer. So that's what that means.
The intracellular space bears the brunt of dehydration. So again, with dehydration, our interstitium is dry. The intravascular space is usually just fine. So whenever we're giving fluids, the point is for the fluids to leave the intravascular space and disperse into the interstitium and plump it up again, okay?
Now what happens is there's only a certain percentage that will actually stay in the intravascular space, while most of it will go leave and go into the interstitium to do what it has to do. So that's something to keep in mind as we're thinking about rehydrating a dehydrated patient. When we are using crystalloids to try to resuscitate a patient who is volume depleted, we actually cannot use a regular amount that we would use if we're just dealing with a patient who's dehydrated. Because remember, only a certain amount stays in the intravascular space. And if we need this patient's volume to increase, we obviously are going to either have to use something a bit more hefty like colloids, or we're going to have to use the crystalloids at a much greater amount to make sure that the intravascular space stays plumped.
And for colloids, essentially what colloids do is they increase the volume of the intravascular space. So if we're dealing with increase the oncotic pressure in the intravascular space. And whenever you have that increase in oncotic pressure, that's how you're able to keep fluids within that space.
All right. And that's what's needed to help expand and keep expanded the intravascular space whenever you are blood volume depleted. Now, how do we know the difference between dehydration and hypovolemia?
And even with dehydration, how are we able to even assess, you know, 5% from say 8%? What is the is the cutoff between dehydration and hypovolemia? For me, I stage dehydration from anywhere from say 5%, 3 to 5, to 8%.
All right. That is for me, my range for dehydration, 5% obviously being the least and up to 8% being the worst. So if I have a patient who has been vomiting for the past two days, but still eating eating and still drinking and they come to me and their gums are a little bit tacky, but not too much.
They still maintain a decent skin tint. So there's still a bit of elasticity there and everything else seems to be okay. Heart rate's normal. You know, all the vitals are fine.
Then I'm probably going to give them like a three to 5% knowing that yes, they have lost some fluid by way of vomiting. However, they're still eating and drinking. Now, while I don't know if they're intaking the amount that they're losing, I know they're still able to replenish something. So three to 5% is kind of what I'd give them. Now, if I have a patient who has been vomiting for two days and has not been eating, has hardly been drinking anything, and when I examined them, their gums are tacky to dry and they have decreased skin turgor, meaning whenever I pull the back of their neck, it tense just a little bit, then that patient is definitely going to get around five to 6% dehydration because obviously the patient is not only losing...
fluids, but he or she is not able to replenish not even a little bit of what they've lost. So based on that alone, again, assuming the heart rate's fine, the pulses are fine, it's just the tacky to dry mucous membranes and a little decrease in skin tear, that's going to make me agree them a five to 6%. If I have a patient who has been vomiting profusely for the past two days, they have not eaten anything. They haven't had a sip of water.
They come in, they are lethargic. They're coming. are dry as a Sahara, their orbits are a bit sunken in, they definitely have a noticeable decreased skin turgor, their heart rate's a bit elevated, their pulses are starting to become a little bit too strong for my liking, then I'm definitely giving them a 6% to 8%.
That is how I would grade that for the dehydration. Now, how do you fix it? How do you fix dehydration? Whenever we say, oh, my patient's 5% dehydrated, this is what we mean. 5% of their body weight is the fluid loss, is the amount of fluid loss.
So for example, if I have a dog that is 10 kgs and I say you're 5% dehydrated, I'm going to multiply 10 by 0.05 and then that leaves me with 0.5. Now whenever you do that, it's always in liters. So what I do is I multiply that by a thousand to get to my milliliters, which is 500 milliliters.
So I interpret that as this patient has lost about 500 mils worth of fluids and needs about 500 mils in order for the hydration status to be corrected. If my patient is, say, 8% dehydrated, again, I'm going to take the weight, so 10 kgs. hypothetically speaking and i'm going to multiply that by 0.08 that would give me 0.8 and remember this is in liters but we never really say 0.8 liters right and we typically work more in milliliters when it comes to fluid therapy then we do liters so i'm going to multiply the 0.8 by a thousand and that's going to give me 800 which means that the patient has an 800 milliliter fluid deficit and that's what i'm going to have to correct now are we going to do this sub q or are we going to do this i IV. In the perfect world, depending on the overall clinical picture of this patient and given the history and things like that, we'd probably want to hospitalize them, right? So especially more so for the patient that's like six to 8% dehydrated, you know, we can offer hospitalization for like a day or two just to really give them the support that they need.
Obviously, again, it depends on what's really going on, but if it's just a simple, oh, I changed his food three days ago and now he's been vomiting. but he still kind of eats and drinks every now and then, you may not need to hospitalize that patient. So obviously you still want to help you try to correct their fluid deficit. And you can do that by way of sub-q fluids or subcutaneous fluid therapy.
So for those who don't really know what that means, that basically means putting fluids underneath their skin. And the awesome thing with cats and dogs is that their sub-q space is pretty forgiving. which is why we're able to give a decent amount of fluids underneath the skin.
We don't want to do it too much because obviously we can cause pressure necrosis. And while it's not common, it's still possible. So we just have to be careful whenever we're administering, especially a high volume of fluids underneath the skin.
All right. So now let's pretend that we're dealing with an 8% dehydrated 10K dog. What do you do?
How do you correct this fluid deficit? Okay. So whenever we're trying to come up with a fluid rate for IV, right?
It's MDO. So maintenance, dehydration, and ongoing losses. Those are the three things that we should be accounting for, okay, in our fluid rate.
In the ideal world, you're going to break it down. You're going to say, for instance, if it's a dog, maintenance fluid therapy is 60 mils per kg per day. Dehydration is going to be whatever it is in percent.
So again, we're using the 8% dehydrated dogs. So So it's going to be 8% of the weight that we're going to have to account for as far as what we're going to have to put back. And then for ongoing losses, that basically means, hey, are they still vomiting?
Are they having diarrhea? You know, are they doing a lot of panting? How can we quantify their ongoing losses?
losses. Now you can do that and be super precise because remember fluids are drugs and we really want to design our fluid therapy plan to our patient but let's just say you're not in the ideal world and things are super busy, let's just say you're working ER, and you just need to come up with something quickly. I use a little trick. The trick is maintenance at 60 mils per kg per day, maintenance and a half at 90 mils per kg per day, or twice maintenance at 120 mils per kg per day. For my dehydrated patient of 8%, I would honestly probably start them off at twice maintenance, okay?
And then. after a couple of hours, say two, three hours, I'm going to reassess and see, do I need to bump them down or do they need to stand twice maintenance for maybe the first 12 to 24 hours? So that's what I would do. And if you're going to do it like that, what I would call blind fluid therapy, then you have to be very certain that you are keeping up with monitoring their endpoints just to make sure that you are not overloading them on fluid.
Now, here's some things I look out for whenever I am in the middle of rehydrating my patient. They're in IV fluids. I always check the TPR, so the temperature and the heart rate and the respiratory rate. I don't want my heart rate to be too high.
And I don't want my, especially my respiratory rate. I don't want that to be greater than 40 to 44. Okay. Because if I see that they're starting to breathe a little bit rapid, knowing that they're in a high rate of fluids, maybe it's time to reassess the amount that I have per hour.
because it might be a bit much for them. All right, if I look at their nose and if I'm starting to see some serious nasal discharge where before they did not have that at all, then that's going to make me want to reevaluate. If I look at their conjunctiva and I see that there's chemosis, that's another indication that it's time for me to...
consider bumping down fluids. When I listen to their heart, if I start hearing a murmur, I definitely have to bump down my fluids or even stop my fluids at that point. If I hear crackles in their lungs, time to stop. Whenever we are checking their weight, yes, weight is very important. Reason being is that whenever you are dehydrated, remember you are losing a portion of your body weight.
And generally speaking, one kilogram is worth one liter of water. of fluid. So let's just say my patient is one liter behind in fluids.
Okay. So you're 10% dehydrated borderline hypovolemic. Then I'm going to say if the weight that you came in with, so let's just say you came in at 10 kgs. Well, geez, were you really 10 kgs before, or were you 11 kgs, even maybe even 12, right? And the fact that you're 10 kgs now just means that you lost a significant amount of body water.
So whenever I weigh my patient twice a day, I'm basically seeing if I'm going up, right? Because I want them to go up. I don't want them to go down. And if they are going up, how by how much? So if they're going up by say one keg, then okay, that's not bad.
But if I see that my patient went from 10 kilograms to 13 kilograms, especially with everything else considered, I'm probably going to be a little bit cautious and consider turning down my fluid rate. Anyways, I hope this was helpful. Again, it's just more so to kind of brush up and tighten things up. And...
And I really hope that it did just that for you guys. If you have any questions at all, please feel free to ask them. I love questions. And until then, I'll see you guys next video.
Bye.