Transudate vs exudate | Respiratory system diseases | NCLEX-RN | Khan Academy

Voiceover: So when we get into talking about plural effusions, that fluid that’s accumulating in the actual plural space, is either a transudate or an exudate, and that can be a really confusing idea to try and wrap your head around, so let’s write this just over here in the corner. We’re either talking about transudate fluid, or exudate fluid. The real difference between the two is how that fluid came about to be in that space. How did that fluid get in that space in other words. There are a couple common causes. For instance if somebody has congestive heart failure, liver failure, if somebody had pneumonia, lupus, and how we really break those up is based off of two things. Our transudate and our exudate is going to help differentiate how these things happened. Now normally when we’re talking about an exudate it’s something that was inflammatory. That would be our pneumonia. Whereas something that was transudate is something that’s changed the hydrostatic…oops, I think I spelled that wrong.

Let’s go back. Static pressure. So something that’s changed in pressure in the vessels, or something that has actually caused inflammation in the vessels, so that’s how we differentiate those two. Let’s start with this image here. What we’re looking at here is an image of a normal vessel. You’ll see that this is our vessel wall, right? Then we have our endothelial cells which are these guys poking out here. Then these little yellow dots, these represent my proteins, so my plasma protein. Then that blue fuzz, that’s going to be our actual fluid. In a normal vessel, this is normal, everything is pretty much even, it’s equal, we don’t have any fluid that’s leaking out of the vessels, we don’t have anything that’s coming in that shouldn’t be, this is our normal representation. Now if we actually come down here, and we’re going to come right below, let’s look at something that would not be normal. Let’s look at this second image that I have here.

Now what we’re looking at, this is going to represent my transudate leakage. Now in our transudate leakage, what happens? What you’ll notice is that we have less of these plasma proteins than we did in our normal scenario. As a result, having less plasma protein cells, let’s put less protein, is going to cause the fluid to actually shift out.

Let me just change my colors so we can see that we’re talking about fluid. It’s going to cause the fluid to actually shift out in between my endothelial cells outside of the actual vessels, so i’m going to have fluid shift out. Now you’ll see that the endothelial cells in the vessel, this hasn’t changed. My vessel looks the same, and the endothelial cells are still sitting next to each other. They had the same inter-endothelial spaces as they did. The only thing that’s different about this is that my protein is down, and that’s going to cause the fluid to shift out.

Another way we can have a transudate leak is by let’s say congestive heart failure. You heard me talk about that earlier. Here’s our heart, right? Here we’re going to draw our heart, I know it’s a Valentine’s heart, but just so we have an idea. We know that in our heart we have four chambers. We have our right atrium, we have our right ventrical, we have our left atrium, and our left ventrical.

Now let’s say that this person had left sided heart failure, so we’ve got heart failure on the left side. That’s our congestive heart failure. What’s going to happen? Well we know that with that failure on the left side we’re going to have increased pressure on the left side of the heart. We know that the left side of the heart will back up to our lungs. Here’s our lungs. Now if the pressure is increased that means that it’s backing up towards our lungs, and the vessels in our lungs, it’s going to cause an increase in pressure. That would be the increase in our hydrostatic pressure that causes transudate, and as a result the same idea here, that fluid that we have going on here, that fluid is going to be forced out in-between the endothelial cells because the pressure is so high. That fluid leaking out is going to leak into the actual plural space. That’s what we talk about in a plural effusion. Now what you’ll see is that the proteins aren’t leaking out, and that’s because they’re too big to fit in-between these endothelial cells.

However, with enough pressure, fluid can be squeezed out of there and that leakage again is what we call our transudate. Now our third scenario would be this. Our exudate, so if we’re talking about exudate fluid. Now how does that happen? First thing you should notice is that this vessel looks a lot bigger than the rest. It is, it’s much bigger, so i’m going to go ahead and write exudate next to this one.

Now you cans see that this vessel’s larger than the rest. Remember, what did we say was the big thing with exudate? It’s inflammatory. What happens to our vessels in an inflammatory situation? Well they’re going to dilate, right? They’re going to become bigger. We know that we’re going to have some stasis of the fluid and the proteins that are happening, not happening, but that are circulating within the vessel. We know that in an inflammatory scenario our endothelial cells you see how they’re much more spaced out? That inter-endothelial space becomes larger. Well larger inter-endothelial space means that not only is fluid going to come out, but what else? What else is going to come out of there? If you’re saying protein you’d be absolutely right.

Protein is going to come out as well. In an exudate plural effusion we have a mix of both fluid and protein in the effusion. Let’s write that over here so we have it down. We’re going to have both fluid, so this here is fluid, and protein in the ecudate fluid. Whereas in our transudate we’re just looking at fluid because nothing else can fit through. Now how do we test for this? When someone has a plural effusion, of course we do a thoracentesis, and that means that we go in with the needle, we [aserate] the fluid out of the space, out of that plural space, and we’re going to test it.

That testing is called Light’s Criteria. I’m going to go ahead over here and i’m just going to draw a light bulb. Here’s my light bulb, let’s put a little bottom on my light bulb. That’s called Light’s Criteria. You can remember how we do that. What they’re looking for in the fluid is they’re going to look for the presence of protein, they’re going to look for a presence of cholesterol, of triglycerides, and if they see those things, protein, triglycerides, basically if they’re seeing large solutes, large particles rather, then they know it was exudated.

But when they test it and there’s a low amount of protein, or a low presence of these solutes or particles that otherwise wouldn’t fit in these tiny spaces, then they know it’s a transudate. That’s how we can tell what type of fluid is present in the plural space and what was the cause of that. Quite honestly because we know in a transudate scenario that protein is not leaking out of these spaces, they may not see any protein at all. That’s going to further confirm that it’s transudate. Think about these things that we discussed. Transudate, we’re talking about the hydrostatic pressure, so that would mean that CHF, that would mean our liver failure, those things change the pressure.

Even someone that’s in kidney failure rather, so because they’re in kidney failure we know they have low protein and low protein can cause these leaky vessels to occur. Then inflammatory, we mentioned that before, inflammatory, think about things that cause an inflammatory response in the body. We’re talking about the lungs, definitely pneumonia, that’s a big one, we talked about lupus, I used that as an example, that’s an inflammatory process as well. When you see these terms think about what’s happening, right? Think about what the cause is, and think about what’s happening at the level of the vessels.

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