Hey everyone, it's Sarah with RegisteredNurseRN.com and in this video I'm going to be talking about body fluid compartments, osmosis, and the different types of IV fluids. So let's get started. IV fluids, also known as intravenous fluids, are special fluids that we administer to the intravascular space, which is part of the extracellular compartment space. And administering IV fluids is a very common treatment that patients get whenever they come to the hospital.
And as a nurse, our role revolves around administering these fluids to this space. And we do that per the healthcare provider's orders. And these fluids can be used to treat a wide variety of conditions, really anything that's affecting these compartment spaces where we need to replenish that fluid.
Let's say the patient's dehydrated, they may need some fluids to help them with that. or they're having electrolyte imbalance or an acid-base imbalance. We can use these fluids to help correct that.
Therefore, as a nurse you want to be familiar with the different types of IV fluids such as isotonic, hypotonic, and hypertonic. You also want to know how they work once we administer them to the body and what you need to monitor for while your patient's receiving these fluids. But before we go over these different types of fluids, I first want to go back and review the different body fluid compartments.
Now the average adult body is made up of about 60 to 70% of water. So that is a lot of fluid within our body. And this fluid has to be stored somewhere. And there are two main compartments that stores this fluid that I want you to remember. The first compartment is known as the intracellular compartment and this is the fluid that's found within the cell and intra means within so remember this is the fluid inside of our cell as you can see here.
Then we have the extracellular compartment and this is the fluid found outside of that cell and extra means beyond or outside so we're talking about that fluid that is surrounding the cell. And it is made up of the intravascular fluid, which you can see here. This is also referred to as the plasma. Then we have the interstitial fluid, which you can see here in blue, and it's just hanging out around our cells.
And then we have the trans... cellular fluid. So now let's take a closer look at these body fluid compartments with the first being the intracellular space.
So again, this was the fluid found inside of the cell. And this space actually accounts for two thirds of our body. water. So most of our fluid is inside of our cells.
And then there's the extracellular space, which again is that fluid outside of the cell. And it accounts for one third of our body water, and it includes the fluid compartments, such as the interstitial fluid compartment. And the interstitial fluid compartment is the fluid that surrounds the outside of our cells.
And this fluid plays a very vital role in helping be a medium for electrolytes and other substances to move to and from the cell to the plasma. with the assistance of the capillaries. And the intravascular fluid compartment, which again is known as the plasma, is the fluid found inside the blood vessels, which contains so many important substances like electrolytes, blood cells, and so forth. And then lastly, we have the transcellular fluid compartment.
And this is actually the smallest compartment. And this is the fluid that is found within certain body cavities, like the spinal fluid, the fluid that surrounds our heart and lungs and the joints. Now it's important to note that these compartments are really all interconnected with their own amount of water and electrolytes and they will work together to help maintain a homeostatic environment in our body. And how they do this is that they will shift water, electrolytes, and other nutrients around so we can keep that balanced environment. And they do this shifting through various processes in the body, with one of those processes being osmosis.
Therefore, in healthcare, we can administer IV fluids, let's say to this intravascular compartment to help expand it if we need to. or shift fluids around these compartments via this process of osmosis to help us correct fluid imbalances or other problems that can occur within the intracellular and extracellular spaces. So to help us understand how IV fluids do this, let's talk about osmosis.
So osmosis is a process where water is going to move from a fluid of a higher water concentration to a fluid of a lower concentration. In other words, water is going to move from a fluid that has a low solute concentration to a fluid that has a higher solute concentration. And it does this passively. It doesn't need any energy or anything from the cell.
It actually does this on its own. And it does it through a semi-permeable membrane, which is only permeable to water molecules. So let's illustrate this process by looking at this drawing. Here we have our... semi-permeable membrane which is only permeable to water and on one side of the membrane we have a lot of water molecules but we don't have a lot of solutes and on the other side of the membrane we have not a lot of water molecules but a lot of solutes so according to osmosis what's going to happen is that water is going to move from a higher concentration of water to a lower concentration of water or you can look at it this way Water is going to move from the place where there's not a lot of solutes to a place that there are a lot of solutes.
Now the big takeaway I want you to get from osmosis is that this process is highly influenced by a fluid solute concentration and depending on how concentrated that fluid is of the solutes will determine how osmosis is going to affect how water is going to shift from this extracellular space to the intracellular space or vice versa. So what is a solute? A solute is a solid that has been dissolved in a liquid. and there's many different substances out there that can become a solute in a liquid solution with one being like sodium and chloride so we can take sodium and chloride in their solid form put them in a liquid whenever we do that once they dissolve they become an electrolyte but there's still a solute in that fluid that we have now we can take that and we can administer it to the patient in their intravascular system Now depending on how much sodium and chloride we actually put in that fluid will determine how the process of osmosis is going to be affected in this extracellular and intracellular compartment. So that leads me to osmolarity.
What is osmolarity? Osmolarity is the amount of solutes within a specific fluid volume. So in other words, it's the total solute concentration per liter of solution.
So depending on that IV fluid's osmolarity will depend on how well osmosis is going to work within the body to shift fluid around these compartments. So we can term fluids as having a high osmolarity or a low osmolarity. So whenever a fluid has a high osmolarity, we're saying it has lot of solutes in that fluid.
Whenever something has a lot of solutes in it, it has less water. On the flip side, if a fluid has a low osmolarity, it has a low amount of solutes in it, meaning it's going to have more water in it. And in healthcare, we can use osmolarity to our benefit to help treat patients who are sick and need fluids replaced based on what compartment we need to treat and shift fluids around. We do this by administering various types of fluids that have different osmolarities.
or solute concentrations which will move water in or out of these compartments. Now let's talk about the different types of IV fluids and their tonicity. So again there are three main types of IV fluids.
They are isotonic, hypotonic, and hypertonic. And let the prefix and the suffix of these fluid names help you determine what type of fluid we're dealing with. So the prefix iso means equal and this means the fluid solute concentration matches or is equal to that of the blood plasma.
Hypo means low and this means that the fluid solute concentration is lower than the blood plasma. Whereas hyper means high and this means that that fluid solute concentration is higher than the blood plasma. And then when we look at the suffix tonic, this is for tonicity. And it tells us about the fluid's ability that will be entering that extracellular space, hence that intravascular space, how well it's going to move water in and out of that intracellular space, hence inside the cell, or not at all.
Will it keep it equal or is it going to build up both parts? And this is based on the concentration of electrolytes, hence those solutes, in the IV fluid. So first is isotonic IV solutions. These have the same osmolarity as the blood, so same concentration of solutes.
And with these fluids, there's going to be an equal transfer of water, so our cell is going to stay the same. Therefore, we can just use these fluids to expand extracellular fluid volume, hence our plasma. Now, why would we want to expand the extracellular fluid? Well, if the patient is experiencing a fluid loss in this space, like through vomiting, diarrhea, they need some sodium and chloride back. or they're experiencing hypovolemic shock, burns, or maybe they're going to be having surgery.
And we know with surgery, they're going to be losing a lot of blood like that extracellular fluid. Now some fluids that are considered isotonic are normal saline, lactated ringer solution, also called LR, and 5% dextrose in water. Now there's an asterisk by this and I'll tell you about this fluid here in a second because although it is isotonic, it does work as a hypotonic solution once administered.
And some things you want to remember about Isotonic solutions is that with normal saline this replaces just water, sodium, and chloride and it is the only solution we use to administer with blood. So you don't use any other solution only normal saline. And with this type of solution you have to watch out for fluid overload especially in patients with kidney and heart failure because their heart and kidneys aren't working too great and if we put too much fluid in there they can become overwhelmed and we can actually put too much fluid back into the extracellular space.
Therefore, you want to monitor their blood pressure. Make sure they're not hypertensive. You also want to check their breathing and check those lung sounds. Make sure that you don't hear any crackles which could indicate pulmonary edema where we've had fluid build up in the lungs. And then also look at their extremities, especially those lower extremities.
Make sure there's no edema present. And because we are administering sodium and chloride, you want to also check those sodium and chloride levels. Make sure that they're not increasing because this fluid could cause cause that if we give too much.
The next is 5% dextrose in water D5W. This solution replaces water and glucose. So as I pointed out earlier, it starts out as isotonic but ends up as a hypotonic solution.
And why is this? Well, in the solution is dextrose. And when dextrose enters the body, it will be used up by the body, hence metabolize. but what's left over is not very concentrated.
It's really just free water. So we have a low osmolarity and it becomes hypotonic. Therefore, because of the components of this fluid, it's not for fluid resuscitation situation. It can actually increase the blood glucose too high, causing hyperglycemia, but it can help hyperneutremia. That is where we have too much sodium in the blood.
And what this fluid will do, because it's hypotonic in the end, it can help in a sense water down that blood, hence decreasing our sodium level there. And then lastly, with LR, this solution contains water, potassium, sodium, chloride, calcium, and lactate. Now this fluid contains lactate, and lactate... Lactate can actually help increase the blood's pH by converting to bicarbonate, which is really helpful whenever we have acidotic conditions going on, like mild cases of metabolic acidosis. However, it's not for patients with liver disease because our liver converts lactate to bicarbonate or for patients who are experiencing lactic acidosis because already in the body, there's a high amount of lactic acid.
So we don't want to go and add more. And because this fluid contains potassium, you would want to monitor for hyperkalemia, high potassium level in the blood, especially if your patient has some type of renal insufficiency. Next are hypertonic IV solutions. And these solutions have a higher osmolarity than the blood. So they have a higher concentration of solutes in the fluid.
Now because of this, osmosis will cause water to leave the intracellular space. Hence, it can shrink the cell. which can help expand the extracellular space. Now why would this be beneficial? Well if we have a patient who has a severely low level of sodium, so they're having severe hyponatremia where they don't have a lot of sodium in that blood, or they have brain swelling which is cerebral edema.
Now some solutions that are considered hypertonic include 3% saline, dextrose 10% in water, dextrose 5% in normal saline, and then dextrose 5% in half normal saline. Now some things you want to remember about these fluids whenever you're administering them is that you want to use them very cautiously because they have the risk of overloading that extracellular space because we're pulling fluid from inside the cell because remember a lot of fluid hangs out inside that cell to that extracellular space, which in the end could overload our system leading to pulmonary edema. In addition, because these solutions are highly concentrated of let's say like saline, they could cause hypernatremia.
So we'd want to check sodium levels of the blood. And when you go to administer these solutions, you always want to check with your facility's protocol on how to properly administer hypertonic solutions. Because some may recommend that all hypertonic solutions have to be administered through a central line rather than a peripheral IV.
while others may say just 10% or higher concentrations have to be administered through a central line. And the reason for this is because if hypertonic solutions get in the surrounding tissue, it can be very damaging to those cells and tissue. So we have to watch out for extravasation.
And then lastly, hypotonic IV solutions. So these solutions have a lower osmolarity than the blood, hence a lower concentration of solutes in the fluid. And because of this, osmosis will cause water to move from the extracellular space to the intracellular space, which can swell the cell to the point where it may rupture.
Now, these fluids are going to help dilute the extracellular space and replenish the inside of the cell. And why would this be beneficial? Well, if there's too much solute concentration in the blood, for example, the patient has hypernatremia, we can dilute that with these solutions.
Plus, it can help provide free water to help the kidneys excrete waste and prevent dehydration. And some hypotonic solutions include half normal saline, 0.225% saline, 0.33% saline. and of course the 5% dextrose in water. But again, that started out as isotonic, but once in the body it becomes hypotonic. So it goes between both.
And some things you want to remember as a nurse about hypotonic solutions is that they cause the cell to swell because fluid is leaving the extracellular fluid and going into the intracellular fluid, which could cause brain swelling. So you want to monitor for mental status changes, low blood pressure, hypovolemia. And because we are giving some free water to the extracellular space, we could give too much. So that could really water down the sodium level. So you want to monitor for hyponatremia and then monitor patients who are more fluid sensitive, especially if they have heart failure and renal failure because they cannot handle the extra water.
Okay, so that wraps up this video. And if you'd like to watch more videos in this series, you can access the link in the YouTube description below.