01.05 Hypotonic Solutions (IV solutions)

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Hey guys, my name is Brad and welcome to nursing.com. And in today's video, what we're going to be doing is we're going to discuss hypotonic solutions. What I'd like to do is discuss what they are, how they work, some of the different types that there are, and some of the assessment findings that we may see in patients who are receiving them. Let's go ahead and dive in. 

So whenever we're talking about hypotonic solutions, the way that I like to remember this is hypotonic hydrate cells, specifically, right? Hypotonic solutions, hydrate cells. Now, how is it able to do this, right? Now we're going to be going back kind of like to some high school chem almost.  A lot of us may have forgotten this, but what we're pretty much looking at here, right, the way that the movement of water occurs is through osmosis. And it does so across the semipermeable cellular membrane. You may remember, right, along the outside of our cells, we have a membrane called a, basically a phospholipid bilayer, but it is a semipermeable membrane. And this is a membrane, a cellular membrane that allows the passage of certain solutes and molecules as well as water to pass across this membrane and move interchangeably between the intracellular compartment as well as the intravascular compartment. So, the way in which a hypotonic fluid works is hypotonic, you can consider is less solutes, right? Let's consider hypotonic as being less solutes, or less concentrated than the cells in the body. And the way in which fluid moves, through osmosis, it moves from an area of lower concentration across the semipermeable membrane to areas of higher concentration. And so what essentially occurs here is we administer a hypotonic, or a less concentrated fluid intravenously, and what's going to occur, because this fluid is less concentrated than the cell, it is going to move into the cell and hydrate the cell. This is why we say hypotonic fluids hydrate cells. 

Of course, this is not without certain risks and benefits. So what are some of the benefits and risks that we may see associated with hypotonic fluids?  Now, in regards to benefits, we usually will see hypotonic fluids used in situations such as DKA. We may see a dextrose containing hypotonic fluid administered to try and prevent hypoglycemia from occurring as we're administering IV insulin to help treat DKA. I don't want to cloud your mind too much with the concept of DKA. Make sure you check out our other lessons on DKA if you would like further clarity regarding the administration of hypotonic fluids during DKA.  But just know that there are some benefits used in DKA with hypotonic fluids, but our risks are something that are absolutely paramount that you're going to want to be mindful of. So think about it as we're administering a hypotonic fluid intravenously, we're administering a less concentrated fluid intravenously. It's going to cause fluid to move from the intravenous compartment into the cell. Now think about it. As this occurs more and more, more and more fluid is going into the cells. What can actually happen is we can cause cellular rupture. And this is actually clinically important and instances such as cerebral edema, right? As we're administering this less concentrated fluid, fluid is going to be moving into the brain tissues. And if we over hydrate the brain tissues, remember hypotonic fluids hydrate cells, if we over hydrate the cells of the brain, this is going to lead to cerebral edema. A very big, important thing to know. Also, I want you to keep in mind something else as a concept, you might think we're administering a IV fluid, so we're hydrating our patient. Actually, we're kind of doing the opposite and this is another risk of hypotonic IV fluids.  Remember we're administering a less concentrated fluid. This is going to cause movement of water through that semipermeable membrane into the cells and out of that intravascular compartment. So what can actually occur, paradoxically, as we administer this IV fluid, instead of hydrating our patients, we're actually moving fluid from the intravascular compartment into the cell. So that's why I say it's important to know in hypotonic fluids, we're hydrating cells. That's the big differentiator we can actually intravascularly volume deplete our patients. So it's just something important to know a little caveat to the administration of hypotonic, IV fluids. 

So what are some examples of different hypotonic IV fluids that you may come across? I put these up here. I just think it's important that you familiarize yourself with them to be able to identify them for testing purposes. But essentially we're looking at a hypotonic, IV fluid as a fluid that is less than 0.9% normal saline, right? We consider 0.9%. normal saline, our everyday normal saline, as isotonic.  It’s isotonic with our blood. Hypotonic solutions or anything, essentially less than 0.9% normal saline. So it's going to be things such as 1/2 normal saline (0.45% Sodium Chloride), ¼  normal saline (0.225% NS), D5 in half normal saline (5% Dextrose and 0.45% Sodium Chloride) something that might be used in DKA, for instance, as well as D5 in water (5% Dextrose) 

But what are some assessment findings or things that we're going to keep an eye out for as nurses? Whenever we're administering hypotonic IV fluids, right, and these all kind of circle back to those risks that are associated with the administration of these fluids. Let's all remember right, as we previously described, we have the blood vessel and here we have our red blood cells. And because we're administering a less concentrated fluid, it's going to cause fluid to go from the intravascular compartment into our intracellular compartment. 

Let me also stop right there and make sure that I remind you if you have not already checked out our fluid compartments lesson, be sure to check that out as well, if you're a little bit, unsure or not quite grasping, what the heck we're about whenever we're saying intravascular compartment, intracellular compartment, et cetera. But again, our assessment findings are related to those risk factors. So as we're hydrating cells with hypotonic solutions, we are intravascularly depleting our patients of volume, right? The water is not staying in the intravascular compartment. It is exiting and moving into these cells. As that occurs, we're going to intravascularly deplete our patient of the volume in their vessels. This can cause hypovolemia. This can cause a drop in blood pressure. All as a result of this osmotic movement of fluid from our intravascular compartment into our cells. And then of course, we're going to make sure that we keep an eye out for patients experiencing headache or decreased levels of consciousness as this may be reflective of that movement of fluid into those brain tissues, leading to cerebral edema. 

And so summarizing some of our key points related to hypotonic solutions, remember hypotonic hydrate cells, not the patient.  It hydrates cells. Causing osmotic movement of fluid across that semipermeable membrane from the intravascular compartment into the intracellular compartment. Again, check out our fluid compartments videos should you need further clarity.  Also understanding the benefits and risks of using IV hypotonic fluids.  Benefits in instances, such as DKA.  And then the risk of cerebral edema, movement of fluid into the brain tissues, as well as intravascularly depleting our patients volume causing hypovolemia, causing hypotension. Also make sure that you familiarize yourself with the different types of IV fluids, as well as understanding that those assessment components that we can see in patients are all reflective of that osmotic movement of fluid into cells.  

Guys, I really hope that this video helped bring clarity to this concept of hypotonic solutions. And I hope that you're able to take the things that you learned here today forward with you and be successful on your exams. I hope that you guys go out there and be your best selves today.  And as always, happy nursing.

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