all right you guys welcome back to another video lesson my name is eddie watson and this is icu advantage giving you the confidence to succeed in the icu by breaking down complex critical care topics and making them easy to understand if i'm able to do just that for you guys make sure and subscribe to the channel to get more critical care educational content such as this video here as well as some exciting news i finally got a website up and going so when you get done with this lesson make sure you head on over to icuadvantage. com or follow the link down in the lesson description to test your knowledge with a free quiz and be entered into our weekly giveaways all right so that said in today's lesson we're going to start off a new short series talking about some of our fluid management strategies and especially patients in the icu it's really vital that we're managing their fluid and electrolytes as they're most likely not going to be able to handle their own intake maintaining this balance is a crucial step in managing the critical illness that they are currently dealing with so let's start off talking about our types of iv fluids all right so the first step in talking about fluid management is for us to talk about the different types of fluids that we have at our disposal now as you know this is a pretty wide topic with many different types of fluid that we do have available to us i'm going to do my best to try and cover as much as i can and really as broadly as i can as we move along in this series i will attempt to cover some of our strategies for either using or not using certain fluids now remember though that this information is a general guide and you'll often find that the selection of fluids in some cases is really going to be dependent on the provider and can often vary from one to the next that said there are some foundational points and bits of knowledge that i'll attempt to try and cover in the series so let's start things off and actually talk about our fluid distribution in the body now understanding the physiology and fluid distribution in the human body is going to be an important part in the management of our critically ill patients as mentioned the different iv fluids have different metabolic consequences in order to understand the impact of these different fluids we first need to have a baseline understanding of the fluid distribution so when we look at our body's composition our bodies are actually composed of 50 to 60 water really depending on if you're male or female now we do have two major compartments of fluid in our bodies we have our extracellular fluid or ecf and we have our intracellular fluid or icf the extracellular fluid composes about a third of our fluid and we can actually further divide this into two areas first we have our plasma that's going to be in our intravascular space and this is about 20 of the ecf volume and then we have the interstitial fluid and this is going to be the fluid that's in between cells and this is about 80 of the ecf now the dividing line between our ecf and our icf is going to be the plasma membrane of our cells and what this means is that the intracellular fluid is actually going to be all the fluid that's inside of our cells and as you can see that makes up the majority of the fluid that we have in our bodies now one important thing to know is that water is going to move passively between these different compartments and between our cells there's no active transport here and really this passive movement of water is going to be driven and is really a result of both osmotic and hydrostatic pressure gradients now within these fluids we do have electrolytes and the major ones are like our sodium magnesium potassium calcium chloride and bicarb now within our extracellular fluid that these electrolytes can move freely between the vasculature and the interstitial space and so we see the concentrations are roughly about the same in these two areas now these electrolytes though because of their charge cannot freely cross the lipid membrane of cells and thus they can't enter the intracellular fluid this actually requires channels and pumps something that we refer to as the active transport and as a result we actually see strikingly different concentrations of these electrolytes in the cells versus out of the cells and the balance of these electrolytes and fluid is a major component of our body's homeostasis and its proper functioning now in addition to our electrolytes we also have proteins ones that you're probably familiar with would be like albumin and we find these within the plasma inside of the vasculature but they're not normally in the interstitial space now these proteins really help to maintain the osmotic gradient and keeping fluid intravascular now because of these proteins our plasma has a normal osmolality of 285 to 295 per liter and this is going to be important here in just a minute so keep that in mind all right so now that we have that out of the way let's actually get in and talk about the different types of fluid that we have when we talk about fluids there's really two broad categories that we can place them into we have our crystalloids and we have our colloids now the crystalloids the basics here is that these fluids contain water and then various electrolytes and other small water soluble molecules now some of the main benefits of these are the simplicity and the cost effectiveness of the fluids the multitude of different combinations available for different purposes as well as their relatively non-existent immune response now colloids on the other hand are large insoluble molecules and oftentimes proteins so blood itself and its products are colloids but we have a couple other forms as well and for the purpose of this lesson i'm actually going to exclude talking about blood products now colloids benefit from having higher osmotic pressure in the blood but they are more expensive than our crystalloids and they have potential complications with immune response so let's actually dive in a little bit deeper and talk about our crystalloids and when we talk about our crystalloids there's actually three main types that we can talk about and these types are based on the osmolality compared to that of plasma which again if you remember our normal osmolality is going to be 280 to 295. so the first type that we have is something that we call isotonic and so what this means is that they have roughly the same osmotic concentration of particles in their concentration when comparing it to our extracellular fluid or our plasma within this category we're going to find fluids that have an osmolality of 250 up to 375.
now the big takeaway here is that because they have roughly the same osmolality that these fluids are going to stay put and won't shift between our extracellular fluid and into our cells in our intracellular fluid now an important distinction here is that we are not talking about the shift from the vascular to the interstitial because both of those are considered the extracellular fluid we still will see fluid shift between those two compartments now the next type is going to be our hypertonic and these have a greater concentration of these particles giving them more osmotic concentration so we're going to see an osmolality greater than 375. because of this greater osmolality that this is going to lead to fluid being pulled from the intracellular fluid inside the cells to the extracellular fluid so in essence we're going to attempt to dehydrate the cells in order to have the fluid enter into the extracellular fluid and then finally the last type we have is what we call hypotonic so these then have less concentrations of these particles giving them less osmotic concentration so here we're going to see that osmolality less than 250 and so as you can imagine on the flip side that this is going to lead to fluid moving from the extracellular fluid to the intracellular fluid so we're going to see that fluid shift inside of the cells and then with these categories we can also further subclass these fluids into what we call either balanced or unbalanced and this is comparing them to the balance of natural plasma and i'm going to touch on more as i go through these different fluids so on that note let's actually talk about some of the common fluids that we have and in order to best compare these i'm actually going to make a table in order to talk about some of the different components and so the first thing that i want to list here is actually our normal plasma this is going to be our base and then we're going to compare the other fluids to this so here with our plasma we have a normal osmolality of 280 to 290 we have a normal sodium of 135 to 145 normal potassium of 3. 5 to 5.
2 calcium of 4. 4 to 5. 2 magnesium from 1.
8 to 2. 4 bicarb from 22 to 26 and lactate of 1. all right so let's start with the different isotonic fluids that we have and we're going to begin talking about normal saline or our 0.
9 ns so normal saline has an osmolality of 308 so it's actually slightly hypertonic now the only things that are going to be contained in this fluid are going to be 154 of sodium and 154 of chloride for the rest of these electrolytes we're going to have zero and because of this this is actually what we call an unbalanced fluid as you can see it's really out of line with what we would normally find in our plasma now normal saline is probably the most commonly used fluid though but it does have some issues because of the concentration of chloride is significantly above the level that we find in plasma that large volumes of this can actually lead to hyperchloremic metabolic acidosis normal saline also has negative effects on our gfr and is associated with acute kidney injury and our thoughts on this are that the hyperchloremia may lead to inflammation and edema really reducing renal blood flow and we see renal clearance is about 30 to 40 percent slower than when we compare it to our balance fluids all right so next fluid we're going to talk about is going to be our lactated ringers or our lr so here we have an osmolality of 273 so this one's actually slightly hypotonic now our lr is going to contain 130 of sodium a potassium level of 4 chloride at 109 calcium at 3 and we're going to find a lactate of 28. so as you can see this is a lot closer to what we would normally find in our plasma therefore we actually consider this to be a balanced fluid and then you might be wondering about the lactate here and the reason that it's included here is that the lactate is actually going to be metabolized into bicarb by the liver and serve as a buffer now that said we do have some potential issues with lr as well again because it's slightly hypotonic that this may lead to a slight intracellular fluid shift which could worsen cerebral edema and increase icps and our patients with head injuries as well as patients with hepatic hypoperfusion are not going to metabolize that lactate rapidly there was another development of something that we call ranger's acetate which uses acetate instead of lactate to try to get around this problem but essentially patients with these liver issues are not going to get the benefit of the lactate and the lr all right so then let's talk about another isotonic fluid this is something that we call plasmalite now plasmalite technically comes in some different formulations and it really was designed to more closely resemble that which we find in plasma so here we're going to see an osmolality of 295. this is going to be containing in the solution a sodium of 140 potassium of 5 chloride of 98 magnesium of 4 and then instead of lactate this actually uses the acetate so we'll find a level of 27 as well as they also use sodium gluconate and we'll find that with a level of 23.
now again as its name suggests and as you can kind of see from its composition that we do consider this one to be closely similar to what we find in plasma thus this is going to be another balanced fluid now it's interesting because there is some debate about which balanced fluid is better lr versus plasmalite and there definitely are some potential benefits to one over the other but we don't necessarily have a clear winner or any clear studies that demonstrate one is necessarily better over the other now like i mentioned plasmalite is going to have the acetate and gluconate which again these are used and converted to bicarb and they basically serve as a buffer the nice thing is that while the liver does play a role in some of this there are other areas throughout the body in which we see this conversion and it happens a lot quicker than lactate now specifically though there are some questions around whether or not gluconate is actually metabolized to produce bicarb in our body if it's not actually happening we're not really getting the benefit of that in the buffer now with plasmalite though we do see a lower risk for hyperchlorimic metabolic acidosis and we can actually use this one with red blood cells as well so again those three normal saline lr and plasmalite those are going to be our isotonic solutions so now let's move on and talk about a hypertonic solution there's really only one that i'm going to talk about here and this is going to be our three percent normal saline although we can actually find this in higher concentrations as well so for the three percent we're going to find an osmolality of 1030. so as you can see this is definitely a hypertonic fluid and so this one is going to work to draw fluid from that intracellular space into the extracellular space now one of the most common uses for this is going to be in the treatment of cerebral edema we're going to pull that fluid out of the cells shrinking the cell size down we can also use three percent to treat severe symptomatic hyponatremia but because of its high concentration of sodium that this can lead to hypernatremia as well as hyperchloremia and if we give this medication too fast that it can result in intravascular volume overload all right and then moving on in the next type of fluid that i'm going to talk about is going to be our hypotonic fluid and then here again i'm really just going to talk about one and that is going to be our half normal saline so our 0. 5 ns now we can also find this one in lower concentrations of sodium as well but for our half ns we're going to find an osmolality of 154.
so once again you can see this is definitely on the hypotonic side and the reason that we call it half ns is because it basically contains half the amount of sodium and chloride so our sodium is going to be 77 here and our chloride is going to be 77 as well and then once again we're not going to have any other electrolytes in here so once again this one's going to be definitely an unbalanced fluid now here due to the decreased osmolality that we're going to see fluids shifting from the extracellular fluid to the intracellular fluid so shifting from outside the cells to inside the cells now because of this it's really important that we're not using hypotonic solution with patients that have head injuries again if we have that fluid shift to the intracellular fluid that this is going to lead to a increase in the cell size basically increased cerebral edema and thus increased intracranial pressure because of its lower sodium content we can't actually use this fluid to treat patients with hypernatremia as well as our half ns does make a good option to replace our patients free water deficit now if we do rapid administration of this fluid though that this can lead to the hemolysis of red blood cells and it can also lead to the depletion of intravascular volume and thus lead to cardiovascular collapse so definitely important things to know here all right so those were our major basic common types of iv fluids i hope you can kind of see the difference between the balanced and unbalanced and the hypo iso and hypertonic so now i want to move in and actually talk about some of our dextrose containing fluids and these fluids are actually quite interesting because they start initially in one category but as the dextrose is metabolized that they decrease in their osmolality now because we have the dextrose available for metabolism that they are actually going to add calories so there's two main concentrations that we're going to see most often that's going to be our five percent dextrose and our 10 dextrose in the 5 percent we're going to find 50 grams of dextrose per liter so we're going to see 170 calories per liter with this fluid for our 10 dextrose this is basically just double so we're going to have 100 grams per liter giving us 340 calories per liter so an important thing to know though while we are getting calories from this fluid that these are definitely not supplements for regular nutrition for our patients all right so there's five different types of fluids that i want to talk about and the first one is going to be our only one that actually starts off as an isotonic fluid and that's going to be our five percent dextrose in water or our d5w so here this one starts with an osmolality of 253 but as that dextrose is metabolized that this is going to basically become free water which is clearly hypotonic so once again those same restrictions and and using hypotonic fluids in the cases of head injuries we definitely are not going to want to use this one as well so then the remaining four that i'm going to talk about are ones that actually start out hypertonic and the first one is going to be our five percent dextrose in half normal saline so our d5 half ns and this one's going to start with an osmolality of 406 but as we metabolize the dextrose as well we're going to see it shift into half normal saline and thus become another hypotonic solution now the next one i'm going to talk about is five percent dextrose in normal saline so our d5ns this one starts with an osmolality of 560 but again it's gonna shift to normal saline and become isotonic over time next will be our five percent dextrose in lactated ringer so our d5lr and then this one starts with an osmolality of 527 again making it hypertonic but then it's going to shift into lactated ringer and once again become another isotonic solution and then the last one i'm going to talk about is our 10 dextrose in water so d10w so this one actually starts with an osmolality of 505 again making it hypertonic but as that dextrose is metabolized we're going to be back into free water which once again is another hypotonic solution so the dextrose containing solutions are very interesting on a couple different fronts you have to be aware of sort of where they're starting where they're going to end up and then also be aware that you are getting calories to your patient as a result of this as well all right and then finally we are going to hit real briefly on our colloids now our colloids we refer to as volume or plasma expanders and the main drive with the use of colloids is the high oncotic pressure that they have now given that these proteins and molecules don't pass from the vasculature to the interstitial space they stay within the blood vessels the thought is that they're going to work to pull fluid into the vasculature and keep it there longer than what we see with crystalloids with crystalloids usually within about 30 minutes we see it balance out within the vasculature in the interstitial space to that normal balance that we find naturally of 20 vasculature and 80 interstitial this can lead to peripheral edema in our patients and not having as much of that fluid available in the vasculature for things like pressure support so by having this osmotic pressure within the vasculature that isn't able to escape into the interstitial space it's going to allow that fluid to stay more readily or even pull some of that fluid from the interstitial space into the vasculature now that said there is potential harm in disease processes that have associated capillary leak disorders so here think about your sepsis and your ards and the reason for this is that we're actually going to see these proteins and molecules which normally would stay within our vasculature that they're going to leak out into that interstitial space and so now we're going to have this osmotic pressure that's actually pulling fluid out of the vasculature creating more of this edema and and some of these capillary leak disorder processes are going to make things even worse so let's talk real quickly about a couple different colloids that we have at our disposal and again i'm going to exclude blood and its blood products which is interesting that i say that because actually the first one i'm going to talk about is albumin and basically this is human albumin we derive it from large pools of plasma and pull out just the albumin protein and so it's interesting because some places do treat this as a blood product while others don't and just like any other fluid or medication so make sure you know how your particular hospital or how your particular facility handles this and make sure that you follow your policy that way now we can find our albumen in two different concentrations it either comes in five percent or 25 percent now the 5 which is going to be the larger bottles that this one we see has a osmolality of 309. the 25 albumin is the more concentrated smaller bottles and this one actually has a higher osmolality as you would imagine this one is 312.
