Hypertonic IV Solutions

(Here’s where you can read an UPDATED VERSION of this article about Hypertonic Solution)

If you’re looking for a list of IV solutions to memorize, then you’re in the wrong place.

But if you want to understand WHY and HOW IV solutions work the way that they do so that you can become a better nurse…here you go!

Osmosis Results Part 1 (from left to right) Hypotonic solution, Isotonic solution, Hypertonic solution
Osmosis Results Part 1 (from left to right) Hypotonic solution, Isotonic solution, Hypertonic solution

If you haven’t already seen the results of my osmosis experiment from last week, make sure to check that out, because I’ll be referring to it in all of my posts this week.

When talking about IV solutions, most people would be tempted to jump right into Isotonic, because those are the most commonly used.  But I just can’t wait to talk about Hypertonic IV fluids because after doing my osmosis experiment last week, I think they’re really stinkin’ cool.

And yes, I do realize that makes me a really big nerd 🙂

Let me back up a second.  Do you understand what Hypertonic solutions are?  It’s a fluid that contains a higher amount of solute than whatever we’re comparing it to.  How’s that for a vague sounding definition?  Seriously though, in nursing, we’re always comparing solutions to the human body!  So when we say that an IV solution is Hypertonic, what we are really saying is that it has a higher solute to solvent ratio than blood does.  Blood basically becomes our definition of what “Isotonic” means, but that article will come later this week.

Why do I think hypertonic fluids are so cool?  Just take another look at the “after” pic from my osmosis experiment up above!  The permeable membranes (aka eggs) that were in the Isotonic and Hypotonic solutions only had a very minor size difference…but the egg placed in the hypertonic solution shows a drastic change!  The water has been sucked out into the hypertonic solution via osmosis, causing a very serious case of egg-dehydration.

Applying this concept to nursing can be a little bit confusing at first.  After all, it’s hard to visualize how a patient could become “dehydrated” as a result of us putting IV fluid in them!  Let me break it down a little bit for you.

Water leaves the RBC in an attempt to dilute the hypertonic fluid around it

With this egg experiment, we were only really working with one semi-permeable membrane:  the egg membrane.  The human body is much more complex, and has many different parts that interact and influence each other.  The body also has more than one semi-permeable membrane to help regulate where fluid in the body is supposed to be.

One of many semi-permeable membranes happens to be located around Red Blood Cells (RBC).  So if you’re not careful RBCs that begin to get “dehydrated” like that are going to die unless the water balance is reversed.  Obviously, that’s not a good situation for our patient to be in!  So even though our patient appears to be well-hydrated, and perhaps has been urinating appropriately, they’re RBCs are dehydrated simply because of the type of solution we injected into their body.

Another semi-permeable membrane you need to consider as a nurse is the blood vessel walls.  When you inject hypertonic solution into the blood vessels, not only do you risk draining RBCs, but that hypertonic solution is also going to attract water from outside of the blood vessels!  All of this additional water moving by osmosis into the blood vessels can quickly cause high blood pressure (and all the complications that come with it) if not done carefully.

So what type of IV solutions are hypertonic?  These are the common ones:

Notice that three of the solutions contain Dextrose, which is a sugar.  The dextrose is included as a way of providing extra calories to the patient.  In fact, even though these dextrose solutions are hypertonic, once the dextrose is absorbed by the body then only pure water or saline is left in the blood vessels.  These three solutions are primarily used for the purpose of providing the patient with extra calories.

3% saline is typically used to treat severe cases of hyponatremia (low sodium).  This makes sense because if your blood stream has become hypotonic and it’s supposed to be isotonic, then adding a hypertonic solution will help increase the electrolyte imbalance back to normal levels.  Even so, though, you need to infuse the IV solution very slowly and cautiously, and watch the patient closely for any evidence of intravascular overload (aka too much fluid in the blood vessels).  This could be increased blood pressure, pulmonary edema (aka fluid in the lungs), or even hypernatremia.

Hypertonic solutions can also be useful for a patient who needs electrolytes but is already on fluid overload, such as in Heart Failure or severe edema.  That way you are providing the patient with needed electrolytes, but minimizing the extra water that their condition doesn’t get worse.

I hope this gives you a better understanding of hypertonic IV solutions!  Now please leave a comment below telling me how cool you think my shrunken egg is.  🙂  And of course, you can ask questions about this topic, too!

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82 thoughts on “Hypertonic IV Solutions”

  1. What other fluids could treat hyponatremia? My instructor said D5w ns won’t work but D5w LR would work. I don’t understand why she said that.

    1. HYPOnatremia wouldn’t be helped by D5w bc once the dextrose (aka sugar) is quickly used up then all you’re left with is free water, which is hypotonic. That will make the problem worse if the patient already has hyponatremia.

      D5LR would work bc after the dextrose is used up, then there is Lactated Ringers solution left, which is isotonic. The isotonic solution would add some fluid, but also electrolytes to help correct the hyponatremia.

  2. Hi,
    Thanks so much for your great explanation.
    One question still remains for me.
    If we give hypertonic solutions to patients with heart failure for the purpose of replacing electrolytes, fluid is going to be pulled into the intravascular compartment from insterstitial space and Intracellular space in order to dilute the hypertonic side(inside blood vessel), doesn’t that cause hypervolemia and worsens heart failure?

    1. This is Ragi again. Hypertonic solutions with administration of Lasix and careful monitoring of Potassium would be a better choice?

      1. yeah, i think for the heart and kidney failure too, when we want to reduce the enema with hypertonic fluid, and all the fluid will enter the blood vessel, still there will be more heart problem , because the heart trying to pump the water in the vessels, and give the heart much work.. maybe theres any other way to reduce the edema? sorry for bad english

    2. Giving hypertonic fluids would not necessarily lead to immediate osmosis from the interstitial or intracellular spaces if the patient was already low on electrolytes to begin with, it would first bring their electrolytes up to normal range.

      Keep in mind that this is an extremely complex situation, and often these patients have multiple health concerns. This is not generally something you would run into during nursing school.

  3. Hi Nicole,

    I just wanted to clarify to make sure I understand.

    With hyponatremia caused by a excess of water, commonly it is treated with fluid restriction..but since that can cause seizures because of less volume in the vascular space and more “pull” from the intracellular space, you can use 3% saline VERY carefully and in small amounts to correct the sodium level (because 3% saline has MORE sodium) and water level (because it is HYPERTONIC it will increase oncotic pressure and draw water from the cells), but you must monitor the patient to make sure they don’t develop fluid overload?

    Sometimes it’s such a dizzying circle of confusion, keeping everything straight!

  4. Hello,
    This was very well explained! Thank you!

    SO I’m not exactly a nurse,,, but I am in grade 12 Biology.. hoping to become one!
    I am doing an EEI (assignment) on osmosis and using a very similar experiment – but to modify it I need different types of hyper/hypotonic liquids – would you know any other examples apart from water or corn syrup, otherwise, what you would suggest I look at using?

  5. I want to commend you for a great job done. I understand you explanations but I want to ask about the electrolytes…for the example you gave about hyponatremia. how does the hypertonic solution normalize the sodium levels? is it that Sodium ions are in the hypertonic solution or something about ion channels?

    1. Yes, the hypertonic solution contains a higher concentration of sodium ions than the blood. So when you give a hypertonic solution to someone who has hyponatremia, you are essentially mixing a liquid with high concentration of Na (the hypertonic solution) with a liquid having a low concentration of Na (the hyponatremic blood). When you mix the two in the blood vessels, it will help normalize the concentration of Na in the blood. Hope that clarifies!

  6. Hello- I just took a test and the question was – If your patient has Edema what IV fluid would you give ?

    The correct answer was Dextrose and Lac. ringers ? Can someone explain this to me ?

    Thank you

  7. sooo.. someone is dehydrated when there is fluid missing from the rbcs and tissues outside the blood vessels and hypovolemia is just missing fluid
    from the blood vessels??

  8. Finally I am beginning to understand fluids.. thank u so much

    A patient is having mild diarrhoea and is anorectic, not taking much water… If hypertonic solution is given to this patient, will it lead to grave dehydration ? Or severe diarrhoea.. ? Please reply

  9. harry kgwarana

    please help me to investigate the flow rate water in drips for different patients in hospitals and advise medical personnel on its importance

  10. I thank you for taking the time to explain everything so clearly. I wasn’t understanding the differences in IV fluids but your video and posts are so easy to understand. You are a great teacher. Please keep teaching always.

  11. Thanks for the help. So if someone is dehydrated, they would need either a hypotonic or isotonic solution to the cell?
    Also, it’s worth mentioning that when we talk about hyper/hypo/isotonic solutions, we must include what it is hypet/hypot/isotonic to. For example, it would be like saying “that sandwich is older”. Older than what? Hyper/hypo/isotonic are all relative terms, so they have to be in relation to something else.
    Thanks!

  12. I am preparing for my broad I would like to know if you do review classes I would like to do one with you please.

  13. I graduated in December 2014 but moved out of state two days after graduation. I am finally going to get to take my NCLEX in April and have been reviewing and have found that your site has made things easy to understand. Wish I would have found this site when I was in nursing school. Great Job!

  14. so what you are saying is that if a patient came in with hyponatremia, you could give them a hypertonic OR isotonic solution to correct the imbalance?

  15. Can we give Hypertonic solutions to treat pitting edema?

    Also, if we give too much hypertonic solutions, we create pitting edema because of increased hypersonic pressure??

    Thank you so much

  16. Your website has been quite helpful to me while studying for my RN boards. Just wish I had found you when I started nursing school…would have made the whole process much less stressful !! Thanks!

  17. Deam… I really though I was going to see here definitions, action, uses, side effects, and nursing considerations. I really need them I’m looking for sodium hypertonic.

  18. I’m currently reviewing for my board exam and I’m beyond happy for finding your website! Hope I found this a little bit earlier though. Haha. More power! God bless and thank you!

  19. For me personally; this was always a really easy topic in general chem class , but applying this concept into practicality and nursing makes it complicated and worth to ponder about…..
    You are really nice to do this, I wish there were more nurses like you ! 🙂

    Thank you.

  20. What a relief to find someone on the Internet who actually has the facts straight. I’m beginning to get a grasp on things by reading your posts. I noticed that some of them are 2013. Are you still available?
    Thank you so much.
    Kim Houston

  21. This might be an odd question but I was learning about hypernatremia and it said that it causes peripheral edema. While trying to figure out why that was so, I came across this post. Now when I think of hypernatremia, I think of a hypertonic solution. Which is why I don’t understand why it would cause peripheral edema. When I think about it simply, I understand that the increased solute in the vessels will cause the fluid to shift out of the cells… but I thought it would go into the vascular space thus increasing blood pressure instead of sitting in the interstitial space. Is that right? Can you explain more succinctly why hypernatremia causes peripheral edema? Thanks in advance!

    1. Good thought process! When you dig into hypernatremia a little bit more than I did in this article, you see that the fluid shift is not only about the blood vessels. Another major factor going on is that the fluid is leaving the CELLS to help dilute the hypernatremia in the blood vessels. So individual cells throughout the body are getting dehydrated (like my shriveled little egg in the picture). Hypervolemia is the body’s attempt to dilute the solute in the blood vessels enough to prevent problems from the hypernatremia. Once the sodium is diluted enough to slow down or stop pulling water into the blood vessels, then excess water can continue to accumulate in other areas of the body. Also, there’s so much water moving from inside the cells to outside the cells, that it’s not all going to get into the blood vessels immediately…it will gradually move there via osmosis, but in the meantime there will be edema.

      Of course, this is still partly a simplification, because this is not a one-way process (the water leaves the cells and goes directly to the blood vessels to dilute sodium). There’s always a “back and forth” going on as water moves in and out of cells AND blood vessels in an attempt to reach homeostasis.

      1. really cool 🙂
        That blood vessel and the other spaces are the most important to take into consideration because it is confusing when one only thinks of rbi or cells…

  22. I am having trouble understanding how TPN does not dehydrate the patient. Since TPN is hypertonic, wouldn’t it pull fluid from outside the blood vessels causing dehydration and FVO?

    1. Since TPN contains all the nutrition the body needs (protein, fat, carbs, etc), then those things don’t stay in the blood vessels long enough to attract a lot of water. Instead, they leave the blood vessels and go into the body cells where they are needed. That’s why TPN typically won’t cause a fluid imbalance.

  23. Sumayya Samreen

    When a medical patient needs to have additional fluids injected into their veins in order to increase blood volume, should the nurse use pure distilled water or isotonic solution?

    1. Good question, Barbara.

      No, you would definitely NOT want to use this for sickle cell crisis. With sickle cell, the RBCs are already abnormal (in the sickle shape). Plus, when a patient gets dehydrated it can trigger a sickle cell crisis. So one of the nursing actions is going to be to do things that support hydration for a sickle cell patient. In most cases, those patients will get an isotonic IV solution. Just picture in your head that you’re filling their blood vessels up with more fluid so that the sickle shaped RBCs have more room to float around and are therefore less likely to get “stuck.”

  24. I’m a PICU nurse, trying to better understand one of my patient’s “cerebral salt wasting” condx and the need for 3% Saline. This was very helpful!! Thank you!!

  25. I like how simply you put the process.

    I originally found this article while looking around online for help with a question regarding the physiologic reaction to fluid administration… I am having a hard time finding a site that explained the difference between the administration of hypertonic solutions for replacement vs dieresis… but more specific than a definition…

    …does it first work by replacing any lost solutes then if administration is continued it begins to pull water/fluids from ISF/ICF.?. …or do the solutes in the administering bag dictate which operation is done.?.

    any help would be appreciated

    (…I have the same confusion with hypotonic solutions…)

    1. Hi Liz,

      Since the body is so complicated, it’s not going to be a completely cut and dry process, meaning that the IV fluid isn’t going to first do one thing, then stop doing that to do another thing. It will be more of a gradual progression depending on the current balance of fluid and electrolytes. It’s one of the ways the body tries to maintain homeostasis.

      That being said, when a hypertonic solution is administered then the electrolytes in the blood vessels will increase. As they increase, they encourage water from outside of the blood vessels to enter the blood vessels through osmosis. Some of this water can be from RBCs or other cells that you don’t necessarily want losing fluid, but usually the electrolyte lab values (especially sodium) will be abnormally high before that happens. Then as more and more fluid enters the blood vessels, the blood pressure will increase. And increased blood pressure is a big factor in how much urine healthy kidneys can output: the higher the blood pressure, the more urine created.

      1. thanks for your explanations, i am slowly getting it, but then i am confused when you say water from RBC’s will enter the blood vessels, but aren’t RBC’s in the blood vessels as part of the blood already?

  26. For burn cases, which solution should we give, hypertonic or hypotonic? Since the body would get extremely dehydrated I think hypotonic should be given? What particular type of I.V. it would be? I’m currently doing my self-review for NCLEX, I want to make sure I didn’t forget my college learnings. Thank you Nicole 🙂

    1. Oops nope, burn will cause fluid shift so the cells will swell therefore we need to give hypertonic for the aid of those cells. I’m a bit confused.

      1. Actually, an isotonic solution such as Lactated Ringers is usually given for burn patients. The goal is to get the patient rehydrated as fast as possible to prevent or at least reverse hypovolemic shock that often occurs as a result of burn injury. That’s also why they will often put in two large bore IVs upon arrival at the hospital, or even insert a central line in some cases.

        Keep thinking things through, but don’t try to make it too complicated! 🙂 The ultimate goal for fluids in a burn patient is simply to make sure they have enough fluid in their blood vessels.

    1. Whenever you have severe fluid overload in the blood vessels, the pressure in the vessels can become so strong that it starts pushing fluid out into the interstitial space. This is especially true in the smaller capillaries, such as in the lungs. And when the fluid leaves the capillaries in the lungs, then you get pulmonary edema. So really, you can think of it as a result of increased BP, which is one of the first things you would be watching for anyway.

  27. I could still use a little clarification on how hypertonic solution can help with fluid overload. Thank you for the great column

    1. Basically, it patients with certain conditions, it can help by pulling fluid out of the tissues (edema), and back into the blood vessels. Once the fluid is back in the blood vessels then the extra fluid can be filtered by the kidneys and peed out of the body.

      Hope that helps clarify!

  28. Nicole Gravelle

    Your article is very interesting .I have cystic fibrosis and I am on a treatment witch consists of inhalations of hypertonic 5% saline solutions by nebuliser, Can you tell me more on this?
    Thank you.

    1. Definitely talk to your dr as s/he should be making sure that you understand the rationales for all your treatments (and I am not in a position to be giving anybody medical advice!).

      But I would guess that it has something to do with keeping your airway well hydrated and moist so that the mucus stays looser and is easier to cough out…kind of the same rationale as putting a humidifer in someone’s room when they have a cold.

  29. Excellent site. It is worth mentioning that rapid correction (more than .5meq/L/hr) of hyponatremia (via hypertonic saline or ADH antagonists) can lead to central pontine myelinolysis aka osmotic demyelination syndrome which is characterized by dysarthria, dysphagia, and paralysis.

  30. Thank you so much! I am in my first semester of nursing school and we are studying Fluid and Electrolyte balance. This helped me! If you aren’t a teacher, you should be!!

    1. Your welcome! So glad it helped. Even though I’m not a “traditional” teacher at a school, I love how the internet gives me the opportunity to be a teacher to way more students then I could reach in a single classroom. Good luck with the rest of your semester!

  31. I had a question regarding the statement for hypertonic solution being ok to give to patients with heart failure and severe edema. In our handout from the instructors it states that if a patient is on a fluid restriction and has impaired heart or kidney function the hypertonic solution will expand the intravascular compartment putting extra strain on the vascular system so do not administer… Im confused.

    1. Good question, Heather!
      What you saw on your handout is generally true…hypertonic solutions should not be given to most patients with heart/kidney dysfunction because it CAN cause water to want to enter the blood vessels in order to “dilute” the hypertonic solution. This would lead to even more fluid overload, which the malfunctioning heart/kidneys would have a tough time handling.
      What I’m talking about in this article, though, is a slightly different scenario. If you have a patient with heart/kidney dysfunction who ALSO has low electrolytes, then you need to find a way to replace the electrolytes without causing fluid overload. That’s where the hypertonic solutions can be given to these patients because they are heavy on the electrolytes but relatively lighter on the fluid. That means they can provide a lot of electrolytes with relatively little added stress on the circulatory system.
      I hope that clears it up for you!

  32. Thank you so much for your explanation. This is a confusing concept to grasp. Your experiment makes it much more understandable!

    1. Hypo/Hyper-tonicity can be really tricky to understand, but it’s so important because it involves osmosis and diffusion. If you can understand this now, it makes it much easier to understand and remember symptoms of diseases you’ll study in the future, too!

  33. Nursing student (feels like eternity)

    Amazing explanation. Perfect! I also have a test but now I completely understand it. Thank you so much you should have been my professor!

  34. I’m a nursing student, studying for our fluid and electrolyte balance test, I was having a difficult time understanding pressures, osmosis, balance, etc. I’m really glad I found your site and your egg experiment, I’ll always think of that shrunken egg when I hear osmosis! Thank you 🙂

    1. sandeep singh

      Hello sir/madam i have done my m.sc nursing but till now i am not able to understand what is hypertonic solution and how they work but when i went on your site and i read it my all quarries are totally cleared so thanks
      Thanks a lot.

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