Isotonic vs hypotonic vs hypertonic

  1. 1
    Can someone clarify the difference between the three types of IV solutions and give examples of when you would use each?
    KjmcavinnRN likes this.

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  2. 21 Comments...

  3. 4
    No, do your own homework or Google it.
  4. 5
    Quote from SonorityGenius
    No, do your own homework or Google it.
    It doesn't ornurse is a student (previous post -"I've been a nurse for 7 years"), even if she was there are more civil ways to answer that.

    OP - you might find this helpful:'
    rnccf2007, Nccity2002, Skips, and 2 others like this.
  5. 18
    All have to do with manipulating osmosis, which is the movement of fluid (specifically solutes as in salts like Na+Cl- and KCl-) across a semi-permeable membrane from an area of lesser to greater concentration. It helps if you remember that salt always follows water - so think where it is you want that water to go and you'll arrive at your answer as to what you'd treat with what. Ideally, extracellular and intracellular balance is maintained in healthy individuals, but get sick or injured and the balance can get thrown out of whack.

    Hypotonic - solution has less sodium than that of the patient's currently circulating plasma. Would be used to push fluid from the vascular spaces into the cells. Too much and the cells will explode. Will decrease circulating volume, so you'd use it when you don't want increased pressure like cerebral edema, or in a dehydrated patient with very high electrolytes, etc...

    Isotonic - has same sodium concentration of plasma. Use to replace volume in cases of blood loss, or to maintain hydration. No fluid shift between vascular spaces and cells - they're equalized.

    Hypertonic - has a greater concentration of sodium than circulating plasma. Pulls fluid from the cells into the vascular spaces. Too much and the cells will crenate or shrivel up like prunes. Will rapidly expand circulating volume and might be used to treat bad burns, septic shock, etc...

    Hypo and Hyper tonic solutions should be used carefully and patient observed for signs that treatment has progressed beyond the theraputic response.

    Hope that helps a little. Sometimes it helps if you don't try to memorize things as much as to stop and think what is actually going on and then use your logic (and certain basic concepts you DO need to memorize) to determine what's needed to fix whatever it is that's going on. You're never going to be able to memorize everything you'll go insane trying. Using your critical thinking skills is vastly superior over rote memorization because memory only takes you so far. But critical thinking will help you react to those weird things that come at you from left field.
    Last edit by Anisettes on Jun 2, '11 : Reason: spelling
    z7trl1, sallyrnrrt, OCNRN63, and 15 others like this.
  6. 4
    Oh, sorry - I just saw the previous post that you're not a student, didn't mean to lecture. Don't feel bad, I've been doing this for 20+ years and there are still things I get hung up on and have to stop and think 'now how does that go again?'
  7. 12
    That was a very nasty way to respond to my post, if you didn't want to answer than just don't! I thought this was a site to help each other out, not tear each other down. i'm not a student, I've been in a specialized field for 7 years. I was asking the question because sometimes its easier to comprehend something when people put it in laymans terms! I have googled and was just looking for some clarification.
  8. 2
    hi ORnurse,

    once a student asked this question (2006) and VickyRN gave this response: i thought is so very helpful!

    Tonicity refers to the solute concentration of a solution outside a cell and its effect on cellular fluid volume. The osmolarity of the solution determines the direction of water flow into or out of the cell. In normal body situations, solute concentration within and outside of the cell is usually nearly the same (isotonic).

    Isotonic: same osmolarity as the cells (270 – 300 mmol/L). Equal solute and water—exact same number of particles in both solutions—no net movement of water. Does not change cell volume.

    Higher solute concentration surrounding cells pulls water out of the cells. Hypertonic: higher osmolarity than cells (> 300 mmol/L). Greater solute, less water—water moves out of cells. The cell will shrink.

    Lower solute concentration surrounding cells causes water to move into the cells. Hypotonic: lower osmolarity than cells (< 270 mmol/L). Less solute, more water—water moves into cells. The cell will swell.

    Isotonicity. If the concentrations of electrolytes are the same in the cell and surrounding fluid, the situation is balanced (homeostatic). The cell fluid volume remains the same.

    Hypertonicity: The cell will shrink (crenation) by loss of its fluid to the surrounding hypertonic environment. High osmotic pressure of surrounding fluid pulls fluid out of the cell.

    Hypotonicity. In a hypotonic environment, fluid will enter a cell and cause it to swell and burst. The inside of the cell has higher osmotic pressure than the surrounding fluid, so fluid is drawn into the cell.

    Both hypertonicity and hypotonicity in the extracellular fluids will destroy cells.

    Need isotonicity for cell homeostasis, for balance.

    ½ NS IV is hypotonic relative to cells. Fluid moves from the vascular space into the cells. When a liter of ½ NS is administered intravenously, it will go into the cells and very little will remain in the blood vessel (since it is hypotonic).

    If you put two isotonic solutions side by side, no fluid shift occurs. A liter of normal saline or Ringer’s lactate is limited to the extracellular space and will expand the blood volume.

    5% Dextrose in NS is hypertonic compared to cells; pulls water into the vascular space from the cells or interstitium.
    camarogirl512 and nurse4forever like this.
  9. 4
    Remember, them that has gets.

    The area that has the most salt (solutes) is going to get more water... water will always follow the solutes around.
    sweetmammarn, Esme12, VivaLasViejas, and 1 other like this.
  10. 0
    MunoRN: Thank you for your comment in my defense and thank you for the link, it was very helpful
    Anisettes: You have nothing to apologize for, i found it very helpful! Thank you again
  11. 0
    Thank you very much for your response, it was very helpful!

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