Hypotonic, isotonic, and hypertonic I.V. solutions? When are they used?

suzanne4, RN · Apr 26, 2005

Think to what you have learned so far............0.9%NS would be considered isotonic. It is equivalent to what you have in your body. Many will also consider 0.45% NS with this. Anything less in terms of NaCl would be hypotonic, and 3% NaCl would be hypertonic. D5W contains no NaCl so that is definitely hypotonic..........

You need to be careful with any solutions containing salt for patients with CHF, you will usually see D5W in just keep open amounts routinely.

If you are trying to give fluids to a dehydrated patient, you would use large volumes of 0.9% NS, or even LR.....notice no dextrose is used..............or KCL added.

Hope that this helps. Let us know if you have any more questions... ?

rschaal · Jan 28, 2011

Just a quick fyi, because I know just how confusing this subject can be. Just because a solution does not have NaCl does not make it 'not' isotonic. Tonicity is measured in mOsm/liter, which is always written on the IV solution bag. A generally rule of thumb is that (this varies from institution to institution) a solution whose osmolarity (mOsm/Liter) falls within the range of 275-295 mOsm/Liter is considered isotonic. Anything higher than 295 mOsm/L is considered hypertonic, and anything below 275 hypotonic. There are of course some exceptions, take for instance Normal Saline, or 0.9% NaCl. Its osmolarity is generally around 308, but it is still considered isotonic because it contains the electrolyte combination NaCl as its solute. D5W, a dextrose based solution, is also actually considered isotonic (while in the bag). However, it is considered hypotonic while in the body (260). Normosol-R and Lactated Ringer's solutions are both isotonic solutions (295;275). D5NS, D51/2NS, and D5LR are the most common hypertonic solutions. Hypertonic solutions are fairly commonly used, primarily to prevent fluid from 3rd spacing, and to pull fluid back into the vascular system (sometimes with things like cerebral edema, and different pathological conditions). Hypotonic solutions, like 1/2NS are also used. They are generally used in severely dehydrated patients, and 1/2NS would be used over D5W in patients who don't want extra glucose, but who may be dehydrated (like diabetic patients). Isotonic solutions are used in the vast majority of patients to help maintain homeostasis and to replace fluid and serve as a pH buffer. Hope that information was helpful! F/E balance can be a very hard concept to understand, so I hope that this information may be of some use to you all!

Woops...that was supposed to be posted on the original comment, not yours suzanne4...my bad.

2ndyearstudent, CNA · Jan 28, 2011

mookieslife said:
Hello all, I am in my first semster of nursing school and we have a test on body fluids and electrolytes. My question is...... What are the indications of each i.v. solution? Any help would be greatly appreciated- Josh

Get up from where ever you are RIGHT NOW and go buy the book, "Fluid and Electrolytes Made Easy"

Seriously, one of the most valuable books I owned during first year.

IVRUS, BSN, RN · Jan 28, 2011

In actuality, since normal serum osmolarity equals 290, a solution IS considered isotonic if it is between 240 and 340 osmolarity (+ or - 50 on either side of the 290) So, a solution isn't hypertonic until it is > 340, and it isn't hypotonic until it's below 240. Dextrose 5% is hypotonic in the body, because the dextrose is quickly metabolized and all you are left with is free water, which is hypotonic. In the bag, D5W has an osmolarity of 252.