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.