Identifying Isotonic, Hypertonic, & Hypotonic Solutions Pt 1

Let’s face it, intravenous (IV) solutions, are burdensome to remember.  It’s confusing! It gets even more complicated if it shows up during your examination. How are you going to differentiate one fluid from another? If you are not familiar with the concepts of each IV solution, chances are, you’ll flunk your exam.

If only there’s just an easier way to remember the indications and mechanism of action for all three, it’ll definitely save you from hours of tedious memorization.

Fortunately, at, Mike has formulated the easiest, most amusing way to correctly identify your hypotonic, isotonic, and hypertonic solutions.

Mike’s fun study tip

When memorizing something that can be a bit confounding, it would be so much easier to connect the complicated physiology to an image that’s closely related to it.

Here’s how…

Hypotonic is for Hippo

In cases of dehydration or medication treatments, the hypotonic solution is the IV solution of choice. This is because hypotonic solutions contain fewer electrolytes and sodium. Oftentimes used if there is decreased solute level outside the cell and the goal is to shift that back inside through osmosis in order to put everything back to normal.

Now, to be able to remember that, think of hypotonic fluids as a hippo. Got it? Hypo to hippo. Why? When fluid goes into your cell, it causes the cell to become full and swollen, like a hippo.

Uses: Hyperosmolar hyperglycemia, diabetic ketoacidosis (DKA)

Hypertonic is for Skinny

On the other hand, hypertonic solutions are used when solutes are increased extracellularly. Osmosis causes water to run from inside out. If this happens, the cell will shrink.

With hypertonic solutions, the first thing that you have to think of is what would happen to someone who is hyper? They have a lot of energy that makes them do activities like running around, keeping them fit and skinny. Hypertonic solutions cause the cell to become skinny because of the fluid that escapes from it.  As Mike puts it, hypertonic is to running and running is to skinny.

Uses: Most likely given to counter the effects of fluid overload or pulmonary edema

Isotonic is for I-so-perfect

Intravascularly, isotonic solutions don’t cause osmotic shifting from the cell to the vascular spaces. There is an equal concentration of cellular conditions.

This can be remembered by simply putting it this way – isotonic is Isoperfect. And being perfect means you don’t have to change anything, you are not required to gain or lose, everything is perfect – Isoperfect.

Uses: Dehydration, surgery

As a recap, here are the things that you need to keep in mind:

  1. Hypo is to hippo. Hippo is to swollen cells.
  2. Hyper is to Skinny. Skinny is to emaciated cells.
  3. Isotonic is to Isoperfect. Isoperfect is to no exchange of fluids required.

By remembering these, you are now able to get the questions related to IV solutions in your next nursing exam. Hopefully, this was able help clear concepts that seem jumbled up for you.

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