When choosing an IV fluid solution, we look at the tonicity or amount of solute dissolved in the solvent, in other words how much stuff is in the liquid. Isotonic solutions match the concentrations within the blood. Because everything matches, there will be no shift in fluid, just volume expansion. Hypotonic solutions have less of the stuff and mostly liquid. When you administer a hypotonic solution, that excess liquid (water) has to find somewhere to go, so it typically forces its way out of the vessel by osmotic pressure. When it needs to come OUT of the vessel – it typically goes INTO the cells. So you will see some rehydration of dehydrated cells or swelling of normal cells. Hypertonic solutions have more stuff, less liquid. To create that balance, the water gets pulled INTO the vessels to balance it out. That means it pulls it OUT of the cells. This is used for severe edema, especially in the case of cerebral edema. Once the fluid is in the vessels, we can diurese it out of the body. You may also use IV solutions that contain 5 or even 10% dextrose to treat hypoglycemia, but be sure to know their tonicity and what to expect in your patient!
Date Published - Jul 12, 2018
Date Modified - May 21, 2018