Nearly every patient you meet is going to be on some sort of intravenous (IV) fluid, which is why knowing the different types of solutions are so important! Let’s dive in and learn the difference between Isotonic, Hypotonic, and Hypertonic solutions commonly used as IV fluids.
Isotonic
Isotonic solutions are some of the most basic IV solutions. They are used to hydrate a patient who has lost fluid through vomiting, sweating, blood loss via trauma, and burns. When thinking about isotonic solutions, think ‘Isotonic solutions stay where I put them.’
Isotonic fluids enter into the vascular space via an IV and stay there. The fluid does not venture out of the vascular space. Because of this, isotonic fluids will increase the blood volume and pressure. It will also increase the exertion of the heart by adding more fluid into the entire vascular system. Therefore, isotonic fluids are contraindicated in patients who already have high blood pressure (aka hypertension), cardiac disease/malfunction, and renal disease.
Examples of isotonic solutions are NS (aka Normal Saline), LR (aka Lactated Ringer), D5W (Dextrose 5% in Water), and D5 1/4NS (Dextrose 5% in 0.22% of Normal Saline).
Hypotonic
Hypotonic solutions are slightly more advanced than isotonic solution in the action of absorption. They are used to hydrate a patient who once again has lost fluid through vomiting, sweating, blood loss via trauma, and burns. However, since its absorption mechanism is a bit different, hypotonic solutions can be used in even more patients than isotonic solutions.
Rather than going straight into the vascular system and staying there, hypotonic fluids enter through the vascular system and are then shifted out into the surrounding cells. This helps to hydrate individual cells rather than the vascular system. When thinking about hypotonic solutions, think ‘Hypotonic solutions ooze out into the surrounding cells.’
Since hypotonic fluids ooze out to the surrounding cells, there isn’t a concern for increased blood pressure. Which means they are safe to be used on patients with hypertension, cardiac disease/malfunction, and renal disease.
However, now that the fluid is entering the surrounding cells, we need to be on the lookout for cellular edema, meaning too much fluid in the cells. We also need to be assessing our patients for decreased blood pressure (aka hypotension) due to the hypotonic solution oozing out of the vascular space instead of remaining there like isotonic solutions would.
Examples of hypotonic solutions are D2.5W (Dextrose 2.5% in Water), 1/2NS (aka 0.45% Normal Saline), and 1/3NS (aka 0.33% Normal Saline).
Hypertonic
Hypertonic solutions are high alert fluids, meaning they can cause damage if used improperly. Because of this, these fluids are only seen in the ICU (aka Intensive Care Unit). They are not used to hydrate a patient in the ways that we have been referring to. Rather, they are used to pull fluid from the cells back into the vascular space.
Hypertonic fluids are used in patients who are hyponatremic (low on sodium), third spacing (when too much fluid moves from the vascular space into the interstitial or ‘third space’), or has severe burns, edema (aka swelling), or ascites (a large accumulation of fluid in the abdominal cavity).
When thinking about hypertonic solutions, think ‘Hypertonic solutions enter back into the vessels.’
Because the fluid is being pulled back into the vascular space, we need to assess our patients for fluid volume excess. Patients receiving high alert hypertonic fluids are going to be monitored in the ICU and have frequent blood pressure, pulse, and cardiovascular pressure checks.
Examples of hypertonic solutions are D10W (aka Dextrose 10% in Water), 3% NS (aka 3% Normal Saline), 5% NS (aka 5% Normal Saline), D5LR (aka Dextrose 5% in Lactated Ringer), D5 1/2NS (aka Dextrose 5% in 0.45% Normal Saline), D5NS (aka Dextrose 5% in Normal Saline), and Albumin.
And that’s it! Those are the three major IV fluid solution categories to know for clinical, nursing school, and the NCLEX! Also be sure to visit Nursing Fundamentals: A Guide to IV Therapy for how to insert an IV. Good luck!
And be sure to check out all the Nursing Fundamentals Series:
Plus be sure to visit the following for more NCLEX study prep!
- Medical Abbreviations You Must Know
- How To Don and Doff PPE for Medical Professionals
- How to Pass the NCLEX in 75 Questions
- Important Lab Values to Know for NCLEX