In this review, I will discuss hypotonic IV (intravenous) solutions.
Hypotonic IV solutions have a lower osmolarity than blood, meaning they have a lower concentration of solutes within the fluid being administered than the blood.
Due to this, osmosis causes water to move from the extracellular space into the intracellular space, which can lead to cell swelling and, potentially, rupture.
These fluids are beneficial because they help dilute the extracellular space and replenish the inside of the cell. For instance, if there is an excessive concentration of solutes in the blood, such as in cases of hypernatremia, these solutions can dilute it. Additionally, they provide free water, aiding the kidneys in excreting waste and preventing dehydration.
Some hypotonic solutions include half-normal saline (0.45% saline), 0.225% saline, 0.33% saline, and 5% dextrose in water. Notably, while 5% dextrose in water starts as isotonic, it becomes hypotonic once inside the body, thus functioning in both roles.
As a nurse, it is crucial to remember that hypotonic solutions can cause cells to swell as fluid moves from the extracellular to the intracellular space, which could lead to brain swelling.
Therefore, monitoring for mental status changes, low blood pressure, and hypovolemia is essential. Additionally, because these solutions provide free water to the extracellular space, there is a risk of over-diluting sodium levels, leading to hyponatremia.
Patients who are more fluid-sensitive, especially those with heart failure and renal failure, need careful monitoring because they may not tolerate the extra water well.
You may be interested in IV Fluid Types and IV Fluid Quiz.
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References:
Dengue Clinical Case Management E-learning. (2023). Crystalloid IV Solutions: Intravenous Fluids. Retrieved from https://www.cdc.gov/dengue/training/cme/ccm/page70749.html.
Merriam-Webster. (n.d.). Osmolarity. In Merriam-Webster.com dictionary. Retrieved March 08, 2023, from https://www.merriam-webster.com/dictionary/osmolarity
NCI Dictionary: Osmotic. National Cancer Institute. (n.d.). Retrieved March 8, 2023, from https://www.cancer.gov/publications/dictionaries/cancer-terms/def/osmotic