IV Therapy: What Are Isotonic Solutions and What Are They Used For?

IV therapy, or intravenous therapy, is frequently used on patients who need immediate electrolyte or fluid replacement or drug therapy. One of the three main types of IV therapy used is the isotonic solution.

What are isotonic solutions for IV Therapy?

Most IV therapy solutions are isotonic. Isotonic solutions are designed to match the makeup of your intracellular fluid and are equal in osmotic pressure inside and outside your cells. This prevents any fluid shifting in and out of your cells. Three primary examples of isotonic solutions are dextrose 5% in water (D₅W), Lactated Ringer's solution, and normal saline solution (0.9% sodium chloride.)

Uses and contraindications for D₅W IV Therapy solution

D₅W is mostly used to treat patients with fluid loss, dehydration, or hypernatremia (too much sodium.) When D₅W is initially infused, it is an isotonic solution, but when the dextrose is metabolized, the solution actually becomes hypotonic, a solution where osmotic pressure causes fluid to shift into cells. D₅W is not good for patients with renal failure or cardiac problems since it could cause fluid overload. Also, patients at risk for intracranial pressure should not receive D₅W since it could increase cerebral edema (swelling.)

Uses and contraindications for Lactated Ringer's IV Therapy solution

A patient would need Lactated Ringer's Solution to treat sudden blood loss, dehydration, burns, and fluid loss in the lower gastrointestinal tract (sigmoid colon, rectum.) Lactated Ringer's solution has an electrolyte concentration similar to serum, but without magnesium. Patients with renal failure should also not receive Lactated Ringer's solution because it contains potassium and you want to avoid potassium overload (hyperkalemia.) Lactated Ringer's solution should also not be used in patients with a pH level above 7.5 (alkalosis.)

Uses and contraindications for normal saline IV Therapy solution

Normal saline solution has some of most uses when giving IV therapy. Normal saline solutions are used for patients with hypercalcemia (too much calcium) or hyponatremia (too little sodium), for patients who are in shock, for patients receiving a blood transfusion, and for patients in metabolic alkalosis (blood pH level over 7.45.) When normal saline solution is infused, it initially stays in the veins and expands vascular volume. Therefore, patients with hypernatremia, heart failure, or edema should not be given normal saline since it could cause fluid overload.

Sources:

Fluids & Electrolytes-An Incredibly East Pocket Guide, (2006), Lippincott, Williams, and Wilkins, Ambler PA, pp 179-181

Kozier, Barabra; Glenora, Erb; Berman, Audrey; Snyder, Shirlee J, Kozier and Erb's Fundamentals of Nursing, Chapter 52 'Fluid, electrolyte, and acid-balance' (2008) Prentice Hall New Jersey, p1455