Which IV solutions are considered isotonic and commonly used to expand intravascular volume?

Which IV solutions are considered isotonic and commonly used to expand intravascular volume?

• A. 0.9% NaCl alone.
• B. 0.9% NaCl and Lactated Ringer's.
• C. 3% NaCl.
• D. Dextrose 5% in water

Answer: (B)

Isotonic IV fluids have an osmolality similar to blood plasma, so they stay mainly in the intravascular space and expand circulating volume without causing fluid to shift into or out of cells. Normal saline (0.9% NaCl) and Lactated Ringer's solution are isotonic crystalloids commonly used to treat hypovolemia and expand intravascular volume. They increase the circulating volume effectively with minimal immediate movement into cells or the interstitial space. Dextrose 5% in water starts as isotonic in the bag, but after the glucose is metabolized, it becomes free water and can dilute plasma, leading to potential cellular swelling and less reliable intravascular volume expansion. A hypertonic solution like 3% NaCl pulls water from cells into the vascular compartment but is used only for specific, monitored indications rather than routine volume resuscitation.

Isotonic IV fluids have an osmolality similar to blood plasma, so they stay mainly in the intravascular space and expand circulating volume without causing fluid to shift into or out of cells. Normal saline (0.9% NaCl) and Lactated Ringer's solution are isotonic crystalloids commonly used to treat hypovolemia and expand intravascular volume. They increase the circulating volume effectively with minimal immediate movement into cells or the interstitial space.

Dextrose 5% in water starts as isotonic in the bag, but after the glucose is metabolized, it becomes free water and can dilute plasma, leading to potential cellular swelling and less reliable intravascular volume expansion. A hypertonic solution like 3% NaCl pulls water from cells into the vascular compartment but is used only for specific, monitored indications rather than routine volume resuscitation.