When would isotonic solutions be preferred in IV fluid therapy?

Isotonic solutions are preferred in IV fluid therapy for fluid resuscitation because they have a similar osmolarity to plasma, which allows them to expand the intravascular volume without causing significant shifts of water into or out of the cells. This property is particularly important in situations of hypovolemia, such as in cases of hemorrhage or severe dehydration, where rapid volume replacement is critical.

When isotonic fluids are administered, they effectively increase blood volume and pressure without leading to complications like cellular swelling (which can occur with hypotonic solutions) or dehydration of cells (which happens with hypertonic solutions). Common isotonic fluids used in clinical practice for resuscitation include Normal Saline (0.9% NaCl) and Lactated Ringer's solution, both of which help restore adequate circulation swiftly, ensuring that vital organs receive the necessary blood flow.

In contrast, the other options provided would not represent the primary use of isotonic solutions. While they can play roles in correcting dehydration and maintaining electrolyte balance, these goals are generally achieved through a more nuanced approach using a combination of isotonic and sometimes hypotonic or hypertonic solutions, depending on the clinical scenario.