Which type of fluids are typically used for maintenance therapy?

Isotonic fluids are typically used for maintenance therapy because they effectively preserve the body's fluid balance without causing shifts in cellular fluid compartments. Maintenance therapy is designed to supply the body's ongoing fluid and electrolyte needs in patients who are unable to maintain adequate intake, such as those who are hospitalized.

Isotonic solutions, typically including Normal Saline (0.9% NaCl) and Lactated Ringer's solution, have osmolarity similar to that of blood plasma, which prevents osmotic imbalance. This means that when isotonic fluids are administered, they neither draw water into cells (which would occur with hypotonic fluids) nor cause water to leave the cells (which would occur with hypertonic fluids). Therefore, they maintain a stable internal environment for hydration and electrolyte balance.

In contrast, hypotonic fluids can lead to cellular swelling and potential lysis due to water influx into cells, while hypertonic fluids can cause cellular shrinkage as water moves out of cells. Colloids are primarily used for volume expansion in cases of hypovolemia rather than maintenance therapy since they are designed to increase oncotic pressure and draw fluid into the vascular compartment. Thus, isotonic fluids are the preferred choice for steady-state fluid maintenance, ensuring appropriate hydration without