Lactated Ringer's and Normal Saline are examples of which type of solution?

• A. Crystalloid
• B. Colloid
• C. Hypertonic solution
• D. Dextrose solution

Answer: (A)

Crystalloids are solutions with small molecules that freely diffuse across capillary walls, so they distribute quickly between the intravascular and interstitial compartments. Lactated Ringer's and normal saline fit this category because they contain electrolytes in water and do not contain large molecules that stay in the blood. As a result, these fluids expand the extracellular fluid volume but only temporarily—the majority eventually equilibrates with the interstitial space. This contrasts with colloids, which have large molecules that remain in the intravascular space longer due to oncotic pressure, and with hypertonic or dextrose-containing solutions, which differ in osmolality or glucose content. Therefore, lactated Ringer's and normal saline are crystalloids.