Which type of fluid includes normal saline and lactated Ringer's?

• A. Crystalloids
• B. Colloids
• C. Blood products
• D. Dextrose solutions

Answer: (A)

Fluid types are grouped by solute size. Crystalloids contain small particles that freely cross capillary walls, so they distribute quickly between the intravascular and interstitial spaces. Normal saline and lactated Ringer’s are classic examples of crystalloids, used routinely for initial fluid resuscitation and maintenance because they’re inexpensive and readily available. They do not stay exclusively in the bloodstream; their effects wane as they move into tissues, especially if given in large volumes. Colloids, by contrast, have larger molecules that pull and hold fluid in the intravascular space longer, which is why they’re used differently and are more expensive. Blood products are a separate category, and dextrose solutions are also crystalloids, but the key point here is that normal saline and lactated Ringer’s fit the crystalloids category.