Which statement correctly describes crystalloids and colloids in fluid therapy?

• A. Crystalloids replace fluid and electrolyte losses; colloids expand intravascular volume via oncotic effects; crystalloids for most dehydration; colloids for severe hypotension or hypoalbuminemia; monitor edema and coagulopathy.
• B. Colloids replace fluid and electrolyte losses; crystalloids expand intravascular volume.
• C. Crystalloids expand intravascular volume via oncotic effects; colloids replace fluid losses.
• D. Crystalloids are only used for electrolyte correction; colloids are used for all dehydration.

Answer: (A)

Crystalloids and colloids work differently in the body, which is why they’re used in different fluid therapy situations. Crystalloids are electrolyte-containing solutions that equilibrate across capillary walls, so they replace fluid and electrolyte losses but predominantly distribute into the interstitial space rather than staying in the vessels. Colloids contain larger molecules that stay largely within the intravascular space and raise oncotic pressure, pulling fluid into the vessels and expanding plasma volume more effectively per unit infused. Because of that, crystalloids are typically the first choice for most dehydration and general volume replacement, while colloids are reserved for situations needing rapid or sustained intravascular volume expansion, such as severe hypotension or hypoalbuminemia. Both require monitoring for edema and potential adverse effects like coagulopathy with some colloids. The described approach—crystalloids for most dehydration and colloids for pronounced intravascular volume needs, with careful monitoring—best captures how these fluids are used.