Crystalloid fluids stay in the intravascular space for less than how many hours?

• A. 1 hour
• B. 2 hours
• C. 4 hours
• D. 6 hours

Answer: (B)

Crystalloid fluids rapidly distribute from the intravascular space into the interstitial space because their small solutes freely cross the capillary walls. Because of this quick equilibration, the intravascular (plasma) volume expansion they produce is short-lived. In clinical terms, the intravascular effect of crystalloids is on the order of about two hours or less, meaning they stay in the circulation for a short time before moving into the interstitial compartment. This is why large volumes may be needed for sustained plasma volume expansion, and why colloids or blood products are sometimes preferred when longer intravascular persistence is desired.