NOVA Clinical Anesthesia Exam 1 Practice

Colloids are IV fluids that contain large molecules or cells that stay mainly in the blood vessels and help pull water into the intravascular space by oncotic pressure. Albumin, dextrans, and hetastarch are classic colloids because their large molecules stay within the vascular compartment and help expand plasma volume. Blood also acts as a colloid for the same reason—the plasma proteins and cellular components remain in the vessels when infused, contributing to plasma volume expansion.

In contrast, crystalloids are simple electrolyte or sugar solutions that readily cross capillary walls and distribute between the intravascular and interstitial spaces, so they don’t stay confined to the bloodstream. This includes D5W, normal saline, Ringer’s lactate, and other dextrose or saline solutions. Dextrose solutions, after metabolism, become free water, which is another hallmark of crystalloids.