Colloid solutions are indicated when more rapid hemodynamic equilibrium is required in conjunction with crystalloids. Which description best defines colloids?

• A. Solution of low molecular weight ions and rapid equilibrium with extracellular space
• B. Hetastarch and albumin
• C. Solution of high molecular weight proteins and large-chain glucose polymers
• D. Crystalloid solutions such as LR and NS

Answer: (C)

Colloids are solutions made of large-molecule substances that stay largely within the intravascular space and generate oncotic (osmotic) pressure, pulling fluid from the interstitial space into the blood. This makes them especially effective for rapid plasma volume expansion when used alongside crystalloids.

The description that best defines colloids is a solution of high molecular weight proteins and large-chain glucose polymers. These large molecules do not easily cross capillary walls, so they remain in the blood vessels, increasing oncotic pressure and drawing fluid into the vascular compartment to support hemodynamic stability.

In contrast, crystalloids consist of small, freely diffusible molecules and rapidly equilibrate with the extracellular fluid, requiring larger volumes to achieve the same intravascular expansion. Examples like LR and NS illustrate this. While colloids can provide faster intravascular volume support, crystalloids are distributed more widely, which is why combining them is sometimes used to optimize hemodynamics.