Colloid fluids are characterized by which of the following?

Colloid fluids are indeed characterized by containing large molecules, such as proteins or starches, which primarily remain within the intravascular space. This is crucial because colloids have a greater oncotic pressure compared to crystalloids (which contain smaller molecules). This property allows colloids to draw and retain water in the blood vessels, thereby helping to maintain circulating blood volume and improve tissue perfusion during situations like hypovolemia.

In contrast to colloid fluids, the other options present characteristics that do not accurately describe these types of fluids. For instance, small molecules that pass through cell membranes refer more to crystalloid solutions, which are typically used for hydration. Additionally, while hydration can be a part of fluid therapy, colloids are specifically employed for their ability to expand blood volume rather than just providing hydration. Lastly, while some intravenous solutions may contain vitamins and minerals, it is not a defining characteristic of colloid fluids, which are focused more on maintaining oncotic pressure and intravascular volume rather than nutritional supplementation.