Regarding colloids, select the correct pattern for electrolyte concentrations in ECF, volume of ECF, and volume of ICF.

• A. Unchanged; increases; unchanged
• B. Increases; increases; decreases
• C. Decreases; unchanged; increase
• D. Unchanged; decreases; unchanged

Answer: (A)

Colloids draw water from the interstitial space into the vascular compartment because their large proteins raise plasma oncotic pressure. This redistribution expands the extracellular fluid volume (primarily by increasing plasma volume) while the intracellular fluid volume stays essentially the same, since water shifts within the extracellular space rather than across cell membranes. The electrolyte concentrations in the extracellular fluid stay about the same because the movement is largely a water shift that preserves osmolar balance, not a net addition of solutes. So the best pattern is: electrolyte concentrations in the ECF unchanged; ECF volume increases; ICF volume unchanged.