Certified Hemodialysis Technician Practice Exam 2025 - Free Hemodialysis Technician Practice Questions and Study Guide

Potassium dialyzes out of the blood while red blood cells do not primarily because potassium is significantly smaller than red blood cells. In the process of dialysis, semipermeable membranes allow small particles and solutes to pass through while retaining larger particles. Potassium ions are small enough to pass through the pores of the dialysis membrane, whereas red blood cells are much larger and cannot fit through these openings. This distinction in size is crucial in understanding the principles of dialysis, which relies on size exclusion to separate solutes from blood components.

The other factors, such as the quantity of red blood cells, their molecular weight, or their charge, do not impact the fundamental reason why potassium can be eliminated through dialysis while red blood cells remain in circulation. The key aspect here is the physical size difference, which dictates the movement of substances during the dialysis process.