At what point during hemodialysis treatment does diffusion stop?

Diffusion during hemodialysis is the process by which solutes move across a semi-permeable membrane from an area of higher concentration to an area of lower concentration. This process continues until an equilibrium is reached, meaning that there is no longer a concentration gradient to drive diffusion.

The correct answer indicates that diffusion stops when the concentration of electrolytes in the blood equals that in the dialysate. At this point, there is no difference in concentration between the two sides of the membrane, thereby halting the movement of solutes. This is a fundamental principle of diffusion; it is driven by differences in concentration and ceases when equilibrium is achieved.

The other options do not accurately describe the point at which diffusion stops. Saturation of the dialysate does not directly correlate with the balance of electrolytes between the blood and dialysate. Similarly, the cessation of blood flow does not inherently stop diffusion since it specifically relates to the movement of solutes, not the flow rate of blood. Finally, pre- and post-dialysis electrolyte levels being equal is not a description of the diffusion process; it only measures the overall result after treatment, not the specific point at which diffusion stops.