Which action increases diffusion during dialysis?

• A. Using a bath that will provide a greater concentration gradient
• B. Increasing blood flow rate
• C. Using sterile technique
• D. Heparin administration

Answer: (A)

Diffusion across the dialyzer membrane is driven by the concentration gradient of each solute between blood and dialysate. A larger difference in solute concentration means solutes move more quickly from blood into the dialysate. So using a dialysate bath that creates a greater concentration gradient for the wastes you want to remove increases diffusion and solute clearance. Sterile technique and heparin mainly affect safety and circuit patency and do not directly change the diffusion rate. Increasing blood flow can boost how much solute is delivered to the membrane and thus overall clearance, but the direct driver of diffusion rate is the gradient created by the dialysate composition.