Dialysis Technician Practice Exam

What occurs during ultrafiltration in dialysis?

1. Blood is filtered through a membrane

2. Water is removed from blood due to a pressure gradient

3. Electrolytes are balanced

4. Hemoglobin is enriched in the blood

The correct answer is: Water is removed from blood due to a pressure gradient

During ultrafiltration in dialysis, water removal from the blood is primarily facilitated by a pressure gradient. This process is crucial for achieving fluid balance in patients undergoing dialysis, particularly those with kidney failure. In an artificial kidney or dialyzer, an externally applied pressure encourages water to pass through the semipermeable membrane while retained solutes, along with larger molecules, remain in the bloodstream. The pressure gradient effectively draws water from the blood into the dialysis solution, which is how excess fluid is removed. The other options describe processes related to dialysis but do not accurately depict ultrafiltration. For instance, while blood filtration through a membrane occurs in dialysis, this action is specifically part of the broader filtration process rather than ultrafiltration alone. Balancing electrolytes is an important function of dialysis as well, but it typically involves diffusion rather than just the ultrafiltration process. Lastly, the enrichment of hemoglobin in the blood is not a function of ultrafiltration; instead, it could relate to other medical processes such as transfusions, but does not pertain to the specifics of ultrafiltration in dialysis sessions.