A client recently started on hemodialysis wants to know how the dialysis will take the place of his kidneys. The nurse’s response is based on the knowledge that hemodialysis works by:
A. Passing water through a dialyzing membrane
B. Eliminating plasma proteins from the blood
C. Lowering the pH by removing nonvolatile acids
D. Filtering waste through a dialyzing membrane
Correct Answer: D. Filtering waste through a dialyzing membrane
Hemodialysis works by using a dialyzing membrane to filter waste that has accumulated in the blood. Dialysis largely replicates the functions of the kidneys in patients with chronic kidney failure. Hemodialysis takes over the key tasks of the kidneys, removing waste materials, toxins, excess salt and fluids from the body.
Option A: In hemodialysis, an artificial kidney (hemodialyzer) is used to remove waste and extra chemicals and fluid from the blood. To get the blood into the artificial kidney, the doctor needs to make an access (entrance) into the blood vessels. This is done by minor surgery to the arm or leg.
Option B: The transfer of metabolic toxins through the membrane into the dialysis fluid is based on natural processes. This process is known as diffusion. When blood and dialysis fluid with different concentrations of molecules are separated by a semipermeable membrane, the molecules move through the membrane to the lower concentration. However, large proteins and blood cells are too big to pass through the small membrane-pores, so they remain in the blood.
Option C: A dialyzer is an artificial filter containing fine fibers. The fibers are hollow with microscopic pores in the wall, also known as semi-permeable dialysis membrane. To remove toxins during hemodialysis, a special dialysis-fluid flows through the filter, and bathes the fibers from the outside, while the blood flows through the hollow fiber. Due to the semi-permeable dialysis membrane, toxins, urea and other small particles can pass through the membrane.