NCLEX RN Practice Question 441

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Hemodialysis

Description

• Hemodialysis is the process of cleansing the client’s blood.
• It involves the diffusion of dissolved particles from one fluid compartment into another across a semipermeable membrane; the client’s blood flows through one fluid compartment of a dialysis filter, and the dialysate is in another fluid compartment.

Functions of hemodialysis

• Cleanses the blood of accumulated waste products
• Removes the byproducts of protein metabolism such as urea, creatinine, and uric acid from the blood
• Removes excess body fluids
• Maintains or restores the buffer system of the body
• Corrects electrolyte levels in the body

Principles of hemodialysis

• The semipermeable membrane is made of a thin, porous cellophane.
• The pore size of the membrane allows small particles to pass through, such as urea, creatinine, uric acid, and water molecules.
• Proteins, bacteria, and some blood cells are too large to pass through the membrane.
• The client’s blood flows into the dialyzer; themovement of substances occurs from the blood to the dialysate by the principles of osmosis, diffusion, and ultrafiltration.
• Diffusion is the movement of particles from an area of higher concentration to one of lower concentration.
• Osmosis is the movement of fluids across a semipermeable membrane from an area of lower concentration of particles to an area of higher concentration of particles.
• Ultrafiltration is the movement of fluid across a semipermeable membrane as a result of an artificially created pressure gradient.

Dialysate bath

• A dialysate bath is composed of water and major electrolytes.
• The dialysate need not be sterile because bacteria and viruses are too large to pass through the pores of the semipermeable membrane; however, the dialysate must meet specific standards, and water is treated to ensure a safe water supply.

Interventions

• Monitor vital signs before, during, and after dialysis; the client’s temperature may elevate because of slight warming of the blood from the dialysis machine (notify the physician about excessive temperature elevations because this could indicate sepsis; obtain samples for blood culture as prescribed for excessive temperature elevations).
• Monitor laboratory values before, during, and after dialysis.
• Assess the client for fluid overload before dialysis and fluid volume deficit following dialysis.
• Weigh the client before and after dialysis to determine fluid loss.
• Assess the patency of the blood access device before, during, and after dialysis.
• Monitor for bleeding; heparin is added to the dialysis bath to prevent clots from forming in the dialyzer or the blood tubing.
• Monitor for hypovolemia and shock during dialysis, which can occur from blood loss or excess fluid and electrolyte removal.