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Dialysis is a type of kidney replacement therapy that removes metabolic waste products, toxins, as well as excess fluid and electrolytes from the blood. Most often, dialysis is required due to end-stage renal disease, which means the kidneys have lost almost all their function. Dialysis can also be used to correct fluid, acid-base, and electrolyte imbalances, and to treat drug overdoses. The two types of dialysis are hemodialysis and peritoneal dialysis.

Now, to perform dialysis, either vascular access for hemodialysis, or abdominal access for peritoneal dialysis will be needed. So, for hemodialysis in an acute setting, temporary venous access can be obtained through a catheter in the internal jugular or femoral vein. When permanent access is needed for long-term hemodialysis, an arteriovenous or AV fistula or graft is created surgically in the patient’s arm. This creates a connection between a small artery and a vein, which causes the vein to become “arterialized,” meaning it increases in size, develops thicker walls, and blood flow is increased.

Peritoneal access can be obtained by inserting a catheter into the peritoneal cavity.

Okay, let’s look at the principles of dialysis, which include diffusion, osmosis, and ultrafiltration. Diffusion is the movement of solutes from a greater concentration to a lesser concentration until the two solutions have the same concentration of solutes on either side of a semipermeable membrane. Osmosis is the health education platform that makes learning easy and fun, but in this case, it refers to the movement of fluid through a semipermeable membrane from an area of lesser solute concentration to an area of greater solute concentration. For example, glucose creates an osmotic gradient across a membrane and is able to pull fluid through that gradient. Finally, ultrafiltration is when a driving pressure moves fluid and solutes across a semipermeable membrane.


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