How Does it Work?
Hemodialysis uses a machine to pull blood out of the body, filter it, and pump the clean blood back into the body again. The actual filtering happens in a part of the machine called a dialyzer, or artificial kidney.
The dialyzer has two parts. One part is for blood. The other is filled with a cleaning solution called dialysate.
The two parts of the dialyzer are separated by a thin membrane. Blood cells and other important parts of the blood are too big to pass through the membrane. But waste products and extra fluids go through it easily.
The dialysate pulls waste and extra fluids out of the blood, through the membrane, and carries them away. The filtered blood is then pumped back to the body.
Blood flows from the body into the machine and back again through tubes. These tubes are attached to needles in the person's skin. The needles go into a large vein or artery through a vascular access. Doctors need to create this vascular access before dialysis can begin.
Creating a vascular access involves minor surgery. Most patients are awake during the procedure, but get a local anesthetic to stop feeling in the area. Surgeons usually create the vascular access a few weeks before hemodialysis starts. That way, the vascular access has time to heal.
There are three different kinds of vascular access, but they all do the same job:
Fistulas and grafts connect arteries to veins to make a bigger blood vessel. Surgeons usually create these types of vascular access in a person's arm.
Sometimes doctors use a catheter to gain access to the blood vessels. Catheters used for dialysis may go in the neck, chest, or other part of the body. They're usually temporary until the person can get a fistula or graft.