How hemodialysis works
Hemodialysis works on two principles:
Osmosis is the ability of water to pass through the wall of a cell. This wall is called a semi-permeable membrane and acts like a filter.
Diffusion is the natural movement of particles from an area with lots of particles to an area with fewer particles.
In hemodialysis, the dialyzer (mechanical kidney) acts as the semi-permeable membrane.
- Blood flows along one side of the membrane and a special dialysis solution called dialysate flows on the other side.
- The waste products removed from your child's body diffuse, or spread, from the blood (an area with lots of waste products) into the dialysate (an area with no waste products).
- The substances that the body needs cannot pass through the semi-permeable membrane. These stay in the blood that is returned to your child's body.
How hemodialysis takes blood from the body and returns it
Blood is taken out and returned through a central venous line or fistula.
The central venous line is a tube that is inserted in your child's body during a minor operation under general anesthetic. The tube is put into the major blood vessels leading to your child's heart and sits at the top of the right side of the heart.
A fistula is created by sewing together an artery and a vein in the arm during surgery. Two needles are inserted into your child's arm: one sends blood to the dialyzer for cleaning and another returns the blood to your child's body. Over time, the vein becomes bigger, which creates easier access for the dialysis needles.