How Does a Hemodialysis Machine Work?

New Jersey resident Susanne Marie Capozzi is a staff RN for DaVita Dialysis at St. Joseph’s Regional Medical Center. With a graduate degree in nursing from Felician College, she is both a registered professional nurse and certified medical surgical nurse. As part of her work, Susanne Capozzi cares for chronic hemodialysis patients.

Hemodialysis is a necessary procedure for patients with advanced kidney failure. The process diverts blood out of the body to be filtered by a dialysis machine, and then returns it to the circulatory system. It involves inserting two needles into the patient: one for blood leaving the body and one for the blood entering. The flow rate of the blood entering the machine is controlled by a pressure monitor working in tandem with a pump.

The core of the dialysis machine consists of a number of membranes surrounded by a fluid called dialysate. The membranes are in the form of tiny mesh tubes whose functions mimic that of the capillaries in a kidney. The dialysate consists of electrolytes, water and salt in proportions specific to the patient’s needs; it balances the electrolytes in the blood and helps draw out the toxins.

As blood passes through the tubes, its toxins and waste filter out into the dialysate through tiny pores in the membranes. The used dialysate is then pumped out of the machine; alongside, the cleaned blood is pumped back into the body.