HOW DIALYSIS MACHINES WORK

These lifesaving devices take over the role of failing kidneys

- AILSA HARVEY

Without healthy kidneys, your body would quickly fill with toxins, causing it to shut down. To prevent this buildup, these two fist-sized organs are continuously working to filter out waste substances from biological processes and pass them out of the body in your urine. For people who suffer from kidney failure, an alternative method is needed to emulate this essential task. Dialysis machines, which were invented in 1943, divert blood out of the body to be cleaned before being returned to the body. Because the body is continually producing waste, patients who depend on dialysis usually undergo four hours of treatment approximately three times a week.

During the process, the machine is attached to a needle, often placed in the arm, through which blood can be extracted and returned. As the blood enters the dialysis machine, it passes along a layer of membranes. These membranes have microscopic holes that only water and waste molecules can filter through. Because of this, no blood cells are lost to the machine – they simply take a diversion on their circulatory course.

The dialysis machine’s fluid, called dialysate, consists of water, electrolytes and salts. Mimicking the concentration of body fluid found outside of your body’s cells, dialysate draws waste products across the membrane in a process called diffusion. Because the waste molecules are in higher concentrations in the blood, they pass from an area of high concentration to an area of low concentration. When the blood is returned to the vein, it’s in a similar condition to filtered blood that has passed through the kidneys.