Understanding dialysis

The kidneys play an important role in keeping the body healthy.

The kidneys play an important role in keeping the body healthy. They retain or excrete water, eliminate wastes and toxins, and produce hormones that regulate blood pressure, stimulate red blood cell production and activate vitamin D. When the kidneys function properly, all these processes work well. But when a child develops progressive, chronic kidney disease that results in endstage renal failure (ESRD)—a condition in which the kidneys function at a fraction of their capacity—the only treatment options are dialysis or a kidney transplant.

A certain number of children with ESRD can be considered for a transplant right away. But often— whether it’s because of the child’s overall health or the availability of a donor kidney—dialysis treatment is necessary. Imitating the filtration function of a healthy kidney, the process of dialysis filters the blood to eliminate what’s not needed and keep what is needed. Dialysis is used in persons with chronic kidney failure, but it is also employed in patients with acute kidney injury to bridge the time it takes until kidney function improves.

Two types of dialysis

A patient requiring dialysis will receive either hemodialysis or peritoneal dialysis. Hemodialysis is done using a machine with a special filter called a dialyzer. The patient’s blood is pumped through special tubings to the dialyzer, where wastes and extra fluid are flushed out. The filtered blood is returned back into the patient’s body through a second tubing. Blood clotting in the system is prevented by adding heparin. Throughout the process, the patient’s blood pressure is monitored as well as the exact amount of fluid removed and the remaining levels of important minerals, such as potassium, sodium, and calcium.

Hemodialysis is usually performed in a hospital setting. The patient arrives for treatments several times a week. Each treatment lasts at least four hours. If sufficiently stable, the patient can read or watch TV.

Before starting hemodialysis, the patient will undergo a surgical procedure to create a vascular access, usually a central venous catheter or an artificial connection between an artery and a vein for efficient access to the bloodstream. It may take some patients a couple of months to adjust to the treatment.

Peritoneal dialysis uses the lining of the abdominal cavity, the peritoneum, to filter the blood. There are different types of peritoneal dialysis, mainly ‘continuous ambulatory peritoneal dialysis’ (CAPD), and ‘continuous cycling peritoneal dialysis’ (CCPD). The latter uses a machine called a ‘cycler’ to repeatedly fill and empty the abdomen with dialysis fluid during the night, while the patient sleeps.

Similar to hemodialysis, the child must undergo a surgical procedure ahead of time. In this case, a surgeon places a catheter into the patient’s abdomen 2 to 3 weeks before dialysis starts.

The dialysis solution is administered through the catheter into the abdominal cavity. The solution soaks up wastes and extra fluid from the body and is then drained into a “waste” bag. Ideally, the abdomen (peritoneum) carries some dialysis fluid day and night, thus enabling continuous filtration, similar to the natural kidneys. The physician and the nephrology nurse determine the optimal composition of the dialysis fluid, the fill volume and the frequency of fluid exchanges based on the patient’s needs.

Chronic peritoneal dialysis is usually performed at home. Therefore, patients are trained in the technical aspects of peritoneal dialysis including the cycler, mastering the rules of hygiene and sterility, and how to record blood pressure, body weight and drain volumes. Performing home dialysis can be very demanding. The Nephrology Division at the MUHC has a multidisciplinary team of nurses, dietitian, social worker and physicians devoted 24/7 to the patients it sees.