Dialysis is a procedure that removes fluid, electrolytes, and waste products from the blood when the kidneys fail. Chronic dialysis is needed for end-stage renal disease (ESRD), which is often caused by diabetes or hypertension. There are two main types of chronic dialysis: hemodialysis and peritoneal dialysis. Patients on chronic dialysis must follow a strict treatment schedule, limit fluid intake, and follow a special diet. Chronic dialysis can allow ESRD patients to live for many years.
When the kidneys fail due to injury or disease, it leads to a dangerous buildup of substances in the blood. Dialysis is a procedure that performs some of the functions of normal, healthy kidneys, including the removal of fluid, electrolytes, and byproducts of cellular metabolism. Dialysis can also help control blood pressure and maintain acid-base balance in the blood. When dialysis is needed for an extended period of time, it is called chronic dialysis.
Chronic renal failure leading to end stage renal disease (ESRD) is the primary indication for chronic dialysis. In the United States, ESRD is most often the result of long-standing diabetes or hypertension. Without dialysis, ESRD is fatal. Several hundred thousand patients in the United States and several million worldwide receive chronic dialysis each year.
When to start dialysis for ESRD varies significantly from patient to patient. Typically, patients have lost 85 to 90% of normal kidney function and have symptoms of ESRD. For many, dialysis becomes necessary when other medical interventions fail to adequately control fluid overload or high blood potassium levels.
Dialysis has been used as a routine treatment for ESRD since the 1960s. The patient’s blood is slowly passed through a semipermeable membrane to filter and remove fluid, electrolytes and waste products, and then returned to the patient. Undesirable electrolytes and waste products are found in a higher concentration in the blood than in the dialysis fluid and move from a higher concentration to a lower one by simple diffusion. Dialysis fluid is called dialysate and is prescribed for each individual patient by a doctor.
There are two main types of chronic dialysis: hemodialysis and peritoneal dialysis. Hemodialysis can be done in a hospital, dialysis clinic, or at home. The usual hemodialysis treatment schedule in the United States involves three to five-hour sessions, three times a week. In some patients, more frequent hemodialysis, up to five or six times a week, may better control the complications of ESRD.
During hemodialysis, the patient’s blood is passed through a membrane called a dialyzer and then returned to the patient. Less than a cup of blood is actually out of the patient’s body in the dialysis machine at any given time. For chronic dialysis with this method, healthcare professionals must be able to easily access the patient’s blood. This is usually done with an arteriovenous (AV) fistula, where a surgeon joins an artery and vein under the skin in the forearm to create one larger blood vessel.
Continuous ambulatory peritoneal dialysis (CAPD) is the other option for patients requiring chronic dialysis. The patient instills the dialysate into his or her abdominal cavity through an implanted catheter, allows the fluid to remain for several hours, and then drains the dialysate. The peritoneal membrane, which contains many small blood vessels, serves as a dialysis filter. CAPD dialysate contains a lot of glucose, which creates a concentration gradient to draw excess water from the blood.
CAPD should be performed four to five times a day. It has the advantage that it can be done at home, at work or on the go. However, it requires a highly motivated patient to keep up with all the daily exchanges. A related procedure called continuous peritoneal dialysis can also be done at home. This type of dialysis requires a machine, which makes frequent exchanges for 10-12 hours at night.
During the dialysis procedure, patients may experience low blood pressure, muscle cramps, and itching. Over time, there is a risk of infection in the AV fistula, which may require hospitalization. Patients on dialysis for several years or more are at risk of developing amyloidosis. This is a condition caused by protein deposits in the joints and tendons.
Patients receiving any type of chronic dialysis have several requirements. They must be willing to follow the strict treatment schedule to prevent unwanted fluid and electrolyte buildup. Additionally, they must limit or monitor their fluid intake and follow a special diet that limits protein, sodium, potassium, and phosphate. Most dialysis patients also take multiple medications, such as phosphate binders, erythropoietin, and calcium/vitamin D.
Unless patients with ESRD are able to receive a kidney transplant, chronic dialysis must be practiced for life. This may seem like a cumbersome procedure given the strict schedules and restrictions. Despite this, chronic dialysis can allow patients with ESRD to live for many years.
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