Dialysis
Dialysis is the process of removing waste products and excess fluids from the body.
There are a number of reasons why a person may need dialysis. Making the decision to begin dialysis is not easy because it entails a major change in lifestyle, including a dependency on machines to maintain life. However, for most people, a successful dialysis program results in a reasonably normal life. Most people undergoing dialysis are able to eat a tolerable diet, have normal blood pressure, do not have anemia, and avoid progression of nerve damage and other complications.
For acute kidney failure, many doctors recommend dialysis when urine output is low, and they continue the dialysis until the person's blood tests indicate that adequate kidney function has been restored. Short-term or urgent dialysis can also be used to remove certain drugs or poisons from the body.
For chronic kidney failure, doctors may recommend dialysis when tests indicate that the kidneys are not removing metabolic waste products adequately or when a person can no longer perform normal daily activities. Dialysis may be used as long-term therapy for chronic kidney failure or as an interim measure before kidney transplantation.
Dialysis usually requires the effort of a team of people. A doctor completes a dialysis prescription, manages complications, and monitors the process. A nurse monitors the person's general well-being and mental health and educates the person about such issues as exercise. A social worker arranges transportation and home assistance. A dietitian recommends an appropriate diet and monitors the person's response to dietary changes.
 See the sidebar Reasons for Dialysis.
Types of Dialysis
There are two types of dialysis: hemodialysis and peritoneal dialysis.
Hemodialysis: In hemodialysis, blood is removed from the body and pumped by a machine outside the body into a dialyzer (artificial kidney). The dialyzer filters metabolic waste products from the blood and then returns the purified blood to the person. The total amount of fluid returned can be adjusted. A person typically undergoes hemodialysis at a dialysis center, usually outside of a hospital but sometimes located in a hospital.
Hemodialysis requires repeated access to the bloodstream. A doctor can achieve temporary access by inserting a large intravenous catheter in a big vein, usually one near the neck. An artificial connection between an artery and a vein (an arteriovenous fistula) is surgically created to make long-term access easier. In this procedure, typically the radial artery in the forearm is joined with the cephalic vein. As a result, the cephalic vein subsequently enlarges and becomes suitable for repeated puncture with a needle. When a fistula cannot be created, a synthetic graft may be surgically connected to an artery and vein. In this situation, the synthetic graft is punctured by the needle for hemodialysis.
Heparin, a drug that prevents clotting, is administered during hemodialysis to prevent blood from clotting in the dialyzer. Inside the dialyzer, a porous artificial membrane separates the blood from a fluid (the dialysate). Fluid, waste products, and electrolytes in the blood filter through the membrane into the dialysate. Blood cells and large proteins are unable to filter through the small pores of the membrane and so remain in the blood. The dialyzed (purified) blood is then returned to the person's body.
Dialyzers have different sizes and degrees of efficiency. Dialysis treatment time is usually about 3 to 4 hours. Most people who have chronic kidney failure need hemodialysis 3 times a week.
 See the table Possible Complications of Hemodialysis.
Peritoneal Dialysis: In peritoneal dialysis, the peritoneum--a membrane that lines the abdomen and covers the abdominal organs--acts as a filter. This membrane has a large surface area and a rich network of blood vessels. Substances from the blood can easily pass through the peritoneum into the abdominal cavity. A fluid (dialysate) is infused through a catheter inserted through the abdominal wall into the peritoneal space within the abdomen. The dialysate must be left in the abdomen for a sufficient time to allow metabolic waste products from the bloodstream to pass slowly into it. Then the dialysate is drained out, discarded, and replaced with fresh dialysate.
A soft silicone rubber or porous polyurethane catheter allows the dialysate to flow smoothly and is unlikely to cause damage. A catheter can be put in place temporarily at the person's bedside, or it may be surgically put in place permanently. One type of permanent catheter eventually forms a seal with the skin and can be capped when not in use.
Various techniques are used for peritoneal dialysis. In the simplest technique, manual intermittent peritoneal dialysis, bags containing dialysate are warmed to body temperature and infused into the peritoneal (abdominal) cavity for 10 minutes. The dialysate is allowed to remain there (dwell time) for 60 to 90 minutes and then drained out in about 10 to 20 minutes. The entire treatment can take 12 hours. Another technique is automated cycler intermittent peritoneal dialysis, which can reduce the need for nursing attention.
In continuous ambulatory peritoneal dialysis, the dialysate is kept in the abdomen for much longer intervals. Typically, the dialysate is drained and replenished 4 or 5 times a day. Generally three of these dialysate exchanges are performed during the day, at intervals of 4 hours or longer. Each exchange takes 30 to 45 minutes. An exchange is performed at night with a long dwell time of 8 to 12 hours during sleep.
Another technique, continuous cycler-assisted peritoneal dialysis, uses an automated cycler to perform short exchanges at night during sleep, whereas longer exchanges are performed manually--without the cycler--during the day. This technique minimizes the number of exchanges during the day but prevents mobility at night because of cumbersome equipment.
See the table Possible Complications of Peritoneal Dialysis.
Choosing a Type of Dialysis
Many factors, including lifestyle, must be considered in determining which type of dialysis is best for a person. Peritoneal dialysis can be performed at home, eliminating the need for travel to a hemodialysis center.
 See the figure Comparing Hemodialysis With Peritoneal Dialysis.
Doctors recommend hemodialysis for people with recent abdominal wounds or abdominal surgery. Peritoneal dialysis is better tolerated in people whose blood pressure fluctuates frequently between periods of high or normal pressure and periods of low blood pressure. With hemodialysis, blood pressure may be controlled simply by removing a sufficient amount of fluid during dialysis. Otherwise, drugs to lower blood pressure may be needed.
Special Considerations
People undergoing dialysis need a special diet. In people undergoing peritoneal dialysis, appetite is generally poor, and protein is lost during dialysis. The diet should be relatively high in protein, roughly ½ gram of protein per pound of ideal body weight a day. Salt, both the usual salt containing sodium and the salt containing potassium, is restricted.
For those undergoing hemodialysis, daily consumption of sodium and potassium is even more restricted. Foods high in phosphorus also may have to be limited. Daily fluid intake is limited for people who have a persistently low or a decreasing sodium concentration in the blood. Daily weighing is important to monitor weight gain. Excessive weight gain between hemodialysis treatments indicates that the person is consuming excessive fluid.
Multivitamin supplements are needed to replace the nutrients lost through hemodialysis or peritoneal dialysis. Erythropoietin or darbepoietin may be given to stimulate the production of red blood cells. Phosphate binders, such as calcium carbonate or calcium acetate, are used to remove excess dietary phosphate.
A low calcium level in the blood and severe renal osteodystrophy may be treated with calcitriol (the active form of vitamin D) and supplemental calcium.
People undergoing dialysis may experience losses in every aspect of their lives. The potential loss of independence can be especially distressing; coping with disruptions in lifestyles can be difficult. Many people undergoing dialysis become depressed and anxious. Psychologic and social counseling is often helpful to families as well as to those undergoing dialysis. Many dialysis centers provide psychologic and social support. Dealing with a loss of independence is helped when people are encouraged to pursue their previous interests. People undergoing hemodialysis need to arrange for transportation to and from dialysis centers on a regular basis. Dialysis sessions may interfere with work, school, or leisure activities.
More than half of the people on long-term dialysis are 60 years of age or older. Older people often are better able to adapt to long-term dialysis than are younger people. However, older people undergoing dialysis may become more dependent on their grown children or may not be able to continue living alone. Older people are more likely to experience fatigue from treatments. Often, family roles and responsibilities must be modified to fit the dialysis routine, creating stress and feelings of guilt and inadequacy.
Children whose growth has been stunted may feel isolated and different from their peers (see Section 23, Chapter 287). Young adults and adolescents coping with identity, independence, and body image issues may find these issues further complicated by dialysis. Diet is an important issue for children undergoing dialysis because children must receive enough nutrients to support their growth.
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