How is dialysis done?
Dialysis is done by using a special fluid called dialysate. Dialysate, a mixture of pure water and chemicals, is carefully controlled to pull wastes out of your blood without removing substances your body needs.
A semipermeable membrane (one with microscopic holes that allow only certain types of particles to pass through) keeps the blood apart from the dialysate. This membrane lets the wastes and fluid in your blood flow through into the dialysate. Your blood cells and larger molecules, like protein that you need, cannot fit through the holes.
There are two main types of kidney dialysis, hemodialysis and peritoneal dialysis (PD).
In hemodialysis a man-made membrane, or dialyzer, partly does the work of the kidneys to filter waste and remove extra fluid. Blood circulates through the dialyzer for several hours during a treatment, with a machine controlling the speed and several safety factors. Hemodialysis is most often done three times per week for three to four hours at a dialysis center. There are also two less common methods of hemodialysis. Nocturnal hemodialysis, typically performed in the home, involves extended treatments three or more nights a week while you sleep. Daily home hemodialysis involves two- to three-hour sessions five or six times a week. Medicare and private insurance companies may not pay for the extra treatments that are often prescribed for nocturnal hemodialysis and daily home hemodialysis.
Before you can begin hemodialysis treatment, you will need a dialysis access to allow blood to flow between your body and the dialyzer. You and your doctor will need to discuss your options to decide which access is right for you and your treatment.
Peritoneal dialysis (PD)
Peritoneal dialysis (PD) is a type of home hemodialysis. In peritoneal dialysis you fill up your abdominal cavity with dialysate through a catheter (a soft plastic tube). The peritoneal membrane that lines your abdominal cavity has many small blood vessels, so it serves as the semipermeable membrane between your blood and the dialysate. The dialysate stays in your abdomen and absorbs wastes and excess fluid from your blood for several hours. Then you drain it out and replace it with fresh dialysate.
Peritoneal dialysis (PD) is most commonly done using an automated machine, called a cycler, which allows fluid to be flushed in and out of the abdomen while a person sleeps at night. Some people choose to do a manual exchange, by performing four to five fill-and-drain exchanges per day depending on their lifestyle and dialysis needs.
Is it possible to sleep at night using a cycler for PD?
Yes. Most people have very little difficulty sleeping at night, even if they like to turn over in bed. Some people take a little while to get used to sleeping with the machine going. Others sleep well right from the start. During training for continuous cycling peritoneal dialysis (CCPD), the nurse will help you learn what to expect.
How does dialysis work?
Hemodialysis mainly works through two principles:
1. Diffusion, which is the movement of particles across a membrane with tiny holes in it (semipermeable) until the particle concentration on both sides of the membrane is equal, and
2. Ultrafiltration, by squeezing extra fluid out of the blood and through the membrane, under pressure. The pressure is supplied by the blood pump, which pushes blood through the dialyzer.
In peritoneal dialysis, there is no pressure pump to cause ultrafiltration. So, to remove fluid, PD works mainly through osmosis by using a chemical substance (in this case, sugar) to pull extra fluid across the membrane.
Which is better, peritoneal dialysis (PD) or hemodialysis (HD)?
PD and HD each have pluses and minuses. Which one is better for you will depend on your needs and lifestyle. Your doctor will be able to tell you if you are medically better suited for one treatment or the other. Most often, the choice will be yours.
PD may be a good choice if you want to keep a job because you will have more control over your treatment schedule. PD also makes it easier to travel and allows a more liberal meal plan and fluid limits. There are also no needle sticks with PD. You many also want to consider that PD can cause weight gain and body image issues due to the catheter that must stay in your abdomen. Treatments must be done with good hygiene and good technique to avoid infections, plus you need room to store the supplies.
HD may be a good choice if you want to have off-days without treatment, want to socialize with other patients, or don't want to have a catheter in your abdomen. Swimming is more possible with HD than with PD. Other aspects of HD include a more restricted diet, a more rigid treatment schedule that may conflict with work or school, more physical ups and downs, and two needle sticks at each treatment.
Newer forms of HD, like daily home hemodialysis and nocturnal home hemodialysis (done at night while you sleep) are offered in some areas. Patients who use these new treatments have a less restricted diet and say they feel better; however, there are fewer off-days. Talk to your doctor about the pros and cons of these dialysis options to find out if they're right for you.
Keep in mind that you can always change treatments if your needs change.
If I start hemodialysis, how often will I have to get treatments?
The usual schedule for hemodialysis treatments is three times a week, either Monday-Wednesday,-Friday-Tuesday, or Thursday-Saturday. You will have the same morning or afternoon time for each treatment. The length of your treatment depends on what your doctor prescribes for you. Three to four hours is common plus time to travel to and from the center, and often some waiting time when you arrive. If you don't like the treatment schedule you get, you can ask to be on a waiting list for a different time or switch to a different center.
If I start PD, how often will I have to get treatments?
Peritoneal dialysis (PD) is most commonly done on a nightly basis using an automated cylcler machine while a person sleeps. A patient will typically be connected to the cycler for 8 to 10 hours each night, and be free of dialysis during the day. Some people will choose to do manual PD, which usually means doing four to five exchanges per day. Each exchange takes 20 to 30 minutes, and they need to be spread out over the whole day to clean the blood well. A common manual PD schedule might be to do one exchange upon waking, one at lunchtime, one at dinner, and one at bedtime. A cycler can be used together with a manual exchange. The cycler can be used at night with only one exchange during the day.
Why do dialysis treatments take so long?
Healthy kidneys work 24 hours a day, 7 days a week. Dialysis replaces only a small amount of your kidney function. If you are not getting adequate dialysis, you will start to have symptoms of kidney failure, such as:
metallic taste in your mouth
loss of appetite
Your doctor may prescribe a bigger dialyzer, longer treatments, or both to be sure you get as much dialysis as you need to feel good and keep doing the things you enjoy.