CHRONIC KIDNEY DISEASE
Oakwood Kidney Institute
Peritoneal Dialysis: A treatment Methods for Kidney Failure
With peritoneal dialysis (PD), you have some choices in treating advanced and permanent kidney failure. Since the 1980s, when PD first became a practical and widespread treatment for kidney failure, we've learned much about how to make PD more effective and minimize side effects. Since you don't have to schedule dialysis sessions at a center, PD gives you more control. You can give yourself treatments at home, at work, or on trips. But this independence makes it especially important that you work closely with your health care team: your nephrologist, dialysis nurse, dialysis technician, dietitian, and social worker. But the most important members of your health care team are you and your family. By learning about your treatment, you can work with your health care team to give yourself the best possible results, and you can lead a full, active life.
When Your Kidneys Fail
Healthy kidneys clean your blood by removing excess fluid, minerals, and wastes. They also make hormones that keep your bones strong and your blood healthy. When your kidneys fail, harmful wastes build up in your body, your blood pressure may rise, and your body may retain excess fluid and not make enough red blood cells. When this happens, you need treatment to replace the work of your failed kidneys.
How PD Works
In PD, a soft tube called a catheter is used to fill your abdomen with a cleansing liquid called dialysis solution. The walls of your abdominal cavity are lined with a membrane called the peritoneum, which allows waste products and extra fluid to pass from your blood into the dialysis solution. The solution contains a sugar called dextrose that will pull wastes and extra fluid into the abdominal cavity. These wastes and fluid then leave your body when the dialysis solution is drained. The used solution, containing wastes and extra fluid, is then thrown away. The process of draining and filling is called an exchange and takes about 30 to 40 minutes. The period the dialysis solution is in your abdomen is called the dwell time. A typical schedule calls for four exchanges a day, each with a dwell time of 4 to 6 hours. Different types of PD have different schedules of daily exchanges.
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The most common form of PD, continuous ambulatory peritoneal dialysis (CAPD), doesn't require a machine. As the word ambulatory suggests, you can walk around with the dialysis solution in your abdomen. Other forms of PD require a machine called a cycler to fill and drain your abdomen, usually while you sleep. The different types of cycler-assisted PD are sometimes called automated peritoneal dialysis, or APD.
Getting Ready for PD
Whether you choose an ambulatory or automated form of PD, you'll need to have a soft catheter placed in your abdomen. The catheter is the tube that carries the dialysis solution into and out of your abdomen. After giving you a local anesthetic to minimize any pain, your doctor will make a small cut, often below and a little to the side of your navel (belly button), and then guide the catheter through the slit into the peritoneal cavity. As soon as the catheter is in place, you can start to receive solution through it, although you probably won't begin a full schedule of exchanges for 2 to 3 weeks. This break-in period lets you build up scar tissue that will hold the catheter in place.
The standard catheter for PD is made of soft tubing for comfort. It has Dacron cuffs that merge with your scar tissue to keep it in place. (Dacron is a polyester fabric.) The end of the tubing that is inside your abdomen has many holes to allow the free flow of solution in and out. There are two types of Tenckhoff peritoneal catheters, a standard (A) and a curled (B).
Types of PD
The type of PD you choose will depend on the schedule of exchanges you would like to follow, as well as other factors. You may start with one type of PD and switch to another, or you may find that a combination of automated and nonautomated exchanges suits you best. Work with your health care team to find the best schedule and techniques to meet your lifestyle and health needs.
Continuous Ambulatory Peritoneal Dialysis (CAPD)
If you choose CAPD, you'll drain a fresh bag of dialysis solution into your abdomen. After 4 to 6 or more hours of dwell time, you'll drain the solution, which now contains wastes, into the bag. You then repeat the cycle with a fresh bag of solution. You don't need a machine for CAPD; all you need is gravity to fill and empty your abdomen. Your doctor will prescribe the number of exchanges you'll need, typically three or four exchanges during the day and one evening exchange with a long overnight dwell time while you sleep.
Continuous Cycler-Assisted Peritoneal Dialysis (CCPD)
CCPD uses an automated cycler to perform three to five exchanges during the night while you sleep. In the morning, you begin one exchange with a dwell time that lasts the entire day.
Nocturnal Intermittent Peritoneal Dialysis (NIPD)
NIPD is like CCPD, only the number of overnight exchanges is greater (six or more), and you don't perform an exchange during the day. NIPD is usually reserved for patients whose peritoneum is able to transport waste products very rapidly or for patients who still have substantial remaining kidney function.
Customizing Your PD
If you've chosen CAPD, you may have a problem with the long overnight dwell time. It's normal for some of the dextrose in the solution to cross into your body and become glucose. The absorbed dextrose doesn't create a problem during short dwell times. But overnight, some people absorb so much dextrose that it starts to draw fluid from the peritoneal cavity back into the body, reducing the efficiency of the exchange. If you have this problem, you may be able to use a minicycler (a small version of a machine that automatically fills and drains your abdomen) to exchange your solution once or several times overnight while you sleep. These additional, shorter exchanges will minimize solution absorption and give you added clearance of wastes and excess fluid.
If you've chosen CCPD, you may have a solution absorption problem with the daytime exchange, which has a long dwell time. You may find you need an additional exchange in the mid-afternoon to increase the amount of waste removed and to prevent excessive absorption of solution.
Infection is the most common problem for people on PD. Your health care team will show you how to keep your catheter bacteria-free to avoid peritonitis, which is an infection of the peritoneum. Improved catheter designs protect against the spread of bacteria, but peritonitis is still a common problem that sometimes makes continuing PD impossible. You should follow your health care team's instructions carefully, but here are some general rules:
* Store supplies in a cool, clean, dry place.
* Inspect each bag of solution for signs of contamination before you use it.
* Find a clean, dry, well-lit space to perform your exchanges.
* Wear sterile gloves to perform exchanges.
* Wash your hands every time you need to handle your catheter.
* Clean the exit site with antiseptic every day.
* Wear a surgical mask when performing exchanges if you have a cold.
Keep a close watch for any signs of infection and report them so they can be treated promptly. Here are some signs to watch for:
* Nausea or vomiting
* Redness or pain around the catheter
* Unusual color or cloudiness in used dialysis solution
* A catheter cuff that has been pushed out
Equipment and Supplies for PD
Transfer Set: A transfer set is tubing that connects the bag of dialysis solution to the catheter. Two types of transfer sets are available.
* A straight transfer set is a straight piece of tubing that stays connected to your catheter. To begin each exchange, you connect the free end to a fresh bag of solution and hang the bag higher than the catheter, usually attaching it to a special stand, so that gravity pulls the solution into your abdomen. While the solution is in your abdomen, you can roll up the bag and wear it under your clothes. When you've finished your dwell time, you take the bag out and place it near the floor so that gravity pushes the used solution down into the bag. When the bag is full, you disconnect it from the straight transfer set and connect a fresh bag of solution to start the next exchange.
* A Y-set is a Y-shaped piece of tubing that can be disconnected between exchanges. To start, you connect the base of the Y to your catheter. You then connect one branch of the Y to a fresh bag of solution and the other to an empty bag. To flush away any bacteria that might be in the transfer set, you close off the base of the Y and drain a small amount of solution from the full bag into the empty one. Then you close the branch that leads to the empty bag and let the solution flow into your abdomen. Once the bag has emptied, you can disconnect the Y-set from your catheter so you won't need to conceal a bag or extra tubing under your clothes. When it's time to empty the used solution, you reconnect the catheter to the Y-set and drain the solution into an empty bag to discard. Then you connect a fresh bag and begin the process again.
Dialysis solution comes in 1.5-, 2-, 2.5-, or 3-liter bags. A liter is slightly more than 1 quart. The dialysis dose can be increased by using a larger bag, but only within the limit of the amount your abdomen can hold. The solution contains a sugar called dextrose, which pulls extra fluid from your blood. Your doctor will prescribe a formula that fits your needs.
You'll need a clean space to store your bags of solution and other supplies. You may also need a special heating device to warm each bag of solution to body temperature before use. Manufacturers do not recommend using microwave ovens to warm solution because they change its chemical makeup.
The cycler, which automatically fills and drains your abdomen, usually at night while you sleep, can be programmed to deliver specified volumes of dialysis solution on a specified schedule. Most systems include the following components:
* Solution storage. At the beginning of the session, you connect bags of dialysis solution to tubing that feeds the cycler. Most systems include a separate tube for the last bag because this solution may have a higher dextrose content so that it can work for a daylong dwell time.
* Pump. The pump sends the solution from the storage bags to the heater bag before it enters the body and then sends it from the weigh bag to the disposal container after it's been used. The pump doesn't fill and drain your abdomen; gravity performs that job more safely.
* Heater bag. Before the solution enters your abdomen, a measured dose is warmed to body temperature. Once the solution is the right temperature and the previous exchange has been drained, a clamp is released to allow the warmed solution to flow into your abdomen.
* Weigh bag. The cycler's timer releases a clamp to let the used dialysis solution drain from your abdomen into a weigh bag that measures and records how much solution has been removed. Some systems compare the amount of solution inserted with the amount drained and display the net difference between the two volumes. This lets you know whether the treatment is removing enough fluid from your body.
* Disposal container. After the used solution is weighed, it's pumped to a disposal container that you can throw away in the morning.
* Alarms. Sensors will trigger an alarm and shut off the machine if there's a problem with inflow or outflow.
Testing the Effectiveness of Your Dialysis
To see if the exchanges are removing enough waste products, such as urea, your health care team must perform several tests. These tests are especially important during the first weeks of dialysis to determine whether you're receiving an adequate amount, or dose, of dialysis.
The peritoneal equilibration test (often called the PET) measures how much sugar has been absorbed from a bag of infused dialysis solution and how much urea and creatinine have entered into the solution during a 4-hour exchange. The peritoneal transport rate varies from person to person. If you have a high rate of transport, you absorb sugar from the dialysis solution quickly and should avoid exchanges with a very long dwell time because you're likely to absorb too much solution from such exchanges.
In the clearance test, samples of used solution drained over a 24-hour period are collected, and a blood sample is obtained during the day when the used solution is collected. The amount of urea in the used solution is compared with the amount in the blood, to see how effective the PD schedule is in removing urea from the blood. For the first months or even years of PD treatment, you may still produce small amounts of urine. If your urine output is more than several hundred milliliters per day, urine is also collected during this period to measure its urea concentration.
From the used solution, urine, and blood measurements, your health care team can compute a urea clearance, called Kt/V, and a creatinine clearance rate (adjusted to body surface area). The residual clearance of the kidneys is also considered. These measurements will show whether the PD prescription is adequate.
If the laboratory results show that the dialysis schedule is not removing enough urea and creatinine, the doctor may change the prescription by
* increasing the number of exchanges per day for patients treated with CAPD or per night for patients treated with CCPD or NIPD
* increasing the volume of each exchange (amount of solution in the bag) in CAPD
* adding an extra, automated middle-of-the-night exchange to the CAPD schedule
* adding an extra middle-of-the-day exchange to the CCPD schedule
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One of the big problems with PD is that patients sometimes don't perform all of the exchanges prescribed by their medical team. They either skip exchanges or sometimes skip entire treatment days when using CCPD or NIPD. Skipping PD treatments has been shown to increase the risk of hospitalization and death.
Normally the PD prescription factors in the amount of residual, or remaining, kidney function. Residual kidney function typically falls, although slowly, over months or even years of PD. This means that more often than not, the number of exchanges prescribed, or the volume of exchanges, needs to increase as residual kidney function falls.
The doctor should determine your PD dose on the basis of practice standards established by the National Kidney Foundation Dialysis Outcomes Quality Initiative (NKF- DOQI). Work closely with your health care team to ensure that you get the proper dose, and follow instructions carefully to make sure you get the most out of your dialysis exchanges.
(Adapted from NIDDK)