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Peritoneal dialysis (PD) was first introduced in the 1960s as an alternative to hemodialysis. Both dialysis treatments clean the blood of waste and excess fluid. Hemodialysis requires that blood be removed from the body and cleaned through an artificial kidney called a dialyzer.
With peritoneal dialysis, blood does not have to travel outside of the body. Instead, PD takes advantage of a membrane in the body called the peritoneal membrane. The peritoneum is located in the abdomen. It filters waste and excess fluid with the help of a fluid called dialysate.
PD works by using the peritoneal membrane to filter the waste and fluid from your bloodstream. The peritoneal membrane is a thin membrane that lines the abdomen. It is a semipermeable membrane so it can allow waste and excess fluid to pass. When dialysate is placed in the abdomen, the glucose in the dialysate pulls waste and fluid from the blood vessels that pass through the peritoneum. The glucose also prevents the waste and fluid from passing back through the peritoneum. The scientific principle of diffusion is what allows PD to work. With diffusion, some particles (the toxins) are able to cross the semipermeable membrane of the peritoneum, until the concentration of particles is equal. The glucose in the dialysate helps pull the extra fluid into the peritoneal cavity. Once the concentration is equal, the dialysate is drained externally and fresh dialysate is added to keep attracting the toxins.
In order to perform PD, a catheter must be surgically placed into the abdomen. A catheter is a small, flexible tube that will serve as the gateway for dialysate to enter and exit the body.
Continuous ambulatory peritoneal dialysis (CAPD) is a type of peritoneal dialysis that is done manually. A bag of fresh dialysate is held above or near head level on an IV pole or coat rack. The dialysate will drip flow down through a tube that is connected to the PD catheter. Once the dialysate bag has been emptied, the dialysate will sit in the abdomen for a specified time, usually between 4 to 8 hours. This is called dwell time. Once your dwell time is over, the dialysate is drained from your abdomen to an empty bag and fresh dialysate is introduced. This drain, fill, dwell procedure is called an exchange. Generally, an exchange takes about 5 to 10 minutes to fill and 15 to 20 minutes to drain.
Automated peritoneal dialysis uses a machine called a cycler in order to minimize the need for manual exchanges. It allows dialysis to be performed at night while a patient sleeps. Dialysate is warmed by the cycler machine to body temperature and then fills the abdomen while the patient is lying in bed. Dwell time can be programmed into the cycler. When dwell time is complete, the used dialysate is drained and replaced. The cycler is programmed to fill and drain the abdomen automatically at night. It performs several exchanges while the patient sleeps with one exchange done in the morning before unhooking from the machine. This process is called continuous cycling peritoneal dialysis (CCPD). Nighttime intermittent peritoneal dialysis (NIPD) is similar to CCPD, except the peritoneum is left empty during non-treatment hours.
Peritoneal dialysis must be performed every day. The doctor determines how many exchanges should be performed, as well as the dwell time based on the patient’s needs. For people using automated peritoneal dialysis, their cycler will be programmed with a specific number of exchanges. Upon rising, those on CCPD will disconnect from the cycler and are free for the day.
Peritoneal dialysis requires training to be performed correctly. The PD training nurse teaches the patient and/or a partner how to perform PD safely at home, at the office for those who work or other clean environments. PD training usually takes about two weeks until people are comfortable with the procedure.
In addition to teaching how to perform manual exchanges and use the cycler, the renal nurse and health care team will provide a list of supplies that will help make PD comfortable and safe. Because PD is done at home, there needs to be an area available in the home to store supplies that are needed to do exchanges.
An ample supply of dialysate needs to be on hand. The doctor will prescribe the appropriate composition of dialysate for the patient. Those performing manual PD will receive a heating pad may to warm the dialysate to their body temperature.
Other supplies needed may include face masks and antibacterial hand cleaner to help prevent infection.
Peritoneal dialysis, like any other dialysis treatment, is extremely effective when the patient follows the treatment plan. The doctor and the health care team work with the individual patient to design a treatment program to manage the kidney disease as well as any underlying conditions the patient may have. PD may be just one aspect of the treatment; the doctor may recommend a special diet and prescribed medicines in addition to PD treatments. If a patient does not follow the entire course of the treatment plan, PD treatments may not be as effective as they can be.
Skipping or cutting back on the number of exchanges, or making dwell time shorter, is not recommended. Waste, which would normally be removed during exchanges, can build up in the bloodstream causing the patient to feel ill when the PD treatment plan is not followed as directed.
The doctor will run several tests on the patient to see how well the treatment is working. One of these tests is called the peritoneal equilibrium test (PET). PET measures how much glucose and waste products such as urea and creatinine are drawn into the dialysate solution after a four-hour dwell time. PET will also measure the amount of glucose remaining in the dialysate. If the glucose levels are low, this means the body may be absorbing too much glucose during dwell time.
The doctor will also order the home training nurse to perform a clearance test also known as Kt/V. Samples of used dialysate are collected over a 24-hour period and the doctor will also request a blood sample. The doctor will then compare the amount of waste in the used dialysate and the amount of waste that is in the blood sample. The doctor may also ask for a urine sample, for those who still produce urine. Using this data, the doctor can calculate Kt/V. This test will determine how well the treatment program is working by measuring the amount of waste (also called urea) removed from the bloodstream as well as the amount of fluid.
In addition to testing, the patient can also help the doctor by telling about any changes experienced. If a patient is feeling ill, the doctor may determine that the dialysis treatment needs adjusting. The adjustment could mean a change in dialysate composition to one with a different glucose level, scheduling more exchanges or longer dwell times or making adjustments to any medicines being taken.
The most common side effects of PD are weight gain, bloating and there is a risk of infection. However, PD is well-tolerated by most people and serious side effects are uncommon.
One of the ingredients in dialysate is a sugar called glucose. During dwell time, the peritoneum can allow glucose to pass to the blood vessels where it is absorbed into the body. Since glucose is a sugar, weight gain and a rise in sugar levels may occur. Careful dialysis prescription management, in addition to proper attention to diet and fluid intake, usually minimize these concerns.
Some patients will be asked to carry fluid in their abdomen during the day. There may be bloating in the abdominal area. This may sometimes cause the abdomen to appear distended and cause a sensation of bloating. Some people may experience abdominal discomfort; if there is any feeling of being uncomfortable, this should be discussed with the doctor.
Special precautions need to be taken against infection. The PD catheter is a potential passageway through which germs can enter the body. The skin surrounding the catheter site is also at risk for infection. Patients will be taught by their health care team how to care for their catheter, as well as how to limit exposure to infection. Washing hands before and after handling the catheter and using a local antibiotic cream reduces the risk of infections. Wearing a face mask will prevent germs from the nose and mouth from having contact with the catheter. The skin surrounding the catheter should be inspected daily for any signs of infection. There are also activities that may increase chances of infection, such as swimming or soaking in a tub. The health care team will provide information about how to avoid infection around the catheter and in the body.
Many people choose peritoneal dialysis because it fits well into their lifestyles and provides more control over their treatment program. Because it provides continuous therapy, it is more like your natural kidneys. PD is highly effective when the treatment schedule is followed along with other recommendations from the doctor and health care team regarding diet and medicines.
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