Dialysis is the procedure of removing waste products, excess water and balancing the electrolyte levels of the blood in the manner that the kidney would do. It is necessary for patients with kidney disorders – either acute disorders where kidney functioning is impaired but will be restored with treatment (short term) and time or in those patients with chronic kidney disease where only a kidney transplant will restore normal functioning (long term). Dialysis is a life-saving technique to filter the blood but cannot restore complete health to the patient. There are two methods for dialysis – hemodialysis or peritoneal dialysis.
What is Hemodialysis?
In hemodialysis, the blood is passed, a little at a time, through a special filter, which removes waste products and excess fluid. The purified blood is then returned to the body. A strict schedule consisting of sessions of 3 to 5 hours, on alternate days, 3 days a week is usually followed. This is known as conventional hemodialysis.
Daily hemodialysis may be done with shorter sessions each day. With home dialysis, a more flexible schedule can be followed but regularity must be maintained.
Preparation for Hemodialysis
The first step is to prepare a vascular access – this means entry to the blood vessels. This is the site on the body from which the blood is removed and returned during dialysis. This may be done by the surgeon a few weeks or even several months before the dialysis is to be started so that the vascular access has time to heal before starting the dialysis. The vascular access should allow continuous high volumes of blood flow so that maximum amount of blood can be treated during the procedure.
For hemodialysis, the 3 basic types of vascular access are necessary :
- Arteriovenous (AV) fistula
- A fistula is a connection between two body parts that are normally separate.
- An AV fistula is surgically created between an artery and a vein, usually in the forearm. As a result, more blood flows into the vein, causing it to become wider and stronger, thus allowing easy access to the blood stream.
- This is the preferred type of vascular access since it lasts for a long time, allows good blood flow, and has less complications than other types of access.
- Arteriovenous (AV) graft
- When the veins are too small, an AV fistula cannot be created. In this case, an AV graft may be needed.
- A synthetic tube or a graft is inserted under the skin, which is used to connect the artery and vein. This is also known as a synthetic bridge graft.
- There is a greater chance of clotting and infection with this type of access as compared to AV fistula.
- Central venous catheter
- Emergency hemodialysis may be done by introducing a temporary catheter into a large vein in the neck or near the groin.
- The two chambers in the catheter allow two-way flow of blood.
- Needle insertion is not necessary once the catheter is in place.
- This may be used for a few weeks or months till the permanent access is ready.
- Prior to starting the hemodialysis, the vital signs, such as the pulse, blood pressure, and temperature, as well as the body weight are measured.
- With an AV fistula or AV graft, two needles are usually inserted through the vascular access – one to carry blood to the dialyzer and the other to bring back the filtered blood to the body. Specialized needles with two openings for two-way flow of blood are available but they seem to be less efficient and may necessitate longer sessions.
- Each needle is connected to the dialyzer by a flexible tube.
- The dialyzer filters the blood in small amounts. The waste products and excess water passes on to the cleansing fluid, known as the dialysate.
- The cleansed blood returns to the body through the other needle.
- Once hemodialysis is complete, the needles are removed and a pressure dressing is applied to prevent bleeding.
Hemodialysis is a painless procedure, during which time the patient may sit, recline, lie down, or fall off to sleep. Any other sedentary activity may be done, such as reading, watching television, or talking over the phone. After each session, the weight may be recorded again.
Complications of Hemodialysis
- Abdominal cramps
- Fluctuation in heart rate
- Low blood pressure
- Shortness of breath
- Complications of the vascular access, such as infection and clot formation.
What is Peritoneal Dialysis?
In peritoneal dialysis, the peritoneal cavity and lining (peritoneum) is used to filter the blood. Once the cavity is filled with dialysis fluid (dialysate), blood in the vessels of the peritoneum will pass out excess water and wastes into the dialysate in the cavity. The fluid can then be drained out of the peritoneal cavity. Peritoneal dialysis is usually done at home and is only viable for patients with a willing caregiver or who has the physical ability to do it themselves.
Preparation for Peritoneal Dialysis
Before starting dialysis, a catheter is inserted into the abdomen under local or general anesthesia. The catheter, which may be placed on the right or left of the umbilicus, will transfer fluid in and out of the abdominal cavity. The catheter is a soft, flexible, hollow tube, usually made of silicone, with balloon-like cuffs that can be inflated so as to hold the catheter in place once it is inserted. Multiple holes at the end of the catheter allow the fluid to flow in and out.
After inserting the catheter, it is advisable to wait for 10 to 14 days before starting dialysis in order to give the catheter site time to heal. In some cases, dialysis may be started right away. After the catheter is in place, the patient and family members are trained on setting up the home dialysis unit and how to perform the dialysis.
Care of the Catheter Site
Special attention should be given to care of the catheter and the skin around it (catheter site) so as to maintain optimum functioning of the catheter and prevent infection.
- Immediately after insertion, the catheter site is covered with a gauze dressing and tape so as to keep the catheter in place and also prevent infection.
- Dressing change should only be done by a trained staff, under strict sterile conditions.
- The area should be kept dry until it has healed.
- Swimming and taking a bath should be avoided during this period.
- Lifting heavy items is not advisable.
- Constipation should be avoided to prevent development of hernia and problems with catheter function.
- After the catheter site has healed, care should be taken to keep the area clean.
- The skin around the catheter site should be cleaned daily with antiseptic lotion or antibacterial soap and the patted dry with a clean towel.
- An antibiotic cream should be applied around the catheter after each dressing change.
- The site should be covered with sterile gauze and tape.
With proper care, the catheter may remain in place and function effectively for many years. A minor surgical procedure will be required if the catheter needs to be replaced or removed.
Peritoneal Dialysis Procedure
- The peritoneal (abdominal) cavity is filled with dialysis fluid (dialysate) through the catheter. The fluid is allowed to remain within the abdomen for a certain period of time. This is known as a dwell.
- The peritoneal lining of the abdomen acts as a membrane through which waste products and extra fluids pass from the blood stream into the dialysate.
- On completion of the dwell, the dialysate containing waste products and excess fluid from the blood is drained out of the abdomen and discarded. This process is known as an exchange.
- Fresh dialysate is again introduced into the peritoneal cavity and the process may be repeated 4 to 5 times in a day.
- Each cycle may take 30 to 40 minutes when done manually. The exchange can also be done with a machine, known as the cycler.
Types of Peritoneal Dialysis
There are different types of peritoneal dialysis may be of different types and the method chosen may be related to a person’s lifestyle.
- Continuous ambulatory peritoneal dialysis (CAPD) is where several exchanges may be done during the day. There are usually 3 exchanges and an overnight dwell (the dialyser is introduced in the abdomen at night and drained in the morning). The exchange is usually done manually and the patient may walk around with the fluid in the abdomen. Sometimes, a machine called the minicycler will perform the exchange at night with the patient asleep.
- Continuous cycler peritoneal dialysis (CCPD) is where the exchange is done automatically by the machine while the patient sleeps. The daytime dwell is long. CCPD is more common than CAPD in developed countries. Its advantage is that a patient gets more time to attend to other commitments.
Complications of Peritoneal Dialysis
- Infection at catheter site.
- Peritonitis or infection of the peritoneal cavity. Peritonitis should be treated aggressively since it is potentially life-threatening.
- Weight gain
Article reviewed by Dr. Greg. Last updated on December 3, 2011