Our blood vessels are not well suited to providing a sufficient and constant blood flow for dialysis. We have two types of blood vessels: veins and arteries. Our veins are located just beneath the skin and we can often see them with the naked eye. They can be punctured quite easily, but the blood flow in veins is too low for dialysis treatment. In the arteries, blood flows with a higher pressure than in the veins, but they are БhiddenБ much deeper under the skin, and are hence much more difficult to puncture. Furthermore, arteries have a very strong pulse and high pressure, which is not ideal for dialysis treatment. Therefore we need a special blood vessel called fistula. A fistula is created during a short surgical intervention by joining an artery with a vein Б that is why it is called БarteriovenousБ. Fistulas are usually located in the forearm. The newly created blood vessel combines the properties of arteries and veins: the blood flow and blood pressure is higher than in a vein and the blood vessel has a palpable thrill, similar to what you can feel when touching an artery.
During the maturation process the diameter of the blood vessel grows making it easier to insert a needle, and the wall thickness of the fistula increases. This Бmaturation processБ usually takes two to six weeks. After maturation the fistula can be cannulated, as it allows a high amount of blood to flow into the extracorporeal blood circuit, enabling effective haemodialysis.
Treatment for hemodialysis usually takes place in a hemodialysis unit. This is a special building that is equipped with machines that perform the dialysis treatment. The dialysis unit is also the place where patients can receive dietary counseling and help with social needs. Patients generally go to the dialysis unit three times a week for treatment. For example, the schedule is either Monday, Wednesday, and Friday or Tuesday, Thursday, and Saturday. Before treatment, patients weigh themselves so that excess fluid accumulated since the last dialysis session can be measured. Patients then go to assigned chairs that are like lounge chairs.
The area of the graft or fistula (the connection between the artery and vein), is cleaned thoroughly. Two needles are then inserted into the graft or fistula. One takes the blood to the machine where it is cleaned. The other needle allows blood that is returning to the patient to go back into the patient s body. Treatments last from 2 to 4 hours. During this time, the dialysis staff checks the patient s frequently and adjusts the dialysis machine to ensure that the proper amount of fluid is being removed from the patients body. Patients can read, watch television, or do other work during treatment. On occasion, patients who are very motivated may be able to perform dialysis themselves at home in a process called home hemodialysis. Peritoneal dialysis requires the patient to play a more active role in their dialysis treatment. Of primary importance is the patient s responsibility for maintaining a clean surface on the abdomen and catheter, where treatment is administered, in order to prevent infection.
During this process, the patient weighs herself/himself to determine the strength of fluid to be used. The patient then puts on a mask and cleans the peritoneal catheter site. Fluid that has been allowed to stay in the peritoneal cavity while the peritoneal membrane filters waste into the fluid. The fluid and waste are is then drained back into the plastic bag that originally contained the fluid. The patient then disconnects this bag containing waste in the fluid and connects a new bag of solution that is allowed to drain into the peritoneal cavity. Once the fluid is in the body, the new bag is rolled up and placed in the patient s underwear until the next treatment. This procedure usually takes 30 minutes to accomplish and must be done four to five times a day. As an alternative to this treatment, some patients on peritoneal dialysis use a machine called a cycler. This cycler is used every night. Five to six bags of dialysis fluid are used on the cycler and the machine automatically changes the fluid while the patient sleeps.