xx%20Peritoneal%20Dialysis%20Dose%20and%20Adequacy -...

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and Adequacy W hen kidneys fail, waste products such as urea and creatinine build up in the blood. One way to remove these wastes is a process called peritoneal dialysis (PD). The walls of the abdominal cavity are lined with a membrane called the peritoneum. During PD, a mixture of dextrose (sugar), salt, and other miner- als dissolved in water, called dialysis solution, is placed in a person’s abdomi- nal cavity through a catheter. The body’s peritoneal membrane enclosing the digestive organs allows waste prod- ucts and extra body fluid to pass from the blood into the dialysis solution. These wastes then leave the body when the used solution is drained from the abdomen. Each cycle of draining and refilling is called an exchange. The time the solution remains in the abdomen between exchanges is called the dwell time. During this dwell time, some of the dextrose in the solution crosses the membrane and is absorbed by the body. Many factors affect how much waste and extra fluid are removed from the blood. Some factors—such as the patient’s size and the permeability, or speed of diffusion, of the peritoneum— cannot be controlled. Dialysis solution comes in 1.5-, 2-, 2.5-, or 3-liter bags. The dialysis dose can be increased by using a larger bag, but only within the limits of the person’s abdominal capaci- ty. Everyone’s peritoneum filters wastes at a different rate. In some people, the peritoneum does not allow wastes to enter the dialysis solution efficiently enough to make PD feasible. Other factors that determine how effi- ciently a person’s blood is filtered can be controlled. Controllable factors include the number of daily exchanges and the dwell times. When fresh solu- tion is first placed in the abdomen, it draws in wastes rapidly. As the solution becomes more nearly saturated with wastes, it cleans the blood less efficient- ly. For example, a patient may perform one exchange with a 6-hour dwell time, during which the solution becomes nearly saturated with urea. But in the second half of that dwell time, urea is being removed from the blood very slowly. If the patient performed two exchanges with 3-hour dwell times instead, the amount of urea removed would be substantially greater than that removed in one 6-hour dwell time. Another way to increase the amount of fluid and waste drawn into the peri- toneal cavity is to use dialysis solution with a higher concentration of dextrose. A higher dextrose concentration moves fluid and more wastes into the abdomi- nal cavity, increasing both early and long-dwell exchange efficiency. Eventu- ally, however, the body absorbs dextrose from the solution. As the concentration of dextrose in the body comes closer to that in the solution, dialysis becomes less effective, and fluid is slowly absorbed from the abdominal cavity. National Institute of Diabetes and Digestive and Kidney Diseases
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This note was uploaded on 10/04/2009 for the course NTR 371 taught by Professor Southworth during the Spring '09 term at University of Texas.

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xx%20Peritoneal%20Dialysis%20Dose%20and%20Adequacy -...

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