Dialysis
Basics Dialysis works on the principles of the diffusion of solutes and ultrafiltration of fluid across a semi- permeable membrane. Blood flows by one side of a semi-permeable membrane, and a dialysate, or special dialysis fluid, flows by the opposite side. A semipermeable membrane is a thin layer of material that contains pores of various sizes, or pores. Smaller solutes and fluid pass through the membrane, but the membrane blocks the passage of larger substances.
Hemodialysis Removes wastes and water by circulating blood outside the body through an external filter called a dialyzer, that contains a semipermeable membrane. The dialyzer is composed of thousands of tiny synthetic hollow or parallel membrane plates suspended in dialysate. The fibers or plates function as a semipermeable membrane where blood flows through the fibers, dialysis solution flows around the outside of the fibers, and water and wastes move between these two solutions. Concentration gradient – Concentration of undesired solutes is high in the blood, but low in the dialysate. Pressure gradient- Ultrafiltration occurs by increasing the hydrostatic pressure across the dialyzer membrane by applying a negative pressure to the dialysate compartment of the dialyzer. This pressure gradient allows the removal of several liters of excess fluid during a typical 3- to 5-hour treatment. Higher than normal bicarb, K and Ca in conc similar to normal blood,
Peritoneal Dialysis The dialysate is run through a tube into the peritoneal cavity, is left there for a period of time to absorb waste products, and then it is drained out through the tube and discarded. The peritoneum is a layer of tissue containing blood vessels that lines and surrounds the peritoneal cavity and the internal abdominal organs. Wastes and excess water diffuse from the blood, across the peritoneum, and into dialysate, which has a composition similar to the fluid portion of normal blood. Ultrafiltration occurs via osmosis; the dialysis solution used contains a high concentration of glucose, and the resulting osmotic pressure causes fluid to move from the blood into the dialysate The exchange is normally repeated 4-5 times during the day or more often overnight with an automated system.
Hemodialysis Peritoneal dialysis Advantages It is most often done by trained health professionals who can watch for any problems. It allows you to be in contact with other people having dialysis, which may give you emotional support. You don't have to do it yourself, as you do with peritoneal dialysis. You do it for a shorter amount of time and on fewer days each week than peritoneal dialysis. It gives you more freedom than hemodialysis. It can be done at home or in any clean place. You can do it when you travel. You may be able to do it while you sleep. You can do it by yourself. It doesn't require as many food and fluid restrictions as hemodialysis, and it does not use needles. It doesn't require the use of blood thinners, so it may be a better choice if you have bleeding problems or take medicines that interfere with blood clotting. Disadvantages It causes you to feel tired on the day of the treatments. It can cause problems such as low blood pressure and blood clots in the dialysis access. It increases your risk of bloodstream infections. It requires the use of blood thinners during the procedure, so it may not be the best choice if you have bleeding problems or take medicines that interfere with blood clotting. The procedure may be hard for some people to do. It increases your risk for an infection of the lining of the belly, called peritonitis.
References http://www.uptodate.com/contents/overview-of- the-hemodialysis-apparatus http://www.emedicinehealth.com/hemodialysis_co mpared_to_peritoneal_dialysis- health/article_em.htm http://en.wikipedia.org/wiki/Dialysis http://www.uptodate.com/contents/patient- information-peritoneal-dialysis-beyond-the-basics