Dialysis, Kidney (Encyclopedia of Medicine)
Dialysis treatment replaces the function of the kidneys, which normally serve as the body's natural filtration system. Through the use of a blood filter and a chemical solution known as dialysate, the treatment removes waste products and excess fluids from the bloodstream, while maintaining the proper chemical balance of the blood. There are two types of dialysis treatment : hemodialysis and peritoneal dialysis.
Dialysis can be used in the treatment of patients suffering from poisoning or overdose, in order to quickly remove drugs from the bloodstream. Its most prevalent application, however, is for patients with temporary or permanent kidney failure. For patients with end-stage renal disease (ESRD), whose kidneys are no longer capable of adequately removing fluids and wastes from their body or
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Dialysis (Encyclopedia of Science)
Dialysis is a process by which small molecules in a solution are separated from large molecules. Dialysis has a number of important commercial and industrial applications and plays a crucial role in maintaining the health of humans. For some people, in fact, the term dialysis refers to a specific kind of medical treatment in which a machine (the dialysis machine) takes on the functions of a human kidney. Dialysis machines have made possible the survival of thousands of people who would otherwise have died as a result of kidney failure.
Dialysis is a specific example of a more general process known as diffusion. Diffusion was first described by Scottish chemist Thomas Graham (1805869) around 1861. Graham studied the movement of molecules of different sizes through a semipermeable membrane. (A semipermeable membrane is a thin sheet of material that allows some substances to pass throughr diffuseut not others.) Many tissues in the human body are semipermeable membranes. Graham discovered that some substances, such as the sodium and chloride ions of which ordinary table salt is composed, diffuse through a semipermeable membrane up to 50 times as fast as other substances, such as ordinary table sugar.
Today we know the reason behind Graham's observation. Semipermeable membranes are not actually solid sheets of material. Instead, they contain tiny holes too small to be seen by the...
(The entire section is 726 words.)
Dialysis, Kidney (Encyclopedia of Nursing & Allied Health)
Dialysis treatment replaces the function of the kidneys, which normally serve as the body's natural filtration system. Through the use of a blood filter and a chemical solution known as dialysate, dialysis removes waste products and excess fluids from the bloodstream, while maintaining the proper chemical balance of the blood. There are two types of dialysis treatment: hemodialysis and peritoneal dialysis.
Dialysis also can be used to remove overdosed drugs or poisons from the bloodstream more quickly than normally functioning kidneys. Its most prevalent application, however, is for patients with temporary or permanent kidney failure. For patients with end-stage renal disease (ESRD), dialysis is the only renal replacement
therapy available other than kidney transplantation. In the United States, nearly 250,000 patients receive regular dialysis treatments to manage ESRD.
Blood pressure changes during hemodialysis may pose a risk for patients with heart disease. Peritoneal dialysis may be the preferred treatment option for these patients. Peritoneal dialysis is not recommended for patients with abdominal adhesions or other abdominal defects, such as a hernia, which might compromise the efficiency of the treatment. It is also not recommended for patients who suffer frequent bouts of diverticulitis (inflammation of diverticuli, small pouches in the colon).
There are two types of dialysis treatment: hemodialysis and peritoneal dialysis.
Hemodialysis is the most frequently prescribed type of dialysis in the United States. The treatment involves circulating the patient's blood outside of the body through an extracorporeal circuit (ECC), or dialysis circuit. Two needles are inserted into the patient's vein, or access site, and are attached to the ECC, which consists of plastic blood tubing, a filter known as a dialyzer (artificial kidney), and a dialysis machine that monitors and maintains blood flow and administers dialysate. Dialysate is a chemical bath that is used to draw waste products out of the blood.
Since the 1980s, the majority of hemodialysis treatments in the United States have been performed with hollow fiber dialyzers. A hollow fiber dialyzer is composed of thousands of tube-like hollow fiber strands encased in a clear plastic cylinder several inches in diameter. There are two compartments within the dialyzer (the blood compartment and the dialysate compartment). The membrane that separates these two compartments is semipermeable; it allows the passage of certain sized molecules across it, but prevents the passage of other, larger molecules. As blood is pushed through the blood compartment in one direction, suction or vacuum pressure pulls the dialysate through the dialysate compartment in a counter-current, or opposite direction. These opposing pressures work to drain excess fluids out of the bloodstream and into the dialysate, a process called ultrafiltration.
A second process, called diffusion, moves waste products in the blood across the membrane into the dialysate compartment, where they are carried out of the body. At the same time, electrolytes and other chemicals in the dialysate solution cross the membrane into the blood compartment. The purified, chemically balanced blood is then returned to the body.
Most hemodialysis patients require treatment three times a week, for an average of three to four hours per dialysis "run." Specific treatment schedules depend on the type of dialyzer used and the patient's current physical condition. While the treatment prescription and regimen is usually overseen by a nephrologist (a doctor that specializes in the kidney), dialysis treatments are typically administered by a nurse or dialysis technician in out-patient clinics known as dialysis centers or in hospital-based dialysis units. In-home hemodialysis treatment is also an option for some patients, although access to this type of treatment may be limited by financial and lifestyle factors. An investment in equipment is required and another person in the household should be available for support and assistance with treatments.
In peritoneal dialysis, the patient's peritoneum (lining of the abdomen) acts as a blood filter. A catheter is surgically inserted into the patient's abdomen. During treatment, the catheter is used to fill the abdominal cavity with dialysate. Waste products and excess fluids move from the patient's bloodstream into the dialysate solution. After a waiting period of six to 24 hours, depending on the treatment method used, the waste-filled dialysate is drained from the abdomen and replaced with clean dialysate.
There are three types of peritoneal dialysis:
- Continuous ambulatory peritoneal dialysis (CAPD). This treatment is self-administered and requires no machine. The patient inserts fresh dialysate solution into the abdominal cavity, waits four to six hours, and removes the used solution. The solution is immediately replaced with fresh dialysate. A bag attached to the catheter is worn under clothing.
- Continuous cyclic peritoneal dialysis (CCPD). An overnight treatment that uses a machine to drain and refill the abdominal cavity, CCPD takes 102 hours per session.
- Intermittent peritoneal dialysis (IPD). This hospital-based treatment is performed several times a week. A machine administers and drains the dialysate solution, and sessions can take up to 24 hours.
Peritoneal dialysis is often the treatment option of choice for infants and children, whose small size can make vascular access difficult to maintain. Peritoneal dialysis also may be performed outside of a clinical setting, which is more conducive to regular school attendance.
A dialysis technologist, nurse, or nursing assistant weighs patients immediately before and after each hemodialysis treatment to assess their fluid balance. The dialysis technologist, nurse, or nursing assistant also measures and records blood pressure and temperature and assesses patients for any physical changes since their last dialysis run. Regular blood tests, performed by laboratory technologists, monitor chemical and waste levels in the blood. Prior to treatment, patients are typically administered a dose of heparin (an anticoagulant that prevents blood clotting) to ensure the free flow of blood through the dialyzer and an uninterrupted dialysis run.
Both hemodialysis and peritoneal dialysis patients must be vigilant about keeping their access sites and catheters clean and infection-free during and between dialysis runs.
Dialysis is just one facet of a comprehensive treatment approach for ESRD. Although dialysis treatment is very effective in removing toxins and fluids from the body, there are several functions of the kidney it cannot mimic, such as regulating high blood pressure and red blood cell production. Patients with ESRD need to watch their diet and fluid intake carefully and adhere to prescribed medications to effectively manage their disease.
Many of the risks and side effects associated with dialysis are a combined result of both the treatment and the poor physical condition of the ESRD patient. Dialysis patients should be instructed to report side effects to their healthcare provider.
Hematocrit (Hct) levels, the percentage of whole blood comprised of red blood cells, are typically low in ESRD patients. This deficiency is caused by a lack of the hormone erythropoietin, which is normally produced by the kidneys. The problem is exacerbated in hemodialysis patients, who may incur blood loss during hemodialysis
Access sitehe vein tapped for vascular access in hemodialysis treatments. For patients with temporary treatment needs, access to the bloodstream is gained by inserting a catheter into the subclavian vein. Patients in long-term dialysis require stronger, more durable access sites, called fistulas or grafts, that are surgically-created.
Dialysate chemical bath used in dialysis to draw fluids and toxins out of the bloodstream and supply electrolytes and other chemicals to the bloodstream.
Dialysis prescriptionhe general parameters of dialysis treatment that vary according to each patient's individual needs. Treatment length, type of dialyzer and dialysate used, and rate of ultrafiltration are all part of the dialysis prescription.
Dialyzern artificial kidney usually composed of hollow fiber that is used in hemodialysis to eliminate waste products from the blood and remove excess fluids from the bloodstream.
Erythropoietin hormone produced by the kidneys that stimulates the production of red blood cells by bone marrow.
ESRDnd-stage renal disease; chronic or permanent kidney failure.
Extracorporeal circuit (ECC)he path the hemodialysis patient's blood takes outside of the body. It typically consists of plastic tubing, a hemodialysis machine, and a dialyzer.
Hematocrit (Hct) level measure of red blood cells.
Peritoneumhe abdominal cavity; the peritoneum acts as a blood filter in peritoneal dialysis.
treatments. Epoetin alfa, a hormone therapy also known as EPO (sold under the trade name Epogen), and intravenous or oral iron supplements are used to manage anemia in dialysis patients.
Cramps, nausea, vomiting, and headaches
Some hemodialysis patients experience cramps and flu-like symptoms during treatment. These may be caused by a number of factors, including the type of dialysate used, composition of the dialyzer membrane, water quality in the dialysis unit, and the ultrafiltration rate of the treatment. Adjustment of the dialysis prescription often helps alleviate symptoms.
Because of the stress placed on the cardiovascular system with regular hemodialysis treatments, patients are at risk for hypotension, a sudden drop in blood pressure. This can often be controlled by medication and adjustment of the patients' dialysis prescription.
Both hemodialysis and peritoneal dialysis patients are at risk for infection. Hemodialysis patients should keep their access sites clean and watch for signs of redness and warmth that could indicate infection. Peritoneal dialysis patients must follow the same precautions with their catheters in order to prevent peritonitis. Peritonitis, an infection of the peritoneum, causes flu-like symptoms and can disrupt dialysis treatments if not detected promptly.
Because there is a great deal of blood exposure involved in dialysis treatment, a slight risk of contracting hepatitis B and hepatitis C exists. The hepatitis B vaccination is recommended for most hemodialysis patients. As of 1997, there has only been one documented case of HIV being transmitted in a United States dialysis unit to a staff member, and no documented cases of HIV ever being transmitted between dialysis patients in the United States. The strict standards of infection control practiced in modern hemodialysis units makes the chance of contracting one of these diseases very small.
Fluid retention may be relieved after dialysis treatment. The patient's overall sense of physical well being may also be improved. Because dialysis is an ongoing treatment process for many patients, a baseline for normalcy can be difficult to gauge.
Health care team roles
Patients receiving dialysis treatments are cared for by a team that includes nephrologists, dialysis technicians, nurses, radiology technicians, and laboratory technicians. Registered dietitians, nutritionists, and nurses instruct patients about dietary changes to manage their disease.
Cameron, J. S. Kidney Failure: The Facts. New York, NY: Oxford Univ. Press, 1996.
The Washington Manual of Medical Therapeutics. 30th ed. Philadelphia: Lippincott Williams & Wilkins, 2001.
American Association of Kidney Patients (AAKP). 100 S. Ashley Drive, Suite 280, Tampa, FL 33602. (800)749-2257. <<a href="http://www.aakp.org">http://www.aakp.org>.
American Kidney Fund (AKF). Suite 1010, 6110 Executive Boulevard, Rockville, MD 20852. (800)638-8299. <<a href="http://www.arbon.com/kidney">http://www.arbon.com/kidney>.
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Natcher Building, 6AS-13K, 45 Center Drive, Bethesda, MD 20892-6600. <<a href="http://www.niddk.nih.gov">http://www.niddk.nih.gov>.
National Kidney Foundation (NKF). 30 East 33rd Street, New York, NY 10016. (800)622-9020. <<a href="http://www.kidney.org">http://www.kidney.org>.
United States Renal Data System (USRDS). USRDS Coordinating Center, 315 W. Huron, Suite 240, Ann Arbor, MI 48103. (313)998-6611. <<a href="http://www.med.umich.edu/usrds">http://www.med.umich.edu/usrds>.