| Homepage | Imprint |
|
||
 |
Dialysis
In medicine, renal dialysis is a method for removing waste such as ureafrom the bloodwhen the kidneysare incapable of this (i.e. in renal failure).
Initiation of DialysisIn acute renal failure, (renal) dialysis is generally initiated when the renal functionhas deteriorated to an extent that it is threatening the body's physiology. Volume overload (i.e. hypervolemia) that is unresponsive to strong diuretics, such as furosemide, and severe hyperkalemiaare two common indications for dialysis. In chronic renal failurethe problem is usually longstanding, and the decision is based on the level of kidney function (GFRor creatinine clearance), possibility of a renal transplantand complications of the malfunctioning kidney (e.g. hyperkalemia, uremia). Chronic renal failure that does not have an acute (i.e. reversible) component and requires dialysis is called end-stage renal disease (ESRD). There is no general agreement among nephrologistson when to start dialysis.[{{fullurl:Template:FULLPAGENAME}}#endnote_Tattersall] In Canadasome nephrologists advocate that patients with CRF should start dialysis when the GFRis below 15 mL/min and below 20 mL/min for patients with diabetes mellitus. Canadian guidelines suggest considering dialysis when the GFR is less than 12 mL/min.[{{fullurl:Template:FULLPAGENAME}}#endnote_Churchill] In the United States, dialysis is initated at a GFR of 15 mL/min in diabetics and 10mL/min in non-diabetics, in conjuction with uremic sypmtoms. Most guidelines agree that dialysis should be started before the GFR drops below 6 mL/min.[{{fullurl:Template:FULLPAGENAME}}#endnote_kdigo] The rationale for starting dialysis early is that it prevents illness associated with severe uremiaand may minimize long-term complications associated with kidney failure. Studies have shown that starting dialysis with a lower GFR is associated with a poor nutritional status which is associated with a higher mortality in the first two years of treatment.[{{fullurl:Template:FULLPAGENAME}}#endnote_Churchill] Acute renal failure can present on top of (i.e. in addition to) chronic renal failure. This is called acute-on-chronic renal failure (AoCRF) and may require dialysis temporarily (until the acute component of the renal failure resolves). Types of dialysisImage:Semipermeable membrane.png There are two main types of dialysis, hemodialysis and peritoneal dialysis, and several subtypes.
Measures of dialysis treatment adequacySeveral measures of dialysis adequacy exist. The most widespread is Kt/V, but its utility has been questioned. The hemodialysis product(HDP) has been proposed as an alternative. Urea reduction ratio(URR) is another measure of dialysis adequacy. It has also been suggested that a 'holistic attitude', which takes overall patient wellbeing should be taken into account rather than mere numbers. The measurement of treatment adequacy is an unresolved issue.[{{fullurl:Template:FULLPAGENAME}}#endnote_Oreopoulos] None of the commonly used dialysis treatment adequacy measures accurately models the mass transferphenomena that underlie the physicsof dialysis. HemodialysisImage:Artificialkidney.jpg
The principle of hemodialysis(UK: haemodialysis) is somewhat different. It works by having the blood flow along one side of a semipermeable membrane, with the dialysis solution flowing along the other side, usually in the opposite direction in a countercurrent exchangesystem. Due to the difference in osmolaritybetween the two solutions, solutes diffuse across the membrane along their concentration gradient. A difference in pressure drives water across the membrane, which also pulls along some solutes (solvent drag). Peritoneal dialysis
There are three types of peritoneal dialysis. Continuous ambulatory peritoneal dialysis (CAPD), the most common type, needs no machine and can be done at home. Continuous cyclic peritoneal dialysis (CCPD) uses a machine and is usually performed at night when the person is sleeping. Intermittent peritoneal dialysis (IPD) uses the same type of machine as CCPD, but is usually done in the hospital because treatment takes longer. Prior to any peritoneal dialysis, a catheteris placed in the patient's abdomen, running from the peritoneum out to the surface, near the navel. This is done as a short surgery. Side-effects and complicationsIntermittent dialysis is associated with a steep drop in blood pressure, and dialysis patients are warned not to travel without assistance. The treatment may cause fatigue. All forms of dialysis require access to either the circulatory system or the peritoneum. As this access breaks normal skin barriers, and as people with renal failure generally have a suppressed immune system, infectionis a relatively common problem, which may require antibioticsand supportive care. Infection rates are much higher with catheter patients than patients with AV fistulas or grafts, and the use of catheters is therefore discouraged. Similarly, hemorrhagefrom the access system is a risk; this is especially so in the hours after dialysis, when heparin(which is used in dialysis) may impair blood clotting. First Use Syndrome is a severe anaphylactic reactionto the dialyzer. Its symptoms include sneezing, wheezing, shortness of breath, back pain, chest pain, or sudden death. It can be caused by residual sterilant in the dialyzer or the material of the membrane itself. In recent years, the incidence of First Use Syndrome has fallen off, due to an increased use of gamma raysterilizationinstead of chemical sterilants, and the development of new dialyzer membranes of higher biocompatibility. Economics of Dialysis in the United StatesDialysis is very expensive, averaging over $63,000 per year for each patient [{{fullurl:Template:FULLPAGENAME}}#endnote_usrds]. In the United States, outpatient dialysis is paid for primarily by the government, through the Medicareand Medicaidprograms. Medicare alone currently spends over $18.1 billion (2003) on dialysis patients annually, or 6.7% of its total budget [{{fullurl:Template:FULLPAGENAME}}#endnote_usrds]. Commercial insurance (private insurance companies) also pays for some patients, typically paying providers more than twice the amount as Medicare. Though in most cases, only those over 65 years of age are eligible for Medicare, patients of any age who have ESRD(End Stage Renal Disease), meaning they require dialysis, are eligible as a special exception. Individuals who do not have the employment history required for Medicare eligibility are usually covered by the Medicaid program, which varies from state to state. A large portion of the cost associated with dialysis is the drug erythropoietin, also known as Epogen or EPO. It is given intravenously during the dialysis procedure, and replaces the hormonenormally secreted by the healthy kidney, stimulating the bone marrowto produce red blood cells. Though it is necessary to prevent possibly fatal progressive anemia, it is also extremely costly. A single dose of 10,000 units costs around $100. This would be given 3 times a week, and assuming a patient did not miss a dose, would cost over $15,000 a year. Medicare spent $1.6 billion on EPO alone in 2003, or, by comparison, about the same as the entire budget of the FDA. The vast majority of US outpatient dialysis clinics are owned and operated by one of a small number of large dialysis corporations, or the "chains," as they are known in the industry. As of 2005, there are two main "chains": Fresenius Medical Careand DaVita. The two other largest dialysis corporations, Renal Care Groupand Gambro Healthcare US, were acquired by Fresenius and DaVita, respectively, in 2005. References
External links
es:Rińón artificial fa:?????? fr:Dialyse nl:Kunstnier ja:???? no:Dialyse pl:Dializa pt:Diálise sk:Dialýza (lekárstvo) sv:Dialys Categories: Nephrology| Medical treatments
|
