Hemodialysis
Hemodialysis | |
---|---|
Other names | kidney dialysis |
Specialty | nephrology |
Hemodialysis,
Hemodialysis can be an
Medical uses
Hemodialysis is the choice of renal replacement therapy for patients who need dialysis acutely, and for many patients as maintenance therapy. It provides excellent, rapid clearance of solutes.[2]
A
Adverse effects
Disadvantages
- Restricts independence, as people undergoing this procedure cannot travel around because of supplies' availability
- Requires more supplies such as high water quality and electricity
- Requires reliable technology like dialysis machines
- The procedure is complicated and requires that care givers have more knowledge
- Requires time to set up and clean dialysis machines, and expense with machines and associated staff[2]
Complications
Fluid shifts
Hemodialysis often involves fluid removal (through
Since hemodialysis requires access to the circulatory system, patients undergoing hemodialysis may expose their circulatory system to
Venous needle dislodgement
Venous needle dislodgement (VND) is a fatal complication of hemodialysis where the patient experiences rapid blood loss due to a faltering attachment of the needle to the venous access point.[3]
Unfractioned heparin (UHF) is the most commonly used anticoagulant in hemodialysis, as it is generally well tolerated and can be quickly reversed with protamine sulfate. Low-molecular weight heparin (LMWH) is however, becoming increasingly popular and is now the norm in western Europe.[4] Compared to UHF, LMWH has the advantage of an easier mode of administration and reduced bleeding but the effect cannot be easily reversed.[5] Heparin can infrequently cause a low platelet count due to a reaction called heparin-induced thrombocytopenia (HIT). The risk of HIT is lower with LMWH compared to UHF. In such patients, alternative anticoagulants may be used. Even though HIT causes a low platelet count it can paradoxically predispose thrombosis.[6] When comparing UHF to LMWH for the risk of adverse effects, the evidence is uncertain as to which treatment approach to thin blood has the least side effects and what is the ideal treatment strategy for preventing blood clots during hemodialysis.[7] In patients at high risk of bleeding, dialysis can be done without anticoagulation.[8]
First-use syndrome
First-use syndrome is a rare but severe
Cardiovascular
Long term complications of hemodialysis include
Vitamin deficiency
Folate deficiency can occur in some patients having hemodialysis.[12]
Electrolyte imbalances
Although a dyalisate fluid, which is a solution containing diluted electrolytes, is employed for the filtration of blood, haemodialysis can cause an electrolyte imbalance. These imbalances can derive from abnormal concentrations of potassium (hypokalemia, hyperkalemia), and sodium (hyponatremia, hypernatremia). These electrolyte imbalances are associated with increased cardiovascular mortality.[13]
Mechanism and technique
The principle of hemodialysis is the same as other methods of
Fluid removal (
The dialysis solution that is used may be a sterilized solution of mineral ions and is called dialysate. Urea and other waste products including potassium, and phosphate diffuse into the dialysis solution. However, concentrations of sodium and chloride are similar to those of normal plasma to prevent loss. Sodium bicarbonate is added in a higher concentration than plasma to correct blood acidity. A small amount of glucose is also commonly used. The concentration of electrolytes in the dialysate is adjusted depending on the patient's status before the dialysis. If a high concentration of sodium is added to the dialysate, the patient can become thirsty and end up accumulating body fluids, which can lead to heart damage. On the contrary, low concentrations of sodium in the dialysate solution have been associated with a low blood pressure and intradialytic weight gain, which are markers of improved outcomes. However, the benefits of using a low concentration of sodium have not been demonstrated yet, since these patients can also develop cramps, intradialytic hypotension and low sodium in serum, which are symptoms associated with a high mortality risk.[14]
Note that this is a different process to the related technique of hemofiltration.
Access
Three primary methods are used to gain access to the blood for hemodialysis: an intravenous catheter, an arteriovenous fistula (AV) and a synthetic graft. The type of access is influenced by factors such as the expected time course of a patient's renal failure and the condition of their vasculature. Patients may have multiple access procedures, usually because an AV fistula or graft is maturing and a catheter is still being used. The placement of a catheter is usually done under light sedation, while fistulas and grafts require an operation.
Types
There are three types of hemodialysis: conventional hemodialysis, daily hemodialysis, and nocturnal hemodialysis. Below is an adaptation and summary from a brochure of The Ottawa Hospital.
Conventional hemodialysis
Conventional hemodialysis is usually done three times per week, for about three to four hours for each treatment (Sometimes five hours for larger patients), during which the patient's blood is drawn out through a tube at a rate of 200–400 mL/min. The tube is connected to a 15, 16, or 17 gauge needle inserted in the dialysis fistula or graft, or connected to one port of a dialysis catheter. The blood is then pumped through the dialyzer, and then the processed blood is pumped back into the patient's bloodstream through another tube (connected to a second needle or port). During the procedure, the patient's blood pressure is closely monitored, and if it becomes low, or the patient develops any other signs of low blood volume such as nausea, the dialysis attendant can administer extra fluid through the machine. During the treatment, the patient's entire blood volume (about 5000 cc) circulates through the machine every 15 minutes. During this process, the dialysis patient is exposed to a week's worth of water for the average person.
Daily hemodialysis
Daily hemodialysis is typically used by those patients who do their own dialysis at home. It is less stressful (more gentle) but does require more frequent access. This is simple with catheters, but more problematic with fistulas or grafts. The "buttonhole technique" can be used for fistulas, but not grafts, requiring frequent access. Daily hemodialysis is usually done for 2 hours six days a week.
Nocturnal hemodialysis
The procedure of nocturnal hemodialysis is similar to conventional hemodialysis except it is performed three to six nights a week and between six and ten hours per session while the patient sleeps.[15]
Equipment
The hemodialysis machine pumps the patient's blood and the dialysate through the dialyzer.
Water system
An extensive
For this reason, water used in hemodialysis is carefully purified before use. A common water purification system includes a multi stage system.
The water is first softened. Next the water is run through a tank containing activated charcoal to
Even this degree of water purification may be insufficient. The trend lately is to pass this final purified water (after mixing with dialysate concentrate) through an ultrafiltration membrane or absolute filter. This provides another layer of protection by removing impurities, especially those of bacterial origin, that may have accumulated in the water after its passage through the original water purification system.
Dialysate
Once purified water is mixed with dialysate (also called dialysis fluid) concentrate consisting of:
Dialyzer
The dialyzer is the piece of equipment that filters the blood. Almost all dialyzers in use today are of the hollow-fiber variety. A cylindrical bundle of hollow fibers, whose walls are composed of semi-permeable membrane, is anchored at each end into potting compound (a sort of glue). This assembly is then put into a clear plastic cylindrical shell with four openings. One opening or blood port at each end of the cylinder communicates with each end of the bundle of hollow fibers. This forms the "blood compartment" of the dialyzer. Two other ports are cut into the side of the cylinder. These communicate with the space around the hollow fibers, the "dialysate compartment." Blood is pumped via the blood ports through this bundle of very thin capillary-like tubes, and the dialysate is pumped through the space surrounding the fibers. Pressure gradients are applied when necessary to move fluid from the blood to the dialysate compartment.
Membrane and flux
Dialyzer membranes come with different pore sizes. Those with smaller pore size are called "low-flux" and those with larger pore sizes are called "high-flux." Some larger molecules, such as beta-2-microglobulin, are not removed at all with low-flux dialyzers; lately, the trend has been to use high-flux dialyzers. However, such dialyzers require newer dialysis machines and high-quality dialysis solution to control the rate of fluid removal properly and to prevent backflow of dialysis solution impurities into the patient through the membrane.
Dialyzer membranes used to be made primarily of cellulose (derived from cotton linter). The surface of such membranes was not very biocompatible, because exposed hydroxyl groups would activate complement in the blood passing by the membrane. Therefore, the basic, "unsubstituted" cellulose membrane was modified. One change was to cover these hydroxyl groups with acetate groups (cellulose acetate); another was to mix in some compounds that would inhibit complement activation at the membrane surface (modified cellulose). The original "unsubstituted cellulose" membranes are no longer in wide use, whereas cellulose acetate and modified cellulose dialyzers are still used. Cellulosic membranes can be made in either low-flux or high-flux configuration, depending on their pore size.
Another group of membranes is made from synthetic materials, using polymers such as polyarylethersulfone, polyamide, polyvinylpyrrolidone, polycarbonate, and polyacrylonitrile. These synthetic membranes activate complement to a lesser degree than unsubstituted cellulose membranes. However, they are in general more hydrophobic which leads to increased adsorption of proteins to the membrane surface which in turn can lead to complement system activation.[20][21] Synthetic membranes can be made in either low- or high-flux configuration, but most are high-flux.
Nanotechnology is being used in some of the most recent high-flux membranes to create a uniform pore size. The goal of high-flux membranes is to pass relatively large molecules such as beta-2-microglobulin (MW 11,600 daltons), but not to pass albumin (MW ~66,400 daltons). Every membrane has pores in a range of sizes. As pore size increases, some high-flux dialyzers begin to let albumin pass out of the blood into the dialysate. This is thought to be undesirable, although one school of thought holds that removing some albumin may be beneficial in terms of removing protein-bound uremic toxins.
Membrane flux and outcome
Whether using a high-flux dialyzer improves patient outcomes is somewhat controversial, but several important studies have suggested that it has clinical benefits. The NIH-funded HEMO trial compared survival and hospitalizations in patients randomized to dialysis with either low-flux or high-flux membranes. Although the primary outcome (all-cause mortality) did not reach statistical significance in the group randomized to use high-flux membranes, several secondary outcomes were better in the high-flux group.[22][23] A recent Cochrane analysis concluded that benefit of membrane choice on outcomes has not yet been demonstrated.[24] A collaborative randomized trial from Europe, the MPO (Membrane Permeabilities Outcomes) study,[25] comparing mortality in patients just starting dialysis using either high-flux or low-flux membranes, found a nonsignificant trend to improved survival in those using high-flux membranes, and a survival benefit in patients with lower serum albumin levels or in diabetics.
Membrane flux and beta-2-microglobulin amyloidosis
High-flux dialysis membranes and/or intermittent internal on-line
Dialyzers and efficiency
Dialyzers come in many different sizes. A larger dialyzer with a larger membrane area (A) will usually remove more solutes than a smaller dialyzer, especially at high blood flow rates. This also depends on the membrane permeability coefficient K0 for the solute in question. So dialyzer efficiency is usually expressed as the K0A – the product of permeability coefficient and area. Most dialyzers have membrane surface areas of 0.8 to 2.2 square meters, and values of K0A ranging from about 500 to 1500 mL/min. K0A, expressed in mL/min, can be thought of as the maximum clearance of a dialyzer at very high blood and dialysate flow rates.
Reuse of dialyzers
The dialyzer may either be discarded after each treatment or be reused. Reuse requires an extensive procedure of high-level disinfection. Reused dialyzers are not shared between patients. There was an initial controversy about whether reusing dialyzers worsened patient outcomes. The consensus today is that reuse of dialyzers, if done carefully and properly, produces similar outcomes to single use of dialyzers.[31]
Dialyzer Reuse is a practice that has been around since the invention of the product. This practice includes the cleaning of a used dialyzer to be reused multiple times for the same patient. Dialysis clinics reuse dialyzers to become more economical and reduce the high costs of "single-use" dialysis which can be extremely expensive and wasteful. Single used dialyzers are initiated just once and then thrown out creating a large amount of bio-
There are two ways of reusing dialyzers, manual and automated. Manual reuse involves the cleaning of a dialyzer by hand. The dialyzer is semi-disassembled then flushed repeatedly before being rinsed with water. It is then stored with a liquid disinfectant(PAA) for 18+ hours until its next use. Although many clinics outside the USA use this method, some clinics are switching toward a more automated/streamlined process as the dialysis practice advances. The newer method of automated reuse is achieved by means of a medical device that began in the early 1980s. These devices are beneficial to dialysis clinics that practice reuse – especially for large dialysis clinical entities – because they allow for several back to back cycles per day. The dialyzer is first pre-cleaned by a technician, then automatically cleaned by machine through a step-cycles process until it is eventually filled with liquid disinfectant for storage. Although automated reuse is more effective than manual reuse, newer technology has sparked even more advancement in the process of reuse. When reused over 15 times with current methodology, the dialyzer can lose B2m, middle molecule clearance and fiber pore structure integrity, which has the potential to reduce the effectiveness of the patient's dialysis session. Currently, as of 2010, newer, more advanced reprocessing technology has proven the ability to eliminate the manual pre-cleaning process altogether and has also proven the potential to regenerate (fully restore) all functions of a dialyzer to levels that are approximately equivalent to single-use for more than 40 cycles.[32] As medical reimbursement rates begin to fall even more, many dialysis clinics are continuing to operate effectively with reuse programs especially since the process is easier and more streamlined than before.
Epidemiology
Hemodialysis was one of the most common procedures performed in U.S. hospitals in 2011, occurring in 909,000 stays (a rate of 29 stays per 10,000 population). This was an increase of 68 percent from 1997, when there were 473,000 stays. It was the fifth most common procedure for patients aged 45–64 years.[33]
History
Many have played a role in developing dialysis as a practical treatment for renal failure, starting with Thomas Graham of Glasgow, who first presented the principles of solute transport across a semipermeable membrane in 1854.[34] The artificial kidney was first developed by Abel, Rountree, and Turner in 1913,[35] the first hemodialysis in a human being was by Haas (February 28, 1924)[36] and the artificial kidney was developed into a clinically useful apparatus by Kolff in 1943 to 1945.[37] This research showed that life could be prolonged in patients dying of kidney failure.
According to McKellar (1999), a significant contribution to renal therapies was made by Canadian surgeon Gordon Murray with the assistance of two doctors, an undergraduate chemistry student, and research staff. Murray's work was conducted simultaneously and independently from that of Kolff. Murray's work led to the first successful artificial kidney built in North America in 1945–46, which was successfully used to treat a 26-year-old woman out of a uraemic coma in Toronto. The less-crude, more compact, second-generation "Murray-Roschlau" dialyser was invented in 1952–53, whose designs were stolen by German immigrant Erwin Halstrup, and passed off as his own (the "Halstrup–Baumann artificial kidney").[38]
By the 1950s, Willem Kolff's invention of the dialyzer was used for acute renal failure, but it was not seen as a viable treatment for patients with stage 5 chronic kidney disease (CKD). At the time, doctors believed it was impossible for patients to have dialysis indefinitely for two reasons. First, they thought no man-made device could replace the function of kidneys over the long term. In addition, a patient undergoing dialysis developed damaged veins and arteries, so that after several treatments, it became difficult to find a vessel to access the patient's blood.
The original Kolff kidney was not very useful clinically, because it did not allow for removal of excess fluid. Swedish professor
In 1962, Scribner started the world's first outpatient dialysis facility, the Seattle Artificial Kidney Center, later renamed the Northwest Kidney Centers. Immediately the problem arose of who should be given dialysis, since demand far exceeded the capacity of the six dialysis machines at the center. Scribner decided that he would not make the decision about who would receive dialysis and who would not. Instead, the choices would be made by an anonymous committee, which could be viewed as one of the first bioethics committees.
For a detailed history of successful and unsuccessful attempts at dialysis, including pioneers such as Abel and Roundtree, Haas, and Necheles, see this review by Kjellstrand.[42]
See also
References
- ^ "Kidney Failure: Choosing a Treatment That's Right for You". National Kidney and Urologic Diseases Information Clearinghouse guidance. Archived from the original on 2010-09-16.
- ^ a b Daugirdas JT, Black PG, Ing TS (2007). Handbook of Dialysis (4th ed.). Philadelphia, PA: Lippincott Williams & Wilkins, a Wolters Kluwer Business.
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- ^ The Ottawa Hospital (TOH). Guide: Treatment options for chronic kidney disease. Ottawa, Ontario:The Ottawa Hospital Riverside Campus;2008
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- ^ KDOQI Clinical Practice Guidelines for Hemodialysis Adequacy, 2006 Updates Archived 2007-06-30 at the Wayback Machine. CPR 5.
- ^ Strain N. "Dialysis Tech". Dialysis Clinic.
- ^ Pfuntner A, Wier LM, Stocks C (October 2013). Most Frequent Procedures Performed in U.S. Hospitals, 2011. HCUP Statistical Brief #165 (Report). Rockville, MD.: Agency for Healthcare Research and Quality.
- ^ Graham T. The Bakerian lecture: on osmotic force. Philosophical Transactions of the Royal Society in London. 1854;144:177–228.
- ^ Abel JJ, Rowntree LG, Turner BB (1913). "On the removal of diffusible substances from the circulating blood by means of dialysis". Transactions of the Association of American Physicians. 28: 51.
- ^ Paskalev DN (December 2001). "Georg Haas (1886-1971): The forgotten hemodialysis pioneer" (PDF). Dialysis and Transplantation. 30 (12): 828–32. Archived from the original (PDF) on 2007-12-02.
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- ^ University of Lund website: Nils Alwall. Archived 2007-10-01 at the Wayback Machine
- ^ Shaldon S. Development of Hemodialysis, From Access to Machine (presentation given during a symposium entitled: Excellence in Dialysis: Update in Nephrology; Karachi, Pakistan. October, 2002, as archived on HDCN
- ^ "NIDDK Contributions to Dialysis". Archived from the original on 2009-01-13. Retrieved 2007-10-09.
- ^ Kjellstrand CM. History of Dialysis, Men and Ideas. Talk given to the Nordic Nephrology Days Symposium, Lund, 1997, as archived on HDCN.
External links
- Your Kidneys and How They Work – (American) National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH.
- Treatment Methods for Kidney Failure – (American) National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH.
- Treatment Methods for Kidney Failure: Hemodialysis – (American) National Kidney and Urologic Diseases Information Clearinghouse, NIH.