Dialysis

This article is about renal dialysis. For the laboratory technique, see Dialysis (biochemistry). For treatment for liver failure, see Liver dialysis.
Dialysis
Intervention

Patient receiving dialysis
ICD-9-CM 39.95
MeSH D006435
MedlinePlus 00743

In medicine, dialysis (from Greek διάλυσις, diàlysis, meaning dissolution, διά, dià, meaning through, and λύσις, lỳsis, meaning loosening or splitting) is a process for removing waste and excess water from the blood and is used primarily as an artificial replacement for lost kidney function in people with kidney failure.[1] Dialysis may be used for those with an acute disturbance in kidney function (acute kidney injury, previously acute renal failure) or progressive but chronically worsening kidney function—a state known as chronic kidney disease stage 5 (previously chronic renal failure or end-stage renal disease). The latter form may develop over months or years, but in contrast to acute kidney injury is not usually reversible and dialysis is regarded as a "holding measure" until a kidney transplant can be performed or sometimes as the only supportive measure in those for whom a transplant would be inappropriate.[2]

The kidneys have important rol in maintaining health. When healthy, the kidneys maintain the body's internal equilibrium of water and minerals (sodium, potassium, chloride, calcium, phosphorus, magnesium, sulfate). The acidic metabolism end-products that the body cannot get rid of via respiration are also excreted through the kidneys. The kidneys also function as a part of the endocrine system, producing erythropoietin, calcitriol and renin. Erythropoietin is involved in the production of red blood cells and calcitriol plays a role in bone formation.[3] Dialysis is an imperfect treatment to replace kidney function because it does not correct the compromised endocrine functions of the kidney. Dialysis treatments replace some of these functions through diffusion (waste removal) and ultrafiltration (fluid removal).[4]

History

Arm showing tubes

A Dutch physician, Willem Johan Kolff, constructed the first working dialyzer in 1943 during the Nazi occupation of the Netherlands.[5] Due to the scarcity of available resources, Kolff had to improvise and build the initial machine using sausage casings, beverage cans, a washing machine, and various other items that were available at the time. Over the following two years, [1943–1945] Kolff used his machine to treat 16 patients suffering from acute kidney failure, but the results were unsuccessful. Then, in 1945, a 67-year-old comatose woman regained consciousness following 11 hours of hemodialysis with the dialyzer, and lived for another seven years before dying from an unrelated condition. She was the first-ever patient successfully treated with dialysis.[5] Dr. Nils Alwall modified a similar construction to the Kolff kidney by enclosing it inside a stainless steel canister. This allowed the removal of fluids, by applying a negative pressure to the outside canister, thus making it the first truly practical device for hemodialysis. Alwall treated his first patient in acute kidney failure on September 3, 1946.

Principle

A hemodialysis machine

Dialysis works on the principles of the diffusion of solutes and ultrafiltration of fluid across a semi-permeable membrane. Diffusion is a property of substances in water; substances in water tend to move from an area of high concentration to an area of low concentration.[6] 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 holes of various sizes, or pores. Smaller solutes and fluid pass through the membrane, but the membrane blocks the passage of larger substances (for example, red blood cells, large proteins). This replicates the filtering process that takes place in the kidneys, when the blood enters the kidneys and the larger substances are separated from the smaller ones in the glomerulus.[6]

The two main types of dialysis, hemodialysis and peritoneal dialysis, remove wastes and excess water from the blood in different ways.[2] Hemodialysis removes wastes and water by circulating blood outside the body through an external filter, called a dialyzer, that contains a semipermeable membrane. The blood flows in one direction and the dialysate flows in the opposite. The counter-current flow of the blood and dialysate maximizes the concentration gradient of solutes between the blood and dialysate, which helps to remove more urea and creatinine from the blood. The concentrations of solutes (for example potassium, phosphorus, and urea) are undesirably high in the blood, but low or absent in the dialysis solution, and constant replacement of the dialysate ensures that the concentration of undesired solutes is kept low on this side of the membrane. The dialysis solution has levels of minerals like potassium and calcium that are similar to their natural concentration in healthy blood. For another solute, bicarbonate, dialysis solution level is set at a slightly higher level than in normal blood, to encourage diffusion of bicarbonate into the blood, to act as a pH buffer to neutralize the metabolic acidosis that is often present in these patients. The levels of the components of dialysate are typically prescribed by a nephrologist according to the needs of the individual patient.

In peritoneal dialysis, wastes and water are removed from the blood inside the body using the peritoneum as a natural semipermeable membrane. Wastes and excess water move from the blood, across the peritoneal membrane, and into a special dialysis solution, called dialysate, in the abdominal cavity.

Types

There are three primary and two secondary types of dialysis: hemodialysis (primary), peritoneal dialysis (primary), hemofiltration (primary), hemodiafiltration (secondary), and intestinal dialysis (secondary).

Hemodialysis

Main article: Hemodialysis

In hemodialysis, the patient's blood is pumped through the blood compartment of a dialyzer, exposing it to a partially permeable membrane. The dialyzer is composed of thousands of tiny hollow synthetic fibers. The fiber wall acts as the semipermeable membrane. Blood flows through the fibers, dialysis solution flows around the outside of the fibers, and water and wastes move between these two solutions.[7] The cleansed blood is then returned via the circuit back to the body. Ultrafiltration occurs by increasing the hydrostatic pressure across the dialyzer membrane. This usually is done by applying a negative pressure to the dialysate compartment of the dialyzer. This pressure gradient causes water and dissolved solutes to move from blood to dialysate, and allows the removal of several litres of excess fluid during a typical 4-hour treatment. In the United States, hemodialysis treatments are typically given in a dialysis center three times per week (due in the United States to Medicare reimbursement rules); however, as of 2005 over 2,500 people in the United States are dialyzing at home more frequently for various treatment lengths.[8] Studies have demonstrated the clinical benefits of dialyzing 5 to 7 times a week, for 6 to 8 hours. This type of hemodialysis is usually called "nocturnal daily hemodialysis", which a study has shown a significant improvement in both small and large molecular weight clearance and decrease the requirement of taking phosphate binders.[9] These frequent long treatments are often done at home while sleeping, but home dialysis is a flexible modality and schedules can be changed day to day, week to week. In general, studies have shown that both increased treatment length and frequency are clinically beneficial.[10]

Hemo-dialysis 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).[11]


Pediatric Dialysis

Over the past 20 years children have benefited from major improvements in both technology and clinical management of dialysis. Morbidity during dialysis sessions has decreased with seizures being exceptional and hypotensive episodes rare. Pain and discomfort have been reduced with the use of chronic internal jugular venous catheters and anesthetic creams for fistula puncture. Non-invasive technologies to assess patient target dry weight and access flow can significantly reduce patient morbidity and health care costs

A more biocompatible synthetic membranes and specific small size material dialyzers and new low extra-corporeal volume tubing have been developed for young infants, meaning that arterial and venous tubing length are made of minimum length and diameter, a <80ml to <110ml volume tubing is designed for peads patients and a >130 to <224ml tubing are for adult patients, its regardless of blood pump segment size, which can be of 6.4mm for normal dialysis or 8.0mm for high flux dialysis in all patients. all dialysis machine manufacturers do design their machine to do the pediatric dialysis. In pediatric patient The pump speed should be kept at low side according to patient blood output capacity and the clotting with heparin dose should be carefully monitored. it is that the high flux dialysis (see below) is not recommended on pediatric patients.

In children hemodialysis has to be individualized and viewed as an “integrated therapy” considering their long-term exposure to chronic renal failure treatment. Dialysis is seen only as a temporary measure for children compared with renal transplantation because this enables the best chance of rehabilitation in terms of educational and psychosocial functioning. In long term chronic dialysis, however, the highest standards should be applied to these children to preserve their future “cardiovascular life” which might include more dialysis time and on-line hemodiafiltration online hdf with synthetic high flux membranes with surface area of 0.2sq.m to 0.8sq.m and blood tubing lines with low volume yet large blood pump segment of 6.4/8.0mm, if we are able to improve on the rather restricted concept of small-solute urea dialysis clearance.

Peritoneal dialysis

Schematic diagram of peritoneal dialysis
Main article: Peritoneal dialysis

In peritoneal dialysis, a sterile solution containing glucose (called dialysate) is run through a tube into the peritoneal cavity, the abdominal body cavity around the intestine, where the peritoneal membrane acts as a partially permeable membrane. The peritoneal membrane or peritoneum is a layer of tissue containing blood vessels that lines and surrounds the peritoneal, or abdominal, cavity and the internal abdominal organs (stomach, spleen, liver, and intestines).[12] Diffusion and osmosis drive waste products and excess fluid through the peritoneum into the dialysate until the dialysate approaches equilibrium with the body's fluids. Then the dialysate is drained, discarded, and replaced with fresh dialysate.[13]

This exchange is repeated 4–5 times per day; automatic systems can run more frequent exchange cycles overnight. Peritoneal dialysis is less efficient than hemodialysis, but because it is carried out for a longer period of time the net effect in terms of removal of waste products and of salt and water are similar to hemodialysis. Peritoneal dialysis is carried out at home by the patient, often without help. This frees patients from the routine of having to go to a dialysis clinic on a fixed schedule multiple times per week. Peritoneal dialysis can be performed with little to no specialized equipment (other than bags of fresh dialysate).

Hemofiltration

Main article: Hemofiltration

Hemofiltration is a similar treatment to hemodialysis, but it makes use of a different principle. The blood is pumped through a dialyzer or "hemofilter" as in dialysis, but no dialysate is used. A pressure gradient is applied; as a result, water moves across the very permeable membrane rapidly, "dragging" along with it many dissolved substances, including ones with large molecular weights, which are not cleared as well by hemodialysis. Salts and water lost from the blood during this process are replaced with a "substitution fluid" that is infused into the extracorporeal circuit during the treatment.

Hemodiafiltration

Hemodiafiltration is a combination of hemodialysis and hemofiltration.

Intestinal dialysis

In intestinal dialysis, the diet is supplemented with soluble fibres such as acacia fibre, which is digested by bacteria in the colon. This bacterial growth increases the amount of nitrogen that is eliminated in fecal waste.[14][15][16] An alternative approach utilizes the ingestion of 1 to 1.5 liters of non-absorbable solutions of polyethylene glycol or mannitol every fourth hour.[17]

Starting indications

The decision to initiate dialysis or hemofiltration in patients with kidney failure depends on several factors. These can be divided into acute or chronic indications.

Indications for chronic dialysis: Chronic dialysis may be indicated when a patient has symptomatic kidney failure and low glomerular filtration rate (GFR). Between 1996 to 2008 there was a trend to initiate dialysis at progressively higher estimated GFR, eGFR. A review of the evidence shows no benefit or potential harm with early dialysis initiation, which has been defined by start of dialysis at an estimated GFR of greater than 10ml/min/1.732.Observational data from large registries of dialysis patients suggests that early start of dialysis may be harmful.[19] The most recent published guidelines from Canada, for when to initiate dialysis, recommend an intent to defer dialysis until a patient has definite kidney failure symptoms, which may occur at an estimated GFR of 5-9ml/min/1.732.[20]

Some reason for dialysis initiation include difficulty in medically controlling fluid overload or serum potassium. If a patient has intractable kidney failure symptoms or signs, start of dialysis may be recommended at eGFR levels above 10ml/min/1.732

Dialyzable substances

Characteristics

Dialyzable substances have following properties:

  1. low molecular mass
  2. high water solubility
  3. low protein binding capacity
  4. prolonged elimination (long half life)
  5. small volume of distribution

Substances

Dialysis provision in the United Kingdom

The National Health Service provides dialysis in the United Kingdom. In England the service is commissioned by NHS England. About 23,000 patients use the service each year.[21]

See also

Materials and methods

Medical applications

References

  1. ↑ "Dialysis".
  2. 1 2 Pendse S, Singh A, Zawada E. Initiation of Dialysis. In: Handbook of Dialysis. 4th ed. New York, NY; 2008:14–21
  3. ↑ Brundage D. Renal Disorders. St. Louis, MO: Mosby; 1992
  4. ↑ "Atlas of Diseases of the Kidney, Volume 5, Principles of Dialysis: Diffusion, Convection, and Dialysis Machines" (PDF). Retrieved 2011-09-02.
  5. 1 2 "Willem Kolff, Doctor Who Invented Kidney and Heart Machines, Dies at 97". New York Times. 12 February 2009.
  6. 1 2 Mosby’s Dictionary of Medicine, Nursing, & Health Professions. 7th ed. St. Louis, MO; Mosby: 2006
  7. ↑ Ahmad S, Misra M, Hoenich N, Daugirdas J. Hemodialysis Apparatus. In: Handbook of Dialysis. 4th ed. New York, NY; 2008:59-78.
  8. ↑ "USRDS Treatment Modalities" (PDF). United States Renal Data System. Retrieved 2011-09-02.
  9. ↑ Rocco, MV (July 2007). "More Frequent Hemodialysis: Back to the Future?". Advances in chronic kidney disease 14 (3): e1–9. doi:10.1053/j.ackd.2007.04.006. PMID 17603969.
  10. ↑ Daily therapy study results compared Archived June 4, 2013, at the Wayback Machine.
  11. ↑ Pfuntner A., Wier L.M., Stocks C. Most Frequent Procedures Performed in U.S. Hospitals, 2011. HCUP Statistical Brief #165. October 2013. Agency for Healthcare Research and Quality, Rockville, MD. .
  12. ↑ Blake P, Daugirdas J. Physiology of Peritoneal Dialysis. In: Handbook of Dialysis. 4th ed. New York, NY; 2008:323-338
  13. ↑ Kallenbach J.Z. In: Review of hemodialysis for nurses and dialysis personnel. 7th ed. St. Louis, Missouri:Elsevier Mosby; 2005.
  14. ↑ "Access". Medscape. Retrieved 2011-09-02.
  15. ↑ "Access". Medscape. Retrieved 2011-09-02.
  16. ↑ "Access". Medscape. Retrieved 2011-09-02.
  17. ↑ "Access". Medscape. Retrieved 2011-09-02.
  18. ↑ Irwin, Richard S.; James M. Rippe (2008). Irwin and Rippe's intensive care medicine. Lippincott Williams & Wilkins. pp. 988–999. ISBN 978-0-7817-9153-3.
  19. ↑ Rosansky, Steven; Glassock, Richard; Clark, William (2011). "Early Start of Dialysis: A Critical Review". Clin J Am Soc Nephrol 6: 1222–1228. doi:10.2215/cjn.09301010.
  20. ↑ Nesrallah, Gihad (Feb 2014). "Canadian Society of Nephrology 2014 clinical practice guideline for timing the initiation of chronic al indications for chronic dialysis". CMAJ 186: 112–117. doi:10.1503/cmaj.130363.
  21. ↑ "Specialised service transfer reconsidered due to incorrect data". Health Service Journal. 13 March 2015. Retrieved 20 April 2015.

Bibliography

  • Al-Mosawi, A. J. (2004). Acacia gum supplementation of a low-protein diet in children with end-stage renal disease. Pediatric Nephrology, 19(10), 1156-1159
  • Al Mosawi, A. J. (2007). The use of acacia gum in end stage renal failure. Journal of tropical pediatrics, 53(5), 362-365
  • Ali, A. A., Ali, K. E., Fadlalla, A. E., & Khalid, K. E. (2008). The effects of gum arabic oral treatment on the metabolic profile of chronic renal failure patients under regular haemodialysis in Central Sudan. Natural product research, 22(1), 12-21
  • Miskowiak, J. (1991). Continuous Intestinal Dialysis for Uraemia by Intermittent Oral Intake of Non-Absorbable Solutions: An Experimental Study. Scandinavian journal of urology and nephrology, 25(1), 71-74

External links

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