Dialysis hemodialysis

In medical applications, the dialysis SPM may be the patient s own stomach lining. A prepared solution is infused into the abdomen, stimulating osmotic flow of toxins across the stomach lining into the ingested solution, which is subsequently drained from the stomach. Alternatively, the dialyzer for blood dialysis (hemodialysis) may be a prepared membrane with special solution over which the blood flows to osmotically remove impurities. 

Thomson NP, Stevens BJ, ElumpheryTJ, Atkins RC. Comparison oftrace elements in peritoneal dialysis, hemodialysis and uremia. Kidney inn983 23 9-14. 

Various techniques to enhance elimination of caffeine have been reported in the literature. Multidose activated charcoal has been advocated to both prevent further absorption of drug and enhance elimination by gut dialysis. Hemodialysis has been reported in the literature for the treatment of caffeine toxicity. The mean plasma protein binding of caffeine (36%), the molecular size (194), and the volume of distribution (0.6-0.81kg ) make hemodialysis a possible modality to enhance elimination. There have also been cases of severe caffeine toxicity treated with peritoneal dialysis, but this modality is less efficient at drug clearance than hemodialysis. 

Individuals overexposed to isopropanol should be removed from exposure, affected areas of the skin should be washed with soap and water, and the eyes should be irrigated with water. Isopropanol is rapidly absorbed from the gastrointestinal tract. Efforts to decrease absorption are unlikely to be beneficial. Severe isopropanol overdoses have been managed successfully with either peritoneal dialysis or hemodialysis. Since the vast majority of patients respond completely with only supportive therapy, dialysis (hemodialysis much more effective than peritoneal) should be instituted in those patients with a history and physical exam consistent with a very large ingestion (blood isopropyl alcohol >400 mg dl ), those patients with hemodynamic instability (hypotension) and coma. 

In cases of loss of kidney function, mechanical devices—dialysis machines— mimic the action of the kidney The process of blood dialysis—hemodialysis— is discussed in A Clinical Perspective Hemodialysis on page 195. 

Exchange transfusion, peritoneal dialysis, hemodialysis, and hemoperfu-sion are not likely to be beneficial because of the large volume of distribution of these chemicals. 

Fiber dimensions have been studied for hemodialysis. When blood is circulated through the fiber lumen (m vivo), a significant reduction in apparent blood viscosity may occur if the flow-path diameter is below 100 p.m (11). Therefore, current dialy2ers use fibers with internal diameters of 180—250 p.m to obtain the maximum surface area within a safe range (see Dialysis). The relationship between the fiber cross section and the blood cells is shown in Figure 5. In many industrial appUcations, where the bore fluid is dialy2ed under elevated pressure (>200 kPa or 2 atm), fibers may burst at points of imperfection. Failure of this nature is especially likely for asymmetric fibers that display a large number of macro voids within the walls. 

Hollow Fiber with Sorbent Walls. A cellulose sorbent and dialy2ing membrane hoUow fiber was reported in 1977 by Enka Glan2stoff AG (41). This hoUow fiber, with an inside diameter of about 300 p.m, has a double-layer waU. The inner waU consists of Cuprophan ceUulose and is very thin, approximately 8 p.m. The outer waU, which is ca 40-p.m thick, consists mainly of sorbent substance bonded by ceUulose. The advantage of such a fiber is that it combines the principles of hemodialysis with those of hemoperfusion. Two such fibers have been made one with activated carbon in the fiber waU, and one with aluminum oxide, which is a phosphate binder (also see Dialysis). 

Maintenance hemodialysis has grown and expanded beyond the expectations of even the most enthusiastic of its eadiest proponents. Figure 7 is a plot of the overall estimated dialysis population by year siace 1970. The population at the end of 1992 exceeded 475,000 another 500,000 patients or so have received therapy at one time but have siace died or had transplants. Maintenance dialysis is now available to some extent ia all but the poorest nations ia economically advanced countries, excepting the United Kingdom, it is rendered as a virtual entitlement. The current worldwide mean cost of a single dialysis patient is about 30,000 per year (47) the aggregate economic magnitude of the medical appHcation of hemodialysis thus approaches 15 biUion. 

Fig. 7. Estimate of the total number of patients receiving maintenance dialysis over the past 20 years. Totals include both hemodialysis and peritoneal dialysis, but exclude transplant recipients. The fraction of patients receiving peritoneal dialysis has grown steadily from 0% in 1978 to about 12% in 1992. These data were combined from various regional registries and industry sources demographic estimates of this iLk are accurate to within 5% (46). D,...

Hemodialysis with microencapsulated urease and an ammonia ion adsorbent, zirconium phosphate [13772-29-7], has been used (247) to delay the onset of dialysis therapy in patients retaining some renal function, and to reduce the time between dialysis treatment. 

Dialysis and Hemodialysis Historically, dialvsis has found some industrial use. Today, much of that is supplanted by iiltrafiltration, Donan dialysis is treated briefly under electrodialysis. Hemodialysis is a huge application for membranes, and it dominates the membrane field in area produced and in rnonetaiv aliie. This medical application is omitted here. 

The effect of hemodialysis can be derived from the removed fraction (FR) that is the relative amount eliminated from the body during the time (/HD) of one dialysis session. This fraction can be derived from the half-life on dialysis (Tl/2on) or from the area under the curve (AUC) on and off dialysis. 

After dialysis, often a rebound is seen in concentrations since elimination from plasma is faster than drug flux from tissue to plasma (Crebound — Ctissue - C). The concentration in plasma follows a bi-exponential kinetics during hemodialysis whereas the concentration in tissue follows mono-exponential kinetics. 

Life expectancy < 1 year from other causes Peritoneal dialysis or hemodialysis ... 

Another indirect electrochemical heahng method involves the artificial kidney machine, with electrochemical regeneration of the dialysis solution. The common kidney machine is a dialyzer in which blood of the patient (who suffers from kiduey insufficiency) and a dialysis solution are pumped arouud iu two differeut loops, aud carbamide (urea), creatinine, and other metabolites are transferred by dialysis into the dialysis solution. For complete extraction of the metabolites, each hemodialysis session requires almost 200 L of this solution to be pumped through, so hemodialysis cau only be performed in a hospital setting. In machines equipped with electrochemical regeueratiou, the dialysis solutiou is ruu iu a closed loop, iucludiug au electrolyzer in which the carbamide is oxidized to nitrogen and carbon dioxide. The solution volume needed in this loop is rather small, so that portable kidney machines could become a reality. 

All patients with major patterns are monitored for rhabdomyolysis and renal failure. An early sign of rhabdomyolysis is an elevated serum uric acid, associated with an increase in serum CK. Within 8 to 12 hours, the serum tests are repeated. If the uric acid falls and the CK rises, rhabdomyolysis is likely. Renal function tests may also be increased at this time. When the diagnosis of rhabdomyolysis is made, the patient is treated with 40 mg furose-mide IV once, and IV fluids. Urine myoglobin concentrations are obtained. If the patient develops renal failure, hemodialysis or peritoneal dialysis may be necessary. In all cases, multiple drug intoxication, trauma, and rhabdomyolysis are ruled out or treated. All patients are kept under observation until they are asymptomatic. 

With either type of dialysis, studies suggest that recovery of renal function is decreased in ARF patients who undergo dialysis compared with those not requiring dialysis. Decreased recovery of renal function may be due to hemodialysis-induced hypotension causing additional ischemic injury to the kidney. Also, exposure of a patient s blood to bioincompatible dialysis membranes (cuprophane or cellulose acetate) results in complement and leukocyte activation which can lead to neutrophil infiltration into the kidney and release of vasoconstrictive substances that can prolong renal dysfunction.26 Synthetic membranes composed of substances such as polysulfone, polyacrylonitrile, and polymethylmethacrylate are considered to be more biocompatible and would be less likely to activate complement. Synthetic membranes are generally more expensive than cellulose-based membranes. Several recent meta-analyses found no difference in mortality between biocompatible and bioincompatible membranes. Whether biocompatible membranes lead to better patient outcomes continues to be debated. 

Fluid restriction is generally unnecessary as long as sodium intake is controlled. The thirst mechanism remains intact in CKD to maintain total body water and plasma osmolality near normal levels. Fluid intake should be maintained at the rate of urine output to replace urine losses, usually fixed at approximately 2 L/day as urine concentrating ability is lost. Significant increases in free water intake orally or intravenously can precipitate volume overload and hyponatremia. Patients with stage 5 CKD require renal replacement therapy to maintain normal volume status. Fluid intake is often limited in patients receiving hemodialysis to prevent fluid overload between dialysis sessions. 

When replacing iron stores in patients receiving ESA therapy, the general approach to treatment is to give a total of 1 g of IV iron, administered in smaller, sequential doses. Because iron stores deplete quickly in patients who do not receive iron supplementation, maintenance doses are often used, particularly in patients receiving hemodialysis. Maintenance doses consist of smaller doses of iron administered weekly or with each dialysis session (e.g., iron dextran or iron sucrose 20 to 100 mg per week sodium ferric gluconate 62.5 to 125 mg per week). 

The cause of pruritus is unknown, although several mechanisms have been proposed. Vitamin A is known to accumulate in the skin and serum of patients with CKD, but a definite correlation with pruritus has not been established. Histamine may also play a role in the development of pruritus, which may be linked to mast cell proliferation in patients receiving hemodialysis. Hyperparathyroidism has also been suggested as a contributor to pruritus, despite the fact that serum PTH levels do not correlate with itching. Accumulation of divalent ions, specifically magnesium and aluminum, may also play a role in pruritus in patients with CKD. Other theories that have been proposed include inadequate dialysis, dry skin, peripheral neuropathy, and opiate accumulation.43... 

Even though intermittent heparinization is required, hemostasis parameters are better corrected with hemodialysis than peritoneal dialysis. 

Dysequilibrium, dialysis, hypotension, and muscle cramps are common. May require months before patient adjusts to hemodialysis. 

From El we 11 RJ, Foote EF. Hemodialysis and peritoneal dialysis. In DiPiro JT, Talbert RL, Yee GC, et al, (eds.) Pharmacotherapy A Pathophysiologic Approach. 6th ed. New York McGraw-Hill 2005 852, with permission. 

Hypotension is the most common complication seen during hemodialysis. It has been reported to occur with approximately 10% to 30% of dialysis sessions, but maybe as frequent as 50% of sessions in some patients.46... 

Pathophysiology Hypotension associated with hemodialysis manifests as a symptomatic sudden drop of more than 30 mm Hg in mean arterial or systolic pressure or a systolic pressure drop to less than 90 mm Hg during the dialysis session. The primary cause is fluid removal from the bloodstream. Ultrafiltration removes fluid from the plasma, which... 

Pathophysiology Muscle cramps can occur with up to 20% of dialysis sessions.48 The cause is often related to excessive ultrafiltration, which causes hypoperfusion of the muscles. Other contributing factors to the development of muscle cramps include hypotension and electrolyte and acid-base imbalances that occur during hemodialysis sessions. 

Thrombosis associated with hemodialysis most commonly occurs in patients with venous catheter access for dialysis and is a common cause of catheter failure. However, thrombosis can occur in synthetic grafts and less frequently in AV fistulas. 

Peritoneal dialysis (PD) utilizes similar principles as hemodialysis in that blood is exposed to a semipermeable membrane against which a physiologic solution is placed. In the case of PD, however, the semipermeable membrane is the peritoneal membrane, and a sterile dialysate is instilled into the peritoneal cavity. The peritoneal membrane is composed of a continuous single layer of mesothelial cells that covers the abdominal and pelvic walls on one side of the peritoneal cavity, and the visceral organs, including the GI tract, liver, spleen, and diaphragm on the other side. The mesothelial cells are covered by microvilli that increase the surface area of the peritoneal membrane to approximate body surface area (1 to 2 m2). 

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