12 - Dialysis
Editors: Schrier, Robert W.
Title: Manual of Nephrology, 6th Edition
Copyright 2005 Lippincott Williams & Wilkins
> Table of Contents > 12 - The Patient Receiving Chronic Renal Replacement with Dialysis
12
The Patient Receiving Chronic Renal Replacement with Dialysis
David M. Spiegel
The number of individuals kept alive by dialysis therapy in the United States continues to increase each year. This life-prolonging therapy continues to make end stage kidney failure the only major organ system failure that does not result in certain death without organ transplantation. However, the morbidity and mortality associated with end stage kidney disease (ESRD) remains high. Increased understanding of the disease process, new insights into pathogenic mechanisms, and new therapeutic options are emerging that may improve survival rates and quality of life for patients with ESRD.
The need for renal replacement therapy (RRT). RRT is required when kidney function deteriorates to the point where the accumulation of waste products begins to interfere with life functions. As kidney function deteriorates, a number of physiologic alterations occur, many of which are ultimately detrimental. Renal replacement therapy is indicated when these changes can no longer be controlled by medications and diet, or when the accumulation of waste products starts to interfere with life functions. The progressive deterioration of kidney function through end stage kidney failure has been defined as chronic kidney disease (CKD). Appropriate care designed to slow the progression of CKD, control factors known to contribute to the morbidity and mortality of kidney failure, and appropriate preparation for RRT during the stages of CKD ensures that patients are in the best overall condition at the time they start dialysis. (See Chapter 11.)
Preparing for RRT
Access creation. Preparation for dialysis therapy is critical for the smooth transition from CKD care to RRT. Poor planning for RRT is a major cause of increased morbidity and mortality at the initiation of dialysis therapy. The use of temporary or tunneled dialysis catheters contributes to dialysis mortality by increasing the incidence of sepsis, acting as a stimulus for chronic inflammation, and damaging the central veins, thereby preventing or shortening the survival of more permanent vascular access once created.
Hemodialysis (HD). Permanent access for HD requires either a native arterial-venous fistula (AVF) or an artificial AV graft. Both types of accesses are placed surgically. Native AVFs are always preferable to artificial grafts, because they have a significantly lower incidence of infection and a longer event-free survival. Vein mapping by ultrasound or venography may increase the likelihood of successful AVF placement by identifying suitable veins for access creation. In ideal candidates, an AVF may mature in as little as 4 weeks. However, in patients with less than ideal veins, AVFs can take 6 months or longer to mature. Therefore, access planning should start 6 to 12 months before dialysis is anticipated. As a general rule, the longer an AVF matures prior to first use, the better the chances for long-term success. For artificial grafts, surgery should be performed 4 to 6 weeks before the anticipated start of dialysis. Usually the access is placed in the nondominant arm, in the most distal position available.
Peritoneal dialysis (PD). PD catheters are surgically inserted into the peritoneal cavity. Several types of catheters are now available and the time from placement to first use may vary greatly. Most nephrologists allow 7 to 10 days before using a catheter that is externalized at the
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time of implantation. Many PD catheters are left in a subcutaneous tunnel for several months before being externalized. This option may allow better in-growth of the catheter in a sterile environment and allows for externalization at the time of training.
Modality selection. Current evidence suggests that both PD and HD provide equal RRT for most patients. Modality selection should be based on patient preference, which is largely related to lifestyle decisions. Proper education, starting early in the course of CKD, is the best means of ensuring that patients are able to make rational and educated decisions.
Hemodialysis
In-center HD. The largest percentages of dialysis patients in the United States are dialyzed via this modality. As a general rule, patients dialyze on a 3 times per week basis for approximate 4 hours each session. At the beginning and throughout the treatment, vital signs are measured. Two needles are placed in the AVF or graft so that blood can be circulated through the artificial kidney at a rate of 300 to 500 mL per minute. Excess fluid is removed by a transmembrane pressure gradient, while toxins are removed by diffusion down their concentration gradient. At the end of the treatment, the needles are removed and bleeding stopped by the application of local pressure. Although most patients participate very little in their actual dialysis care, some facilities promote self-care, where in patients actively participate by taking their blood pressure (BP), responding to machine alarms, and even performing needle placement.
Home HD. The number of patients on home HD in the United States remains small. Traditionally, this therapy has required a partner to help with the treatment, especially in emergencies. However, newer machines designed for home use are making it possible for some patients without partners to receive the benefits of home HD. The average training time before patients are able to perform HD at home is about 6 weeks. Once trained, patients generally do quite well, having the lowest mortality rate of any group of U.S. dialysis patients. Part of this low mortality may be related to patient selection, since traditionally only the healthiest patients were selected for home HD.
New HD therapies. Emerging HD therapies offer some advantages over current treatment and may ultimately improve the quality of life of dialysis patients, along with increasing survival. These therapies include daily home HD, nocturnal HD, and daily in-center HD. In both daily home and daily in-center HD, patients dialyze 2 to 3 hours, 6 days per week. Nocturnal dialysis is typically 6 to 8 hours, 6 days per week, although fewer treatments per week are being studied. In all these therapies, the advantages are that patients dialyze more frequently and achieve higher clearances than with traditional HD. The increased dialysis frequency allows for better fluid and BP control. Noncontrolled trials also suggest that patients feel better, experience a higher quality of life, and are more socially adjusted. Some studies have found a reduced requirement for erythropoeitin, although this has not been universal. Patients on nocturnal HD generally have greatly reduced need for phosphate binders (see IV.A.6.c.(3)). Although these therapies are more expensive than traditional HD, emerging evidence suggests that the total cost of patient care may be decreased, because patients on these more frequent therapies have a decreased need for supplemental medications and experience fewer hospitalizations.
Peritoneal dialysis
Continuous ambulatory PD (CAPD), along with automated PD (APD) accounts for 15% to 18% of all dialysis in the United States. With this dialysis modality the semi-permeable lining of the peritoneal cavity is used as a dialysis membrane such that toxins diffuse out of the blood into a sterile dialysate fluid that has been instilled into the abdominal
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cavity. The process of draining out the old PD dialysate and instilling fresh dialysate into the peritoneal cavity is referred to as an exchange. As patients perform the PD exchanges at home, PD allows patients a more flexible schedule than HD, because the exchanges can be done around most schedules. Another advantage of PD is that patients in remote areas do not have to travel to a dialysis center.APD uses a machine to perform the dialysis exchanges, usually overnight, thus allowing patients greater daytime flexibility. This is especially useful for people in school or young children.
Renal replacement therapy. The appropriate time to initiate dialysis for a patient cannot be clearly defined. Most nephrologists base their decision upon clinical laboratory data and a subjective patient assessment. By the time the glomerular filtration rate (GFR) falls below 10 mL per minute, most patients require dialytic intervention. However, many patients appear to function quite well until the GFR approaches 5 mL per minute. As a general rule, patients with diabetes require earlier intervention (GFR less than 15 mL per minute) than do those with other etiologies for their renal failure. Clearly, dialysis must be initiated before the uremic symptoms of peripheral neuropathy, encephalopathy, malnutrition, or serositis (including pericarditis) become evident. Although many of these complications resolve with adequate dialysis, peripheral neuropathy and malnutrition may be exceedingly difficult to reverse. Some nephrologists believe that early initiation with dialysis may improve long-term outcome, although this has not been shown to be true.
Hemodialysis
Technical aspects. Although the basic principles of HD (diffusion-based mass transfer of solute and pressure gradient driven water removal) have not changed a great deal in the last 20 years, the technology has dramatically improved. Most patients dialyze three times per week. For each treatment, two large-bore needles are inserted into the vascular access for removal and return of blood. The patient must remain confined to their dialysis machine for the duration of the treatment. Today, most dialysis units use volumetric machines designed to remove a precise amount of fluid. These volumetric machines permit the use of larger, highly porous dialyzers with high water and solute permeability. This new design not only allows for significantly more removal of larger molecules than older dialyzers, but also increases the efficiency of urea removal.
Adequacy. What constitutes optimal HD remains controversial. Urea kinetic modeling is a useful tool to quantify dialysis and thereby prevent underdialysis. Care must be taken to ensure that the modeling is based on delivered dialysis. Additionally, as dialysis times are shortened, plasma urea rebound due to delayed intercompartmental shifts must be considered. Currently, a delivered dialysis dose, as measured by a urea removal, of less than 65% or a Kt/V (where K equals the dialyzer clearance of urea, t is the treatment time, and V is the urea volume of distribution) of less than 1.2 is considered inadequate (1). To ensure adequate dialysis, the recommended targets have been set at a URR of greater than or equal to 70% [URR = 100 (1-Ct/C0), where Ct is the postdialysis BUN and C0 is the pre-dialysis BUN] or a Kt/V of greater than or equal to 1.3 (determined by formal urea kinetic modeling or the Kt/V natural logarithm formula (1).
Blood pressure control. Cardiovascular mortality remains the leading cause of death in ESRD patients. Whereas the condition of patients at the time they start dialysis clearly plays a role in their long-term outcome, optimal BP control while on dialysis remains critical. The timing of BP determination in HD patients is controversial. Most patients experience a fall in BP during their dialysis treatment, often correlated with the amount of fluid removed. Therefore, post-dialysis BP is usually lower than pre-dialysis BP. In most studies that have closely evaluated BP in
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dialysis patients, it is clear that within 8 to 12 hours post-dialysis, BP has returned to pre-dialysis levels. It is therefore generally recommended that of the two, the pre-dialysis BP better reflects overall hypertensive risk. However, due to the fall in BP with dialysis, it is generally accepted that a slightly higher than normal BP be accepted for patients pre-dialysis. Although there are no definitive studies, and the topic remains controversial, many nephrologists aim for a pre-dialysis target of less 140 to 160/95 mm Hg.In the United States, 50% to 80% of dialysis patients are receiving antihypertensive therapy. Some evidence suggests that many of these patients could have their BP adequately controlled without or with significantly less antihypertensive medications if adequate dialysis was provided along with vigilant control of fluid volume. Although all antihypertensive medications except diuretics are available to treat dialysis patients, the use of both angiotensin converting enzyme (ACE) inhibitors and beta-blockers are increasing due to their cardioprotective advantage. Carvedilol has recently been shown to decrease mortality in a prospective study of dialysis patients with dilated cardiomyopathy (2).
Anemia. Anemia occurs in most dialysis patients and almost certainly contributes to cardiac hypertrophy. Studies have shown that the anemia of ESRD is largely due to a deficiency of erythropoietin (EPO) and can be corrected by administration of exogenous EPO. Initial doses usually range from 120 to 180 units per kg per week intravenously, or 80 to 120 units per kg per week subcutaneously (1). Dose adjustments are then made on a monthly or every-other-week basis. Adequate iron stores are also required. The correction of anemia in dialysis patients has been shown to improve patients' quality of life and exercise physiology. Short-term studies have shown a decrease in cardiac hypertrophy when the anemia of CRF was partially corrected. As with hypertension, some data suggest that adequate dialysis is associated with improved hemoglobin values and a decreased EPO requirement. The optimal level of hemoglobin for dialysis patients remains to be determined. Clear survival benefits have been achieved by increasing the hemoglobin to greater than 11 gm per dL. Some retrospective studies suggest that improved survival can be achieved by hemoglobin levels in the normal range. However, one prospective randomized trial was stopped early due to failure to show improved benefit in a large group of dialysis patients with underlying heart disease whose hemoglobin values were normalized (3). A smaller European randomized trial showed no difference in survival between patients with hemoglobin values maintained between 11 to 12 and 13 to 14 mg per dL in patients without heart disease (4).
Rehabilitation and psychosocial adjustment. When compared to the normal U.S. population, patients on HD have a much lower employment rate and a much higher percentage of disability recipients. Efforts to improve these figures through vocational rehabilitation have been only marginally successful. However, on quality of life questionnaires, most HD patients rate their quality of life only slightly below the general population. Despite their overall high self-rating on quality of life questionnaires, many dialysis patients suffer from depression and anxiety disorders. A social worker is a critical member of all dialysis facility teams and can play a vital role in helping patients adjust to dialysis and deal with feelings of depression and anxiety.
Complications. Despite its life-saving nature, HD remains a poor substitute for normal renal function and is fraught with a number of complications, both technical and secondary to kidney failure itself.
Technical complications
Vascular access. Despite recent advances, vascular access remains the Achilles heel of HD. Although some arteriovenous fistulas last 5 to 20 years, many patients have poor native vessels and
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therefore have shortened AVF survival rates. These patients often must rely on artificial grafts, which are predisposed to thrombosis, pseudoaneurysm formation, and infection. The average survival of new grafts is about 2 years. Early intervention for failing grafts, along with new radiologic techniques, has improved the average survival rate (5). Intervention can take several forms, including the measurement of static or dynamic venous pressures or indirect measures of access blood flow rate.Hypotension. Despite improvements in dialysis equipment, hypotension remains a common problem during HD. Use of bicarbonate dialysate, higher dialysate sodium concentrations, and volumetric machines have helped to decrease its frequency. However, hypotension continues to occur for a number of reasons including autonomic insufficiency, rapid ultrafiltration (fluid removal) that exceeds the rate of vascular refilling, or myocardial dysfunction.
Allergic reactions. These can occur to the dialyzer material or the sterilant. They can range from mild itching to anaphylaxis.
Other. Air embolism, ruptured dialyzer, improper dialysate mixture, or failures of the water purification system are a cause of rare but often life-threatening complications. Care and proper maintenance of dialysis machines and water treatment facilities, with special attention to the dialysis technique and to the safety and alarm mechanisms, help prevent these complications.
Complications associated with inadequate dialysis
Uremic pericarditis. Although often thought of as a pre-dialysis problem, occasionally HD patients develop pericarditis. This often occurs in the setting of an acute illness, catabolic states, or at a time of vascular access difficulty, resulting in inadequate dialysis.
Uremic neuropathy. This complication is often overlooked by many nephrologists, because it is generally a peripheral neuropathy starting in the feet or hands. It must be differentiated from diabetic neuropathy, which is common in the dialysis population. Because the two conditions can co-exist, chronic inadequate dialysis must considered as a possible cause for any peripheral neuropathy.
Long-term complications
Cardiovascular. Cardiovascular death remains the major cause of mortality in patients with ESRD. Many factors contribute, including hypertension, anemia, smoking, hypercholesterolemia, and the presence of an arteriovenous shunt. Most of these factors are present long before the development of ESRD. Although the aggressive treatment of these risk factors seems prudent, good clinical studies in ESRD patients are lacking. New evidence shows that kidney failure, and possibly the abnormal mineral metabolism that results, increases the deposition of calcium in the media of blood vessels in patients. This calcium deposition appears to be an active process, much like the calcium deposition in bone. This medial vascular calcification has been associated with increased mortality presumably due to alterations in normal vascular physiology. Typical findings in patients with excessive vascular calcification are a widened pulse pressure and linear calcium deposition on plain films. In patients on dialysis, evidence of cardiac dysfunction and vascular calcification predict poor outcome (6,7).
Infectious. Infections remain a common cause of morbidity and mortality in HD patients. Infection of temporary catheters and artificial AV grafts are common. When they become infected, temporary catheters generally must be removed. Evidence suggests that changing the catheter over a guidewire, along with antibiotic therapy, may allow for resolution of the infection. Staphylococcal organisms remain the most common, followed by other gram-positive
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bacteria. Work on a staphylococcal vaccine for dialysis patients is ongoing. Endocarditis is a very serious complication that may result from a catheter or graft infection. Native vein fistulas have a lower infection rate than all forms of temporary or artificial graft material and are the access of first choice. In addition to the vascular access as a route of infection, improper reprocessing of dialyzers can lead to sepsis, often from waterborne organisms.Bone disease. Bone disease is common in long-term dialysis patients. The morphology of the bone pathology has changed over the past 10 years. Hyperparathyroid bone disease (i.e., osteitis fibrosa), remains the most common. It results from overactivity of the parathyroid glands as a result of hyperphosphatemia and low 1,25-vitamin D3 levels. Rapid bone turnover, increased osteoclastic activity, and ultimately fibrosis of the marrow space characterize this bone disease. It can be mild to severe, pure or mixed with aluminum (Al) bone disease. Aluminum is directly toxic to bone. Dialysis patients can acquire Al either through oral Al-containing phosphate binders or via a contaminated water supply. It accumulates due to lack of renal excretion and deposits at the mineralization front of growing or remodeling bone. This impairs bone mineralization and leads to a condition of weakened bone with increased unmineralized matrix or osteoid (osteomalacia). A histologic pattern increasingly found in bone biopsies from dialysis patients has been termed adynamic bone. This bone is characterized by very low bone turnover with few osteoblasts or osteoclasts. Whereas severe hyperparathyroidism can cause hypercalcemia, both adynamic and Al bone disease also predispose patients to hypercalcemia. Treatment for the abnormalities of mineral metabolism in ESRD has traditionally been limited to oral phosphate binders and intravenous or oral vitamin D preparations. The recent cloning of the calcium sensing receptor has allowed for a new class of therapeutic agents called calcimimetics. These small organic compounds bind to the calcium sensing receptor and modify its affinity for calcium. Through a second intracellular messenger, the net effect is a reduction in parathyroid hormone release (8). Work is ongoing in an attempt to determine whether the abnormalities in bone mineral metabolism or the current treatment of bone disease are linked in any way to the abnormal vascular calcification seen in dialysis patients. A final form of bone and osteoarticular disease seen in long-term dialysis patients is beta-2-microglobulin ( 2M) amyloidosis. 2M is a small protein that accumulates in the blood of dialysis patients and precipitates at osteoarticular surfaces to form amyloid. Symptoms include pain, swelling, bone cysts, and fractures. Recent data suggest that highly permeable dialysis membranes may delay the onset of disease symptoms.
Malnutrition inflammation syndrome. Large-scale studies have demonstrated that the nutritional state of a dialysis patient, as measured by the serum albumin, has a major impact on their long-term survival. Traditionally, it was believed that a low albumin reflected inadequate protein and calorie intake to maintain lean body mass. Whereas some patients do suffer from true malnutrition, it is now recognized that albumin is an important inverse acute phase reactant, and the utility of a low serum albumin as a marker of mortality probably reflects in large part the presence of an active inflammatory process rather than specific nutritional deficiencies. Although the cause of the chronic inflammation is evident in some patients, in many patients a clearly identifiable cause cannot be found. The finding of a low serum albumin
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and elevated levels of inflammatory markers has been termed the malnutrition-inflammation syndrome. Identifying and correcting reversible causes of both inflammation and malnutrition is essential to maintaining optimal health in patients with ESRD.Skin disorders. Pruritus remains one of the most troubling complaints of dialysis patients. Causes include an elevated calcium-phosphorus product, dry skin, and hyperparathyroidism. Some relief may be achieved with antihistamines and phosphate control. In severe cases, treatment with ultraviolet (UV) light has been effective. Other skin conditions in dialysis patients include bullous dermatitis and porphyria cutanea tarda.
Acquired renal cystic disease. Many patients undergoing maintenance dialysis develop cysts in their native kidneys that tend to increase in size and number over time. Although these cysts are generally an incidental finding, complications have been reported including polycythemia, spontaneous rupture, and retroperitoneal bleeding. Dialysis patients with acquired renal cystic disease appear to have a 100-fold increase in the incidence of renal cell carcinoma. However, deaths from renal cancer remains uncommon in the ESRD population, and routine screening has not been advocated due to the high rate of false positive studies that might lead to unnecessary surgery in this high-risk population. Patients with hematuria, flank pain, or abnormal weight loss should be evaluated.
Peritoneal dialysis
Technical aspects. Technically, PD is much less complex than HD. A sterile electrolyte and dextrose solution (dialysate) is allowed to flow into the peritoneal cavity through a previously implanted catheter using gravity or via a low-pressure pump. Following a specified period (dwell time), the fluid is drained out of the peritoneal cavity and fresh fluid is again infused. The peritoneal lining acts as the semi-permeable membrane across which diffusion occurs. The process of fluid infusion and drainage (exchanges) can be performed manually (CAPD) or by a machine (APD). A new, nondextrose dialysate solution is now available in the United States. Its advantages include a long duration of osmotic activity due to its poor peritoneal transport and the lack of a glucose load to the patient that occurs when the dextrose in traditional PD fluid is absorbed across the peritoneal membrane (9).
Adequacy. Because the quantity of PD that can be delivered is limited by the fixed peritoneal membrane kinetics and the amount of dialysate that can be comfortably infused and carried, it seems prudent to deliver as much dialysis as is reasonably possible. For many patients on PD, residual kidney function plays a vital role in their ability to achieve adequate creatinine clearances. Many experts have advocated minimum targets for creatinine clearance of 50 L per week per 1.73 m2 for patients with low peritoneal membrane transport rates, and 60 L per week per 1.73 m2 for patients with more rapid transport rates. Urea clearance is less affected by residual renal function, the Kt/V urea of 2.0 has been advocated for all CAPD patients (1).
Blood pressure control. As in HD, BP control is important for the long-term well being of PD patients. Many patients on PD are able to discontinue their antihypertensives and maintain a normal BP. This may be attributable to the steady-state volume control achieved by this continuous dialysis modality.
Anemia. Correction of anemia using EPO is important in improving the quality of life for PD patients. EPO is generally administered subcutaneously in PD patients. Adequate correction of anemia can generally be achieved with once or twice weekly injections. The lower overall dose of
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EPO needed to correct the anemia in PD patients, compared with HD patients, reflects the difference in routes of administration (subcutaneous is more effective than intravenous) and the small ongoing blood losses in HD patients.Nutritional aspects. Nutrition is critically important in PD patients. Protein requirements for PD patients are considered to be slightly higher than for HD patients due to the ongoing loss of protein in the spent dialysate. Many patients on PD gain weight over the first 1 year to 18 months. This phenomenon probably results from an increase in fat mass due to excess calorie intake, part of which comes from the high glucose content of the peritoneal dialysate solution. However, long-term PD patients, like HD patients, tend to lose lean body mass. It is unclear how this relates to the adequacy of PD or to underlying inflammatory processes.
Rehabilitation and psychosocial adjustment. Although PD allows individual patients more control over their health care and a more flexible dialysis schedule, the percent of PD patients in the work force and the percent on disability are no different from those on HD. On quality of life questionnaires, PD patients as a group rate their quality of life about the same as HD patients. Unfortunately, no prospective studies are available, and the variability in patient selection is certainly a major factor in these outcomes.
Complications. As in HD, PD has a number of associated complications. They can be divided into infectious and long-term complications. However, unlike HD, inadequate PD tends to result in malnutrition and technique failure, with pericarditis and peripheral neuropathy being less common, although they do occur.
Infectious. Peritonitis remains the most frequent complication of PD. Technical improvements, including disconnect flush before fill systems, have reduced the peritonitis rates in most centers. Most episodes of peritonitis are treatable in the outpatient setting; however, severe infections require hospitalization and occasionally catheter removal. This is particularly true when peritonitis is caused by a fungal infection or Pseudomonas aeruginosa. Exit site infections are also common in PD and usually result from gram-positive organisms. These infections can generally be treated with antibiotics and increased local care. However, some infections, particularly those secondary to Staphylococcus aureus may require catheter removal. Although no consensus on proper exit site care has emerged, most experts agree that the catheter should exit the skin in a downward direction. Tunnel infections usually result from exit site infections and are frequently caused by S. aureus. Early diagnosis is often difficult. An episode of peritonitis, with the same organism causing an exit site infection, may be the presenting symptoms. In some centers, ultrasound has been useful in detecting the fluid around the subcutaneous tunnel that indicates a tunnel infection. Tunnel infections usually necessitate catheter removal.
Long-term complications. Although acute hemodynamic complications are less frequent with PD due to the continuous nature of the technique, cardiovascular disease remains the most common cause of death. Aggressive treatment of lipid abnormalities seems warranted, although outcome studies are not available. Renal osteodystrophy also occurs in PD patients. The morphology is similar to that seen in HD patients, with a slightly higher incidence of adynamic bone disease. 2M amyloid also occurs in PD patients, although theoretically its onset may be delayed due to the higher clearance of 2M by the peritoneal membrane when compared to conventional HD. Acquired renal cystic disease and renal cell cancer appear to have the same increased incidence in PD as in HD. A number of long-term complications are unique to PD. These include a leak of PD fluid from the peritoneal space to
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either the pleural space or into the subcutaneous tissues, resulting in either pleural effusions or hernias, respectively. Sclerosing peritonitis resulting in ultrafiltration failure is an uncommon complication of PD; when it occurs, it is usually in the setting of repeated episodes of peritonitis. A much more common cause of failure of patients on PD is a gradual loss of residual renal function that results in a fall in total clearance, often leading to inadequate dialysis.
Mortality. Despite major advances in renal transplantation and the technology of HD and PD, the diagnosis of ESRD carries an increased mortality compared to age-matched controls. Whereas much of the increased mortality can be related to the underlying medical conditions that resulted in renal failure, some can be directly attributable to the current practice of dialysis and transplantation. Dialysis in any form provides only a very small percent of the clearance achieved by the normal kidneys. Although the hormones produced by the normal kidney, such as erythropoietin and 1,25-dihydroxy vitamin D3 and its analogues, have been available for some time, their optimal use remains to be determined. The appropriate target hemoglobin remains unknown, as does the optimal use of vitamin D analogues and the new calcimimetic agent.
Hemodialysis versus peritoneal dialysis. In the United States, the gross annual mortality among dialysis patients is about 20% to 22%. This figure is 25% to 50% higher than that reported in much of Europe and Japan, and has raised questions about the delivery of dialysis in this country. However, differences in case mix remain a large confounding variable. The risk of death is higher for patients with diabetes as well as those with increasing age. For all age and race groups, the life expectancy on dialysis is significantly shorter than that of the general population. As an example, a white man in the United States, at age 45, has a life expectancy of 32 years compared to white male dialysis patients, whose life expectancy is about 7.4 years. For a black woman, the numbers are similar: normal population 33 years versus dialysis patient 8.4 years (10). However, most studies comparing survival on HD versus PD have found little difference in overall mortality.
Dialysis versus transplantation. There is no doubt that a successful renal transplant improves an individual's quality of life and rehabilitation potential. For diabetic patients and the young, renal transplantation also significantly increases the average life expectancy of those with ESRD.
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