Use Of Biocompatible Membranes Research Articles

The Use of Biocompatible Membranes in Oral Surgery: The Past, Present & Future Directions. A Narrative Review.

The use of biocompatible membranes in periodontal and oral surgery is an important part of regeneration. Over the years, several different membranes have been developed, ranging from non-resorbable membranes that have to be removed in a separate procedure, to collagen membranes that completely resorb on their own, thus avoiding the need for a second surgery. Autogenous membranes are becoming increasingly popular in more recent years. These membranes can be used with a great variety of techniques in the four main hard tissue regenerative procedures: guided tissue regeneration, alveolar ridge preservation, guided bone regeneration and sinus floor augmentation. A review of the literature was conducted in order to identify the most commonly used membranes in clinical practice, as well as the most promising ones for regeneration procedures in the future. The information provided in this review may serve as a guide to clinicians, in order to select the most applicable membrane for the clinical case treated as the correct choice of materials may be critical in the procedure’s success.

Biocompatibility of Polysulfone Hemodialysis Membranes and Its Mechanisms: Involvement of Fibrinogen and Its Integrin Receptors in Activation of Platelets and Neutrophils.

Activation of blood cells during hemodialysis is considered to be a significant determinant of biocompatibility of the hemodialysis membrane because it may affect patient health adversely through microvascular inflammation and oxidative stress. This study found very different cell activation among various polysulfone (PSf) hemodialysis membranes. For example, CX‐U, a conventional PSf membrane, induced marked adhesion of platelets to its surface and increased surface expression of activated CD11b and production of reactive oxygen species (ROS) by neutrophils; while NV‐U, a hydrophilic polymer‐immobilized PSf membrane, caused little platelet adhesion and slight CD11b expression and ROS production by neutrophils. Analysis of the molecular mechanisms of the above phenomena on CX‐U and NV‐U indicated that anti‐integrin GPIIb/IIIa antibody blocked platelet adhesion, and that the combination of anti‐CD11b (integrin α subunit of Mac‐1) and anti‐integrin αvβ3 antibodies blocked ROS production by neutrophils. Plasma‐derived fibrinogen, a major ligand of GPIIb/IIIa, Mac‐1, and αvβ3 on membranes, was thus analyzed and found to be more adsorbed to CX‐U than to NV‐U. Moreover, comparison between five PSf membranes showed that the number of adherent platelets and neutrophil ROS production increased with increasing fibrinogen adsorption. These results suggested that fibrinogen, adsorbed on membranes, induced GPIIb/IIIa‐mediated platelet activation and Mac‐1/αvβ3‐mediated neutrophil activation, depending on the amount of adsorption. In conclusion, the use of biocompatible membranes like NV‐U, which show lower adsorption of fibrinogen, is expected to reduce hemodialysis‐induced inflammation and oxidative stress by minimizing cell activation.

Hemodialysis-related amyloidosis: Is it still relevant?

Accumulation of amyloid fibrils from β2-microglobulin (β2M) was first recognized as a characteristic osteoarticular complication in long-term hemodialysis (HD) patients and called "HD-related amyloidosis" (HRA). However, this syndrome can also be observed in end-stage renal diseases (ESRD) patients undergoing peritoneal dialysis, and even in patients with chronic renal failure before the initiation of dialytic therapy, suggesting that HD is not a direct cause but that accumulation of β2M or some β2M-associated molecules in the body is a common pathogenesis. Currently the term "dialysis-related amyloidosis" (DRA) is widely used for β2M-amyloid (Aβ2M) amyloidosis associated with ESRD, although DRA patients consist mostly of those undergoing long-term HD. Factors other than β2M accumulation also play a role in the formation/local deposition of Aβ2M and disruption of tissue architecture. Conformational changes of β2M by misfolding/unfolding, and promoting/inhibitory effects induced by other coexisting molecules, advanced glycation and oxidation, and direct cell toxicity have also been documented. Two technological improvements of HD have been the keys to prevent the development and progression of DRA: the efficient removal of β2M by using high-flux membranes, high-volume convection and adsorptive column/membrane, as well as the use of biocompatible membranes and dialysates (eg, ultrapure and acetate-free dialysates) have minimized both inflammation and β2M production. Epidemiologically, a decrease in the incidence of DRA has recently been reported; however, longer survival of HD patients may contribute to the development of more DRA, though with a delayed onset. In this article, we describe the pathogenesis of DRA, the strategies developed for its prevention and minimization, and the favorable epidemiological data achieved by these efforts.

Effects of Renal Replacement Therapy on Renal Recovery after Acute Kidney Injury

Recovery of kidney function following an episode of acute kidney injury (AKI) is now acknowledged as a vital patient-centered outcome with clear health economic implications. In approximately 5-8% of critically ill patients with more severe forms of AKI, support with renal replacement therapy (RRT) is provided. Recent data have suggested that rates of RRT utilization in AKI are increasing. Despite advances in our understanding of how best to prescribe acute RRT in critically ill patients with AKI, additional aspects remain uncertain, predisposing to suboptimal delivery and variation in practice. Importantly, if, when, how, and by what principles we apply acute RRT for AKI are all treatment decision-related factors that are modifiable and may interact with recovery of kidney function. Limited data, mostly from observational studies and secondary analyses, have explored the specific association between acute RRT and recovery. Available data are not able to clarify whether providing any RRT in otherwise eligible patients with AKI impacts recovery. They are also unable to inform whether the timing or circumstance under which RRT is started impacts recovery. No studies have evaluated whether there is an optimal time to start RRT to maximize the probability of recovery. Accumulated evidence, mostly derived from observational studies, suggests initial therapy in critically ill patients with AKI with continuous RRT, compared with intermittent modalities, improves the probability of recovery to dialysis independence. Evidence from high-quality randomized trials failed to show any association between delivered dose intensity of RRT and recovery. The use of biocompatible membranes for acute RRT may improve recovery in AKI; however, data are inconsistent. Limited data have evaluated the impact of membrane flux properties on recovery. Preliminary data have suggested that circuit anticoagulation with citrate, which results in a reduction in membrane-induced oxidative stress and leukocyte activation, may be associated with improved recovery; however, further corroborative data are needed. Additional evidence, ideally from randomized trials, is clearly needed to inform best practice in the delivery of acute RRT to optimize probability of recovery of kidney function for survivors of AKI.

Bio-Composite Membrane Electrolytes for Direct Methanol Fuel Cells

A new class of bio-composite polymer electrolyte membranes comprising chitosan (CS) and certain biomolecules in particular, plant hormones such as 3-indole acetic acid (IAA), 4-chlorophenoxy acetic acid (CAA) and 1-naphthalene acetic acid (NAA) are explored to realize proton-conducting bio-composite membranes for application in direct methanol fuel cells (DMFCs). The sorption capability, proton conductivity and ion-exchange capacity of the membranes are characterized in conjunction with their thermal and mechanical behaviour. A novel approach to measure the permeability of the membranes to both water and methanol is also reported, employing NMR imaging and volume localized NMR spectroscopy, using a two compartment permeability cell. A DMFC using CS-IAA composite membrane, operating with 2M aqueous methanol and air at 70°C delivers a peak power density of 25 mW/cm2 at a load current density of 150 mA/cm2. The study opens up the use of bio-compatible membranes in polymer-electrolyte-membrane fuel cells.

Hemodialysis duration impairs food intake and nutritional parameters in chronic kidney disease patients

The aim of this study was to evaluate the effect of hemodialysis (HD) duration on food intake and nutritional markers in patients with chronic kidney disease (CKD). Twenty CKD patients received maintenance HD over a 9-year period. At the beginning of the study (T0) and at 3-year intervals (T1, T2, and T3) during the 9-year follow-up, a nutritional survey using the 24-h recall and record method was repeated for 4 days, and the blood samples were drawn. The results from T0 were used as references. Nutritional status was assessed through food intake, nutritional markers (urea, uric acid, creatinine, cholesterol, total protein, and albumin), and anthropometric measurements (height, dry weight, and body mass index). HD duration was correlated with energy intake (r = -0.89, P < 0.01), protein intake (r = -0.50, P < 0.05), and body mass index (r = -0.50, P < 0.05). Albuminemia decreased over time. Reduced carbohydrate intakes were noted in patients at T1 (-8%), T2 (-38%), and T3 (-59%) with decreased fiber intakes. Lipid intake was diminished by 11, 17, and 25% in patients, respectively, at T1, T2, and T3. The consumption of milk and dairy products, meats, fish, eggs, fruits, vegetables, and fat was reduced at T1, T2, and T3. In conclusion, long-term HD fails to correct undernutrition caused by CKD. Long-term dialysis complications could be reduced with preventive measures, including the use of biocompatible membranes and high-dose dialysis. Consequently, patients could experience a decreased prevalence of protein-energy malnutrition.

Aminothiols and allantoin in chronic dialysis patients: effects of hemodialysis sessions

To investigate the possible relationship between homocysteine and allantoin levels in hemodialyzed patients, serum levels of thiols and purine compounds were analyzed before and after dialysis sessions. 16 clinically stable non-diabetic patients hemodialyzed on polysulfone membranes were compared with 36 control subjects. Serum samples were collected before and after hemodialysis sessions. Total homocysteine, cysteine, glutathione, cysteinylglycine, uric acid, hypoxanthine, and allantoin were measured by capillary electrophoresis. Pre-dialysis homocysteine, allantoin, and uric acid were significantly elevated in dialysis patients as compared to controls. Cysteine, glutathione, and hypoxanthine levels were similar in both groups. Homocysteine significantly decreased, but did not normalize after dialysis sessions. Glutathione and cysteinylglycine levels remained unchanged after dialysis sessions, whereas cysteine decreased. Uric acid, hypoxanthine, and allantoin levels were significantly reduced by dialysis sessions. The allantoin/uric acid ratio was higher in dialyzed patients before hemodialysis (0.049 +/- 0.023 vs. 0.016 +/- 0.012 in controls; p < 0.001), and became elevated after a dialysis session (0.084 +/- 0.033; p = 0.002). Despite the use of biocompatible membranes, homeostasis of thiols and purine compounds is disturbed in hemodialysed patients. We suggest that allantoin could be used as a marker for oxidative stress in hemodialyzed patients.

Biocompatibility and Permeability of Dialyzer Membranes Do Not Affect Anemia, Erythropoietin Dosage or Mortality in Japanese Patients on Chronic Non-Reuse Hemodialysis: A Prospective Cohort Study from the J-DOPPS II Study

Background: Considerable controversy existsover the impact of the biocompatibility and flux characteristics ofdialyzer membranes on anemia in chronic hemodialysis patients. Methods: A subset of 1,207 subjects from the Japanese arm of DOPPS phase II was analyzed. Results: Patient characteristics included mean age 59 years, male sex 60%, BMI 20.6, time on dialysis therapy 7.8 years, and diabetes rate 27%. Dialysis parameters were Kt/V 1.33, and normalized protein catabolic rate 1.05 g/kg/day. Initial hemoglobin level was 10.1 g/dl. 79% were treated by intravenous erythropoietin with mean weekly doses of 4,500 IU. Hemoglobin levels and erythropoietin doses during 2-year study period were not affected by dialysis membrane biocompatibility (unmodified cellulose or biocompatible) or flux (standard or high performance). The 2-year survival rate was 90.9% and was influenced by older age, presence of cardiovascular diseases and amyloidosis, lower levels of BMI and serum albumin, but not by other variables, including dialysis membranes. Use of biocompatible membranes was associated with a lower all-cause mortality (8.3 vs. 13.0% for bioincompatible, p = 0.037), but this difference was not significant in multivariate analyses (hazard ratio 0.70, p = 0.17 by Cox multivariate analysis). Conclusion: The biocompatibility and permeability of dialyzer membranes had no effect on anemia, erythropoietin dosage or all-cause mortality in Japanese chronic hemodialysis patients treated by non-reuse dialysis.

The Impact of Hypertension in Hemodialysis Patients

Although the large majority of patients with end-stage renal disease are hypertensive, blood pressure levels are insufficiently controlled despite the complex pharmacological treatment they receive. Hypertension is known to be associated with cardiovascular complications, but its impact on mortality is still controversial. The paradox of “reverse epidemiology”, i.e. better survival of dialysis patients with high blood pressure levels, is common to other patients, such as those with heart failure, and is linked to the left ventricular abnormalities that are found in many hemodialysis (HD) patients. Moreover, unlike epidemiological studies on the general population, observational surveys on HD patients have been performed for shorter periods of time. After correction for confounders and over the long-term, hypertension seems to be an independent risk factor for mortality in HD patients and is multi-factorial in origin. Several causes are recognized: volume overload, sympathetic hyperactivity, activation of the renin angiotensin system, vascular calcification and erythropoietin treatment. The optimal blood pressure target seems to be pre-dialysis values of 140/90 mmHg, or the lowest possible values which are well tolerated during the dialysis session. The best method for assessing blood pressure levels remains to be established, because of oscillations in relation to the dialysis session or the inter-dialysis period. Home blood pressure measurement seems to be as sensitive as ambulatory blood pressure monitoring; alternatively the average of 12 predialysis measurements has been used. Drug treatment is unsatisfactory, and difficult kinetics and side effects are often reported. Several non pharmacological options are available, such as modifications to the hemodialysis schedule, increased HD efficiency, and use of biocompatible membranes, besides dietary salt and fluid restriction. A correct approach to HD can efficiently reduce the incidence of hypertension, cardiovascular complications and mortality rate in these patients.

Biocompatible hemodialysis membranes for acute renal failure

Acute renal failure (ARF) is associated with substantial morbidity and mortality. Some studies have reported a survival advantage among patients dialyzed with biocompatible membranes (BCM) compared to bioincompatible membranes (BICM). These findings were not consistently observed in subsequent studies. To ascertain whether the use of BCM confers an advantage in either survival or recovery of renal function over the use of BICM in adult patients with ARF requiring intermittent hemodialysis. We searched the Cochrane Central Register of Controlled Trials (CENTRAL, in The Cochrane Library), MEDLINE (from 1966), EMBASE (from 1980), the Mexican Index of Latin American Biomedical Journals IMBIOMED (from 1990), the Latin American and Caribbean Health Sciences Literature Database LILACS (from 1982), and reference lists of articles. Search date: January 2007 Randomized and quasi-randomized controlled trials comparing the use of a BCM with a BICM in patients > 18 years of age with ARF requiring intermittent hemodialysis. Two authors extracted the data independently. Cellulose-derived dialysis membranes were classified as BICM, and synthetic dialyzers were considered as BCM. The main outcomes were all-cause mortality and recovery of renal function by type of dialyzer. We further explored these outcomes according to the flux properties (high-flux or low-flux) of each of these dialyzers. A meta-analysis was conducted by combining data using a random-effects model. Ten studies were included in the primary analysis of mortality, with a total of 1100 patients. None of the pooled risk ratios (RRs) reached statistical significance. The pooled RR for mortality was 0.93 (95% confidence interval (CI) 0.81 to 1.07). The overall RR for recovery of renal function, which was inclusive of 1038 patients from nine studies, was 1.09 (95% CI 0.90 to 1.31). The pooled RR for mortality by dialyzer flux property was 1.05 (95% CI 0.81 to 1.37). The pooled RR for recovery of renal function by flux property was 1.30 (95% CI 0.83 to 2.02). A meta-analysis of mortality among kidney transplant recipients was not possible, however the analysis of recovery of renal function in this patient population revealed an RR of 1.05 (95% CI 0.87 to 1.26). Results of sensitivity analyses did not differ significantly from the primary analyses. There is no demonstrable clinical advantage to the use of BCM versus BICM in patients with ARF who require intermittent hemodialysis.

Nerve Conduction Studies and Prediction of Mortality in Hemodialysis Patients

Background. The electrophysiological aspects of uremic neuropathy have been studied extensively, but never for prediction of mortality. In order to assess the parameters of nerve conduction study (NCS) as predictors of mortality in hemodialysis patients, a post hoc analysis of a prospective observation study was made. Methods. We examined conventional electrophysiological parameters (motor nerve conduction velocity [MCV], terminal latency [TL], and F wave latency of the peroneal nerve, as well as sensory nerve conduction velocity [SCV] of the sural nerve) in 75 nondiabetic patients. Hemodialysis modality (bicarbonate dialysis and biocompatible membranes), Kt/V, comorbidity (ischemic heart disease and congestive heart failure), and clinical and laboratory parameters were also evaluated. Survival was analyzed using the Cox proportional hazard model. Results. SCV was significantly higher (t-test, p < 0.01) in the group of patients treated with polysulfone compared to those using cuprophane membranes. On the other hand, MCV significantly correlated with Kt/V (Pearson, r = 0.388; p < 0.01). Multivariate Cox regression revealed only MCV as a significant predictor of mortality in this group of hemodialysis patients (HR = 0.92; CI (0.86–0.99); p < 0.05). Conclusion. Only MCV was a significant mortality risk predictor among NCS parameters. This parameter correlates significantly with dialysis dose. SCV was related to the use of biocompatible membranes, indicating the complexity of polyneuropathy in dialysis patients.

Erythropoiesis‐stimulating agent hyporesponsiveness (Review Article)

Approximately 5-10% of patients with chronic kidney disease demonstrate hyporesponsiveness to erythropoiesis-stimulating agents (ESA), defined as a continued need for greater than 300 IU/kg per week erythropoietin or 1.5 mug/kg per week darbepoetin administered by the subcutaneous route. Such hyporesponsiveness contributes significantly to morbidity, mortality and health-care economic burden in chronic kidney disease and represents an important diagnostic and management challenge. The commonest causes of ESA resistance are non-compliance, absolute or functional iron deficiency and inflammation. It is widely accepted that maintaining adequate iron stores, ideally by administering iron parenterally, is the most important strategy for reducing the requirements for, and enhancing the efficacy of ESA. There have been recent epidemiologic studies linking parenteral iron therapy to an increased risk of infection and atherosclerosis, although other investigations have refuted this. Inflammatory ESA hyporesponsiveness has been reported to be improved by a number of interventions, including the use of biocompatible membranes, ultrapure dialysate, transplant nephrectomy, ascorbic acid therapy, vitamin E supplementation, statins and oxpentifylline administration. Other variably well-established causes of ESA hyporesponsiveness include inadequate dialysis, hyperparathyroidism, nutrient deficiencies (vitamin B12, folate, vitamin C, carnitine), angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, aluminium overload, antibody-mediated pure red cell aplasia, primary bone marrow disorders, myelosuppressive agents, haemoglobinopathies, haemolysis and hypersplenism. This paper reviews the causes of ESA hyporesponsiveness and the clinical evidence for proposed therapeutic interventions. A practical algorithm for approaching the investigation and management of patients with ESA hyporesponsiveness is also provided.

Evolving Practices in Critical Care and Potential Implications for Management of Acute Kidney Injury

Acute kidney injury (AKI) is a common complication in hospitalized patients, with an incidence of 3 to 10% (1–4). In-hospital mortality rates that are associated with AKI remain high, in the range of 30 to 70% (5–8), despite significant improvements in dialytic technology as well as important advances in critical care, which have resulted in improved survival for other critical illnesses, including acute lung injury and sepsis (9). These improvements include continuous renal replacement therapies, which allow for continuous removal of solutes and fluid and may be tolerated better from a hemodynamic standpoint, and biocompatible dialysis membranes, which are associated with reduced complement and granulocyte activation. In general, indications for dialysis in the acute care setting have been extrapolated from those that are applied in chronic kidney disease, including volume overload that is refractory to diuretic therapy; electrolyte abnormalities (in particular hyperkalemia); uremic complications (pericarditis or pleuritis); severe acidosis (pH < 7.20); and selected toxic ingestions, such as methanol, ethylene glycol, and other water-soluble agents (10,11). However, the evidence base supporting specific dialysis practices in the acute care setting is limited. For example, several studies that were completed in the 1960s and 1970s compared “early” and “late” initiation of dialysis, using blood urea nitrogen (BUN) to define early and late (Table 1). These studies primarily were cohort studies that used historical controls, not randomized, clinical trials. The results of these investigations, along with extrapolation from the ESRD population, promoted recent practice patterns. Currently, many nephrologists often delay dialysis in the acute care setting until the patient has an impending complication of AKI, such as hyperkalemia leading to cardiac arrhythmias, acidosis resulting in hypotension, or oliguria leading to volume overload or hypoxemia, or until the BUN exceeds 100 mg/dl (18). Given differences in protein catabolism, …

The health assurance coaching model for chronic renal disease management.

This article presents a coach-player approach to the care of patients with chronic renal disease (CRD) that evokes patients’ motivation toward self-maintaining behaviors and informed, competent, and confident selfcare. In operation, it is superior to our conventional directive and prescriptive styles of patient caregiving because self-evidently it assures each patient’s continuous access to consistent high-quality care at lower cost because of predictably reduced use of health care resources. Grounded on evidence-based disease management and generically applicable to virtually all chronic medical disease, health assurance coaching should specifically focus on reducing both the morbidity risks among pre– end stage CRD patients and, as a consequence, cause a significant reduction in the current, unacceptable rates of morbidity and mortality of end-stage renal disease (ESRD) patients. It is generally agreed that our dialyzed ESRD patients’ current rates of morbidity and mortality, and therefore their health care costs, are too high. The principal, alleged causes, including late referral to a nephrologist of already uremic patients, late initiation of dialysis, underdialysis, and undernutrition, are being addressed, respectively, by educational countermeasures in the literature; increasing amounts of dialysis; and use of biocompatible membranes, erythropoietin, intradialytic alimentation, and dietetic coun

Extracorporeal Treatment Strategy in Acute Renal Failure

The mortality of acute renal failure remains high (around 50-70%) despite manifold improvements in terms of techniques and equipment for renal replacement therapies as well as patient monitoring and intensive care support. At present, it is not clear if the method chosen for renal replacement therapy, i.e. intermittent hemodialysis or continuous hemofiltration, might impact on the outcome of these patients. Whilst earlier retrospective studies suggested that CVVH might result in better survival and renal recovery in acute patients, recent prospective studies indicated that this may not be the case or, conversely, outcomes may be better with IHD. These studies were, however, not evenly randomised in terms of illness severity or were too small to produce conclusive results. In addition, a meta-analysis of 9 published prospective studies in 692 pts. indicated a similar mortality with CVVH vs. IHD. Some of the studies enrolled for this meta-analysis, however, suffered from methodological and/or randomisation problems, thus this important question remains to date unanswered. Typically, CVVH is chosen for treating patients with hemodynamic instability and volume overload. In such cases, however, CVVH should be performed with a filtrate volume of at least 35 ml/kg body weight per hour as this was shown to be associated with better survival as compared to smaller filtrate volumes. A second controversy exists to date whether the choice of the dialyzer membrane might be of relevance for the outcome of patients with acute renal failure. Earlier studies indicated that the use of biocompatible membranes in these patients may result in improved patient survival and renal recovery. More recently, however, similar studies could not confirm these results. Another meta-analysis of controlled prospective trials (671 patients in 7 separate studies) calculated a relative mortality risk of 1.01 for cuprophan vs. biocompatible membranes. Thus, the choice of the dialyzer membrane should be based on individual assessment rather than treatment bias.

Effect of hemodialysis on the oxidative stress and antioxidants.

Oxidative stress plays a role in many disease states. These diseases have an increased incidence in uremia, and particularly in hemodialysis (HD) patients. This suggests an increased exposure to oxidative stress. An imbalance between oxidants and antioxidants has been suggested in uremic patients on HD. However, the respective influence of uremia and dialysis procedure has not been evaluated. It is postulated that antioxidant capacity in uremic patients is reduced, yet the mechanism remains unclear. We have determined the levels of lipid peroxidation expressed as thiobarbituric acid-reactive substances. We assessed oxidative protein damage by carbonyl content and activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) in predialysis uremic patients and in end-stage renal disease (ESRD) patients before and after hemodialysis. Vitamin E and vitamin C levels, reduced glutathione and sulfhydryl content were also studied. We found enhanced oxidative stress in ESRD patients undergoing HD and in predialysis uremic patients. This was mostly due to defective antioxidant enzyme levels. Preventive modalities, including use of biocompatible membranes, ultrapure dialysate, exogenous supplementation of antioxidant vitamins, extracorporeal removal of reactive oxygen species (ROS) and oxidatively modified substances, would appear highly desirable to reduce complications in the long-term dialysis patients.

Biocompatible membranes do not promote graft recovery following cadaveric renal transplantation

Controversy surrounds the role of biocompatible membrane dialyzers in treatment of acute renal failure. Studies that have shown a benefit have involved critically ill patients where renal recovery and patient mortality are influenced by other comorbid disease. The aim of the present work is to clarify this issue in a more homogeneous population of patients with acute renal failure following cadaveric renal transplantation. All patients with delayed graft function between January 1996 and February 1998 were randomized to receive either a biocompatible (BCM, polysulfone) membrane or bioincompatible (BICM, cuprophane) membrane for dialysis until onset of graft function. Forty-one patients were randomized, 23 to receive BCM and 18 BICM. Five patients (2 BCM, 3 BICM; p = NS) with primary non-function of graft were excluded from analysis, leaving 36 cases of acute tubular necrosis (ATN). Patient and donor characteristics were similar in both groups. The BCM group had significantly longer periods of dialysis dependency compared to the BICM group (14 vs 10 days; p = 0.03). There was a tendency towards higher serum creatinine levels in the short term in the BCM group (318 vs 164 micromol/l at 1 month (p = 0.1), 190 vs 169 micromol/l at latest visit (p = 0.07)) and a greater number of acute rejection episodes in the BCM group (3.7 vs 1.7 episodes per 100 days of dialysis dependency, p = 0.1). With an intention-to-treat analysis of all 41 patients originally randomized, there was no significant difference in time to graft recovery between the 2 groups (p = 0.18). In the setting of ARF posttransplantation, we have found no evidence to support the use of biocompatible membranes for dialysis. Rather, our study provides argument against a large benefit for the use of BCM in the recovery of ARF, as suggested by earlier studies.

Clinical impact of residual renal function on patients starting dialysis treatment.

We describe our clinical experience of monitoring residual renal function of patients on regular dialysis treatment as residual renal function can play an important role in the management of patients undergoing regular dialysis. With active residual renal function it is possible to delay the start of haemodialytic programmes. In managing dialysis treatments, it is important to maintain residual renal function by preventing hypotensive events. It is known that in acute renal failure intradialytic hypotension is able to reduce the recovery of renal function. Out patient follow-up plays an important role for these patients. This paper will also discuss the use of biocompatible membranes during dialysis. The outcome is that they are not associated with better maintenance of residual renal function.

Treatment of acute renal failure--concepts and controversies. 2. Extracorporeal renal replacement and peritoneal dialysis

Therapy of prolonged acute renal failure regularly requires a renal replacement therapy. This can be achieved by different extracorporal renal replacement therapies (ERRT) or by peritoneal dialysis. ERRT are classified according to the physical principle underlying toxin elimination as hemodialysis (diffusion) and hemofiltration (convection). Another classification refers to intermittent or continuous application modes. Biocompatibility of membranes is judged according to their activation of the complement system. Prospective randomized studies did not consolidate the assumptions about the benefit of particular modalities proposed on theoretical foundations. Mortality, duration and complication rates of acute renal failure are not significantly decreased by use of biocompatible membranes. Continuous modalities are not generally preferable but optimize treatment in hemodynamically unstable patients, in whom they endorse fluid balancing and maintenance of sufficient arterial blood pressure. The use of demanding hemofiltration techniques for cytokine removal should be limited to clinical studies. The effects of ERRT-"intensity" and the best timing for initiation of ERRT have not been evaluated sufficiently. The choice of the ERRT modality is subject to clinical judgement (criterion: hemodynamic situation), practical aspects (criteria: availability of equipment and handling experience), and costs. Prior to their general use new and expensive technical modalities and membrane types should be thoroughly evaluated in studies with regard to outcome-related aspects such as patient survival and preservation of renal function.

Increased reduction of dimethylarginines and lowered interdialytic blood pressure by the use of biocompatible membranes

Hypertension contributes to cardiac and cerebrovascular complications in HD patients. Endogenous inhibitors of nitric oxide synthase accumulate in renal failure and may interfere with the regulation of vascular tone. We investigated the elimination of asymmetric dimethylarginine (ADMA) by using biocompatible Polyamide Strade mark membranes in low-flux (Polyflux 6L) or high-flux (Polyflux 14S) hemodialysis or hemodiafiltration (HDF) compared with hemodialysis with cellulosic membranes. Removal rates for ADMA, symmetric dimethylarginine (SDMA), and beta2-microglobulin significantly increased in HDF. The plasma total amino acid concentration and the arginine/ADMA ratio increased, and the mean 24-hour blood pressure decreased during the study. In a second study, we investigated whether plasma amino acids and interdialytic blood pressure are influenced by the use of a biocompatible membrane and HDF. Seventeen end-stage renal disease patients were treated for six weeks with hemodialysis using cellulosic membranes, six weeks with low-flux hemodialysis using Polyflux 6L, and six weeks with HDF using Polyflux 14S. Only in the diabetic patients were the hemoglobin concentration (from 10.6 +/- 1.5 to 11.9 +/- 0.6 mg/dL) and hematocrit (from 33.6 +/- 1.9 to 36.2 +/- 1.5%) increased significantly, whereas the mean 24-hour systolic blood pressure decreased (from 154 +/- 22 to 129 +/- 18 mm Hg). No significant changes were observed in nondiabetic patients. We conclude that primarily diabetic patients seem to benefit from the use of biocompatible membranes--most in HDF--after a period of six weeks. The regulation of nitric oxide pathways by ADMA removal and changed ADMA/arginine ratio might be contributing factors. Further prospective studies are required to show whether the long-term application of HDF or other changes of dialysis treatment modalities may help to improve well-being, morbidity, and mortality in hemodialysis patients.