High-flux dialyzers, backfiltration, and dialysis fluid quality

Is hemodiafiltration superior to high-flow hemodialysis in reducing all-cause and cardiovascular mortality in kidney failure patients? A meta-analysis of randomized controlled trials

INTRODUCTION

Hemodiafiltration (HDF) and high-flux hemodialysis (hf-HD) are different methods of kidney replacement therapy (KRT) used for the treatment of kidney failure patients. A debate has raged over the last decade about the survival benefit of patients with the use of HDF compared with hf-HD, but with divergent results from randomized controlled trials. Therefore, this study aimed to perform a meta-analysis to compare HDF and hf-HD regarding all-cause and cardiovascular mortality.

METHODS

PubMed and Cochrane databases were searched until July 19, 2023, for randomized clinical trials comparing HDF and hf-HD in patients on maintenance dialysis. A meta-analysis was performed using Stata 16.1, applying fixed or random effect models according to the heterogeneity between studies.

FINDINGS

Of the 496 studies found, five met the inclusion criteria. Compared with the hf-HD group, the risk ratio (RR) for all-cause mortality with HDF use was 0.76 (95% CI: 0.67-0.88, I2 = 0%). HDF was associated with lower cardiovascular mortality, although the sensitivity analysis showed that the result differed between scenarios. Subgroup analysis showed lower all-cause mortality among patients without diabetes in the HDF group compared with hf-HD (RR 0.66, 95% CI: 0.51-0.81, I2 = 0%), but not in diabetic patients (RR = 0.89, 95% CI: 0.65-1.12, I2 = 0.0%). A subgroup analysis considering convection volumes was not performed, but the studies with the highest weight in the meta-analysis described convection volume as more than 20 L/session.

DISCUSSION

More clinical studies considering critical risk factors, such as advanced age and preexisting cardiovascular disease, are needed to confirm the supremacy of HDF over hf-HD on the survival of patients treated by these two forms of kidney replacement therapy.

An update review on hemodynamic instability in renal replacement therapy patients

BACKGROUND

Hemodynamic instability in patients undergoing kidney replacement therapy (KRT) is one of the most common and essential factors influencing mortality, morbidity, and the quality of life in this patient population.

METHOD

Decreased cardiac preload, reduced systemic vascular resistance, redistribution of fluids, fluid overload, inflammatory factors, and changes in plasma osmolality have all been implicated in the pathophysiology of hemodynamic instability associated with KRT.

RESULT

A cascade of these detrimental mechanisms may ultimately cause intra-dialytic hypotension, reduced tissue perfusion, and impaired kidney rehabilitation. Multiple parameters, including dialysate composition, temperature, posture during dialysis sessions, physical activity, fluid administrations, dialysis timing, and specific pharmacologic agents, have been studied as possible management modalities. Nevertheless, a clear consensus is not reached.

CONCLUSION

This review includes a thorough investigation of the literature on hemodynamic instability in KRT patients, providing insight on interventions that may potentially minimize factors leading to hemodynamic instability.

Blood-incompatibility in haemodialysis: alleviating inflammation and effects of coagulation

Blood-incompatibility is an inevitability of all blood-contacting device applications and therapies, including haemodialysis (HD). Blood leaving the environment of blood vessels and the protection of the endothelium is confronted with several stimuli of the extracorporeal circuit (ECC), triggering the activation of blood cells and various biochemical pathways of plasma. Prevention of blood coagulation, a major obstacle that needed to be overcome to make HD possible, remains an issue to contend with. While anticoagulation (mainly with heparin) successfully prevents clotting within the ECC to allow removal of uraemic toxins across the dialysis membrane wall, it is far from ideal, triggering heparin-induced thrombocytopenia in some instances. Soluble fibrin can form even in the presence of heparin and depending on the constitution of the patient and activation of platelets, could result in physical clots within the ECC (e.g. bubble trap chamber) and, together with other plasma and coagulation proteins, result in increased adsorption of proteins on the membrane surface. The buildup of this secondary membrane layer impairs the transport properties of the membrane to reduce the clearance of uraemic toxins. Activation of complement system-dependent immune response pathways leads to leukopenia, formation of platelet–neutrophil complexes and expression of tissue factor contributing to thrombotic processes and a procoagulant state, respectively. Complement activation also promotes recruitment and activation of leukocytes resulting in oxidative burst and release of pro-inflammatory cytokines and chemokines, thereby worsening the elevated underlying inflammation and oxidative stress condition of chronic kidney disease patients. Restricting all forms of blood-incompatibility, including potential contamination of dialysis fluid with endotoxins leading to inflammation, during HD therapies is thus still a major target towards more blood-compatible and safer dialysis to improve patient outcomes. We describe the mechanisms of various activation pathways during the interaction between blood and components of the ECC and describe approaches to mitigate the effects of these adverse interactions. The opportunities to develop improved dialysis membranes as well as implementation strategies with less potential for undesired biological reactions are discussed.

Choices in hemodialysis therapies: variants, personalized therapy and application of evidence-based medicine

The extent of removal of the uremic toxins in hemodialysis (HD) therapies depends primarily on the dialysis membrane characteristics and the solute transport mechanisms involved. While designation of ‘flux’ of membranes as well toxicity of compounds that need to be targeted for removal remain unresolved issues, the relative role, efficiency and utilization of solute removal principles to optimize HD treatment are better delineated. Through the combination and intensity of diffusive and convective removal forces, levels of concentrations of a broad spectrum of uremic toxins can be lowered significantly and successfully. Extended clinical experience as well as data from several clinical trials attest to the benefits of convection-based HD treatment modalities. However, the mode of delivery of HD can further enhance the effectiveness of therapies. Other than treatment time, frequency and location that offer clinical benefits and increase patient well-being, treatment- and patient-specific criteria may be tailored for the therapy delivered: electrolytic composition, dialysate buffer and concentration and choice of anticoagulating agent are crucial for dialysis tolerance and efficacy. Evidence-based medicine (EBM) relies on three tenets, i.e. clinical expertise (i.e. doctor), patient-centered values (i.e. patient) and relevant scientific evidence (i.e. science), that have deviated from their initial aim and summarized to scientific evidence, leading to tyranny of randomized controlled trials. One must recognize that practice patterns as shown by Dialysis Outcomes and Practice Patterns Study and personalization of HD care are the main driving force for improving outcomes. Based on a combination of the three pillars of EBM, and particularly on bedside patient–clinician interaction, we summarize what we have learned over the last 6 decades in terms of best practices to improve outcomes in HD patients. Management of initiation of dialysis, vascular access, preservation of kidney function, selection of biocompatible dialysers and use of dialysis fluids of high microbiological purity to restrict inflammation are just some of the approaches where clinical experience is vital in the absence of definitive scientific evidence. Further, HD adequacy needs to be considered as a broad and multitarget approach covering not just the dose of dialysis provided, but meeting individual patient needs (e.g. fluid volume, acid–base, blood pressure, bone disease metabolism control) through regular assessment—and adjustment—of a series of indicators of treatment efficiency. Finally, in whichever way new technologies (i.e. artificial intelligence, connected health) are embraced in the future to improve the delivery of dialysis, the human dimension of the patient–doctor interaction is irreplaceable. Kidney medicine should remain ‘an art’ and will never be just ‘a science’.

Clinical relevance of abstruse transport phenomena in haemodialysis

Haemodialysis (HD) utilizes the bidirectional properties of semipermeable membranes to remove uraemic toxins from blood while simultaneously replenishing electrolytes and buffers to correct metabolic acidosis. However, the nonspecific size-dependent transport across membranes also means that certain useful plasma constituents may be removed from the patient (together with uraemic toxins), or toxic compounds, e.g. endotoxin fragments, may accompany electrolytes and buffers of the dialysis fluids into blood and elicit severe biological reactions. We describe the mechanisms and implications of these undesirable transport processes that are inherent to all HD therapies and propose approaches to mitigate the effects of such transport. We focus particularly on two undesirable events that are considered to adversely affect HD therapy and possibly impact patient outcomes. Firstly, we describe how loss of albumin (and other essential substances) can occur while striving to eliminate larger uraemic toxins during HD and why hypoalbuminemia is a clinical condition to contend with. Secondly, we describe the origins and mode of transport of biologically active substances (from dialysis fluids with bacterial contamination) into the blood compartment and biological reactions they elicit. Endotoxin fragments activate various proinflammatory pathways to increase the underlying inflammation associated with chronic kidney disease. Both phenomena involve the physical as well as chemical properties of membranes that must be selected judiciously to balance the benefits with potential risks patients may encounter, in both the short and long term.

Multitargeted interventions to reduce dialysis-induced systemic stress

Hemodialysis (HD) is a life-sustaining therapy as well as an intermittent and repetitive stress condition for the patient. In ridding the blood of unwanted substances and excess fluid from the blood, the extracorporeal procedure simultaneously induces persistent physiological changes that adversely affect several organs. Dialysis patients experience this systemic stress condition usually thrice weekly and sometimes more frequently depending on the treatment schedule. Dialysis-induced systemic stress results from multifactorial components that include treatment schedule (i.e. modality, treatment time), hemodynamic management (i.e. ultrafiltration, weight loss), intensity of solute fluxes, osmotic and electrolytic shifts and interaction of blood with components of the extracorporeal circuit. Intradialytic morbidity (i.e. hypovolemia, intradialytic hypotension, hypoxia) is the clinical expression of this systemic stress that may act as a disease modifier, resulting in multiorgan injury and long-term morbidity. Thus, while lifesaving, HD exposes the patient to several systemic stressors, both hemodynamic and non-hemodynamic in origin. In addition, a combination of cardiocirculatory stress, greatly conditioned by the switch from hypervolemia to hypovolemia, hypoxemia and electrolyte changes may create pro-arrhythmogenic conditions. Moreover, contact of blood with components of the extracorporeal circuit directly activate circulating cells (i.e. macrophages-monocytes or platelets) and protein systems (i.e. coagulation, complement, contact phase kallikrein-kinin system), leading to induction of pro-inflammatory cytokines and resulting in chronic low-grade inflammation, further contributing to poor outcomes. The multifactorial, repetitive HD-induced stress that globally reduces tissue perfusion and oxygenation could have deleterious long-term consequences on the functionality of vital organs such as heart, brain, liver and kidney. In this article, we summarize the multisystemic pathophysiological consequences of the main circulatory stress factors. Strategies to mitigate their effects to provide more cardioprotective and personalized dialytic therapies are proposed to reduce the systemic burden of HD.

Mechanisms for hemodynamic instability related to renal replacement therapy: a narrative review

Hemodynamic instability related to renal replacement therapy (HIRRT) is a frequent complication of all renal replacement therapy (RRT) modalities commonly used in the intensive care unit. HIRRT is associated with increased mortality and may impair kidney recovery. Our current understanding of the physiologic basis for HIRRT comes primarily from studies of end-stage kidney disease patients on maintenance hemodialysis in whom HIRRT is referred to as ‘intradialytic hypotension’. Nonetheless, there are many studies that provide additional insights into the underlying mechanisms for HIRRT specifically in critically ill patients. In particular, recent evidence challenges the notion that HIRRT is almost entirely related to excessive ultrafiltration. Although excessive ultrafiltration is a key mechanism, multiple other RRT-related mechanisms may precipitate HIRRT and this could have implications for how HIRRT should be managed (e.g., the appropriate response might not always be to reduce ultrafiltration, particularly in the context of significant fluid overload). This review briefly summarizes the incidence and adverse effects of HIRRT and reviews what is currently known regarding the mechanisms underpinning it. This includes consideration of the evidence that exists for various RRT-related interventions to prevent or limit HIRRT. An enhanced understanding of the mechanisms that underlie HIRRT, beyond just excessive ultrafiltration, may lead to more effective RRT-related interventions to mitigate its occurrence and consequences.

Prescribing Hemodialysis or Hemodiafiltration: When One Size Does Not Fit All the Proposal of a Personalized Approach Based on Comorbidity and Nutritional Status

There is no simple way to prescribe hemodialysis. Changes in the dialysis population, improvements in dialysis techniques, and different attitudes towards the initiation of dialysis have influenced treatment goals and, consequently, dialysis prescription. However, in clinical practice prescription of dialysis still often follows a "one size fits all" rule, and there is no agreed distinction between treatment goals for the younger, lower-risk population, and for older, high comorbidity patients. In the younger dialysis population, efficiency is our main goal, as assessed by the demonstrated close relationship between depuration (tested by kinetic adequacy) and survival. In the ageing dialysis population, tolerance is probably a better objective: "good dialysis" should allow the patient to attain a stable metabolic balance with minimal dialysis-related morbidity. We would like therefore to open the discussion on a personalized approach to dialysis prescription, focused on efficiency in younger patients and on tolerance in older ones, based on life expectancy, comorbidity, residual kidney function, and nutritional status, with particular attention placed on elderly, high-comorbidity populations, such as the ones presently treated in most European centers. Prescription of dialysis includes reaching decisions on the following elements: dialysis modality (hemodialysis (HD) or hemodiafiltration (HDF)); type of membrane (permeability, surface); and the frequency and duration of sessions. Blood and dialysate flow, anticoagulation, and reinfusion (in HDF) are also briefly discussed. The approach described in this concept paper was developed considering the following items: nutritional markers and integrated scores (albumin, pre-albumin, cholesterol; body size, Body Mass Index (BMI), Malnutrition Inflammation Score (MIS), and Subjective Global Assessment (SGA)); life expectancy (age, comorbidity (Charlson Index), and dialysis vintage); kinetic goals (Kt/V, normalized protein catabolic rate (n-PCR), calcium phosphate, parathyroid hormone (PTH), beta-2 microglobulin); technical aspects including vascular access (fistula versus catheter, degree of functionality); residual kidney function and weight gain; and dialysis tolerance (intradialytic hypotension, post-dialysis fatigue, and subjective evaluation of the effect of dialysis on quality of life). In the era of personalized medicine, we hope the approach described in this concept paper, which requires validation but has the merit of providing innovation, may be a first step towards raising attention on this issue and will be of help in guiding dialysis choices that exploit the extraordinary potential of the present dialysis "menu".

What the non-nephrologist needs to know about dialysis

The End-Stage Renal Disease (ESRD) program now serves approximately 675,000 individuals in the United States at a cost of $26.1 billion to the Medicare system. Given the size of this population, healthcare providers from all disciplines will deliver care to patients on dialysis. Mortality remains high among patients on chronic dialysis, with 42.3% surviving 5 years. As this is a vulnerable population, it is important in the care of ESRD patients that non-nephrologists have a working knowledge of issues germane to dialysis. This review examines the physiology, mechanics, complications, and care delivery concerns of kidney dialysis modalities relevant to the non-nephrologist. The majority of patients receive in-center hemodialysis thrice weekly, with a small proportion on home-based therapies such as peritoneal dialysis or home hemodialysis. Inpatients may undergo hemodialysis or peritoneal dialysis, and in critically ill patients, continuous renal replacement therapies are utilized. Practical aspects of each of these modalities are discussed.

Prognostic effect of high-flux hemodialysis in patients with chronic kidney disease

We investigated the prognostic effects of high-flux hemodialysis (HFHD) and low-flux hemodialysis (LFHD) in patients with chronic kidney disease (CKD). Both an electronic and a manual search were performed based on our rigorous inclusion and exclusion criteria to retrieve high-quality, relevant clinical studies from various scientific literature databases. Comprehensive meta-analysis 2.0 (CMA 2.0) was used for the quantitative analysis. We initially retrieved 227 studies from the database search. Following a multi-step screening process, eight high-quality studies were selected for our meta-analysis. These eight studies included 4967 patients with CKD (2416 patients in the HFHD group, 2551 patients in the LFHD group). The results of our meta-analysis showed that the all-cause death rate in the HFHD group was significantly lower than that in the LFHD group (OR=0.704, 95%CI=0.533-0.929, P=0.013). Additionally, the cardiovascular death rate in the HFHD group was significantly lower than that in the LFHD group (OR=0.731, 95%CI=0.616-0.866, P<0.001). The results of this meta-analysis clearly showed that HFHD decreases all-cause death and cardiovascular death rates in patients with CKD and that HFHD can therefore be implemented as one of the first therapy choices for CKD.

Spin-coated Au-nanohole arrays engineered by nanosphere lithography for a Staphylococcus aureus 16S rRNA electrochemical sensor

The nanopatterning of gold nanoparticle (AuNP) arrays on an indium tin oxide (ITO) electrode using efficient and low-cost methods is described. This process used nanosphere lithography (NSL) encompassing the deposition of monolayered Polystyrene (PS) followed by a convective self-assembly drop coating protocol onto the ITO substrate that further acted as the mask after the AuNP assembly. The results showed that spin-coating allowed AuNPs to follow the contour and adhere to the PS nanospheres. The final products, after etching the PS, generated a highly ordered Au-nanohole array on an ITO substrate. The Au-nanohole arrays on the ITO electrode provided a greater surface area and successfully enhanced the peak current of electrochemical measurements by 82% compared with bare ITO and was used to detect Staphylococcus aureus 16S rRNA hybridization. In contrast to non-templated AuNP structures, the Au-nanohole arrays on the ITO electrode contributed to an optimum sensitivity improvement in DNA hybridization detection by 23%, along with an impressive limit of detection (LOD) of 10 pM. The high specificity of this distinguished structure was also achieved in the hybridization measurements of multi-analyte pathogens. These findings indicate that the combination of PS nanosphere lithography, followed by the spin-coating of AuNPs, leads to an inexpensive and simple engineering process that effectively generates uniform Au-nanohole arrays on ITO, which provides a greater surface area to optimize the electrochemical performance of the DNA biosensor.

Dialyzer Reuse and Outcomes of High Flux Dialysis

Background

The bulk of randomized trial evidence for the expanding use of High Flux (HF) hemodialysis worldwide comes from two randomized controlled trials, one of which (HEMODIALYSIS, HEMO) allowed, while the other (Membrane Outcomes Permeability, MPO) excluded, the reuse of membranes. It is not known whether dialyzer reuse has a differential impact on outcomes with HF vs low flyx (LF) dialyzers.

Methods

Proportional Hazards Models and Joint Models for longitudinal measures and survival outcomes were used in HEMO to analyze the relationship between β2-microglobulin (β2M) concentration, flux, and reuse. Meta-analysis and regression techniques were used to synthesize the evidence for HF dialysis from HEMO and MPO.

Findings

In HEMO, minimally reused (< 6 times) HF dialyzers were associated with a hazard ratio (HR) of 0.67 (95% confidence interval, 95%CI: 0.48–0.92, p = 0.015), 0.64 (95%CI: 0.44 – 0.95, p = 0.03), 0.61 (95%CI: 0.41 – 0.90, p = 0.012), 0.53 (95%CI: 0.28 – 1.02, p = 0.057) relative to minimally reused LF ones for all cause, cardiovascular, cardiac and infectious mortality respectively. These relationships reversed for extensively reused membranes (p for interaction between reuse and flux < 0.001, p = 0.005) for death from all cause and cardiovascular causes, while similar trends were noted for cardiac and infectious mortality (p of interaction between reuse and flux of 0.10 and 0.08 respectively). Reduction of β2M explained only 1/3 of the effect of minimally reused HF dialyzers on all cause mortality, while non-β2M related factors explained the apparent attenuation of the benefit with more extensively reused dialyzers. Meta-regression of HEMO and MPO estimated an adjusted HR of 0.63 (95% CI: 0.51–0.78) for non-reused HF dialyzers compared with non-reused LF membranes.

Conclusions

This secondary analysis and synthesis of two large hemodialysis trials supports the widespread use of HF dialyzers in clinical hemodialysis over the last decade. A mechanistic understanding of the effects of HF dialysis and the reuse process on dialyzers may suggest novel biomarkers for uremic toxicity and may accelerate membrane technology innovations that will improve patient outcomes.

Inflammatory Response to Sorbent Hemodialysis

Inflammation is common and associated with morbidity and mortality in hemodialysis (HD) patients. Exposure to endotoxin contained in the dialysate may trigger inflammation. Dialysate volume is substantially reduced in sorbent HD compared with standard single-pass dialysis. In this prospective study (Clinicaltrials.gov, number: NCT00788905), we compared the inflammatory response to single-pass and sorbent HD. Patients receiving single-pass HD were studied during 1 week of sorbent HD (Allient system; Renal Solutions, Warrendale, PA) and 1 week of single-pass HD. Patients were dialyzed using high-flux polysulfone dialyzers. Midweek pre- and post-HD serum levels of high-sensitivity C-reactive protein, interleukin (IL)-1β, IL-6, IL-10, interferon gamma, tumor necrosis factor alpha (TNF-α), and eotaxin were determined and their intradialytic change corrected for hemoconcentration during single-pass HD and sorbent HD compared by paired t-test. We enrolled 18 patients, nine completed the study. Although TNF-α decreased during both single-pass and sorbent HD (p < 0.001), none of the other biomarkers changed significantly during HD. We observed no difference between single-pass and sorbent HD. For the markers investigated in this study, there was no difference in the acute intradialytic inflammatory response to single-pass or sorbent HD.

Transfer of low-molecular weight single-stranded DNA through the membrane of a high-flux dialyzer

PURPOSE

Microbial contamination is often present in dialysate used for hemodialysis. Small single-stranded bacterial DNA sequences are capable of activating human inflammatory pathways, through mechanisms that include the Toll-like-receptor 9, and dialysis patients frequently show severe inflammation. Since these molecules have been found in dialysate and in patients' bloodstreams, we studied the potential of low-molecular weight DNA sequences, of the same structure as found in bacteria, to cross from the dialyzer circuit to the blood circuit of a dialysis filter.

METHODS

The mass transfer of DNA fragments across a high-flux dialyzer was evaluated with an in vitro dialysis model, in both conventional dialysis and pure convection mode. Measurement of DNA was performed by HPLC.

RESULTS

In dialysis mode, these mass transfer coefficients were calculated for different single-stranded DNA chain lengths: 5-bases = 28.5%, 9-bases = 20.5%, 20-bases = 9.4%, 35-bases = 2.4%, 50-bases and 100-bases, no transfer detected. In convection mode, these sieving coefficients were calculated: 5-bases = 1.0, 9-bases = 1.0, 20-bases = 0.68, 35-bases = 0.40, 50-bases = 0.17, 100-bases, no convective transfer detected. The physical size of DNA molecules could be the major factor that influences their movement through dialyzer pores.

CONCLUSIONS

This study establishes that significant transfer across the dialyzer may occur with single-stranded DNA in the size range of 20-bases or less. These findings need to be confirmed with an in vitro whole blood model and with clinical investigations. Previous studies have described the clinical benefits of achieving high-purity dialysate. Precautions are warranted to minimize the presence of these DNA compounds in fluids utilized for hemodialysis treatment.

Hemodialysis and water quality

Over 383,900 individuals in the U.S. undergo maintenance hemodialysis that exposes them to water, primarily in the form of dialysate. The quality of water and associated dialysis solutions have been implicated in adverse patient outcomes and is therefore critical. The Association for the Advancement of Medical Instrumentation has published both standards and recommended practices that address both water and the dialyzing solutions. Some of these recommendations have been adopted into Federal Regulations by the Centers for Medicare and Medicaid Services as part of the Conditions for Coverage, which includes limits on specific contaminants within water used for dialysis, dialysate, and substitution fluids. Chemical, bacterial, and endotoxin contaminants are health threats to dialysis patients, as shown by the continued episodic nature of outbreaks since the 1960s causing at least 592 cases and 16 deaths in the U.S. The importance of the dialysis water distribution system, current standards and recommendations, acceptable monitoring methods, a review of chemical, bacterial, and endotoxin outbreaks, and infection control programs are discussed.

Endotoxemia after high cutoff hemodialysis for treatment of patient with multiple myeloma can be prevented by using ultrapure dialysate: a case report

To report endotoxemia presented in a case with multiple myeloma (MM) treated by high cutoff hemodialysis (HCO-HD) being prevented by using ultrapure dialysate. A female inpatient with MM received six times HCO-HD (HCO 2100 dialyzer) within 3 weeks after initiation of a chemotherapy based on vincristine+epirubicin+dexamethasone protocol. Conventional dialysate was used in the first three times and then changed to ultrapure dialysate due to elevation of body temperature after HCO-HD. Free light chains (FLC) and endotoxin levels in blood and dialysate were monitored. After six times HCO-HD, her serum FLC λ decreased from 4689 mg/L to 492.7 mg/L, with a trend of decline of serum creatinine. The clearance, reduction ratio, and removal amount of FLC λ was 38.4 mL/min, 71.0-85.2%, and 9.06-18.02 g, respectively, in the setting of dialysate flow rate 500 mL/min, while in the setting of dialysate flow rate 200 mL/min, the removal efficacy of FLC λ was lower than the former. A rise of body temperature up to 38.5°C after treatment and endotoxemia (endotoxin levels 0.122 EU/mL) was found when using conventional dialysate (endotoxin levels 0.112-0.145 EU/mL), but not seen after changing to ultrapure dialysate. Combined with appropriate chemotherapy, HCO-HD can effectively remove and reduce blood FLC. Attention should be paid to the endotoxemia and the rise of temperature after treatment when conventional dialysate is used, which can be prevented by using ultrapure dialysate.

Water quality in conventional and home haemodialysis

Dialysis water can be contaminated by chemical and microbiological factors, all of which are potentially hazardous to patients on haemodialysis. The quality of dialysis water has seen incremental improvements over the years, with advances in water preparation, monitoring and disinfection methods, and high standards are now readily achievable in clinical practice. Advances in dialysis membrane technology have refocused attention on water quality and its potential role in the bioincompatibility of haemodialysis circuits and adverse patient outcomes. The role of ultrapure dialysate is increasingly being advocated, given its proposed clinical benefits and relative ease of production as a result of the widespread use of reverse osmosis and ultrafiltration. Many of the issues pertaining to water quality in hospital-based dialysis units are also pertinent to haemodialysis in the home. Furthermore, an increased awareness of the environmental and financial consequences of home haemodialysis has resulted in the development of automated and more efficient dialysis machines. These new machines have an increased emphasis on water conservation and recycling along with a decreased need for a complex infrastructure for water purification and maintenance.

High-flux versus low-flux membranes for end-stage kidney disease

BACKGROUND

Clinical practice guidelines regarding the use of high-flux haemodialysis membranes vary widely.

OBJECTIVES

We aimed to analyse the current evidence reported for the benefits and harms of high-flux and low-flux haemodialysis.

SEARCH METHODS

We searched Cochrane Renal Group's specialised register (July 2012), the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1948 to March 2011), and EMBASE (1947 to March 2011) without language restriction.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared high-flux haemodialysis with low-flux haemodialysis in people with end-stage kidney disease (ESKD) who required long-term haemodialysis.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two authors for study characteristics (participants and interventions), risks of bias, and outcomes (all-cause mortality and cause-specific mortality, hospitalisation, health-related quality of life, carpal tunnel syndrome, dialysis-related arthropathy, kidney function, and symptoms) among people on haemodialysis. Treatment effects were expressed as a risk ratio (RR) or mean difference (MD), with 95% confidence intervals (CI) using the random-effects model.

MAIN RESULTS

We included 33 studies that involved 3820 participants with ESKD. High-flux membranes reduced cardiovascular mortality (5 studies, 2612 participants: RR 0.83, 95% CI 0.70 to 0.99) but not all-cause mortality (10 studies, 2915 participants: RR 0.95, 95% CI 0.87 to 1.04) or infection-related mortality (3 studies, 2547 participants: RR 0.91, 95% CI 0.71 to 1.14). In absolute terms, high-flux membranes may prevent three cardiovascular deaths in 100 people treated with haemodialysis for two years. While high-flux membranes reduced predialysis beta-2 microglobulin levels (MD -12.17 mg/L, 95% CI -15.83 to -8.51 mg/L), insufficient data were available to reliably estimate the effects of membrane flux on hospitalisation, carpal tunnel syndrome, or amyloid-related arthropathy. Evidence for effects of high-flux membranes was limited by selective reporting in a few studies. Insufficient numbers of studies limited our ability to conduct subgroup analyses for membrane type, biocompatibility, or reuse. In general, the risk of bias was either high or unclear in the majority of studies.

AUTHORS' CONCLUSIONS

High-flux haemodialysis may reduce cardiovascular mortality in people requiring haemodialysis by about 15%. A large well-designed RCT is now required to confirm this finding.

Computational Modeling of Effects of Mechanical Shaking on Hemodynamics in Hollow Fibers

Introduction:

Blood-membrane interaction during hemodialysis develops a secondary protein layer on the dialysis membrane surface, resulting in reduction of hemodialyzer performance. Wall shear stress at the surface of the hollow-fiber membrane is one of the determinant factors able to influence dialysis efficiency. Shaking of hemodialyzer during treatment could increase the wall shear stress of the membrane, which could enhance hemodialyzer performance.

Methods:

In this study, hemodynamic changes in hollow fibers were analyzed using computational fluid dynamics software for various shaking conditions of hemodialyzer (longitudinal, transverse, rotational motions).

Results:

Longitudinal motion induced reverse flow, while transverse motion induced symmetric swirling inside the hollow fiber. During rotational motions, nonuniform vortices were developed according to the rotational radius of the hollow fiber. These changes in flow pathlines induced by different shaking profiles increased the relative motion of blood, transmembrane pressure, and wall shear stress on dialysis membrane surfaces. Both longitudinal and transverse shaking profiles showed a linear relationship between shaking velocity (the product of amplitude and frequency) and wall shear stress.

Conclusion:

Performance of hemodialyzer can be enhanced with simple mechanical shaking motions, and optimal shaking profiles for clinical application can be investigated and predicted with the computational fluid dynamics model proposed in this study.