How will the results of the HEMO study impact dialysis practice?

Is β2-Microglobulin-Related Amyloidosis of Hemodialysis Patients a Multifactorial Disease? a New Pathogenetic Approach

Purpose

β2-microglobulin amyloidosis (Aβ2M) is one of the main long-term complications of dialysis treatment. The incidence and the onset of Aβ2M has been related to membrane composition and/or dialysis technique, with non-homogeneous results. This study was carried out to detect: i) the incidence of bone cysts and CTS from Aβ2M; ii) the difference in Aβ2M onset between cellulosic and synthetic membranes; iii) other risk factors besides the membrane.

Methods

480 HD patients were selected between 1986 to 2005 and grouped according to the 4 types of membranes used (cellulose, synthetically modified cellulose, synthetic low-flux, synthetic high-flux). The patients were analyzed before and after 1995, when the reverse osmosis treatment for dialysis water was started at our center, and the incidence of Aβ2M was compared between the two periods. Routine plain radiography, computer tomography (CT) and nuclear magnetic resonance imaging (MRI) as well as electromyography were used to investigate the clinical symptoms.

Results

Bone cysts occurred in 29.2% of patients before 1995 vs. 12.2% after 1995 (p<0.0001). CTS occurred in 24% of patients before 1995 vs. 7.1% after 1995 (p<0.0001). Bone cysts and CTS occurred in older patients, who began dialysis at a late age, with high CRP, low albumin, low residual GFR, and low Hb. Cox regression analysis showed that the risk factor for bone cysts was high CRP (RR 1.3, p<0.01), while albumin (RR 0.14, p<0.0001) and residual GFR (RR 0.81, p<0.0001) were revealed to be protective factors. Cox analysis for CTS confirmed CRP as a risk factor (RR 1.2, p<0.01), and albumin (RR 0.59, p<0.0001) and residual GFR (RR 0.75, p<0.0001) as protective factors. The comparison obtained between membranes did not suggest any protective effect on Aβ2M.

Conclusions

The findings that the inflammatory status as well as low albumin and the residual GFR of the uremic patient are predictive of Aβ2M lesions suggests that Aβ2M has a multifactorial origin rather than being solely a membrane- or technique-related side effect.

Antidepressants for treating depression in adults with end-stage kidney disease treated with dialysis

BACKGROUND

Depression affects approximately one-quarter of people treated with dialysis and is considered an important research uncertainty by patients and health professionals. Treatment for depression in dialysis patients may have different benefits and harms compared to the general population due to different clearances of antidepressant medication and the severity of somatic symptoms associated with end-stage kidney disease (ESKD). Guidelines suggest treatment of depression in dialysis patients with pharmacological therapy, preferably a selective serotonin reuptake inhibitor. This is an update of a review first published in 2005.

OBJECTIVES

To evaluate the benefit and harms of antidepressants for treating depression in adults with ESKD treated with dialysis.

SEARCH METHODS

We searched Cochrane Kidney and Transplant's Specialised Register to 20 January 2016 through contact with the Information Specialist using search terms relevant to this review.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing antidepressant treatment with placebo or no treatment, or compared to another antidepressant medication or psychological intervention in adults with ESKD (estimated glomerular filtration rate < 15 mL/min/1.73 m(2)).

DATA COLLECTION AND ANALYSIS

Data were abstracted by two authors independently onto a standard form and subsequently entered into Review Manager. Risk ratios (RR) for dichotomous data and mean differences (MD) for continuous data were calculated with 95% confidence intervals (95% CI).

MAIN RESULTS

Four studies in 170 participants compared antidepressant therapy (fluoxetine, sertraline, citalopram or escitalopram) versus placebo or psychological training for 8 to 12 weeks. In generally very low or ungradeable evidence, compared to placebo, antidepressant therapy had no evidence of benefit on quality of life, had uncertain effects on increasing the risk of hypotension (3 studies, 144 participants: RR 1.72, 95% CI 0.75 to 3.92), headache (2 studies 56 participants: RR 2.91, 95% CI 0.73 to 11.57), and sexual dysfunction (2 studies, 101 participants: RR 3.83, 95% CI 0.63 to 23.34), and increased nausea (3 studies, 114 participants: RR 2.67, 95% CI 1.26 to 5.68). There were few or no data for hospitalisation, suicide or all-cause mortality resulting in inconclusive evidence. Antidepressant therapy may reduce depression scores during treatment compared to placebo (1 study, 43 participants: MD -7.50, 95% CI -11.94 to -3.06). Antidepressant therapy was not statistically different from group psychological therapy for effects on depression scores or withdrawal from treatment and a range of other outcomes were not measured.

AUTHORS' CONCLUSIONS

Despite the high prevalence of depression in dialysis patients and the relative priority that patients place on effective treatments, evidence for antidepressant medication in the dialysis setting is sparse and data are generally inconclusive. The relative benefits and harms of antidepressant therapy in dialysis patients are poorly known and large randomised studies of antidepressants versus placebo are required.

Relationship between the target dose for hemodialysis adequacy and nutritional assessment

BACKGROUND

Some studies have shown an increased relative risk of death for patients with higher levels of Kt/V, which may be associated with marked malnutrition.

OBJECTIVE

The aim of this study was to investigate the relationship between the target dose for hemodialysis adequacy, as measured by Kt/V, and various nutritional parameters in hemodialysis patients.

DESIGN

Cross-sectional.

SETTINGS

Sakarya University Faculty of Medicine, Turkey between February 2014 and March 2014.

PATIENTS AND METHODS

For consecutive patients who met criteria, the following were recorded: nutritional status, dialysis malnutrition score (DMS), the geriatric nutritional risk index (GNRI), serum albumin level, anthropometric measurements, and bioelectrical impedance analysis. Patients were classified into two groups according to the target hemodialysis dose for single-pool Kt/V: patients with spKt/V >=1.4 and patients with spKt/V < 1.4.

MAIN OUTCOME MEASURE(S)

Association of hemodialysis adequacy by nutritional assessment.

RESULTS

The prevalence of malnutrition in 286 patients with target dose hemodialysis (spKt/V >=1.4) was significantly higher according to body mass index (BMI), DMS, and GDRI (P=.001, P=.006, and P=.004, respectively) compared with patients with a lower target dose (spKt/V < 1.4). BMI, biceps skinfolds, mid-arm circumference, calf circumference, fat free mass, and total body water were statistically significantly lower in patients at a higher target dose (spKt/V >= 1.4) (P < .001, P=.034, P=.010, P < .001, P < .001, and P < .001 respectively).

CONCLUSIONS

Malnutrition was more frequent in chronic hemodialysis patients who received the target hemodialysis. Evaluation of nutritional status in patients at the target hemodialysis dose should be considered.

LIMITATIONS

Data collected from a single region; small sample size; cross-sectional design is disadvantageous.

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.

Urea kinetics and intermittent dialysis prescription in small animals

Hemodialysis improves survival for animals with acute kidney injury beyond what would be expected with conventional management of the same animals. Clinical evidence and experience in human patients suggest a role for earlier intervention with renal replacement to avoid the morbidity of uremia and to promote better metabolic stability and recovery. For a large population of animal patients, it is the advanced standard for the management of acute and chronic uremia, life-threatening poisoning, and fluid overload for which there is no alternative therapy.

Associations of hemodialysis dose and session length with mortality risk in Australian and New Zealand patients

The optimal combination of hemodialysis (HD) dose and session length remains uncertain, and previous studies have not conclusively shown session length to be an important independent determinant of patient mortality. The objective of this study was to examine associations between HD dose and session length with mortality risk using data from the Australian and New Zealand Dialysis and Transplant Registry. Analyses were performed using a prospective inception cohort comprising all incident adult patients treated by thrice-weekly maintenance HD, who commenced renal replacement therapy with HD between 1 April 1997 and 31 March 2004. In all, 6593 patients were identified, of whom 4193 had sufficient data for multivariate analyses. HD dose (single pool fractional clearance of urea, Kt/V) and session length were included in analyses as those recorded 12 months after HD inception to reduce confounding by residual renal function. The outcome examined was patient mortality. Survival analyses included Kaplan-Meier calculations of survival and Cox regression for multivariate analyses. Covariates in Cox models included patient demographics, co-morbid medical conditions at HD inception, and HD operating parameters. After adjustment for covariates and each other, Kt/V of 1.30-1.39 and session length of 4.5-4.9 h were associated with the lowest mortality risk. There was no interaction between HD dose and session length. Thus, the optimal combination for mortality appears to be Kt/V of > or = 1.3 and session length of > or = 4.5 h. These data suggest a randomized controlled trial to test these hypotheses, and support the inclusion of criteria relating to session length in definitions of adequate HD practice.

Dose of dialysis: key lessons from major observational studies and clinical trials

Analyses based on the National Cooperative Dialysis Study (NCDS) provided the impetus for routine quantification of delivered dialysis dose in hemodialysis practice throughout the world, by suggesting minimum targets for small solute (urea) clearance. Morbidity and mortality in dialysis populations remain high despite many technological advances in dialysis delivery. A number of observational studies reported association between higher dose of dialysis as measured by Kt/V urea or urea reduction ratio with lower mortality risk. During the 1990s, a steady increase in dialysis dose and a modest reduction in mortality on dialysis were observed. However, observational studies only reveal associations and are limited by selection bias and confounding. The Kidney Disease Outcomes Quality Initiative guidelines on dialysis adequacy are based on results of observational studies and expert opinion. Since the NCDS, the HEMO Study was the first major randomized clinical trial designed to study the effect of dose of dialysis and dialyzer flux on patient outcomes. Despite adequate separation of dose and flux, however, results of the trial did not prove a beneficial effect of higher dose. The Dialysis Outcomes and Practice Patterns Study (DOPPS), in a major international effort designed to examine the effect of practice patterns on outcomes, has made significant contributions to the topic of dialysis dose. The following review critically examines data from observational studies, including the DOPPS, and from the HEMO Study, emphasizing important lessons from both, and discusses future paradigms for achieving dialysis adequacy to improve patient outcomes.

Beyond Kt/V: redefining adequacy of dialysis in the 21st century

I presume that every dialysis patient needs a minimal amount of dialysis, since less dialysis will lead to death. Until we come up with a better index, for hemodialysis, I propose that we should return to Scribner's 1974 recommendation on adequacy of dialysis and concentrate on the homeostatic function of the kidney, as indicated in Table 1. For those who still want to measure dialysis dose by Kt/V, the optimal dose for HD is a Kt/V of 1.2/treatment and for PD 1.7/week. None of these would be adequate without good UF and control of patients' fluid status. Frequent (4, 5, 6 or 7 days/week) and prolonged dialyses (5-8 hours) should be the norm and I believe that the Hemodialysis Product should be used as a guide, pending confirmation by prospective studies. A high hemodialysis product reflects much more closely the function of the normal kidneys than 3-4 hours of dialysis three times a week with a Kt/V of 1.2 per session. Peritoneal dialysis that is already continuous needs to improve its efficiency. For PD patients, I believe that the total daily volume (Kt) might be a better index of adequacy, especially if it is combined with a good ultrafiltration (at least of 1 L/day) and blood pressure control. Of course, this has to be confirmed in the future. In the anuric patients, the daily volume can be kept to 8 L/day if the patient is free of symptoms, but should be increased to 10-12 L/day for CAPD and 15-20 L/day for APD patients if they develop symptoms of underdialysis and fluid overload.

Middle molecules and small-molecular-weight proteins in ESRD: properties and strategies for their removal

Molecular weight has traditionally been the parameter most commonly used to classify uremic toxins, with a value of approximately 500 Da frequently used as a demarcation point below which the molecular weights of small nitrogenous waste products fall. This toxin group, the most extensively studied from a clinical perspective, is characterized by a high degree of water solubility and the absence of protein binding. However, uremia is mediated by the retention of a plethora of other compounds having characteristics that differ significantly from those of the previously mentioned group. As opposed to the relative homogeneity of the nitrogenous metabolite class, other uremic toxins collectively are a very heterogeneous group, not only with respect to molecular weight but also other characteristics, such as protein binding and hydrophobicity. A recently proposed classification scheme by the European Uraemic Toxin Work Group subdivides the remainder of molecules into 2 categories: protein-bound solutes and middle molecules. For the latter group, the Work Group proposes a molecular weight range (500-60,000 Da) that incorporates many toxins identified since the original middle molecule hypothesis, for which the upper molecular weight limit was approximately 2,000 Da. In fact, low-molecular-weight peptides and proteins (LMWPs) comprise nearly the entire middle molecule category in the new scheme. The purpose of this article is to provide an overview of the middle molecule class of uremic toxins, with the focus on LMWPs. A brief review of LMWP metabolism under conditions of normal (and in a few cases, abnormal) renal function will be presented. The physical characteristics of several LMWPs will also be presented, including molecular weight, conformation, and charge. Specific LMWPs to be covered will include beta 2-microglobulin, complement proteins (C3a and Factor D), leptin, and proinflammatory cytokines. The article will also include a discussion of the treatment-related factors influencing dialytic removal of middle molecules. Once these factors, which include membrane characteristics, protein-membrane interactions, and solute removal mechanisms, are discussed, an overview of the different therapeutic strategies used to enhance clearance of these compounds is provided.