Clinical advantages of acetate-free biofiltration

Haemodiafiltration, haemofiltration and haemodialysis for end-stage kidney disease

BACKGROUND

Convective dialysis modalities (haemofiltration (HF), haemodiafiltration (HDF), and acetate-free biofiltration (AFB)) removed excess body fluid across the dialysis membrane with positive pressure and accumulated middle- and larger-size accumulated solutes more efficiently than haemodialysis (HD). This increased larger solute removal combined with use of ultra-pure dialysis fluid in convective dialysis is hypothesised to reduce the frequency and severity of symptoms during dialysis as well as improve clinical outcomes. Convective dialysis therapies (HDF and HF) are associated with lower mortality compared to diffusive therapy (HD) in observational studies. This is an update of a review first published in 2006.

OBJECTIVES

To compare convective (HF, HDF, or AFB) with diffusive (HD) dialysis modalities on clinical outcomes (mortality, major cardiovascular events, hospitalisation and treatment-related adverse events) in men and women with end-stage kidney disease (ESKD).

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register (to 18 February 2015) through contact with a Trials' Search Co-ordinator using search terms relevant to this review.

SELECTION CRITERIA

We included randomised controlled trials comparing convective therapy (HF, HDF, AFB) with another convective therapy or diffusive therapy (HD) for treatment of ESKD.

DATA COLLECTION AND ANALYSIS

Two independent authors identified studies, extracted data and assessed study risk of bias. We summarised treatment effects using the random effects model. We reported results as a risk ratio (RR) for dichotomous outcomes and mean difference (MD) for continuous data together with 95% confidence intervals (CI). We assessed for heterogeneity using the Chi(2) test and explored the amount of variation in treatment estimates beyond that expected by chance using the I(2) statistic.

MAIN RESULTS

Twenty studies comprising 667 participants were included in the 2006 review. In that review, there was insufficient evidence of treatment effects on major clinical outcomes to draw clinically meaningful conclusions. Searching to February 2015 identified 40 eligible studies comprising 3483 participants overall. In total, 35 studies (4039 participants) compared HF, HDF or AFB with HD, three studies (54 participants) compared AFB with HDF, and three studies (129 participants) compared HDF with HF.Risks of bias in all studies were generally high resulting in low confidence in estimated treatment effects. Convective dialysis had no significant effect on all-cause mortality (11 studies, 3396 participants: RR 0.87, 95% CI 0.72 to 1.05; I(2) = 34%), but significantly reduced cardiovascular mortality (6 studies, 2889 participants: RR 0.75, 95% CI 0.61 to 0.92; I(2) = 0%). One study reported no significant effect on rates of nonfatal cardiovascular events (714 participants: RR 1.14, 95% CI 0.86 to 1.50) and two studies showed no significant difference in hospitalisation (2 studies, 1688 participants: RR 1.23, 95% CI 0.93 to 1.63; I(2) = 0%). One study reported rates of hypotension during dialysis were significantly reduced with convective therapy (906 participants: RR 0.72, 95% CI 0.66 to 0.80). Adverse events were not systematically evaluated in most studies and data for health-related quality of life were sparse. Convective therapies significantly reduced predialysis levels of B2 microglobulin (12 studies, 1813 participants: MD -5.55 mg/dL, 95% CI -9.11 to -1.98; I(2) = 94%) and increased dialysis dose (Kt/V urea) (14 studies, 2022 participants: MD 0.07, 95% CI -0.00 to 0.14; I(2) = 90%) compared to diffusive therapy, but results across studies were very heterogeneous. Sensitivity analyses limited to studies comparing HDF with HD showed very similar results. Directly comparative data for differing types of convective dialysis were insufficient to draw conclusions.Studies had important risks of bias leading to low confidence in the summary estimates and were generally limited to patients who had adequate dialysis vascular access.

AUTHORS' CONCLUSIONS

Convective dialysis may reduce cardiovascular but not all-cause mortality and effects on nonfatal cardiovascular events and hospitalisation are inconclusive. However, any treatment benefits of convective dialysis on all patient outcomes including cardiovascular death are unreliable due to limitations in study methods and reporting. Future studies which assess treatment effects of convection dose on patient outcomes including mortality and cardiovascular events would be informative.

Haemodiafiltration, haemofiltration and haemodialysis for end-stage kidney disease

BACKGROUND

Renal replacement therapy (RRT) for end-stage kidney disease (ESKD) can be achieved by several interventions including haemodialysis (HD), peritoneal dialysis (PD) and kidney transplantation. HD, haemofiltration (HF), haemodiafiltration (HDF) and acetate-free biofiltration (AFB) are extracorporeal RRT methods. It has been suggested that HF and HDF may reduce the frequency and severity of intradialytic and post-dialytic adverse symptoms and may be more effective than HD in the removal of high molecular weight molecules.

OBJECTIVES

To compare convective modes of extracorporeal RRT (HF, HDF or AFB) with HD and to establish if any of these techniques is superior to each other in patients with ESKD.

SEARCH STRATEGY

We searched MEDLINE (1966-2006), EMBASE (1980-2006), Cochrane Central Register of Controlled Trials (CENTRAL, in The Cochrane Library issue 2, 2006) and CINAHL (1872-2006). Authors of included studies were contacted, reference lists of identified RCTs and relevant narrative reviews were screened.

SELECTION CRITERIA

RCTs comparing HF, HDF, AFB and HD for ESKD were included. Trials enrolling any patient undergoing RRT for ESKD were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. Statistical analyses were performed using the random effects model and the results expressed as relative risk (RR) for dichotomous outcomes or weighted mean difference (MD) for continuous data with 95% confidence intervals (CI). Heterogeneity was measured using the Chi-square (chi(2)) and I(2) statistic.

MAIN RESULTS

Twenty studies (657 patients) were included. Seventeen studies compared HF, HDF or AFB with HD, two compared HDF with AFB and one compared HF with HDF. The studies were generally small with suboptimal quality. Convective modalities (HF, HDF, AFB) did not differ significantly from HD for mortality (RR 1.68, 95% CI 0.23 to 12.13; chi(2)= 2.58, P = 0.11, I(2) = 61.2%), number of hospital admissions/year (MD 0.20, 95% CI -0.07 to 0.47) and dialysis adequacy (Kt/V: MD 0.09, 95% CI 0.02 to 0.17; chi(2) = 3.73, P = 0.29, I(2) = 19.6%). No study assessed number of dialysis treatments associated with "any adverse symptoms", sessions that were stopped early, change of dialysis modality or dialysis-related amyloidosis.

AUTHORS' CONCLUSIONS

We were unable to demonstrate whether convective modalities (either HF, HDF or AFB) have significant advantages over HD with regard to clinically important outcomes of mortality, dialysis-related hypotension and hospitalisation. More adequately-powered good quality RCTs assessing clinically important outcomes (mortality, hospitalisation, quality of life) are needed.

A Comparison of Bicarbonate Hemodialysis, Hemodiafiltration, and Acetate-free Biofiltration on Cytokine Production

Acetate-free biofiltration (AFB) is a special hemodiafiltration (HDF) modality performed with a base-free dialysate and simultaneous injection of non-pyrogenic sodium bicarbonate solution. The purpose of this study was to investigate the difference of cytokine production by conventional bicarbonate hemodialysis (BCD), standard HDF and AFB in the same patients. Eight stable hemodialysis patients were treated in random order with BCD, HDF and AFB every 4 weeks. The production of interleukin-1 beta (IL-1 beta) and interleukin-1 receptor antagonist (IL-1Ra) by peripheral blood mononuclear cells (PBMC) was investigated without stimulation and with stimulation by a small amount of endotoxin (ET)-contaminated beta 2-microglobulin (beta 2M) and lipopolysaccharide (LPS) before and after dialysis treatment in the last sessions during all periods. To serve as controls, 14 healthy volunteers participated in this study. In spontaneous IL-1Ra production, the values of before and after AFB were not significantly different from that of the controls, and the values of before and after BCD and before HDF were significantly higher than that of the controls. In LPS-stimulated PBMC, IL-1 beta production before and after AFB was not significantly different from that of the controls, and before and after BCD and HDF was significantly higher than that of the controls. In ET-contaminated beta 2M-stimulated PBMC, IL-1 beta production before and after AFB was not significantly different compared to the controls, and the production was significantly lower than that before and after BCD and HDF. In addition, IL-1Ra production after AFB was not significantly different from the controls, and the production was significantly lower than that before and after BCD and HDF. It was concluded that a lower cytokine production by AFB may have the effect of preventing dialysis-related complications.