Fitness of biocompatible high-flux hemodiafiltration for dialysis-related amyloidosis

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.

New strategy to attenuate pulse wave velocity in haemodialysis patients

BACKGROUND

Pulse wave velocity (PWV) is commonly elevated in haemodialysis (HD) patients having cardiovascular diseases. Disturbances in calcium-phosphate metabolism are among the established cardiovascular risk factors in HD patients. The present study was performed to assess the effect of sevelamer on PWV in HD patients.

METHODS

Fifteen patients, who had been treated with calcium carbonate as a phosphate binder, were entered into the study. Changes in PWV during the 6 months before sevelamer administration were compared with PWV changes during 6 months of receiving sevelamer. Serum biochemistry parameters were also assessed.

RESULTS

Compared with the preceding control period, the sevelamer period resulted in decreased serum calcium (9.9+/-0.1 to 9.6+/-0.1 mg/dl, n = 15; P<0.01) in association with reductions in oral calcium load (4.3+/-0.4 to 2.3+/-0.6 g/day; P<0.001). Serum phosphorus and whole parathyroid hormone remained unchanged. Sevelamer reduced serum total cholesterol (167+/-7 to 148+/-6 mg/dl; P<0.001) and LDL-cholesterol (85+/-8 to 65+/-7 mg/dl; P<0.001), without modifying HDL-cholesterol or triglycerides. Finally, sevelamer reversed the increase in PWV observed during the control period (from 46+/-16 to -20+/-9 cm/s/month; P<0.01).

CONCLUSIONS

In chronic HD patients, sevelamer decreased serum total- and LDL-cholesterol as well as calcium. Moreover, our findings suggest that treatment with sevelamer attenuates the progressive increase in PWV observed during calcium carbonate treatment.

Young Hemodialysis Patients Are Exposed to Hyperhomocysteinemia

OBJECTIVE

Homocysteine is one of the cardiovascular risk factors in hemodialysis (HD) patients. Studies were performed to assess the effects of folic acid on pulse wave velocity (PWV) in HD patients.

METHODS

In a cross-sectional study, plasma total homocysteine (tHcy) was measured in 49 patients on maintenance HD. Ten HD patients younger than 45 years old entered the prospective study. Monthly changes in PWV were compared before and during folic acid treatment.

RESULTS

Younger HD patients had higher tHcy (r = -0.53, n = 49, P < .001). Patients who manifested myocardial ischemia (37 +/- 3 nmol/mL) possessed higher tHcy than those who did not (30 +/- 3 nmol/mL, P < .05). In prospective study, folic acid treatment (10 to 20 mg/d) failed to alter blood pressure and biochemical parameters, including lipids, calcium, phosphate, and parathormone. However, in association with a decrease in tHcy (46 +/- 5 to 27 +/- 3 nmol/mL, n = 10, P < .005), progressive increases in PWV (33 +/- 8 to 3 +/- 6 cm/sec/month, P < .01) were stopped.

CONCLUSIONS

The present findings indicate that young HD patients are exposed to severe hyperhomocysteinemia, and suggest that relatively large doses of folic acid attenuate progressive increases in PWV of young or middle-age HD patients.

Pulse wave velocity as an indicator of arteriosclerosis in hemodialysis patients

Studies were performed to examine whether pulse wave velocity (PWV) is a useful indicator of arteriosclerosis in hemodialysis (HD) patients. In total, 72 patients were enrolled. Annual changes in PWV were compared to clinical parameters and therapeutic maneuvers. PWV increased in diabetic patients faster than non-diabetics (35 +/- 10 cm/s/month versus 10 +/- 4 cm/s/month, P < 0.05). Changes in PWV showed strong correlations to triglyceride level exposed during observation period (r = 0.50, P < 0.05) and HD duration (r = 0.46, P < 0.05). In addition, we found that PWV of some patients decreased (regressors), while the others increased (non-regressors). Regressors more frequently received combined treatment with angiotensin blockade and lipid-lowering drugs or vitamin E-coated dialyzers than non-regressors (P < 0.05). Our data demonstrate that PWV is useful as a marker of arteriosclerosis in HD patients. Furthermore, the present results suggest that combined treatment with both angiotensin inhibition and lipid-lowering drugs or vitamin E-coated membrane would slow the progression of arteriosclerosis in HD patients.

Beta-2 microglobulin in ESRD: an in-depth review

Beta-2 microglobulin is the most widely studied low-molecular-weight protein in end-stage renal disease. It is known to cause dialysis-related amyloidosis (DRA), by virtue of its retention when renal function fails, its deposition in tissues, its aggregation into fibrils, and its ability to become glycosylated. The onset of DRA may be protracted by the use of noncellulosic membranes, especially when high-volume hemodiafiltration is used in the treatment of renal failure. Adsorptive methods have been developed to improve the removal of beta-2 microglobulin. There seems to be a relative risk reduction in mortality when patients are treated with dialysis membranes that have a higher clearance of beta-2 microglobulin.

The next step from high-flux dialysis: application of sorbent technology

The current foci of renal replacement therapy with dialysis are middle molecular weight toxins, consisting of small proteins, polypeptides and products of glycosylation and lipoxygenation. Conventional high-flux dialysis is not efficient at removing these molecules, explaining the increased interest in using sorbents to supplement dialysis techniques. Prototype biocompatible sorbents have been developed and investigated for middle molecule removal; these have been shown, in man, to remove beta(2)-microglobulin, angiogenin, leptin, cytokines and other molecules, without reducing platelets and leukocytes. Extensive clinical studies are underway to demonstrate the clinical utility and safety of adding routinely a sorbent hemoperfusion device to hemodialysis.

Warning of high-flux hemodialysis

In order to estimate the influence of flux on plasma refilling during hemodialysis (HD), prospective crossover studies were performed in 10 HD patients with low-flux and high-flux dialyzers. Hematocrit was continuously monitored to assess changes in blood volume. In addition, plasma osmolarity and total protein concentration were measured. Intradialytic reductions in body weight (-5 +/- 1 vs -5 +/- 1%) and plasma osmolarity (-5 +/- 1 vs -5 +/- 1%) were similar in both conditions. Although mean blood pressure remained unchanged in either state, the decrease in blood volume was larger in high-flux HD (-13 +/- 2 vs -10 +/- 2%, p<0.05). In spite of greater contraction in blood volume during high-flux HD, total proteins were increased equally between low-flux and high-flux HD (11 +/- 4 vs 11 +/- 4%). Our data that although high-flux HD failed to induce significant drops in blood pressure, it elicited greater magnitude of decreases in blood volume, implicate the judicious application of high-flux HD.