Discussion
The major findings of this study were that HD using high-flux
dialysis membrane was associated with decreased mortality
compared to HD using low-flux dialysis membrane in patients
with 24 h-residual urine volume ,100 ml, whereas there was no
significant difference in mortality between the high- and the lowflux
dialysis group in patients with 24 h-residual urine volume $
100 ml. These data suggest that high-flux dialysis impacts survival
differently according to residual renal function and that high-flux
dialysis is superior to low-flux dialysis in patients without residual
renal function.
Residual renal function is associated with improved survival and
clinical outcomes such as hospitalization, nutrition, anemia, and
serum phosphorous control in HD patients [14–16]. Furthermore,
residual renal function is a strong predictor of serum b2-
microglobulin levels, since the kidney is the primary organ for
the clearance of b2-microglobulin [11]. In this study, serum b2-
microglobulin levels were significantly higher in patients with
24 h-residual urine volume ,100 ml (31 mg/L, interquartile
range, 23–45 mg/L) than in those with 24 h-residual urine
volume $100 ml (21 mg/L, interquartile range, 16–28 mg/L)
(p,0.001) (data not shown). A previous study also reported that
increment of residual renal function was associated with a decrease
in serum b2-microglobulin levels in dependent of years on dialysis
[11]. Therefore, the beneficial effects of high-flux dialysis by
clearance of middle molecules such as b2-microglobulin on clinical
outcomes may be overshadowed by residual renal function in HD
patients. Thus, it could be postulated that the beneficial effect of
high-flux dialysis may be more apparent in patients with lesser
residual renal function.
The HEMO study showed that there was no statistically
significant interaction between baseline residual renal function and
the type of flux intervention with respect to all-cause mortality
although there was a trend towards decreased mortality in patients
with lesser residual renal function [17]. They reported that all-