The Frequent Hemodialysis Network Trial Group recently found that compared with conventional in-center hemodialysis (HD) that is performed three times a week, frequent in-center HD (6 times a week) improved self-reported physical health and functioning for patients with end-stage renal disease (ESRD) but had no significant effect on objective physical performance, according to a report in the Clinical Journal of the American Society of Nephrology 2012;7:782-794).

Frequent nocturnal dialysis, for its part, showed no significant effects on any of these physical metrics. Nephrologist and study coauthor Yoshio Hall, MD, Assistant Professor of Medicine at the University of Washington, Seattle, discusses his team’s findings with Renal & Urology News.

Were you surprised and/or disappointed by these findings?

Dr. Hall:  We hypothesized that increasing the frequency of hemodialysis might further improve overall physical capacity through perhaps better control of uremia, preservation of nutritional status and muscle mass, correction of acid-base imbalances, and reduction of interdialytic weight gain and volume overload.

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Overall, our results were mixed. The lack of demonstrable effects of frequent nocturnal home hemodialysis on all physical measures was perhaps unsurprising due to limited sample size (87 patients) of the Frequent Hemodialysis Network nocturnal trial.

The modest effects of frequent hemodialysis on self-reported physical health and functioning were consistent with those demonstrated in the HEMO study [Kidney International 2004;66:355-366;], in which increasing the per-session dose of dialysis led to better preservation of self-reported physical health and functioning among patients receiving hemodialysis three times per week.

These results deserve attention, as self-reported physical health and functioning are important predictors of subsequent morbidity and mortality.

Unfortunately, no prior randomized studies have demonstrated significant improvements in physical performance by increasing dialysis dose.

The lack of effect of frequent hemodialysis on physical performance suggests that the potential benefits of frequent dialysis (in terms of dietary intake or body composition) will likely only be realized if the person engages in concurrent physical activity. Simply increasing the dialysis frequency (and thereby dose) appears to have little measurable effect on physical performance, at least in this trial population.

What else should nephrologists know about the results?

Dr. Hall: Difficulty in recruitment reduced the sample size of the nocturnal trial and precluded detection of smaller but potentially meaningful effects of frequent nocturnal hemodialysis on physical performance, health, and functioning. In addition, the characteristics of the study participants differed substantially between the two trials.

It is important to note also that mean scores for self-reported physical health increased in both groups receiving nocturnal home hemodialysis, suggesting that changing the dialysis venue (in-center to home) may have also influenced self-perceived physical health.

Alternatively, the presence of substantial residual kidney function among subjects enrolled in the nocturnal trial may have reduced the potential effect of hemodialysis frequency on physical health and functioning, and perhaps on physical performance.