Benefits and risks of frequent or longer haemodialysis: weighing the evidence

Although the ability of individuals with end-stage renal disease to maintain body homoeostasis is equally impaired during all weekdays, conventional haemodialysis (HD) treatment is scheduled thrice weekly, containing two short and one long interdialytic interval. This intermittent nature of HD and the consequent fluctuations in volume, metabolic parameters and electrolytes have long been hypothesized to predispose to complications. Large observational studies link the first weekday with an increased risk of cardiovascular morbidity and mortality. Several schemes of frequent and/or longer, home or in-centre HD have been introduced, aiming to alleviate the above risks by both increasing total dialysis duration and reducing the duration of interdialytic intervals. Observational studies in this field have non-uniform results, showing that enhanced frequency in home (but not in-centre) HD is associated with reduced mortality. Evidence from the randomized Daily and Nocturnal Trials of the Frequent HD Network suggest the opposite, showing mortality benefits with in-centre daily but not with home nocturnal dialysis. Secondary analyses of these trials indicate that daily and nocturnal schedules do not have equal effects on intermediate outcomes. Alternative schemes, such as thrice weekly in-centre nocturnal HD or every-other-day HD, seem to also offer improvements in several intermediate endpoints, but need further testing with randomized trials. This review summarizes the effects of frequent and/or longer HD methods on hard and intermediate outcomes, attempting to provide a balanced overview of the field.

Extended Duration Nocturnal Hemodialysis and Changes in Plasma Metabolite Profiles

Background and objectivesIn-center, extended duration nocturnal hemodialysis has been associated with variable clinical benefits, but the effect of extended duration hemodialysis on many established uremic solutes and other components of the metabolome is unknown. We determined the magnitude of change in metabolite profiles for patients on extended duration nocturnal hemodialysis.Design, setting, participants, & measurementsIn a 52-week prospective, observational study, we followed 33 patients receiving conventional thrice weekly hemodialysis who converted to nocturnal hemodialysis (7–8 hours per session, three times per week). A separate group of 20 patients who remained on conventional hemodialysis (3–4 hours per session, three times per week) served as a control group. For both groups, we applied liquid chromatography-mass spectrometry–based metabolite profiling on stored plasma samples collected from all participants at baseline and after 1 year. We examined longitudinal changes in 164 metabolites among those who remained on conventional hemodialysis and those who converted to nocturnal hemodialysis using Wilcoxon rank sum tests adjusted for multiple comparisons (false discovery rate <0.05).ResultsOn average, the nocturnal group had 9.6 hours more dialysis per week than the conventional group. Among 164 metabolites, none changed significantly from baseline to study end in the conventional group. Twenty-nine metabolites changed in the nocturnal group, 21 of which increased from baseline to study end (including all branched-chain amino acids). Eight metabolites decreased after conversion to nocturnal dialysis, including l-carnitine and acetylcarnitine. By contrast, several established uremic retention solutes, including p-cresol sulfate, indoxyl sulfate, and trimethylamine N-oxide, did not change with extended dialysis.ConclusionsAcross a wide array of metabolites examined, extended duration hemodialysis was associated with modest changes in the plasma metabolome, with most differences relating to metabolite increases, despite increased dialysis time. Few metabolites showed reduction with more dialysis, and no change in several established uremic toxins was observed.