Benefits and Risks of Frequent or Longer Haemodialysis

Weighing the Evidence

Pantelis Sarafidis; Danai Faitatzidou; Aikaterini Papagianni


Nephrol Dial Transplant. 2021;36(7):1168-1176. 

In This Article

Abstract and Introduction


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.


In the early days of haemodialysis (HD) as renal replacement therapy (RRT) for end-stage renal disease (ESRD), schedules including short HD sessions (3 h every other day or 4 h thrice weekly) were described.[1] The thrice-weekly schedules (performed on Monday–Wednesday–Friday or Tuesday–Thursday–Saturday) quickly prevailed and became the standard in most of the world, without solid evidence from randomized clinical trials (RCTs) with hard outcomes, but due to 'calendar logistics' relevant to the weekly work schedule, health unit structure and patient convenience. Patients under this schedule remain outside dialysis for two 2-day intervals (~44 h) prior to the second and third weekly session, and one 3-day interval (~72 h) during the weekend.[2,3] However, their capacity to maintain the homoeostasis of metabolic and volume parameters is equally impaired in all weekdays; it was therefore hypothesized that this intermittent nature of conventional HD could translate to heightened risk of complications, particularly towards the end of the 3-day interval and the subsequent dialysis.[4,5]

In recent years, large observational studies evaluated the day-of-the-week morbidity and mortality in HD. A retrospective study examined all-cause mortality and cardiovascular-related hospitalizations during the day after the 3-day interval in comparison with all other days in 32 065 patients receiving conventional HD.[4] Over 2.2 years, higher rates on this day were noted for all-cause mortality (22.1 versus 18.0 deaths per 100 person-years; P < 0.001), cardiovascular mortality (10.2 versus 7.5; P < 0.001) and cardiovascular hospitalizations. Other studies with populations from various parts of the world[6–9] showed also increased cardiovascular-related hospitalizations, cardiovascular deaths and all-cause mortality on the first dialysis day (Monday or Tuesday). Mechanisms proposed for this increased risk include greater volume accumulation and blood pressure (BP) increase over the long interval [which not only raises pulmonary oedema risk before dialysis, but also requires a higher ultrafiltration rate (UFR) during dialysis, contributing to intradialytic hypotension (IDH), cardiac ischaemia and myocardial stunning], larger fluctuations in electrolyte and acid–base parameters (for instance, higher serum to dialysate K+ gradient increasing arrhythmia risk), and others.[2]

Such observations suggest a strong link between day-of-week mortality and dialysis schedule and call for ways to eliminate the relevant risks through re-evaluation of timing and frequency of prescribed HD regimens. Over the years, various frequent and/or longer, home or in-centre, dialysis schemes have been implemented aiming to offer a more 'continuous' form of RRT and reduce the risks of conventional HD, by both minimizing interdialytic time and by augmenting total weekly dialysis duration. This review presents data from observational studies and RCTs on the effects of these schemes on hard and intermediate outcomes, providing an overview of current evidence.