Extended-hours hemodialysis (HD) is associated with decreased mortality risk relative to conventional HD, according to a new study.

Matthew B. Rivara, MD, of the University of Washington in Seattle, and collaborators compared mortality risk among 1206 patients with end-stage renal disease (ESRD) undergoing thrice-weekly extended-hours HD and 111,707 receiving conventional HD. The average treatment time per session for extended-hours HD was 399 minutes compared with 211 minutes for conventional HD. The crude mortality rate with extended-hours HD was 64 deaths per 100 patient-years versus 14.7 per 100 patient-years for conventional HD.

Patients treated with extended-hours HD had a 33% lower adjusted risk of death compared with those who had conventional HD, Dr. Rivara and his colleagues reported online ahead of print in Kidney International.

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An important potential benefit of thrice-weekly extended-hours HD over other forms of dialysis intensification is avoidance of the need for more frequent use of the patient’s vascular access, the investigators noted. In the Frequent Hemodialysis Network trials, they pointed out, patients undergoing more frequent HD were more likely to experience complications related to vascular access versus patients undergoing conventional HD. In contrast, there is no evidence that thrice-weekly extended-hours HD is associated with an increase in access-related complications versus conventional HD.

Noting that the average treatment times of patients treated with extended-hours HD exceeded those of conventional HD by more than 3 hours, they explained that this substantial lengthening of HD treatment is much greater than what is possible to achieve within the context of conventional in-center HD or more frequent HD, whether performed in-center or at home.

Dr. Rivara and his collaborators discussed some potential mechanisms by which substantially longer HD treatments may lead to improved clinical outcomes, independent of any increase in dialysis frequency. For example, nocturnal extended-hours HD has been shown to enhance phosphorus removal and decrease arterial stiffness, which are potential mediators in the pathway between ESRD and clinical cardiovascular events. Dr. Rivara’s group noted that in their study, patients who switched from conventional in-center HD to extended-hours HD, serum phosphorus levels decreased into the range associated with lower risk for death in prior observational studies.

As far as the investigators are aware, their study is the largest to date of extended-hours HD, which they cited as a strength of the study. A second strength was the observation of a large difference in the mean and overall distribution of delivered treatment times between patients undergoing conventional versus extended-hours HD, enhancing their ability to detect an association between treatment time and outcomes.

The study also had limitations. The investigators explained, for example, that patients on extended-hours HD are likely to differ in important ways from patients on conventional HD, including attributes such as motivation, cardiovascular function, exercise capacity, cognitive function, and social support structures that are not captured in available data.