Long Interdialytic Interval Raises Mortality Risk

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Hemodialysis (HD) patients have a greater risk of dying on the day following a long (two-day) interdialytic interval compared with other days, a study found.

Most HD patients do not dialyze in the two days between Friday and Monday or between Saturday and Tuesday, the study authors observed. In an analysis of data from 32,065 HD patients, Robert N. Foley, MB, of the U.S. Renal Data System in Minneapolis, Minn., and colleagues found a 22% increased death risk on the day after a long interval compared with other days.

In addition, on the day after the long interval, HD patients were significantly more likely to die from, or be hospitalized for, cardiovascular events compared with other days. The risk of death from cardiac causes was 36% higher on the day after a long interval compared with other days and the risk of being hospitalized for any cardiovascular event was more than doubled.

The patients in the study were participants in the End-Stage Renal Disease Clinical Performance Measures Project, a nationally representative sample of U.S. patients received HD thrice weekly.

Writing in the New England Journal of Medicine (2011;365:1099-1107), the investigators explained that ESRD patients “have a limited capacity to maintain homeostasis in the presence of metabolic and volume-related deviations from normal ranges, and most patients begin maintenance dialysis with overt cardiovascular disease. Consequently, there has been concern that the two-day interval may needlessly raise mortality risk.”

The authors pointed out that daily HD treatment has the potential to alleviate these concerns and two clinical trials have shown improvements in surrogate outcomes such as left ventricular mass and quality of life with this approach.

Commenting on the new study, Anthony J. Bleyer, MD, Professor of Internal Medicine/Nephrology at Wake Forest University School of Medicine in Winston-Salem, N.C., said the new study expands on prior studies over the past decade showing an increased risk of cardiac death on Monday for HD patients who have a Monday-Wednesday-Friday dialysis schedule and on Tuesday for patients with a Tuesday- Thursday-Saturday schedule.

For peritoneal dialysis patients, previous studies have shown an increased cardiac death rate on Monday, similar to the general population.

“It is important to remember that the death rates are comparable between hemodialysis and peritoneal dialysis,” Dr. Bleyer said, “so that one should not choose peritoneal dialysis over hemodialysis solely because of the increased cardiac death rate after the weekend interval.” Kidney transplantation is the one form of renal replacement therapy that is associated with a marked improvement in survival, he added. 

“While the current study shows an increased cardiac mortality after the two-day dialysis-free interval, this does not necessarily mean that daily dialysis would result in improved survival,” Dr. Bleyer said.

A recent randomized study did not show an increased survival in patients receiving daily dialysis, but the study may not have had sufficient statistical power to show this, he said.

“Nephrologists should counsel their patients about the risk of the dialysis-free weekend interval, and the importance of limiting their fluid and potassium intake during this time period,” Dr. Bleyer advised. “Patients should be advised to seek help if they develop symptoms of volume overload during the weekend interval.”

Although the dialysis population is at increased risk of cardiac death, it is important to remember that these deaths occur most commonly in patients with underlying heart disease, including congestive heart failure and coronary artery disease. “Nephrologists should evaluate these patients carefully after the weekend interval for symptoms of failure,” he said. “Consideration should be given to dialyzing these patients four times per week.” 

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