Two-Day Dialysis Interval Could Pose Danger: Study

Waiting 48 hours between kidney treatments seems to raise risk of death, hospitalization

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By Mary Brophy Marcus
HealthDay Reporter

WEDNESDAY, Sept. 21 (HealthDay News) -- Waiting more than a day between dialysis treatments ups the risk of death and hospitalization in people with kidney disease, new research suggests.

Patients are more likely to die or head to the hospital for cardiovascular-related and other complications following a two-day interval between dialysis sessions compared to a one-day gap, concluded researchers from the U.S. Renal Data System (USRDS) and the University of Minnesota, both in Minneapolis.

"It shows an association between adverse outcomes and a two-day interval between dialysis sessions," said study author Dr. Robert Foley, deputy director of the USRDS Coordinating Center, whose observational study involved more than 32,000 people on hemodialysis.

Hemodialysis is the more common form of dialysis in the United States, said Dr. Martin Zand, a professor of medicine in the division of nephrology at the University of Rochester Medical Center in New York. Used by people whose kidneys function at about 15 percent or less, this machine-based treatment removes toxins and extra fluid from the blood. Zand said kidney failure patients typically visit an outpatient dialysis center three times a week for sessions that last roughly four hours.

"Most patients are on a Monday, Wednesday, Friday schedule, or a Tuesday, Thursday, Saturday schedule, so once a week, they're missing dialysis for two days instead of one," Zand explained.

More than 340,000 people with chronic kidney disease are on hemodialysis, according to the U.S. National Kidney Foundation. In 75 percent of cases, kidney failure is caused by diabetes and high blood pressure.

The study, published in the Sept. 22 issue of the New England Journal of Medicine, followed 32,065 dialysis patients, average age 62, for a little more than two years.

During that time, 41 percent died from all causes. The average annual death rates were 22 percent on the day after the two-day interval compared to 18 percent on other days. The findings showed cardiac-related death rates were higher after the two-day interval, 10.2 percent compared to 7.5 percent after a one-day gap. Cardiac arrest after the longer interval was 1.3 percent compared to 1 percent, and deaths from heart attack were 6.3 percent vs. 4.4 percent.

Hospital admission rates were also steeper following the longer wait between dialysis visits. Hospitalization rates for heart attack were 6.3 percent compared to 3.9 percent, and congestive heart failure admission rates were almost double after a two-day interval (29.9 percent vs. 16.9 percent). Hospitalization rates for stroke were also higher (4.7 percent vs. 3.1 percent).

"This is a terrific study. Well-designed and clearly written," said Dr. Ajay Singh, an associate professor of medicine at Harvard Medical School and a practicing nephrologist. While the authors do not discuss the potential explanation for their findings, Singh said it's possible that the higher risk of death and hospitalization associated with the longer wait time stems from excessive fluid buildup or an electrolyte abnormality, perhaps related to elevated potassium levels, that harm the heart. Potassium is a mineral that can build up in blood and cause an abnormal heartbeat called an arrhythmia.

"The take-away message of the study is really something that many of us have known from our clinical practices for years -- that the long two-day interval between dialysis treatments in somebody on a three-day-a-week schedule is a point of high risk for heart attacks, congestive heart failure and hospital admissions," Zand said. "It begs the question, do we need to re-examine the three-day-a-week schedule?"

Foley said it's too early to change dialysis protocol. "Our study suggests that alternate-day treatment versus conventional three times per week treatment is a trial that needs to be seriously considered," he said.

Foley also emphasized that studies like this that draw conclusions from associations "are shaky foundations" upon which to build new treatment guidelines. He said the next step should be a trial in which patients are randomly assigned to different dialysis schedules and their outcomes compared.