An odd asymmetry of hemodialysis is that almost all patients have treatments every other day, Wednesday and then Friday or Thursday and then Saturday; but then a 2 day break over the weekend. What happens from Friday to Monday or Saturday to Tuesday, is there increased risk? ( image source: www.tws3d.com)
Robert Foley and colleagues from the United States Renal Data System studied exactly this question. Their study was published recently in the New England Journal of Medicine (N Engl J Med 2011;365:1099-107). A total of 32,065 hemodialysis patients from the Clinical Performance Measures Project were studied from 2004-2007. The main finding was that on the day after the long interdialytic period there was an approximately 20% increase in deaths, more than a 30% increase in deaths from cardiac causes, a 30% increase in deaths from cardiac arrest and a number of other outcomes with increased risk.
This simple but elegant study places a sharp focus on what may be intuitive, hemodialysis patients are at greater risk after the long interdialytic period- usually after a weekend. Is it excessive intake of salt, potassium and other electrolytes over the weekend? Increased volume intake? A reduction in calcium with widened QT intervals? Whatever the cause, we need to think about how hemodialysis may be changed to keep patients safer.
I asked Dr. Foley about what the clinical implications of these finding are. He responded, “Like all observational studies, cause and effect can't be proven here. However, unlike most observational studies, differences in unmeasured comorbidity can't explain the findings, as the same population is being examined for outcomes on different days. Given the downward-tilted sawtooth pattern for death and cardiovascular admissions, it is hard to imagine that anything other than more frequent dialysis and avoidance of two-day intervals could change the current situation. Clearly, this would involve major philosophical and logistical shifts.”
Steven Fishbane, MD
Prof of Medicine