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Fluid Removal during Hemodialysis: An Interview with Dr. Jennifer Flythe, Part I
As you are no doubt aware, fluid removal in hemodialysis in general, and the ultrafiltration (UF) rate in particular, have become areas of increasing attention in the renal community. Much has been written on these topics over the past few years and related research is currently underway. In addition, UF rate is slated to become part of the Centers for Medicare & Medicaid Service’s (CMS) End Stage Renal Disease (ESRD) Quality Incentive Program (QIP). I sat down with Dr. Jennifer Flythe, an expert on hemodialytic fluid removal, for part one of a two-part discussion about where we, the renal community, are today and where we are headed.
Dr. Brunelli: Dr. Flythe, can you give us an overview on the importance of fluid removal?
Dr. Flythe: Fluid removal during dialysis is essential to preventing volume overload—a condition associated with long-term cardiovascular consequences and patient discomfort. However, over the years, the renal community has largely overlooked fluid removal and UF rate (the speed fluid is removed during a hemodialysis treatment)* when considering what constitutes adequate dialysis. Recent research findings on UF rate and related topics have caused the community to reconsider the importance of fluid removal practices as part of the dialysis process.
Dr. Brunelli: What is the new UF rate metric and what will the reporting requirements be for dialysis facilities?
Dr. Flythe: In November 2016, CMS released its most recent Final Rule that specified the components of the End Stage Renal Disease (ESRD) Quality Incentive Program (QIP). The rule included a UF rate reporting measure in the 2020 ESRD QIP. The QIP UF rate measure calculates the proportion of patients dialyzing at a clinic who have UF rates ≥ 13 mL/h/kg. For each patient, this is to be defined as the mean UF rate for the [typically three] treatments that occurred during the week in which monthly clearance assessment (Kt/V) was made.
To enable calculation of UF rate, clinics will have to report via CROWNWeb three new data points: delivered treatment time, UF volume and post-dialysis weight. The UF rate measure will be entering the QIP as a reporting measure—thus clinics will initially be evaluated on whether they reported the necessary data elements. Over time, the presumption is that it will evolve into a clinical performance measure. Dialysis providers are already making clinical protocol changes with this in mind—with some asking staff to limit UF rates to a maximum threshold of 13 mL/h/kg when possible.
Dr. Brunelli: What is the evidence used to establish the UF rate quality measure and how solid is it?
Dr. Flythe: There have been no randomized controlled clinical trials for fluid removal, so, by definition, the evidence base should not be considered strong. However, the link between higher UF rates and bad outcomes is plausible and supported by pathophysiologic studies.
Several observational research studies have found that higher UF rates are associated with higher death rates among individuals on hemodialysis. The risk can go up sharply for UF rates above 10 or 13 mL/h/kg. The most recent study shows that UF rate-related risk actually begins at much lower rates—as low as 6 mL/h/kg. It is important to note that all four studies linking higher UF rates to adverse outcomes are observational in nature.
Imaging studies have shown that higher UF rates are associated with reduced blood flow (often subclinical or asymptomatic) to the heart, brain, gut, liver and kidneys. Repeat episodes of such ischemia likely have long-term negative end-organ sequelae. This pathophysiologic plausibility, combined with the consistency of results across observational studies, has increased confidence in the finding and led to clinical practice change more quickly than is typical for most research findings not yet confirmed by clinical trials.
* The UF rate is mostly dependent on the amount of fluid being removed (the UF volume) and the length of the dialysis treatment (the dialysis treatment time). Weight also contributes to the UF rate calculation.
Upcoming post: Fluid Removal during Hemodialysis: An Interview with Dr. Jennifer Flythe, Part II
Jennifer Flythe, MD, MPH, is a medical director at the University of North Carolina Hospitals Dialysis Services, an assistant professor of medicine at the University of North Carolina at Chapel Hill and a research fellow at Cecil G. Sheps Center for Health Services Research.