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Higher Fluid Removal During Dialysis Puts Heavier Patients at Greater Risk

Ariella Mermelstein, a graduate of the Katz School's M.A. in Mathematics, is lead author of a study that appears in the June issue of the Clinical Journal of the American Society of Nephrology.

By Dave DeFusco

An epidemiological study of dialysis patients conducted at the Renal Research Institute with the Katz School of Science and Health found that higher ultrafiltration rates in hemodialysis therapy tailored to body weight may put heavier patients at a higher risk of death.

In their research article in the Clinical Journal of the American Society of Nephrology, Ariella Mermelstein, a 2021 graduate of the Katz School’s M.A. in Mathematics, Jochen Raimann, an adjunct professor in the M.S. in Biotechnology Management and Entrepreneurship, and several of their colleagues reported that the most pronounced increase in death occurred at the currently recommended ultrafiltration threshold of 13 milliliters per hour per kilogram of body weight.

Hemodialysis is the process of purifying the blood of a person whose kidneys are not working normally, while ultrafiltration is the technical process for removing excess fluid from the patient during hemodialysis.

Jochen Raimann, who teaches in the M.S in Biotechnology Management and Entrepreneurship program, is a co-author of the study.

The authors proposed novel algorithms allowing the calculation of maximally permissible ultrafiltration rates based on predefined risk levels. They further estimated the impact of required changes with these novel algorithms on the treatment times in a large retrospective cohort of dialysis patients.

“What our study shows is that there will be an increase in the risk of death with an increase in the ultrafiltration rate,” said Raimann, who is also director of data analytics at the Renal Research Institute. “Scaling of the rate to body weight assumes the human body is a homogenous cylinder filled with fluid. Consequently, employing a threshold of 13 milliliters per hour per kilogram disadvantages larger and heavier patients with a different body composition compared to lighter and smaller patients.”

Mermelstein, the lead author and a senior data analyst at the Renal Research Institute, said the researchers determined that when 10 milliliters per hour per kilogram is exceeded, the risk of death starts increasing in these patients. The proposed novel algorithm allows the calculation of an individualized ultrafiltration rate as three times body weight plus 470 milliliters per hour for women and three times body weight plus 530 milliliters for men.

"The advantage of this algorithm," she said, "would be an evenly distributed risk across different body weights." The study, “Ultrafiltration Rate Levels in Hemodialysis Patients Associated with Weight-Specific Mortality Risks,” involved 396,358 adult patients around the age of 62—57% of them men and 41% with diabetes—who started receiving hemodialysis in Fresenius Kidney Care clinics in the United States between 2015 and 2020.

Mermelstein and Raimann were joined in their work by Yuedong Wang (UC Santa Barbara), Peter Kotanko (Icahn School of Medicine at Mount Sinai) and John Daugirdas (University of Illinois Chicago).

“This paper, confirming that high ultrafiltration rates associated with poor health outcomes, emphasizes the importance of personalized and optimal fluid volume and sodium management,” said Raimann. “Our work shows that individualizing acceptable thresholds of ultrafiltration rates may help improve patient outcomes.”