Kidney Week

Abstract: FR-PO0479

Defining the Optimal Ultrafiltration Rate to Reduce Mortality in Hemodialysis: Target Trial Emulation in a Multinational Cohort

Session Information

• Dialysis: Hemodiafiltration, Ultrafiltration, Profiling, and Interdialytic Symptoms
  November 07, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Dialysis

• 801 Dialysis: Hemodialysis and Frequent Dialysis

Authors

• Pinter, Jule, Julius-Maximilians-Universitat Wurzburg Medizinische Fakultat, Würzburg, BY, Germany

Jule Pinter, MD

• Bernardo, Ana Paula, Fresenius Medical Care, Portugal, Vila Nova de Gaia, Portugal

Ana Paula Bernardo, MD

• Viecelli, Andrea K., The University of Queensland, Brisbane, Queensland, Australia

Andrea K. Viecelli, MD, PhD

• Tunnicliffe, David J., The University of Sydney School of Public Health, Sydney, New South Wales, Australia

David J. Tunnicliffe, PhD, MPH

• Mohebbi, Nilufar, Nephrocare Switzerland, Country Medical Director, Zurich, Switzerland

Nilufar Mohebbi, MD

• Tripepi, Giovanni, National Research Council Institute of Clinical Physiology of Reggio Calabria, Calabria, Italy

Giovanni Tripepi

• Stuard, Stefano, Fresenius Medical Care Italia SpA, Palazzo Pignano, Lombardia, Italy

Stefano Stuard, MD, PhD

Group or Team Name

• EuClid Collaborative Group.

Background

While insufficient ultrafiltration may lead to fluid overload and cardiovascular complications, overly aggressive fluid removal increases the risk of intradialytic hypotension, ischemic injury, and death. Despite growing evidence that high ultrafiltration rates (UFR) are associated with increased mortality, the optimal UFR remains undefined—particularly in relation to sex-specific outcomes.

Methods

Using target trial emulation, we assessed the association between UFR (ml/h/kg, normalized to post-dialysis weight) and all-cause mortality in incident patients receiving hemodiafiltration or high-flux hemodialysis at NephroCare centers across eight European countries (2014–2019). Patients with residual kidney function were excluded. The cohort was drawn from the European Clinical Database 5, an electronic health record repository. Six UFR categories were compared: <6, 6–<8, 8–<10, 10–<12, 12–<14, and ≥14 ml/h/kg (reference group). A nested target trial design and inverse probability of treatment weighting across 45 covariates—including demographics, comorbidities, dialysis parameters, labs, vitals, and medications—were applied to emulate randomization.

Results

Among 19,539 patients (35,455 person-years), 4,125 deaths occurred, yielding a mortality rate of 11.9/100 person-years (95% CI: 11.5–12.2). On average, the UFR was 12.8 ± 4.9 ml/h/kg. Compared to the reference group, we observed a stepwise linear inverse reduction in hazard of all-cause mortality, from 0.83 (95% CI 0.76-0.90) on a rate of 12-14 ml/h/kg to 0.53 (95%CI 0.44-0.63) on a rate of < 6ml/h/kg (figure 1). There was no evident effect modification by gender (lack of substantial heterogeneity, I² values: 0% to 27.1%).

Conclusion

Lower UFR are strongly and independently associated with improved survival in hemodialysis patients, regardless of sex. These findings support individualized fluid management strategies that prioritize lower UFR while preventing chronic fluid overload.

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025vf23mgew