Abstract: FR-PO0189
Neither Prefilter Replacement Fluid nor Dialysate Increases Hemoconcentration in Continuous Kidney Replacement Therapy Circuits
Session Information
- AKI: Mechanisms - 2
November 07, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Acute Kidney Injury
- 102 AKI: Clinical, Outcomes, and Trials
Authors
- Radford, Gwyndolyn Maluki, University of Iowa Hospitals and Clinics, Iowa City, Iowa, United States
- Gopireddy, Naga Sumanth Reddy, University of Iowa Hospitals and Clinics, Iowa City, Iowa, United States
- Khawaja, Imran, University of Iowa Hospitals and Clinics, Iowa City, Iowa, United States
- Grover, Sahil, University of Iowa Hospitals and Clinics, Iowa City, Iowa, United States
- Nizar, Jonathan, University of Iowa Hospitals and Clinics, Iowa City, Iowa, United States
- Griffin, Benjamin R., Iowa City VA Medical Center, Iowa City, Iowa, United States
Background
Filter clotting is a major complication of continuous kidney replacement therapy (CKRT) resulting in blood loss, reduced treatment efficacy, and increased cost. Minimization of filtration fraction (FF), an analog for hemoconcentration within a circuit, is often proposed to prolong filter life. However, how best to calculate FF in the setting of pre-filter replacement fluid and dialysate usage is unclear.
Methods
We prospectively enrolled patients on stable CKRT settings for >24 hours and measured four post-filter hematocrit (HCT) values under varying machine settings to determine hemoconcentration within a circuit, as follows: 1) baseline value, with pre-filter and dialysate flow rates set to zero, 2) total effluent delivered as pre-filter replacement fluid, 3) total effluent delivered as dialysate, and 4) total effluent delivered as post-filter replacement fluid. We allowed at least 10 minutes after changing machine settings before drawing the post-filter HCT, and maintained constant blood flow rate, citrate flow rate, and ultrafiltration rates for all four draws. In patients who were not grossly volume overloaded, ultrafiltration was set to 0 for the duration of the experiment.
Results
Five of a planned 20 patients have been enrolled to date. Measured post-filter HCT values are given in Table 1. Average percent change from the baseline value, akin to FF attributable to effluent flow rates, was -1.7% for pre-filter replacement fluid, -3.3% for dialysate, and 26.1% for post-filter replacement fluid. Post-filter replacement fluid percent change nicely approximated calculated FF, whereas measured percent change for pre-filter replacement fluid was significantly lower than the calculated value.
Conclusion
In this prospective study, there was no appreciable hemoconcentration within CKRT circuits due to pre-filter replacement fluid or dialysate. These findings bring into question the accuracy of current FF calculations in settings of predominant pre-filter replacement fluid or dialysate usage.
Table 1. Measured post-filter hematocrit values under varying effluent flow settings.