#5859 A NEW ULTRAFILTRATION RATE FEEDBACK CONTROLLER FOR ATTAINMENT OF RELATIVE BLOOD VOLUME TARGETS DURING HEMODIALYSIS
Authors: Wang Lin-Chun , Thijssen Stephan , Rivera Lemuel , Tapia Silva Leticia M , Ye Xiaoling (Janice) , Casper Sabrina , Fuertinger Doris , Fuertinger Stefan , Kotanko Peter 
Published: June 2023

Abstract

Background and Aims
Preciado et al. (NDT, 2019) have identified half-hourly relative blood volume (RBV) targets during hemodialysis (HD) that are associated with significantly improved patient survival. Attainment of these RBV targets would necessitate incessant adjustments to the ultrafiltration rate (UFR) by the dialysis nurse, which is logistically not feasible. We developed a proportional-integral controller (Casper et al., Int J Artif Organs, 2022) that takes RBV data from the commercially available CLiC® device as an input and provides UFR suggestions to guide the RBV curve into the desired targets. The clinician pre-specifies the desired UF goal and the maximum allowed upward/downward deviation from this goal. The Controller then optimizes the RBV trajectory within the limits allowed by the clinician's prescription. The present study aimed to characterize the performance of this feedback controller.

Methods
We conducted a single-arm, prospective, interventional pilot study in subjects on chronic HD at three Avantus Renal Therapy dialysis centers in New York City. Subjects were treated with Fresenius 2008T HD machines. RBV was measured with the CLiC® device. CLiC® and HD machine data were fed into a research laptop running the UFR Feedback Controller software. The UFR recommendations (generated every 10 minutes) were evaluated by dialysis nurses, who then either implemented or disregarded them as they deemed clinically appropriate. The nurses were instructed to only override Controller recommendations if medically indicated, but not in an attempt to manage the subjects’ RBV trajectories themselves. RBV target range attainment with the UFR Feedback Controller was compared to standard of care treatments (data obtained retrospectively) in the same subjects.

Results
Fifteen subjects (58.9 ± 15.3 years, dialysis vintage 4.1 ± 2.4 years, baseline interdialytic weight gain 2.6 ± 0.8 L, treatment time 222 ± 28 min) were studied prospectively with the UFR Feedback Controller (63 study visits, 4.2 ± 1.9 visits per subject). Nine subjects contributed at least two complete treatments to each study period (Controller and standard of care, respectively) and were included in this analysis. The probabilities of achieving an RBV within the desired target range for each timepoint, stratified by study period (standard of care versus UFR Feedback Controller), are shown in the Figure. Use of the Controller was associated with a higher rate of RBV target range attainment for every timepoint. We confirmed these results with generalized linear mixed-effects models: Across all RBV target timepoints, use of the Controller was a significant predictor of better RBV target range attainment (P &lt; 0.0001). Use of the UFR Feedback Controller was a significant predictor of RBV target range attainment for timepoints 60, 90, 120, and 150 minutes, and a borderline significant predictor for timepoints 30 and 180 minutes.

Conclusion
Use of this UFR Feedback Controller was associated with a significant and clinically meaningful increase in RBV target range attainment. This technology individualizes the UFR to the patient's plasma refill kinetics during the HD treatment and may assist clinicians with optimizing fluid management in their patients.