P1556HEALTH CARE STAFF ACCEPTANCE OF ULTRAFILTRATION RATE RECOMMENDATIONS MADE BY A NOVEL FEEDBACK CONTROLLER
Authors: Tapia Leticia , Rivera-Fuentes Lemuel , Rogg Sabrina , Thijssen Stephan , Kotanko Peter 
Published: June 2020

Abstract

Background and Aims
Preciado et al. 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 require frequent adjustments to the ultrafiltration rate (UFR) by the dialysis nurse, which is logistically not feasible. We developed a novel proportional-integral controller 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. In this study, we investigated the degree to which the dialysis nurses accepted the UFR recommendations made by this novel feedback controller.

Method
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 rejected them as they deemed clinically appropriate.

Results
Fifteen subjects (58.9 ± 15.3 years, 33% white, 53% black, dialysis vintage 4.1 ± 2.4 years, baseline interdialytic weight gain 2.6 ± 0.8 L, treatment time 222 ± 28 min) were studied. Fifty-six study visits (48 complete, 8 partial) from 14 subjects had analyzable data. Out of 1,038 UFR recommendations made by the Controller, 926 (89.2%) were accepted by the dialysis nurses, while 112 (10.8%) were overridden. In 48% of all 48 complete treatments, the Controller ran without a single override by the nurses. Of the other half of the treatments, about a quarter only saw one override per treatment (only half of which were due to low blood pressure or clinical symptoms). Only 1 of 59 study visits was incomplete due to a staff intervention for medical reasons that disengaged the Controller. For the 25 complete study treatments (from 11 subjects) that had at least one Controller suggestion overridden by the nurses, we analyzed the direction and magnitude of disagreement between the Controller-suggested and the implemented UFR (Fig. 1). Out of a total of 109 overridden Controller suggestions, 20 implemented UFRs were greater than the respective Controller-suggested UFRs (i.e., not indicated for medical reasons). Another 70 implemented UFRs were less than 100 mL/h (on average 49.7 mL/h) lower than the Controller-suggested UFRs (i.e., very mild disagreements). Together, these two categories make up 83% of all “disagreements” between healthcare staff and the Controller, leaving only 19 more pronounced disagreements. Of note, of the 109 UFR overrides, 65 (59.6%) were due to staff preference in the absence of low blood pressure or clinical symptoms; 41 were due to low blood pressure, 2 due to hypotension with clinical symptoms, and 1 due to clinical symptoms without low blood pressure.

Conclusion
The proportion of UFR recommendations generated by this UFR Feedback Controller that were accepted by the nurses was very high (≈90%). Importantly, of the relatively few cases where nurses chose to override the Controller’s recommendation, the majority (≈60%) were due to “staff preference” in the absence of low blood pressure or clinical symptoms. The high rate of “staff preference” overrides is likely owed to the fact that, for this study, the nurses exclusively attended to only one patient (the study subject) at a time for the entire HD session.