title: Closed-loop assisted versus manual goal-directed fluid therapy during high-risk abdominal surgery: a case-control study with propensity matching.
abstract: BACKGROUND
  Goal-directed fluid therapy strategies have been shown to benefit moderate- to high-risk surgery patients. Despite this, these strategies are often not implemented. The aim of this study was to assess a closed-loop fluid administration system in a surgical cohort and compare the results with those for matched patients who received manual management. Our hypothesis was that the patients receiving closed-loop assistance would spend more time in a preload-independent state, defined as percentage of case time with stroke volume variation less than or equal to 12%.
  
  
  METHODS
  Patients eligible for the study were all those over 18 years of age scheduled for hepatobiliary, pancreatic or splenic surgery and expected to receive intravascular arterial blood pressure monitoring as part of their anesthetic care. The closed-loop resuscitation target was selected by the primary anesthesia team, and the system was responsible for implementation of goal-directed fluid therapy during surgery. Following completion of enrollment, each study patient was matched to a non-closed-loop assisted case performed during the same time period using a propensity match to reduce bias.
  
  
  RESULTS
  A total of 40 patients were enrolled, 5 were ultimately excluded and 25 matched pairs were selected from among the remaining 35 patients within the predefined caliper distance. There was no significant difference in fluid administration between groups. The closed-loop group spent a significantly higher portion of case time in a preload-independent state (95 ± 6% of case time versus 87 ± 14%, P =0.008). There was no difference in case mean or final stroke volume index (45 ± 10 versus 43 ± 9 and 45 ± 11 versus 42 ± 11, respectively) or mean arterial pressure (79 ± 8 versus 83 ± 9). Case end heart rate was significantly lower in the closed-loop assisted group (77 ± 10 versus 88 ± 13, P =0.003).
  
  
  CONCLUSIONS
  In this case-control study with propensity matching, clinician use of closed-loop assistance resulted in a greater portion of case time spent in a preload-independent state throughout surgery compared with manual delivery of goal-directed fluid therapy.
  
  
  BACKGROUND
  ClinicalTrials.gov Identifier: NCT02020863. Registered 19 December 2013.
authors.affiliation: Department of Anesthesiology & Perioperative Care, UC Irvine Medical Center, 101 The City Drive South, Orange, CA, 92868, USA. jrinehar@uci.edu.
authors.forename: Joseph
authors.initials: J
authors.lastname: Rinehart
authors.affiliation: Department of Anesthesiology and Intensive Care, Louis Pradel Hospital, Hospices Civils de Lyon, 60 avenue du Doyen Lepine, 69300, Bron, France. marclilot@hotmail.com.
authors.forename: Marc
authors.initials: M
authors.lastname: Lilot
authors.affiliation: Department of Anesthesiology & Perioperative Care, UC Irvine Medical Center, 101 The City Drive South, Orange, CA, 92868, USA. chriskl2@uci.edu.
authors.forename: Christine
authors.initials: C
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology & Perioperative Care, UC Irvine Medical Center, 101 The City Drive South, Orange, CA, 92868, USA. alexandre_joosten@hotmail.com.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Joosten
authors.affiliation: Department of Anesthesiology & Perioperative Care, UC Irvine Medical Center, 101 The City Drive South, Orange, CA, 92868, USA. trishh@uci.edu.
authors.forename: Trish
authors.initials: T
authors.lastname: Huynh
authors.affiliation: Department of Anesthesiology & Perioperative Care, UC Irvine Medical Center, 101 The City Drive South, Orange, CA, 92868, USA. canalesc@uci.edu.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Canales
authors.affiliation: Department of Surgery, UC Irvine Medical Center, 101 The City Drive South, Orange, CA, 92868, USA. dkimagaw@uci.edu.
authors.forename: David
authors.initials: D
authors.lastname: Imagawa
authors.affiliation: Department of Surgery, UC Irvine Medical Center, 101 The City Drive South, Orange, CA, 92868, USA. demirjia@uci.edu.
authors.forename: Aram
authors.initials: A
authors.lastname: Demirjian
authors.affiliation: Department of Anesthesiology & Perioperative Care, UC Irvine Medical Center, 101 The City Drive South, Orange, CA, 92868, USA. mcanness@uci.edu.
authors.forename: Maxime
authors.initials: M
authors.lastname: Cannesson
mesh_terms: D000005:Abdomen / Q000601:surgery*; D000368:Aged; D000768:Anesthesia, General; D016063:Blood Loss, Surgical / Q000517:prevention & control; D002302:Cardiac Output / Q000502:physiology; D016022:Case-Control Studies; D013505:Digestive System Surgical Procedures / Q000379:methods* / Q000592:standards; D005240:Feasibility Studies; D005260:Female; D005440:Fluid Therapy / Q000295:instrumentation / Q000379:methods*; D019983:Guideline Adherence; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D057216:Propensity Score; D012151:Resuscitation; D013318:Stroke Volume / Q000502:physiology