title: Closed-loop fluid resuscitation: robustness against weight and cardiac contractility variations.
abstract: BACKGROUND
  Surgical patients present with a wide variety of body sizes and blood volumes, have large differences in baseline volume status, and may exhibit significant differences in cardiac function. Any closed-loop fluid administration system must be robust against these differences. In the current study, we tested the stability and robustness of the closed-loop fluid administration system against the confounders of body size, starting volume status, and cardiac contractility using control engineering methodology.
  
  
  METHODS
  Using an independently developed previously published hemodynamic simulation model that includes blood volumes and cardiac contractility, we ran a Monte-Carlo simulation series with variation in starting blood volume and body weight (phase 1, weight 35-100 kg), and starting blood volume and cardiac contractility (phase 2, contractility from 1500 [severe heart failure] to 6000 [hyperdynamic]). The performance of the controller in resuscitating to the target set point was evaluated in terms of milliliters of blood volume error from optimal, with <250 mL of error defined as "successful."
  
  
  RESULTS
  One thousand simulations were run for each of the 2 phases of the study. The phase 1 mean blood volume error ± SD from optimal was 25 ± 59 mL. The phase 2 mean blood volume error from optimal was -60 ± 89 mL. The lower 95% Clopper-Pearson binomial confidence interval for resuscitation to within 250 mL of optimal blood volume for phase 1 and 2 was 99.6% and 97.1%, respectively.
  
  
  CONCLUSIONS
  The results indicate that the controller is highly effective in targeting optimal blood and stroke volumes, regardless of weight, contractility or starting blood volume.
authors.affiliation: From the *Department of Anesthesiology and Perioperative Care, University of California Irvine, Orange, California; and †Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Joseph
authors.initials: J
authors.lastname: Rinehart
authors.forename: Christine
authors.initials: C
authors.lastname: Lee
authors.forename: Maxime
authors.initials: M
authors.lastname: Cannesson
authors.forename: Guy
authors.initials: G
authors.lastname: Dumont
mesh_terms: D000776:Anesthesiology / Q000295:instrumentation* / Q000379:methods*; D001794:Blood Pressure; D001810:Blood Volume; D001835:Body Weight; D002302:Cardiac Output; D003198:Computer Simulation; D005246:Feedback; D005440:Fluid Therapy / Q000295:instrumentation / Q000379:methods*; D006439:Hemodynamics; D006801:Humans; D008955:Models, Cardiovascular; D016343:Monitoring, Intraoperative / Q000379:methods; D009010:Monte Carlo Method; D009200:Myocardial Contraction / Q000187:drug effects*; D011897:Random Allocation; D015203:Reproducibility of Results; D012151:Resuscitation / Q000295:instrumentation / Q000379:methods*; D012984:Software