title: Physician-Directed Versus Computerized Closed-Loop Control of Blood Pressure Using Phenylephrine in a Swine Model.
abstract: Vasopressors provide a rapid and effective approach to correct hypotension in the perioperative setting. Our group developed a closed-loop control (CLC) system that titrates phenylephrine (PHP) based on the mean arterial pressure (MAP) during general anesthesia. As a means of evaluating system competence, we compared the performance of the automated CLC with physicians. We hypothesized that our CLC algorithm more effectively maintains blood pressure at a specified target with less blood pressure variability and reduces the dose of PHP required.
  
  
  
  In a crossover study design, 6 swine under general anesthesia were subjected to a normovolemic hypotensive challenge induced by sodium nitroprusside. The physicians (MD) manually changed the PHP infusion rate, and the CLC system performed this task autonomously, adjusted every 3 seconds to achieve a predetermined MAP.
  
  
  
  The CLC maintained MAP within 5 mm Hg of the target for (mean ± standard deviation) 93.5% ± 3.9% of the time versus 72.4% ± 26.8% for the MD treatment (P = .054). The mean (standard deviation) percentage of time that the CLC and MD interventions were above target range was 2.1% ± 3.3% and 25.8% ± 27.4% (P = .06), respectively. Control statistics, performance error, median performance error, and median absolute performance error were not different between CLC and MD interventions. PHP infusion rate adjustments by the physician were performed 12 to 80 times in individual studies over a 60-minute period. The total dose of PHP used was not different between the 2 interventions.
  
  
  
  The CLC system performed as well as an anesthesiologist totally focused on MAP control by infusing PHP. Computerized CLC infusion of PHP provided tight blood pressure control under conditions of experimental vasodilation.
authors.affiliation: From the *Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas; †Department of Mechanical Engineering, University of Houston, Houston, Texas; and ‡Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston, Texas.
authors.forename: Nicole Ribeiro
authors.initials: NR
authors.lastname: Marques
authors.forename: William E
authors.initials: WE
authors.lastname: Whitehead
authors.forename: Upendar R
authors.initials: UR
authors.lastname: Kallu
authors.forename: Michael P
authors.initials: MP
authors.lastname: Kinsky
authors.forename: Joe S
authors.initials: JS
authors.lastname: Funston
authors.forename: Taoufik
authors.initials: T
authors.lastname: Wassar
authors.forename: Muzna N
authors.initials: MN
authors.lastname: Khan
authors.forename: Mindy
authors.initials: M
authors.lastname: Milosch
authors.forename: Daniel
authors.initials: D
authors.lastname: Jupiter
authors.forename: Karolos
authors.initials: K
authors.lastname: Grigoriadis
authors.forename: George C
authors.initials: GC
authors.lastname: Kramer
mesh_terms: D000465:Algorithms; D000764:Anesthesia, Closed-Circuit / Q000379:methods*; D000768:Anesthesia, General; D000776:Anesthesiology; D000818:Animals; D001331:Automation; D001794:Blood Pressure / Q000187:drug effects*; D003201:Computers; D018592:Cross-Over Studies; D004360:Drug Therapy, Computer-Assisted; D006801:Humans; D007022:Hypotension / Q000188:drug therapy; D008991:Monitoring, Physiologic; D009599:Nitroprusside / Q000008:administration & dosage; D010656:Phenylephrine / Q000008:administration & dosage*; D010820:Physicians; D015203:Reproducibility of Results; D013552:Swine; D014662:Vasoconstrictor Agents / Q000008:administration & dosage*; D014664:Vasodilation
chemical_list: D014662:Vasoconstrictor Agents; D009599:Nitroprusside; D010656:Phenylephrine