title: Feasibility study for the administration of remifentanil based on the difference between response entropy and state entropy.
abstract: BACKGROUND
  Facial electromyography (FEMG) may have utility in the assessment of nociception during surgery. The difference between state entropy (SE) and response entropy (RE) is an indirect measure of FEMG. This study assesses an automated algorithm for remifentanil administration that is based on maintaining an entropy difference (ED) that is less than an upper boundary condition and greater than a lower boundary condition.
  
  
  METHODS
  The algorithm was constructed with a development set (n = 40), and then automated and studied with a validation set (n = 20) of patients undergoing anterior cruciate ligament repair. The percentage of time that the ED was maintained between the two boundary conditions was determined. Remifentanil and propofol predicted effect-site concentrations (Ce) were determined at surgical milestones and, after drug discontinuation, the time to response to verbal stimulation and orientation was measured.
  
  
  RESULTS
  The median (25th-75th percentile) per cent of time that the ED was recorded between the boundary conditions was 99.3% (98.1-99.8%). Predicted propofol (microg ml(-1)) and remifentanil (ng ml(-1)) Ce (sd), respectively, were 3.5 and 4.0 at induction, 1.9 (0.8) and 7.2 (3.7) at the end of surgery, and 1.1 (0.5) and 3.2 (2.2) at eye opening. The median time to eye opening and orientation was 3.8 and 6.8 min, respectively.
  
  
  CONCLUSIONS
  This feasibility study supports the concept that remifentanil may be delivered using an algorithm that maintains the difference between SE and RE between the upper and lower boundary condition.
authors: Department of Anesthesiology, St Vincent Catholic Medical Centers - St Vincent's Hospital, Manhattan, New York, NY 10011, USA. dmathews@svcmcny.org
authors: D M
authors: DM
authors: Mathews
authors: P M
authors: PM
authors: Cirullo
authors: M M R F
authors: MM
authors: Struys
authors: T
authors: T
authors: De Smet
authors: R J
authors: RJ
authors: Malik
authors: C L
authors: CL
authors: Chang
authors: G G
authors: GG
authors: Neuman
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D000465:Algorithms; D000701:Analgesics, Opioid / Q000008:administration & dosage* / Q000494:pharmacology; D000762:Anesthesia Recovery Period; D018686:Anesthetics, Intravenous; D016118:Anterior Cruciate Ligament / Q000601:surgery; D001364:Awareness / Q000187:drug effects; D004334:Drug Administration Schedule; D016903:Drug Monitoring / Q000379:methods*; D004576:Electromyography / Q000187:drug effects / Q000379:methods; D019277:Entropy; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D009068:Movement / Q000187:drug effects; D010880:Piperidines / Q000008:administration & dosage* / Q000494:pharmacology; D015742:Propofol; D000077208:Remifentanil; D012815:Signal Processing, Computer-Assisted
chemical_list: D000701:Analgesics, Opioid; D018686:Anesthetics, Intravenous; D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol