title: Response surface model predictions of emergence and response to pain in the recovery room: An evaluation of patients emerging from an isoflurane and fentanyl anesthetic.
abstract: BACKGROUND
  Sevoflurane-remifentanil interaction models that predict responsiveness and response to painful stimuli have been evaluated in patients undergoing elective surgery. Preliminary evaluations of model predictions were found to be consistent with observations in patients anesthetized with sevoflurane, remifentanil, and fentanyl. This study explored the feasibility of adapting the predictions of sevoflurane-remifentanil interaction models to an isoflurane-fentanyl anesthetic. We hypothesized that model predictions adapted for isoflurane and fentanyl are consistent with observed patient responses and are similar to the predictions observed in our previous work with sevoflurane-remifentanil/fentanyl anesthetics.
  
  
  METHODS
  Twenty-five patients scheduled for elective surgery received a fentanyl-isoflurane anesthetic. Model predictions of unresponsiveness were recorded at emergence, and predictions of a response to noxious stimulus were recorded when patients first required analgesics in the recovery room. Model predictions were compared with observations with graphical and temporal analyses. Results were also compared with our previous predictions after the administration of a sevoflurane-remifentanil/fentanyl anesthetic.
  
  
  RESULTS
  Although patients were anesthetized, model predictions indicated a high likelihood that patients would be unresponsive (> or = 99%). After the termination of the anesthetic, model predictions of responsiveness well described the actual fraction of patients observed to be responsive during emergence. Half of the patients woke within 2 min of the 50% model-predicted probability of unresponsiveness; 70% woke within 4 min. Similarly, predictions of a response to a noxious stimulus were consistent with the number of patients who required fentanyl in the recovery room. Model predictions after the administration of an isoflurane-fentanyl anesthetic were similar to model predictions after a sevoflurane-remifentanil/fentanyl anesthetic.
  
  
  CONCLUSIONS
  The results confirmed our study hypothesis; model predictions for unresponsiveness and no response to painful stimuli, adapted to isoflurane-fentanyl were consistent with observations. These results were similar to our previous study comparing model predictions and patient observations after a sevoflurane-remifentanil/fentanyl anesthetic.
authors.affiliation: Anesthesiology, University of Utah, 30 North, 1900 East, Room SOM 3C444, Salt Lake City, UT 84132-2304, USA. noah.syroid@hsc.utah.edu
authors.forename: Noah D
authors.initials: ND
authors.lastname: Syroid
authors.forename: Ken B
authors.initials: KB
authors.lastname: Johnson
authors.forename: Nathan L
authors.initials: NL
authors.lastname: Pace
authors.forename: Dwayne R
authors.initials: DR
authors.lastname: Westenskow
authors.forename: Diane
authors.initials: D
authors.lastname: Tyler
authors.forename: Frederike
authors.initials: F
authors.lastname: Brühschwein
authors.forename: Robert W
authors.initials: RW
authors.lastname: Albert
authors.forename: Shelly
authors.initials: S
authors.lastname: Roalstad
authors.forename: Samuel
authors.initials: S
authors.lastname: Costy-Bennett
authors.forename: Talmage D
authors.initials: TD
authors.lastname: Egan
mesh_terms: D000328:Adult; D000700:Analgesics / Q000627:therapeutic use; D000762:Anesthesia Recovery Period; D019162:Anesthetics, Combined / Q000008:administration & dosage / Q000493:pharmacokinetics*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000493:pharmacokinetics*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000493:pharmacokinetics*; D003198:Computer Simulation; D003243:Consciousness / Q000187:drug effects*; D004357:Drug Synergism; D017558:Elective Surgical Procedures; D005240:Feasibility Studies; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage / Q000493:pharmacokinetics*; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008297:Male; D008738:Methyl Ethers / Q000493:pharmacokinetics; D008875:Middle Aged; D008954:Models, Biological; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects*; D010880:Piperidines / Q000493:pharmacokinetics; D011237:Predictive Value of Tests; D011650:Pulmonary Alveoli / Q000378:metabolism; D020127:Recovery of Function; D000077208:Remifentanil; D000077149:Sevoflurane
chemical_list: D000700:Analgesics; D019162:Anesthetics, Combined; D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D008738:Methyl Ethers; D010880:Piperidines; D000077149:Sevoflurane; D007530:Isoflurane; D000077208:Remifentanil; D005283:Fentanyl