title: Performance of the rapidly extracted auditory evoked potentials index to detect the recovery and loss of wakefulness in anesthetized and paralyzed patients.
abstract: BACKGROUND
  The rapidly extracted auditory evoked potentials index (A-lineTM ARX Index or AAI) has been proposed as a method to measure the depth of anesthesia. A prospective study was designed to assess the performance of AAI to detect the recovery and loss of wakefulness in anesthetized and paralyzed patients.
  
  
  METHODS
  Fourteen adult patients undergoing elective surgery were anesthetized with propofol 1.5 mg kg-1, vecuronium 0.1 mg kg-1 and further propofol 1.0 mg kg-1. Wakefulness was measured by the ability of the patient to respond to command using the isolated forearm technique (IFT). After the patient responded, propofol was infused at 10 mg kg-1. h-1 until wakefulness (responsiveness) was lost. The AAI was recorded continuously throughout the study and analyzed off-line.
  
  
  RESULTS
  The AAI showed a significant difference between the values registered during, 30 s before and 30 s after the recovery, and also between 30 s before and 30 s after the loss of wakefulness. The prediction probability (Pk) values for AAI were 0.786 and 0.864 during the transitions from unresponsiveness to responsiveness and from responsiveness to unresponsiveness. The area under the receiver operating characteristic curve for the responsive and unresponsive values was 0.926 (SE 0.002, 95% CI 0.922-0.931), and the AAI values of approximately 5%, 50% and 95% predicted probability of wakefulness were 19, 29 and 39, respectively.
  
  
  CONCLUSIONS
  The AAI may be a good predictor of recovery and loss of wakefulness for anesthetized and paralyzed patients.
authors.affiliation: Department of Anesthesiology, Shanghai First People's Hospital, Shanghai, China. steeroncn@yahoo.com.cn
authors.forename: S J
authors.initials: SJ
authors.lastname: Ge
authors.forename: X L
authors.initials: XL
authors.lastname: Zhuang
authors.forename: Y T
authors.initials: YT
authors.lastname: Wang
authors.forename: Z D
authors.initials: ZD
authors.lastname: Wang
authors.forename: S L
authors.initials: SL
authors.lastname: Chen
authors.forename: H T
authors.initials: HT
authors.lastname: Li
mesh_terms: D000328:Adult; D000768:Anesthesia, General; D018686:Anesthetics, Intravenous; D002648:Child; D003243:Consciousness; D003877:Dermatitis, Contact; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory; D006801:Humans; D007114:Immunization; D007223:Infant; D008875:Middle Aged; D019148:Neuromuscular Blockade; D003473:Neuromuscular Nondepolarizing Agents; D015742:Propofol; D011446:Prospective Studies; D012815:Signal Processing, Computer-Assisted; D014673:Vecuronium Bromide
chemical_list: D018686:Anesthetics, Intravenous; D003473:Neuromuscular Nondepolarizing Agents; D014673:Vecuronium Bromide; D015742:Propofol