title: aepEX monitor for the measurement of hypnotic depth in patients undergoing balanced xenon anaesthesia.
abstract: BACKGROUND
  Previously, we showed a significant difference in the measurements of hypnotic depth by the bispectral index (BIS) and auditory-evoked potentials (AEPs) using the A-line autoregressive index during xenon anaesthesia. In the present study, we evaluate the alternative AEP-based auditory-evoked potential index (aepEX) for the measurement of hypnotic depth in patients undergoing general anaesthesia with xenon.
  
  
  METHODS
  Forty-two patients undergoing elective abdominal surgery were enrolled in this controlled, double-blinded, randomized, clinical study. Patients were randomized to receive either xenon (n=21) or sevoflurane anaesthesia (n=21). During anaesthesia, BIS values were recorded simultaneously with the aepEX monitoring. The anaesthetist performing the anaesthesia was blinded to the hypnotic depth monitors. After surgery, the incidence of recalls and awareness was evaluated.
  
  
  RESULTS
  Patients' characteristics such as gender, age, and weight did not differ between the groups. The aepEX and BIS values behaved similarly during anaesthesia. The comparison of aepEX values during xenon and sevoflurane anaesthesia revealed significantly lower aepEX values in the xenon group after 25 min [xenon: 32.9 (4.8) vs sevoflurane: 39.3 (9.0); P=0.008] and after 35 min [xenon: 31.4 (6.6) vs sevoflurane: 37.0 (6.8); P=0.012]. During anaesthesia, aepEX values correlated with the clinical evaluation of depth of anaesthesia (e.g. >20% changes of the baseline arterial pressure or heart rate, spontaneous breathing and/or intolerance of mechanical ventilation, coughing, abdominal pressing, sweating, eye tearing).
  
  
  CONCLUSIONS
  We found the aepEX monitor to provide index in the range of adequate depth of xenon anaesthesia, when combined with remifentanil infusion in intubated patients undergoing elective abdominal surgery.
authors.affiliation: Department of Anaesthesiology,  RWTH University Hospital, Pauwelsstr. 30, D-52074 Aachen,  Germany.
authors.forename: C
authors.initials: C
authors.lastname: Stoppe
authors.forename: D
authors.initials: D
authors.lastname: Peters
authors.forename: A V
authors.initials: AV
authors.lastname: Fahlenkamp
authors.forename: J
authors.initials: J
authors.lastname: Cremer
authors.forename: S
authors.initials: S
authors.lastname: Rex
authors.forename: G
authors.initials: G
authors.lastname: Schälte
authors.forename: R
authors.initials: R
authors.lastname: Rossaint
authors.forename: M
authors.initials: M
authors.lastname: Coburn
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000762:Anesthesia Recovery Period; D000768:Anesthesia, General; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation; D003243:Consciousness / Q000187:drug effects*; D056805:Consciousness Monitors; D004311:Double-Blind Method; D004569:Electroencephalography / Q000187:drug effects; D005072:Evoked Potentials, Auditory / Q000187:drug effects; D005260:Female; D013509:Gynecologic Surgical Procedures; D006801:Humans; D058926:Intraoperative Awareness; D008297:Male; D008738:Methyl Ethers; D008875:Middle Aged; D010147:Pain Measurement; D011184:Postoperative Period; D000077149:Sevoflurane; D013520:Urologic Surgical Procedures; D014978:Xenon; D055815:Young Adult
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D014978:Xenon