title: Auditory-evoked potentials in bispectral index-guided anaesthesia for cardiac surgery.
abstract: OBJECTIVE
  Midlatency auditory-evoked potentials, as measures of the anaesthetic state, were evaluated at similar levels of bispectral index in cardiac surgical patients maintained with either propofol or isoflurane anaesthesia.
  
  
  METHODS
  Twenty-four patients were randomly allocated to anaesthesia with propofol (n = 12) or isoflurane (n = 12). Bispectral index was maintained below 60 during surgery. Auditory-evoked potentials were collected before induction of anaesthesia, 10 min after intubation, 30 min after sternotomy, during cardiopulmonary bypass at the time of cross-clamping of the aorta and during stable mild hypothermia, after de-clamping of the aorta, and after the operation.
  
  
  RESULTS
  At the pre-determined time points, bispectral index values showed comparable depth of hypnosis in both groups. The latency of the Nb component of midlatency auditory-evoked potentials was significantly increased in the isoflurane group after intubation (P < 0.001) and that of both the Nb and the Pa components after sternotomy (P < 0.001) compared with the propofol group. No differences between the groups were detected with respect to haemodynamic variables. No patient reported recall of intraoperative events.
  
  
  CONCLUSIONS
  After intubation and surgical stimulation, when bispectral index was at a constant level, there was a difference in the Nb and Pa components of the midlatency auditory-evoked potentials between the two anaesthetic regimens, indicating a distinction in the state of anaesthesia. Our results suggest that the parallel use of these two electrophysiological methods can show differences in the components of anaesthesia between various anaesthesia methods in cardiac surgical patients.
authors.affiliation: Kuopio University Hospital, Anaesthesiology and Intensive Care Department, Kuopio, Finland. tadeusz.musialowicz@kuh.fi
authors.forename: T
authors.initials: T
authors.lastname: Musialowicz
authors.forename: M
authors.initials: M
authors.lastname: Niskanen
authors.forename: H
authors.initials: H
authors.lastname: Yppärilä-Wolters
authors.forename: M
authors.initials: M
authors.lastname: Pöyhönen
authors.forename: O
authors.initials: O
authors.lastname: Pitkänen
authors.forename: M
authors.initials: M
authors.lastname: Hynynen
mesh_terms: D000368:Aged; D015760:Alfentanil / Q000494:pharmacology; D000768:Anesthesia, General; D019162:Anesthetics, Combined / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D002315:Cardiopulmonary Bypass; D003243:Consciousness / Q000187:drug effects; D001026:Coronary Artery Bypass; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000187:drug effects*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007530:Isoflurane / Q000494:pharmacology; D008297:Male; D008568:Memory / Q000187:drug effects; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D015742:Propofol / Q000494:pharmacology; D011930:Reaction Time / Q000187:drug effects; D013997:Time Factors
chemical_list: D019162:Anesthetics, Combined; D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D015760:Alfentanil; D007530:Isoflurane; D015742:Propofol