title: Midlatency auditory-evoked potentials in the assessment of sedation in cardiac surgery patients.
abstract: OBJECTIVE
  Midlatency auditory-evoked potentials (MLAEPs) may provide an objective measure of depth of sedation. The aim of this study was to evaluate MLAEPs for measuring sedation in cardiac surgery patients.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  Intensive care unit of a university hospital.
  
  
  METHODS
  Twenty-two patients scheduled for elective coronary artery bypass grafting.
  
  
  METHODS
  MLAEPs were obtained at 5 time points: the day before surgery (baseline), 1 hour before surgery, after premedication, postoperatively during deep (Ramsay 6) and moderate (Ramsay 4) sedation, and the day after surgery.
  
  
  RESULTS
  The latency of the Nb MLAEP component increased from 44 ms (38-60 ms; median, range) at baseline to 49 ms (41-64 ms) after premedication (p = 0.03) and further to 63 ms (48-80 ms) during deep sedation after surgery (P < 0.01). Although a decreasing clinical level of sedation after rewarming was not associated with a significant change in Nb latency (61 ms [42-78 ms]), the MLAEP NaPa amplitude increased from 0.9 muV (0.4-1.6 microV) to 1.3 muV (0.8-3.9 microV; p = 0.01). Nb latency remained increased the day after surgery (49 ms [37-71 ms]) as compared with baseline (p < 0.01).
  
  
  CONCLUSIONS
  MLAEP latencies can reflect subtle changes in auditory perception, while amplitudes seem to change with transition between deep levels of sedation.
authors.affiliation: Critical Care Research Program, Division of Intensive Care, Department of Anaesthesiology and Intensive Care Medicine, Kuopio University Hospital, Kuopio, Finland.
authors.forename: Tadeusz
authors.initials: T
authors.lastname: Musialowicz
authors.forename: Markku
authors.initials: M
authors.lastname: Hynynen
authors.forename: Heidi
authors.initials: H
authors.lastname: Yppärilä
authors.forename: Pekka
authors.initials: P
authors.lastname: Pölönen
authors.forename: Esko
authors.initials: E
authors.lastname: Ruokonen
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Jakob
mesh_terms: D000328:Adult; D000368:Aged; D015760:Alfentanil / Q000627:therapeutic use; D018686:Anesthetics, Intravenous / Q000627:therapeutic use; D002315:Cardiopulmonary Bypass / Q000379:methods; D016292:Procedural Sedation / Q000379:methods* / Q000706:statistics & numerical data; D001026:Coronary Artery Bypass / Q000379:methods*; D003975:Diazepam / Q000627:therapeutic use; D005072:Evoked Potentials, Auditory / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008874:Midazolam / Q000627:therapeutic use; D008875:Middle Aged; D003473:Neuromuscular Nondepolarizing Agents / Q000627:therapeutic use; D010197:Pancuronium / Q000627:therapeutic use; D015742:Propofol / Q000627:therapeutic use; D011446:Prospective Studies
chemical_list: D018686:Anesthetics, Intravenous; D003473:Neuromuscular Nondepolarizing Agents; D015760:Alfentanil; D010197:Pancuronium; D003975:Diazepam; D008874:Midazolam; D015742:Propofol