Midlatency auditory-evoked potentials in the assessment of sedation in cardiac surgery patients.
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.
Musialowicz
Tadeusz
T
Critical Care Research Program, Division of Intensive Care, Department of Anaesthesiology and Intensive Care Medicine, Kuopio University Hospital, Kuopio, Finland.
Hynynen
Markku
M
Yppärilä
Heidi
H
Pölönen
Pekka
P
Ruokonen
Esko
E
Jakob
Stephan M
SM
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
D018686:Anesthetics, Intravenous; D003473:Neuromuscular Nondepolarizing Agents; D015760:Alfentanil; D010197:Pancuronium; D003975:Diazepam; D008874:Midazolam; D015742:Propofol