• Gunter N Schmidt, Petra Bischoff, Thomas Standl, Andreas Gerhardt, Gunnar Lankenau, and Jochen Schulte em Esch.
• Department of Anesthesiology, University Hospital Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany. guschmid@uke.uni-hamburg.de
• Anesth. Analg. 2004 Jan 1;98(1):123-7, table of contents.

UnlabelledAuditory evoked potentials (AEP) can be suppressed by anesthetics dose dependently, but may fail to be registered because of the absence of adequate auditory stimuli. The Alaris AEP monitor includes the "Click Detection" (CD) (generating the message "NO AEP" or "LOW AEP") to detect the loss of auditory stimuli. We investigated the accuracy of the CD in 17 patients awake (AWAKE) and during anesthesia (ANESTHESIA) with accurately placed headphones (HP) and after disconnected HP (No HP) over 5 min each, respectively. Alaris AEP ARX index, CD, and Bispectral Index were recorded each minute. Changes were evaluated with the Friedman and Wilcoxon test. Sensitivity (SEN) and specificity (SPE) and receiver operating characteristic curve were analyzed for the accuracy of the CD. During AWAKE after disconnection of the HP, Alaris AEP ARX index decreased significantly (P < 0.05). The CD was able to detect No HP after 2 min with a SEN of 88% and a SPE of 97%. During ANESTHESIA, no changes were found after HP disconnection. CD detected No HP with a SEN of 100% and a SPE of 20%. The CD of the Alaris AEP monitor is not able to detect unnoticed disconnection of HP during ANESTHESIA.ImplicationsSignal transmission of auditory evoked potentials can be suppressed by anesthetics, but also by disconnection of headphones. In the present study, we demonstrate that even the Alaris AEP monitor with the very new feature "Click Detection" was not able to detect the loss of headphones during general anesthesia with propofol and remifentanil.

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