Comparison of BIS and AEP indices for monitoring hypnotic level during sevoflurane anaesthesia
European Society of Anaesthesiologists; 8th Annual Meeting with the Austrian International Congress; Vienna, Austria, 1-4 April 2000
1Department of Cardiac Anaesthesia, Hospital Sant Pau, Barcelona, Spain.
2Polytechnic University of Catalonia, Department ESAII, CREB, Spain
Background: The bispectral analysis of the EEG (BIS) and Middle Latency Auditory Evoked Potentials and their derived indices are both described as good correlates to the hypnotic level during non receptor specific anaesthesia. In this study we have compared the two methods with respect to the following two output variables. 1) Time from loss of consciousness (LOC) until the AEP-index was below 28 and the BIS was below 60. 2) Time from recovery of consciousness (ROC) until the AEP index was above 40 and BIS above 70. FIGURE
Materials and methods: The study was approved by the local ethics committee and data were collected from 12 patients scheduled for cardiac surgery. Induction of anaesthesia was carried out with eight per cent sevoflurane. The AEP was recorded using the A-line AEP-monitor (Danmeter, Odense, Denmark) and the BIS was recorded using the A-2000 BIS monitor (Aspect Medical, Ma, USA). Sevoflurane was administered until LOC, defined as loss of a meaningful response to a verbal command. The gas was closed and the patient was allowed to awake and ROC was registered.
Results and discussion: During induction the AEP index descended to 28 within a mean (SD) time of 47(41) s after LOC and the BIS reached 60 after 63(47) s (no significant difference). During the transition from asleep to awake the AEP index was above 40 on average (SD) 9(6) s after ROC and the BIS index was above 70 within a mean (SD) time 24(8) s after ROC.
Conclusion: Both the AEP-index and the BIS correlated well to LOC and ROC. The AEP index was significantly faster in detecting the transition from asleep to awake.
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