347 - Assessing BIS stimulation response and BIS monitor delay during sedation.

Abstract:

Purpose:
The Bispectral Index Monitoring System (BIS) is an EEG providing a numerical value to measure a sedated patients’ level of hypnosis. What level of BIS obtunds the response to either sharp or pressure like stimuli?. Also, the BIS monitor analysis delay may interfere with correlation between clinical events and BIS values. To evaluate this delay, the time to post-stimulation BIS elevation and the stored BIS buffer when the probe is disconnected will be assessed.

Methods:
After IRB approval, patients recruited for a BIS monitored hypnosis onset sedation bolus response were also assessed for this BIS project. All patients received the same sedative based regimen; Midazolam, Fentanyl and Propofol. Doses were age and weight based and the only difference was the sequence of sedative administration prior to procedure start. On initial LA placement and initial surgical extraction the BIS monitor to computer data stream was real-time highlighted. Also the BIS probe was disconnected to assess the stored buffer both during and after the procedure. Patient movement in response to either stimulation was assessed by two
observers

Results:
We have recruited 17 patients, four patients moved with sharp stimulus (Movers: BIS 65,2. Non movers: BIS 58) and seven with pressure stimulus (Movers: BIS 59.4. Non movers: BIS 59.3). Median time to BIS increase with sharp stimulation was 25 seconds. Median Buffer time was 50 seconds.

Conclusion:
We have demonstrated that there is a BIS delay of about 30 seconds. Further recruitment and analysis is needed to establish a BIS target depth.

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