Monitoring Equipment and Computers 59 Conclusion(s): During sevoflurane anaesthesia, both EEG and EMG arousals are frequently seen. Beta and delta arousal have opposite effects on the Entropy values. EMG arousal is abolished by rocuronium at TOF level 0/4. All anesthe- siologists using these monitors should be familiar with the effects of EMG and EEG arousal patterns and understand why they may cause misleading values. 3AP6-7 Bispectral index for monitoring hypnosis during balanced xenon anaesthesia A. Fahlenkamp, D. Peters, C. Billoet, R. Rossaint, M. Coburn Department of Anaesthesiology, University Hospital Aachen, Aachen, Germany Background and Goal of Study: The noble gas xenon is an anaesthetic with a favourable haemodynamic profile [1]. The role of Bispectral Index (BIS) monitoring for the survey of hypnosis during xenon anaesthesia is discussed controversially [2, 3], but till now has only been investigated for single agent xenon anaesthesia. We analyzed the performance of the BIS during balanced xenon anaesthesia. Materials and Methods: After written informed consent, 60 Patients undergoing abdominal surgery participated in this double-blinded randomized controlled clinical trial and were randomly assigned to receive either balanced xenon or sevoflurane anaesthe- sia with remifentanil titrated to clinical needs. BIS monitoring was blinded to the perform- ing anaesthetist and values were continuously assessed by accessory study personnel. Results and Discussion: 30 patients were enrolled in each group, comparable in respect to age, gender, height, ASA status, baseline systolic blood pressure and baseline heart rate. BIS values during induction and maintenance of xenon anaesthe- sia correlated well with the value range recommended for deep hypnosis and with val- ues obtained during sevoflurane anaesthesia.Bispectral Index monitoring thoroughly indicated an adequate level of hypnosis during balanced xenon anaesthesia guided according to clinical parameters. Controversial results obtained from former studies [2] indicating unpredictable influences of xenon on the BIS were not confirmed. Conclusion(s): We conclude that hypnosis during xenon anaesthesia can suf- ficiently be monitored using the BIS. References: 1 Rossaint R, Reyle-Hahn M, Schulte Am Esch J, et al. Anesthesiology 2003; 98: 6-13. 2 Goto T, Nakata Y, Saito H, et al. Br J Anaesth 2000; 85: 359-63. 3 Laitio RM, Kaskinoro K, Särkelä MO, et al. Anesthesiology 2008; 108:63-70. Acknowledgements: This work was co-sponsored by the University Hospital Aachen and Air Liquide Santé International. 3AP6-8 Joint monitoring of regional cerebral oxygenation and bispectral index during cerebral desaturation in cardiac anaesthesia F. Vieira, A. Lourenço, C. Luís, J. Viterbo Department of Anaesthesiology, Hospital São João E.P.E., Porto, Portugal Background and Goal of Study: Multimodal monitoring is essential to a thor- ough evaluation of neurological status. Near-infrared spectroscopy assesses the balance between oxygen delivery and consumption as regional cerebral oximetry (rSO 2 ) and detects cerebral hypoxia. Bispectral index (BIS) evaluates electric brain activity. Several case reports support its effectiveness as an indi- rect measure of injury, and it predicts neurological outcome in critical patients (1). Nevertheless, BIS and rSO 2 have not yet been evaluated jointly. Our aim was to correlate BIS and rSO 2 during cardiac surgery. Materials and Methods: rSO 2 was monitored in elective cardiac surgery when- ever patients were older than 70 or had either carotid artery stenosis >50% on pre-operative Doppler ultrasound, or previous stroke history on pre-operative Background and Goal of Study: Permutation Entropy PeEn seems to distin- guish “awake” EEG from EEG at unconsciousness using EEG frequency range 0-30Hz reliably [1]. Analyzing frequencies above 30Hz bears the risk to include EMG activity that can overlap with EEG. This abstract raises the question if it may be beneficial to use PeEn and analyze more specific frequency ranges such as the β-band. β-activity is suggested to reflect intracortical signal trans- mission [2] that may be an indicator of consciousness. Loss of consciousness is reflected by a decrease of α and β activity while lower frequencies in the δ and θ range increase. When focussing on β activity, its decrease during loss of consciousness can be evaluated and the analysis becomes independent from low frequency artefacts, e.g. eyeblinks (1-5Hz) or sweat and motion artefacts (<4Hz). Materials and Methods: EEG was recorded during 2 studies with (i) 15 volun- teers undergoing propofol (study 1) and (ii) 15 volunteers undergoing propofol and propofol-remifentanil (study 2) anaesthesia at stable levels “awake” and “general anaesthesia”. PeEn was calculated all sequences for frequency ranges 0.5-7.5Hz (δ, θ); 12-30Hz (β) and 0-30Hz. Pk values were calculated for sepa- rating consciousness from unconsciousness. Results and Discussion: Table 1 shows the Pk values. Table 1 PeEn d=4 Study I Study II Study II (Propofol/Remifentanil) Study II (Propofol) (Propofol) (overall) Pk: beta-band 1 0.998 0.938 0.97 Pk: 0-30Hz 0.95 0.952 0.869 0.92 Pk of distinguishing consciousness from unconsciousness for PeEn (beta-band) and PeEn (0-30Hz) Conclusion(s): Analyzing only β activity seems to be beneficial for some data sets. If δ and θ bands are included in analysis, their activation with increasing anaesthetic level may disturb the result. PeEn tends to remain stable or increase slightly if it is used on these low frequency bands while it decreases in the β range and on the 0-30Hz band. The next step is to test, if a combination of overall PeEn (0-30Hz) and PeEn calculated over selected frequency ranges will result in a better performance for distinguishing con- sciousness from unconsciousness than only PeEn calculated over a wider frequency range. References: 1 Biomed Tech 2006; 51: 89-94. 2 Anesthesiology 2005; 102: 447-471. 3AP6-6 Effect of electromyographic and electroencephalographic arousal on entropy monitoring during sevoflurane anaesthesia with and without neuromuscular blocking agents A. Aho, L.-P. Lyytikäinen, A. Yli-Hankala, K. Kamata, V. Jäntti Department of Anaesthesiology, Tampere University Hospital, Tampere, Finland Background and Goal of Study: Entropy™ is an anaesthetic electroencepha- logram (EEG) monitoring method, yielding two parameters: State Entropy (SE) and Response Entropy (RE). SE reflects the hypnotic level of the patient. RE covers also the electromyogram(EMG)-dominant part of the frequency spec- trum, reflecting the upper facial EMG response to nociceptive stimulation. Skin incision is often associated with an increase in Entropy values. We stud- ied the EEG, EMG, and Entropy values before and after skin incision, and the effect of rocuronium on Entropy and EMG at skin incision during sevoflurane anaesthesia. Materials and Methods: 38 patients were anaesthetized with sevoflurane- nitrous oxide or sevoflurane-nitrous oxide-rocuronium. The biosignal was stored and analyzed off-line to detect EEG patterns, EMG and artifacts. The signal, its power spectrum, SE, RE, and RE-SE values were analyzed 1 minute before and 1 minute after skin incision. EEG arousal was classified as beta (spectral peak at 20 Hz, a decrease in delta activity (< 4 Hz)) or delta (increase in delta, decrease in beta activity). Results and Discussion: EEG arousal appeared in 17/19 and 15/19 patients (n.s.), and EMG arousal in 0/19 and 13/19 patients (P<0.01) with and without rocuronium, respectively. Both beta (n = 30) and EMG arousals increased SE, but delta arousal (n = 2) decreased SE. A significant rise in RE-SE was only seen in patients without rocuronium. Figure 1. RE/SE, sevoflurane concentra- tion, heart rate and spectrogram from the whole study period, and samples of the original biosignal/ its respective power spectra during intubation and skin incision. The characteristic patterns of the biosignal and its power spectrum allowed us to classify beta, delta and EMG arousals. However, they often occur simultaneously and to more accurately detect them, more than one channel should be recorded.