Comparison of Two Electroencephalogram (EEG)-Derived Indices With Electroencephalogram Signals

Bispectral Index (BIS) and Entropy indices will be compared with each other, and to raw EEG signals in patients receiving sevoflurane anaesthesia. BIS and Entropy numbers often differ significantly from each other during surgery, and the reason for this has not been studied in detail, therefore remaining only poorly understood. BIS and Entropy, together with multi-channel EEG, will be collected and analyzed later on. Course of anaesthesia and surgery will be annotated. All relevant information from anaesthesia monitor will be collected on computer.