EEG-based Depth of Anesthesia-monitoring, Effects on Dosage and Cognition

Depth of anesthesia-monitoring based on EEG changes demands knowledge about the effects of the different anesthetic medications on EEG waveforms. The investigators want to investigate the use of the raw-EEG waveform in addition to indexes (BIS) and EEG spectrogram analyses for depth of anesthesia monitoring. The investigators hypothesize that with the use of this monitoring, anaesthesia providers will be able to better individualize the dosage of anesthetic drugs, and that this will reduce the total consumption of anesthetic medication , thus reducing time to wake-up after surgery. Some studies have indicated that too deep anesthesia, confirmed by "burst-suppression" or isoelectric-EEG , is associated with increased postoperative cognitive dysfunction (POCD). The investigators will therefore assess the patients with the Cambridge Neuropsychological Test Automated Battery tests in mild cognitive impairment (CANTAB-MCI) cognitive function assessment tool.