Neurocognitive Disorders After Major Surgery in Elderly

The objective of the study is to investigate, in patients aged 70 years and over undergoing major non-cardiac surgery, the effect of electroencephalic (EEG)-guided anesthesia on postoperative neurocognitive disorders when controlling for intraoperative nociception, personalized blood pressure targets and using full information provided by the processed EEG monitor (including burst suppression ratio, density spectral array and raw EEG waveform). This prospective, randomized, controlled trial will be conducted in a single Canadian university hospital. Patients aged 70 years and over, undergoing elective major non-cardiac surgery will be included. The administration of sevoflurane will be adjusted to maintain a BIS value between 40 and 60, a suppression Ratio at 0%, a direct EEG display without any suppression time and a spectrogram with most of the EEG wave frequency within the alpha, theta and delta frequencies in the EEG-guided group. In the control group sevoflurane will be administered to achieve an age-adjusted minimum alveolar concentration of \[0.8-1.2\]. A nociception monitor will guide intraoperative opioids' infusion and individual blood pressure targets will be personalized in both groups. The primary endpoint is the incidence of neurocognitive disorder (NCD) at postoperative day 1 evaluated by the Montréal Cognitive Assessment. Secondary endpoints include the incidence of postoperative neurocognitive disorder at different timepoints and the evaluation of cognitive trajectories among EEG-guided and control groups.