Bilateral Bispectral Index, Asymmetries and Post-operative Delirium

The primary objective of the study is to describe the value of interhemispheric asymmetry (ASYM), during the different intra- and peri-operative phases, in those patients who develop or do not develop post-operative delirium (POD) during the first 30 post-operative days and postoperative cognitive disfunction (POCD) in the first 90 post-operative days, in a population undergoing head\&neck and plastic surgery with a priori increased probability of POD.