Anesthesia will be standardized (general anesthesia using sevoflurane and fentanyl for maintenance, thiopental for induction and atracurium or rocuronium for neuromuscular blockade). Intraoperatively, the dose of anesthetics will be controlled using an EEG derived index (depth of anesthesia monitoring (Bispectral Index (BIS), Aspect Medical Systems), and end-tidal sevoflurane concentration monitoring). Furthermore, intraoperative bilateral cerebral near-infrared spectroscopy (NIRS) monitoring (NIRO-200, Hamamatsu Photonics, Japan) will be applied. Data will be downloaded directly from the monitors and the anesthesia machine (Dräger Perseus) using ICM+ software.