In order to address the ongoing controversy about the utility of electroencephalography guidance of anaesthesia and to potentially help to inform the standard of care going forward, the authors propose a block-randomised, double-blinded, comparative effectiveness trial which hypothesises that EEG-guidance of anesthetic administration prevents postoperative delirium and downstream sequelae, including falls and decreased quality of life. The ENGAGES study will enroll 1232 patients 60 years and older who will undergo elective major surgery at Barnes Jewish Hospital, St. Louis, Missouri, USA, an academic medical centre which is affiliated to Washington University School of Medicine. Perioperative data (including repeated measures data) will be retrieved from MetaVision.