In this exploratory grant, the investigators aim to determine whether two different anesthetic depths as measured by an anesthetic depth monitor can be practiced uniformly by a number of anesthesia providers and with safety across a large group of older surgical patients. The investigators will use a randomized control trial design to randomize 232 patients in receiving "light" vs "deep" anesthesia as measured by an anesthetic depth monitor. Postoperative outcomes will include delirium and cognitive measurements.