Postoperative delirium (POD) is the most common complications (\ 50-60%) in elderly and major challenges to our rapidly growing aging population. Growing evidence suggests a possible role for neuroinflammation in the development of delirium, which is facilitated by a transient increase in blood-brain barrier (BBB) permeability. Lidocaine and dexmedetomidine, commonly used anesthetic adjuncts, have anti-inflammatory properties. Both drugs are reported to have modulatory effect on the intergrity of BBB and associated with a beneficial effect on postoperative neurocognitive dysfunction. In this regard, The investigators aimed to prospectively compare the modulatory effect of the intraoperative administration of dexmedetomidine or lidocaine with a sham control group (normal saline solution) on surgery-induced BBB disruption.