Pregabalin Versus Dexmedetomidine for Delirium Treatment After Coronary Artery Bypass Grafting

Inclusion Criteria: * CABG patients ≥ 65 years of age both genders American Society of Anesthesiologists (ASA) physical status classification II or III planned for fast track developed postoperative delirium (POD). Exclusion Criteria: * Patients who had history of psychiatric diseases; inability to communicate; * previous history of POD; preoperative sick sinus syndrome, allergy/sensitivity to pregabalin or dexmedetomidine, severe bradycardia (heart rate \<50 beat per minute), second-degree or above atrioventricular block without pacemaker; severe hepatic or renal insufficiency. * Previous cardiac or thoracic surgery, known diagnosis of depression or other major psychiatric diseases, cognitive impairment or inability to cooperate with the study, renal insufficiency, and history of substance abuse.