The aim of this study is to determine the effect of pregabalin versus dexmedetomidine on the treatment and lasting duration of delirium in fast tracking elderly patients after Coronary Artery Bypass Grafting.

Delirium is an acute brain disorder that involves changes in consciousness, attention, cognition, and perception.The incidence of postoperative delirium (POD) is high among patients undergoing cardiac surgery, ranging from 20 to 50%, and the risk is even higher in the elderly.

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.

The data will available upon reasonable request from the principal investigator