The aim of this study is to compare the effect of perioperative administration of pregabalin versus dexmedetomidine on the prevalence and lasting duration of delirium in elderly patients after cardiac surgery.

Pregabalin is a beta-isobutyl of GABA with chemical similarity to gabapentin . Pregabalin binds to the alpha-2-delta subgroup of calcium channels, thereby reducing excitatory neurotransmitter release and preventing hyperalgesia and central sensitization . Pregabalin is used as anticonvulsant but has also been used as analgesic for neuropathic pain and, lately, for postoperative pain, in an attempt to reduce opioid consumption and prevent progression to chronic pain.

Dexmedetomidine with its broad range of effects including easily controllable sedation, analgesia, and anxiolysis still enables the caring medical team to interact with the patient. It reduces the activity while still maintaining the reactivity of neurons in the locus coeruleus. Therefore, it is an appealing alternative to traditional sedatives such as propofol and benzodiazepines.

Inclusion Criteria:

• ≥ 65 years of age both genders American Society of Anesthesiologists (ASA) physical status classification II or III scheduled for cardiac surgery.

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 be upon reasonable request from the principal investigator

for one year after completion of the study

The research solutions will be formulated by a devoted pharmacist who had no further involvement in the trial. Intraoperative and postoperative parameters will be examined by a second anesthesiologist who was unaware of group assignment.