Effect of Intraoperative Dexmedetomidine on Postoperative Delirium in Elderly Patients Undergoing Major Abdominal Surgery

Inclusion Criteria: * Patients over 65 years old * Patients undergoing elective major abdominal surgery * Written informed consent was obtained Exclusion Criteria: * Patients with severe preoperative cognitive impairment (MMSE ≤ 20) who are unable to undergo a follow-up evaluation. * Patients with history of psychiatric or neurological disorders. * Patients with body mass index ≤ 18 or ≥ 30 * Patients with severe bradycardia (heart rate less than 40 beats per minute) * Patients with pathological sinus node syndrome or grade 2 or greater AV block * Patients with severe hepatic or renal insufficiency. * Patients with severe hypertension (systolic blood pressure ≥ 180 mmHg or diastolic blood pressure ≥ 110 mmHg)