To observe the effect of intraoperative dexmedetomidine on the incidence of postoperative delirium, postoperative analgesic drug requirements and pain scores in elderly patients undergoing major abdominal surgery.

This study is a multicenter, randomized, double-blind, placebo-controlled trial. Three hundred patients undergoing elective major abdominal surgery were randomized to the intervention and control groups. Patients in the intervention group were given a loading dose of 0.6 μg/kg of dexmedetomidine by intravenous infusion within 10 minutes after intubation, followed by a continuous infusion at a rate of 0.4 μg/kg/h until 30 min before the end of the procedure; patients in the control group were given an equal volume of saline. Data were collected at 1-5 days and 1 month postoperative follow-up.

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)