This study was a multicenter, randomized, double-blind, placebo-controlled trial to treat elderly surgical patients with low-dose midazolam or placebo for anesthesia induction. The incidence of postoperative 7-day delirium was assessed and compared between two groups, to provide valuable reference for clinical practitioners in the use of midazolam in elderly surgical patients.

This study is a multicenter, randomized, double-blind, placebo-controlled trial. A total elderly patients who underwent elective non cardiac surgery were included in the plan and randomly divided into an intervention group and a control group. The intervention group patients were given 2mg midazolam injection (Jiangsu Enhua Pharmaceutical Co., Ltd.) during anesthesia induction; The control group patients were given equal volume physiological saline. Follow up assessment of postoperative delirium and anxiety will be conducted 1-7 days after surgery, and cognitive function follow-up will be conducted 1 month after surgery.

Inclusion Criteria:

1. 65 ≤ Age ≤ 85 years old;
2. Elective surgery under general anesthesia, with an estimated surgery time of ≥ 2 hours;
3. Non cardiac surgery, non neurosurgical surgery;
4. ASA grades I-III;
5. Agree to participate and sign the informed consent form;

Exclusion Criteria:

1. Preoperative history of comorbidities such as depression and schizophrenia;
2. History of neurological disorders, moderate stroke;
3. Long term use of benzodiazepines before surgery;
4. 18.5≤BMI≤30 kg/m2
5. There is cognitive impairment, which is determined based on Mini Mental State Examination (MMSE) scores below the standard threshold;
6. There are communication barriers, such as severe dementia, language barriers, and severe hearing or visual impairments;
7. There are any contraindications for the use of midazolam (contraindications for patients with severe respiratory dysfunction, patients with severe liver and kidney damage, patients with sleep apnea syndrome, and patients known to be allergic to benzodiazepines);
8. Preoperative severe liver and kidney dysfunction;
9. Patients expected to enter the ICU after surgery;