The trial protocol has undergone substantial revisions, including modifications to the primary outcome measure, which fundamentally alter the original study objectives. As these changes are not compatible with the initial registration, we

Postoperative delirium (POD) is a common surgical complication.It is associated with a range of negative outcomes such as delayed postoperative recovery,prolonged hospitalization,additional medical expenditures and higher mortality.

Meanwhile,sleep disorders are not only an important predisposing factor for delirium,but also one of the main symptoms of delirium.Systemic inflammatory responses caused by sleep disorders may be an important mechanism for POD.

Many studies have shown that esketamie may inhibit inflammatory factors and enhance neuroplasticity.

In summary,we felt the need to further explore the therapeutic potential of esketamine in the area of POD as well as postoperative sleep disorders.

Inclusion Criteria:

1. Age ≧ 65 years;
2. ASA Ⅰ-Ⅲ;
3. Elective major non-cardiac surgery;
4. Voluntary signed informed consent.

Exclusion Criteria:

1. People with mental illness;
2. Suffering from serious central nervous system disorders such as arkinson's disease, Alzheimer's disease, etc;
3. Elevated intracranial pressure;
4. Emergency or trauma surgery;
5. Prior history of postoperative delirium or postoperative cognitive decline;
6. The patient has impaired hearing or impaired vision;
7. Suffering from severe systemic underlying diseases (e.g. cardiac insufficiency, malignant arrhythmia, malignant hypertension, hepatic failure, renal failure, etc.);
8. The patient is in chronic pain;
9. The patient is severely malnourished;
10. Patients with stage 3 or 4 malignant tumors, pancreatic cancer, allbladder cancer, cholangiocarcinoma and other tumors with high malignancy and poor prognosis.
11. history of allergy to or contraindication to esketamine;
12. inability or unwillingness to complete questionnaires or clinical testing;
13. Unable or unwilling to use a postoperative intravenous analgesic pump.

Study protocol and de-identified individual participant data could be shared after 1 year after publication with the permission of principle investigator for reasonable usage.

The data could be shared after 1 year after publication with the permission of principle investigator. The duration of the data sharing will be determined by principle investigator after publication.

Study protocol and de-identified individual participant data could be shared after 1 year after publication with the permission of principle investigator. Please email principle investigator if researchers wish to have the data.