The purpose of this study is to determine the efficacy and safety of Tropisetron in preventing emergence delirium.

Delirium is a common complication during postoperative period, especially in elderly patients. The presence of postoperative delirium is independently associated with poor recovery, increased length of hospital stay, the development of long-term cognitive decline and increased mortality.

Tropisetron is a 5-HT3A receptor antagonist and is widely used to treat postoperative nausea and vomiting. Previous studies found that tropisetron has positive effect on cognitive function. This study aims to access the efficacy and safety of tropisetron in preventing emergence delirium.

To explore the results differences amongst different patients, subgroup analysis will be conducted according to: a. Age (older than 65 years versus 65 years or younger); b. Surgery type (major surgery versus minor surgery); c. Preoperative MoCA scores (>26 versus 18-26 versus 10-17).

Inclusion Criteria:

1. Written consent given
2. Scheduled to undergo elective non-cardiac surgeries under general anesthesia
3. ASA Physical Score I-III

Exclusion Criteria:

1. Patients with a history of neurological disease, such as Alzheimer disease.
2. Patients with a history of psychiatric disease
3. Patients with a medication history of antipsychotic drugs over the last 30 days prior to enrollment.
4. Unable to complete neuropsychological testing including patients with severe visual or hearing impairment.
5. the Montreal Cognitive Assessment (MoCA) scores below 10
6. Patients who have severe intraoperative adverse events, such as cardiac arrest.
7. Patients with contraindication of tropisetron.