The aim of this clinical trial is to understand the effects of dexmedetomidine and esketamine on postoperative sleep in patients undergoing cardiac surgery. The main questions it aims to answer are:

Does dexmedetomidine or esketamine prevent the development of postoperative sleep disturbances? Which one works better? The researchers compared dexmedetomidine and esketamine with saline (a drug-free solvent) to see if dexmedetomidine and esketamine prevented the development of postoperative sleep disturbances.

Participants will:

1. Intraoperative continuous infusion of dexmedetomidine, esketamine or saline until the end of surgery
2. Postoperative sleep was assessed on the first and third postoperative days using a sleep rating scale

Inclusion Criteria:

1. ASA class II-III, NYHA class I-III, EF ≥ 50%
2. Intended to perform cardiac surgery under extracorporeal circulation

Exclusion Criteria:

1. Patients undergoing second heart surgery
2. Patients with mental retardation, deafness, or other conditions that interfere with normal communication
3. Previous neurological or psychiatric disorders
4. Patients with a history of sleep disorders
5. Alcoholics, drug addicts, or psychotropic substance abusers
6. Significant hepatic or renal dysfunction affecting drug metabolism
7. Contraindication to the use of dexmedetomidine or esketamine.