The aim of this study is to observe the antidepressant effect of low-dose esketamine in obese patients with preoperative depression and seeking bariatric surgery. We speculate that intraoperative infusion and the addition of a small dose of esketamine to the postoperative analgesic pump can help reduce the proportion of patients with depression after surgery, and may further improve postoperative recovery, reduce the use of postoperative opioids, shorten postoperative hospital stay, and improve postoperative quality of life of patients.

Inclusion Criteria:

• Age ≥18 years old and <65 years old
• Patients with a BMI greater than 35 kg/m^2
• Hamilton Depression score ≥7 points
• Planned to undergo elective laparoscopic sleeve gastrectomy

Exclusion Criteria:

• ASA ≥ grade IV
• Those who have had or are currently suffering from mental disorders other than anxiety and depression, such as schizophrenia, bipolar disorder, organic mental disorders, etc.
• Those who are unable to cooperate in completing the scale assessment
• Have received ketamine/esketamine treatment, or are allergic to ketamine/esketamine
• Clarify ischemic cardiomyopathy or severe liver and kidney dysfunction (Child pugh grade C, CKD stage G5)
• People with opioid dependence and those who have been taking various types of painkillers for a long time (more than 3 months)
• Participate in other research