Crohn's disease (CD) is a chronic inflammatory disease of the gastrointestinal tract with symptoms evolving in a relapsing and remitting manner. Typically, the peak incidence of CD is 18 to 35 years , which means that patients with CD will be plagued by the disease during their most precious years, and nearly 35% of them will develop depressive symptoms. For 70% of patients with CD who need surgery, the incidence of preoperative depression may be higher. The CD cohort with diagnosable psychological condition has been shown to experience a higher rate of disease exacerbation than the CD cohort without psycho complication. At the same time, this depressive mood may make postoperative recovery more difficult, so it is necessary to alleviate postoperative depression.

Ketamine, a widely used anesthetic, is also used to treat depression. The most used ketamine in clinical practice is racemic ketamine, but its use is associated with many complications such as psychotic adverse effects and neurotoxicity. In recent years, S-ketamine has received attention for better efficacy and fewer complications . In 2019, the Food and Drug Administration (FDA) approved S-ketamine nasal spray for the treatment of refractory depression and subsequently received approval from numerous health authorities around the world. This proves that S-ketamine can provide a rapid antidepressant effect in patients with depression in a non-surgical setting. However, it is inconclusive whether S-ketamine affects surgical patients, mainly because of differences in the type of surgery, the dosage administered, the interaction with analgesics, and the evaluation tools implemented. Studies have shown that small doses of S-ketamine in breast cancer surgery and cervical cancer surgery can reduce postoperative depression. However, the effects of S-ketamine on postoperative depression (POD) and pain in patients with CD have not been studied.

Inclusion Criteria:

1. subjects who volunteered and signed informed consent for the trial, (b) patients aged between 18 and 60, (c) patients with CD who underwent surgery, (d) American Society of Anesthesiologists (ASA) grade Ⅰ~Ⅲ, (e) Hamilton depression score 8-24.

Exclusion Criteria:

1. allergy to narcotic drugs or ketamine used, (b) patients with other serious systemic diseases (including severe heart, kidney, and liver disease), (c) chronic opioid therapy (more than twice a week for more than three months), (d) inability to understand the digital pain scale, (e) Hamilton depression score < 8 or > 24.