Effect of Transversus Abdominis Plane Block With Compound Lidocaine and Esketamine on Pain After Surgery

Inclusion Criteria:

1. Subject is scheduled to undergo colorectal cancer surgery under general anesthesia
2. Subject's American Society of Anesthesiologists physical status is I-II.
3. The subject's parent/legally authorized guardian has given written informed consent to participate.

Exclusion Criteria:

1. Subject has a diagnosis of bronchial asthma, coronary heart disease, severe hypertension, renal failure or liver failure.
2. Subject has a diagnosis of Insulin dependent diabetes.
3. Subject is allergy and contraindication to local anesthetics or any components of local anesthetics.
4. Subject has a history of chronic pain, a history of alcohol or opioid abuse, pre- existing therapy with opioids, intake of any analgesic drug within 48 hours before surgery.
5. Subject has any contraindication for the use of patient-controlled analgesia (PCA).
6. Subject is pregnant or breast-feeding.
7. Subject is obese (body mass index \>30kg/m\^2).
8. Subject is incapacity to comprehend pain assessment and cognitive assessment.