The results of the primary endpoints of this study are expected to be difficult to identify, thus canceling the study to readjust the study plan.

Traditionally, pain control methods based on narcotic analgesics have been used to control severe pain after surgery, but this has resulted in side effects such as vomiting, constipation, dizziness, mental confusion due to drugs, and respiratory depression. This slowed the recovery of the patient after surgery and increased the duration of hospitalization, which had a negative impact on the patient 's prognosis. In addition, research has been conducted on the use of various painkillers in a variety of ways over the past decade to reduce the dose of narcotic analgesics and to increase the effectiveness of pain control, since studies of anesthetics and narcotic analgesics have shown immunosuppressive effects.

This study investigate the effect of multimodal analgesics for postoperative pain control on immune function amd prognosis in patients undergoing laparoscopic colorectal cancer resection.

Inclusion Criteria:

1. elective laparoscopic colorectal resection due to colorectal cancer
2. curative, resectable operation
3. ASA classification Ⅰ-Ⅲ

Exclusion Criteria:

1. elective co-operation due to distance metastasis
2. preoperative chemo/radiation therapy
3. drug allergy to opioid, tramadol, local anesthetics
4. MAOi medication (within 14 days of surgery)
5. decreased hepatic/renal function
6. Patients who can not read the consent form or are not fluent in Korean (illiterate, foreigner
7. pregnant, lactating women
8. palliative surgery