In this study, the investigators evaluate the effect of total intravenous anesthesia using sufentanil-remimazolam and remifentanil-remimazolam on postoperative pain in patients undergoing laparoscopic gastrectomy.

Inclusion Criteria:

1. 20years or older
2. Scheduled for laparoscopic-assisted gastrectomy
3. American Society of Anesthesiologists(ASA) physical status I and III

Exclusion Criteria:

1. Emergency operation
2. Patients with a history of severe hypersensitivity reaction to dextran 40
3. Patients who cannot use patient controlled analgesia(PCA)
4. Patients with morbid obesity [body mass index (BMI) >35 kg/m2]
5. Patients with history of uncontrolled hypertension (diastolic BP >110mmHg) or DM
6. Patients with history of heart failure (unstable angina, congestive heart failure)
7. Patients with history of liver failure, renal failure, allergic to medicine
8. Patients with history of cerebrovascular disease (cerebral hemorrhage, cerebral ischemia)
9. Patients with history of uncontrolled psychiatric disease (PTSD, anxiety, depression)
10. Patients with obstructive sleep apnea
11. Patients who cannot read the consent form (examples: Illiterate, foreigner)
12. Patients who withdraw the consent