"Want to know the effect of dexmedetomidine during opioid free anesthesia on postoperative recovery after gastrectomy. Patients undergoing open gastrectomy are divided into dexmedetomidine group and control(remifentanil) group, administered during surgery, and compared with the speed of postoperative intestinal function recovery. Based on our institution's previous record, the average recovery time was 6 ± 1.4 days. Given that it is clinically significant to reduce recovery time by 20%, Alpha 0.05 and Power 80% require 31 samples per group, and assuming a 10% dropout rate, the total number of samples needed is 68.Subjects are patients aged 19 to 75 who are subject to open gastretomy planned by a gastric cancer. The exclusion criteria include American Society of Anesthesiology grade 3 or higher, patients who have previously been treated for cancer, patients with cancer other than the stomach, patients with drug allergies, weight less than 60kg, BMI > 30 kg/m2, patients who are unable to communicate and are unable to read consent (e.g., illiteracy, foreigners, etc.). The research method is a Randomized double-blind controlled study, and the assignment of both drugs is unknown and is used to maintain anesthesia in the form of continuous injection during surgery. Primary outcome is the recovery period satisfying the following. 1)intestinal gas passage 2) tolerance of soft bland diet (SBD) for 24 hr. 3) safe ambulation without assistance 4) no requirement iv analgesics after discontinuation of PCA (VAS <4). 5) no abnormal physical signs or laboratory test. The secondary outcomes are maximum VAS, post-operative hospital stay, complications and readmission rate at 3 months F/U time, post-operative period analgesic requirement, incidence of opioid related side effect.

Inclusion Criteria:

-patients undergoing open gastrectomy for gastric cancer

Exclusion Criteria:

• American Society of Anesthesiology grade 3 or higher
• history of chemotherapy
• diagosis of cancer in other organs
• history of drug allergy
• weight less than 60kg
• BMI over 30 kg/m2 patient
• cognitive impairment
• gait disturbance

Patients are divided into the Dexmedetomidine group / control group by random assignment. Using a table of computer-generated random numbers(s), assign 68 people to each county by 34 people. Random tables, in turn, seal the results in an opaque envelope. An anesthesiologist who is unaware of the content of this study and does not participate in the study receives information only about drug administration and is in charge of anesthesia, and does not disclose information about the assigned group to postoperative observers. Also, they don't disclose information about the assigned group to the surgeon.