Inclusion Criteria:  Patients over 19 years who underwent laparoscopic gastrectomy for gastric cancer  Exclusion Criteria:  Patients with a history of allergic reactions to drugs Patients with a history of drug addiction Patients with chronic pain who require analgesics Patients with cancer other than the stomach History of hospitalization for psychiatric disorders Patients with sleep apnea Preoperative pulse oximetry (SpO2) < 95 % Moderate or severe hepatic impairment bradycardia (HR<50bpm), hypotension, atrioventricular block, intraventricular or sinus block Body mass index over 35 kg/m2 Blood clotting disorders Pregnant/lactating women Cognitive impairment Unable to read consent form (eg illiterate, foreigner, etc.)