Inclusion Criteria:  Subject is scheduled to undergo gynecological laparoscopic surgery under a short general anesthesia of less than 2 hours Subject's American Society of Anesthesiologists physical status is I-II. The subject's parent/legally authorized guardian has given written informed consent to participate. Patients in plateau areas are long staying residents in above 3000 meters above sea level for enrollment, while patients in plain areas are long staying residents below 1000 meters above sea level.  Exclusion Criteria:  Subject has a diagnosis of renal or liver failure. Subject has a diagnosis of Insulin dependent diabetes. Subject is allergy and contraindication to any drugs used during general anesthesia. 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. Subject has any contraindication for the use of patient-controlled analgesia (PCA). Subject is pregnant or breast-feeding. Subject is obese (body mass index >30kg/m2).