Dexamethasone has been recognized as an antiemetic agent after surgeries, and the combination of dexamethasone and tramadol remained stable in solution up to 5 days. In addition, i.v. basal infusion of tramadol is a certified technique in postoperative pain management. We purposed that combined administration of dexamethasone and tramadol adjunct to i.v. morphine is an effective way in treating postoperative pain.

Inclusion Criteria:

1. ASA physical status I-II
2. Chinese
3. 19-64yr
4. Uterus myoma

Exclusion Criteria:

1. Allergy to opioids, a history of the use of centrally-acting drugs of any sort, chronic pain and psychiatric diseases records.
2. Participants younger than 18yr，older than 65yr or pregnancy was eliminated.
3. Due to the significant changes in vital signs might affect cognition of pain and that of sensation, over 20% variation of these records from the baselines or below 92% of SpO2 under 20-40% nasal tube oxygen at any time should be excluded from the study.
4. Those who were not willing to or could not finish the whole study at any time.
5. Any patient who exhibited a combative or incoherent state of PCA analgesia would be excluded from the study.