Fast awakening from anesthesia is one of the major characteristics of remifentanil-associated anesthetic induction and maintenance, whereas corresponding pain during awakening influences patient's rehabilitation strongly. In addition, such early postoperative pain results in significant stress responses, which displays as further release of stress hormones such as cortisol and β-endorphin as well. How to prevent such acute pain resulting from remifentanil's fast metabolism endows clinical significance. This study is designed to compare the analgesic efficacy of fentanyl, sufentanil and butorphanol delivered after gynecological laparoscopic surgeries that underwent remifentanil induction and maintenance, and investigate corresponding influence on the levels of blood cortisol and β-endorphin.

Inclusion Criteria:

1. ASA physical status I-II
2. Chinese
3. 19-45yr
4. Selective laparoscopic surgeries

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 18 years, older than 45 years 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