After patient waked, a loading dose of 10 ug sufentanil was given per time according to the patients' pain level and the loading dose was repeated till the pain relived or the RR was less than 10 times per min. Then the patient-controlled analgesia (PCA) pump was attached, and the continuous infusion speed was set at 2 ml/h. The pump was set to give an amount of 0.5ml at each press with a lockout interval of 10min. Patient was observed in the PACU for at least 30 min until the discharge criteria was reached. All the patients were followed-up at 2h, 6h, 24h and 48 h after the surgery. Clinical evaluations included MAP, HR, respiratory rate (RR), SpO2%, total pressing times, total amount of sufentanil, additional analgesic requirement, VAS, numerical rating scale (NRS) and Ramsey sedation scale were recorded. Side effects include nausea and vomiting, urinary retention, pruritus, respiratory depression were also recorded. Overall satisfaction index were inquired as well.