All primary and secondary endpoints will be analyzed on an intent-to-treat basis. Analyses are performed with the use of SPSS 18.0 software. The Student-t test is used to analyze demographic data in the two groups. The incidence of CRBD and side effects between groups are analyzed by Chi-square test, whereas the severity of CRBD (mild, moderate, and severe) is analyzed by Fisher's exact test. NRS scale is analyzed by the Mann-Whitney test. Postoperative tramadol and sufentanil requirement is analyzed by Z test, and the number of patients requiring tramadol for CRBD rescue treatment and sufentanil for postoperative pain will be analyzed with Fisher's exact test. A P value<0.05 is considered significant.