Results
Postoperative pain, SD
ADVERSE REACTIONS, ADVERSE EVENT
From March 2022 to December 2022, 90 patients were initially evaluated for eligibility, of whom four patients met the exclusion criteria. Thus, 86 patients were randomized and received the study intervention. Later, four participants in S-ketamine group, two participants in control group were excluded because they were lost to follow-up or had incomplete postoperative QoR-15 assessment. Consequently, 80 patients were analyzed, with 40 patients in each group. The details of patient selection are illustrated in a flow chart (Fig. 
Consolidated Standards of Reporting Trials (CONSORT) flowchart describing patients progress through the studyPatient characteristics and perioperative details of both groups are detailed in Table 
Patients’ demographic and perioperative characteristics (n = 40 in each group)Data are presented as median (interquartile range), mean ± SD or number (percentage). *The global QoR-15 scores and five different subcomponent between the two groups at POD1 and POD2 are reported as median (IQR) in Table 
Postoperative QoR-15 score (n = 40 in each group)0.7890.018*0.000*Data are presented as median (IQR). The median difference (reported with 95% CI) is the median of all pairwise differences between observations in the two groups. It is not the difference between the group medians. *
Comparison of the global QoR-15 scores of S-ketamine and propofol group at PRE, POD1 and POD2 (Cognitive status was determined using MMSE, which was assessed at Pre, POD1, and POD2. In present study, the MMSE scores both at Pre and POD2 showed no statistically difference between the two groups (Postoperative pain intensity of the participants illustrated in Fig. 
The comparison of the VAS scores of patients in two groups. The perioperative adverse reactions and patient’s satisfaction in the two groups are shown in Table 
Adverse events in the perioperative period (n = 40 in each group)Data are presented as median (IQR) or number (percentage). *