Results
postoperative pain, pruritus, CRF, nausea & vomiting
ADVERSE EVENTS, CRF
From October 2018 to September 2019, 240 patients were screened and 21 of them were excluded (Fig. 
Trial profile. Data analysis included all patients in the groups to which they were randomly assigned. CRF: case report formWe did not find any significant difference in the demographic data between oxycodone and tramadol groups (P > 0.05, Table 
Comparison of demographic data between oxycodone & tramadol groupsSurgery types(orthopedic/urinary/general/neuro/vascular)Neither oxycodone nor tramadol group needed alternative rescue analgesia in PACU. FLACC scores at different time points in PACU were analyzed using a linear mixed-model. Most of the patients from the oxycodone and tramadol groups had well immediate postoperative pain relief (FLACC scores < 4) after extubation in PACU, and there was no significant difference in FLACC scores at 10 min, 20 or 30 min after extubation (P > 0.05, Table After returning to the wards, all patients had adequate postoperative analgesia in the wards (FLACC scores < 4) after the bolus dose administration, and no alternative rescue analgesia was thereby recorded. There was no significant difference in the FAS scores (in response to turning around in bed), incidence rate of bolus analgesia, time spent from PACU discharge to the first bolus dose, No. of boluses administered, bolus-administered amount of opioid (equal to morphine) in the wards between the oxycodone and tramadol groups (P > 0.05, Table 
Comparison the effect of postoperative pain relief between oxycodone & tramadol-PCIAPACU: postoperative anesthesia care unit; PCIA: parent control intravenous analgesiaParent satisfaction scores were analyzed using a linear mixed-model. There was no significant diffidence in parent satisfaction scores between the oxycodone and tramadol group at either 3 h (P = 0.553), 24 h (P = 0.553) or 48 h (P = 0.834) after surgery (Fig. 
Comparison of parent satisfaction scores between oxycodone and tramadol group. * P < 0.05. +: mean; oxy: oxycodone group; tra: tramadol groupDuring the anesthesia recovery period, there was no significant difference in the consciousness recovery time, extubation time, incidence of nausea & vomiting or pruritus between the oxycodone and tramadol groups (P > 0.05, Table 
Comparison of recovery and adverse events between oxycodone and tramadol in PACUPACU: postoperative anesthesia care unitPCIA: parent control intravenous analgesiaRamsay sedation scores were analyzed using a linear mixed-model. Patients from both oxycodone and tramadol groups showed a time-dependent reduction in Ramsay sedation scores in PACU (P < 0.05). Interestingly, patients from the oxycodone group showed significantly lower Ramsay sedation scores relative to the tramadol group 10 and 20 min after extubation in PACU (Fig. 
Comparison of Ramsay sedation scores between oxycodone and tramadol group. Patient′s sedation level in the PACU (10, 20 and 30 min after extubation) and in the wards (3 h, 24 and 48 h after surgery) was assessed by Ramsay sedation scores. ** P ≤ 0.01. oxy: oxycodone group; tra: tramadol groupWe further compared the other PCIA-related adverse events in the wards. As shown in Table 
Comparison of adverse events between oxycodone and tramadol-PCIA in wards