〔Abstract〕 Objective To study the effects of different adjuvants in ultrasound-guided quadratus lumborum block on postoperative analgesia after total hip arthroplasty (THA). Methods A total of 90 patients who underwent THA from December 2019 to December 2020 in Foshan First People's Hospital were selected and randomly divided into groups Y, D and R, 30 cases in each group. The operation side of group Y was injected with mixed medicine: ropivacaine 100 mg + dexmedetomidine 1 μg·kg-1 (total 30 mL), and the operation side of group D was injected with mixed medicine: ropivacaine 100 mg + dexamethasone 0.1 mg·kg-1 (30 mL in total), 100 mg of ropivacaine (30 mL in total) was injected on the surgical side of group R. All patients in each group used intravenous analgesia pump (PCIA) after operation. After surgery, 50 mg tramadol was injected intravenously according to the analgesic effect for salvage analgesia. At the same time, the patient's satisfaction score for postoperative analgesia was recorded. The visual analogue scale (VAS) scores of the three groups were recorded at 4, 6, 12, 24, and 48 hours after operation. Statistics of tramadol salvage analgesia and the number of compressions of the analgesic pump within 48 h after surgery. At the same time, the incidence of respiratory depression, nausea and vomiting, and postoperative delirium within 48 hours were recorded. Results There was no significant difference in the VAS scores of each group at 4, 6, and 48 hours after operation (P > 0.05). TheVAS scores of the Y group and D group were lower than that of the R group at 12 and 24 h after the operation, the difference was statistically significant (P < 0.05), and the VAS scores of the Y group and the D group were not different at 12 and 24 h after the operation. Statistical significance (P > 0.05); within 48 hours after surgery, the number of remedies for tramadol in group Y and group D was (1.5 ± 1.1) times and (1.1 ± 0.9) times, and the number of times the analgesic pump was pressed was 2 cases (6.7 %) and 2 cases (6.7 %) were lower than those in the R group (3.5 ± 1.2) and 8 cases (26.7%). The difference was statistically significant (P < 0.05). Moreover, the number of remedy cases of tramadol in group Y and the number of compressions of the analgesic pump were not statistically significant compared with group D (P > 0.05); respiratory depression and postoperative delirium did not appear in the three groups. Nausea and vomiting occurred in 1 case (3.3%) in group Y and 2 cases (6.7%) in group D, both lower than 7 cases in group R (23.3%), the difference was statistically significant (P < 0.05). Moreover, there was no statistically significant difference in the nausea and vomiting rates between group D and group Y (P > 0.05). The postoperative satisfaction score of group Y was (5.8 ± 0.3) points and group D was (5.3 ± 0.3) points, which were higher than those of group R, and the difference was statistically significant (P < 0.05). Moreover, there was no statistically significant difference between the postoperative satisfaction scores of group D and group Y (P > 0.05).ConclusionAdding an adjuvant (dexmedetomidine or dexamethasone) to the ultrasound-guided quadratus lumborum block has a better effect on postoperative analgesia after THA, while reducing adverse reactions and improving patients’ satisfaction with postoperative analgesia Degrees. However, there is no significant difference in efficacy between the two.