Statistical analysis
SD
Based on the results of the pretest, the time to first postoperative expulsion was 17.2 ± 6.9 h for patients receiving the opioid-sparing anaesthesia protocol and 27.1 ± 16.2 h for patients receiving the conventional anaesthesia protocol. Taking a test efficacy of 90% and α as 0.05, a sample size of 35 cases per group was obtained using PASS15 software (NCSS LLC, Utah, USA). Considering a 10% nonresponse, 39 cases per group were required.Categorical data were expressed as percentages, and the χ2 test was used for comparison between groups. Continuous data that conformed to a normal distribution were expressed as mean ± SD, and independent samples t-test was used for comparison between groups. Continuous data that did not conform to a normal distribution were expressed as median [25% quartiles, 75% quartiles], and group comparisons were performed using the Mann-Whitney U test or the Kruskal-Wallis test. All statistical analyses were performed using SPSS 25.0 (IBM Corp., Armonk, NY, USA). 