Statistical analysis
Despite the comparison of analgesic effects of different concentrations of ropivacaine under a single shot of SAPB[13]. However, no previous studies have tested the analgesic effect of different concentrations of ropivacaine in continuous SAPB. The sample size was determined according to the primary outcome using Power Analysis and Sample Size (PASS) 15. Following previous reports, we set the VAS non-inferiority margin at 1.3 as an acceptable difference in this study, and the standard deviation is anticipated to be 2.0 cm[15-17], assuming a one-sided type I primary error rate of 2.5% and 80% power. Group L: Group H=1:1, and a minimum sample size of 39 patients for each group was estimated. Considering a 10% rate of potential dropout, a total of 44 patients for each group were finally included.
Data were analyzed using Statistical Package for Social Sciences (SPSS) 26.0 for Windows (SPSS Inc., Chicago Illinois, USA). Descriptive data are shown as the mean (with standard deviation) depending on the (normal or skewed) distribution of data, and categorical data are shown as percentages. Comparisons of categorical data were performed with the chi-square test, and an independent t test was used for numerical data comparisons. All statistical tests were two-sided tests, and p values <0.05 were considered significant.