Sample size estimation and statistical analysis
In a pretest of 12 patients per group, 1 patient in the hypertonic saline group developed POD and 4 patients in the normal saline group developed POD. The incidence of POD in the two groups was 0.083% and 0.333%, respectively. To detect a clinically significant decrease in the incidence of POD at an α risk of 0.05 (two-tailed) and a power of 80%, we needed a sample size of 38 patients per group (PASS 15.0, CNSS, UT, USA). Based on a dropout rate of approximately 10%, 42 patients were recruited in each group.Data from the trial were analyzed by SPSS 25.0 software. Categorical variables were analyzed by chi-square test, Yates’ continuity corrected Chi-square test or Fisher’s exact test and expressed as numbers and percentages. Student’s 