Sample size calculation
In a pilot observation of 20 elderly patients, mean RCSQ score at surgery night was 50 with standard deviation (SD) of 15. We assumed that intraoperative remimazolam would increase the RCSQ score to 60 at surgery night. With statistical significance at 0.05 and power at 90%, the sample size required to detect the difference was 49 patients in each group (PASS 15.0, StataCorp. LP, College Station, TX, USA). Taking a dropout rate of 10%, we planned to enrol 54 patients in each group.