Sample size calculation
ESPB
G*Power 3.1.9.2 (Universitat Kiel, Germany) was used to determine the sample size. The mean (± SD) total morphine consumption (our primary outcome) was 3.43 ± 2.56 mg in ESPB without dexmedetomidine and 1.71 ± 1.79 mg in ESPB with dexmedetomidine according to a previous study (15). In each group, 30 cases were recruited with 0.779 effect size, 95% confidence limit, and 80% power, group ratio 1:1, and three cases were added to overcome dropout.