Fig. 1

Comparisons of fentanyl usage and frequency of hemodynamics fluctuation during operation between groups. a Comparisons of intraoperative fentanyl usage. b Comparisons of intraoperative frequency of hemodynamics fluctuation. The whisker of boxplot stands for the min and max, line in box stands for median. * P < 0.05, ** P < 0.01. Non-block: patients received no caudal block, ROP1.0: patients received 1.0 mL/kg of 0.15% ropivacaine, ROP1.3: patients received 1.3 mL/kg of 0.15% ropivacaine