Optimum programmed intermittent epidural bolus interval time between 8 mL boluses of Ropivacaine 0.1% with sufentanil 0.3 μg/mL with dural puncture epidural technique for labor analgesia: A biased-coin up-and-down sequential allocation trial

Yujie Song, Weijia Du, Yiyi Tao, Qian Li, Fuyi Shen, Zhendong Xu, Zhiqiang Liu