Background:Spinal anesthesia is considered as a reasonable anesthetic option in lower abdominal and lower limb surgery.This study was to determine the dose-response of intrathecal ropivacaine in patients with scarred uterus undergoing cesarean delivery under combined spinal-epidural anesthesia.Methods:Seventy-five patients with scarred uterus undergoing elective cesarean delivery under combined spinal-epidural anesthesia were enrolled in this randomized,double-blinded,dose-ranging study.Patients received 6,8,10,12,or 14 mg intrathecal hyperbaric ropivacaine with 5 μg sufentanil.Successful spinal anesthesia was defined as a T4 sensory level achieved with no need for epidural supplementation.The 50％ effective dose (ED50) and 95％ effective dose (ED95) were calculated with a logistic regression model.Results:ED50 and ED95 ofintrathecal hyperbaric ropivacaine for patients with scarred uterus undergoing cesarean delivery under combined spinal-epidural anesthesia (CSEA) were 8.28 mg (95％ confidence interval [CI]:2.28-9.83 mg) and 12.24 mg (95％ CI:10.53-21.88 mg),respectively.Conclusion:When a CSEA technique is to use in patients with scarred uterus for an elective cesarean delivery,the ED50 and ED95 of intrathecal hyperbaric ropivacaine along with 5 μg sufentanil were 8.28 mg and 12.24 mg,respectively.In addition,this local anesthetic is unsuitable for emergent cesarean delivery,but it has advantages for ambulatory patients.