Hyperbaric spinal anesthesia with ropivacaine coadministered with sufentanil for cesarean delivery: a dose-response study.

Adjuvant sufentanil could achieve effective spinal anesthesia with low dose of hyperbaric ropivacaine for cesarean delivery. Two previous studies had calculated the 50% effective dose (ED50) of intrathecal ropivacaine coadministered with sufentanil for cesarean delivery. However, the 95% effective dose (ED95) of intrathecal hyperbaric ropivacaine coadministered with sufentanil for cesarean delivery remains uncertain. This study determined the ED95 of intrathecal hyperbaric ropivacaine coadministered with sufentanil for cesarean delivery. 80 ASA physical status I or II parturients undergoing elective cesarean delivery were enrolled in this prospective, randomized, double-blind investigation. A combined spinal and epidural anesthesia was performed at the L3-L4 interspace. Patients received a dose of spinal ropivacaine coadministered with sufentanil 5 μg diluted to 3.0 ml with normal saline and 0.5 ml of 10% dextrose: 7.5 mg (n = 20), 9.0 mg (n = 20), 10.5 mg (n = 20), or 12 mg (n = 20). An effective dose was defined as a dose that provided bilateral sensory block to T7 within 10 min after intrathecal drug administration and required no epidural top-up for surgery to be completed. The ED50 and ED95 values for successful anesthesia were determined using a logistic regression model. The ED50 (95% confidence interval [CI]) for successful anesthesia was 8.4 (4.0-9.8) mg and the ED95 (95% CI) was 11.4 (9.7-13.9) mg. The results show that the ED95 of intrathecal hyperbaric ropivacaine coadministered with sufentanil 5 μg for cesarean delivery was 11.4 mg. The addition of sufentanil could significantly reduce the dosage of ropivacaine.