ED₅₀ and ED₉₅ of intrathecal levobupivacaine with opioids for Caesarean delivery.

Background: This prospective randomized double-blind dose-response study aimed to determine the ED₅₀ and ED₉₅ of intrathecal levobupivacaine combined with morphine and sufentanil for elective Caesarean delivery.

Methods: Parturients undergoing elective Caesarean delivery were included and allocated to five levobupivacaine dose groups (6, 8, 10, 12, or 14 mg). Combined spinal-epidural (CSE) anaesthesia was performed, allowing intrathecal administration of the allocated dose of levobupivacaine with intrathecal morphine 100 µg and intrathecal sufentanil 2.5 µg, and insertion of epidural catheter for completing anaesthesia in the case of failure. The dose was considered as successful if a bilateral T6 sensory block to pinprick occurred in 15 min and if no epidural supplement was required during surgery. A probit regression analysis was performed to calculate the ED₅₀ and ED₉₅ of intrathecal levobupivacaine for Caesarean delivery.

Results: Eighty-five parturients were included. A block to T6 sensory level was reached in 15 min for most of the patients. The ED₅₀ and ED₉₅ of levobupivacaine were 6.2 mg (95% CI: 2.6-7.6) and 12.9 mg (11.1-17.9), respectively. Haemodynamic stability and the rate of nausea and vomiting were similar among groups. Greater doses of levobupivacaine were associated with increased motor block duration.

Conclusions: When combined with intrathecal sufentanil 2.5 µg and intrathecal morphine 100 µg, the ED₉₅ of intrathecal levobupivacaine is 12.9 mg for Caesarean delivery. If doses of levobupivacaine less than the ED₉₅, particularly near the ED₅₀, are used, these doses should be administered under a CSE technique.