Using the statistic method of sequential allocation, we realized a prospective double-blind study in order to establish the minimum local anesthetic concentration (MLAC) of large intrathecal volume of levobupivacaine, during the first stage labour analgesia in spontaneous and induced laboring women.Seventy-five nulliparous, at term, with cervical dilatation <5 cm parturients requesting combined spinal/epidural analgesia, were enrolled. The starting concentration was chosen according to recent literature. Total volume of study solution was 10 ml and efficacy was assessed with a visual analogue pain scale at the height of the uterine contraction.We established that MLAC of levobupivacaine, in 10 ml intrathecal volume, during the first stage of spontaneous and induced labour was 0.0134\% and 0.0195\%, respectively. No complications occurred during the study and the only side effect was shivering, which is common even in other anesthetic techniques. We produced a very selective sensitive block. Neither sympathetic nor motor block occurred.Low intrathecally concentration of local anesthetic allows the anesthetist to reduce the total amount of drug and improves not only the differential blockade between motor and sensitive but also between sympathetic and sensitive fibers
