Determination of the minimal motor block local analgesic concentration of ropivacaine for analgesia in the first stage of labor by sequential procedure

Objective: To determine the minimal motor block local analgesic concentration(MMLAC) of ropivacaine for epidural analgesia in the first stage of labor.Methods: Thirty ASA I nulliparous women were administered 10 ml bolus of epidural ropivacaine in the first stage of labor.A concentration of 0.5% ropivacaine was applied to the first woman,and the dosage to the next one was up-regulated or down-regulated one level in accordance to the previous woman's response to the concentration.The Brownlee method was used to quantify the MMLAC.Results: The minimal motor blocking concentration of epidural ropivacaine determined by sequential method was 0.673 7% in the first stage of labor,and 95% confidence interval was between 0.651 2% to 0.697 0%.Conclusions: Determination of the MMLAC of ropivacaine may guide the use of ropivacaine in the first stage of labor.