Comparison of the onset time between 0.375% ropivacaine and 0.25% levobupivacaine for ultrasound-guided infraclavicular brachial plexus block: a randomized-controlled trial

At centers with pressure on rapid operating room turnover, onset time is one of the important considerations for choosing a local anesthetic drug. To hasten the onset of the block, higher concentrations of local anesthetics are sometimes used. However, the use of diluted local anesthetics may be safer. Therefore, we aimed to compare the onset times of equipotential levobupivacaine and ropivacaine at low concentrations for infraclavicular brachial plexus block. Adult patients undergoing upper extremity surgery under ultrasound-guided infraclavicular brachial plexus block at our center were randomly allocated to the levobupivacaine and ropivacaine groups. Infraclavicular brachial plexus block was induced with 0.25% levobupivacaine or 0.375% ropivacaine depending on the assigned group. The degrees of sensory and motor blockade were assessed for 40 min after the administration of local anesthetics. A total of 46 patients were included in the analysis. Infraclavicular brachial plexus block with 0.25% levobupivacaine and 0.375% ropivacaine provided sufficient surgical anesthesia. The sensory onset time of 0.375% ropivacaine was shorter than that of 0.25% levobupivacaine (group R, 15 [15.0–22.5] min; group L, 30 [17.5–35.0] min, p = 0.001). There were no significant differences in other block characteristics and clinical outcomes between the two groups. Thus, when a quicker block onset is required, 0.375% ropivacaine is a better choice than 0.25% levobupivacaine. Trial registration ClinicalTrials.gov (NCT03679897).