Background: The aim of this prospective, randomized, double-blind study was to compare the block induced by ropivacaine 0.5% with levobupivacaine 0.33% at the recommended dose range in upper limb surgery. These concentrations have provided equivalent block after epidural analgesia. We hypothesized that the block induced by both local anesthetics at clinical equipotent dose would be similar in axillary block.
Methods: Eighty-six patients received 30 mL of ropivacaine 0.5% (150 mg) or 30 mL of levobupivacaine 0.33% (99 mg) by axillary approach. Sensory and motor blocks were assessed in the 5 main nerve territories of the arm at 2, 5, 10, 15, 20, 25, and 30 mins and every 6 hrs for the first 24 hrs. We used the Student t test and chi test for comparison between groups and an analysis of survival. P < 0.05 was considered statistically significant.
Results: Onset of motor block was 9.0 mins (SD, 5.3 mins) for ropivacaine and 12.4 mins (SD, 7.8 mins) for levobupivacaine (P = 0.02). Time to be considered ready for surgery was similar in both groups: ropivacaine, 25.2 mins (SD, 5.1 mins); and levobupivacaine, 25.3 mins (SD, 6.4 mins) (t = -0.09, P = 0.93). Sensory block was 9.2 hrs (SD, 3.1 hrs) for ropivacaine and 11.3 hrs (SD, 4.1 hrs) for levobupivacaine (P = 0.01).
Conclusions: Onset of motor block was significantly faster for ropivacaine than levobupivacaine (P = 0.02), but the time to be ready for surgery was similar with both drugs. Duration of sensory block was prolonged with levobupivacaine (P = 0.01).