Sample size will be based on onset of block. Kaabachi et al16 found a sensory onset of axillary brachial plexus block (with 30 ml of lidocaine 1.5%) of 9 (SD, 3) mins. The sample size required to have an 90% probability of detecting a decrease in the onset time by 40% (level of significance 0.05)) will be 12 patients per group using an unpaired student's t test.