The study method was a step-up/step-down sequence model where the dose for following patients was determined by the outcome of the preceding block. The starting concentration of lidocaine was 1.5 % mixed with fentanyl 75 ug. All patients receive 13mL of lidocaine with fentanyl 75ug. The concentration of lidocaine for subsequent patients is determined by the outcome in the previous patient according to up and down sequential allocation in 0.1% increments. In the case of block failure, the concentration of lidocaine was increased by 0.1%.

Conversely, block success resulted in a reduction in concentration by 0.1%.

The occurrence of sensory block up to at T 12 and motor function score of 3 or more on the modified Bromage scale were considered characteristics of a successful block. Moreover, the surgery should be concluded without any complementary analgesia to confirm the success of the anesthetic procedure.