Minimal Effective Dose of Hyperbaric Spinal Bupivacaine for Saddle Block

using a modified Dixon's up-and-down method (using 0.5 mg as a step size) (16). The first patient was tested at a dose 1.5 mg bupivacaine, if patient responded with failed block then the next patient received an increment of 0.5mg bupivacaine, if patient responded with successful block, then the next patient received a decrement of 0.5mg bupivacaine. The research continued until we obtained seven crossover midpoints.