because the study is very complicated and cannot be performed in the practice

This study was performed in 131 adult patients undergoing transurethral, urological or lower limb surgery under combined spinal and epidural anesthesia. Patients were stratified according to age: 20-30, 31-40, 41-50, 51-60, 61-70, and 71-80 years. The spinal component of the anesthetic was established by bolus administration of up-and-down doses of 0.75% plain bupivacaine, determined by Dixon's method. The degree of motor block after intrathecal administration of each concentration was evaluated by the modified Bromage and Hip motor function score. The EC50 were estimated from the up-and-down sequences using the method of Dixon and Massey and logistic regression. Other endpoints were included on the basis of sensory block level, duration of motor blockade, hypotension, and vasopressor requirements.

Inclusion Criteria:

- ASA physical status I-II adult patients who were undergoing transurethral, urological or lower limb surgery, primarily under the spinal component of established combined epidural-spinal anesthesia, with the epidural component to be used if there was a need for intra-operative analgesic supplementation or for postoperative analgesia.

Exclusion Criteria:

• Patients with diabetes, obesity, neuromuscular diseases, bleeding diathesis, hypersensitivity to amide local anesthetics, lumbar vertebrae abnormality, chronic back pain, or who were pregnant were excluded from this study

This study was performed in 131 adult patients undergoing transurethral, urological or lower limb surgery under combined spinal and epidural anesthesia.