To Study the Efficacy of Ropivacaine (0.75%) With or Without Butorphanol As an Adjuvant in Single Shot Epidural Anaesthesia in Lower Limb Orthopedic Surgeries. Int Jour of Biomed Res 2014, 5 (12), 725-730. https://doi.org/10.7439/ijbr.v5i12.847.