A comparison between epidural Butorphanol and Tramadol for postoperative analgesia, sedation and side effects using CSEA technique for surgeries below the level of umbilicus. Int J of Biomed & Adv Res [Internet]. 2016 Nov. 28 [cited 2026 Mar. 11];7(11):537-42. Available from: https://ssjournals.co.in/index.php/ijbar/article/view/3730