However, the epidural technique is not universally successful and the number of patients experiencing inadequate analgesia with this technique is approximately 12-32%. The failure of epidural analgesia is still a frequent clinical problem and needs active management including a new block or other analgesic medication in order to rescue postoperative pain. Previous study showed that the incidence of patients having epidural analgesia with postoperative moderate pain was 20.9% and that with severe pain was 7.8%. In Siriraj Hospital, recent study showed that 19.6% of patients having elective upper abdominal surgery under general anesthesia combined with epidural analgesia reported severe first pain scores in post anesthetic care unit.27 As a result of severe pain, patients needed a number of intervention and management from acute pain service, and finally spent longer time in post anesthetic care unit.