This study was conducted in a randomized, double-blind, controlled fashion. Patients were randomly allocated to DXM group or Saline group. DMT group received hyperbaric bupivacaine 0.5% (1.2 ml) (6 mg) in dextrose 8% solution + DMT 0.3 ml (3 µg)－in total, bupivacaine 0.4% (1.5 ml) intrathecally and Saline group received hyperbaric bupivacaine 0.5% (1.2 ml) (6 mg) in dextrose 8% solution + normal saline 0.3 ml －in total, bupivacaine 0.4% (1.5 ml) intrathecally. After spinal block, the level of sensory block, defined as the dermatomal segment with loss of pain sensation to pin-prick with a 22 G hypodermic needle and cold sensation to alcohol swab was measured every 2 min after intrathecal injection. The investigators recorded the peak sensory block level, time to peak block level from intrathecal injection, blood pressure and heart rate, and analgesic supplementation during operation. The maximum motor block level was assessed according to the modified Bromage scale. During postoperative period, the frequency of analgesic requirement, time to the first analgesic request, and pain scores were evaluated by blind investigator.