Dexmedetomidine is a highly selective á 2adrenoreceptor agonist recently introduced to anesthesia. It produces dose dependent sedation, anxiolysis and analgesia without respiratory depression. Methods: This prospective randomized doubleblind study was carried out on 100 patients, aged 20 to 70 years with American society of Anesthesiology (ASA) class I and II of either gender, for lower limb surgery, who met the inclusion criteria of spinal anesthesia. The randomly selected patients received Bupivacaine 0.5% 15 mg (3ml) + 0.5 ml of normal saline in group BS (n=50) and Bupivacaine 0.5% 15 mg (3ml) +Dexmedetomidine 10 mcg in 0.5ml NS in group BD(n=50). The onset time to reach sensory and motor level, the regression time of sensory and motor block, requirement of first rescue analgesic, hemodynamic changes and side­effects if any were recorded. Result: The onset time to reach T10 dermatome and modified bromage 3 motor blocks were not significantly different between the groups. Time to achieve sensory regression to L1 in Group BD (284.4±62.84 min) were prolonged as compare to Group BS (149.3±24.91min) (p=0.00). The regression time of motor block to reach modified bromage 0 was (379.5±75.42 min) and (231.6 ±44.55 min) in group BD and BS respectively (p=0.004). The first rescue analgesic was required at 200.90 ± 40.33 min and 327.60 ± 60.05 min in group BS and group BD respectively, were comparable (p=0.104). Conclusion: Intrathecal Dexmedetomidine as an adjuvant to intrathecal Bupivacaine prolong sensory and motor block with minimal side effects. So it is an attractive alternative choice for long duration surgery.

Keywords: Bupivacaine; Dexmedetomidine; Lower Limb Surgery; Spinal Anesthesia.