Each patient will receive intrathecal hyperbaric bupivacaine 10 mg in 2.5 ml and 0.5 ml saline with 3 mL total volume. Continous 50 ml saline infusion for 10 min followed by 200 ml saline infusion till the end of surgery.

Each patient will receive dexmedetomidine 5 μg diluted in 0.5ml saline and hyperbaric Bupivacaine 10 mg in 2.5 ml with 3 mL total volume. Continous 50 ml saline infusion for 10 min followed by 200 ml saline infusion till the end of surgery.

Each patient will receive intravenous dexmedetomidine started at a loading dose of 1 μg/kg diluted in 50 ml saline and administered within 10 min as a loading dose, followed by maintenance at a dose of 0.4 μg/kg/h diluted in 200 ml saline till the end of surgery and hyperbaric Bupivacaine 10 mg in 2.5 ml total volume.

Each patient will receive intrathecal hyperbaric bupivacaine 10 mg in 2.5 ml and 0.5 ml saline with 3 mL total volume. Continous 50 ml saline infusion for 10 min followed by 200 ml saline infusion till the end of surgery.

The duration between the administration of spinal block and the first desire for supplemental analgesia (onset of 1st post-operative analgesic dose).

First post-operative analgesic dose will be1 μg/kg intravenous fentanyl when visual analogue pain score (VAS) is 4 or more

Visual analogue score (VAS) between 0 and 10{0= no pain, 10=most severe pain}