The patients were randomly allocated into 3 groups ( 20 patients each ) to receive intrathecally 3 mL of 0.5 % hyperbaric bupivacaine in combination with 5 mcg of dexmedetomidine ( dexmedetomidine group ) , 1 mg of midazolam ( midazolam group ) or 0.5 mL of 0.9 % saline ( control group ) .