Patients were randomized into two groups, A group and B group. A group and B group patients
are injected intravenous dexmedetomidine after intrathecal injection (IT) of heavy
bupivacaine and injected intravenous dexmedetomidine before IT of heavy bupivacaine,
respectively.
The investigators will compare of hemodynamics and patient's comfortability between two
groups.