A Comparision of Midazolam-dexmedetomidine With Dexmedetomidine Alone for Hemodynamic Stability and Quality of Sedation in Elderly Patients Under Spinal Anesthesia

Inclusion Criteria: * aged ≥ 65 years * ASA physical status class I-II * the patients who want sedation during elective lower limb surgery under spinal anesthesia Exclusion Criteria: * contraindication to spinal anesthesia * neurologic or cognitive dysfunction * severe cardiovascular or pulmonary disease * refusal to participation