Compare the changes of regional cerebral oxygen saturation during midazolam or dexmedetomidine administration (target bispectrl index 75-80) for spinal anesthesia in the elderly patients over 65 years who undergoing femur surgery.
Compare the changes of regional cerebral oxygen saturation during midazolam or dexmedetomidine sedation for spinal anesthesia in the elderly patients who undergoing femur surgery.