ASSESSMENT THE EFFICACY OF SPINAL ANESTHESIA WITH THE DOSE OF 6MG PLAIN ROPIVACAINE ADDED FENTANYL FOR HIP ARTHROPLASTY IN ELDERLY PATIENTS Objective: To evaluate the efficacy and safety of the dose of 6mg intrathecal plain ropivacaine added 30 fentanyl for elderly patients who underwent hip arthroplasty.