Dexmedetomidine Combined With Ropivacaine for Postoperative Continuous Femoral Nerve Block

Delirium is common in the elderly after orthopedic surgery and is associated with worse outcomes. Continuous femoral nerve block is frequently used for postoperative analgesia after total knee arthoplasty. The investigators hypothesize that dexmedetomidine, when combined with ropivacaine for continuous femoral nerve block, can reduce the incidence of delirium and improve the long-term outcome in elderly patients after total knee arthroplasty.