Effect of single-dose dexmedetomidine and non-sedation on postoperative cognitive dysfunction in elderly patients undergoing hip and knee surgery : a randomized controlled trial

INTERVENTION: Experimental Drug,No Intervention No treatment Participants receive intravenous dexmedetomidine at a dose of 0.3 to 0.5 mcg/kg administered over 10 minutes during surgery under spinal anesthesia. Standard perioperative care is provided according to institutional protocols.,Participants undergo hip or knee surgery under spinal anesthesia without dexmedetomidine sedation. Single‐dose Dexmedetomidine,No Sedation Control CONDITION: Dexmedetomidine; Postoperative Cognitive Dysfunction; POCD; Postoperative Delirium; Cognitive Function; Montreal Cognitive Assessment; MMSE; Spinal Anesthesia; Hip Surgery; Knee Surgery; Elderly Patients; Orthopedic Surgery; Sedation; Perioperative Care Postoperative Cognitive Dysfunction Postoperative Delirium Cognitive Impairment Elderly Surgical Patients ; Dexmedetomidine; Postoperative Cognitive Dysfunction; POCD; Postoperative Delirium; Cognitive Function; Montreal Cognitive Assessment; MMSE; Spinal Anesthesia; Hip Surgery; Knee Surgery; Elderly Patients; Orthopedic Surgery; Sedation; Perioperative Care PRIMARY OUTCOME: Postoperative Cognitive Dysfunction 72 hours, 2 weeks and 3 months after surgery Incidence of postoperative cognitive dysfunction assessed using Montreal Cognitive Assessment (MoCA) and Mini‐Mental State Examination (MMSE) SECONDARY OUTCOME: MoCA Score 72 hours, 2 weeks and 3 months after surgery Montreal Cognitive Assessment,MMSE Score 72 hours, 2 weeks and 3 months after surgery Mini‐Mental State Examination,Postoperative Delirium 24 hours and 72 hours after surgery Thai version of the Confusion Assessment Method,Intraoperative Complications During surgery Occurrence of hypotension, bradycardia, and hypoxemia INCLUSION CRITERIA: 1. Patients aged 60 years or older. 2. Scheduled for hip or knee surgery under spinal anesthesia. 3. American Society of Anesthesiologists (ASA) physical status 2‐3