Dexmedetomidine Combined With Ropivacaine for Postoperative Continuous Femoral Nerve Block

Impact of Dexmedetomidine Combined With Ropivacaine for Postoperative Continuous Femoral Nerve Block on Postoperative Delirium and Long-term Oucomes in Elderly Patients After Single Knee Arthroplasty

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.

A growing number of elderly patients undergo total knee arthroplasty. Delirium is a common complication in these patients after surgery and is associated with worse outcomes, including prolonged hospital stay, poor functional recovery, decreased cognitive function, increased health care costs, and elevated mortality rate. Dexmedetomidine has been shown to prolong the duration of nerve block without neurotoxicity and improve postoperative sleep quality. 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.

Inclusion Criteria:

• Elderly patients (≥ 65 years but < 90 years);
• Scheduled to undergo single total knee arthroplasty;
• Planned to receive continuous femoral nerve block for postoperative analgesia.

Exclusion Criteria:

• Refuse to participate in this study;
• Preoperative history of schizophrenia, epilepsy, Parkinsonism, or myasthenia gravis;
• Inability to communicate in the preoperative period because of coma, profound dementia or language barrier;
• Preoperative hemorrhagic disease or coagulopathy (platelet count, prothrombin time and/or activated partial thrombin time below the lower limit of normal);
• Preoperative obstructive sleep apnea (diagnosed as obstructive sleep apnea, or STOP-Bang score ≥3);
• Preoperative sick sinus syndrome, severe sinus bradycardia (< 50 beats per minute), or second-degree or above atrioventricular block without pacemaker;
• Severe hepatic dysfunction (Child-Pugh class C);
• Severe renal dysfunction (requirement of renal replacement therapy before surgery);
• ASA classification ≥ IV or unlikely to survive for more than 24 hours after surgery.