Dexmedetomidine as Adjuvant for FNB in TKA

Dexmedetomidine added to lower concentration of ropivacaine for postoperative analgesia in FNB

ultrasound-guided femoral nerve block, a single bolous of 20 ml ropivacaine (concentration 0.2% for H group or 0.1% for L group) before surgery followed by continuous femoral nerve block using an infusion rate of ropivacaine 0.2% 5 ml/h for postoperative analgesia started right after surgery

All subjects received intravenous patient-controlled analgesia (IV-PCA) pumps to measure additional morphine consumption, which included 50 mg morphine in 50 ml saline: bolus 2 mg; lock out time, 15 minutes.

All the continuous femoral nerve block infusion regimes in the pump were connected to CFNB catheter, which contained only ropivacaine with different concentrations (ropivacaine 0.1% for L group and LD group; ropivacaine 0.2% for H group, 5 ml/h).