Effect of ultrasound-guided femoral nerve block with dexmedetomidine and ropivacaine on postoperative analgesia in patients undergoing total knee arthroplasty: a randomized controlled trial.

BACKGROUND

Dexmedetomidine, a potent and highly selective α2-adrenoreceptor agonist, has become a popular adjuvant to local anesthetics. This study was designed to investigate the effect of dexmedetomidine with ropivacaine for femoral nerve block on postoperative analgesia after total knee arthroplasty.

METHODS

Forty-six patients after total knee arthroplasty received ultrasound-guided femoral nerve block with either 0.3% ropivacaine alone (group R) or 0.3% ropivacaine with 0.5 μg/kg dexmedetomidine (group RD). Total 24-h sufentanil consumption, visual analogue scale (VAS) pain scores, frequency of patient-controlled analgesia (PCA) pressed, Ramsay sedation score, the incidence of bradycardia and hypotension, and incidence of postoperative nausea and vomiting (PONV) were recorded.

RESULTS

Compared to group R, the total 24-h sufentanil consumption was significantly reduced (110.76 ± 11.56 vs. 99.09 ± 13.31; P<0.05), the VAS scores were lower at 10 and 12 h postoperatively [3(2-3) vs. 2(1-2) and 3(2-3) vs. 2(1-3), respectively; P<0.05], the frequency of PCA pressed was lower at 8-12 and 12-16-h time intervals [(5(3-6) vs. 2(1-3) and 4(3-4) vs. 2(1-3), respectively; P<0.05]. However, there were no differences in Ramsay's sedation score and the incidence of PONV. Also, no patient experienced bradycardia and hypotension.

CONCLUSIONS

0.5 μg/kg dexmedetomidine with 0.3% ropivacaine for femoral nerve block significantly decreased the total 24-h sufentanil consumption, prolonged and enhanced the analgesic efficacy of ropivacaine, without clinically relevant cardiovascular depression or over-sedation in patients undergoing total knee arthroplasty.