Effect of dexmedetomidine-assisted continuous femoral nerve block analgesia after total knee arthroplasty (TKA)

Abstract

Objective To investigate the effects of dexmedetomidine on ropivacaine for continuous femoral nerve block (CFNB) analgesia after total knee arthroplasty (TKA). Methods Forty patients after TKA were randomly assigned into two groups of T and C (n=20 cases each group). All of the patients received spinal-epidural combined anesthesia, subarachnoid injection of 0.5% isobaric ropivacaine 3 ml, intraoperative epidural space according to the need of surgery an extra 0.375% ropivacaine paid for 3 to 5 ml. Postoperative analgesia with continuous femoral nerve block was performed in both groups, after the puncture of femoral nerve, group T was injected with 0.375% ropivacaine + dexmedetomidine mixed solution 20 ml (with dexmedetomidine 0.6 μg/kg), group C were injected with 0.375% ropivacaine 20 ml. Placement of continuous femoral nerve catheter, two groups of patients were performed operation continuous femoral nerve block analgesia and CFNB with 0.75% ropivacaine 50 ml, added saline diluted to 200 ml (each bag). Background infusion was 4 ml per hour; the demand dose was 4 ml in a lockout interval of 30 minutes. Two groups of patients were recorded rest visual analogue scale (RVAS) and passive visual analogue scale (PVAS) postoperative 6, 24, 48 and 72 h. Serum concentration of tumor necrosis factor-α (TNF-α), interleukin(IL)-1β and IL-6 were measured with double sandwich enzyme-linked immunosorbent assay (ELISA) method before anesthesia and postoperative in 24, 48, and 72 hours. Analgesia-related adverse reactions such as delirium, nausea and vomiting, urinary retention were record. Results Compared to group C, postoperative RVAS and PVAS of 6, 24 and 48 h wrere significantly decreased (P<0.05). Postoperative serum concentrations of TNF-α, IL-1β and IL-6 in 24, and 48 hours in group T were lower than those in group C (P<0.05). Group T incidence of postoperative sinus bradycardia was lower than the group C (P<0.05). Conclusions Dexmedetomidine combined with ropivacaine analgesia may effectively improve the TKA postoperative analgesic effect of CFNB, to reduce the levels of serum inflammatory factors, and depress stress reaction after operation. Key words: Dexmedetomidine/AD; Procaine/AD; Femoral nerve; Nerve block; Arthroplasty, replacement, knee; Analgesia