Comparison of 0.125% and 0.2% ropivacaine in continuous lumbar plexus block for postoperative analgesia after total hip arthroplasty

Background: Lower concentrations of ropivacaine in continuous lumbar plexus block (LPB) have not been studied adequately. Thus, we designed this prospective, randomized, comparative study to evaluate the two different concentrations of ropivacaine (0.125% and 0.2%) in continuous LPB for postoperative pain relief following total hip arthroplasty (THA). Materials and Methods: Fifty patients undergoing THA under standardized subarachnoid block have been randomly allocated to receive a continuous infusion of either 0.125% (Group 1) or 0.2% (Group 2) of ropivacaine in LPB done under the guidance of peripheral nerve stimulator. The primary outcome was consumption of tramadol during the first 24 h and the secondary outcomes were quality of sensory and motor blockade and consumption of ropivacaine. Results: The total amount of tramadol did not differ significantly (P = 0.442) between the two groups. Furthermore, the duration of sensory and motor blockade did not differ significantly between the two groups. However, the average consumption of ropivacaine was significantly lower in Group 1 when compared to Group 2 (238.80 mg vs. 380.64 mg, P = 0.0001). Conclusion: Administration of 0.125% of ropivacaine can be a better alternative as it would decrease the total amount of the local anesthetic in continuous LPB.