Lidocaine versus ropivacaine for continuous interscalene brachial plexus block after open shoulder surgery

Background: This study compared the postoperative infusion of 1% lidocaine and 0.2% ropivacaine for continuous interscalene analgesia in patients undergoing open shoulder surgery. Methods: Forty patients undergoing open shoulder surgery received an interscalene brachial plexus block with 30 ml of either 1.5% lidocaine (n=20) or 0.5% ropivacaine (n=20), followed by a continuous patient-controlled interscalene analgesia with 1% lidocaine or 0.2% ropivacaine, respectively. A blinded observer recorded the quality of analgesia and recovery of motor function during the first 24 h of infusion. Results: Onset of the block occurred after 7.5 (5-40) min with lidocaine and 30 (10-60) min with ropivacaine (P=0.0005). Postoperative pain intensity was higher with lidocaine than ropivacaine for the first 8h of infusion. The ratio between boluses given and demanded from the pump was 0.5 (0.13-0.7) with lidocaine and 0.7 (0.4-1.0) with ropivacaine (P = 0.005). Rescue IV tramadol was required during the first 24 h of infusion by 16 patients of the lidocaine group (84%) and eight patients of the ropivacaine group (46%) (P = 0.05). At the 16 h and 24 h observation times a larger proportion of patients receiving ropivacaine had complete regression of motor block (70% and 95%) than patients receiving lidocaine (50% and 55%) (P = 0.05 and P = 0.013, respectively). Conclusions: Although 1% lidocaine can be effectively used for postoperative patient-controlled interscalene analgesia, 0.2% ropivacaine provides better pain relief and motor function.