A continuous interscalene brachial plexus block is a highly effective postoperative analgesic modality after shoulder surgery. However, there is no consensus regarding the optimal basal infusion rate of ropivacaine for a continuous interscalene brachial plexus block. A prospective, double blind study was performed to compare two different basal rates of 0.2% ropivacaine for a continuous interscalene brachial plexus block after shoulder surgery.

Sixty-two patients receiving shoulder surgery under an interscalene brachial plexus block were included. The continuous interscalene brachial plexus block was performed using a modified lateral technique with 30 ml of 0.5% ropivacaine. Surgery was carried out under an interscalene brachial plexus block or general anesthesia. After surgery, the patients were divided randomly into two groups containing 32 each. During the first 48 h after surgery, groups R8 and R6 received a continuous infusion of 0.2% ropivacaine at 8 ml/h and 6 ml/h, respectively. The pain scores at rest and on movement, supplemental analgesia, motor block, adverse events and patient's satisfaction were recorded.

The pain scores, supplemental analgesia, motor block, adverse events and patient's satisfaction were similar in the two groups.

When providing continuous interscalene brachial plexus block after shoulder surgery, 0.2% ropivacaine at a basal rate of 8 ml/h or 6 ml/h produces similar clinical efficacy. Therefore, decreasing the basal rate of CISB is more appropriate considering the toxicity of local anesthetics.