The analgesic effect of interscalene block using clonidine as an analgesic for shoulder arthroscopy

Used as the sole analgesic, clonidine produces analgesia after central neural blockade and intraarticular injection but not after axillary block. In this study, we sought to determine whether interscalene clonidine induces analgesia for shoulder arthroscopy. Forty patients scheduled for shoulder arthroscopy were prospectively included in this double-blinded study. Using a nerve stimulator technique, an interscalene catheter was inserted. The patients were randomly divided into two groups. The interscalene group (n = 20) received clonidine 150 micro g in 15 mL of saline through the catheter and 1 mL of subcutaneous saline, and the systemic group (n = 20) received 15 mL of saline through the catheter and clonidine 150 micro g (1 mL) subcutaneously. All patients underwent general anesthesia for surgery. On completion of arthroscopy, all patients received, via a patient-controlled analgesia, on demand a bolus of 8 mL of ropivacaine 0.2% through the catheter with a 1-h lockout period. Postoperative pain was measured every 4 h using the visual analog scale (VAS) for 24 h. Additional postoperative analgesia was available with parenteral nalbuphine if required until VAS < 3. VAS scores in the recovery room were significantly higher in the systemic group compared with the interscalene group (P < 0.0001). Analgesic duration was significantly longer in the interscalene group (P < 0.00001), and ropivacaine consumption was significantly less than in the systemic group (P < 0.0001). No significant difference was observed between groups for nalbuphine consumption. Side effects were comparable in the two groups.

Clonidine administered via an interscalene catheter enhanced analgesia compared with systemic administration. Nevertheless, the adverse effect of clonidine at this dose limits its use for routine management for postoperative analgesia.