The aim of this study was to evaluate the sedative effect of dexmedetomidine (DEX) added to ropivacaine for supraclavicular brachial plexus block (BPB) using the bispectral index (BIS).

Sixty patients (American Society of Anesthesiologists physical status 1 or 2, aged 20-65 years) undergoing wrist and hand surgery under supraclavicular BPB were randomly allocated to two groups. Ultrasound-guided supraclavicular BPB was performed with 40 ml of ropivacaine 0.5% and 1 µg/kg of DEX (Group RD) or 0.01 ml/kg of normal saline (Group R). The primary endpoint was the BIS change during 60 min after block. The secondary endpoint was the change in the mean arterial blood pressure (MAP), heart rate (HR), and SpO₂ and the onset time and duration of the sensory and motor block.

In Group RD, the BIS decreased significantly until 30 min after the block (69.2 ± 13.7), but remained relatively constant to 60 min (63.8 ± 15.3). The MAP, HR and BIS were significantly decreased compared with Group R. The onset time of the sensory and motor block were significantly faster in Group RD than in Group R. The duration of the sensory and motor block were significantly increased in Group RD.

DEX added to ropivacaine for brachial plexus block induced sedation that corresponds to a BIS value of 60 from which patients are easily awakened in a lucid state. In addition, perineural DEX shortened the onset time and prolonged the duration of the sensory and motor blocks.