Introduction: Clonidine has established itself as an effective adjuvant in peripheral nerve blocks. However, its effects on systemic administration along with nerve blocks, elucidating the site and mechanism of its action has not been studied adequately. The present trial was conducted to compare intravenous and perineurally administered clonidine in brachial plexus blocks.

Materials and Methods: ASA I and II patients undergoing upper limb orthopedic surgeries under brachial plexus block with Bupivacaine were randomized into three groups by computer generated random numbers with allocation concealment. In the first group (Bc) 2 mcg/kg of clonidine was added to the anesthesia solution; second group (Bivc) recieved clonidine 2 mcg/kg by intravenous route and third group (B) received no clonidine, with normal saline used as placebo to blind the anesthesiologist. Onset and duration of sensorimotor block, hemodynamic variables, duration of analgesia, level of sedation and adverse effects were noted down by blinded assessors.

Results: Ninety three patients were randomized into three groups of 31 each. Mean onset of sensorimotor block was earlier in Group Bc compared to Group B: 7 min v/s 11.5 min (p<0.005) for sensory and 16.4 min v/s 22.8 min (p<0.005) for motor. Mean duration of analgesia was longer in Group Bc(1160.7 min) compared to group B ( 442.5 min) (p<0.005) and group Bivc( 454.6 min) (p<0.005). Incidence of sedation was higher in Group Bivc

Conclusion: Perineurally administered clonidine hastened onset of block and prolonged postoperative analgesia compared to placebo control and intravenously administered clonidine in brachial plexus block with Bupivacaine.