Perineural administration of dexmedetomidine in combination with ropivacaine prolongs axillary brachial plexus block.

To evaluate the hypothesis that adding dexmedetomidine to ropivacaine prolongs axillary brachial plexus block. Forty-five patients of ASA I~II and aged 25-60 yr who were scheduled for elective forearm and hand surgery were randomly divided into 3 equal groups and received 40 ml of 0.33% ropivacaine + 1 ml dexmedetomidine (50 μg) (Group DR1), 40 ml of 0.33% ropivacaine + 1 ml dexmedetomidine (100 μg) (group DR2) or 40 ml of 0.33% ropivacaine + 1 ml saline (group R) in a double-blind fashion. The onset and duration of sensory and motor blocks and side effects were recorded. The demographic data and surgical characteristics were similar in each group. Sensory and motor block onset times were the same in the three groups. Sensory and motor blockade durations were longer in group DR2 than in group R (P < 0.05). There was no significant difference in the sensory blockade duration between group DR1 and group R. Bradycardia, hypertension and hypotension were not observed in group R and occurred more often in group DR2 than in group DR1. Dexmedetomidine added to ropivacaine for an axillary brachial plexus block prolongs the duration of the block. However, dexmedetomidine may also lead to side effects such as bradycardia, hypertension, and hypotension.