Dexmedetomidine as an adjuvant to 0.5% ropivacaine in ultrasound-guided axillary brachial plexus block.

Abstract

The aim of this study was to elucidate the effect of dexmedetomidine added to ropivacaine on the onset and duration of sensory and motor block and duration of analgesia of ultrasound-guided axillary brachial plexus block. Thirty-seven ASA physical status I-II patients with elective forearm and hand surgery under ultrasound-guided axillary brachial plexus block were randomly divided into 2 groups. Patients in ropivacaine-dexmedetomidine group (group RD, n=19) received 15mL of 0.5% ropivacaine with 100μg (1mL) dexmedetomidine, and patients in ropivacaine group (group R, n=18) received 15mL of 0.5% ropivacaine with 1mL of normal saline. Onset time and duration of sensory and motor block and duration of analgesia were assessed. Duration of sensory block (U-value=35, P<.001), duration of motor block (P=.001) and duration of analgesia (P<.001) were extended in group RD compared to group R. Onset time of sensory block in group RD was significantly faster than in group R (U-value=65.5, P=.001). Onset time of motor block showed no significant difference between the 2 groups (U-value=116.5, P=.096). Adverse reactions were reported only in group RD (bradycardia in 2 and hypotension in 3 patients). Our study indicated that dexmedetomidine 100μg as adjuvant on ultrasound-guided axillary plexus block significantly prolonged the duration of sensory block and analgesia, as well as accelerated the time to onset of sensory block. These results should be weighed against the increased risks of motor block prolongation, transient bradycardia and hypotension and allow for attentive optimism, only if prolonged clinical trials provide a definitive answer.