[Effect of dexmedetomidine on supraclavicular brachial plexus block: a randomized double blind prospective study]

To evaluate the effect of dexmedetomidine combined with ropivacaine on brachial plexus block in patients scheduled for elective shoulder arthroscopy.

Ninety patients with American Society of Anesthesiologists (ASA) I or II, scheduled for elective shoulder arthroscopy, were randomly divided into three groups. In group R (n=30), the patients were given 10 mL of 0.375% ropivacaine in branchial plexus block (interscalene approach guided by ultrasound), in group D1 (n=30), the patients were given 10 mL of 0.375% ropivacaine (interscalene approach guided by ultrasound) + dexmedetomidine 0.2 μg/(kg×h) (intravenous pump infusion), and in group D2 (n=30), the patients were given 10 mL of 0.375% ropivacaine (interscalene approach guided by ultrasound) + dexedetomidine 0.7 μg/(kg×h) (intravenous pump infusion). To evaluate the effect of brachial plexus block before general anesthesia. Group D1 and group D2 were given dexmedetomidine intravenously for 1.0 μg/kg during 10 min, then the drug was pumped by 0.2 μg/(kg×h) and 0.7 μg/(kg×h) respectively until 30 min before the operation finished. Changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and before anesthesia (T0), 10 min (T1), 30 min (T2) after giving dexmedetomidine, discontinue medication (T3), after operation (T4), and extubation (T5) were investigated. Motor and sensory block onset times, block durations, and duration of analgesia were recorded. The scores of pain after operation and the adverse effects of shiver, hypopiesia, drowsiness, and blood loss were recorded during operation.

Compared with group R, the duration of analgesia and duration of sensory block in group D1 and group D2 were significant longer (P<0.01), there was no significant difference between groups D1 and D2 (P>0.05). Compared with group R, at each time point of T1-T5, the heart rate and systolic blood pressure in group D1 and group D2 were significantly decreased (P<0.01). Compared with D1 group, the incidence of hypotension and bradycardia in group D2 were significantly different (P<0.05).

Intravenous dexmedetomidine could prolong the duration of analgesia time and sensory block within the brachial plexus block, inhibiting the stress response during arthroscopic shoulder surgery. Compared with high-dose, low-dose can provide safer and better clinical effect and reduce the adverse effects of dexmedetomidine.