Pharmacodynamic evaluation of dexmedetomidine as an additive drug to bupivacaine in ultrasound-guided interscalene brachial plexus block

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Introduction Dexmedetomidine, a novel α2 agonist, is widely used as an adjuvant to local anesthetic in peripheral nerve blocks to decrease the time of onset and increase the duration of the block. Aim We have conducted this study to compare three different doses of dexmedetomidine as an additive to 0.5% bupivacaine in interscalene brachial plexus block guided by ultrasound for upper limb surgery. Patient and Methods Sixty patients aged (21–60 years, ASA I, II) were divided into three groups. Group I received 15 ml 0.5% bupivacaine+50 µg dexmedetomidine (BD50). Group II received 15 ml 0.5% bupivacaine+100 µg dexmedetomidine (BD100). Group III received 15 ml 0.5% bupivacaine+150 µg dexmedetomidine (BD150). Onset of sensory and motor block, visual analog scale, total analgesic need, sedation level, side effects and complications, hemodynamic variables (systolic and diastolic blood pressure and heart rate), and stress response [cortisol, blood glucose, C-reactive protein (ultrasensitive)] were recorded for each patient. Results The onset time for sensory and motor blocks in intergroups comparisons showed nonsignificant difference between groups II and III. The results showed a highly significant difference in visual analog scale score after 12 and 24 h postoperatively in group I than in groups II and III (P<0.001). Six patients in group I required rescue analgesia whereas in groups II and III no patients required rescue analgesia in the first 24 h postoperatively. The sedation score was higher in groups II and III than in group I. No serious side effects were observed in all groups except bradycardia in one (5%) patient in group II and two (10%) patients in group III and it was clinically insignificant. Conclusion By comparing the outcomes of using different doses of dexmedetomidine, we may conclude that the use of 100 µg dexmedetomidine carries the best benefits of dexmedetomidine with little hazards and side effects.