A dose-finding study of dexmedetomidine with levobupivacaine in ultrasound-guided axillary brachial plexus block

Background: Ultrasound-guided axillary brachial plexus block provides effective surgical anesthesia and postoperative analgesia for upper limb procedures. The addition of adjuvants to local anesthetics aims to prolong block duration and improve analgesic quality. This study evaluated the efficacy and safety of different doses of dexmedetomidine combined with levobupivacaine.Methods: Sixty-one patients undergoing elective forearm surgery were randomized into three groups receiving an ultrasound-guided axillary block with 25 mL of 0.5% levobupivacaine plus: Group LD1 (n=21), a fixed dose of 100 µg dexmedetomidine; Group LD2 (n=20), a weight-based dose of 1 µg/kg dexmedetomidine; and Group LD3 (n=20), a weight-based dose of 0.5 µg/kg dexmedetomidine. Primary outcomes included sensory and motor block duration and time to first analgesic request. Secondary outcomes comprised hemodynamic changes, sedation scores, and adverse effects.Results: Sensory and motor block durations were longest in Group LD1 (754.74 ± 46.11 min and 808.42 ± 58.71 min, respectively), though intergroup differences were not clinically significant. Analgesia was also prolonged in Group LD1 (819.47 ± 52.01 min). However, this group exhibited a higher incidence of bradycardia and deeper sedation (RSS ≥ 4). Mean arterial pressure was comparable across groups. All three regimens provided effective intraoperative analgesia, with comparable hemodynamic stability in terms of mean arterial pressure.Conclusion: While 100 µg dexmedetomidine as an adjuvant to levobupivacaine prolongs analgesia, it is associated with a greater risk of bradycardia and sedation. For clinical use in ultrasound-guided axillary brachial plexus block, the weight-based dose of 1 µg/kg dexmedetomidine offers an effective balance, providing enhanced analgesia with a more favourable side-effect profile.