Highly selective alpha-2 agonist as adjuvant for axillary plexus brachialis block in patients undergoing wrist surgery

Objectives: Regional anesthesia is gaining popularity due to optimal pain control, early
mobilization, and fewer complications. Axillary brachial plexus block provides safe,
effective, low-cost anesthesia with good postoperative analgesia. Various adjuvants, such as
clonidine, dexamethasone and adrenaline prolong the duration of regional anesthesia.
Dexmedetomidine, a highly selective α2 adrenergic agonist, prolongs the effect of regional
anesthesia when administered perineurally in combination with local anesthetics and it could
be evaluated as an adjuvant to regional anesthesia. We aim to evaluate the effect of perineural
dexmedetomidine on the duration of sensory and motor block and side effects during axillary
plexus brachialis block.
Materials and Methods: This prospective cohort study includes 84 patients undergoing
wrist surgery under axillary plexus brachialis block. All patients were aged 18 to 71 and had
an ASA score of 3 or less. Patients were divided in 2 groups - control group (CG; N=42) and
dexmedetomidine group (DG; N=42). Axillary plexus brachialis block was provided with
0.5% 20 mL bupivacaine and 1% 10 mL lidocaine. Patients in the DG group also received
100 mcg of dexmedetomidine perineurally in addition to local anesthetic. Axillary plexus
block was performed using ultrasound and neurostimulation for all patients. Onset of sensory
block was assessed using the pin prick method. Onset of motor block was assessed using
Bromage scale. Intraoperative oxygen saturation and hemodynamic parameters were
assessed. Depth of sedation was assessed using Ramsay Sedation Scale (RSS). Postoperative
pain intensity was assessed using Visual Analogue Scale (VAS).
Results: In the DG group, sensory block occurred within 10.1 minutes and motor block
within 13.1 minutes. In the CG group, sensory block occurred within 15.4 minutes and motor
block within 20.8 minutes (p <0.001). The duration of sensory block in the DG group was
12.74 h, duration of motor block was 13.67 h. In the CG group, sensory block lasted 7.35 h,
motor block lasted 8.06 h (p <0.001). In the DG group 30 patients (71.42%) had an RSS
score of 4 during surgery and only a single patient (2.38%) had an RSS score of 6. Two
patients had bradycardia and three patients had hypotension during surgery in the DG group.
Bradycardia and hypotension were not observed in CG group. No postoperative adverse
effects were observed in both groups.
Conclusions: Perineural administration of dexmedetomidine alongside local anesthetics for
wrist surgery increases the speed of onset and nearly doubles the duration of sensory and
motor block. Perineural dexmedetomidine allows a faster initiation of surgery and prolongs
postoperative analgesia. It also provides a sedative effect, limiting the need for additional
sedation during surgery. Postoperative adverse effects of dexmedetomidine administration
were not observed and intraoperative adverse effects were rare.