Effects of adding dexmedetomidine to lidocaine on the onset and duration of axillary block for upper extremity surgeries

Introduction: Dexmedetomidine, which is an alpha 2 agonist, reduces the transmission of pain signals and has an independent inhibitory effect on nerve action potential. The purpose of this study was to examine the effects of adding dexmedetomidine to lidocaine in an axillary block.

Methods: In this randomized, double-blind study 40 patients included patients were divided randomly into two groups of 20: In the first group, 39 cc of 1% lidocaine plus 1cc of normal saline was administered and the 2^nd group received dexmedetomidine 1cc (100µg) in addition to 39 cc of 1% lidocaine. The onset and persistence of the sensorimotor block and hemodynamic changes including heart rate and systolic and diastolic blood pressure before, during, and after surgery were compared.

Results: Age, sex, type of surgery, duration of surgery, and other demographic characteristics were not significantly different in two groups (P>0.05). Onset of the sensory and motor block was similar in both groups, but the persistence of the sensory and motor block and analgesia in the treatment group was significantly higher (P<0.05). The VAS score was lower in cases than controls. Hemodynamic change differences between the two groups were statistically significant (P<0.05).

Conclusion: The results of this study showed that adding dexmedetomidine to lidocaine in an axillary block did not alter the onset of the sensory and motor block, but the sensory and motor block duration and analgesia was increased. Despite significant differences in hemodynamic responses between the two groups, these changes were not clinically significant in ASA1 patients.