The effect of adding dexmedetomidine to local anesthetic mixture for peribulbar block in vitreoretinal surgeries

Purpose
The purpose of this study was to compare the effect of adding different doses of dexmedetomidine to local anesthetic mixture for peribulbar block in vitreoretinal surgeries as regards duration, efficacy and pain relief.
Materials and methods
In this prospective randomized double blind clinical study, 160 patients were equally divided into four groups: () ( = 40) received 10 ml mixture of lidocaine 2% and bupivacaine 0.5% with 120 IU of hyaluronidase, 15 ( = 40) received a 10 ml mixture of lidocaine 2% and bupivacaine 0.5% with 120 IU of hyaluronidase + 15 μg dexmedetomidine, 20 ( = 40) received a 10 ml mixture of lidocaine 2% and bupivacaine 0.5% with 120 IU of hyaluronidase + 20 μg dexmedetomidine 25 ( = 40) also received a 10 ml mixture of lidocaine 2% and bupivacaine 0.5% with 120 IU of hyaluronidase + 25 μg dexmedetomidine.
Results
The onset of globe anesthesia was shorter in dexmedetomidine groups in comparison with control group. The difference was statistically significant in group D25 and group D20 in comparison with the control group ( > 0.05). Regarding the duration of globe analgesia, adding dexmedetomidine to the local anesthetic mixture prolonged the duration of globe analgesia, and this difference was statistically significant in group D25 in comparison with the control group ( > 0.05). Regarding the duration of globe akinesia although there was prolongation of the duration of akinesia in all groups the difference was statistically significant only in group D25 when compared to the control group ( > 0.05). The Verbal Rating Score (VRS) during surgery didn’t show any significant difference when comparing the dexmedetomidine groups (D15, D20 and D25) to the control group or when comparing the four groups to each other ( < 0.05).
Conclusions
Adding dexmedetomidine to a mixture of lidocaine 2% and bupivacaine in peribulbar block shortened sensory and motor block onset, extended the analgesia period and the motor block duration. It also significantly decreased the intraocular pressure and enabled better operating conditions. In this study, the addition of 25 μ dexmedetomidine to the local anesthetic mixture showed the best outcome.