Dexmedetomidine versus clonidine as an adjuvant to peribulbar block in vitreoretinal surgery

Purpose To assess the efficacy, time to first analgesic request, total analgesic requirement,patients’ satisfaction, intraocular pressure (IOP), and side effects of addition of dexmedetomidine to a local anesthetic mixture for a peribulbar block in vitreoretinal surgery. Methods A double-blind prospective study was carried out on 50 ASA I and II patients scheduled for elective vitreoretinal surgery. Patients were divided randomly into two groups, 25 patients in each group. Group C received equal volumes of 9 ml of a 1 : 1 mixture of bupivacaine 0.5% and lidocaine 2% with 1 µg/kg clonidine in 1 ml saline and group D received the same local anesthetic mixture supplemented with 1 µg/kg dexmedetomidine in 1 ml saline (total volume 10 ml). The duration and onset of sensoryand motor block, time to first analgesic request, total analgesic requirement, patients’ comfort, IOP, and other side effects of dexmedetomidine were assessed. Results Patients who received dexmedetomidine showed significantly prolonged duration of lid, globe akinesia, and globe anesthesia (192.0 ± 34.9, 229.5 ±58.5, and 130.9 ± 30.5 min, respectively). The measurement of IOP was significantly less in the dexmedetomidine group after 5 and 10 min. The time to first analgesic requirement was statistically higher in the dexmedetomidine group (6.2 ±2.3 h), whereas the totalanalgesic requirement was significantly higher in the clonidine group. More than 90% of dexmedetomidine patients were comfortable intraoperatively and postoperatively, with significantly less side effects of dryness of the mouth and dizziness. Conclusion The addition of 1 µg/kg dexmedetomidne to the lidocaine–bupivacaine mixture in a peribulbar block for vitreoretinal surgery improves the duration of lid, globe akinesia, and anesthesia, with a significant decrease in the IOP. It prolongs the time to first rescue analgesia and decreases the number of analgesic requirements, with minimal side effects in comparison with clonidine.