Dexmedetomidine versus magnesium sulphate as an adjuvant to local anesthesia in single-injection percutaneous peribulbar anesthesia for cataract extraction

Abstract

BackgroundThe aim of the study was to evaluate the impact of addition of dexmedetomidine or magnesium sulphate to the standard local anesthetics mixture as a primary objective and to compare between both as a secondary objective utilizing the single-injection percutaneous technique for peribulbar block. In this prospective randomized double-blinded clinical trial (RCT), sixty patients, both sexes, aged 45 to 75, with an ASA of I to III, were scheduled for cataract extraction operation. They were divided into three equal groups; each received a single injection peribulbar block of a mixture of 0.5% bupivacaine (3 ml) + 2 percent lidocaine (3 ml) + 120 IU hyaluronidase + (control group (C): 0.5 ml of normal saline; group D: 50 μg of dexmedetomidine; group M: 50 mg of magnesium sulphate in 0.5 ml) with a total injected volume of 7 ml each. The duration of sensory, motor block, need for supplementary doses, hemodynamics, and satisfaction of patients and surgeons were assessed.ResultsFor the primary outcome, both the dexmedetomidine and magnesium groups revealed statistically significant differences from the control group with shorter onsets of sensory block and lid akinesia (p value< 0.001 for both), shorter onset of globe akinesia for dexmedetomidine (p value<0.001) and for magnesium sulphate (p value=0.022), prolonged duration of lid and globe akinesia and sensory block (p value<0.001), better patient satisfaction (p value=0.044) but insignificant difference regarding surgeons’ satisfaction (p value= 0.117) and a less frequent, but statistically insignificant need for supplementary injection (p value=0.075). The demographic and clinical hemodynamics and oxygen saturation parameters were comparable between the three groups. For the secondary outcome, dexmedetomidine was superior to magnesium sulphate regarding onset of globe and lid akinesia (p value= 0.047 and 0.003, respectively), and durations of globe akinesia and sensory block (p value= 0.02 and 0.016, respectively). No complications related to the drugs or procedure were recorded.ConclusionsWhen compared to 50 mg magnesium sulphate, dexmedetomidine at a dose of 50 μg is a superior adjunct to local anesthetic combination in peribulbar block for cataract procedures in terms of start and duration of peribulbar block.