A COMPARATIVE STUDY OF TWO DIFFERENT DOSES OF DEXMEDETOMIDINE AS AN ADJUVANT TO LOCAL ANESTHETIC IN PERIBULBAR BLOCK FOR CATARACT SURGERY

Abstract

Background: Peribulbar block is widely used for cataract surgery; however, its relatively slow onset and limited duration of postoperative analgesia remain important limitations. Dexmedetomidine has emerged as a promising adjuvant to local anesthetics, although the optimal perineural dose remains uncertain. Aim: To compare the efficacy and safety of 25 μg versus 50 μg dexmedetomidine as an adjuvant to local anesthetics in peribulbar block for cataract surgery. Materials and Methods: This prospective, randomized, double-blind comparative study included 100 patients (ASA I–III) undergoing elective phacoemulsification cataract surgery. Patients were allocated into two equal groups. Group D25 received 25 μg dexmedetomidine, whereas Group D50 received 50 μg dexmedetomidine combined with lidocaine, bupivacaine, and hyaluronidase for peribulbar block. The primary outcome was onset of globe akinesia. Secondary outcomes included onset and duration of sensory and motor block, duration of postoperative analgesia, supplemental block requirement, Ramsay Sedation Score, intraoperative Visual Analog Scale (VAS) pain score, surgeon and patient satisfaction, hemodynamic parameters, and adverse events. Results: Baseline characteristics were comparable between groups. Group D50 demonstrated significantly faster onset of globe akinesia (5.8±1.2 vs. 7.2±1.4 min; p<0.001) and sensory block (3.1±0.8 vs. 3.8±0.9 min; p<0.001), along with longer sensory block (336.8±38.6 vs. 282.6±32.8 min), motor block (296.9±35.2 vs. 241.7±28.4 min), and postoperative analgesia (389.6±46.3 vs. 322.8±39.4 min) (all p<0.001). It also required fewer supplemental blocks (2% vs. 12%; p=0.049), produced lower intraoperative pain scores, higher sedation, and superior surgeon and patient satisfaction (all p<0.001). Hemodynamic parameters remained stable in both groups, with only a modest reduction in heart rate in Group D50. Adverse events were infrequent and comparable between groups. Conclusion: Perineural dexmedetomidine 50 μg provides superior block quality, faster onset, prolonged postoperative analgesia, reduced supplemental anesthetic requirement, and greater patient and surgeon satisfaction compared with 25 μg, while maintaining acceptable hemodynamic stability and a favorable safety profile.