Supplementation of retrobulbar block with clonidine in vitreoretinal surgery: effect on postoperative pain ★

Study ObjectiveTo evaluate the effect of clonidine when added to local anesthetics on duration of postoperative analgesia during retrobulbar block.DesignProspective, randomized controlled trial.SettingOperating room and Postanesthesia Care Unit of a university-affiliated hospital.Subjects80 ASA physical status 1, 2, and 3 patients undergoing vitreoretinal surgery with or without scleral buckling.InterventionsPatients in the control group (n = 40) received a retrobulbar block with 4.5 mL of lidocaine-bupivacaine and 0.5 mL of saline. Clonidine group patients (n = 40) received 4.5 mL of lidocaine-bupivacaine and 0.5 μg/kg of clonidine in a 0.5 mL volume.MeasurementsThe time to first analgesic request, frequency of postoperative pain, and number of postoperative analgesic requests per patient were assessed.Main Results37 patients in the control group (92.5%) versus 24 patients (60%) in the clonidine group reported pain postoperatively (P = 0.001), with a shorter time to first analgesic request noted in the control group (4.9 ± 3 vs 11.9 ± 5.3 hrs; P < 0.001). The median number of postoperative analgesic requests per patient during the first 24 hours was higher in the control group than the clonidine group [2 (0-3) vs. 1 (0-3); P < 0.001].ConclusionsThe addition of clonidine 0.5 μg/kg to the local anesthetics of a retrobulbar block for vitreoretinal surgery decreases the frequency of postoperative pain and prolongs the time of analgesia.