Comparable pain scale, onset, and duration of anesthesia in sub-Thenon’s and peribulbar anesthesia in vitrectomy: A pilot study

Introduction: Specific guidelines regarding the safest and most effective anesthetic procedure for patients undergoing pars plana vitrectomy have not been established. Regional anesthetic use has increased in recent years. Regional anesthetic techniques can be needle-based (retrobulbar and peribulbar) and cannula-based (sub-Thenon’s block). This research aimed to compare the efficacy of sub-Thenon’s anesthesia and peribulbar block in vitrectomy surgery. Materials and Methods: This study was a prospective randomized controlled single-blind pilot. Thirty subjects were divided equally into sub-Thenon’s and peribulbar groups. Subjects were randomized by permuted block randomization with a single-blind method. Eye drops of 1% tropicamide and 5% phenylephrine were used to achieve pupil dilation. Local anesthetic used was 0.5% propacaine hydrochloride. Sub-Thenon anesthesia was achieved by 2.5 mL llidocaine 2% and 2.5 mL bupivacaine, whereas peribulbar block by 4 mL lidocaine 2% and 4 mL of bupivacaine 0.5% injection. The observed outcome variables included the numerical rating scale (NRS) at trocar insertion, anesthetic onset, and anesthesia duration. Results: The NRS during trocar insertion under sub-Thenon’s compared with peribulbar was comparable (P = 0.28). The onset of sub-Thenon’s versus peribulbar anesthesia is 6 versus 10 min (P = 0.74). Duration of anesthesia under sub-Thenon’s versus peribulbar anesthesia was 73.3 ± 30 versus 68 ± 26 min (P = 0.32). The results of multivariate analysis showed there were no differences in pain scale on trocar insertion, the onset of anesthesia, and duration of anesthesia between sub-Thenon’s and peribulbar anesthesia after controlling for confounding variables. Conclusion: There are no differences in trocar insertion pain scale, onset, and duration of anesthesia between sub-Thenon’s anesthesia and peribulbar anesthesia.