Sub-Tenon's Block in Patients with Previous Encircling Band Surgery-A Feasibility Study

Introduction: During the COVID-19 pandemic, reducing aerosol-generating procedures became fundamental, particularly in ophthalmic surgeries traditionally performed under general anesthesia (GA). Regional anesthesia, such as sub-Tenon's block (STB), is widely used in vitreoretinal surgeries, offering a safer alternative by avoiding airway manipulation. However, the altered orbital anatomy in patients with previous scleral explant surgery creates unique challenges to STB application. This study aims to evaluate the effectiveness, safety, and feasibility of STB in patients after encircling band surgery. Methods: This retrospective analysis included 46 patients with a history of scleral explant surgery, undergoing vitreoretinal procedures at the Bern University Hospital. All procedures were conducted under STB with either analgosedation or GA for additional support when required. An ophthalmic surgeon or an experienced anesthesiologist performed the STBs. Data collected included block success rate, procedural difficulty, incidence of chemosis, and patient satisfaction. The Institutional Ethics Committee approved this study, and all participants provided informed consent. Results: STB was successfully administered in 93.5% of cases, with only three unsuccessful blocks. Block placement was rated as easy in 55% of cases, moderately difficult in 28%, and difficult in 17%. Chemosis was observed in 24% of patients, with severe cases in only 4%. Patient satisfaction scores were high, with most patients expressing satisfaction with the STB procedure. Conversion to GA was required in only one case due to alcohol withdrawal-related agitation. Discussion: The high success rate and minimal complications suggest that STB is a feasible and safe alternative to GA in patients with prior scleral buckling surgery. The altered orbital anatomy presents potential challenges, including scar tissue and compartmentalization, which may lead to patchy anesthesia. However, the use of STB avoids the risks associated with GA and may be especially beneficial for elderly or frail patients. Future studies should further investigate the hemodynamic implications of STB in these cases and the potential for ultrasound-guided techniques to improve accuracy and safety.