Therapeutic Antithrombotic Agent Use and Bleeding Risk in Retrobulbar Anesthesia for Outpatient Ophthalmic Surgery.

Background and objective Retrobulbar block is commonly used for providing effective anesthesia and akinesia for ophthalmic surgery. It can, however, lead to sight-threatening retrobulbar hemorrhage in very rare cases. The aim of this study was to evaluate retrobulbar block quality, to determine the prevalence of retrobulbar hemorrhage associated with these blocks, and to assess whether the use of antithrombotic agents in patients undergoing retrobulbar block for ophthalmic surgery was associated with retrobulbar hemorrhage. Methods This was a retrospective cohort study conducted on a registry of patients who underwent outpatient ophthalmic surgery at a tertiary care eye center. Adult patients who underwent ophthalmic surgery and received retrobulbar block between October 2014 and December 2021 were retrospectively included to evaluate retrobulbar hemorrhage prevalence and block quality between three groups according to antithrombotic agent use: non-therapeutic antithrombotic use, therapeutic antithrombotic use, and no antithrombotic use. Results Of 15,112 records included in final analyses, the median age was 73 with an interquartile range of 67-79 years. White patients totaled 9,813 (64.9%). Patients classified as having mild or major systemic disease before surgery totaled 8,178 (62.9%) and 4,216 (32.4%), respectively. Patients who had at least one comorbidity totaled 13,364 (88.4%). Regarding antithrombotic agent use, 5,856 (38.8%) patients used either one, two, or three medications. Of these, there were 4,183 (27.7%) patients who were therapeutic during the block procedure compared to a total of 10,929 (72.3%) who either did not use antithrombotics or did not use them therapeutically. There were seven (0.1%) retrobulbar hemorrhages among 15,112 patients overall, including two (0.1%) from the 4,183 (27.7%) therapeutic antithrombotic users and five (0.1%) from the 9,256 (61.2%) no antithrombotic users, with no significant differences between groups (p=0.621). Successful blocks totaled 13,364 (95.7%). Conclusions Retrobulbar hemorrhage from retrobulbar block in ophthalmic surgery patients is extremely rare, with these results showing no difference in the occurrence of retrobulbar hemorrhage between those using and not using antithrombotic medications. Therefore, it is recommended to continue antithrombotic medication use during ophthalmic procedures as they do not appear to increase the risk of retrobulbar hemorrhage.