Introduction The risk of bleeding during regional anesthesia implementation in patients on antithrombotic therapy remains poorly characterized. We; therefore, analyzed bloody tap rates and adjusted ORs comparing patients who take antithrombotic medications with those who do not.

Methods 65,814 qualifying regional anesthetics (2007–2019) from the Network for Safety in Regional Anesthesia and Acute Pain Therapy registry were included in a retrospective cohort analysis. Procedures in patients who took antithrombotic drugs were compared with procedures in patients who did not. The primary outcome was bloody puncture, defined as any kind of blood aspiration during placement. Secondarily, we considered timely discontinuation of thromboprophylaxis and the impact of various drug classes. As a sensitivity analysis, we used propensity matched groups.

Results Patients on antithrombotic therapy were more likely to have a bloody puncture during peripheral nerve block implementation (adjusted OR 1.60; 95% CI 1.33 to 1.93; p<0.001) irrespective of whether therapy was discontinued. In contrast, bloody neuraxial blocks were no more common in patients who took antithrombotic medications (adjusted OR 0.95; 95% CI 0.82 to 1.10; p=0.523) so long as they were paused per guideline. Across both peripheral and neuraxial blocks, concurrent use of more than one platelet and/or coagulation cascade inhibitor nearly doubled the odds (adjusted OR, 1.89; 95% CI 1.48 to 2.40; p<0.001).

Discussion Patients on antithrombotic therapy receiving peripheral blocks are at increased risk for bloody punctures irrespective of discontinuation practice. Patients having neuraxial blocks are not at increased risk so long as antithrombotics are stopped per guidelines. Patients who take combined medications are at especially high risk. Guidelines for discontinuing antithrombotic treatments for neuraxial anesthesia appear to be effective and should possibly be extended to high-risk peripheral blocks.