Abstract
Bleeding complications after peripheral nerve blocks (PNBs) in patients treated with an antiplatelet agent and/or an anticoagulant drug are rare, with estimated incidence of 0.67% (0.51-0.83%). However, they can result in significant patient morbidity and may require follow-up investigations and interventions. The evidence for bleeding risks and complications after PNB is very low or nonexistent, therefore, recommendations and guidelines are based on retrospective analyses, case reports, expert opinions and expert panel consensus. In the manuscript, an expert panel consensus on classification of PNBs according to the potential risk of serious bleeding complications is presented. The risks of bleeding depend on the location (vicinity of the vessels and critical structures at risk from the mass effect of a hematoma), block depth (which influences needle visibility), associated comorbidities and anticoagulation status, body habitus, site compressibility, whether the bleeding or hematoma are easy or not to assess and how easy or not an intervention may be applied to prevent or treat bleeding. Also, technical factors are considered: type and size of the used needle, technical difficulties, multiple attempts, needle passes and bloody tap, use of catheters and type of nerve location technique (USG versus blind techniques) and operator experience. In all patients on antithrombotic drugs, benefits vs. risks should be weighted. A bleeding risk should be minimized with the optimization of patient's coagulation: appropriate antithrombotic drug timing before PNB, dose of antithrombotic drug, indication for the drug and risk factors that may influence drug pharmacokinetics (bodyweight, age, renal and hepatic function). Superficial PNBs may be performed in the presence of antithrombotic drug. For deep PNBs, a recommendations for neuraxial procedures should be considered.