Background
Aspirin, clopidogrel, prasugrel and ticagrelor are oral antiplatelet agents that are used widely for the prevention of thrombotic events in patients with cardiovascular disease. Despite their effectiveness in reducing thrombotic events, oral antiplatelets are associated with an increased risk of bleeding which includes major bleeding and fatal bleeding. Investigation of bleeding in patients who take antiplatelets has been performed using light transmission aggregometry and point of care platelet function assays. Management of patients who take oral antiplatelets and who bleed or require urgent surgery is challenging for clinicians. No antidote is available to reverse oral antiplatelet agents, and their platelet inhibiting effect persists for 3 to 10 days after the last dose. Platelet transfusion can reverse the haemostatic defect produced by antiplatelet drugs by providing a source of uninhibited platelets from a donor.
Aims
To determine 1) the optimal time at which to transfuse platelets to reverse oral antiplatelet agents, and 2) the optimal quantity of transfused platelets required to reverse oral antiplatelet agents.
Methods
In vitro reversal experiments, cohort studies and randomised trials of platelet transfusion for the reversal of oral antiplatelets were reviewed.
Results
Laboratory studies show that platelets are most effective at reversing oral antiplatelets if transfused after the agent is cleared from the circulation. There are three distinct patterns of reversal of oral antiplatelet agents. Aspirin can be fully reversed from about one hour after ingestion with 1-2 apheresis units of platelets. Clopidogrel and prasugrel can be partially reversed as donor platelets provide a linear improvement in aggregation. Ticagrelor is the most difficult to reverse, and the response to donor platelets is dose- and time-dependent.
Conclusion
Detailed knowledge of the optimal timing and quantity of platelets to transfuse is essential to prevent or treat bleeding in patients who take oral antiplatelets, and to utilise finite blood products appropriately. Laboratory studies provide information on management of bleeding on oral antiplatelet agents which will be helpful to design clinical studies of platelet transfusion.