title: Clopidogrel (Plavix) and cardiac surgical patients: implications for platelet function monitoring and postoperative bleeding.
abstract: The use of clopidogrel (Plavix), an inhibitor of adenosine diphosphate (ADP)-induced platelet aggregation, has been proven to reduce ischemic events in cardiovascular patients, but little information is available for optimal monitoring of platelet function in patients receiving the drug preoperatively. In the first part of the study we compared different testing modalities (thrombelastography (TEG), platelet aggregometry, and whole blood aggregation) to assess platelet ADP receptor inhibition. Because clopidogrel is a pro-drug, we used an in vitro model of ADP inhibition with 5'-p-fluorosulfonylbenzoyladenosine (FSBA). FSBA at final concentration of 80 microM completely inhibited platelet aggregation but had no effect on TEG maximum amplitude (MA). In the second part of the study, antiplatelet effects of clopidogrel were clinically assessed and correlated to postoperative bleeding in 18 coronary bypass surgery patients. Preoperative TEG results were normal or hypercoagulable in clopidogrel-treated patients, although platelet aggregation responses to ADP were inhibited. Clopidogrel-treated patients who underwent cardiopulmonary bypass had a high incidence (84.6%) of platelet transfusion therapy due to increased chest tube drainage. In conclusion, we have demonstrated that normal preoperative TEG-MA does not preclude clopidogrel-induced ADP receptor blockade; however, TEG can be a reliable monitor for CPB-induced platelet dysfunction related to GPIIb/IIIa. For monitoring clopidogrel, it is necessary to perform more specific platelet function tests (aggregometry or platelet count ratio) using ADP as an activator.
authors.affiliation: Department of Anesthesiology, Emory University School of Medicine, Atlanta, GA 30322, USA. kenichi_tanaka@emoryhealthcare.org
authors.forename: Kenichi A
authors.initials: KA
authors.lastname: Tanaka
authors.forename: Fania
authors.initials: F
authors.lastname: Szlam
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Kelly
authors.forename: J David
authors.initials: JD
authors.lastname: Vega
authors.forename: Jerrold H
authors.initials: JH
authors.lastname: Levy
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000368:Aged; D000369:Aged, 80 and over; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D002318:Cardiovascular Diseases / Q000097:blood* / Q000188:drug therapy / Q000601:surgery; D000077144:Clopidogrel; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology*; D010979:Platelet Function Tests / Q000379:methods*; D019106:Postoperative Hemorrhage / Q000517:prevention & control*; D058919:Purinergic P2 Receptor Antagonists; D012189:Retrospective Studies; D013916:Thrombelastography / Q000187:drug effects; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D058919:Purinergic P2 Receptor Antagonists; D000244:Adenosine Diphosphate; C010959:5'-(4-fluorosulfonylbenzoyl)adenosine; D000077144:Clopidogrel; D000241:Adenosine; D013988:Ticlopidine