Clopidogrel (Plavix) and cardiac surgical patients: implications for platelet function monitoring and postoperative...

Area of Science:

• Cardiovascular Medicine
• Hematology
• Pharmacology

Background:

• Clopidogrel (Plavix) reduces ischemic events but optimal preoperative platelet function monitoring is lacking.
• Platelet aggregation inhibition is key to clopidogrel's efficacy.
• Assessing clopidogrel's antiplatelet effects preoperatively is crucial for patient safety.

Purpose of the Study:

• To compare testing modalities for assessing platelet adenosine diphosphate (ADP) receptor inhibition.
• To evaluate the clinical antiplatelet effects of clopidogrel and correlate them with postoperative bleeding.
• To determine reliable methods for monitoring clopidogrel's impact on platelet function.

Main Methods:

• In vitro study using 5'-p-fluorosulfonylbenzoyladenosine (FSBA) to model ADP inhibition and comparing thrombelastography (TEG), platelet aggregometry, and whole blood aggregation.
• Clinical assessment of clopidogrel's antiplatelet effects in 18 coronary bypass surgery patients.
• Correlation of preoperative TEG results with postoperative bleeding and platelet transfusion needs.

Main Results:

• FSBA inhibited platelet aggregation but not TEG maximum amplitude (MA).
• Preoperative TEG in clopidogrel-treated patients was normal or hypercoagulable, despite inhibited ADP-induced platelet aggregation.
• 84.6% of clopidogrel-treated patients undergoing cardiopulmonary bypass required platelet transfusion due to increased bleeding.

Conclusions:

• Normal preoperative TEG-MA does not rule out clopidogrel-induced ADP receptor blockade.
• TEG is a reliable monitor for CPB-induced platelet dysfunction related to GPIIb/IIIa.
• Specific platelet function tests (aggregometry or platelet count ratio) using ADP are necessary for monitoring clopidogrel's effects.