Assessment of platelet inhibition secondary to clopidogrel and aspirin therapy in preoperative acute surgical patients measured by Thrombelastography Platelet Mapping.
BACKGROUND
Increasing numbers of patients prescribed clopidogrel and aspirin are presenting for non-elective surgery. No consensus on the timing of surgery exists after withdrawal of antiplatelet and tests of platelet function are not routinely available. The Thrombelastography Platelet Mapping (TEG-PM) assay is designed to assess platelet inhibition secondary to antiplatelet therapy. We assessed its ability to detect platelet inhibition in preoperative acute surgical patients.


METHODS
We conducted a prospective observational study in three groups of preoperative patients: those taking clopidogrel or aspirin up to admission, and a control group. TEG-PM was performed on the day of admission and alternate days until surgery.


RESULTS
Mean (SD) platelet thromboxane A(2) receptor inhibition in the control group was 17.5% (23.8) (n=20), 52.6% (32.3) (n=18) in the aspirin group, and 31.9% (27.6) (n=21) in the clopidogrel group (P<0.01). Mean (SD) platelet adenosine diphosphate (ADP) receptor inhibition in the control group was 47.8% (18.9) (n=20), 52.6% (19.7) (n=18) in the aspirin group, and 71.5% (18.4) (n=21) in the clopidogrel group (P<0.01). Among the clopidogrel group awaiting surgery, mean platelet ADP channel inhibition decreased on day 3 to 67.1% (24.7) (n=11), 48.8% (24.4) (n=4) on day 5, and 36.1% (15.9) (n=2) on day 7 (P=0.57).


CONCLUSIONS
TEG-PM can identify statistically significant platelet inhibition after antiplatelet therapy; however, the overlap in platelet receptor inhibition between the three groups is likely to limit the clinical usefulness of this test.
Collyer
T C
TC
Academic Unit of Anaesthesia, Royal Perth Hospital, Perth, Australia. tomcollyer@doctors.org.uk
Gray
D J
DJ
Sandhu
R
R
Berridge
J
J
Lyons
G
G
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001241:Aspirin / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects*; D000077144:Clopidogrel; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011300:Preoperative Care / Q000379:methods; D011446:Prospective Studies; D013916:Thrombelastography / Q000379:methods*; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000494:pharmacology
D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin