title: Assessment of platelet inhibition secondary to clopidogrel and aspirin therapy in preoperative acute surgical patients measured by Thrombelastography Platelet Mapping.
abstract: 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.
authors.affiliation: Academic Unit of Anaesthesia, Royal Perth Hospital, Perth, Australia. tomcollyer@doctors.org.uk
authors.forename: T C
authors.initials: TC
authors.lastname: Collyer
authors.forename: D J
authors.initials: DJ
authors.lastname: Gray
authors.forename: R
authors.initials: R
authors.lastname: Sandhu
authors.forename: J
authors.initials: J
authors.lastname: Berridge
authors.forename: G
authors.initials: G
authors.lastname: Lyons
mesh_terms: 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
chemical_list: D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin