title: Platelet-activated clotting time does not measure platelet reactivity during cardiac surgery.
abstract: BACKGROUND
  Platelet dysfunction is a major contributor to bleeding after cardiopulmonary bypass (CPB), yet it remains difficult to diagnose. A point-of-care monitor, the platelet-activated clotting time (PACT), measures accelerated shortening of the kaolin-activated clotting time by addition of platelet activating factor. The authors sought to evaluate the clinical utility of the PACT by conducting serial measurements of PACT during cardiac surgery and correlating postoperative measurements with blood loss.
  
  
  METHODS
  In 50 cardiac surgical patients, blood was sampled at 10 time points to measure PACT. Simultaneously, platelet reactivity was measured by the thrombin receptor agonist peptide-induced expression of P-selectin, using flow cytometry. These tests were temporally analyzed. PACT values, P-selectin expression, and other coagulation tests were analyzed for correlation with postoperative chest tube drainage.
  
  
  RESULTS
  PACT and P-selectin expression were maximally reduced after protamine administration. Changes in PACT did not correlate with changes in P-selectin expression at any time interval. Total 8-h chest tube drainage did not correlate with any coagulation test at any time point except with P-selectin expression after protamine administration (r = -0.4; P = 0.03).
  
  
  CONCLUSIONS
  The platelet dysfunction associated with CPB may be a result of depressed platelet reactivity, as shown by thrombin receptor activating peptide-induced P-selectin expression. Changes in PACT did not correlate with blood loss or with changes in P-selectin expression suggesting that PACT is not a specific measure of platelet reactivity.
authors.affiliation: Department of Cardiothoracic Anesthesiology, The Mount Sinai Medical Center, New York, New York, USA. linda_shore@SMTPLINK.mssm.edu
authors.forename: L
authors.initials: L
authors.lastname: Shore-Lesserson
authors.forename: T
authors.initials: T
authors.lastname: Ammar
authors.forename: M
authors.initials: M
authors.lastname: DePerio
authors.forename: F
authors.initials: F
authors.lastname: Vela-Cantos
authors.forename: C
authors.initials: C
authors.lastname: Fisher
authors.forename: K
authors.initials: K
authors.lastname: Sarier
mesh_terms: D000328:Adult; D000368:Aged; D001792:Blood Platelets / Q000502:physiology*; D001803:Blood Transfusion; D006348:Cardiac Surgical Procedures; D002315:Cardiopulmonary Bypass; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019007:P-Selectin / Q000032:analysis; D014914:Whole Blood Coagulation Time
chemical_list: D019007:P-Selectin