title: Is the kaolin or celite activated clotting time affected by tranexamic acid?
abstract: BACKGROUND
  During cardiopulmonary bypass, the activated clotting time is frequently used for determination of anticoagulation, and either Celite or kaolin are used as activators. If aprotinin is administered concomitantly, the Celite activated clotting time (C-ACT) becomes significantly higher than the kaolin activated clotting time (K-ACT). Therefore, insufficient anticoagulation using C-ACT in the presence of aprotinin is a major concern. Whether the application of tranexamic acid (TA), a pharmacologic alternative to aprotinin, has similar effects has not been studied before.
  
  
  METHODS
  An in vitro study using the blood of healthy volunteers was performed. Both C-ACT and K-ACT were measured at baseline, after adding TA, and after adding TA and heparin. In addition, 30 patients undergoing primary cardiac operations had simultaneous measurements of C-ACT and K-ACT after skin-incision, 5 minutes after the application of heparin and TA, every 30 minutes during cardiopulmonary bypass, and 10 minutes after the application of protamine.
  
  
  RESULTS
  In vitro, C-ACT and K-ACT correlated significantly at each measurement. Tranexamic acid had no influence on the activated clotting time. In vivo, C-ACT and K-ACT did not differ significantly, but at each time C-ACT tended to be greater than K-ACT (p = 0.086). The average difference between K-ACT and C-ACT was stable before and after the application of TA (p = 0.85) but the variability of the differences significantly increased during cardiopulmonary bypass (p < 0.001).
  
  
  CONCLUSIONS
  Application of TA does not seem to differentially affect the mean C-ACT and K-ACT. No recommendation seems warranted to prefer one activator over the other in patients receiving TA.
authors.affiliation: Department of Cardiac Surgery, University Hospital of Luebeck, Germany.
authors.forename: J F Matthias
authors.initials: JF
authors.lastname: Bechtel
authors.forename: Joachim
authors.initials: J
authors.lastname: Prosch
authors.forename: Hans-Hinrich
authors.initials: HH
authors.lastname: Sievers
authors.forename: Claus
authors.initials: C
authors.lastname: Bartels
mesh_terms: D000368:Aged; D000933:Antifibrinolytic Agents / Q000494:pharmacology*; D007692:Diatomaceous Earth; D005260:Female; D006801:Humans; D008297:Male; D010314:Partial Thromboplastin Time; D014148:Tranexamic Acid / Q000494:pharmacology*
chemical_list: D000933:Antifibrinolytic Agents; D007692:Diatomaceous Earth; D014148:Tranexamic Acid