title: An evaluation of factors affecting activated coagulation time.
abstract: OBJECTIVE
  Although failure to achieve an adequate activated coagulation time (ACT) after full heparinization before cardiopulmonary bypass often is attributed to antithrombin (AT) deficiency, it remains unclear if this is a causative mechanism of decreased heparin responsiveness. Therefore, the authors determined the relationship between AT and other coagulation-related factors that affect the ACT measurement and heparin sensitivity index before the establishment of cardiopulmonary bypass.
  
  
  METHODS
  Observational study.
  
  
  METHODS
  University medical center.
  
  
  METHODS
  Adult elective cardiac surgical patients.
  
  
  METHODS
  Preoperative data collection included demographics, type of preoperative medical therapy, hemoglobin, platelet count, and AT. Intraoperative measurements included ACT and anti-Xa activity.
  
  
  RESULTS
  Of the 203 patients enrolled in this study, 10% (n = 21) did not achieve an adequate ACT (≥400 seconds) after full heparinization. Subnormal AT activity (55%-79%) was not related to a low ACT and a low heparin sensitivity index. Preoperative low-molecular-weight heparin therapy did not cause a decreased ACT response. However, preoperative low hemoglobin levels and high platelet counts were associated with a decreased ACT.
  
  
  CONCLUSIONS
  All these observations suggest that failure to achieve an adequate ACT is, in general, not an indicator of AT deficiency but could be affected by high platelet counts and low hemoglobin levels.
authors.affiliation: Department of Cardiothoracic Surgery, Cardiovascular Research Institute Maastricht (CARIM), Maastricht, the Netherlands. yvonne.bosch@mumc.nl
authors.forename: Yvonne P J
authors.initials: YP
authors.lastname: Bosch
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Weerwind
authors.forename: Patty J
authors.initials: PJ
authors.lastname: Nelemans
authors.forename: Jos G
authors.initials: JG
authors.lastname: Maessen
authors.forename: Baheramsjah
authors.initials: B
authors.lastname: Mochtar
mesh_terms: D000368:Aged; D020152:Antithrombin III Deficiency / Q000175:diagnosis; D001241:Aspirin / Q000494:pharmacology; D005260:Female; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008074:Lipoproteins / Q000502:physiology; D008297:Male; D008875:Middle Aged; D010976:Platelet Count; D014914:Whole Blood Coagulation Time
chemical_list: D006454:Hemoglobins; D008074:Lipoproteins; C051928:lipoprotein-associated coagulation inhibitor; D001241:Aspirin