title: The use of the activated clotting time for monitoring heparin therapy in critically ill patients.
abstract: OBJECTIVE
  To determine the correlation between activated clotting time (ACT) and activated partial thromboplastin time (aPTT) in patients receiving intravenous unfractionated heparin therapy, and the accuracy of the ACT in predicting the level of anticoagulation.
  
  
  METHODS
  Paired aPTT and ACT measurements were obtained from a convenience sample of critically ill patients requiring intravenous unfractionated heparin. The aPTT was determined in the hospital laboratory and ACT measurements were performed with a portable device.
  
  
  METHODS
  The intensive care unit of Ghent University Hospital, a tertiary care facility with 54 beds.
  
  
  METHODS
  Twenty-eight patients were studied prospectively; a total of 105 paired samples were obtained. The indication for heparin therapy was cerebral ischemia in 8, various cardiac conditions in 10, pulmonary embolism in 3, continuous hemofiltration in 3, and peripheral arterial thrombosis in 4.
  
  
  RESULTS
  There was a significant correlation between aPTT and ACT. Analysis of variance showed a significant difference in ACT between different levels of anticoagulation, aPTT shorter than 60 s (group 1), aPTT 60-90 s (group 2), and aPTT longer than 90 s (group 3): 142+/-16.7 s in group 1 vs. 155+/-29.6 and 192+/-39.1 in groups 2 and 3.
  
  
  CONCLUSIONS
  The correlation between the aPTT and the ACT in this ICU setting is poor; ACT cannot differentiate between low and therapeutic levels of anticoagulation. The use of the ACT for monitoring low to moderate doses of heparin in ICU patients cannot be recommended.
authors.affiliation: Intensive Care Unit, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium. jan.dewaele@rug.ac.be
authors.forename: Jan J
authors.initials: JJ
authors.lastname: De Waele
authors.forename: Sebastiaan
authors.initials: S
authors.lastname: Van Cauwenberghe
authors.forename: Eric
authors.initials: E
authors.lastname: Hoste
authors.forename: Dominique
authors.initials: D
authors.lastname: Benoit
authors.forename: Francis
authors.initials: F
authors.lastname: Colardyn
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D000925:Anticoagulants / Q000009:adverse effects*; D001530:Belgium; D002545:Brain Ischemia / Q000188:drug therapy; D003422:Critical Care / Q000379:methods* / Q000592:standards; D016638:Critical Illness / Q000628:therapy*; D016903:Drug Monitoring / Q000379:methods* / Q000592:standards; D005260:Female; D006493:Heparin / Q000008:administration & dosage*; D006785:Hospitals, University; D006801:Humans; D008297:Male; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D019095:Point-of-Care Systems / Q000592:standards; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000188:drug therapy; D013927:Thrombosis / Q000188:drug therapy; D014914:Whole Blood Coagulation Time
chemical_list: D000925:Anticoagulants; D006493:Heparin