Implementing a New Method for Activated Clotting Time
Point-of-care determination of the activated clotting time (ACT) has become the standard of care in a number of clinical situations. The authors converted from ACT done by the Hemochron 801 analyzer, which uses tubes containing either celite, kaolin, or glass as a clotting activator, to the Actalyke analyzer with MaxACT tubes, which contain a mixture of all these clotting activators. Because the systems used different clot activators and clot detection methods, the authors conducted a systematic evaluation to establish new therapeutic ranges for specific patient groups. More than 300 samples from patients who routinely require ACT testing were obtained. This included 50 blood samples from adult open-heart surgery cases, 19 from pediatric open-heart surgery cases, 130 from adult cardiac percutaneous coronary intervention (catheterization) procedures, 53 from cardiac catheterization for radiofrequency ablation procedures, and 57 from pediatric patients on extracorporeal membrane oxygenation. With respect to precision, for ACT results up to 400 seconds, the mean difference between duplicate results was approximately 20% less for the Actalyke system than for the Hemochron 801 system. ACT results by the Actalyke-MaxACT were also shorter than ACT results by the Hemochron 801. Therefore, the authors established new therapeutic ranges appropriate to different clinical situations using the Actalyke-MaxACT system. For cardiac surgery with cardiopulmonary bypass, the traditional target remained at 480 seconds, although this led to the use of more heparin. For cardiac catheterization, 180 to 240 seconds became the therapeutic target, and less than 160 seconds was the target during sheath removal. For extracorporeal membrane oxygenation procedures, the target range was established at 160 to 180 seconds. © 2003 Lippincott Williams & Wilkins, Inc.
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