NDT Advance Access originally published online on March 19, 2004
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Nephrol Dial Transplant (2004) 19: 1552-1558
Nephrol Dial Transplant Vol. 19 No. 6 © ERA-EDTA 2004; all rights reserved
Original Article
Factor Xa-activated whole blood clotting time (Xa-ACT) for bedside monitoring of dalteparin anticoagulation during haemodialysis
Department of Nephrology and Clinical Immunology, University Hospital Aachen, Germany
Correspondence and offprint requests to: Rolf Dario Frank, MD, Department of Nephrology, University Hospital Aachen, D-52057 Aachen, Germany. Email: dario.frank{at}ukaachen.de
Background. Low molecular weight heparins (LMWH) like dalteparin are increasingly used for anticoagulation during haemodialysis (HD). The available laboratory tests for monitoring LMWH anticoagulation are time-consuming and expensive, and the suitability of the conventional activated clotting time (ACT) is controversial. A simple and cheap bedside test would be useful.
Methods. We studied the factor Xa-activated whole blood clotting time (Xa-ACT) in vitro and in vivo in nine patients undergoing chronic HD with i.v. dalteparin bolus anticoagulation and compared it with the conventional ACT. Plasma anti-factor Xa (antiXa) activity was determined with a chromogenic assay. Thrombinantithrombin complexes were measured to detect coagulation activation.
Results. Xa-ACT and ACT were prolonged with rising dalteparin concentration. In vitro, both clotting times were strongly correlated with the antiXa levels (r = 0.94 and 0.89, respectively). Nevertheless, compared with the ACT, the Xa-ACT was considerably more sensitive to the LMWH in vitro (healthy blood: Xa-ACT 90 s/U vs ACT 26 s/U; uraemic blood: Xa-ACT 96 s/U vs ACT 31 s/U) as well as in vivo (Xa-ACT 81 s/U vs ACT 22 s/U) and reflected different intensities of anticoagulation. An initial dalteparin bolus of 80±11 U/kg body weight was able to prevent coagulation activation for up to 4 h of HD.
Conclusion. For monitoring LMWH anticoagulation the Xa-ACT was superior to the conventional ACT in vitro as well as in vivo during HD. The Xa-ACT can be useful as a LMWH bedside test. The ACT was not sensitive enough to serve as a LMWH monitoring tool.
Keywords: activated clotting time; haemodialysis; low molecular weight heparin; monitoring
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