Frank Rolf Dario, Brandenburg Vincent M, Lanzmich Regina, Floege Jürgen
Department of Nephrology and Clinical Immunlogy, University Hospital Aachen, D-52057 Aachen, Germany.
Nephrol Dial Transplant. 2004 Jun;19(6):1552-8. doi: 10.1093/ndt/gfh203. Epub 2004 Mar 19.
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.
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. Thrombin-antithrombin complexes were measured to detect coagulation activation.
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.
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.
低分子量肝素（LMWH）如达肝素在血液透析（HD）期间越来越多地用于抗凝。用于监测LMWH抗凝的现有实验室检测耗时且昂贵，传统活化凝血时间（ACT）的适用性存在争议。一种简单且廉价的床旁检测将很有用。
我们在9例接受静脉注射达肝素推注抗凝的慢性HD患者中，对体外和体内的Xa活化全血凝血时间（Xa-ACT）进行了研究，并将其与传统ACT进行比较。用显色法测定血浆抗Xa因子（抗Xa）活性。测量凝血酶 - 抗凝血酶复合物以检测凝血激活。
随着达肝素浓度升高，Xa-ACT和ACT延长。在体外，两种凝血时间均与抗Xa水平密切相关（分别为r = 0.94和0.89）。然而，与ACT相比，Xa-ACT在体外（健康血液：Xa-ACT 90 s/U vs ACT 26 s/U；尿毒症血液：Xa-ACT 96 s/U vs ACT 31 s/U）以及体内（Xa-ACT 81 s/U vs ACT 22 s/U）对LMWH更为敏感，并反映了不同强度的抗凝作用。初始剂量为80±11 U/kg体重的达肝素推注能够在长达4小时的HD期间预防凝血激活。
在HD期间，对于监测LMWH抗凝，Xa-ACT在体外和体内均优于传统ACT。Xa-ACT可作为LMWH床旁检测。ACT不够敏感，不能用作LMWH监测工具。
