Measurement of whole blood factor Xa-activated clotting time during hemodialysis with low-molecular-weight heparin

Purpose To determine whole blood factor Xa-activated clotting time (XaACT), a test for monitoring low-molecular-weight heparins (LMWHs). Methods Blood was obtained from six healthy volunteers. Dalteparin, a LMWH, was mixed with the blood to concentrations of 0,05 and 1.0IU·ml⁻¹. XaACT, activated clotting time (ACT), and activated partial thromboplastin time (APTT) were measured at each dalteparin concentration. XaACT of blood from the outflow and inflow sides of the blood circuit in seven hemodialysis patients was measured before and after bolus administration of 1000 IU of dalteparin, followed by continuous infusion at a rate of 500IU·h⁻¹. Results XaACT, ACT, and APTT in dalteparin-containing blood from volunteers were correlated with dalteparin concentration (y=312.8x+86.4;r ²=0.88;P<0.001,y=41.8x +113.5;r ²=0.83;P<0.001, andy=59.5x+38.8;r ²=0.80;P<0.001, respectively). The regression slope of XaACT was steeper than those of ACT and APTT (P<0.001). In hemodialysis patients, dalteparin increased XaACT on the outflow and inflow sides of the circuit (P<0.001,P<0.05, respectively). Conclusion The measurement of XaACT can be employed to monitor LMWHs in clinical settings.