LMW-HEPARIN/-HEPARINOID ANTI-XA ACTIVITY OBTAINED BY HMT (CELLITE) AND ACT (CELLITE, KAOLIN) PROCEDURES

Abstract

S187 The new heparin management test (HMT, dry chemistry) has been proved a reliable point-of-care system for monitoring unfractioned heparins during cardiopulmonary bypass (CPB) [1]. The HMT has been also shown to correlate well with the anti-Xa activity [1], which is regarded as a reference for the determination of plasma heparin levels. However, chromogen-measured anti-Xa activity does not only take into account the high-molecular-weight fractions of heparin, but also depends on the low-molecular-weight (LMW) fraction. The goal of the present study was to assess whether the optical HMT method reveals linearity with LMWH-anti-Xa activity, and to compare the results to the established mechanical ACT (activated clotting time) procedures (surface activator cellite or kaolin). METHODS: With approval of the local ethics comittee and written informed consent, 5 patients scheduled for elective CPB participated. Defined LMWH anti-Xa activities were achieved by spiking whole blood samples of each patient with 0.25 U/mL (range: 0 - 3 U/mL) of the heparinoid orgaran (NV Organon, OSS). Clotting times (sec) were obtained simultaneously with the cellite and kaolin ACT (Hemochron; ITC, Edison, NJ, USA) (spiked whole blood; n = 24), and the new cellite HMT method (Cardiovascular Diagnostics Inc., Raleigh, NC, USA) (citrated whole blood; n = 12). All samples were analyzed at 13 set points immediately after spiking (0-30 U/mL; duplicates, n = 72). RESULTS: The ACT and HMT values (sec) at defined concentrations of orgaran (U/mL) are shown below (mean values, U-test). (Figure 1)Figure 1CONCLUSION: Recently, in contrast to the ACT, the new cellite HMT has been shown to be independent of potential errors (e.g., due to aprotinin) [1]. Presently, the HMT additionally correlated well with LMWH-anti-Xa activity over a wide range, whereas the cellite ACT appears to be rather uninfluenced by this heparin fraction (i.e., not suitable). The molecular mechanism of this finding, however, remains a matter of speculation. Further studies will have to prove whether the HMT may develop routine on-line monitoring for high levels of both LMW-heparins and - heparinoids (e.g., orgaran), too, as occuring in invasive cardiology, hemodialysis, and CPB (including patients with heparin-induced thrombocytopenia type II).