ROTEM Analyses of Low Molecular heparin effects with Vitro Induced Thrombocytopenia

Abstract

Background: Thrombocytopenia is correlated to hemorrhagic complications in patients with low molecular weight heparin (LMWH) thromboprophylaxis. Aims: The aims of our study were to investigate an experimentally induced in vitro thrombocytopenia and then adding 2 types of LMWHs in vitro. Our hypothesis was that a platelet depleted whole blood sample could reflect a stronger synergistic anticoagulative effect of in vitro added LMWH than in the non-manipulated blood. Method: Two venous citrated blood samples were consecutively drawn from 8 patient’s gynaecologic cancer and normal routine coagulation laboratory analyses immediately preopewratively. One of the two samples had its buffy coat pipetted away into a separate tube. Half of the buffy coat was returned to the same sample (treated sample). 3x500 μl of blood from the non-treated sample was added to 3 separate microtubes and corresponding for the treated sample. Thromboprophylactic doses corresponding to an in vivo peak effect 0.5 anti-Xa international units/ml of tinzaparin and enoxaparin were added both to untreated and treated samples – 2 microtubes were unheparinized (treated/untreatedsample). All samples were analysed with rotational thromboelastometry (ROTEM). Results: Wilcoxon matched-pairs signed rank tests of the in-group differences between non-non-treated and treated samples showed no significant differences (p≤0.05) for any of the parameters analysed with the ROTEM-INTEM reagent regardless of heparinization or not. Calculation of non-parametric spearman correlation for clotting time (CT) vs. platelet count (PLC) were not significant for any group. Tinzaparin was clearly observed to prolong CT in the buffy-coat lowered blood from two patients. Conclusions: Our results corroborate previous research that ROTEM cannot detect anticoagulative effects of low dose LMWH in patients with normal PLC. In two patients there was a clear prolongation of clot initiation after tinzaparin that warrants further studies on a more developed in vitro induced thrombocytopenia model.