Inactivated antithombin as anticoagulant reversal in a rat model of cardiopulmonary bypass: a potent and potentially safer alternative to protamine.

Heparin anticoagulation followed by protamine reversal is commonly used in cardiopulmonary bypass (CPB). As an alternative to protamine, a recombinant inactive antithrombin (riAT) was designed as an antidote to heparin and was previously shown to be as potent as protamine in-vitro. In the present study, riAT was assessed for its ability to neutralize heparin after CPB in a rat model. After 60 min of CPB under heparin, rats received 5 mg/kg protamine, 37.5 mg/kg riAT or phosphate buffered saline (PBS) as placebo. Residual anticoagulant activity was assessed using the activated partial thromboplastin time assay before, and 10-30 min after reversion. Haemodynamic monitoring was performed and plasma histamine concentration was also measured. In this model, riAT appeared to be as efficient as protamine in neutralizing heparin. Ten minutes after injection, riAT and protamine both decreased heparin activity, to 1.8 ± 1.3 and 4.5 ± 1.4 u/ml, respectively (23.1 ± 5.1 u/ml in placebo group). Furthermore, evolution of mean carotid arterial pressure, heart rate and plasma histamine levels was comparable in rats treated with PBS or riAT, while protamine exhibited haemodynamic side effects and increased histamine plasma concentration. Thus, riAT could represent an advantage over protamine in CPB because it efficiently reverses heparin activity without negative effects on haemodynamic parameters and plasma histamine level.

Performance evaluation of the fully automated random-access multiparameter Sysmex CN-6000 hemostasis analyzer at a core laboratory with a high sample throughput.

INTRODUCTION: We aimed to evaluate the performance of the fully automated multiparameter CN-6000 hemostasis analyzer. METHODS: Performance evaluation of the CN-6000 analyzer was conducted for 10 tests including prothrombin time (PT), activated partial prothrombin time (aPTT), fibrinogen level, anti-Xa activity, and antithrombin activity using a unique portfolio of liquid ready-to-use reagents. Precision, sample and reagent carryovers, throughput, and sample turnaround time (STAT) function were prospectively assessed. Results from 343 samples (normal subjects, critically ill patients, patients receiving anticoagulants, subjects with high or low fibrinogen levels, and patients with decreased levels of factor II, V, VII, and X) were compared to those obtained on the STA-R Max 2® analyzer using dedicated reagents. RESULTS: Total precision (coefficient of variation) was below 7% for all parameters in both normal and pathological ranges. For all analyzed parameters, results obtained on the CN-6000 were strongly correlated with those obtained on the STA-R Max 2®analyzer. Agreement between both instruments was excellent for all assays. The CN-6000 demonstrated a 30% higher throughput compared to the STA-R Max 2® (258 vs 185 tests per hour for a panel of tests including PT, aPTT, fibrinogen, factor V, anti-Xa, and D-Dimer). STAT turnaround time for critical care samples testing was <7 minutes. CONCLUSIONS: The CN-6000 analyzer performs equivalently or better than the STA-R Max 2® with a significantly improved throughput. This new hemostasis multiparameter analyzer appears to be particularly well suited for coagulation laboratories which require high sample throughput and manage high numbers of nonstandard and critical care samples.

Inactivated antithrombins as fondaparinux antidotes: a promising alternative to haemostatic agents as assessed in vitro in a thrombin-generation assay.

In the absence of specific antidote to fondaparinux, two modified forms of antithrombin (AT), one recombinant inactive (ri-AT) and the other chemically inactivated (chi-AT), were designed to antagonise AT-mediated anticoagulants, e. g. heparins or fondaparinux. These inactive ATs were previously proven to effectively neutralise anticoagulant activity associated with heparin derivatives in vitro and in vivo, as assessed by direct measurement of anti-FXa activity. This study was undertaken to evaluate in vitro the effectivity of inactive ATs to reverse anticoagulation by heparin derivatives and to compare them with non-specific fondaparinux reversal agents, like recombinant-activated factor VII (rFVIIa) or activated prothrombin-complex concentrate (aPCC), in a thrombin-generation assay (TGA). Addition of fondaparinux (3 µg/ml) to normal plasma inhibited thrombin generation by prolonging lag time (LT) as much as 244 % and lowering endogenous thrombin potential (ETP) to 17 % of their control (normal plasma) values. Fondaparinux-anticoagulant activity was reversed by ri-AT and chi-AT, as reflected by the corrections of LT up to 117 % and 114 % of its control value, and ETP recovery to 78 % and 63 %, respectively. Unlike ri-AT that had no effect on thrombin generation in normal plasma, chi-AT retained anticoagulant activity that minimises its reversal capacity. However, both ATs were more effective than rFVIIa or aPCC at neutralising fondaparinux and, unlike non-specific antidotes, inactive ATs specifically reversed AT-mediated anticoagulant activities, as suggested by their absence of procoagulant activity in anticoagulant-free plasma.