BackgroundAn increasing number of patients are treated with direct-acting oral anticoagulants (DOACs), but the optimal way to reverse the anticoagulant effect is not known. Specific antidotes are not available and prothrombin complex concentrate (PCC), activated PCC (aPCC) and recombinant factor VIIa (rFVIIa) are variously used as reversal agents in case of a major bleeding. We aimed to determine the most effective haemostatic agent and dose to reverse the effect of rivaroxaban in blood samples from patients taking rivaroxaban for therapeutic reasons.MethodsBlood samples from rivaroxaban-treated patients (n = 50) were spiked with PCC, aPCC and rFVIIa at concentrations imitating 80%, 100% and 125% of suggested therapeutic doses. The reversal effect was assessed by thromboelastometry in whole blood and a thrombin generation assay (TGA) in platelet-poor plasma. Samples from healthy subjects (n = 40) were included as controls.ResultsIn thromboelastometry measurements, aPCC and rFVIIa had a superior effect to PCC in reversing the rivaroxaban-induced lenghtening of clotting time (CT). aPCC was the only haemostatic agent that shortened the CT down to below the control level. Compared to healthy controls, patients on rivaroxaban also had a prolonged lag time and decreased peak concentration, velocity index and endogenous thrombin potential (ETP) in platelet-poor plasma. aPCC reversed these parameters more effectively than rFVIIa and PCC. There were no differences in efficacy between 80%, 100% and 125% doses of aPCC.ConclusionsaPCC seems to reverse the anticoagulant effect of rivaroxaban more effectively than rFVIIa and PCC by evaluation with thromboelastometry and TGA in vitro.

An anti-FXa activity above 0.4 IU/ml after 4 h of dialysis inhibits significant clotting during haemodialysis. A bolus dose of dalteparin of 70 IU/kg usually seems appropriate, but may be reduced in patients on warfarin treatment. Dialysis time is an independent risk factor for clinical clotting.

Despite clinically effective anticoagulation, obtained by dalteparin administration, platelets and coagulation are activated by HD, resulting in a potentially thrombophilic state. Warfarin treatment reduces clinical clot formation and subclinical activation of coagulation.

Haemophilia patients with inhibitors require bypassing agents (BPA) like activated prothrombin complex concentrate (aPCC) and recombinant activated factor VII (rFVIIa) to control bleeds. Adjunct tranexamic acid (TXA) may improve haemostasis. The objective of this study was to investigate safety and haemostatic effect of TXA given in combination with BPA. Healthy volunteers (N = 5) and haemophilia inhibitor patients (N = 6) were enrolled in a prospective case crossover design. Controls were treated with TXA 20 mg kg(-1) orally (O.R.) Patients were treated with aPCC 75 IU kg(-1) intravenous (I.V.) on day 1 followed by TXA 20 mg kg(-1) O.R. combined with aPCC 75 IU kg(-1) I.V. on day 2. A 14-day washout occurred before crossover to rFVIIa 90 μg kg(-1) I.V. ±TXA. Safety evaluation and blood sampling processes were performed at baseline, 15, 30, 60, 120, 180 and 240 min post treatment. Primary outcome was maximum clot firmness (MCF) evaluated by whole blood thromboelastometry using a TF + tissue plasminogen activator-based assay. Healthy controls showed a 20-fold increase in MCF following TXA. Adjunct TXA to aPCC or rFVIIa induced a significant increase in MCF (P < 0.0001) reaching levels indistinguishable from healthy controls treated with TXA (P > 0.05). Infusion of aPCC or rFVIIa alone induced only 3-10 fold increase in MCF from baseline, with a decline in MCF starting after 60-120 min. TXA did not increase the endogenous thrombin potential. No clinical or laboratory signs of thromboembolic events, disseminated intravascular coagulation, or hypercoagulability were observed. Combination of aPCC or rFVIIa with TXA normalizes clot stability in haemophilia patients with inhibitor as compared to healthy controls. No clinical or laboratory adverse events were observed.

The aim of this study was to evaluate the capability of thromboelastometry (ROTEM) and thrombin generation assay (TGA) to monitor the treatment response of bypassing agent (BPA) therapy and to study whether one method is superior to another. In a prospective crossover study haemophilia A patients with high titre inhibitors were included to receive a dose of 75 U kg(-1) activated prothrombin complex concentrates (aPCC) intravenously. Blood sampling was performed at baseline, 15, 30 min, 1, 2, 3 and 4 h post-infusion for TGA and ROTEM analysis. After a washout period of 14 days the subjects received recombinant FVIIa (rFVIIa) at a dose of 90 μg kg(-1) and similar blood sampling was performed. Healthy subjects were used as controls. Six haemophilia A patients with inhibitors were included. We found that TGA parameters endogenous thrombin potential (ETP) and peak thrombin increased 2-3 folds from baseline 15-30 min after infusion. ROTEM parameters MaxVel and maximum clot firmness increased to a level comparable to that of healthy controls. An individual difference in response was observed for different parameters among participants. ETP and peak thrombin were almost two-fold greater following aPCC infusion compared to rFVIIa, whereas ROTEM parameters showed no difference in response between the two products. The study showed that ROTEM and TGA have a great potential to evaluate the effect of BPA in haemophilia patients with inhibitors. TGA seemed to be more sensitive than ROTEM in reflecting the difference in treatment response between aPCC and rFVIIa. Additional prospective clinical studies are needed to clarify which assay and what parameters are clinically predictive.