Whole Blood Point-of-Care Testing for Incomplete Reversal With Idarucizumab in Supratherapeutic Dabigatran.

BACKGROUND: Incomplete reversal with a recommended 5-g dose of idarucizumab has been reported in patients with excessively high dabigatran concentrations. A timely detection of reversal failure after idarucizumab using whole blood (WB) coagulation testing is clinically useful. The aims of this study were to determine residual dabigatran activity after idarucizumab on thrombin generation (TG) using in vitro supratherapeutic dabigatran models and to compare 4 WB point-of-care tests (activated partial thromboplastin time [aPTT], prothrombin time [PT], and 2 thromboelastometry tests) with the TG results. METHODS: Blood samples from 12 healthy volunteers were spiked in vitro with 0-5000 ng/mL of dabigatran. Dabigatran reversal was evaluated by adding 1000 µg/mL of idarucizumab (Praxbind) to dabigatran-spiked samples, which reflect the administration of 5-g idarucizumab to a 70-kg patient. Residual dabigatran activity was assessed using the calibrated automated TG (Thrombinoscope) in platelet-poor plasma samples. The TG results were compared with WB aPTT (DRIHEMATO APTT-S) and PT (DRIHEMATO PT-S) using CG02N analyzer, thromboelastometry (ROTEM) triggered by ellagic acid (INTEM) and tissue factor (EXTEM). RESULTS: At a therapeutic concentration of dabigatran (200 ng/mL), the lag time was prolonged, and peak TG was decreased. The effects of dabigatran on TG were increased up to 1000 ng/mL, and TG was obliterated at higher supratherapeutic dabigatran levels (P < .001 versus control, respectively). TG was fully restored with idarucizumab when dabigatran was ≤2000 ng/mL, but residual anticoagulant activity was observed at higher dabigatran levels. Dabigatran prolonged WB aPTT and PT concentration dependently, and residual prolongations were observed when idarucizumab was added to 3000 or 5000 ng/mL of dabigatran (P < .001 versus control, respectively). In contrast, both INTEM and EXTEM clotting times were reversed toward reference ranges at all dabigatran concentrations when idarucizumab was added. CONCLUSIONS: Our data indicate that the recommended dose of idarucizumab may not restore TG completely with excessively elevated concentrations of dabigatran. All WB measurements with aPTT, PT, and thromboelastometry predicted supratherapeutic dabigatran concentrations, whereas those tests varied in sensitivity to residual anticoagulant activity after reversal. WB aPTT corresponded well with plasma TG changes among those measurements, but the use of thromboelastometry may overestimate the effect of idarucizumab. Caution should be exercised before extrapolating in vitro point-of-care data to the clinical monitoring of dabigatran reversal.

Prohemostatic Activity of Factor X in Combination With Activated Factor VII in Dilutional Coagulopathy.

BACKGROUND: Recombinant activated factor VII (rFVIIa) concentrate reduces allogeneic blood transfusions, but it may increase thromboembolic complications in complex cardiac surgery. The mixture of activated factor VII (FVIIa) and factor X (FX) (FVIIa/FX) (FVIIa:FX = 1:10) is a novel bypassing agent for hemophilia patients. We hypothesized that the combination of FX and FVIIa could improve thrombin generation (TG) in acquired multifactorial coagulation defects such as seen in cardiac surgery and conducted in vitro evaluation of FVIIa/FX in parallel with other coagulation factor concentrates using in vitro and in vivo diluted plasma samples. METHODS: Plasma samples were collected from 9 healthy volunteers and 12 cardiac surgical patients. We measured TG (Thrombinoscope) using in vitro 50% dilution plasma and in vivo dilution plasma after cardiopulmonary bypass, in parallel with thromboelastometry (ROTEM) and standard coagulation assays. In vitro additions of FVIIa/FX (0.35, 0.7, and 1.4 µg/mL, based on the FVIIa level), rFVIIa (1.4, 2.8, and 6.4 µg/mL), prothrombin complex concentrate (0.3 international unit), and 20% plasma replacement were evaluated. RESULTS: In diluted plasma, the addition of either FVIIa/FX or rFVIIa shortened the lag time and increased the peak TG, but the effect in lag time of FVIIa/FX at 0.35 µg/mL was more extensive than rFVIIa at 6.4 µg/mL. Prothrombin complex concentrate increased peak TG by increasing the prothrombin level but failed to shorten the lag time. No improvement in any of the TG variables was observed after 20% volume replacement with plasma. The addition of factor concentrates normalized prothrombin time/international normalized ratio but not with plasma replacement. In cardiac patients, similar patterns were observed on TG in post-cardiopulmonary bypass samples. FVIIa/FX shortened clotting time (CT) in a concentration-dependent manner on CT on thromboelastometry. Plasma replacement did not improve CT, but a combination of plasma and FVIIa/FX (0.35 µg/mL) more effectively shortened CT than FVIIa/FX alone. CONCLUSIONS: The combination of FVIIa and FX improved TG more efficiently than rFVIIa alone or plasma in dilutional coagulopathy models. The required FVIIa dose in FVIIa/FX was considerably lower than those reported during bypassing therapy in hemophilia patients (1.4-2.8 µg/mL). The combination of plasma could restore coagulation more efficiently compared to FVIIa/FX alone. Lesser FVIIa requirement to exert procoagulant activity may be favorable in terms of reducing systemic thromboembolic complications.

A Comparative Study of Point-of-Care Prothrombin Time in Cardiopulmonary Bypass Surgery.

OBJECTIVE: Point-of-care (POC) devices allow for prothrombin time/international normalized ratio (PT/INR) testing in whole blood (WB) and timely administration of plasma or prothrombin complex concentrate during cardiopulmonary bypass surgery. This study evaluated the sensitivities of a new POC PT test, a dry-hematology method with heparin neutralization technology (DRIHEMATO PT-S [DRI PT-S]; A&T Corporation, Kanagawa, Japan), and compared it with other POC tests currently available. DESIGN: Prospective, observational study. SETTING: University hospital, single center. PARTICIPANTS: Healthy volunteers and warfarin-treated and cardiac surgical patients. MEASUREMENT AND MAIN RESULTS: In WB samples obtained from 6 healthy volunteers, PT-INR results of DRI PT-S were not affected by an in vitro addition of heparin <6.0 U/mL. In warfarin-treated samples (n = 88, PT/INR 0.98-3.87), PT-INR with DRI PT-S showed acceptable correlation with the laboratory method (r2 = 0.85, p < 0.001). In blood samples obtained from cardiac surgical patients (n = 72), heparin prolonged the PT/INR with the laboratory assay, dry-hematology method with non heparin neutralization technology (DRI PT), Coaguchek XS (Roche Diagnostics, Basel, Switzerland), and Hemochron Jr. (Accriva Diagnostics, Edison, NJ), but DRI PT-S was not affected by heparin anticoagulation. In nonheparinized samples, different methods between DRI PT-S and the laboratory method yielded acceptable correlations (r2 = 0.76, p < 0.0001). There was a moderate correlation between factor levels and the PT-INR with DRI PT-S (factor [F]II: r2 = 0.63, FVII: r2 = 0.47, FX: r2 = 0.67; p < 0.0001). CONCLUSIONS: This study demonstrated that PT/INR can be accurately assessed using the dry-hematology method in WB under therapeutic heparin levels. Currently available other POC PT/INR tests are affected by heparin, and thus they are not recommended for coagulation monitoring during cardiopulmonary bypass.