The anticoagulant effect of therapeutic levels of dabigatran in atrial fibrillation evaluated by thrombelastography (TEG®), Hemoclot Thrombin Inhibitor (HTI) assay and Ecarin Clotting Time (ECT).

Monitoring the effect of dabigatran (Pradaxa®) is challenging. The aim of this study was to evaluate if thrombelastography reaction time (TEG® R) could detect the anticoagulant effect of dabigatran showing a correlation between TEG® R, Hemoclot Thrombin Inhibitor (HTI) assay and Ecarin Clotting Time (ECT) in patients with non-valvular atrial fibrillation (NVAF). Blood samples from 35 AF patients receiving either 110 mg (n 19) or 150 mg (n 16) dabigatran twice daily were analyzed with TEG®, HTI and ECT 2-3 h after dabigatran intake. All patients had prolonged TEG® R. The patients receiving dabigatran 110 mg ×2 had a TEG® R mean 14.2 min (range 9.1-25), a mean dabigatran concentration measured by HTI of 268.5 ng/mL (range 54-837 ng/mL) and by ECT of 355.7 ng/mL (range 40-1020 ng/mL). The corresponding numbers for patients receiving dabigatran 150 mg ×2 were TEG® R mean of 12.5 min (range 9.2-23.2 min), mean dabigatran concentration of 179.2 ng/mL by HTI (range 26-687 ng/mL) and by ECT 225.1 ng/mL (range 42-1020 ng/mL). The two dosage groups had comparable anticoagulation demonstrated by equally prolonged TEG® R (p = .909), HTI (p = .707) and ECT (p = .567). No difference in creatinine levels in the two dosage groups was observed (p = .204) though patients with dabigatran concentration >400 ng/mL had significantly higher creatinine levels (p = .001). Large individual variation of the anticoagulant response was observed. Some patients had TEG® R values up to three times upper normal limit with immediate risk of bleeding. Our data indicate that TEG® R reflected dabigatran levels in NVAF patients and that TEG® R correlated to HTI and ECT.

Impact of blood products on platelet function in patients with traumatic injuries: a translational study.

BACKGROUND: Reductions in platelet (PLT) count and function are associated with poor outcomes in trauma patients. We proposed to determine if patients expected to receive blood products have a decrease in PLT function higher than expected based on the reduction in PLT count, and if the reduction in function could be associated with the donor plasma/supernatant received. METHODS: PLT count and function were measured on admission to the emergency department and intensive care unit in severely injured patients expected to receive a transfusion. PLT function was measured by Multiplate aggregometry in response to five agonists. Function was corrected for alterations in count. In vitro studies were conducted in the blood of normal subjects to assess the effect of dilutions with AB donor plasma on PLT function. RESULTS: Forty-six patients were enrolled, with 87% requiring a transfusion. Median Injury Severity Score was 23 (13, 29) and mortality 15%. PLT count and function were decreased from emergency department to intensive care unit admission by 25% and 58%, respectively. Decreases in function persisted after adjustment for count. Patients requiring large volumes of blood products had reductions in function that were disproportionately greater. Reductions in PLT function were greatest after transfusion of PLTs. In in vitro studies with a 30% dilution by autologous plasma caused a relational reduction in function, whereas allogenic plasma resulted in greater decreases that were highly variable between donors. CONCLUSIONS: Within hours of injury a decrease in both PLT count and function occurs, that is aggravated with the administration of blood products, with transfusion of PLTs showing the greatest effect. The effect on PLT function of allogenic transfused plasma appears to be highly donor related.

Thrombelastography detects dabigatran at therapeutic concentrations in vitro to the same extent as gold-standard tests.

BACKGROUND/OBJECTIVES: Dabigatran is an oral anticoagulant approved for treatment of non-valvular atrial fibrillation, deep venous thrombosis (DVT), pulmonary embolism and prevention of DVT following orthopedic surgery. Monitoring of the dabigatran level is essential in trauma and bleeding patients but the available plasma-based assays may not sufficiently display its hemostatic effect. This study investigated the in vitro effect of different concentrations of dabigatran on whole blood thrombelastography (TEG) and its correlation to the specific but time-consuming plasma-based tests Hemoclot and Ecarin Clotting Time (ECT). METHOD: Blood was collected from 8 healthy donors (two females, six males) with a median age of 46 years and it was spiked with dabigatran to a range of plasma concentrations (0, 50, 100, 200 and 400 ng/ml) covering the therapeutic level. RESULTS: Mean TEG R at 0 ng/ml=5.963 min, 50 ng/ml=7.425 min, 100 ng/ml=8.425 min, 200 ng/ml=9.775 min, 400 ng/ml=11.813 min. A significant overall increase (p=0.001) in TEG reaction time (R) was found across increasing dabigatran concentrations i.e. 0 vs 50 vs 100 vs 200 vs 400 ng/ml (p<0.000 p=0.027 p=0.026, p=0.005, respectively). TEG R correlated strongly with Hemoclot (R(2)=0.891, p<0000) and ECT (R(2)=0.914, p<0.000) and Hemoclot and ECT were strongly inter-correlated (R(2)=0.978, p<0.000). CONCLUSION: The whole blood viscoelastic assay TEG R displayed linearity towards fixed concentrations of dabigatran and correlated strongly to the current gold-standard tests Hemoclot and ECT, for assessing dabigatran. TEG R is applicable as a rapid and precise whole blood monitoring test for dabigatran treated patients in the emergency setting.

Monitoring of dabigatran anticoagulation and its reversal in vitro by thrombelastography.

BACKGROUND: Dabigatran etexilate, a pro-drug of a direct thrombin inhibitor, was approved a few years ago for non-valvular atrial fibrillation and deep venous thrombosis. Rapid monitoring of the dabigatran level is essential in trauma and bleeding patients but the traditional plasma-based assays may not sufficiently display the effect. Furthermore, no antidote exists and reversal of the anticoagulant effect is impossible or difficult. The present study investigated the in vitro effect of dabigatran on whole blood thromboelastography (TEG) and its reversal by recombinant activated factor VII and prothrombin complex concentrate. METHODS: Blood was collected from 10 healthy donors and spiked in vitro with therapeutic doses of dabigatran to a plasma concentration of 200 ng/ml, followed by therapeutic doses of recombinant activated factor VII (corresponding to 100 µg/kg) and prothrombin complex concentrate (corresponding to 50 IE/kg) and evaluated by TEG. RESULTS: Compared to baseline, dabigatran changed all TEG parameters in a hypocoagulable direction corresponding to increased R time and time to maximum rate of thrombus generation, reduced angle, A5, A10, maximum amplitude and maximum rate of thrombin formation. Recombinant activated factor VII had a procoagulant effect on the majority of the investigated TEG parameters when added to dabigatran spiked samples. Prothrombin complex concentrate appeared not to have a procoagulant effect on TEG even when the heparin content in the formulation was neutralized by heparinase. CONCLUSIONS: TEG displays the presence of dabigatran in whole blood in vitro and the anticoagulant effect of dabigatran is partly reversed by spiking with recombinant activated factor VII.

Dabigatran and its reversal with recombinant factor VIIa and prothrombin complex concentrate: a Sonoclot in vitro study.

OBJECTIVE: Dabigatran is a new oral direct thrombin inhibitor. No specific antidote exists in the event of hemorrhage, but prothrombin complex concentrate (PCC) and recombinant activated factor VII (rFVIIa) are suggested therapies. Sonoclot is a bedside viscoelastic instrument for monitoring the coagulation process in whole blood. The aim of this study was to investigate the effect of dabigatran and reversal with PCC and rFVIIa, as monitored by the Sonoclot. METHODS: Citrated whole blood was drawn and mixed in vitro with dabigatran, dabigatran + PCC or dabigatran + rFVIIa and analyzed with three different Sonoclot cuvettes: Glassbead, kaolin and tissue factor (diluted) activated. RESULTS: The Sonoclot detected in vitro-induced anticoagulation due to dabigatran with the glassbead- and kaolin-activated cuvettes. There was no reversing effect of PCC, probably due to the presence of heparin in the PCC we used. There was no certain reversing effect of rFVIIa. CONCLUSIONS: The Sonoclot can detect the anticoagulant effect of dabigatran. Our results do not support efficient reversal of dabigatran with PCC and rFVIIa, or alternatively do not support the ability of Sonoclot to detect a reversing effect of the PCC and rFVIIa in our study. Clinical studies of dabigatran-treated patients with severe bleeding are called for, as well as the continued development of specific antidotes and monitoring techniques.

Trauma-induced coagulopathy: standard coagulation tests, biomarkers of coagulopathy, and endothelial damage in patients with traumatic brain injury.

It remains to be debated whether traumatic brain injury (TBI) induces a different coagulopathy than does non-TBI. This study investigated traditional coagulation tests, biomarkers of coagulopathy, and endothelial damage in trauma patients with and without TBI. Blood from 80 adult trauma patients was sampled (median of 68 min [IQR 48-88] post-injury) upon admission to our trauma center. Plasma/serum were retrospectively analyzed for biomarkers reflecting sympathoadrenal activation (adrenaline, noradrenaline), coagulation activation/inhibition and fibrinolysis (protein C, activated protein C, tissue factor pathway inhibitor, antithrombin, prothrombin fragment 1+2, thrombin/antithrombin complex, von Willebrand factor, factor XIII, d-dimer, tissue-type plasminogen activator, plasminogen activator inhibitor-1), immunology (interleukin [IL]6), endothelial cell/glycocalyx damage (soluble thrombomodulin, syndecan-1), and vasculogenesis (angiopoietin-1, -2). Patients were stratified according to: (1) isolated severe head/neck injuries (Abbreviated injury score [AIS]-head/neck ≥ 3, AIS-other<3) (isoTBI); (2) severe head/neck and extracranial injuries (AIS-head/neck ≥ 3, AIS-other>3) (sTBI+other); and (3) injuries without significant head/neck injuries (AIS-head/neck<3, including all AIS-other scores) (non-TBI). Twenty-three patients presented with isoTBI, 15 with sTBI+other and 42 with non-TBI. Acute coagulopathy of trauma shock, defined as activated partial thromboplastin time (APTT) and/or international normalized ratio (INR)>35 sec and>1.2, was found in 13%, 47%, and 5%, respectively (p=0.000). sTBI+other had significantly higher plasma levels of adrenaline, noradrenaline, annexin V, d-dimer, IL-6, syndecan-1, soluble thrombomodulin, and reduced protein C and factor XIII levels (all p<0.05). No significant biomarker differences were found between isoTBI and non-TBI patients. Injury severity scale (ISS) rather than the presence or absence of head/neck injuries determined the hemostatic and biomarker response to the injury. The coagulopathy identified thus reflected the severity of injury rather than its localization.

In-vitro comparison of free oscillation rheometry (ReoRox) and rotational thromboelastometry (ROTEM) in trauma patients upon hospital admission.

Plasma-based assays do not provide accurate information on haemostatic resuscitation hence viscoelastic point-of-care haemostatic assays such as rotational thromboelastometry (ROTEM Delta, Pentapharm) are used to monitor coagulopathy in trauma patients. Free oscillation rheometry (FOR) is a new whole blood haemostatic assay that measures not only the clot-forming process but also the initial viscous phase; this could potentially be of value when assessing traumatic coagulopathy. A comparative analysis between FOR and ROTEM was therefore performed. This is a prospective observational study of 40 adult trauma patients admitted to a level 1 trauma centre. Citrated whole blood was analysed with ROTEM EXTEM and FIBTEM assays and FOR Fibscreen1 and Fibscreen2 assays. Predefined variables of ROTEM and FOR were compared using Spearman's ρ. ROTEM maximum clot function (MCF) in both EXTEM and FIBTEM correlated (P < 0.0001 for both) with FOR maximum elasticity Fibscreen1 and Fibscreen2, respectively. Interestingly, ROTEM EXTEM clotting time did not correlate with any of the FOR clot initiation parameters COT1, COT2 or COT2-1 of Fibscreen1. A correlation between ROTEM EXTEM and FIBTEM and FOR Fibscreen1 and Fibscreen2 clot formation and clot strength was found as was a significant correlation between lysis index after 60 min and ClotSR30. ROTEM EXTEM did not correlate with COT1, COT2 or COT2-1 of Fibscreen1 and this warrants further investigation.

A review of the clinical utility of INR to monitor and guide administration of prothrombin complex concentrate to orally anticoagulated patients.

BACKGROUND AND OBJECTIVES: The number of patients treated with oral anticoagulation (OAC) is increasing and these patients are monitored by International Normalized Ratio (INR). Bleeding complications are common and we speculate if this is related to the limitation of INR only reflecting the initiation steps of the haemostatic process. The objective of the present review was to reassess the evidence for using INR as a tool to guide administration of prothrombin complex concentrates (PCC) to OAC patients. A Medline and Cochrane database search was conducted using the following keywords: prothrombin complex concentrate, reversal of oral anticoagulation and international normalized ratio (INR). Thirty-three articles were contracted and a total of ten studies were eligible after applying inclusion and exclusion criteria encompassing only 339 patients. No consensus regarding optimal target INR value to aim for when reversing OAC was found. In three of the studies it was reported that patients reaching their target INR continued to bleed, whereas three studies reviewed reported good haemostatic response also in patients that did not reach their target INR. The present review found limited evidence for the usefulness of INR as a tool to monitor and guide reversal of OAC induced coagulopathy in patients with PCC, which is expected given that it is a plasma-based assay only reflecting a limited part of the haemostatic process.

Coagulopathy and hemostatic monitoring in cardiac surgery: an update.

OBJECTIVES: Cardiac surgery with cardiopulmonary bypass (CPB) causes severe derangements in the hemostatic system, which in turn puts the patient at risks of microvascular bleeding. Excessive transfusion and surgical re-exploration after cardiac surgery are potentially associated with a number of adverse outcomes including increased mortality. DESIGN: This review describes coagulopathies occurring in cardiac surgery and the monitoring of these. Viscoelastic hemostatic assays (VHA) have routinely been used in cardiac surgery for more than 25 years and at least 16 studies (involving more than 3250 patients, including three randomized controlled trials) have compared VHA to routine coagulation tests (RCoT) with regards to their ability to predict bleeding and re-do surgery and also with regards to transfusion requirements secondary to hemostatic therapy based on VHA vs. RCoT. RESULTS: All 16 studies demonstrated superiority with VHA as compared to RCoT both in predicting bleeding and need for re-do surgery and in reducing the total amount of blood transfusions by employing goal-directed administration of blood products based on VHA as compared RCoT based therapy or at the clinicians discretion. CONCLUSIONS: The different types of coagulopathies observed in patients undergoing cardiac surgery requires adequate and timely hemostatic therapy and real-time monitoring with WHA such as TEG/ROTEM and whole blood platelet aggregometry.