Search

Viscoelastic coagulation tests have been increasingly used for hemostasis management in cardiac surgery. The ClotPro system is a novel viscoelastic device based on principles of rotational thromboelastometry. We aimed to compare ClotPro with ROTEM and plasma coagulation assays in cardiopulmonary bypass (CPB) patients. Blood samples were collected from 25 CPB patients at (1) baseline, (2) start of CPB, (3) end of CPB, and (4) end of surgery. The EX-test, IN-test, HI-test, FIB-test parameters on ClotPro were compared with corresponding ROTEM assay (EXTEM, INTEM, HEPTEM, and FIBTEM). Standard plasma coagulation assays and endogenous thrombin generation (TG) were simultaneously evaluated. Pearson correlation analyses showed moderate correlations between clotting times (CTs) (r = 0.63-0.67; p < 0.001, respectively), and strong correlations with maximal clot firmness (MCF) (r = 0.93-0.98; p < 0.001, respectively) between ClotPro and ROTEM. EX-test and IN-test MCF parameters were interchangeable with acceptable percentage errors (EX-test MCF: 7.3%, IN-test MCF: 8.3%), but FIB-test MCF (27.0%) and CT results were not (EX-test CT: 44.7%, IN-test CT: 31.4%). The correlations of PT/INR or peak TG with EX-test CTs were higher than with EXTEM CTs (PT/INR: r = 0.80 and 0.41, peak TG: 0.43 and 0.18, respectively). FIB-test MCF has strong correlation with plasma fibrinogen and factor XIII level (r = 0.84 and 0.66, respectively). ROC analyses showed that ClotPro was capable of emulating well-established ROTEM thresholds (area under curves: 0.83-1.00). ClotPro demonstrated strong correlations in MCF parameters of ROTEM in CPB patients. It may be reasonable to modify ROTEM-based transfusion algorithm pertaining to MCF parameters to establish cut-off values for ClotPro device., (© 2022. The Author(s).)

Introduction: The methods of viscoelastic coagulation testing (VCT) have evolved since the original invention of thrombelastography over 60 years ago, and new generations of devices are clinically used to guide hemostatic interventions at bedside. The utility of VCTs has been demonstrated in several clinical trials, but diagnostic performance of VCT may vary between devices, various transfusion algorithms, and patient populations., Areas Covered: Working principles and currently available data on the evolving VCTs for coagulation monitoring in acute care settings are reviewed. The PubMed database was used to search pertinent retrospective, prospective, and meta-analysis data on VCTs., Expert Opinion: Point-of-care VCTs provide clinically useful information on platelet count, fibrin polymerization, and other procoagulant factor activities in acute bleeding due to trauma or major surgery, and antithrombotic therapy. The addition of fibrin-specific VCT channel has brought renewed attention to early correction of fibrinogen deficiency using fibrinogen-rich component therapy, and stabilization of fibrin with antifibrinolytic agents. Normal reference ranges vary between devices, and diagnostic and treatment algorithms should be specifically established for each device and indication. There is interest in utilizing VCTs in complex coagulation management relating to hemophilia with inhibitors, but the standardized protocol has not been established.

Objective: To explore how cytochalasin D (CyD) affects clot initiation and to compare clotting times (CTs) of EXTEM and FIBTEM on rotational thromboelastometry in cardiac surgical patients undergoing cardiopulmonary bypass (CPB)., Design: Retrospective cohort study with translational in vitro coagulation experiments., Setting: Single-center, tertiary, academic medical center., Participants: Patients who underwent cardiac surgery with CPB between November 2015 and August 2017., Intervention: None., Measurements and Main Results: The study's primary measurements were CT EXTEM and CT FIBTEM before and after CPB. Additionally, the authors performed translational in vitro coagulation experiments using commercial plasma. In these experiments, the impact of CyD on in vitro thrombin generation (TG) was assessed using 10 platelet-rich plasma (PRP) samples and calibrated automated thrombogram. The impact of CyD on ROTEM-CT also was evaluated in vitro using the same 10 PRP samples. One hundred fifty-three patients had clinical CT EXTEM and CT FIBTEM measurements. CT FIBTEM was shorter than CT EXTEM before and after CPB by 6.8% (95% confidence interval [CI], 5.5-8.1) and 8.9% (95% CI, 4.7-13.0), respectively. These results correlated with in vitro experiments, where TG lag time was shortened by CyD and CT FIBTEM was shorter than CT EXTEM ., Conclusion: CyD shortens the onset of TG and clot formation, resulting in shorter CT FIBTEM than CT EXTEM . The authors' data suggest that CT EXTEM and CT FIBTEM are not interchangeable. Additional clinical studies are warranted to assess if CT FIBTEM can be used to optimize the indication for plasma transfusion., Competing Interests: Declaration of Competing Interest MJ and KAT have participated in clinical validation studies sponsored by Instrumentation Laboratory (Bedford, MA)., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Coagulopathy is common in multitrauma patients and repletion of procoagulant factor deficiency with fresh frozen plasma (FFP) improves hemostasis. Optimal kaolin-thromboelastography thresholds for FFP transfusion in trauma patients have not been well established., Study Design: Adult trauma patients with an Injury Severity Score ≥15 were included in this retrospective observational cohort study. The primary end point was area under the receiver operating characteristic curve (AUROC) for reaction time (R-time) to detect procoagulant factor deficiency, as reflected by an elevated international normalized ratio (INR) or aPTT. Test characteristics for the optimal R-time threshold calculated in our study were compared against thresholds recommended by the American College of Surgeons for FFP transfusion., Results: Six hundred and ninety-four pairs of thromboelastography and conventional coagulation tests were performed in 550 patients, with 144 patients having additional pairs of tests after the first hour. The R-time was able to detect procoagulant factor deficiency (INR ≥1.5 AUROC 0.80; 95% CI, 0.75 to 0.85; aPTT ≥40 seconds AUROC 0.85; 95% 0.80 to 0.89) and severe procoagulant factor deficiency (INR ≥2.0 AUROC 0.82; 95% CI, 0.73 to 0.99; aPTT ≥60 seconds AUROC 0.89; 95% CI, 0.81 to 0.98) with good accuracy. Optimal thresholds to maximize sensitivity and specificity were 3.9 minutes for detection of INR ≥1.5, 4.1 minutes for detection of aPTT ≥40 seconds, 4.3 minutes for detection of INR ≥2.0, and 4.3 for detection of aPTT ≥60 seconds. Currently recommended R-time thresholds for FFP transfusion had 100% specificity for detecting procoagulant factor deficiency, but low sensitivity (3% to 7%)., Conclusions: R-time can detect procoagulant factor deficiency in multitrauma patients with good accuracy, but currently recommended R-time thresholds are highly specific and not sensitive. Use of low-sensitivity thresholds might result in undertreatment of many patients with procoagulant factor deficiency., (Copyright © 2020 American College of Surgeons. Published by Elsevier Inc. All rights reserved.)

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.

Background: Acute traumatic coagulopathy is common in trauma patients. Prompt diagnosis of hypofibrinogenemia allows for early treatment with cryoprecipitate or fibrinogen concentrate. At present, optimal cutoffs for diagnosing hypofibrinogenemia with kaolin thrombelastography (TEG) have not been established. We hypothesized that kaolin kaolin-TEG parameters, such as kinetic time (K-time), α-angle, and maximum amplitude (MA), would accurately diagnose hypofibrinogenemia (fibrinogen <200 mg/dL) and severe hypofibrinogenemia (fibrinogen <100 mg/dL)., Methods: Adult trauma patients (injury severity score >15) presenting to our trauma center between October 2015 and October 2017 were identified retrospectively. All patients had a traditional plasma fibrinogen measurement and kaolin-TEG performed within 15 minutes of each other and within 1 hour of admission. Some patients had additional measurements after. Receiver operating characteristic (ROC) curve analysis was performed to evaluate whether K-time, α-angle, and MA could diagnose hypofibrinogenemia and severe hypofibrinogenemia. Area under the ROC curve (AUROC) was calculated for each TEG parameter with a bootstrapped 99% confidence interval (CI). Further, ROC analysis was used to estimate ideal cutoffs for diagnosing hypofibrinogenemia and severe hypofibrinogenemia by maximizing sensitivity and specificity. In addition, likelihood ratios were also calculated for different TEG variable cutoffs to diagnose hypofibrinogenemia and severe hypofibrinogenemia., Results: Seven hundred twenty-two pairs of TEGs and traditional plasma fibrinogen measurements were performed in 623 patients with 99 patients having additional pairs of tests after the first hour. MA (AUROC = 0.84) and K-time (AUROC = 0.83) better diagnosed hypofibrinogenemia than α-angle (AUROC = 0.8; P = .03 and P < .001 for AUROC comparisons, respectively). AUROCs statistically improved for each parameter when severe hypofibrinogenemia was modeled as the outcome (P < .001). No differences were found between parameters for diagnosing severe hypofibrinogenemia (P > .05 for all comparisons). The estimated optimal cutoffs for diagnosing hypofibrinogenemia were 1.5 minutes for K-time (95% CI, 1.4-1.6), 70.0° for α-angle (95% CI, 69.8-71.0), and 60.9 mm for MA (95% CI, 59.2-61.8). The estimated optimal cutoffs for diagnosing severe hypofibrinogenemia were 2.4 minutes for K-time (95% CI, 1.7-2.8), 60.6° for α-angle (95% CI, 57.2-67.3), and 51.2 mm for MA (95% CI, 49.0-56.2). Currently recommended K-time and α-angle cutoffs from the American College of Surgeons had low sensitivity for diagnosing hypofibrinogenemia (3%-29%), but sensitivity improved to 74% when using optimal cutoffs., Conclusions: Kaolin-TEG parameters can accurately diagnose hypofibrinogenemia and severe hypofibrinogenemia in trauma patients. Currently recommended cutoffs for the treatment of hypofibrinogenemia are skewed toward high specificity and low sensitivity. Many patients are likely to be undertreated for hypofibrinogenemia using current national guidelines.

Achieving hemostasis after complex cardiovascular and transplant surgical procedures is one of the greatest challenges anesthesiologists face. Preoperative coagulation disturbances due to underlying disease or antithrombotic therapy are common, and they are worsened by intraoperative blood loss and fluid replacement. The coagulation reactions in vivo are incredibly complex interactions among blood cells, proteins, and vasculature, standing in sharp contrast to rather simple treatment options including transfusion of platelets, plasma, and cryoprecipitate. The long turnaround time of laboratory coagulation testing, and intraoperative heparin use also make timely coagulation assessment difficult during cardiopulmonary bypass, and thus, hemostatic components are often empirically ordered and administered without knowing their actual need or efficacy. However, increasing clinical experience with viscoelastic coagulation testing in cardiac and transplant anesthesia has introduced a paradigm shift, enabling clinicians to obtain clinically relevant coagulation data in a timely fashion and to treat a specific element of coagulation that is dysfunctional. Viscoelastic coagulation testing may facilitate an optimal use of blood components and other hemostatic agents, but its application is often practice specific (ie, type of surgery), and there are technical limitations and learning curves. The aims of this review are thus to summarize recent clinical data on viscoelastic coagulation testing and to provide practical examples of its use in complex cardiac surgical and transplant cases., (Copyright © 2016. Published by Elsevier Inc.)

Prolonged prothrombin time (PT) and its ratio are routinely used for the assessment of candidates for liver transplantation (LT), but intraoperative coagulation management of transfusion is hindered by its long turnaround time. Abnormal reaction time (R time) on thromboelastography (TEG) or clotting time (CT) of rotational thromboelastometry (ROTEM) are presumably an alternative, but there is a paucity of clinical data on abnormal R time/CT values compared to PT during LT. After receiving institutional review board approval and informed consent, we obtained blood samples from 36 LT patients for international normalized ratio (INR), factor (F) X level, and viscoelastic tests (EXTEM/INTEM and kaolin/rapid TEG) at baseline and 30 minutes after graft reperfusion. Receiver operating characteristic (ROC) curves were calculated for INR > 1.5 and viscoelastic R time/CT thresholds to assess the ability to diagnose FX deficiency at the moderate (<50%) or severe (<35%) level. The FX deficiency data were calculated using cutoff values of INR (>1.5) and abnormal R time/CT for TEG and ROTEM. Tissue factor (TF)-activated INR and EXTEM-CT performed well in diagnosing FX below 50%, but rapid TEG with combined TF and kaolin activators failed. Improved performance of INTEM-CT in diagnosing FX below 35% underlies multifactorial deficiency involving both intrinsic and common pathways. In conclusion, the differences among different viscoelastic tests and clinical situations should be carefully considered when they are used to guide transfusion during LT., (© 2015 American Association for the Study of Liver Diseases.)

Unlike kaolin thrombelastography (k-TEG), the clinical utility of rapid thrombelastography (r-TEG) and functional fibrinogen thrombelastography (FF-TEG) has not been tested in liver transplantation (LT). These thrombelastography techniques were simultaneously performed at the time of the skin incision (the baseline) and 30 minutes after graft reperfusion (III + 30) for 27 consecutive adult LT patients. k-TEG and r-TEG parameters [alpha angle (α) and maximum amplitude of the clot (MA)] were compared in addition to the assay time. Estimated FF-TEG fibrinogen levels were compared with plasma fibrinogen measurements. At the baseline, the values of Spearman's correlation coefficient (r) between k-TEG and r-TEG were moderate for α (r = 0.40, P = 0.06) and strong for MA (r = 0.90, P < 0.01). At III + 30, r was 0.46 (P < 0.05) for α and 0.80 (P < 0.01) for MA. The average time required to measure MA via r-TEG was decreased in comparison with k-TEG [from 29.7 to 21.6 minutes at the baseline (a 22% reduction) and from 29.6 to 22.9 minutes at III + 30 (a 23% reduction)]. FF-TEG correlated strongly with the plasma fibrinogen level at the baseline (r = 0.90, P < 0.01); however, FF-TEG overestimated the fibrinogen level at III + 30 (r = 0.58, P = 0.01). In conclusion, in adult LT, r-TEG correlates with k-TEG strongly for MA but only moderately for α. FF-TEG estimates the plasma fibrinogen level well at the baseline; however, it must be interpreted with caution because of its overestimation after graft reperfusion when the plasma fibrinogen level often decreases to less than 100 mg/dL., (© 2014 American Association for the Study of Liver Diseases.)

The value of thrombelastography (TEG) and thromboelastometry (ROTEM) to improve perioperative hemostasis is under debate. We aimed to assess the effects of TEG- or ROTEM-guided therapy in patients undergoing cardiac surgery on the use of allogeneic blood products. We analyzed 12 trials including 6835 patients, 749 of them included in 7 randomized controlled trials (RCTs). We collected data on the amount of transfused allogeneic blood products and on the proportion of patients who received allogeneic blood products or coagulation factor concentrates. Including all trials, the odds ratios (ORs) for transfusion of red blood cell (RBC) concentrates, fresh-frozen plasma (FFP), and platelets were 0.62 (95% confidence interval [CI], 0.56-0.69; P<.001), 0.28 (95% CI, 0.24-0.33; P<.001), and 0.55 (95% CI, 0.49-0.62; P<.001), respectively. However, more than 50% of the patients in this analysis were derived from one retrospective study. Including RCTs only, the ORs for transfusion of RBC, FFP, and platelets were 0.54 (95% CI, 0.38-0.77; P<.001), 0.36 (95% CI, 0.25-0.53; P<.001), and 0.57 (95% CI, 0.39-0.81; P=.002), respectively. The use of coagulation factor concentrates was reported in 6 studies, 2 of them were RCTs. The ORs for the infusion of fibrinogen and prothrombin complex concentrate were 1.56 (95% CI, 1.29-1.87; P<.001) and 1.74 (95% CI, 1.40-2.18; P<.001), respectively. However, frequencies and amounts were similar in the intervention and control group in the 2 RCTs. It is presumed that TEG- or ROTEM-guided hemostatic management reduces the proportion of patients undergoing cardiac surgery transfused with RBC, FFP, and platelets. This presumption is strongly supported by similar ORs found in the analysis including RCTs only. Patient blood management based on the transfusion triggers by TEG or ROTEM appears to be more restrictive than the one based on conventional laboratory testing. However, evidence for improved clinical outcome is limited at this time., (© 2013.)

Background: Rotational thromboelastometry (ROTEM®)-based FIBTEM is used perioperatively to assess the extent of fibrin polymerization in whole blood. In FIBTEM, cytochalasin D eliminates the contribution of platelets to whole blood clotting, but changing levels in fibrin(ogen) and erythrocytes may differently affect clot formation. Because dynamic changes of hematocrit are not reflected in plasma fibrinogen measurements, we hypothesized that the lack of erythrocytes in isolated plasma measurements would affect the relationship between the Clauss method and whole blood-based FIBTEM during cardiac surgery. Therefore, in the current study we investigated the influence of perioperative hematocrit changes on FIBTEM and fibrinogen measurements., Methods: Blood samples were collected from 6 consenting healthy volunteers. FIBTEM tests were run before and after serial in vitro dilutions of whole blood with saline or autologous plasma (5:1, 2:1, and 1:1 v/v). We then evaluated the relationship between FIBTEM-maximal clot firmness (MCF) and the Clauss fibrinogen method in relation to hematocrit values before and after cardiac surgery. Pearson correlation coefficients were determined between laboratory test results and ROTEM variables., Results: Upon in vitro hematocrit reduction, FIBTEM-MCF was progressively decreased depending on the extent of saline dilution, but it was increased by 31% after 1:1 volume replacement with autologous plasma (P < 0.05). In samples from cardiac patients (150 measurements in 50 patients), the overall correlation coefficient between FIBTEM-MCF and plasma fibrinogen was 0.80 (P < 0.001). In hemodiluted blood samples (during surgery or at intensive care unit), FIBTEM-MCF 10 mm corresponded to plasma fibrinogen levels of 200 mg/dL. In the subgroup analysis (n = 50 each), according to hematocrit levels (<25%, ≥25% to 30%, ≥30%), plasma fibrinogen levels of 200 mg/dL corresponded to 11 mm, 10 mm, and 8 mm of FIBTEM-MCF, respectively. The correlation between FIBTEM-MCF and plasma fibrinogen was higher at lower hematocrit (<25%) than at higher hematocrit (>30%) (r = 0.88 and 0.67, respectively)., Conclusions: Perioperative changes in hematocrit affect the correlation between plasma fibrinogen levels and FIBTEM-MCF values. The higher correlation between FIBTEM-MCF and plasma fibrinogen with lower hematocrit (<25%) indicates that FIBTEM is a practical method to determine the need for fibrinogen replacement in bleeding patients who typically develop perioperative anemia.

In the recent years, thromboelastography has become a popular monitoring device for hemostasis and transfusion management in major surgery, trauma, and hemophilia. Thromboelastography is performed in whole blood and assesses the viscoelastic property of clot formation under low shear condition. Thromboelastography can be performed with a variety of activator and inhibitors at different concentrations representing the most important factors for different intervals and clot formation variables reported in multiple studies and algorithms. Furthermore, fibrinogen levels and platelet counts have a major influence on thromboelastographic variables. In addition, differences in patient populations, devices, and preanalytical conditions contribute to some conflicting findings in different studies., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: Coagulopathy after cardiopulmonary bypass (CPB) is caused by multiple perturbations in cellular and humoral elements of coagulation. A timely and comprehensive method to evaluate hemostasis would be helpful in the management of bleeding patients after CPB. The assessment of whole blood coagulation using rotation thromboelastometry (ROTEM) was compared to coagulation tests routinely performed during cardiac surgery., Study Design and Methods: Blood was obtained from 26 patients undergoing CPB surgery at baseline, at 60 minutes on CPB, at the end of CPB, and on admission to intensive care unit. ROTEM tests (extrinsically activated [EXTEM], intrinsically activated [INTEM], specific clot formation [FIBTEM]), prothrombin time, activated partial thromboplastin time, platelet (PLT) count, fibrinogen, prothrombin level, antithrombin level, and thrombin generation (TG) measurement were performed., Results: We observed strong correlations between FIBTEM-amplitude at 10 minutes (A10) and fibrinogen level (r=0.87; p<0.001) and between EXTEM/ INTEM-A10 variables and PLT count (r=0.72 and 0.67, respectively; p<0.001). Receiver operating characteristic analysis demonstrated that EXTEM-A10 and INTEM-A10 are predictive of thrombocytopenia below 80×10(9)/L (area under the curve [AUC], 0.83 and 0.82, respectively), and FIBTEM-A10 was highly predictive of fibrinogen level below 200 mg/dL (AUC, 0.96). There were only weak correlations found between TG peak and clot formation time of EXTEM or INTEM (r=0.30 and 0.29, respectively; p<0.05)., Conclusion: ROTEM variables demonstrated clinically relevant correlations with PLT counts and fibrinogen levels. In particular, decreasing levels of fibrinogen can be quickly determined (<15-20 min) using FIBTEM., (© 2011 American Association of Blood Banks.)

The REG1 system consists of factor IXa inhibitor, RB006, an aptamer-based anticoagulant and its antidote, RB007. The optimal use of RB006 can be facilitated by understanding its effect on the formation of thrombin and fibrin, and other standard tests of coagulation. Blood from consented volunteers was drawn into 3.2% citrate (9:1 v/v) and either used immediately or centrifuged to obtain platelet-poor plasma. Increasing concentrations of aptamer (6-24 microg/ml) alone or in combination with heparin (0.1 U/ml) or lepirudin (0.2 microg/ml) were added to blood and plasma samples. Activated clotting times (ACT+, low range-ACT), thrombelastometry (ROTEM) or thrombelastography (TEG) were performed in recalcified whole blood samples. Thrombin generation, prothrombin time (PT) and activated partial thromboplastin time (aPTT) were performed in plasma samples. To some samples the antidote RB007 was added to neutralise the anticoagulation activity of RB006. In all experiment the ratio of RB006 to RB007 was kept 1:2. RB006 dose-dependently prolonged aPTT and low range-ACT, but, as expected, had no effect on PT. RB006 prolonged the lag time and decreased the peak of Actin-triggered thrombin generation. Thrombin-activated TEG demonstrated that RB006 decreases the rate of clot formation. These effects were potentiated when RB006 was combined with heparin or lepirudin. In all experiments RB007 reversed the effects of RB006 back to baseline. In conclusion, RB006 inhibits thrombin generation and clot formation in a concentration-dependent manner. It is feasible to monitor RB006 and its reversal with RB007 using aPTT, low range-ACT, and thrombin-activated TEG.

Background: The binding of fibrinogen and fibrin to platelets is important in normal hemostasis. The extent of platelet-fibrin interaction can be measured as the viscoelastic strength of clot by rotational thromboelastometry (ROTEM). In this study, we investigated the effect of fibrinogen concentration and its relative contribution to overall clot strength using ROTEM., Methods: Blood samples were collected from healthy volunteers. The effects of platelet count on clot strength, determined by maximum clot elasticity (MCE), were evaluated on ROTEM using platelet-rich plasma (PRP) adjusted with autologous plasma to generate a range of platelet counts. PRPs were adjusted to 10 x 10(3) mm(-3), 50 x 10(3) mm(-3), and 100 x 10(3) mm(-3) and spiked with fibrinogen concentrates at 550 and 780 mg/dL. The effect of fibrin polymerization on clot strength, independent of platelet attachment, was analyzed by the cytochalasin D-modified thromboelastometry (FIBTEM) method. Additional retrospective analysis of clot strength (MCE) in two groups of thrombocytopenic patients was conducted., Results: Clot strength (MCE) decreased at a platelet count below 100 x 10(3) mm(-3), whereas increases in MCE peaked and reached a plateau at platelet counts from 400 x 10(3) mm(-3). Increasing fibrinogen concentrations in PRP increased clot strength in a concentration-dependent manner, even at low platelet counts (10 x 10(3) mm(-3)). The positive correlation between clot strength and plasma fibrinogen level was also confirmed in the analysis of the data obtained from 904 thrombocytopenic patients., Conclusions: These in vitro and clinical data indicate that the clot strength increases in a fibrinogen concentration-dependent manner independent of platelet count, when analyzed by ROTEM. The maintenance of fibrinogen concentration is critical in the presence of thrombocytopenia. EXTEM (extrinsic activation) and FIBTEM may be useful in guiding fibrinogen repletion therapy.

For intravenous anticoagulation, heparin has been the mainstay drug, but its use may be contraindicated in heparin-induced thrombocytopenia and thrombosis. Heparin alternatives including direct thrombin inhibitors are available, but clotting assays (e.g. partial thromboplastin time) measure the time required to form fibrin gel when only a small amount of thrombin is generated. It was hypothesized that the extent of thrombin inhibition varies among inhibitors, and thrombin-activated thrombelastography would provide useful data on therapeutic responses to thrombin inhibitors. Thrombin was added (0-100 nmol/l final concentration) to nonrecalcified whole blood to evaluate clot formation on thrombelastography. Effects of direct thrombin inhibitors (argatroban 3.75 microg/ml, bivalirudin 15 microg/ml, and lepirudin 3.0 microg/ml), and heparin cofactor II activator and dermatan disulfate (20 microg/ml) were evaluated in the presence of 100 nmol/l thrombin. The interactions of thrombin and respective inhibitors were also compared by fluorogenic thrombin substrate cleavage. Increasing concentrations of thrombin progressively shortened the lag time and increased viscoelasticity on thrombelastography. Only 20 nmol/l thrombin caused instantaneous clotting, but maximal viscoelastic force was obtained at 50-100 nmol/l thrombin. All thrombin inhibitors prolonged the lag time (lepirudin > bivalirudin > argatroban = dermatan disulfate), but full recovery of thrombelastography viscoelasticity was observed with argatroban and bivalirudin. Lepirudin abrogated clotting, and dermatan disulfate suppressed clot development on thrombelastography. Thrombin substrate cleavage was observed only for bivalirudin, and heparin cofactor II without dermatan disulfate. The modified thrombelastography technique using nonrecalcified whole blood may be useful in evaluating the extent and reversibility of thrombin blockade with direct or indirect thrombin inhibitors.

Clot retraction and fibrinolysis may present as a decrease in amplitude on thrombelastography (TEG). The former represents normal or hyperactive platelet function, and the latter represents a fibrinolytic state. It is important to distinguish clot retraction from fibrinolysis because the treatment of each condition is different. To distinguish between these phenomena, we performed TEG with platelet-poor plasma (PPP) and platelet-rich plasma (PRP) with an increasing platelet count (range, 50-1200 x 10(9)/L) with or without abciximab. Maximum amplitude (MA) and the percentage decrease of amplitude at 30 and 60 min after MA were examined for each sample. Blood samples to which tissue plasminogen activator (tPA) was added served as positive controls for fibrinolysis. Morphological changes of clots and D-dimer levels were also examined. With higher platelet counts, the percentage decrease of amplitude after MA increased significantly at 30 and 60 min, but not in the abciximab samples. Morphological changes of clots have shown clot retraction in PRP, but not in PPP or PRP pretreated with abciximab. D-dimer levels increased only in samples to which tPA was added, but not in native PPP or PRP samples. In conclusion, we have shown that the decrease in amplitude at 30 and 60 min can be due to platelet-mediated clot retraction and can be attenuated by sample pretreatment with abciximab, which interrupts platelet-fibrin(ogen) binding.

We examined a novel method to detect platelet inhibition with thrombelastography (TEG). We hypothesized that this method would be suitable for monitoring the antiplatelet effects of eptifibatide (Integrilin). Whole blood from healthy volunteers was anticoagulated with 3.2% citrate or unfractionated heparin (7 IU/mL). For the platelet aggregation test, both citrate and heparinized samples were spiked with increasing concentrations of eptifibatide (0, 0.2, 0.4, 0.8, 1.6, and 4 microg/mL). Conventional kaolin TEG was performed with citrated samples, and batroxobin-modified TEG was performed with heparinized samples, which were spiked with eptifibatide at concentrations of 0, 0.4, 0.8, 1.6, 4, 8, and 24 microg/mL. Adenosine 5'-diphosphate-induced platelet aggregation was reduced to 6.4% +/- 2.9% (citrate) and 10.3% +/- 4.8% (heparin) with eptifibatide at the concentration of 4 mug/mL. The kaolin TEG showed a decrease in maximum amplitude (MA) only at the eptifibatide concentration of 24 mug/mL and no change in alpha angle, whereas with the batroxobin-based TEG, the difference in MA and alpha angle was observed at concentrations >/=0.8 microg/mL. Additionally, the time to achieve maximum MA was much shorter for batroxobin TEG than for kaolin TEG. We conclude that the batroxobin-modified TEG is a sensitive method that detects platelet inhibition induced by eptifibatide.

In this study, we characterized clot morphology with a scanning electron microscope (SEM) at time points corresponding to the commonly used thrombelastography (TEG) variables, illustrating the correlation of the physical clot formation with TEG(R) tracings. The first channel of the TEG analyzer was used to obtain the tracings of clot formation, while the sub-samples for the SEM were obtained from the second TEG channel. Different types of samples were examined, including whole blood, abciximab-treated whole blood, platelet-rich plasma (PRP), and abciximab-treated PRP. The SEM images were obtained at reaction time, different amplitudes (5-30 mm), maximum amplitude (MA), and at amplitude 60 min after MA. In the whole blood, coarse fibrin and activated platelets were observed at reaction time and fibrin strands progressively became more solid and intertwined at amplitude 10 mm and thereafter. Red blood cells were surrounded with fibrin strands at amplitude 30 mm and were tightly packed by fibrin strands at MA. In abciximab-treated whole blood, red blood cell shape was maintained at MA. The process of fibrin formation and platelet activation was also examined in PRP. Abciximab did not block platelet shape change, although the blockage of fibrin binding to platelets was shown on the TEG analyzer. In summary, we have shown structural changes of the forming clot in relation to TEG variables.

Background: Fibrinogen thromboelastometry (FIBTEM) test is clinically used for rotational thromboelastometry as a surrogate measure of fibrinogen. Elevated fibrinogen might confer protection against bleeding after major surgery. This single-center study was conducted to assess any relationship between baseline FIBTEM value and exposure to allogeneic transfusion in patients undergoing coronary artery bypass grafting (CABG).Study Design and Methods: Data were obtained retrospectively from local FIBTEM data and the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database between 2016 and 2019. Preoperative FIBTEM 10-min amplitude (A10) was categorized as low (≤ 18 mm), intermediate (19-23 mm), or high (≥24 mm). The primary outcome was any transfusion during the hospitalization, including red blood cells (RBCs), platelets, plasma, and cryoprecipitate. A multivariable regression model was used to adjust for confounders and calculate an odds ratio (OR) for any transfusion.Results: The high FIBTEM group included more female and African-American patients, as well as urgent surgery. The STS predicted risks of morbidity and mortality were greater, and anemia was most prevalent with high FIBTEM. Unadjusted blood transfusion rates were increased with high FIBTEM due to RBC transfusion, but non-RBC transfusion was highest with low FIBTEM. After adjustments, a lower OR for transfusion was associated with high FIBTEM (0.426; 95% confidence interval, 0.199-0.914) compared to low FIBTEM.Conclusion: The high FIBTEM group frequently presented with anemia and comorbidities, and received more RBCs but not non-RBC products. Postoperative blood loss was less with high FIBTEM, and after adjustments, it conferred protection against any transfusion. [ABSTRACT FROM AUTHOR]

Presents the case of patients in whom on-site thromboelastography was used to monitor blood coagulation status for perioperative coagulopathy. Medical histories of the patients; Results of laboratory examinations; Outcome of treatments.

• Behind the Eight Ball in predicting functional outcomes after ischemic stroke • Using thrombelastography outside perioperative bleeding management • TEG assay variabilities after pharmacological thrombolysis and/or EVT [ABSTRACT FROM AUTHOR]