The utility of thromboelastography in inherited and acquired bleeding disorders

Postoperative hemorrhage secondary to acquired hemophilia A

Acquired hemophilia A in postoperative patients can cause major bleeding and an accurate diagnosis is required for effective treatment. Standard treatment is costly, difficult to obtain, and takes 4 to 6 weeks to be effective. This article describes a patient successfully treated with recombinant factor VIIa, porcine factor VIII, plasmapheresis, rituximab, and high-dose corticosteroids.

Thromboelastography in pre-surgery monitoring in Hemophilia A with high inhibitor titer: case report and literature review

The development of factor VIII inhibitors (allo-antibodies) continues to be a major complication in the management of severe forms of hemophilia A, especially as far as treatment and treatment response monitoring is concerned. The need to implement a reliable laboratory assay is all the more obvious if major surgery occurs, when conventional tests (activated partial thromboplastin time APTT, prothrombin time PT, factor VIII level) are of no avail and there is a very fragile balance between bleeding and thrombosis.

We report the case of a 32 year-old patient diagnosed with severe Hemophilia A, referred to the Comprehensive Center for the Diagnosis and Treatment of Hemophilia of the Fundeni Clinical Institute for a multidisciplinary assessment in view of a total left hip arthroplasty due to aseptic necrosis of the femoral neck.

Workup showed a high inhibitor titer (>200 BU). Taking into consideration the interindividual variability of the response to bypassing agents, as well as the bleeding risk associated with a major orthopedic surgery, we used thromboelastography (TEG) to assess the patient’s response to aPCC (activated prothrombin complex concentrate) and rFVIIa (activated recombinant factor VII). The findings helped select the optimal replacement scheme to ensure perioperative hemostasis.

Platelet Disorders

After vascular injury and exposure of subendothelial matrix proteins to the intravascular space, mediators of hemostasis are triggered and allow for clot formation and restoration of vascular integrity. Platelets are the mediators of primary hemostasis, creating a platelet plug and allowing for initial cessation of bleeding. Platelet disorders, qualitative and quantitative, may result in bleeding signs and symptoms, particularly mucocutaneous bleeding such as epistaxis, bruising, petechiae, and heavy menstrual bleeding. Increasing evidence suggests that platelets have functional capabilities beyond hemostasis, but this review focuses solely on platelet hemostatic properties. Herein, normal platelet function as well as the effects of abnormal function and thrombocytopenia are reviewed.

Prediction of the haemostatic effects of bypassing therapy using comprehensive coagulation assays in emicizumab prophylaxis-treated haemophilia A patients with inhibitors

In emicizumab prophylaxis, the concomitant therapy using bypassing agents (BPAs) is required for breakthrough bleeding and invasive procedures with attention to thrombotic complications. To predict coagulant effects of BPAs in emicizumab-treated patients with haemophilia A (PwHA) with inhibitor (PwHAwI), blood samples from emicizumab-treated PwHAwI (n = 8) and PwHA without inhibitor (n = 2) in phase 1/2 and HAVEN 1 study, spiked with activated prothrombin complex concentrates (aPCC) or recombinant factor VIIa (rFVIIa) ex vivo, and blood samples from emicizumab-treated PwHAwI-receiving BPAs were analysed by Ca²⁺ -triggered rotational thromboelastometry (ROTEM) and ellagic acid/tissue factor-triggered clot waveform analysis (CWA). Spiked aPCC, corresponded to 10-100 U/kg, markedly shortened ROTEM parameters beyond the normal range, while spiked rFVIIa, corresponded to 90-270 μg/kg, shortened them within near-normal range. Each of the spiked BPA-improved adjusted maximum coagulation velocity of CWA to within or near the normal range. In blood samples at post-infusion of aPCC (44-73 U/kg) or rFVIIa (79-93 μg/kg), the parameters of both assays improved to approximately the normal range. Taken together, ex vivo results of spiking tests in ROTEM and CWA, except aPCC spiking test in ROTEM, were relatively consistent with in vivo ones, and could usefully predict the coagulant effects of concomitant bypassing therapy for emicizumab-treated PwHAwI.

Application of clot-fibrinolysis waveform analysis to assessment of in vitro effects of direct oral anticoagulants on fibrinolysis

INTRODUCTION

Acceleration of fibrinolysis by direct oral anticoagulants (DOACs) has been reported by several groups, suggesting contribution of not only anticoagulant but also fibrinolytic effects to the therapeutic efficacy. The present study aims to evaluate the usability of clot-fibrinolysis waveform analysis (CFWA) for assessment of in vitro effects of DOACs on fibrinolysis.

METHODS

The experimental conditions were optimized according to how t-PA concentrations and a time length after t-PA adjustment affect parameters of CFWA. Addition of the activated partial thromboplastin time (APTT) reagent followed by that of calcium and t-PA was done to obtain clotting and fibrinolytic reaction curves which were mathematically differentiated for CFWA (APTT-CFWA). The positive and negative modes of waveforms were defined as the direction toward fibrin generation and that toward fibrin degradation, respectively. The maximum positive and negative values (Max_p 1 and Max_n 1) correspond to the maximum coagulation velocity and the maximum fibrinolysis velocity, respectively. Plasma spiked with each of DOACs (rivaroxaban, apixaban, edoxaban, and dabigatran) was subjected to APTT-CFWA.

RESULTS

Optimization of t-PA use was based on Max_n 1. Roughly biphasic effects of rivaroxaban and dabigatran but not apixaban or edoxaban on fibrinolysis were observed through Max_n 1 and the fibrinolysis peak time, which was defined as a time length from the time when Max_p 1 (Max_p 1 time) to the time when Max_n 1 appears (Max_n 1 time).

CONCLUSION

The results suggest the usability of CFWA for assessment of DOAC effects and provide insights into relevance of anticoagulation to therapeutic efficacy and bleeding risk from the perspective of fibrinolysis.

Reference intervals for rotational thromboelastometry measurements using the ROTEM® delta device in dogs

Aims of the present study were to define reference intervals for viscoelastic analyses of canine haemostasis using the ROTEM® delta analyser, and as a secondary aspect to determine the precision (repeatability) of this method. Blood samples from 125 clinically healthy dogs were included. Measurements were performed with commercially available activating reagents (ex-tem, in-tem and kaolin solution) as well as without activation. Additional fourfold measurements were done in 3 of the normal blood samples and in 3 samples with haemostatic alterations to evaluate the precision of the method. Coefficients of variation (CVs) for most of the ROTEM variables were < 10%. Clot formation time and maximum clot elasticity showed a wide inter-individual variation in comparison with alpha angle and maximum clot firmness. A multivariate analysis on various ROTEM parameters revealed particularly a significant influence of neuter status and a significant interrelationship between the factors sex and neuter status for measurements with different activating reagents. These results reflected the fact that significant differences occurred only between intact and neutered females, but not in males. No or only occasionally significant differences were found between groups of sex, age, and size. In conclusion, CVs demonstrated that the method delivers repeatable results in canine citrated whole blood. Established reference intervals should deliver valuable orientation for the evaluation of viscoelastic properties of clotting whole blood in dogs using the ROTEM delta analyser. Neuter status in females appeared to be the most relevant influencing factor and should be considered for the interpretation of ROTEM delta test results.

Clinical controversies in anticoagulation monitoring and antithrombin supplementation for ECMO

During extracorporeal membrane oxygenation (ECMO), a delicate balance is required to titrate systemic anticoagulation to prevent thrombotic complications within the circuit and prevent bleeding in the patient. Despite focused efforts to achieve this balance, the frequency of both thrombotic and bleeding events remains high. Anticoagulation is complicated to manage in this population due to the complexities of the hemostatic system that are compounded by age-related developmental hemostatic changes, variable effects of the etiology of critical illness on hemostasis, and blood-circuit interaction. Lack of high-quality data to guide anticoagulation management in ECMO patients results in marked practice variability among centers. One aspect of anticoagulation therapy that is particularly challenging is the use of antithrombin (AT) supplementation for heparin resistance. This is especially controversial in the neonatal and pediatric population due to the baseline higher risk of bleeding in this cohort. The indication for AT supplementation is further compounded by the potential inaccuracy of the diagnosis of heparin resistance based on the standard laboratory parameters used to assess heparin effect. With concerns regarding the adverse impact of bleeding and thrombosis, clinicians and institutions are faced with making difficult, real-time decisions aimed at optimizing anticoagulation in this setting. In this clinically focused review, the authors discuss the complexities of anticoagulation monitoring and therapeutic intervention for patients on ECMO and examine the challenges surrounding AT supplementation given both the historical and current perspectives summarized in the literature on these topics.

The Utility of Thromboelastography to Guide Blood Product Transfusion

OBJECTIVES

To provide an overview of the clot viscoelastic testing technology and to describe its utility in guiding blood product transfusions.

METHODS

A case scenario will be discussed as well as interpretation of thromboelastography (TEG) tracings. In addition, literature examining the utility of viscoelastic testing in guiding patient management and blood product transfusions will be reviewed.

RESULTS

TEG/rotational thromboelastometry (ROTEM) is useful in evaluating clot kinetics in trauma and acutely bleeding patients. TEG/ROTEM parameters are reflective of values measured using standard coagulation assays; however, TEG/ROTEM parameters are more rapidly available and more costly. TEG and ROTEM are used in three main settings: cardiac surgery, liver transplantation, and trauma to assess global hemostasis and administration of blood products.

CONCLUSIONS

TEG/ROTEM can be helpful in guiding resuscitation and blood product transfusion. Several studies have demonstrated a reduction in transfusion of blood components with TEG/ROTEM; however, other studies have suggested that TEG/ROTEM is not clinically effective in guiding transfusion.

Clinical utility of viscoelastic testing (TEG and ROTEM analyzers) in the management of old and new therapies for hemophilia

Hemophilia A and B are rare inherited bleeding disorders resulting from deficiency of coagulation factors VIII and IX respectively. In the past few decades, the field of hemophilia has witnessed pivotal management challenges and therapeutic advances. Routine coagulation and factor assays, while useful in the classification of severity and treatment monitoring in hemophilia patients, have been shown to be of limited use in managing clinical presentations and outcomes. This prompted the investigation of viscoelastic studies in hemophilia care, which have established their utility in various bleeding and thrombotic states. In this review, we will discuss and critically assess the current literature highlighting the use of viscoelastic studies in various aspects of hemophilia including the determination of clinical phenotype, management of patients with inhibitors, perioperative management, and monitoring of novel agents.

Evaluation of EC50 of factor VIII as predictor of prophylaxis efficacy in patients with severe haemophilia A

Trough factor (F) VIII level is a not reliable bleeding risk indicator to predict prophylaxis efficacy in severe haemophilia A (SHA), therefore, accurate biomarkers are much needed. Thrombelastography (TEG) monitors both thrombin and clot formation addressing the global haemostatic status but its usefulness to tailor prophylaxis in haemophilia has been poorly evaluated. In this study, correspondence between individual pharmacodynamic/pharmacokinetic profile of FVIII and joint condition, physical activity and bleeding phenotype of SHA patients under prophylactic treatment was assessed. Nineteen SHA patients < 18 years old on long-term prophylaxis treatment with FVIII were studied in an observational cross-sectional study. Whole blood was withdrawn before FVIII administration and at five time-points after infusion for a TEG-based pharmacodynamic- and pharmacokinetic-study. Type of prophylaxis and joint condition at inclusion and physical activity as well as onset of treated spontaneous bleeding events in the previous two years were retrospectively assessed. Six patients had suffered at least one treated spontaneous bleeding event and were named as "bleeders". The rest were named as "non-bleeders". Only the half maximal effective concentration of FVIII (FVIII-EC50) for TEG parameters R-time, K-time and α-angle correlated with the bleeding phenotype being significantly higher in bleeders suggestive of a poorer response to FVIII. Poorer joint condition, trough FVIII levels or type of prophylaxis were not definitive predicting variables of bleeding phenotype. In conclusion, this study reveals FVIII-EC50 for the first time as a valuable biomarker to anticipate individual efficacy of prophylaxis in SHA.

Evaluation of recombinant factor VIII Fc (Eloctate) activity by thromboelastometry in a multicenter phase 3 clinical trial and correlation with bleeding phenotype

The aim of this study was to compare the hemostatic efficacy of recombinant factor VIII Fc (rFVIIIFc) (Eloctate) and Advate by ex-vivo rotation thromboelastometry (ROTEM) of whole blood and to explore potential ROTEM parameters that may be more predictive of a patient's bleeding tendency than plasma FVIII activity. Thirteen clinical sites were selected to perform ROTEM on freshly collected blood samples from 44 patients in the phase 3 study for rFVIIIFc, including 16 patients undergoing sequential pharmacokinetic assessment of Advate and rFVIIIFc. Equivalent hemostatic activity was observed for rFVIIIFc and Advate in postinfusion samples, followed by improvements for rFVIIIFc in clotting time, clot formation time and alpha angle (α) for a longer duration than Advate, consistent with the pharmacokinetic improvements reported previously for rFVIIIFc. Our study did not demonstrate a statistical correlation between a patient's ROTEM activity at baseline or at trough and the occurrence of spontaneous bleeds while on prophylactic therapy. However, an association was observed between postinfusion clotting time and the occurrence of one or more spontaneous bleeds vs. no bleeds over a follow-up period of 1 year (P = 0.003). How well a patient's whole blood clotting deficiency is corrected after a dose of FVIII may be an indicator of subsequent bleeding tendency in patients with otherwise equivalent FVIII peak and trough levels. The technical challenges of standardizing the ROTEM, largely overcome in the current study, may however preclude the use of this method for widespread assessment of global hemostasis unless additional assay controls or normalization procedures prove to be effective.

The Double Hazard of Bleeding and Thrombosis in Hemostasis From a Clinical Point of View: A Global Assessment by Rotational Thromboelastometry (ROTEM)

Hemostasis is a complex dynamic process involving bleeding and thrombosis as two end-points. Conventional coagulation tests which are measured in plasma examine only isolated portions of the coagulation cascade, thereby giving no information on important interactions essential to the clinical evaluation of hemostatic function. Thromboelastography (TEG), originally described in 1948 has improved over the decades and become a valuable tool of coagulation testing because of the limitations of standard coagulation tests. TEG is a technique that provides data about the entire coagulation system, from the beginning of clot formation to fibrinolysis, involving both cellular and plasma components of hemostasis. Rotational thromboelastometry (ROTEM) which evolved from TEG technology overcome several limitations of classical TEG while maintaining a good correlation with conventional TEG determination. ROTEM analyses are useful for rapid assessment of global clotting function in various clinical situations including liver transplantation, cardiac surgery, obstetrics, trauma, hemophilia and idiopathic thrombocytopenic purpura. ROTEM has been also reported to be useful in identifying various hypercoagulable conditions including major surgery, malignancy, Behcet’s disease and apheresis. Further developments in ROTEM based transfusion strategies may also reduce transfusion requirements and improve clinical outcomes by optimizing the administration of blood components. This is a literature review of ROTEM including its technique, interpretation and specially clinical applications in different scenarios of bleeding and thrombotic disorders.

Thrombocytopenia after liver transplantation: Should we care?

Transient thrombocytopenia is a common phenomenon after liver transplantation. After liver transplantation (LT), platelet count decreases and reaches a nadir on postoperative days 3-5, with an average reduction in platelet counts of 60%; platelet count recovers to preoperative levels approximately two weeks after LT. The putative mechanisms include haemodilution, decreased platelet production, increased sequestration, medications, infections, thrombosis, or combination of these processes. However, the precise mechanisms remain unclear. The role of platelets in liver transplantation has been highlighted in recent years, and particular attention has been given to their effects beyond hemostasis and thrombosis. Previous studies have demonstrated that perioperative thrombocytopenia causes poor graft regeneration, increases the incidence of postoperative morbidity, and deteriorates the graft and decreases patient survival in both the short and long term after liver transplantation. Platelet therapies to increase perioperative platelet counts, such as thrombopoietin, thrombopoietin receptor agonist, platelet transfusion, splenectomy, and intravenous immunoglobulin treatment might have a potential for improving graft survival, however clinical trials are lacking. Further studies are warranted to detect direct evidence on whether thrombocytopenia is the cause or result of poor-graft function and postoperative complications, and to determine who needs platelet therapies in order to prevent postoperative complications and thus improve post-transplant outcomes.

The use of viscoelastic haemostatic assays in non-cardiac surgical settings: a systematic review and meta-analysis

BACKGROUND

Thrombelastography (TEG) and rotational thromboelastometry (ROTEM) are viscoelastic haemostatic assays (VHA) which exploit the elastic properties of clotting blood. The aim of this systematic review and meta-analysis was to evaluate the usefulness of these tests in bleeding patients outside the cardiac surgical setting.

MATERIALS AND METHODS

We searched the Cochrane Library, MEDLINE, EMBASE and SCOPUS. We also searched clinical trial registries for ongoing and unpublished studies, and checked reference lists to identify additional studies.

RESULTS

We found 4 randomised controlled trials (RCTs) that met our inclusion criteria with a total of 229 participants. The sample size was small (from 28 to 111 patients) and the follow-up periods very heterogenous (from 4 weeks to 3 years). Pooled data from the 3 trials reporting on mortality (199 participants) do not show any effect of the use of TEG on mortality as compared to standard monitoring (based on the average treatment effect from a fixed-effects model): Risk Ratio (RR) 0.71; 95% Confidence Interval (CI): 0.43 to 1.16. Likewise, the use of VHA does not reduce the need for red blood cells (mean difference -0.64; 95% CI: -1.51 to 0.23), platelet concentrates (mean difference -1.12; 95% CI: -3.25 to 1.02), and fresh frozen plasma (mean difference -0.91; 95% CI: -2.02 to 0.19) transfusion. The evidence on mortality and other outcomes was uncertain (very low-certainty evidence, down-graded due to risk of biases, imprecision, and inconsistency).

CONCLUSIONS

Overall, the certainty of the evidence provided by the trials was too low for us to be certain of the benefits and harms of viscoelastic haemostatic assay in non-cardiac surgical settings. More, larger, and better-designed RCTs should be carried out in this area.

First report of real-time monitoring of coagulation function potential and IgG subtype of anti-FVIII autoantibodies in a child with acquired hemophilia A associated with streptococcal infection and amoxicillin

We describe an 8-year-old boy with acquired hemophilia A (AHA) associated with streptococcal infection and amoxicillin. Laboratory data revealed low factor VIII activity (FVIII:C, 1.5 IU/dl), and FVIII inhibitor (15.9 BU/ml). Comprehensive coagulation function assays, including rotation thromboelastometry (ROTEM^®), revealed a markedly prolonged clotting time. Thrombin and plasmin generation (TG/PG) appeared to be moderately impaired. The inhibitor epitope of his anti-FVIII autoantibody recognized light and heavy chains. He was treated with Novoseven^® and prednisolone, resulting in rapid improvement. ROTEM showed the return of coagulation time to normal level on day 20, and TG gradually improved. PG was moderately reduced in the clinical early phase, but improved at day 20. The patient's IgG subtype was IgG₄ at onset. IgG₁ was transiently positive on day 20, but negative on day 46. FVIII inhibitor gradually decreased and was completely absent after day 46, along with the elevated FVIII:C. IgG4 was again elevated on day 83, followed by a rapid decrease, indicative of the presence of non-neutralizing antibody, which remains currently undetected. We for the first time report changes in comprehensive coagulation function and IgG subtype of anti-FVIII antibody in a rare pediatric case of AHA.

Role of red blood cells in the anemia-associated bleeding under high shear conditions

BACKGROUND

Red blood cells (RBCs) contribute to hemostasis under blood-flow, and anemia might contribute to a hemorrhagic diathesis. The majority of current laboratory techniques to assess hemostasis do not consider the effects of RBCs. An assay to determine the role of RBCs in hemostasis could be beneficial for clinical management.

OBJECTIVES

To investigate the influence of RBCs in hemostasis.

METHODS

Hemostasis was investigated using a novel microchip flow-chamber system (T-TAS^® ) in an anemic patient with von Willebrand disease. Subsequently, the effects of RBCs in total thrombus analysis system (T-TAS) were examined using reconstituted whole blood at various hematocrit levels.

RESULTS

In vivo: When the patient was anemic and demonstrated persisted hemorrhagic symptoms despite the maintained adequate von Willebrand factor ristocetin cofactor activity levels, thrombus formation determined by T-TAS was delayed. However, transfusions of RBCs resolved bleeding symptom and, accordingly, the thrombus formation in T-TAS improved. In vitro: Thrombus formation determined by T-TAS at 1000 s^-1 was dose-dependent on hematocrit (the time to reach 10 kPa (T₁₀ ): 10.0 ± 0, 9.5 ± 1.4, 6.7 ± 2.4, 2.8 ± 1.6 min at hematocrits of 0%, 12.5%, 25% and 50%, respectively). Markedly defective thrombus formation (T₁₀ >10 min) was confirmed at a hematocrit <25% at 2000 s^-1 .

CONCLUSION

Red blood cells play an essential role in hemostasis under high shear, and RBC transfusions could be effective for refractory bleeding in patients with anemia. T-TAS measurements appear to reflect the hemostatic consequences of diminished red cell numbers under blood-flow, and could provide a valuable means for monitoring patients.

Tissue factor-dependent coagulation activation by heme: A thromboelastometry study

Heme has been characterized as potent trigger of inflammation. In hemostasis, although heme has been shown to both induce and inhibit different compartments of hemostasis, its net effect on the hemostatic balance, and the biological relevance of these effects remain to be determined. Herein we evaluated the effect of heme on hemostasis using a global assay able to generate clinically relevant data in several other complex hemostatic diseases. Citrated whole blood samples from healthy participants were stimulated by heme or vehicle and incubated for 4h at 37°C. Rotational thromboelastometry was immediately performed. The participation of tissue factor in coagulation activation was evaluated using inhibitory antibody. Heme was able of inducing ex vivo coagulation activation in whole blood, affecting predominantly parameters associated with the initial phases of clot formation. This activation effect was at least partially dependent on hematopoietic tissue factor, since the effects of heme were partially abrogated by the inhibition of human tissue factor. In conclusion, using a global hemostasis assay, our study confirmed that heme is able to activate coagulation in whole blood, in a tissue factor-dependent way. These findings could explain the disturbance in hemostatic balance observed in conditions associated with the release of heme such as sickle cell disease.

Rare bleeding disorders-old diseases in the era of novel options for therapy

Rare diseases are defined as life-threatening or chronically debilitating diseases with a prevalence of less than one per 2000 according to the European Union or one per 1250 according to the USA. Congenital rare bleeding disorders RBD are reported in most populations, with incidence varying from 1 in 5000 (Hemophilia A), 1:30,000 (Hemophilia B) to much rarer (1:500,000 for FVII deficiency, 1-3 million for Prothrombin or FXIII deficiency). Acquired Hemophilia A is also a rare bleeding disorder with estimated frequency of 1 in million. Most RBDs are inherited as autosomal recessive (AR); however, heterozygous carriers with varying degrees of corresponding factor deficiency may render an unpredictable propensity for bleeding. In patients with bleeding symptoms, laboratory assessment and especially molecular techniques currently enable accurate diagnosis and may provide tools for prenatal and family counseling. Currently hemostasis control is mainly based upon replacement of the missing coagulation factors (unless presence of inhibitors renders it impossible), however future gene therapy and disruptive, non-replacement alternatives may be promising for patients with RBD.

Quality Assessment of Established and Emerging Blood Components for Transfusion

Blood is donated either as whole blood, with subsequent component processing, or through the use of apheresis devices that extract one or more components and return the rest of the donation to the donor. Blood component therapy supplanted whole blood transfusion in industrialized countries in the middle of the twentieth century and remains the standard of care for the majority of patients receiving a transfusion. Traditionally, blood has been processed into three main blood products: red blood cell concentrates; platelet concentrates; and transfusable plasma. Ensuring that these products are of high quality and that they deliver their intended benefits to patients throughout their shelf-life is a complex task. Further complexity has been added with the development of products stored under nonstandard conditions or subjected to additional manufacturing steps (e.g., cryopreserved platelets, irradiated red cells, and lyophilized plasma). Here we review established and emerging methodologies for assessing blood product quality and address controversies and uncertainties in this thriving and active field of investigation.