Thromboelastometry versus free-oscillation rheometry and enoxaparin versus tinzaparin: an in-vitro study comparing two viscoelastic haemostatic tests' dose-responses to two low molecular weight heparins at the time of withdrawing epidural catheters from ten patients after major surgery

Self-Reporting Theranostic: Nano Tool for Arterial Thrombosis

Arterial thrombosis (AT) originates through platelet-mediated thrombus formation in the blood vessel and can lead to heart attack, stroke, and peripheral vascular diseases. Restricting the thrombus growth and its simultaneous monitoring by visualisation is an unmet clinical need for a better AT prognosis. As a proof-of-concept, we have engineered a nanoparticle-based theranostic (combined therapy and monitoring) platform that has the potential to monitor and restrain the growth of a thrombus concurrently. The theranostic nanotool is fabricated using biocompatible super-paramagnetic iron oxide nanoparticles (SPIONs) as a core module tethered with the anti-platelet agent Abciximab (ReoPro) on its surface. Our in vitro feasibility results indicate that ReoPro-conjugated SPIONS (Tx@ReoPro) can effectively prevent thrombus growth by inhibiting fibrinogen receptors (GPIIbIIIa) on the platelet surface, and simultaneously, it can also be visible through non-invasive magnetic resonance imaging (MRI) for potential reporting of the real-time thrombus status.

In vitro Effect of Dalteparin and Argatroban on Hemostasis in Critically Ill Sepsis Patients with New-Onset Thrombocytopenia

Thrombocytopenia is common among critically ill sepsis patients, while they also hold an increased risk for thromboembolic events. Thus, the choice of anticoagulant prophylaxis for this patient population is challenging. We investigated the in vitro effect of low-molecular-weight heparin (dalteparin) and direct thrombin inhibitor (argatroban) on the hemostasis in blood from sepsis patients with new-onset thrombocytopenia. Thrombocytopenia was defined as a platelet count drop of ≥30% and/or from >100 × 10 ⁹ /L to 30 to 100 × 10 ⁹ /L within 24 hours prior to inclusion. We included five healthy individuals and ten patients. Analyses of thrombin generation (Calibrated Automated Thrombogram), thrombin-antithrombin (TAT) complex levels, prothrombin fragment 1+2 (F1+2), and rotational thromboelastometry (ROTEM) were performed. Based on dose-response relationships investigated in healthy blood, patient samples were spiked with prophylactic (0.25 IU/mL) and therapeutic (0.75 IU/mL) dalteparin and low (0.25 µg/mL) and high (0.50 µg/mL) argatroban concentrations, each with a sample without anticoagulant. In patients, the endogenous thrombin potential was markedly lower in therapeutic dalteparin samples than in samples without anticoagulant [median (range): 29 (0-388) vs. 795 (98-2121) nM × min]. In high argatroban concentration samples, thrombin lag time was longer than in samples without anticoagulant [median (range): 15.5 (10.5-20.2) versus 5.3 (2.8-7.3) min]. Dalteparin and argatroban both increased clotting time but did not affect maximum clot firmness in the ROTEM INTEM assay. Six patients had elevated TAT and eight patients had elevated F1 + 2. In conclusion, dalteparin mainly affected the amount of thrombin generated and argatroban delayed clot initiation in critically ill sepsis patients with new-onset thrombocytopenia. Neither anticoagulant affected clot strength.

Impact of surface coating and systemic anticoagulants on hemostasis and inflammation in a human whole blood model

BACKGROUND

Surface compatibility with blood is critical both for scientific investigations on hemostasis and clinical applications. Regarding in vitro and ex vivo investigations, minimal alteration in physiological hemostasis is of particular importance to draw reliable conclusions on the human coagulation system. At the same time, artificial coagulation activation must be avoided, which is relevant for the patient, for example to prevent stent graft occlusion. The aim was to evaluate the advantages and disadvantages of antithrombotic and antifouling surface coatings in the context of their suitability for ex vivo incubation and the study of coagulation properties.

METHODS

We investigated the impact of different protocols for surface coating of synthetic material and different anticoagulants on hemostasis and platelet activation in ex vivo human whole blood. Blood samples from healthy donors were incubated in coated microtubes on a rotating wheel at 37°C. Two protocols for surface coating were analyzed for hemostatic parameters and metabolic status, a heparin-based coating (CHC, Corline Heparin Conjugate) without further anticoagulation and a passivating coating (MPC, 2-methacryloyloxethyl phosphorylcholine) with added anticoagulants (enoxaparin, ENOX; or fondaparinux, FPX). Employing the MPC-based coating, the anticoagulants enoxaparin and fondaparinux were compared regarding their differential effects on plasmatic coagulation by thrombelastometry and on platelet activation by flowcytometry and platelet function assays.

RESULTS

Using the CHC coating, significant coagulation cascade activation was observed, whereas parameters remained mostly unchanged with MPC-based protocols. Extended incubation caused significantly elevated levels of the soluble membrane attack complex. Neither ENOX nor FPX caused a relevant impairment of platelet function or activation capacity and thrombelastometric parameters remained unchanged with both protocols. For translational purposes, we additionally modeled endotoxemia with the MPC-based protocols by incubating with lipopolysaccharide plus/minus thrombin. While coagulation parameters remained unchanged, elevated Interleukin 8 and Matrix Metalloproteinase 9 demonstrated preserved immune cell responsiveness.

CONCLUSIONS

The MPC-based protocols demonstrated better hemocompatibility compared to CHC, and ENOX and FPX proved useful for additional anticoagulation. Furthermore, this simple-to-use whole blood model may be useful for experimental analyses of the early coagulatory and immunological response without decalcification.

"In Less than No Time": Feasibility of Rotational Thromboelastometry to Detect Anticoagulant Drugs Activity and to Guide Reversal Therapy

Anticoagulant drugs (i.e., unfractionated heparin, low-molecular-weight heparins, vitamin K antagonists, and direct oral anticoagulants) are widely employed in preventing and treating venous thromboembolism (VTE), in preventing arterial thromboembolism in nonvalvular atrial fibrillation (NVAF), and in treating acute coronary diseases early. In certain situations, such as bleeding, urgent invasive procedures, and surgical settings, the evaluation of anticoagulant levels and the monitoring of reversal therapy appear essential. Standard coagulation tests (i.e., activated partial thromboplastin time (aPTT) and prothrombin time (PT)) can be normal, and the turnaround time can be long. While the role of viscoelastic hemostatic assays (VHAs), such as rotational thromboelastometry (ROTEM), has successfully increased over the years in the management of bleeding and thrombotic complications, its usefulness in detecting anticoagulants and their reversal still appears unclear.

Evaluation of health outcomes after the implementation of rotational thromboelastometry in patients undergoing cardiac surgery

BACKGROUND

Viscoelastic tests (rotational thromboelastometry, ROTEM^®), together with the implementation of a specific algorithm for coagulation management in cardiac surgery, enable perioperative coagulopathy to be better controlled.

METHODS

Retrospective cohort study including 675 patients who underwent cardiac surgery with cardiopulmonary bypass. The incidence of allogeneic blood transfusions and clinical postoperative complications were analyzed before and after ROTEM^® implementation.

RESULTS

Following viscoelastic testing and the implementation of a specific algorithm for coagulation management, the incidence of any allogeneic blood transfusion decreased (41.4% vs 31.9%, p = .026) during the perioperative period. In the group monitored with ROTEM^®, decreased incidence of transfusion was observed for packed red blood cells (31.3% vs 19.8%, p = .002), fresh frozen plasma (9.8% vs 3.8%, p = .008), prothrombin complex concentrate administration (0.9% vs 0.3%, p = .599) and activated recombinant factor VII (0.3% vs 0.0%, p = .603). Increased incidence was observed for platelet transfusion (4.8% vs 6.8%, p = .530) and fibrinogen concentrate (0.9% vs 3.5%, p = .066), tranexamic acid (0.0% vs 0.6%, p = .370) and protamine administration (0.6% vs 0.9%, p = .908). Similar results were observed in the postoperative period, but with a decreased incidence of platelet transfusion (4.8% vs 3.8%, p = .813). In addition, statistically significant reductions were detected in the incidence of postoperative bleeding (9.5% vs 5.3%, p = .037), surgical reexploration (6.0% vs 2.9%, p = .035), and length of Intensive Care Unit (ICU) stay (6.0 days vs 5.3 days, p = .026).

CONCLUSIONS

The monitoring of hemostasis by ROTEM^® in cardiac surgery, was associated with decreased incidence of allogeneic blood transfusion, clinical hematologic postoperative complications and lengths of ICU stay.

Thromboelastometry demonstrates endogenous coagulation activation in nonsevere and severe COVID-19 patients and has applicability as a decision algorithm for intervention

In patients with severe forms of COVID-19, thromboelastometry has been reported to display a hypercoagulant pattern. However, an algorithm to differentiate severe COVID-19 patients from nonsevere patients and healthy controls based on thromboelastometry parameters has not been developed. Forty-one patients over 18 years of age with positive qRT-PCR for SARS-CoV-2 were classified according to the severity of the disease: nonsevere (NS, n = 20) or severe (S, n = 21). A healthy control (HC, n = 9) group was also examined. Blood samples from all participants were tested by extrinsic (EXTEM), intrinsic (INTEM), non-activated (NATEM) and functional assessment of fibrinogen (FIBTEM) assays of thromboelastometry. The thrombodynamic potential index (TPI) was also calculated. Severe COVID-19 patients exhibited a thromboelastometry profile with clear hypercoagulability, which was significantly different from the NS and HC groups. Nonsevere COVID-19 cases showed a trend to thrombotic pole. The NATEM test suggested that nonsevere and severe COVID-19 patients presented endogenous coagulation activation (reduced clotting time and clot formation time). TPI data were significantly different between the NS and S groups. The maximum clot firmness profile obtained by FIBTEM showed moderate/elevated accuracy to differentiate severe patients from NS and HC. A decision tree algorithm based on the FIBTEM-MCF profile was proposed to differentiate S from HC and NS. Thromboelastometric parameters are a useful tool to differentiate the coagulation profile of nonsevere and severe COVID-19 patients for therapeutic intervention purposes.

Rotational Thromboelastometry Findings Are Associated with Symptomatic Venous Thromboembolic Complications after Hip Fracture Surgery

BACKGROUND

Venous thromboembolism is a common complication after hip fractures. However, there are no reliable laboratory assays to identify patients at risk for venous thromboembolic (VTE) events after major orthopaedic surgery.

QUESTION/PURPOSES

(1) Are rotational thromboelastometry (ROTEM) findings associated with the presence or development of symptomatic VTE after hip fracture surgery? (2) Were any other patient factors associated with the presence or development of symptomatic VTE after hip fracture surgery? (3) Which ROTEM parameters were the most accurate in terms of detecting the association of hypercoagulability with symptomatic VTE?

METHODS

This retrospective study was conducted over a 13-month period. In all, 354 patients with femoral neck and peritrochanteric fractures who underwent hip hemiarthoplasty or cephallomedullary nailing were assessed for eligibility. Of those, 99% (349 of 354) were considered eligible for the study, 1% (3 of 354) of patients were excluded due to coagulation disorders, and another 1% (2 of 354) were excluded because they died before the postoperative ROTEM analysis. An additional 4% (13 of 354) of patients were lost before the minimum study follow-up of 3 months, leaving 95% (336 of 354) for analysis. A ROTEM analysis was performed in all patients at the time of their hospital admission, within hours of the injury, and on the second postoperative day. The patients were monitored for the development of symptoms indicative of VTE, and the gold standard tests for diagnosing VTE, such as CT pulmonary angiography or vascular ultrasound, were selectively performed only in symptomatic patients and not routinely in all patients. Therefore, this study evaluates the association of ROTEM with only clinically evident VTE events and not with all VTE events. ROTEM results did not affect the clinical surveillance of the study group and the decision for further work up. To determine whether ROTEM findings were associated with the presence or development of symptomatic VTE, ROTEM parameters were compared between patients with and without symptomatic VTE. To establish whether any other patient factors were associated with the presence or development of symptomatic VTE after hip fracture surgery, clinical parameters and conventional laboratory values were also compared between patients with and without symptomatic VTE. Finally, to determine which ROTEM parameters were the most accurate in terms of detecting the association of hypercoagulability with symptomatic VTE, the area under the curve (AUC) for certain cut off values of ROTEM parameters was calculated.

RESULTS

We found several abnormal ROTEM values to be associated with the presence or development of symptomatic VTE. The preoperative maximum clot firmness was higher in patients with clinically evident VTE than in patients without these complications (median [interquartile range] 70 mm [68 to 71] versus 65 mm [61 to 68]; p < 0.001). The preoperative clot formation time was lower in patients with clinically evident VTE than those without clinically evident VTE (median 61 seconds [58 to 65] versus 70 seconds [67 to 74]; p < 0.001), and also the postoperative clot formation time was lower in patients with clinically evident VTE than those without these complications (median 52 seconds [49 to 59] versus 62 seconds [57 to 68]; p < 0.001). Increased BMI was also associated with clinically evident VTE (odds ratio 1.26 [95% confidence interval 1.07 to 1.53]; p < 0.001). We found no differences between patients with and without clinically evident VTE in terms of age, sex, smoking status, comorbidities, and preoperative use of anticoagulants. Lastly, preoperative clot formation time demonstrated the best performance for detecting the association of hypercoagulability with symptomatic VTE (AUC 0.89 [95% CI 0.81 to 0.97]), with 81% (95% CI 48% to 97%) sensitivity and 86% (95% CI 81% to 89%) specificity for clot formation time ≤ 65 seconds.

CONCLUSION

ROTEM's performance in this preliminary study was promising in terms of its association with symptomatic VTE. This study extended our earlier work by demonstrating that ROTEM has a high accuracy in detecting the level of hypercoagulability that is associated with symptomatic VTE. However, until its performance is validated in a study that applies a diagnostic gold standard (such as venography, duplex/Doppler, or chest CT) in all patients having ROTEM to confirm its performance, ROTEM should not be used as a regular part of clinical practice.

LEVEL OF EVIDENCE

Level IV, diagnostic study.

Viscoelastometric Testing to Assess Hemostasis of COVID-19: A Systematic Review

Infection by SARS-CoV-2 is associated with a high risk of thrombosis. The laboratory documentation of hypercoagulability and impaired fibrinolysis remains a challenge. Our aim was to assess the potential usefulness of viscoelastometric testing (VET) to predict thrombotic events in COVID-19 patients according to the literature. We also (i) analyzed the impact of anticoagulation and the methods used to neutralize heparin, (ii) analyzed whether maximal clot mechanical strength brings more information than Clauss fibrinogen, and (iii) critically scrutinized the diagnosis of hypofibrinolysis. We performed a systematic search in PubMed and Scopus databases until 31st December 2020. VET methods and parameters, and patients' features and outcomes were extracted. VET was performed for 1063 patients (893 intensive care unit (ICU) and 170 non-ICU, 44 studies). There was extensive heterogeneity concerning study design, VET device used (ROTEM, TEG, Quantra and ClotPro) and reagents (with non-systematic use of heparin neutralization), timing of assay, and definition of hypercoagulable state. Notably, only 4 out of 25 studies using ROTEM reported data with heparinase (HEPTEM). The common findings were increased clot mechanical strength mainly due to excessive fibrinogen component and impaired to absent fibrinolysis, more conspicuous in the presence of an added plasminogen activator. Only 4 studies out of the 16 that addressed the point found an association of VETs with thrombotic events. So-called functional fibrinogen assessed by VETs showed a variable correlation with Clauss fibrinogen. Abnormal VET pattern, often evidenced despite standard prophylactic anticoagulation, tended to normalize after increased dosing. VET studies reported heterogeneity, and small sample sizes do not support an association between the poorly defined prothrombotic phenotype of COVID-19 and thrombotic events.

Higher coagulation activity in hip fracture patients: A case-control study using rotational thromboelastometry

INTRODUCTION

Trauma-induced coagulopathy has been extensively investigated in the multitrauma setting, but only sparsely following moderate orthopedic trauma. The purpose of this study was to evaluate changes in the hemostatic profile of patients with hip fractures, using rotational thromboelastometry (ROTEM).

METHODS

198 patients with hip fractures who underwent surgery were included in the study. A matched group of 52 healthy individuals was also enrolled. Demographics, conventional laboratory assays, and ROTEM parameters were recorded and compared between patients and healthy adults. The preoperative and postoperative ROTEM values of fractured patients were also compared.

RESULTS

The conventional coagulation assays were similar for the 2 groups. However, several ROTEM parameters including EXTEM MCF (P < .001), EXTEM alpha angle (P < .001), INTEM MCF (P < .001), INTEM A10 (P < .001), and INTEM alpha angle (P < .001) significantly differed between the 2 groups indicating a higher coagulation potential following hip fractures. Also, fractured patients had significantly lower INTEM and EXTEM CT values (P = .008 and P = .012, respectively) and significantly lower INTEM and EXTEM CFT values (P < .001). Adjusted analysis for confounders further confirmed the direct relationship between hip fracture and higher coagulation activity. Last, INTEM CT and CFT significantly decreased (P = .008 and P < .001, respectively), while INTEM MCF, A10, and alpha angle significantly increased (P < .001) postoperatively, indicating that surgery further increases the coagulation potential.

CONCLUSION

A higher coagulation activity following hip fractures and surgical treatment can be detected by ROTEM shortly after the injury, even when this is undetectable by conventional coagulation assays.

The effect of hematocrit, fibrinogen concentration and temperature on the kinetics of clot formation of whole blood

BACKGROUND

Dynamic mechanical analysis of blood clots can be used to detect the coagulability of blood.

OBJECTIVE

We investigated the kinetics of clot formation by changing several blood components, and we looked into the clot "signature" at its equilibrium state by using viscoelastic and dielectric protocols.

METHODS

Oscillating shear rheometry, ROTEM, and a dielectro-rheological device was used.

RESULTS

In fibrinogen- spiked samples we found the classical high clotting ability: shortened onset, faster rate of clotting, and higher plateau stiffness. Electron microscopy explained the gain of stiffness. Incorporated RBCs weakened the clots. Reduction of temperature during the clotting process supported the development of high moduli by providing more time for fiber assembly. But at low HCT, clot firmness could be increased by elevating the temperature from 32 to 37°C. In contrast, when the fibrinogen concentration was modified, acceleration of clotting via temperature always reduced clot stiffness, whatever the initial fibrinogen concentration. Electrical resistance increased continuously during clotting; loss tangent (D) (relaxation frequency 249 kHz) decreased when clots became denser: fewer dipoles contributed to the relaxation process. The relaxation peak (Dmax) shifted to lower frequencies at higher platelet count.

CONCLUSION

Increasing temperature accelerates clot formation but weakens clots. Rheometry and ROTEM correlate well.

Advances in monitoring anticoagulant therapy

Anticoagulant drugs directly or indirectly influence coagulation factors preventing fibrin formation, thus preventing blood clotting. They are classified into two groups according to the mode of application, namely parenteral and oral drugs. Among the latter, vitamin K antagonists (most often warfarin) were most widely used for almost a century. In recent years new oral anticoagulant drugs have become available that directly target either factor IIa or Xa (direct oral anticoagulants, DOACs). The proportion of patients to whom DOACs are prescribed is increasing because clinical studies have proved they are at least as effective and safe as vitamin K antagonists. Some of the anticoagulant drugs require regular laboratory monitoring, while others only need assessment of blood drug levels in specific clinical situations. This chapter provides an overview of appropriate laboratory tests used for either regular laboratory monitoring of therapy or occasional assessment of the anticoagulant effect of both parenteral and oral anticoagulant drugs used in clinical practice.

Comparison of antithrombin-dependent and direct inhibitors of factor Xa or thrombin on the kinetics and qualitative characteristics of blood clots

BACKGROUND

Venous thromboembolism (VTE) is associated with significant morbidity and mortality.

OBJECTIVES

We investigated the impact of direct and AT-dependent FXa or thrombin inhibitors on thrombus formation.

METHODS

Whole blood thromboelastometry and thrombin generation were assessed after triggering the TF pathway. Clinically relevant concentrations of rivaroxaban, fondaparinux, dabigatran or tinzaparin and an association of rivaroxaban and dabigatran were examined.

RESULTS

All agents delayed thrombus formation in a concentration-dependent manner, as documented by the prolongation of the clotting time (CT) and clot formation time (CFT). Rivaroxaban did not significantly alter the α-angle or maximum clot firmness (MCF). In contrast, dabigatran and fondaparinux altered the process of clot structure by decreasing the α-angle, but did not modify clot firmness. The later property was significantly affected only by tinzaparin that also reduced the MCF. The association of rivaroxaban and dabigatran did not affect the MCF, although it amplified the effect on CFT and α-angle.

CONCLUSIONS

All agents delayed thrombus formation. However, the compounds differed substantially with respect to fibrin polymerization rate and clot firmness. Comparison of the data obtained by thrombin generation assessment with those obtained by the thromboelastometric study shows that the delay in clot formation is principally associated with prolongation of the initiation phase of thrombin formation as well as a reduction of the propagation phase. Tinzaparin was much more potent than the other agents both with regard to suppression of thrombin generation and by delay in clot formation.

Pre- to postoperative coagulation profile of 307 patients undergoing oesophageal resection with epidural blockade over a 10-year period in a single hospital: implications for the risk of spinal haematoma

Background

Epidural anaesthesia and analgesia are indicated for oesophageal surgery. A rare but serious complication is spinal haematoma, which can occur on insertion, manipulation or withdrawal of catheters. Evidence and guidelines are vague regarding which tests are appropriate and how to interpret their results. We aimed to describe how routine coagulation test results change during oesophagectomy’s perioperative course.

Methods

Following ethical approval, we retrospectively identified patients who had undergone oesophagectomy between 2002 and 2012. Blood test results and details of operations, haemorrhage and complications were recorded and analysed with Excel and R. A literature search was conducted using the PubMed terms ‘epidural’ AND ‘coagulation’ AND English language. Relevant articles published in 2000 and after were included.

Results

Three hundred and seven patients received a thoracic epidural infusion with bupivacaine and morphine while 51 received an intravenous morphine infusion. Tests taken preoperatively and before the planned withdrawal of the epidural catheter demonstrated increases in all three measures: aPTT (activated partial thromboplastin time), PT-INR (prothrombin international normalised ratio) and platelet count (Plc). Postoperative thrombocytopenia was almost non-existent while aPTT or PT-INR was elevated above the reference range in 129/307 patients: aPTT was elevated in 116/307 while PT-INR was elevated in 32/307. This is too small a sample to allow meaningful estimation of risk of spinal haematoma: it may be as high as 2.3%. The literature search returned 275 articles, of which 57 were relevant. Twenty-one concerned the natural history of postoperative coagulation; 16, the incidence of and risk factors for spinal haematoma; and 5, evaluation of specific blood tests. Postoperative coagulation is characterised by thrombocytosis and transient moderately abnormal routine coagulation test results. Viscoelastic tests are not validated in the stable postoperative setting.

Conclusions

Screening for coagulopathy before removal of epidural catheters is of unclear benefit since elevated aPTT and PT-INR are usual and may not indicate hypocoagulation. A thorough clinical assessment is important. We nevertheless recommend caution when being presented with elevated routine tests of coagulation before withdrawing an epidural catheter: viscoelastic haemostatic tests may have a role in testing before withdrawal of epidural catheters but they are so far not validated. Future research should include advanced coagulation analysis as soon as a patient is unfortunate enough to have a spinal haematoma.

Electronic supplementary material

The online version of this article (10.1186/s13741-017-0070-7) contains supplementary material, which is available to authorized users.

Development and validation of a high throughput whole blood thrombolysis plate assay

The objective of this work was to develop a high throughput assay for testing in vitro the thrombolytic activity using citrated whole blood samples, and to overcome the limitations of currently available techniques. We successfully developed a method that involves forming halo shaped, tissue factor induced, whole blood clots in 96 well plates, and then precisely measuring the thrombolysis process with a spectrophotometer plate reader. We here describe the implementation of this novel method, which we refer to as halo assay, and its validation with plasmin, urokinase and tissue plasminogen activator at different doses. The resulting data is a highly detailed thrombolysis profile, allowing comparison of different fibrinolytic agents. The time point analysis allows kinetic data to be collected and calculated to determine key parameters such as the activation time and the rate of fibrinolysis. We also assessed the capacity of the model to study the effect of clot maturation time on the fibrinolytic rate, an aspect of thrombosis rather unexplored with currently available methods, but of increasing importance in drug development. This novel thrombolysis assay could be an extremely useful research tool; to study the complex process of thrombolysis, and a valuable translational clinical tool; as a screening device to rapidly identify hypo- or hyper-fibrinolysis.