Global assays of fibrinolysis

Validation of the time to attain maximal clot amplitude after reaching maximal clot formation velocity parameter as a measure of fibrinolysis using rotational thromboelastometry and its application in the assessment of fibrinolytic resistance in septic patients: a prospective observational study: communication from the ISTH SSC Subcommittee on Fibrinolysis

BACKGROUND

In sepsis, fibrinolysis resistance correlates with worse outcomes. Practically, rotational thromboelastometry (ROTEM) is used to report residual clot amplitude relative to maximum amplitude at specified times after clot formation clot lysis indices (CLIs). However, healthy individuals can exhibit similar CLIs, thus making it challenging to solely diagnose the low fibrinolytic state. Furthermore, CLI does not include the kinetics of clot formation, which can affect overall fibrinolysis. Therefore, a more nuanced analysis, such as time to attain maximal clot amplitude after reaching maximal clot formation velocity (t-AUCi), is needed to better identify fibrinolysis resistance in sepsis.

OBJECTIVES

To evaluate the correlation between the degree of fibrinolytic activation and t-AUCi in healthy or septic individuals.

METHODS

Whole blood (n = 60) from septic or healthy donors was analyzed using tissue factor-activated (EXTEM) and nonactivated (NATEM) ROTEM assays. Lysis was initiated with tissue-type plasminogen activator, and CLI and t-AUCi were calculated. Standard coagulation tests and plasma fibrinolysis markers (D-dimer, plasmin-α2-antiplasmin complex, plasminogen activator inhibitor type 1, and plasminogen) were also measured.

RESULTS

t-AUCi values decreased with increasing fibrinolytic activity and correlated positively with CLI for different degrees of clot lysis both in EXTEM and NATEM. t-AUCi cutoff value of 1962.0 seconds in EXTEM predicted low fibrinolytic activity with 81.8% sensitivity and 83.7% specificity. In addition, t-AUCi is not influenced by clot retraction.

CONCLUSION

Whole-blood point-of-care ROTEM analyses with t-AUCi offers a more rapid and parametric evaluation of fibrinolytic potential compared with CLI, which can be used for a more rapid and accurate diagnosis of fibrinolysis resistance in sepsis.

Fibrin and Fibrinolytic Enzyme Cascade in Thrombosis: Unravelling the Role

Blood clot formation in blood vessels (thrombosis) is a major cause of life-threatening cardiovascular diseases. These clots are formed by αA-, βB-, and ϒ-peptide chains of fibrinogen joined together by isopeptide bonds with the help of blood coagulation factor XIIIa. These clot structures are altered by various factors such as thrombin, platelets, transglutaminase, DNA, histones, and red blood cells. Various factors are used to dissolve the blood clot, such as anticoagulant agents, antiplatelets drugs, fibrinolytic enzymes, and surgical operations. Fibrinolytic enzymes are produced by microorganisms (bacteria, fungi, etc.): streptokinase of Streptococcus hemolyticus, nattokinase of Bacillus subtilis YF 38, bafibrinase of Bacillus sp. AS-S20-I, longolytin of Arthrobotrys longa, versiase of Aspergillus versicolor ZLH-1, etc. They act as a thrombolytic agent by either enhancing the production of plasminogen activators (tissue or urokinase types), which convert inactive plasminogen to active plasmin, or acting as plasmin-like proteins themselves, forming fibrin degradation products which cause normal blood flow again in blood vessels. Fibrinolytic enzymes may be classified in two groups, as serine proteases and metalloproteases, based on their catalytic properties, consisting of a catalytic triad responsible for their fibrinolytic activity having different physiochemical properties (such as molecular weight, pH, and temperature). The analysis of fibrinolysis helps to detect hyperfibrinolysis (menorrhagia, renal failure, etc.) and hypofibrinolysis (diabetes, obesity, etc.) with the help of various fibrinolytic assays such as a fibrin plate assay, fibrin microplate assay, the viscoelastic method, etc. These fibrinolytic activities serve as a key aspect in the recognition of numerous cardiovascular diseases and can be easily produced on a large scale with a short generation time by microbes and are less expensive.

Sensitivity and specificity of thromboelastography for hyperfibrinolysis: Comparison of TEG 5000 and TEG 6S CK LY30 systems

OBJECTIVES

The sensitivity and specificity of clot lysis at 30 minutes after maximum clot strength (LY30), as measured by thromboelastography (TEG), for clinically significant hyperfibrinolysis have not been compared across the 2 US Food and Drug Administration-approved instruments (the TEG 5000 and TEG 6s [Haemonetics]).

METHODS

We performed a retrospective, single-center analysis of these 2 instruments using the kaolin (CK) reagent.

RESULTS

Local verification studies showed that the TEG 5000 and TEG 6s CK LY30 upper limits of normal (ULNs) were distinct (5.0% and 3.2%, respectively). Retrospective analysis of patient data showed that abnormal LY30 was 6 times more prevalent with the TEG 6s than with the TEG 5000 instrument. LY30 was a significant predictor of mortality with both instruments (TEG 6s: receiver operating characteristic [ROC] area under the curve [AUC] = 0.836, P ≤ .0001; TEG 5000: ROC AUC = 0.779, P = .028). The optimal LY30 cut point was determined based on these mortality data for each instrument. The TEG 6s showed superior mortality prediction than the TEG 5000 at lower LY30 levels (≥10%), with likelihood ratios of 8.22 and 2.62 for the TEG 6s and TEG 5000, respectively. Patients with a TEG 6s CK LY30 of 10% or higher were significantly more likely to die, receive cryoprecipitate, receive transfusions, or receive massive transfusion than patients with a TEG 6s LY30 of 3.3% to 9.9% (all P < .01). Patients with a TEG 5000 LY30 of 17.1% or higher were significantly more likely to die or use cryoprecipitate (P < .05); transfusion and massive transfusion protocol were not significantly different. Whole blood spiking studies showed that 70 ng/mL tissue plasminogen activator (tPA) achieved an average LY30 of approximately 10% for both instruments.

CONCLUSIONS

CK LY30 above the ULN is a sensitive but not specific cutoff for hyperfibrinolysis. At least moderately elevated CK LY30 carries more clinical portent on the TEG 6s instrument than on the TEG 5000. These TEG instruments are not sensitive to low concentrations of tPA.

Association of Fibrinolytic Potential and Risk of Mortality in Cancer Patients

Cancer is a leading cause of death, and the fibrinolytic system shows cooperative effects that facilitate the growth of tumors and the appearance of metastases. This prospective study aimed to evaluate the fibrinolytic potential in cancer patients and its association with mortality outcomes using the fluorometric method of simultaneous thrombin and plasmin generation. The study included 323 cancer patients and 148 healthy individuals. During the 12-month follow-up, 68 patients died. Compared to the control group, cancer patients showed alterations in thrombin production consistent with a hypercoagulability profile, and an increase in plasmin generation. Mortality risk was associated with two parameters of thrombin in both univariate and multivariable analysis: maximum amplitude (Wald 11.78, p < 0.001) and area under the curve (Wald 8.0, p < 0.005), while such associations were not observed for plasmin. In conclusion, this was the first study able to demonstrate the simultaneous evaluation of thrombin and plasmin generation in newly diagnosed untreated cancer patients. Patients with cancer have been observed to exhibit a hypercoagulable profile. During the study, two parameters linked to thrombin generation, MA and AUC, were identified and found to have a potential association with mortality risk. However, no associations were found with parameters related to plasmin generation.

Testing strategies used in the diagnosis of rare inherited bleeding disorders

INTRODUCTION

Rare Bleeding Disorders have a low population prevalence and may not be recognized by most clinicians. In addition, knowledge gaps of the indicated laboratory tests and their availability add to the potential for delayed diagnosis or misdiagnosis. The lack of widely available commercial, regulatory body approved esoteric tests limit them to reference laboratories, thus limiting easy access for patients.

AREAS COVERED

A literature search of Pubmed, Medline, Embase and review of international society guidelines was performed. Additional references from published articles were reviewed. A patient-centered approach to recognition and evaluation of RBD is discussed.

EXPERT OPINION

Recognition of RBD relies on obtaining a detailed patient personal and family hemostatic history. Inquiry into a history of involvement of other organ systems is important and if present should lead to suspicion of an inherited platelet disorder or a variant of Ehlers Danlos Syndrome. Multiple factors contribute to the complexity of development of efficient algorithms for diagnostic testing. Limitations in diagnostic sensitivity and specificity of screening tests, diagnostic tests, and esoteric tests further compound the complexity of establishing a diagnosis. Educational efforts focusing on clinician awareness of RBDs and available testing options are vital for optimal management of such patients.

Assays to quantify fibrinolysis: strengths and limitations. Communication from the International Society on Thrombosis and Haemostasis Scientific and Standardization Committee on fibrinolysis

Fibrinolysis is a series of enzymatic reactions that degrade insoluble fibrin. Plasminogen activators convert the zymogen plasminogen to the active serine protease plasmin, which cleaves and solubilizes crosslinked fibrin clots into fibrin degradation products. The quantity and quality of fibrinolytic enzymes, their respective inhibitors, and clot structure determine overall fibrinolysis. The quantity of protein can be measured by antigen-based assays, and both quantity and quality can be assessed using functional assays. Furthermore, variations of commonly used assays have been reported, which are tailored to address the role(s) of specific fibrinolytic factors and cellular elements (eg, platelets, neutrophils, and red blood cells). Although the concentration and/or activity of a protein can be quantified, how these individual components contribute to the overall fibrinolysis outcome can be challenging to determine. This difficulty is due to temporal changes within and around the thrombi during the clot breakdown, particularly the fibrin matrix structure, and composition. Furthermore, terms such as "fibrinolytic activity/potential," "plasminogen activation," and "plasmin activity" are often used interchangeably despite having different definitions. The purpose of this review is to 1) summarize the assays measuring fibrinolysis activity and potential, 2) facilitate the interpretation of data generated by these assays, and 3) summarize the strengths and limitations of these assays.

Fibrinolysis: an illustrated review

In response to vessel injury (or other pathological conditions), the hemostatic process is activated, resulting in a fibrous, cellular-rich structure commonly referred to as a blood clot. Succeeding the clot's function in wound healing, it must be resolved. This illustrated review focuses on fibrinolysis-the degradation of blood clots or thrombi. Fibrin is the main mechanical and structural component of a blood clot, which encases the cellular components of the clot, including platelets and red blood cells. Fibrinolysis is the proteolytic degradation of the fibrin network that results in the release of the cellular components into the bloodstream. In the case of thrombosis, fibrinolysis is required for restoration of blood flow, which is accomplished clinically through exogenously delivered lytic factors in a process called external lysis. Fibrinolysis is regulated by plasminogen activators (tissue-type and urokinase-type) that convert plasminogen into plasmin to initiate fiber lysis and lytic inhibitors that impede this lysis (plasminogen activator inhibitors, alpha 2-antiplasmin, and thrombin activatable fibrinolysis inhibitor). Furthermore, the network structure has been shown to regulate lysis: thinner fibers and coarser clots lyse faster than thicker fibers and finer clots. Clot contraction, a result of platelets pulling on fibers, results in densely packed red blood cells (polyhedrocytes), reduced permeability to fibrinolytic factors, and increased fiber tension. Extensive research in the field has allowed for critical advancements leading to improved thrombolytic agents. In this review, we summarize the state of the field, highlight gaps in knowledge, and propose future research questions.

Laboratory evaluation of a new integrative assay to phenotype plasma fibrinolytic system

BACKGROUND

There is currently no universal and standardized test available to phenotype plasma fibrinolytic system.

AIMS

Our main aims were to evaluate the performances of the 'global fibrinolysis capacity' assay (GFC) performed with the Lysis Timer® instrument, and to study the influence of some preanalytical conditions.

METHOD

Euglobulin clot lysis time (ECLT) and GFC were performed under several preanalytical conditions.

RESULTS

GFC showed satisfactory intra- and inter-run precision. Frozen controls and reagents showed stability over the studied period. There was no statistically significant difference between GFC assessed in plasma samples processed at 4 °C or at 20 °C. GFC assessed with frozen-thawed plasma samples was prolonged when compared to fresh samples (p = 0.014). The centrifugation scheme had no influence on PAI-1 activity levels, GFC and ECLT. Reference interval for GFC ranges from 29.3 (C I90% = 26.9-31.9) to 49.5 (90% CI = 45.9-52.2) minutes. In addition, a preliminary study in 40 healthy volunteers and 43 adult patients referred for investigation of a bleeding disorder was conducted to compare GFC and ECLT assays in their ability to classify samples with shortened or prolonged clot lysis times. Disagreements between ECLT and GFC were observed for 23 samples (out of 83), most of them minor.

CONCLUSION

GFC is suitable and convenient for a broad clinical use and can be performed with frozen-thawed plasma samples. Unlike ECLT, GFC is designed to take into account the balance between inhibitors and activators of the fibrinolytic system and could detect both hypo- and hyperfibrinolytic states. Whether it is as suitable as or even better than ECLT to detect a bleeding tendency due to a hyperactive fibrinolytic system deserves to be properly investigated.

Hemostatic Effects of Tranexamic Acid in Cesarean Delivery: An Ancillary Study of the TRAAP2 Study

BACKGROUND

 Fibrinolysis activation during delivery contributes to postpartum hemorrhage (PPH). Clot lysis time studied with the global fibrinolytic capacity device (GFC/LT) is a functional test which rapidly assesses fibrinolytic profile. Tranexamic acid (TXA) is an efficient antifibrinolytic therapy.

METHODS

 We prospectively studied fibrinolysis and coagulation in 33 women included in the TRAAP2 trial, which aimed to assess the impact of TXA in preventing PPH following a cesarean delivery. TXA or placebo was randomly administered after childbirth as part of the TRAAP2 trial's protocol. Fibrinolytic (GFC/LT, plasma concentration of fibrinolysis activators and inhibitors) and hemostatic parameters were assayed at three sample times (TREF [T-reference] after anesthesia, T15 and T120minutes after TXA, or placebo administration).

RESULTS

 All cesarean deliveries were elective. In the placebo group, the clot lysis time assessed with GFC/LT significantly decreased between TREF and T120, indicating an activated fibrinolysis (44 [interquartile range, IQR: 40-48] vs. 34 [IQR: 30-36] minutes, p<0.001). In both TXA and placebo groups, significant fluctuations of the plasmatic concentrations of fibrinolytic mediators were noticed over time, suggesting fibrinolysis activation. Clot lysis time measured by GFC/LT was significantly increased in women of the TXA group as compared with those in the placebo group at T15 (120 [120-120] vs. 36 [34-41] minutes, p<0.001) and T120minutes (113 [99-120] vs. 34 [30-36] minutes, p<0.001) after drug administration, indicating a decreased in fibrinolysis in those women.

CONCLUSIONS

 GFC/LT evidenced fibrinolysis activation during cesarean delivery, linked to a decrease in fibrinolytic inhibitors. GFC/LT revealed a significant antifibrinolytic effect of TXA compared with placebo.

Predictive ability of viscoelastic testing using ClotPro® for short-term outcome in patients with severe Covid-19 ARDS with or without ECMO therapy: a retrospective study

BACKGROUND

SARS-CoV-2 infections are suspected to trigger the coagulation system through various pathways leading to a high incidence of thromboembolic complications, hypercoagulation and impaired fibrinolytic capacity were previously identified as potentially mechanisms. A reliable diagnostic tool for detecting both is still under discussion. This retrospective study is aimed to examine the prognostic relevance of early viscoelastic testing compared to conventional laboratory tests in COVID-19 patients with acute respiratory distress syndrome (ARDS).

METHODS

All mechanically ventilated patients with COVID-19 related ARDS treated in our intensive care unit (ICU) between January and March 2021 were included in this study. Viscoelastic testing (VET) was performed using the ClotPro® system after admission to our ICU. Prevalence of thromboembolic events was observed by standardized screening for venous and pulmonary thromboembolism using complete compression ultrasound and thoracic computed tomography pulmonary angiography at ICU admission, respectively. We examined associations between the severity of ARDS at admission to our ICU, in-hospital mortality and the incidence of thromboembolic events comparing conventional laboratory analysis and VET. ECMO related coagulopathy was investigated in a subgroup analysis. The data were analyzed using the Mann-Whitney U test.

RESULTS

Of 55 patients enrolled in this study, 22 patients required treatment with ECMO. Thromboembolic complications occurred in 51% of all patients. Overall hospital mortality was 55%. In patients with thromboembolic complications, signs of reduced fibrinolytic capacity could be detected in the TPA assay with prolonged lysis time, median 460 s (IQR 350-560) vs 359 s (IQR 287-521, p = 0.073). Patients with moderate to severe ARDS at admission to our ICU showed increased maximum clot firmness as a sign of hypercoagulation in the EX-test (70 vs 67 mm, p < 0.05), FIB-test (35 vs 24 mm, p < 0.05) and TPA-test (52 vs 36 mm, p < 0.05) as well as higher values of inflammatory markers (CRP, PCT and IL6). ECMO patients suffered more frequently from bleeding complications (32% vs 15%).

CONCLUSION

Although, the predictive value for thromboembolic complications or mortality seems limited, point-of-care viscoelastic coagulation testing might be useful in detecting hypercoagulable states and impaired fibrinolysis in critically ill COVID-19 ARDS patients and could be helpful in identifying patients with a potentially very severe course of the disease.

Point of care coagulation management in anesthesiology and critical care

Point of care (POC) devices are increasingly used in the ICU and in anesthesia. Besides POC-devices for blood gas analysis, several devices are available for coagulation measurements. Although basic principles for thromboelastographic measurements are not novel, some promising developments were made during the last decade improving both user-friendliness and measurement reliability. For instance, POC measurements of activated clotting time (ACT) for heparin monitoring is still regarded as standard-of-care in cardiac interventions and surgery. In the field of anesthesia and intensive care medicine, POC-devices for thromboelastographic and platelet aggregation measurements are widely used. Their impact in case of bleeding and patient blood management for cardiothoracic and trauma surgery is well known. Moreover, there are promising concepts for anticoagulation monitoring including new oral anticoagulant drugs. Coagulation POC-devices may also identify patients at specific risk for thromboembolic events quickly. On the other hand, benefits of POC-devices need to be balanced against limitations, which include technical restrictions and operator related errors, mainly affecting reproducibility and interpretation of results. Therefore, it is recommendable to consider results of POC-coagulation testing in comparison to standard laboratory tests (SLT). Nevertheless, in urgent or emergency situations POC results enable fast decision making to optimize patient care.

Disorders of Fibrinogen and Fibrinolysis

Fibrinogen plays a fundamental role in coagulation through its support for platelet aggregation and its conversion to fibrin. Fibrin stabilizes clots and serves as a scaffold and immune effector before being broken down by the fibrinolytic system. Given its importance, abnormalities in fibrin(ogen) and fibrinolysis result in a variety of disorders with hemorrhagic and thrombotic manifestations. This review summarizes (i) the basic elements of fibrin(ogen) and its role in coagulation and the fibrinolytic system; (ii) the laboratory evaluation for fibrin(ogen) disorders, including the use of global fibrinolysis assays; and (iii) the management of congenital and acquired disorders of fibrinogen and fibrinolysis.

A simple method for obtaining human albumin and its use for in vitro interaction assays with indole-thiazole and indole-thiazolidinone derivatives

This work aimed to develop a simple and low-cost method to obtain human serum albumin (HSA) and its consequent application for in vitro drug interaction assays. The HSA was purified by classic principles of plasma precipitation and thermocoagulation, using a multiple-stage fractionation. The quality of the final product was assessed by electrophoresis, protein dosage by the Lowry method and the pharmacopeial thermal stability. At the end, an isotonic solution of HSA with a total protein concentration of 2.7 mg·mL^-1 was obtained, which was visualized as a single band corresponding to the molecular weight of 66 kDa. After the thermal stability test, there was no indication of turbidity or color change of the solution. Finally, the HSA was useful for interaction assays with indole-thiazole and indole-thiazolidinone derivatives through UV-vis absorption and fluorescence spectroscopic studies, as well as by docking molecular analysis. Derivatives quenched the intrinsic fluorescence of HSA, disrupted the tryptophan residues microenvironment, and probably bind at Sudlow's site I. Therefore, the simplified methodology developed in this work proved to be effective in obtaining HSA that can be applied to research goals including drug interaction assays.

Fluorescently conjugated annular fibrin clot for multiplexed real-time digestion analysis

Impaired fibrinolysis has long been considered as a risk factor for venous thromboembolism. Fibrin clots formed at physiological concentrations are promising substrates for monitoring fibrinolytic performance as they offer clot microstructures resembling in vivo. Here we introduce a fluorescently labeled fibrin clot lysis assay which leverages a unique annular clot geometry assayed using a microplate reader. A physiologically relevant fibrin clotting formulation was explored to achieve high assay sensitivity while minimizing labeling impact as fluorescence isothiocyanate (FITC)-fibrin(ogen) conjugations significantly affect both fibrin polymerization and fibrinolysis. Clot characteristics were examined using thromboelastography (TEG), turbidity, scanning electron microscopy, and confocal microscopy. Sample fibrinolytic activities at varying plasmin, plasminogen, and tissue plasminogen activator (tPA) concentrations were assessed in the present study and results were compared to an S2251 chromogenic assay. The optimized physiologically relevant clot substrate showed minimal reporter-conjugation impact with nearly physiological clot properties. The assay demonstrated good reproducibility, wide working range, kinetic read ability, low limit of detection, and the capability to distinguish fibrin binding-related lytic performance. In combination with its ease for multiplexing, it also has applications as a convenient platform for assessing patient fibrinolytic potential and screening thrombolytic drug activities in personalized medical applications.

Microbial Fibrinolytic Enzymes as Anti-Thrombotics: Production, Characterisation and Prodigious Biopharmaceutical Applications

Cardiac disorders such as acute myocardial infarction, embolism and stroke are primarily attributed to excessive fibrin accumulation in the blood vessels, usually consequential in thrombosis. Numerous methodologies including the use of anti-coagulants, anti-platelet drugs, surgical operations and fibrinolytic enzymes are employed for the dissolution of fibrin clots and hence ameliorate thrombosis. Microbial fibrinolytic enzymes have attracted much more attention in the management of cardiovascular disorders than typical anti-thrombotic strategies because of the undesirable after-effects and high expense of the latter. Fibrinolytic enzymes such as plasminogen activators and plasmin-like proteins hydrolyse thrombi with high efficacy with no significant after-effects and can be cost effectively produced on a large scale with a short generation time. However, the hunt for novel fibrinolytic enzymes necessitates complex purification stages, physiochemical and structural-functional attributes, which provide an insight into their mechanism of action. Besides, strain improvement and molecular technologies such as cloning, overexpression and the construction of genetically modified strains for the enhanced production of fibrinolytic enzymes significantly improve their thrombolytic potential. In addition, the unconventional applicability of some fibrinolytic enzymes paves their way for protein hydrolysis in addition to fibrin/thrombi, blood pressure regulation, anti-microbials, detergent additives for blood stain removal, preventing dental caries, anti-inflammatory and mucolytic expectorant agents. Therefore, this review article encompasses the production, biochemical/structure-function properties, thrombolytic potential and other surplus applications of microbial fibrinolytic enzymes.

Clinical value of early assessment of hyperfibrinolysis by rotational thromboelastometry during postpartum hemorrhage for the prediction of severity of bleeding: A multicenter prospective cohort study in the Netherlands

INTRODUCTION

Coagulopathy may be the result of hyperfibrinolysis and could exacerbate bleeding following childbirth. Timely recognition of hyperfibrinolysis during the earliest stages of postpartum hemorrhage could identify women at risk of more severe blood loss who may benefit from targeted anti-fibrinolytic therapy. Rotational thromboelastometry (ROTEM^® ) is a point-of-care test that could detect hyperfibrinolysis. The aim of this study was to evaluate whether early assessment of hyperfibrinolysis by ROTEM during postpartum hemorrhage could predict progression to severe postpartum hemorrhage.

MATERIAL AND METHODS

During a prospective cohort study in the Netherlands among women with postpartum hemorrhage (total blood loss at least 1000 ml within 24 h after childbirth) ROTEM measurements were performed following 800-1500 ml of blood loss. Hyperfibrinolysis was defined as an enzymatic fibrinolysis index (ROTEM EXTEM maximum clot lysis [ML] minus the ROTEM APTEM ML) above 15%. Severe postpartum hemorrhage was defined as a composite end point of total blood loss greater than 2000 ml, transfusion of four or more units of packed cells, and/or need for an invasive intervention. The predictive value of hyperfibrinolysis for progression to severe postpartum hemorrhage was assessed by area under the receiver operating curve (AUC) and positive and negative predictive values.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT02149472).

RESULTS

Of 390 women included, 82 (21%) had severe postpartum hemorrhage. Four (1%) women had thromboelastometric evidence of hyperfibrinolysis, of whom two developed severe postpartum hemorrhage. The AUC for enzymatic fibrinolysis index more than 15% for progression to severe postpartum hemorrhage was 0.47 (95% CI 0.40-0.54). Positive and negative predictive values for this index were 50.0% (95% CI 6.8-93.2) and 79.3% (95% CI 74.9-83.2), respectively.

CONCLUSIONS

Thromboelastometric evidence of hyperfibrinolysis was rare in women with postpartum hemorrhage when assessed between 800 and 1500 ml of blood loss. The clinical predictive value of viscoelastometric point-of-care testing for hyperfibrinolysis for progression to severe postpartum hemorrhage during early postpartum hemorrhage is limited.

Anticoagulants and the Hemostatic System: A Primer for Occupational Stress Researchers

Anticoagulation, the body’s mechanism to prevent blood clotting, is an internal biomarker of an individual’s response to stress. Research has indicated that understanding the causes, processes, and consequences of anticoagulation can provide important insight into the experience of individuals facing emotional and occupational strain. Unfortunately, despite their importance, the mechanisms and implications of anticoagulation are unfamiliar to many researchers and practitioners working with trauma-exposed professionals. This paper provides an accessible primer on the topic of anticoagulation, including an overview of the biological process, the research connecting these processes with emotional and occupational functioning, as well as some potential methods for assessment.

Fibrin Network Formation and Lysis in Septic Shock Patients

Background: Septic shock patients are prone to altered fibrinolysis, which contributes to microthrombus formation, organ failure and mortality. However, characterisation of the individual patient’s fibrinolytic capacity remains a challenge due to a lack of global fibrinolysis biomarkers. We aimed to assess fibrinolysis in septic shock patients using a plasma-based fibrin clot formation and lysis (clot–lysis) assay and investigate the association between clot–lysis parameters and other haemostatic markers, organ dysfunction and mortality. Methods: This was a prospective cohort study including adult septic shock patients (n = 34). Clot–lysis was assessed using our plasma-based in-house assay. Platelet count, activated partial thromboplastin time (aPTT), international normalised ratio (INR), fibrinogen, fibrin D-dimer, antithrombin, thrombin generation, circulating fibrinolysis markers and organ dysfunction markers were analysed. Disseminated intravascular coagulation score, Sequential Organ Failure Assessment (SOFA) score and 30-day mortality were registered. Results: Three distinct clot–lysis profiles emerged in the patients: (1) severely decreased fibrin formation (flat clot–lysis curve), (2) normal fibrin formation and lysis and (3) pronounced lysis resistance. Patients with abnormal curves had lower platelet counts (p = 0.05), more prolonged aPTT (p = 0.04), higher lactate (p < 0.01) and a tendency towards higher SOFA scores (p = 0.09) than patients with normal clot–lysis curves. Fibrinogen and fibrin D-dimer were not associated with clot–lysis profile (p ≥ 0.37). Conclusion: Septic shock patients showed distinct and abnormal clot–lysis profiles that were associated with markers of coagulation and organ dysfunction. Our results provide important new insights into sepsis-related fibrinolysis disturbances and support the importance of assessing fibrinolytic capacity in septic shock.

Basic principles of viscoelastic testing

BACKGROUND

Viscoelastic testing is a method of hemostatic analysis that provides a real-time, holistic view of ex vivo clotting. It allows for examination of both cellular and plasma protein contributions to clotting including platelet number and function, fibrin(ogen) function, and coagulation factor function. The method assesses physical clot properties during the transition of blood from a liquid to a gel state, either by measurement of clot shear modulus using physical force transduction or by measurement of clot resonance frequency using sonometric interrogation. Results are reported in a live trace, with different trace parameters reflecting different contributors to hemostasis. These reported parameters vary between testing platforms.

RESULTS

In the United States, there are several commonly used Food and Drug Administration (FDA)-approved viscoelastic instruments available on the market. Those instruments that use sonometric clot assessment are more recently available and allow for improved portability for use near the patient's bedside. These instruments generally feature different reagent kits that allow more specific interrogation of different hemostatic pathways. Viscoelastic testing can predict the results of traditional plasma-based coagulation assays and has the added benefit of detecting hypercoagulability and severe hyperfibrinolysis. Implementation of viscoelastic testing in many clinical settings is becoming widespread and has proven to be efficacious in reducing blood transfusion rates in many settings. An impact on overall mortality and morbidity has not yet been demonstrated.

CONCLUSION

This article provides a narrative review of the basic principles of viscoelastic testing, including the science and technology behind the method, as well as currently available testing platforms and reagents.

Plasmin-mediated cleavage of high-molecular-weight kininogen contributes to acetaminophen-induced acute liver failure

Acetaminophen (APAP)-induced liver injury is associated with activation of coagulation and fibrinolysis. In mice, both tissue factor-dependent thrombin generation and plasmin activity have been shown to promote liver injury after APAP overdose. However, the contribution of the contact and intrinsic coagulation pathways has not been investigated in this model. Mice deficient in individual factors of the contact (factor XII [FXII] and prekallikrein) or intrinsic coagulation (FXI) pathway were administered a hepatotoxic dose of 400 mg/kg of APAP. Neither FXII, FXI, nor prekallikrein deficiency mitigated coagulation activation or hepatocellular injury. Interestingly, despite the lack of significant changes to APAP-induced coagulation activation, markers of liver injury and inflammation were significantly reduced in APAP-challenged high-molecular-weight kininogen-deficient (HK-/-) mice. Protective effects of HK deficiency were not reproduced by inhibition of bradykinin-mediated signaling, whereas reconstitution of circulating levels of HK in HK-/- mice restored hepatotoxicity. Fibrinolysis activation was observed in mice after APAP administration. Western blotting, enzyme-linked immunosorbent assay, and mass spectrometry analysis showed that plasmin efficiently cleaves HK into multiple fragments in buffer or plasma. Importantly, plasminogen deficiency attenuated APAP-induced liver injury and prevented HK cleavage in the injured liver. Finally, enhanced plasmin generation and HK cleavage, in the absence of contact pathway activation, were observed in plasma of patients with acute liver failure due to APAP overdose. In summary, extrinsic but not intrinsic pathway activation drives the thromboinflammatory pathology associated with APAP-induced liver injury in mice. Furthermore, plasmin-mediated cleavage of HK contributes to hepatotoxicity in APAP-challenged mice independently of thrombin generation or bradykinin signaling.

[Spontaneous fibrinolysis and possibilities of its acceleration in pulmonary embolism]

This review contains the data concerning the mechanisms of spontaneous fibrinolysis in pulmonary vessels and possibilities of its acceleration in pulmonary embolism. The spontaneous fibrinolysis system is known to be sequential and multifactorial, with the interaction of accelerators (t-PA and u-PA) and inhibitors (alpha-2-antiplasmin, PAI-1, TAFI). The fibrinolytic processes take place in case of prevailing reactions of accelerating factors over inhibiting ones. The endothelium of pulmonary vessels possesses pronounced antithrombogenic and profibrinolytic properties, therefore, the processes of fibrinolysis in the pulmonary vascular bed normally occur more intensively than in the vessels of the systemic circulation. The membrane proteins of the endothelium annexins A2 activate plasminogen, whereas thrombomodulin inhibits the activity of PAI-1. The main approaches to increase the fibrinolysis intensity in conditions of pulmonary embolism may be aimed at elevating the activity of fibrinolytic enzymes (enhancing the synthesis of annexins A2, the use of NMDA-receptor antagonists) and suppressing its inhibitors (the use of monoclonal antibodies to alpha-2-antiplasmin, as well as plasminogen activator inhibitor-1 (PAI-1) and thrombin-activatable fibrinolysis inhibitor (TAFI). Promising directions for future research can be the synthesis of a new generation of tissue-type plasminogen activators, and investigations of the possibility of clinical application of antithrombin and thrombomodulin, angiotensin converting enzyme inhibitors and cortisol antagonists. To meet these challenges, it is necessary to develop new models of venous thrombosis and acute pulmonary embolism in different animal species, with the assessment of the changes in the venous haemodynamics and pulmonary microcirculation on the background of administration of a new class of fibrinolytic agents.

Euglobulin clot lysis time reveals a high frequency of fibrinolytic activation in trauma

Activation of the fibrinolytic system plays a central role in the host response to trauma. There is significant heterogeneity in the degree of fibrinolysis activation at baseline that is usually assessed by whole blood thromboelastography (TEG). Few studies have focused on plasma markers of fibrinolysis that could add novel insights into the frequency and mechanisms of fibrinolytic activation in trauma. Global fibrinolysis in plasma was assessed using a modified euglobulin clot lysis time (ECLT) assay in 171 major trauma patients and compared to commonly assessed analytes of fibrinolysis. The median ECLT in trauma patients was significantly shorter at 8.5 h (IQR, 1.3-19.5) compared to 19.9 h (9.8-22.6) in healthy controls (p < 0.0001). ECLT values ≤2.5th percentile of the reference range were present in 83 (48.5%) of trauma patients, suggesting increased fibrinolytic activation. Shortened ECLT values were associated with elevated plasmin-antiplasmin (PAP) complexes and free tissue plasminogen activator (tPA) levels in plasma. Sixteen (9.2%) individuals met the primary outcome for massive transfusion, here defined as the critical administration threshold (CAT) of 3 units of packed red cells in any 60-minute period within the first 24 h. In a univariate screen, plasma biomarkers associated with CAT included D-dimer (p < 0.001), PAP (p < 0.05), free tPA (p < 0.05) and ECLT (p < 0.05). We conclude that fibrinolytic activation, measured by ECLT, is present in a high proportion of trauma patients at presentation. The shortened ECLT is partially driven by high tPA levels and is associated with high levels of circulating PAP complexes. Further studies are needed to determine whether ECLT is an independent predictor of trauma outcomes.

Fibrinolysis and bleeding of unknown cause

Patients with bleeding of unknown cause (BUC) present with a variety of mild to moderate bleeding symptoms, but no hemostatic abnormalities can be found. Hyperfibrinolysis is rarely evaluated as the underlying cause for bleeding in clinical practice, and well-established global assays for abnormal fibrinolysis are lacking. Few patients with definitive fibrinolytic disorders, including α2-antiplasmin deficiency, plasminogen activator inhibitor 1 deficiency, or Quebec platelet disorder, have been reported. This review aims to summarize data on established fibrinolytic disorders and to discuss assessments of fibrinolysis in prior bleeding cohorts. Furthermore, we review available global tests with the potential to measure fibrinolysis, such as turbidity fibrin clot assays and rotational thromboelastometry, and their relevance in the workup of patients with BUC. We conclude that, due to the lack of adequate global tests, hyperfibrinolysis might be an underdiagnosed cause for a bleeding disorder. The diagnosis of hyperfibrinolytic bleeding disorders would improve patient care as effective treatment with antifibrinolytic agents is available.

Fibrinolysis in Acute and Chronic Cardiovascular Disease

The formation of an obstructive thrombus within an artery remains a major cause of mortality and morbidity worldwide. Despite effective inhibition of platelet function by modern antiplatelet therapies, these agents fail to fully eliminate atherothrombotic risk. This may well be related to extensive vascular disease, beyond the protective abilities of the treatment agents used. However, recent evidence suggests that residual vascular risk in those treated with modern antiplatelet therapies is related, at least in part, to impaired fibrin clot lysis. In this review, we attempt to shed more light on the role of hypofibrinolysis in predisposition to arterial vascular events. We provide a brief overview of the coagulation system followed by addressing the role of impaired fibrin clot lysis in acute and chronic vascular conditions, including coronary artery, cerebrovascular, and peripheral vascular disease. We also discuss the role of combined anticoagulant and antiplatelet therapies to reduce the risk of arterial thrombotic events, addressing both efficacy and safety of such an approach. We conclude that impaired fibrin clot lysis appears to contribute to residual thrombosis risk in individuals with arterial disease on antiplatelet therapy, and targeting proteins in the fibrinolytic system represents a viable strategy to improve outcome in this population. Future work is required to refine the antithrombotic approach by modulating pathological abnormalities in the fibrinolytic system and tailoring therapy according to the need of each individual.

Aqueous two-phase deposition and fibrinolysis of fibroblast-laden fibrin micro-scaffolds

This paper describes printing of microscale fibroblast-laden matrices using an aqueous two-phase approach that controls thrombin-mediated enzymatic crosslinking of fibrin. Optimization of aqueous two-phase formulations enabled polymerization of consistent sub-microliter volumes of cell-laden fibrin. When plasminogen was added to these micro-scaffolds, the primary normal human lung fibroblasts converted it to plasmin, triggering gradual degradation of the fibrin. Time-lapse live-cell imaging and automated image analysis provided readouts of time to degradation of 50% of the scaffold as well as maximum degradation rate. The time required for degradation decreased linearly with cell number while it increased in a dose-dependent manner upon addition of TGF-β1. Fibroblasts isolated from idiopathic pulmonary fibrosis patients showed similar trends with regards to response to TGF-β1 stimulation. Addition of reactive oxygen species (ROS) slowed fibrinolysis but only in the absence of TGF-β1, consistent with published studies demonstrating that pro-fibrotic cellular phenotypes induced by TGF-β1 are mediated, at least in part, through increased production of ROS. FDA-approved and experimental anti-fibrosis drugs were also tested for their effects on fibrinolysis rates. Given the central role of fibrinolysis in both normal and pathogenic wound healing of various tissues, the high-throughput cell-mediated fibrinolysis assay described has broad applicability in the study of many different cell types and diseases. Furthermore, aqueous two-phase printing of fibrin addresses several current limitations of fibrin bio-inks, potentially enabling future applications in tissue engineering andin vitromodels.

Comparison of different activators of coagulation by turbidity analysis of hereditary dysfibrinogenemia and controls

Turbidity analysis is widely used as a quantitative technique in hereditary dysfibrinogenemia. We aimed to compare several coagulation triggers in hereditary dysfibrinogenemia and control plasmas. We included 20 patients with hereditary dysfibrinogenemia, 19 with hotspot mutations Aα Arg35His (n = 9), Aα Arg35Cys (n = 2), γ Arg301His (n = 6), γ Arg301Cys (n = 2), and one with Aα Phe27Tyr, and a commercial pooled normal plasma. Fibrin polymerization was activated by bovine or human thrombin or tissue factor (TF), in the presence or absence of tissue type plasminogen activator. The lag time (min), slope (mOD/s), maximum absorbance (MaxAbs, mOD), and area under the curve (AUCp, OD s) were calculated from the fibrin polymerization curves and the time for 50% clot degradation (T50, min), AUCf (OD s) and the overall fibrinolytic potential from fibrinolysis curves. The lag time was significantly shorter and AUC increased in Aα Arg35His patients with bovine thrombin as compared with human thrombin. The MaxAbs and AUCp were significantly higher in γArg301His patients with bovine thrombin compared with human thrombin. Fibrin polymerization parameters of patients' samples were closer to those of control when assessed with TF compared with both human and bovine thrombin. T50 and overall fibrinolytic potential were similar in all samples regardless of the coagulation trigger used, however, with TF the AUCf of Aα Arg35His and γ Arg301His groups were significantly decreased compared with control. Bovine and human thrombin cannot be used equally for studying fibrin polymerization in hotspot hereditary dysfibrinogenemia or control plasmas.

Fibrinolytic characteristics of Bacillus subtilis G8 isolated from natto

Due to the high prevalence of vascular obstructive diseases, discovering potent, safe, and affordable fibrinolytic agents is of importance. There is particular interest concerning the use of functional foods that have a fibrinolytic activity, such as natto, a Japanese fermented soy-based product made with Bacillus subtilis (natto) strain BEST195. We recently isolated another bacterial strain from natto commercialized in Indonesia, B. subtilis G8, which has proven to exert fibrinolytic activity. Herein, a further characterization of B. subtilis G8 was assessed through a comparison with commercialized nattokinase, the major fibrinolytic enzyme of B. subtilis, by utilizing various in vitro fibrinolytic assays, namely whole blood clot lysis, euglobulin clot lysis, the fibrin plate method, and zymography. Both nattokinase and B. subtilis G8 were able to dissolve both whole blood and euglobulin clots. Furthermore, both nattokinase and B. subtilis G8 were able to lyse blood clots, presumably due to their ability to directly lyse fibrin. Finally, a crude extract of B. subtilis G8 displayed six zymogram bands of approximately 42.0, 35.5, 30.8, 26.7, 20.0, and 13.7 kDa, with the strongest activity observed at 20.0 kDa. This indicates that B. subtilis G8 contained several fibrinolytic enzymes, which might have comprised nattokinase and other fibrinolytic enzymes. In summary, we demonstrated that a crude extract of B. subtilis G8 has potent fibrinolytic activity and that the activity was mediated by various fibrinolytic enzymes.

Measuring Fibrinolysis

Physiological fibrinolysis under normal conditions progresses slowly, in contrast to coagulation which is triggered rapidly to stop bleeding and defend against microbial invasion. Methods to detect fibrinolysis abnormalities are less simple and poorly standardized compared with common coagulation tests. Fibrinolysis can be accelerated by preparing euglobulin from plasma to reduce endogenous inhibitors, or by adding plasminogen activators to normal plasma. However, these manipulations complicate interpretation of results and diagnosis of a "fibrinolysis deficit." Many observational studies on antigen levels of fibrinolysis inhibitors, plasminogen activator inhibitor 1 or thrombin-activatable fibrinolysis inhibitor, zymogen or active enzyme have been published. However, conclusions are mixed and there are clear problems with harmonization of results. Viscoelastic methods have the advantage of being rapid and are used as point-of-care tests. They also work with whole blood, allowing the contribution of platelets to be explored. However, there are no agreed protocols for applying viscoelastic methods in acute care for the diagnosis of hyperfibrinolysis or to direct therapy. The emergence of SARS-CoV-2 and the dangers of associated coagulopathy provide new challenges. A common finding in hospitalized patients is high levels of D-dimer fibrin breakdown products, indicative of ongoing fibrinolysis. Well-established problems with D-dimer testing standardization signal that we should be cautious in using results from such tests as prognostic indicators or to target therapies.

Effects of antithrombotic drugs on the prothrombotic state in patients with atrial fibrillation: The west Birmingham atrial fibrillation project

BACKGROUND

Direct oral anticoagulants (DOACs) are known to prevent thrombosis but there is limited information about their activity on the clot formation and lysis cascade.

OBJECTIVES

This study assesses the role of apixaban, one of the four licenced DOACs, on clot dynamics in patients with atrial fibrillation (AF).

METHODS

We compared haemostatic and clot lysis characteristics between a group of patients with AF (n = 47) and a "disease control" group with ischaemic heart disease but in sinus rhythm (n = 39). Subsequently, we conducted clot structure studies in 3 groups of patients with AF on different antithrombotic drugs: warfarin (n = 60), apixaban (n = 60) or antiplatelets (n = 62) and in patients with AF naïve to oral anticoagulants before and after 3-months treatment with apixaban (n = 32). Haemostasis was investigated by a viscoelastic, whole blood technique (Thromboelastography/TEG), a "microplate-reader based", citrated plasma technique (microplate assay), immunoassays to determine plasma concentrations of plasminogen activator inhibitor-1 (PAI-1), tissue-Plasminogen Activator (t-PA), D-dimer and finally platelet derived and apoptotic microparticles.

RESULTS

Patients with AF have more potent thrombogenesis based on microplate assay indices [Rate of clot formation (p = 0.03, ƞ² = 0.06), Maximum optical density (p < 0.001, ƞ² = 0.05)] and delayed fibrinolysis [Rate of clot dissolution (p = 0.005, ƞ² = 0.17)] with increased levels of apoptotic microparticles (p = 0.02, ƞ² = 0.06) compared with the 'disease control' group. Apixaban was more effective in attenuating prothrombotic characteristics assessed by TEG {R (ε² = 0.21), K (ε² = 0.16) and angle [mean difference (MD), 95% Confidence Intervals (CI), vs warfarin 5, 0.96-8.6 and 8, 3.8-11.4 vs antiplatelets], (p < 0.001 for all indices)} compared with the other treatment groups. Patients on apixaban had lower D-dimer (p < 0.001, ε² = 0.17) and tPA (p = 0.03, MD 90, 95%CI 6-150 vs warfarin and MD 90, 95% CI 4-150 vs antiplatelets) levels. From the microplate assay analysis, warfarin and apixaban demonstrated comparable activity based on multiple indices, both superior to antiplatelets. However, warfarin was associated with reduced fibrin network robustness (Max. optical density p < 0.001, ε² = 0.1). Apixaban inhibited thrombosis, amplified fibrinolysis and decreased D-dimer (p = 0.001, r = 0.4) levels in the follow up study.

CONCLUSIONS

Patients with AF have impaired haemostasis and elevated levels of apoptotic microparticles. Apixaban appears to affect plasma prothrombotic characteristics in a distinctive manner compared with warfarin and to reduce biomarkers associated with adverse cardiovascular events.

Thromboelastographic Assessment of Fibrinolytic Activity in Postpartum Hemorrhage: A Retrospective Single-Center Observational Study

BACKGROUND

Postpartum hemorrhage is a leading cause of maternal mortality. Antifibrinolytic therapy has the potential to influence outcomes in postpartum hemorrhage, but the incidence of elevated fibrinolytic activity in postpartum hemorrhage is unknown.

METHODS

We retrospectively reviewed thromboelastography (TEG) results obtained for postpartum hemorrhage from 118 deliveries at The University of Chicago. TEG results were obtained as part of our postpartum hemorrhage protocol when blood loss exceeded 500 mL after vaginal delivery or 1000 mL after cesarean delivery. Our primary outcome was the incidence of elevated fibrinolytic activity, which we predefined as clot lysis ≥3% at 30 minutes (Ly30) on kaolin TEG. Platelet-mediated clot retraction can also lead to an elevated Ly30 on kaolin TEG. Therefore, to distinguish between fibrinolysis and clot retraction, we evaluated clot lysis using functional fibrinogen TEG, which contains a platelet inhibitor. We considered a kaolin TEG Ly30 ≥3% in conjunction with a nonzero functional fibrinogen TEG Ly30 suggestive of elevated fibrinolytic activity. We also recorded quantitative blood loss, primary etiology of hemorrhage, standard laboratory measurements of coagulation, and demographic and obstetric characteristics of the study population.

RESULTS

The median kaolin TEG Ly30 was 0.2% (interquartile range: 0%-0.8%). Fifteen of 118 women (12.7%; 95% confidence interval, 7.9%-19.9%) had kaolin TEG Ly30 values ≥3%. Of 15 patients with elevated Ly30 values, functional fibrinogen TEG Ly30 was available for 13, of which none demonstrated detectable clot lysis.

CONCLUSIONS

Our observation that none of the patients in our sample with kaolin TEG Ly30 values ≥3% had a nonzero functional fibrinogen TEG Ly30 value suggests that the observed elevations in kaolin TEG Ly30 may have been secondary to platelet-mediated clot retraction as opposed to fibrinolysis. Platelet-mediated clot retraction should be distinguished from fibrinolysis when assayed using viscoelastic techniques in postpartum hemorrhage. Further research is necessary to determine the optimal methods to assess fibrinolytic activity in postpartum hemorrhage.

Methodological variations affect the release of VEGF in vitro and fibrinolysis' time from platelet concentrates

Blood Concentrates (BCs) are autologous non-transfusional therapeutical preparations with biological properties applied in tissue regeneration. These BCs differ in the preparation method, in fibrin network architecture, growth factors release as well as in platelet/cell content. Methodological changes result in distinct matrices that can compromise their clinical effectiveness. The present study evaluated the influence of different g-forces and types of tubes in the release of vascular endothelial growth factor (VEGF) from platelet-rich fibrin (PRF) as a function of time. The PRF-like samples were obtained with three g-forces (200, 400, and 800 x g) for 10 minutes in pure glass tubes or in polystyrene-clot activator tubes. Scanning and Transmission electron microscopy was used to morphometric analyzes of PRF’s specimens and flow cytometry was used to quantify VEGF slow release until 7 days. Our results showed that platelets were intact and adhered to the fibrin network, emitting pseudopods and in degranulation. The fibrin network was rough and twisted with exosomic granulations impregnated on its surface. An increase in the concentration of VEGF in the PRF supernatant was observed until 7 days for all g forces (200, 400 or 800 xg), with the highest concentrations observed with 200 x g, in both tubes, glass or plastic. Morphological analyzes showed a reduction in the diameter of the PRF fibers after 7 days. Our results showed that g-force interferes with the shape of the fibrin network in the PRF, as well as affect the release of VEGF stored into platelets. This finding may be useful in applying PRF to skin lesions, in which the rapid release of growth factors can favor the tissue repair process. Our observations point to a greater clarification on the methodological variations related to obtaining PRF matrices, as they can generate products with different characteristics and degrees of effectiveness in specific applications.

A Pathological Clarification of Sepsis-Associated Disseminated Intravascular Coagulation Based on Comprehensive Coagulation and Fibrinolysis Function

BACKGROUND

 The functional dynamics of coagulation and fibrinolysis in patients with disseminated intravascular coagulation (DIC) vary due to the pathology and severity of various underlying diseases. Conventional measurements of hemostasis such as thrombin-antithrombin complex, plasmin-α2-plasmin-inhibitor complex, and fibrinogen-fibrin degradation products may not always reflect critical pathophysiologic mechanisms in DIC. This article aims to clarify the pathology of sepsis-associated DIC using assessment of comprehensive coagulation and fibrinolysis.

METHODS

 Plasma samples were obtained from 57 patients with sepsis-associated DIC at the time of initial diagnosis. Hemostasis parameters were quantified by clot-fibrinolysis waveform analysis (CFWA) and thrombin/plasmin generation assays (T/P-GA). The results were expressed as ratios relative to normal plasma.

RESULTS

 CFWA demonstrated that the maximum coagulation velocity (|min1|) ratio modestly increased to median 1.40 (min - max: 0.10 - 2.60) but the maximum fibrinolytic velocity (|FL-min1|) ratio decreased to 0.61 (0 - 1.19). T/P-GA indicated that the peak thrombin (Th-Peak) ratio moderately decreased to 0.71 (0.22 - 1.20), whereas the peak plasmin (Plm-Peak) ratio substantially decreased to 0.35 (0.02 - 1.43). Statistical comparisons identified a correlation between |min1| and Th-Peak ratios (ρ = 0.55, p < 0.001), together with a strong correlation between |FL-min1| and Plm-Peak ratios (ρ = 0.71, p < 0.001), suggesting that CFWA reflected the balance between thrombin and plasmin generation. With |min1| and |FL-min1| ratios, DIC was classified as follows: coagulation-predominant, coagulation/fibrinolysis-balanced, fibrinolysis-predominant, and consumption-impaired coagulation. The majority of patients in our cohort (80.7%) were coagulation-predominant.

CONCLUSION

 A pathological clarification of sepsis-associated DIC based on the assessment of coagulation and fibrinolysis dynamics may be useful for the hemostatic monitoring and management of optimal treatment in these individuals.

Development and application of global assays of hyper- and hypofibrinolysis

Numerous methods for evaluation of global fibrinolytic activity in whole blood or plasma have been proposed, with the majority based on tissue-type plasminogen activator (t-PA) addition to initiate fibrinolysis. We propose that such an approach is useful to reveal hypofibrinolysis, but t-PA concentrations should be kept to a minimum. In this paper, we describe a low-concentration t-PA plasma turbidity assay to evaluate several congenital factor deficiencies, including plasminogen activator inhibitor-1 (PAI-1) and plasminogen deficiency, as well as hemophilia A and B. In addition, we demonstrate a threshold dependency on endogenous PAI-1 levels. To assess endogenous hyperfibrinolysis, we suggest that assays that avoid t-PA addition are preferable, with assays based on euglobulin fractionation remaining a viable choice. We describe a euglobulin fraction clot lysis time (ECLT) assay with spectrophotometric readout and other modifications, and evaluate it as a tool to measure hyperfibrinolysis in inherited clotting factor deficiency states. We demonstrate that the ECLT is predominantly driven by residual amounts of PAI-1, t-PA, and α2-antiplasmin. These assays should be further evaluated for the detection of hypo- or hyperfibrinolysis in acquired thrombotic or hemorrhagic disorders.

The current status of viscoelastic testing in septic coagulopathy

Sepsis can be associated with different degrees of coagulopathy, ranging from a mild activation of the coagulation system to disseminated intravascular coagulation (DIC). The evaluation of haemostasis in the context of sepsis is important since it has been shown that anticoagulant therapies were beneficial mainly in patients with sepsis-induced DIC, but not in the general population of septic patients. Sepsis-induced haemostatic disturbances are not adequately reflected by standard coagulation tests (SCTs) which only consider the plasmatic components of the haemostatic system and not the cellular components. In addition, SCTs only assess the initiation phase of coagulation and reflect the activity of pro-coagulant factors, but lack sensitivity for the anticoagulant drive and the fibrinolytic activity. Viscoelastic tests (VET) are whole-blood tests which can assess clot formation and dissociation, and the contribution of both plasmatic and cellular components with a shorter turnaround time compared to SCTs. The use of VET in septic patients has proved useful for the assessment of the fibrinolytic activity, detecting hypercoagulable status and for the diagnosis of DIC and mortality risk prediction. While having relevant advantages over SCTs, the VET also present some blind spots or limitations leaving space for future improvement by the development of new reagents or new viscoelastic parameters.

Inherited disorders of the fibrinolytic pathway

Deficiencies or excessive activation of the  fibrinolytic system can result in severe, lifelong bleeding disorders. The most severe clinical phenotype is caused by α2-Antiplasmin (α2-AP) deficiency which results in excess fibrinolysis due to the inability to inhibit plasmin. Another bleeding disorder due to a defect in the fibrinolytic pathway results from Plasminogen activator inhibitor-1 (PAI-1) deficiency causing enhanced fibrinolysis due to the decreased inhibition of plasminogen activators resulting in increased conversion of plasminogen to plasmin. Both these disorders are rare and have an autosomal recessive pattern of inheritance. They can remain undetected as routine coagulation and platelet function tests are normal. A unique gain-of-function defect in fibrinolysis causes the Quebec platelet disorder (QPD) which is characterized by profibrinolytic platelets containing increased urokinase-type plasminogen activator (uPA) in the α-granules. A high index of suspicion based on clinical phenotype along with the availability of specialized hemostasis testing is required for timely and accurate diagnosis. Antifibrinolytic agents, such as tranexamic acid or ε-aminocaproic acid, are the mainstays of treatment which inhibit fibrinolysis by preventing the binding of plasminogen to fibrin and thereby stabilizing the fibrin clot. The purpose of this review is to summarize the pathogenesis, clinical phenotype, approaches to diagnosis and treatment for these three major disorders of fibrinolysis.

The relationship between pancreatic cancer and hypercoagulability: a comprehensive review on epidemiological and biological issues

It has long been recognised that pancreatic cancer induces a hypercoagulable state that may lead to clinically apparent thrombosis. Although the relationship between pancreatic cancer and hypercoagulability is well described, the underlying pathological mechanism(s) and the interplay between these pathways remain a matter of intensive study. This review summarises existing data on epidemiology and pathogenesis of thrombotic complications in pancreatic cancer with a particular emphasis on novel pathophysiological pathways. Pancreatic cancer is characterised by high tumoural expression of tissue factor, activation of leukocytes with the release of neutrophil extracellular traps, the dissemination of tumour-derived microvesicles that promote hypercoagulability and increased platelet activation. Furthermore, other coagulation pathways probably contribute to these processes, such as those that involve heparanase, podoplanin and hypofibrinolysis. In the era in which heparin and its derivatives—the currently recommended therapy for cancer-associated thrombosis—might be superseded by direct oral anticoagulants, novel data from mouse models of cancer-associated thrombosis suggest the possibility of future personalised therapeutic approaches. In this dynamic era for cancer-associated thrombosis, the discovery of novel prothrombotic and proinflammatory mechanisms will potentially uncover pharmacological targets to prevent and treat thrombosis without adversely affecting haemostasis.

Establishing a reference range for thromboelastograph parameters in the neonatal period

Introduction

Acquired coagulation disorders are a common cause of neonatal bleeding. The thromboelastograph (TEG) comprehensively assesses haemostatic processes in the body. Unfortunately, the reference range of TEG parameters in the neonatal period has not yet been evaluated, which limits the use of the TEG in neonates. In this study, we aimed to establish the reference range of TEG parameters for the neonatal period.

Methods

This study included 371 full‐term infants (≥37 weeks of gestation), and we divided these infants into three groups according to age as follows: 1, 2‐7 and 8‐28 days. We measured their peripheral blood using TEG, coagulation routine and platelet count tests. We analysed differences among the groups.

Results

The reference ranges for TEG parameters are presented as medians and reference ranges (2.5th and 97.5th percentiles) as follows: R (clot reaction time, seconds) 4.80 (2.80‐7.17), Angle (fibrin production rate) 69.90 (44.91‐78.89), K (clot kinetics, min) 1.40 (0.80‐4.50), MA (maximum amplitude, mm) 63.50(44.34‐74.66) and LY30 (lysis at 30 minutes, %) 0.10 (0.10‐6.95). There were significant differences in Angle, K, MA and LY30 values between the different neonatal day age groups.

Conclusion

This study preliminarily establishes a reference range for TEG parameters during the neonatal period. The age of a newborn had a large influence on TEG parameters. Additionally, we demonstrated a correlation between laboratory tests and TEG parameters for this age period. The reference values provided herein are meaningful for future studies.

Fibrinolysis during liver transplantation: analysis by the Thrombodynamics method

An issue in orthotopic liver transplantation (OLT) is the diagnosis of hyperfibrinolysis. The Thrombodynamics-4D assay (TD4D) is a videomicroscopy system allowing the dynamic analysis of fibrin clot. Fibrinolysis is highlighted by a change in clot intensity. The aim of this observational study was to evaluate the TD4D as a tool to diagnose fibrinolysis during OLT. Thirty consecutive patients were included. We studied a subset of 41 samples from 13 patients who demonstrated hyperfibrinolysis during OLT by global fibrinolytic capacity studied by the Lysis Timer (GFC/LT) and/or euglobulin clot lysis time (ECLT) and/or EXTEM maximum lysis (EXTEM ML) on ROTEM. Three samples exhibited fibrinolysis. They exhibited significantly shorter ECLT, higher lysis on EXTEM graphs, shorter GFC/LT clot lysis time and higher t-PA activity values. After adding urokinase, 13 samples exhibited fibrinolysis. In conclusion, TD4D allows the dynamic analysis of fibrin clot formation and lysis. It only recognises the most severe forms of hyperfibrinolysis during OLT.

What concentration of tranexamic acid is needed to inhibit fibrinolysis? A systematic review of pharmacodynamics studies

: Intravenous tranexamic acid (TXA) reduces death because of bleeding in patients with trauma and postpartum haemorrhage. However, in some settings intravenous injection is not feasible. To find different routes of administration, we first need to determine the minimal concentration of TXA in the blood that is required to inhibit fibrinolysis.We conducted a systematic review of in-vitro and in-vivo pharmacodynamics studies. We searched MEDLINE, EMBASE, OviSP, and ISI Web of Science from database inception to November 2017 for all in-vitro (including simulated clotting models) or in-vivo studies reporting the relationship between the TXA concentration in blood or plasma and any reliable measure of fibrinolysis.We found 21 studies of which 20 were in vitro and one was in vivo. Most in-vitro studies stimulated fibrinolysis with tissue plasminogen activator and measured fibrinolysis using viscoelastic, optical density, or immunological assays. TXA concentrations between 10 and 15 mg/l resulted in substantial inhibition of fibrinolysis, although concentrations between 5 and 10 mg/l were partly inhibitory.TXA concentrations of 10-15 mg/l may be suitable targets for pharmacokinetic studies, although TXA concentrations above 5 mg/l may also be effective.

Fibrinolysis in trauma patients: wide variability demonstrated by the Lysis Timer

Hyperfibrinolysis contributes to the pathophysiology of trauma-induced coagulopathy. At present, systematic administration of tranexamic acid (TXA) is recommended in all patients in the early phase of trauma. However, there is some debate regarding whether TXA is beneficial in all trauma patients. A rapid and accurate tool to diagnose hyperfibrinolysis may be useful for tailoring TXA treatment. We conducted a proof-of-concept study of consecutive adult trauma patients. A first blood sample was obtained at the time of pre-hospital care (T1). Patients received 1 g of TXA after T1. A second sample was obtained on arrival at the emergency unit (T2). We examined coagulation, fibrin and fibrinogen formation and degradation. Fibrinolysis was assessed by determining tissue plasminogen activator (t-PA) antigen and plasminogen activator inhibitor 1 (PAI-1) activity and global fibrinolysis capacity assay using a device developed by Hyphen BioMed: the Lysis Timer (GFC/LT). The study population consisted of 20 patients (42 ± 21 years, index of severity score 32 ± 21). Both coagulation and fibrinolysis were altered at T1. GFC/LT values exhibited hyperfibrinolysis only in five patients. Principal component analysis carried out at T1 showed two main axes of alteration. The major axis was related to coagulation, altered in all patients, while the second axis was related to fibrinolysis. GFC/LT was mainly influenced by PAI-1 activity while fibrin monomers were related to the severity of trauma. At T2, GFC/LT exhibited the marked effect of TXA on clot lysis time. In conclusion, GFC/LT demonstrated huge variation in the fibrinolytic response to trauma.