The place of viscoelastic testing in clinical practice

Laboratory Testing for Fibrinogen Disorders: From Routine Investigations to Research Studies

Congenital and acquired fibrinogen disorders often have heterogeneous clinical phenotypes and are challenging from a laboratory perspective. Fibrinogen determination using the Clauss method remains the gold standard, while the reproducibility and significance of the thrombin time and the reptilase time are limited. Molecular testing for causative mutations in fibrinogen genes is now recommended to confirm the diagnosis of congenital fibrinogen disorders. Research assays are used to evaluate alterations to fibrin formation and properties of plasma and purified fibrinogen-derived clots, characterized by fiber thickness, the number of branches, and pore sizes. Fibrin clot permeability (permeation, porosity) using a hydrostatic pressure system represents the most commonly used method for evaluating fibrin network density. Reduced clot permeability, which denotes the reduced size of an average pore in the network, results in tighter fibrin networks, typically associated with impaired susceptibility to lysis, leading to a thrombotic tendency. Biophysical properties of fibrin clots are largely assessed using rheometry, with atomic force microscopy and nanorheology being increasingly used in disease states. Thromboelastography and thromboelastometry, a simple modification of rheometry, have been used, mainly in intensive care units, for more than 50 years. Given growing evidence for altered fibrin clot properties in diseases with elevated risk of venous and arterial thromboembolism and in some bleeding disorders, further work on standardization and validation of the assessment of fibrin clot characteristics is needed. This review summarizes the current methods used to evaluate fibrinogen abnormalities in both diagnostic and research laboratories.

Comparison of Two Viscoelastic Testing Devices in a Parturient Population

Background: Viscoelastic hemostatic assays (VHAs) have become an integral diagnostic tool in guiding hemostatic therapy, offering new opportunities in personalized hemostatic resuscitation. This study aims to assess the interchangeability of ClotPro® and ROTEM® delta in the unique context of parturient women. Methods: Blood samples from 217 parturient women were collected at three timepoints. A total of 631 data sets were eligible for our final analysis. The clotting times were analyzed via extrinsic and intrinsic assays, and the clot firmness parameters A5, A10, and MCF were analyzed via extrinsic, intrinsic, and fibrin polymerization assays. In parallel, the standard laboratory coagulation statuses were obtained. Device comparison was assessed using regression and Bland-Altman plots. The best cutoff calculations were used to determine the VHA values corresponding to the established standard laboratory cutoffs. Results: The clotting times in the extrinsic and intrinsic assays showed notable differences between the devices, while the extrinsic and intrinsic clot firmness results demonstrated interchangeability. The fibrinogen assays revealed higher values in ClotPro® compared to ROTEM®. An ROC analysis identified VHA parameters with high predictive values for coagulopathy exclusion and yet low specificity. Conclusions: In the obstetric setting, the ROTEM® and ClotPro® parameters demonstrate a significant variability. Device- and indication-specific transfusion algorithms are essential for the accurate interpretation of measurements and adequate hemostatic therapy.

Viscoelastic Testing Methods

Viscoelastic testing methods examine the real-time formation of a clot in a whole blood sample, and include thromboelastography (TEG), rotational thromboelastometry (ROTEM), and several other testing platforms. They allow for concurrent assessment of multiple aspects of clotting, including plasmatic coagulation factors, platelets, fibrinogen, and the fibrinolytic pathway. This testing is rapid and may be performed at the point-of-care, allowing for prompt identification of coagulopathies to guide focused and rational administration of blood products as well as the identification of anticoagulant effect. With recent industry progression towards user-friendly, cartridge-based, portable instruments, viscoelastic testing has emerged in the 21st century as a powerful tool to guide blood transfusions in the bleeding patient, and to identify and treat both bleeding and thrombotic conditions in many operative settings, including trauma surgery, liver transplant surgery, cardiac surgery, and obstetrics. In these settings, the use of transfusion algorithms guided by viscoelastic testing data has resulted in widespread improvements in patient blood management as well as modest improvements in select patient outcomes. To address the increasingly wide adoption of viscoelastic methods and the growing number of medical and laboratory personnel tasked with implementing, performing, and interpreting these methods, this chapter provides an overview of the history, physiology, and technology behind viscoelastic testing, as well as a practical review of its clinical utility and current evidence supporting its use. Also included is a review of testing limitations and the contextual role played by viscoelastic methods among all coagulation laboratory testing.

Current and future strategies to monitor and manage coagulation in ECMO patients

Extracorporeal membrane oxygenation (ECMO) can provide life-saving support for critically ill patients suffering severe respiratory and/or cardiac failure. However, thrombosis and bleeding remain common and complex problems to manage. Key causes of thrombosis in ECMO patients include blood contact to pro-thrombotic and non-physiological surfaces, as well as high shearing forces in the pump and membrane oxygenator. On the other hand, adverse effects of anticoagulant, thrombocytopenia, platelet dysfunction, acquired von Willebrand syndrome, and hyperfibrinolysis are all established as causes of bleeding. Finding safe and effective anticoagulants that balance thrombosis and bleeding risk remains challenging. This review highlights commonly used anticoagulants in ECMO, including their mechanism of action, monitoring methods, strengths and limitations. It further elaborates on existing anticoagulant monitoring strategies, indicating their target range, benefits and drawbacks. Finally, it introduces several highly novel approaches to real-time anticoagulation monitoring methods including sound, optical, fluorescent, and electrical measurement as well as their working principles and future directions for research.

SHock-INduced Endotheliopathy (SHINE): A mechanistic justification for viscoelastography-guided resuscitation of traumatic and non-traumatic shock

Irrespective of the reason for hypoperfusion, hypocoagulable and/or hyperfibrinolytic hemostatic aberrancies afflict up to one-quarter of critically ill patients in shock. Intensivists and traumatologists have embraced the concept of SHock-INduced Endotheliopathy (SHINE) as a foundational derangement in progressive shock wherein sympatho-adrenal activation may cause systemic endothelial injury. The pro-thrombotic endothelium lends to micro-thrombosis, enacting a cycle of worsening perfusion and increasing catecholamines, endothelial injury, de-endothelialization, and multiple organ failure. The hypocoagulable/hyperfibrinolytic hemostatic phenotype is thought to be driven by endothelial release of anti-thrombogenic mediators to the bloodstream and perivascular sympathetic nerve release of tissue plasminogen activator directly into the microvasculature. In the shock state, this hemostatic phenotype may be a counterbalancing, yet maladaptive, attempt to restore blood flow against a systemically pro-thrombotic endothelium and increased blood viscosity. We therefore review endothelial physiology with emphasis on glycocalyx function, unique biomarkers, and coagulofibrinolytic mediators, setting the stage for understanding the pathophysiology and hemostatic phenotypes of SHINE in various etiologies of shock. We propose that the hyperfibrinolytic phenotype is exemplified in progressive shock whether related to trauma-induced coagulopathy, sepsis-induced coagulopathy, or post-cardiac arrest syndrome-associated coagulopathy. Regardless of the initial insult, SHINE appears to be a catecholamine-driven entity which early in the disease course may manifest as hyper- or hypocoagulopathic and hyper- or hypofibrinolytic hemostatic imbalance. Moreover, these hemostatic derangements may rapidly evolve along the thrombohemorrhagic spectrum depending on the etiology, timing, and methods of resuscitation. Given the intricate hemochemical makeup and changes during these shock states, macroscopic whole blood tests of coagulative kinetics and clot strength serve as clinically useful and simple means for hemostasis phenotyping. We suggest that viscoelastic hemostatic assays such as thromboelastography (TEG) and rotational thromboelastometry (ROTEM) are currently the most applicable clinical tools for assaying global hemostatic function-including fibrinolysis-to enable dynamic resuscitation with blood products and hemostatic adjuncts for those patients with thrombotic and/or hemorrhagic complications in shock states.

CREST: clinical bleeding and risk evaluation in hematology-oncology patients: a systematic review and meta-analysis of thromboelastography's role

Thrombocytopenia and bleeding are common complications of hematologic malignancies. Often, prophylactic platelets are administered to minimize bleeding risk, based on total platelet count (TPC). However, TPC is a poor predictor, and does not provide rapid information. This review presents a novel prospective in the use of point-of-care viscoelastic studies to assess bleeding risk and guide transfusion therapy in a haematological oncological population, where its use can be extended to a ward level as a bedside test. Monitoring TEG maximum amplitude trends may be useful to guide transfusion protocols, especially for patients with total platelet counts ranging 30-100 × 10 9 /l. Fibrinogen assessment in this group of patients may identify other blood components that require replacing to reduce bleeding risk. Normal maximum amplitude parameters for patients with low platelet counts can be a reassuring sign. This meta-analysis serves to remind the reader that absolute platelet quantity does not equate to the quality of clot formation.

In Vitro Evaluation of Real-Time Viscoelastic and Coagulation Properties of Various Classes of Topical Hemostatic Agents Using a Novel Contactless Nondestructive Technology

Hemorrhaging is the main cause of death among combat and civilian injuries and has significant clinical and economic consequences. Despite their vital roles in bleeding management, an optimal topical hemostatic agent (HA) has yet to be developed for a particular scenario. This is partly due to a lack of an overarching quantitative testing technology to characterize the various classes of HAs in vitro. Herein, the feasibility of a novel, contactless, and nondestructive technique to quantitatively measure the shear storage modulus (G') and clotting properties of whole blood in contact with different dosages of eight topical HAs, including particulates and gauze-like and sponge-like systems, was assessed. The real-time G'-time profiles of these blood/HA systems revealed their distinct biomechanical behavior to induce and impact coagulation. These were analyzed to characterize the clot initiation time, clotting rate, clotting time, and apparent stiffness of the formed clots (both immediately and temporally), which were correlated with their reported hemostatic mechanisms of action. Moreover, the HAs that worked independently from the natural blood clotting cascade were identified and quantified through this technology. In sum, this study indicated that the nondestructive nature of the technology may offer a promising tool for accurate, quantitative in vitro measurements of the clotting properties of various classes of HAs, which may be used to better predict their in vivo outcomes.

Is it possible to improve prediction of outcome and blood requirements in the severely injured patients by defining categories of coagulopathy?

PURPOSE

It has been suggested to define the Trauma-induced coagulopathy (TIC) with a PT_ratio threshold of 1.20. We hypothesized that a more pragmatic classification would grade severity according to the PT_ratio (or corresponding ROTEM clotting time: EXTEM-CT), and that this would correlate better with the need for blood products (BP) and prognosis.

METHODS

Retrospective analysis of prospectively collected data of 1076 severely injured patients admitted from 01/2011 to 12/2019 in a university hospital. To determine the number of TIC categories and the best PT_ratio or EXTEM-CT thresholds for mortality at 24-h, a modified Mazumdar approach was used. Multivariate regression analyses were done to describe the relationship between PT_ratio and ROTEM parameter subclasses with mortality.

RESULTS

Three thresholds were, respectively, identified for PT_ratio (1.20, 1.90 and 3.00) and EXTEM-CT (90 s, 130 s, 200 s). The following categories were defined for PT_ratio: ≤ 1.20 (No TIC), 1.21-1.90 (Moderate TIC), 1.91-3.00 (severe TIC), > 3.00 (major TIC); and for EXTEM-CT: < 91 s (no TIC), 91-130 s (moderate TIC), 131-200 s (severe TIC) and > 200 s (major TIC). We observed that when the PT_ratio (or EXTEM-CT) increased, mortality and BP requirements increased. After multiple adjustments, we observed that each subclass of PT_ratio and EXTEM-CT was independently associated with mortality at 24-h.

CONCLUSION

In this study, we have described a pragmatic classification of coagulopathy utilizing PT_ratio and EXTEM-CT where increasing severity was associated with prognosis and the amount of BP administered. This could allow clinicians to better predict the outcome and anticipate the need for blood products.

Hemostasis in neonatal ECMO

Extracorporeal membrane oxygenation (ECMO) is a life-saving support for cardio-respiratory function. Over the last 50 years, the extracorporeal field has faced huge technological progress. However, despite the improvements in technique and materials, coagulation problems are still the main contributor to morbidity and mortality of ECMO patients. Indeed, the incidence and survival rates of the main hemorrhagic and thrombotic complications in neonatal respiratory ECMO are relevant. The main culprit is related to the intrinsic nature of ECMO: the contact phase activation. The exposure of the human blood to the non-endothelial surface triggers a systemic inflammatory response syndrome, which chronically activates the thrombin generation and ultimately leads to coagulative derangements. Pre-existing illness-related hemostatic dysfunction and the peculiarity of the neonatal clotting balance further complicate the picture. Systemic anticoagulation is the management's mainstay, aiming to prevent thrombosis within the circuit and bleeding complications in the patient. Although other agents (i.e., direct thrombin inhibitors) have been recently introduced, unfractionated heparin (UFH) is the standard of care worldwide. Currently, there are multiple tests exploring ECMO-induced coagulopathy. A combination of the parameters mentioned above and the evaluation of the patient's underlying clinical context should be used to provide a goal-directed antithrombotic strategy. However, the ideal algorithm for monitoring anticoagulation is currently unknown, resulting in a large inter-institutional diagnostic variability. In this review, we face the features of the available monitoring tests and approaches, mainly focusing on the role of point-of-care (POC) viscoelastic assays in neonatal ECMO. Current gaps in knowledge and areas that warrant further study will also be addressed.

Which injured patients with moderate fibrinogen deficit need fibrinogen supplementation?

Background

In severely injured patients, fibrinogen supplementation is recommended when fibrinogenemia is < 1.5 g L⁻¹, but some teams have suggested to use higher thresholds (fibrinogenemia < 2.0 g L⁻¹ or FIBTEM clot amplitude at 5 min (A5) values < 11 mm). The goal of this study was to specify in patients with a moderate fibrinogen deficit (MFD) whether some admission characteristics would be associated with fibrinogen administration at 24 h.

Methods

Prospective analysis of retrospectively collected data from a trauma registry (01/2011–12/2019). MFD-C was defined by a fibrinogenemia 1.51–1.99 g L⁻¹ or the corresponding FIBTEM-A5 values (MFD-A5) that were determined from linear regression and ROC curve analysis. Administration of fibrinogen were described according to the following admission parameters: shock index (SI) > 1, hemoglobin level < 110 g L⁻¹ (HemoCue®), and base deficit > 5 mEq L⁻¹. Data are expressed as count (%), median [IQR].

Results

1076 patients were included in the study and 266 (27%) had MFD-C, among them, 122/266 (46%) received fibrinogen. Patients with MFD-C who received fibrinogen were more severely injured (ISS: 27 [19–36] vs. 24 [17–29]) and had more impaired vital signs (base deficit: 5.4 [3.6–7.8] vs. 3.8 [2.0–6.0]). Linear regression analysis found a positive correlation between fibrinogen level and FIBTEM-A5 (r: 0.805). For a fibrinogen level < 1.5 g L⁻¹ and < 2.0 g L⁻¹, FIBTEM-A5 thresholds were 6 mm (sensitivity 85%, specificity 83%, AUC: 0.934) and 9 mm (sensitivity 84%, specificity 69%, AUC: 0.874), respectively. MFD-A5 values (185 (27%) patients) were defined as a FIBTEM-A5 between 7 and 9 mm. More than 50% of MFD-C patients presenting a SI > 1, a hemoglobin level < 110 g L⁻¹, or a base deficit > 5.0 mEq L⁻¹ received fibrinogen. The relative risk [95% CI] for fibrinogen administration (SI > 1) were 1.39 [1.06–1.82] for MFD-C, and 2.17 [1.48–3.19] for MFD-A5. Results were not modified after adjustment on the ISS.

Conclusions

We have shown in this study an association between shock parameters and fibrinogen administration. Further studies are needed to determine how these parameters may be used to guide fibrinogen administration in trauma patients with MFD.

Monitoring of Enoxaparin during Hemodialysis Covered by Regional Citrate Anticoagulation in Acute Kidney Injury: A Prospective Cohort Study

Background: Current guidelines recommend the monitoring of anti-factor Xa (anti-Xa) levels to avoid an accumulation of low-molecular-weight heparins in patients with acute kidney injury, but there is no evidence on how to proceed with such monitoring during continuous renal replacement therapy. Against this background, we investigated the potential accumulation of enoxaparin administered subcutaneously for venous thromboembolism prophylaxis in critically ill patients during continuous renal replacement therapy covered by regional citrate anticoagulation. Methods: Anti-Xa levels were measured at baseline (≤12 h before renal replacement therapy) and on three consecutive days (A to C) when enoxaparin had reached trough levels. Supplementary testing included modified assays of rotational thromboelastometry known to be highly sensitive for low-molecular-weight heparins. Results: The 16 men and 13 women included were adults comparable in age, body mass index, thromboembolism risk assessment, and clinical severity of the disease. Throughout the four examinations, the median trough levels of anti-Xa remained below the detection limit of the test (<0.1 IU mL⁻¹), with interquartile ranges of <0.1 to 0.14 IU mL⁻¹ at baseline and <0.1 to 0.16 IU mL⁻¹ on days A/B/C. All rotational thromboelastometry parameters of clot initiation and clot formation dynamics did not significantly change from baseline to day C. Conclusions: Neither anti-Xa levels nor modified assays of rotational thromboelastometry revealed any accumulation of enoxaparin administered for thromboprophylaxis during continuous renal replacement therapy covered by regional citrate anticoagulation. Although generally recommended in patients with acute kidney injury, monitoring of anti-Xa levels should be questioned in this defined setting.

Viscoelastic Hemostatic Assays for Postpartum Hemorrhage

This article discusses the importance and effectiveness of viscoelastic hemostatic assays (VHAs) in assessing hemostatic competence and guiding blood component therapy (BCT) in patients with postpartum hemorrhage (PPH). In recent years, VHAs such as thromboelastography and rotational thromboelastometry have increasingly been used to guide BCT, hemostatic adjunctive therapy and prohemostatic agents in PPH. The three pillars of identifying hemostatic competence include clinical observation, common coagulation tests, and VHAs. VHAs are advantageous because they assess the cumulative contribution of all components of the blood throughout the entire formation of a clot, have fast turnaround times, and are point-of-care tests that can be followed serially. Despite these advantages, VHAs are underused due to poor understanding of correct technique and result interpretation, a paucity of widespread standardization, and a lack of large clinical trials. These VHAs can also be used in cases of uterine atony, preeclampsia, acute fatty liver of pregnancy, amniotic fluid embolism, placental abruption, genital tract trauma, surgical trauma, and inherited and prepartum acquired coagulopathies. There exists an immediate need for a point-of-care test that can equip obstetricians with rapid results on developing coagulopathic states. The use of VHAs in predicting and treating PPH, although in an incipient state, can fulfill this need.

Perioperative Viscoelastic Assay Use for Monitoring Coagulation Among US Liver Transplantation Centers

BACKGROUND

Viscoelastic assay has been used in liver transplantation since 1985 and shown to be beneficial in detecting coagulopathy and to guide transfusion. The objective of this study was to review and evaluate the current uses of viscoelastic assay among US liver transplantation programs.

METHODS

Anesthesia program directors at all 137 liver transplantation centers in the United States were contacted via email and asked to complete a 21-item survey. The primary outcome measure was the percentage of viscoelastic assay used in the perioperative management of liver transplantation. Secondary outcome measures were institutional demographics, physician training level, and device demographics.

RESULTS

Sixty-one of 137 (46%) centers responded. Liver transplantations were performed in the university setting at 48 of the 61 centers (77%), with a modal value of 11 to 50 liver transplantations a year and 74% in adult patients only. Most of the institutions (n = 57, 92%) had access to either rotational thromboelastometry or thrombelastography during liver transplantation. Most centers (n = 54; 87%) also used viscoelastic monitoring routinely (>60% of the time), including 42 (67.7%) that always used viscoelastic assay intraoperatively during liver transplantation. Thirty-five centers (59%) used it preoperatively, and 51 (84%) used it postoperatively. Most viscoelastic assay users (68%) learned how to use it through self-education and 10.5% learned during their fellowship or from a superuser or colleagues.

CONCLUSION

Currently, viscoelastic monitoring is widely available and routinely used in most US liver transplantation centers regardless of university or private practice setting, but training in it is limited. Only 21.1% of respondents reported that they received any type of official training in viscoelastic assay interpretation.

Establishing reference ranges of cord blood: point-of-care hemostatic function assessment in preterm and term neonates

BACKGROUND

Thrombelastometry, allowing timely assessment of global hemostatic function, is increasingly used to guide hemostatic interventions in bleeding patients. Reference values are available for adults and children, including infants but not neonates immediately after birth.

METHODS

Neonates were grouped as preterm (30 + 0 to 36 + 6 weeks/days) and term (37 + 0 to 39 + 6 weeks/days). Blood samples were drawn from the umbilical cord immediately after cesarean section and analyzed by thrombelastometry. Reference ranges were determined for the extrinsic and intrinsic coagulation pathways, fibrin polymerization, and hyperfibrinolysis detection.

RESULTS

All extrinsically activated test parameters, but maximum lysis (P = 0.139) differed significantly between both groups (P ≤ 0.001). Maximum clot firmness in the fibrin polymerization test was comparable (P = 0.141). All intrinsically activated test parameters other than coagulation time (P = 0.537) and maximum lysis (P = 0.888) differed significantly (P < 0.001), and so did all aprotinin-related test parameters (P ≤ 0.001) but maximum lysis (P = 0.851).

CONCLUSIONS

This is the first study to identify reference ranges for thrombelastometry in preterm and term neonates immediately after birth. We also report differences in clot initiation and clot strength in neonates born <37 versus ≤40 weeks of gestation, mirroring developmental hemostasis.

IMPACT

Impact: This prospective observational study is the first to present reference ranges in preterm and term infants for all types of commercially available tests of thrombelastometry, notably also including the fibrin polymerization test.

IMPORTANCE

Viscoelastic coagulation assays such as thrombelastometry have become integral to the management of perioperative bleeding by present-day standards. Reference values are available for adults, children, and infants but not for neonates. Key message: Clot initiation and formation was faster and clot strength higher in the term than in the preterm group. Parameters of thrombelastometry obtained from cord blood do not apply interchangeably to preterm and term neonates.

Thrombin Generation and Platelet Function in ICU Patients Undergoing CVVHD Using Regional Citrate Anticoagulation

Background: To investigate pro- and anticoagulant alterations in uremic critically ill patients prior to and during continuous renal replacement therapy. In addition to the conventional thrombin generation assay (TGA), we performed a thrombomodulin-modified variant to better elucidate procoagulant imbalances. Platelet function was determined via multiple electrode aggregometry (MEA) to round off hemostatic analysis.

Methods: We prospectively enrolled patients at surgical intensive care units (ICU) with acute kidney injury undergoing continuous veno-venous hemodialysis using regional citrate anticoagulation. TGA and platelet function testing were performed at baseline (≤ 12 h prior to continuous renal replacement therapy) and on 3 consecutive days (day A–C) of extracorporeal therapy.

Results: We did not observe significant changes in thrombin generation after start or during renal replacement therapy. Ratios of endogenous thrombin potential in patients were significantly increased (p < 0.001) compared to standardized plasma of healthy donors confirming the assumed procoagulant alterations in ICU patients. Test results of the conventional TGA differed significantly (p < 0.05) from those of the thrombomodulin-modified assay. The area under the curve remained below MEA reference values during the entire observation period, indicating a persistent reduction in platelet function.

Conclusion: In summary, in-depth analysis using standard and modified TGA, as well as calculation of endogenous thrombin potential (ETP) ratios, revealed no further aggravation of the procoagulatory shift in the critically ill patient during CVVHD using regional citrate anticoagulation. MEA ruled out the potential impact of platelets.

Clinical Trial Registration: German Clinical Trials Register (DRKS00004336), 29 August 2012; www.drks.de.

Barriers and facilitators to implementing evidence based bleeding management in Australian Cardiac Surgery Units: a qualitative interview study analysed with the theoretical domains framework and COM-B model

Background

Bleeding during cardiac surgery is a common complication that often requires the transfusion of blood products. The combination of bleeding and blood product transfusion incrementally increases adverse outcomes including infection and mortality. Following bleeding management guideline recommendations could assist with minimising risk but adherence is not high, and the cause for lack of adherence is not well understood. This study aimed to identify barriers and facilitators to practicing and implementing evidenced-based intra-operative, bleeding management in Australian cardiac surgery units.

Methods

We used a qualitative descriptive design to conduct semi-structured interviews with Australian cardiac surgeons, anaesthetists and perfusionists. The Theoretical Domains Framework (TDF) was utilised to guide interviews and thematically analyse the data. Categorised data were then linked with the three key domains of the COM-B model (capability, opportunity, motivation - behaviour) to explore and understand behaviour.

Results

Seventeen interviews were completed. Nine of the 14 TDF domains emerged as significant. Analysis revealed key themes to improving capability included, standardisation, monitoring, auditing and feedback of data and cross discipline training. Opportunity for change was improved with interpersonal and interdepartmental collaboration through shared goals, and more efficient and supportive processes allowing clinicians to navigate unfamiliar business and financial models of health care. Results suggest as individuals, clinicians had the motivation to make change and healthcare organisations have an obligation and a responsibility to partner with clinicians to support change and improve goal directed best practice.

Conclusion

Using a theory-based approach it was possible to identify factors which may be positively or negatively influence clinicians ability to implement best practice bleeding management in Australian cardiac surgical units.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12913-021-06269-8.

Fibrinolytic shutdown diagnosed with rotational thromboelastometry represents a moderate form of coagulopathy associated with transfusion requirement and mortality: A retrospective analysis

BACKGROUND

Viscoelastic techniques have made it possible to describe specific fibrinolytic phenotypes (physiological, hyperfibrinolysis and shutdown) and to establish a relationship of these phenotypes with outcome. However, there remains a debate as to whether shutdown is a state of hypercoagulability or rather a coagulopathy with moderate fibrinolysis and fibrinogen consumption.

OBJECTIVES

Our objectives were to describe the relationship between fibrinolytic phenotypes and outcomes, and to report the effects of tranexamic acid (TXA) administration.

DESIGN

This was a retrospective analysis of prospectively acquired data from a trauma registry.

SETTING

An academic level 1 trauma centre in the Lyon Region, from March 2011 to December 2016.

PATIENTS

We included all injured patients who had a rotational thromboelastometry analysis at admission. Fibrinolytic phenotypes were determined according to the maximum lysis: shutdown less than 3%, physiological 3 to 15%, hyperfibrinolysis more than 15%.

MAIN OUTCOME MEASURE

Mortality at 24 h and at hospital discharge.

RESULTS

During the study period, 473 patients were included with the following phenotypes: physiological (344 patients, 73%), shutdown (107 patients, 23%) and hyperfibrinolysis (22 patients, 5%). There was an increase in injury severity, prothrombin time ratio, fibrin degradation products and transfusion requirements from the physiological to the shutdown and hyperfibrinolysis phenotypes. Prehospital TXA administration increased the rate of shutdown and decreased the maximum lysis value at admission. After adjustment, multivariate analysis showed that fibrinolytic phenotypes, but not TXA, were independently associated with an increased risk of early death and death before hospital discharge: shutdown [odds ratio (95% confidence interval)] 2.4 (1.2 to 4.8) and hyperfibrinolysis 67.9 (7.4 to 624.2).

CONCLUSION

The results of the current study suggest that shutdown, which is associated with injury severity and mortality, probably reflects a moderate form of coagulopathy and fibrinolysis rather than a hypercoagulopathy. Therefore, the observation of shutdown fibrinolysis on thromboelastography/rotational thromboelastometry should not lead to withholding but rather to the administration of TXA.

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.

Perioperative Management of Severe Acquired Coagulopathy in Patients with Left Ventricular Assist Device—a Literature Review and Expert Recommendations

Purpose of This Review

The implantation of a left ventricular assist device (LVAD) is associated with high hemorrhage-related re-exploration rates. Improved management of coagulopathy may improve patient outcome. The optimal management of acquired coagulopathy in LVAD patients needing urgent non-cardiac surgery needs to be defined. We aim to review risk factors for perioperative bleeding and diagnosis and management of LVAD-associated coagulopathy and to provide expert recommendations for clinical practice.

Recent Findings

In patients undergoing LVAD implantation, the severity of coagulopathy is directly related to the severity of the cardiac failure. The evidence from current literature for optimal management of acquired coagulopathy during and after LVAD implantation is sparse. The traditional transfusion strategy of replacing coagulation factors with fresh frozen plasma involves the risk of transfusion-associated circulatory overload. Current recommendations for targeted replacement of coagulation factors with 4-factor prothrombin concentrate and fibrinogen concentrate in cardiac surgery may be translated in this special setting.

Summary

The targeted, point-of-care use of concentrated coagulation factors may improve treatment of severe acquired coagulopathy during LVAD implantation and in LVAD patients needing urgent non-cardiac surgery.

Comparison of Thromboelastography and Conventional Coagulation Tests in Patients With Severe Liver Disease

OBJECTIVE

Thromboelastography (TEG) may provide rapid and clinically important coagulation information in acutely ill patients with chronic liver disease (CLD). Our objective was to describe the relationship between TEG and conventional coagulation tests (CCTs), which has not been previously explored in this population.

METHODS

In acutely ill patients with severe CLD (Child-Pugh score > 9, category C), we conducted a prospective observational study investigating coagulation assessment as measured by both CCTs and TEG. We used quantile regression to explore 30 associations between TEG parameters and corresponding CCTs. We compared TEG and CCT measures of coagulation initiation, clot formation, clot strength, and fibrinolysis.

RESULTS

We studied 34 patients on a total of 109 occasions. We observed inconsistent associations between TEG and CCT measures of coagulation initiation: TEG (citrated kaolin [CK] assay) standard reaction time and international normalized ratio: R ² = 0.117 (P = .044). Conversely, there were strong and consistent associations between tests of clot formation: TEG (CK) kinetics time and fibrinogen: R ² = 0.202 (P < .0001) and TEG (CK) α angle and fibrinogen 0.263 (P < .0001). We also observed strong associations between tests of clot strength, specifically TEG MA and conventional fibrinogen levels, across all TEG assays: MA (CK) and fibrinogen: R ² = 0.485 (P < .0001). There were no associations between TEG and D-dimer levels.

CONCLUSIONS

In acutely ill patients with CLD, there are strong and consistent associations between TEG measures of clot formation and clot strength and conventional fibrinogen levels. There are weak and/or inconsistent associations between TEG and all other conventional measures of coagulation.

Hemostasis in Coronavirus Disease 2019-Lesson from Viscoelastic Methods: A Systematic Review

Hemostatic unbalance is often observed in patients with coronavirus disease 2019 (COVID-19), and patients with severe disease are at high risk of developing thromboembolic complications. Viscoelastic methods (VEMs), including thrombelastography (TEG) and thromboelastometry (TEM), provide data on the nature of hemostatic disturbance. In this systematic review, we assessed the performance of TEG and TEM in the assessment of blood coagulation and fibrinolysis in patients with COVID-19. PubMed, Scopus, Web of Science Core Collection, medRxiv, and bioRxiv were systematically searched for clinical studies evaluating TEG and/or TEM variables in COVID-19 individuals. Ten studies, with a total of 389 COVID-19 patients, were included, and VEMs were performed in 292 of these patients. Most patients (90%) presented severe COVID-19 and required mechanical ventilation. TEG and TEM variables showed that these patients displayed hypercoagulability and fibrinolysis shutdown, despite the use of appropriate thromboprophylaxis. However, the mechanism underlying these phenomena and their clinical significance in COVID-19 patients who developed thrombosis are still not clear. Further studies are warranted if VEMs might help to identify those at highest risk of thrombotic events and who therefore may derive the greatest benefit from antithrombotic therapy.

Massive Gastrointestinal Hemorrhage

Massive gastrointestinal hemorrhage is a life-threatening condition that can result from numerous causes and requires skilled resuscitation to decrease patient morbidity and mortality. Successful resuscitation begins with placement of large-bore intravenous or intraosseous access; early blood product administration; and early consultation with a gastroenterologist, interventional radiologist, and/or surgeon. Activate a massive transfusion protocol when initial red blood cell transfusion does not restore effective perfusion or the patient's shock index is greater than 1.0. Promptly reverse coagulopathies secondary to oral anticoagulant or antiplatelet use. Use thromboelastography or rotational thromboelastometry to guide further transfusions. Secure a definitive airway and minimize aspiration.

The role of platelets in bleeding in patients with thrombocytopenia and hematological disease

This review evaluates the role of platelets in bleeding risk among patients with hematological disease and thrombocytopenia. Platelets are pivotal in primary hemostasis, and possess non-hemostatic properties involved in angiogenesis, tissue repair, inflammation and metastatis. Also, platelets safeguard vascular integrity in inflamed vessels. Overall, bleeding risk depends on the underlying disease, and patients with cancer and platelet count <6-10 × 109/L have a markedly increased bleeding risk, while the platelet count does not correlate with bleeding risk at higher platelet counts. Other factors might affect platelet properties and thus bleeding risk, for example, drugs, low hematocrit, coagulation system impairments or transfusion of dysfunctional donor platelets. For patients with leukemia and immune thrombocytopenia, reduced platelet activation, platelet aggregation, or thrombopoiesis, reflected by the reduced presence of reticulated platelets, are associated with bleeding phenotype. However, mechanistic insight into the cause of reduced platelet function in different thrombocytopenic conditions is sparse, except for some inherited platelet disorders. Promising tools for platelet function studies in thrombocytopenia are flow cytometry and biomarker studies on platelet constituents. An important message from this current paper is that bleeding risk assessment must be tailored to specific patient populations and cannot be applied broadly to all patients with thrombocytopenia.

Trauma-Induced Coagulopathy and Massive Bleeding: Current Hemostatic Concepts and Treatment Strategies

Hemorrhage after trauma remains a significant cause of preventable death. Trauma-induced coagulopathy (TIC) at the time of hospital admission is associated with an impaired outcome. Rather than a universal phenotype, TIC represents a complex hemostatic disorder, and standard coagulation tests are not designed to adequately reflect the complexity of TIC. Viscoelastic testing (VET) has gained increasing interest for the characterization of TIC because it provides a more comprehensive depiction of the coagulation process. Thus, VET has been established as a point-of-care-available hemostatic monitoring tool in many trauma centers. Damage-control resuscitation and early administration of tranexamic acid provide the basis for treating TIC. To improve survival, ratio-driven massive transfusion protocols favoring early and high-dose plasma transfusion have been implemented in many trauma centers around the world. Although plasma contains all coagulation factors and inhibitors, only high-volume plasma transfusion allows for adequate substitution of lacking coagulation proteins. However, high-volume plasma transfusion has been associated with several relevant risks. In some European trauma facilities, a more individualized hemostatic therapy concept has been implemented. The hemostatic profile of the bleeding patient is evaluated by VET. Subsequently, goal-directed hemostatic therapy is primarily based on coagulation factor concentrates such as fibrinogen concentrate or prothrombin complex concentrate. However, a clear difference in survival benefit between these two treatment strategies has not yet been shown. This concise review aims to summarize current evidence for different diagnostic and therapeutic strategies in patients with TIC.

Post-TBI splenectomy may exacerbate coagulopathy and platelet activation in a murine model

INTRODUCTION

Traumatic brain injury (TBI) induces acute hypocoagulability, subacute hypercoagulability, and persistently elevated risk for thromboembolic events. Splenectomy is associated with increased mortality in patients with moderate or severe TBI. We hypothesized that the adverse effects of splenectomy in TBI patients may be secondary to the exacerbation of pathologic coagulation and platelet activation changes.

METHODS

An established murine weight-drop TBI model was utilized and a splenectomy was performed immediately following TBI. Sham as well as TBI and splenectomy alone mice were used as injury controls. Mice were sacrificed for blood draws at 1, 6, and 24 h, as well as 7 days post-TBI. Viscoelastic coagulation parameters were assessed by rotational thromboelastometry (ROTEM) and platelet activation was measured by expression of P-selectin via flow cytometry analysis of platelet rich plasma samples.

RESULTS

At 6 h following injury, TBI/splenectomy demonstrated hypocoagulability with prolonged clot formation time (CFT) compared to TBI alone. By 24 h following injury, TBI/splenectomy and splenectomy mice were hypercoagulable with a shorter CFT, a higher alpha angle, and increased MCF, despite a lower percentage of platelet contribution to clot compared to TBI alone. However, only the TBI/splenectomy continued to display this hypercoagulable state at 7 days. While TBI/splenectomy had greater P-selectin expression at 1-h post-injury, TBI alone had significantly greater P-selectin expression at 24 h post-injury compared to TBI/splenectomy. Interestingly, P-selectin expression remained elevated only in TBI/splenectomy at 7 days post-injury.

CONCLUSION

Splenectomy following TBI exacerbates changes in the post-injury coagulation state. The combination of TBI and splenectomy induces an acute hypocoagulable state that could contribute to an increase in intracranial bleeding. Subacutely, the addition of splenectomy to TBI exacerbates post-injury hypercoagulability and induces persistent platelet activation. These polytrauma effects on coagulation may contribute to the increased mortality observed in patients with combined brain and splenic injuries.

Assessing TEG6S reliability between devices and across multiple time points: A prospective thromboelastography validation study

The TEG6S is a novel haemostasis analyser utilising resonance technology. It offers potentially greater coagulation information and ease of use, however has not been independently validated in a clinical setting. We aimed to determine if the TEG6S is reliable between devices and across time points. We performed a prospective observational study with ethical approval. For interdevice reliability, we performed simultaneous analysis on two TEG6S devices on 25 adult ICU patients. For time point reliability, we performed repeated sampling across five different time points on 15 adult participants. Blood was collected with informed consent, or as standard care, before four-channel citrated kaolin analysis. We observed almost perfect interdevice reliability across all TEG parameters. The Lin's concordance correlation coefficients (95% CI, major axis regression slope, intercept) were R-time: 0.96 (0.92-0.99, 0.88, 0.57); K-time: 0.93 (0.87-0.98, 1.07, 0.00); Alpha Angle: 0.87 (0.78-0.96, 1.20, -14.10); Maximum Amplitude: 0.99 (0.98-0.99, 1.02, -1.38); Clot Lysis: 0.89 (0.82-0.97, 1.20, 0.07). Additionally, we observed moderate-to-high reliability across time points. Demonstrating almost perfect agreement across different devices and moderate-to-high reliability across multiple time points, suggests the TEG6S platform can be used with haemostatic accuracy and generalisability. This has potentially significant implications for clinical practice and multi-site research programs.

Viscoelastic haemostatic assays and fibrinogen in paediatric acute traumatic coagulopathy: A comprehensive review

OBJECTIVE

Haemorrhage in paediatric trauma remains a significant cause of morbidity and mortality. Over recent years there has been increasing attention to the role of fibrinogen in traumatic haemorrhage and the association of low fibrinogen levels with poor patient outcomes. In addition, there has been a move towards using viscoelastic haemostatic assays (VHAs) to rapidly assess coagulation status and guide clinicians in the replacement of coagulation factors, including fibrinogen. In the paediatric population, there has been limited uptake of these principles and a paucity of data to support a change in practice. This paper summarises the available evidence in the published literature through a systematic review, presented in narrative format.

RESULTS

There is limited high-quality prospective data on the use of VHA in the management of acute traumatic coagulopathy in the paediatric population. While the use of fibrinogen early in major haemorrhage is becoming standard practice, there are currently no randomised prospective studies comparing fibrinogen concentrate to cryoprecipitate.

CONCLUSIONS

The early identification of hypo-fibrinogenemia and acute traumatic coagulopathy in paediatric trauma using VHA testing and subsequent early fibrinogen replacement with a concentrated off the shelf product is an attractive treatment option. However, there is currently insufficient high-level evidence to support the use of fibrinogen concentrate over cryoprecipitate in the paediatric trauma population. Pilot studies currently under way will go some way to addressing this important knowledge gap, and facilitate the design of larger definitive multi-centre randomised trials.

Hemostatic Testing in Critically Ill Infants and Children

Children with critical illness frequently manifest imbalances in hemostasis with risk of consequent bleeding or pathologic thrombosis. Traditionally, plasma-based tests measuring clot formation by time to fibrin clot generation have been the "gold standard" in hemostasis testing. However, these tests are not sensitive to abnormalities in fibrinolysis or in conditions of enhanced clot formation that may lead to thrombosis. Additionally, they do not measure the critical roles played by platelets and endothelial cells. An added factor in the evaluation of these plasma-based tests is that in infants and young children plasma levels of many procoagulant and anticoagulant proteins are lower than in older children and adults resulting in prolonged clot generation times in spite of maintaining a normal hemostatic "balance." Consequently, newer assays directly measuring thrombin generation in plasma and others assessing the stages hemostasis including clot initiation, propagation, and fibrinolysis in whole blood by viscoelastic methods are now available and may allow for a global measurement of the hemostatic system. In this manuscript, we will review the processes by which clots are formed and by which hemostasis is regulated, and the rationale and limitations for the more commonly utilized tests. We will also discuss selected newer tests available for the assessment of hemostasis, their "pros" and "cons," and how they compare to the traditional tests of coagulation in the assessment and management of critically ill children.

Application of Piezo-Based Measuring System for Evaluation of Nucleic Acid-Based Drugs Influencing the Coagulation

During open-heart surgery, the status of hemostasis has to be constantly monitored to quickly and reliably detect bleeding or coagulation disorders. In this study, a novel optimized piezo-based measuring system (PIEZ) for rheological monitoring of hemostasis was established. The applicability of the PIEZ for the evaluation of nucleic acid-based drugs influencing coagulation was analyzed. Thrombin aptamers such as NU172 might be used during extracorporeal circulation (ECC) in combination with a reduced heparin concentration or for patients with heparin-induced thrombocytopenia (HIT). Therefore, the effect of the coagulation inhibiting thrombin aptamer NU172 and the abrogation by its complementary antidote sequence (AD) were investigated by this rheological PIEZ system. After the addition of different NU172 concentrations, the coagulation of fresh human blood was analyzed under static conditions and using an in vitro rotation model under dynamic conditions (simulating ECC). The clotting times (CTs) detected by PIEZ were compared to those obtained with a medical reference device, a ball coagulometer. Additionally, after the circulation of blood samples for 30 min at 37 °C, blood cell numbers, thrombin markers (thrombin-antithrombin III (TAT) and fibrinopeptide A (FPA)) and a platelet activation marker (β-thromboglobulin (β-TG)) were analyzed by enzyme-linked immunosorbent assays (ELISAs). The increase of NU172 concentration resulted in prolonged CTs, which were comparable between the reference ball coagulometer and the PIEZ, demonstrating the reliability of the new measuring system. Moreover, by looking at the slope of the linear regression of the viscous and elastic components, PIEZ also could provide information on the kinetics of the coagulation reaction. The shear viscosity at the end of the measurements (after 300 s) was indicative of clot firmness. Furthermore, the PIEZ was able to detect the abrogation of coagulation inhibition after the equimolar addition of NU172 aptamer´s AD. The obtained results showed that the established PIEZ is capable to dynamically measure the hemostasis status in whole blood and can be applied to analyze nucleic acid-based drugs influencing the coagulation.

Application of thromboelastography to evaluate the effect of different routes administration of tranexamic acid on coagulation function in total hip arthroplasty

Background

Tranexamic acid (TXA) is widely used to reduce blood loss and transfusion rates in total hip arthroplasty(THA). Thromboelastography, which can monitor coagulation changes from clotting to fibrinolysis dynamically. In this study, thromboelastography was used to assess the dynamic changes in the coagulation of patients who underwent THA with the administration of TXA.

Methods

This randomized controlled trial consisted of 207 consecutive patients who underwent primary total hip arthroplasty. Patients were randomized into three groups: topical-TXA group received a topical application of TXA, IV-TXA group received an intravenous injection of TXA, and control group. Thromboelastography was performed 1 day before surgery and first, fourth, seventh days after surgery. The primary outcomes were thromboelastography parameters, the rates of deep vein thrombosis(DVT), and pulmonary embolism(PE). Secondary outcomes included perioperative blood loss, transfusion rates, and other perioperative complications.

Results

The mean calculated total blood loss in the Topical-TXA group were 832.7 ± 279.84 ml and 834.8 ± 322.94 ml in the IV-TXA group, which were significantly reduced (p < 0.05) compared with control groups at 1093.3 ± 379.7 ml. There were no significant differences between topical-TXA and IV-TXA groups in total blood loss or transfusion rates. K and R have reached a nadir from preoperative levels to 4th day postoperatively and then began to increase.α angle and CI peaked from preoperative levels to the fourth day postoperatively and then began to decline.IV-TXA significantly (p < 0.05) promoted coagulation levels compared with topical-TXA and control groups in the early postoperative period. Almost no significant differences were observed between topical-TXA and control groups in thromboelastography parameters.No significant differences were observed in the incidence of thromboembolic complications and other perioperative complications.

Conclusions

The topical administration of TXA had the same hemostatic effect as intravenous injection tranexamic acid. Coagulation function peaked on 4th day postoperatively and then began to decline. IV-TXA was more enhanced coagulation functions compared with topical-TXA.

Relationship of Coagulopathy and Platelet Dysfunction to Transfusion Needs After Traumatic Brain Injury

BACKGROUND

Coagulopathy and platelet dysfunction commonly develop after traumatic brain injury (TBI). Thromboelastography (TEG) and platelet function assays (PFAs) are often performed at the time of admission; however, their roles in assessing post-TBI coagulopathy have not been investigated. We hypothesized that compared to blunt TBI, penetrating TBI would (1) demonstrate greater coagulopathy by TEG, (2) be associated with abnormal PFA results, and (3) require more blood product transfusions.

METHODS

We performed a retrospective study of patients admitted to the neuroscience intensive care unit of a level 1 trauma center from 2013 to 2015 with head Abbreviated Injury Scale ≥3. Patients were compared by mechanism of injury (blunt vs. penetrating). Admission demographics, injury characteristics, and laboratory parameters were evaluated. VerifyNow^® Aspirin and P2Y12 tests were used for platelet function analysis.

RESULTS

Five hundred and thirty-four patients were included in the analysis. There were no differences between groups in platelet count or international normalized ratio; however, patients with penetrating TBI were more coagulopathic by TEG, with all of the TEG parameters being significantly different except for R time. Patients with penetrating head trauma were not more likely than their blunt counterparts to have abnormal PFA results, and PFA results did not correlate with any TEG parameter in either group. The penetrating cohort received more units of blood products in the first 4 and 24 h than the blunt cohort.

CONCLUSIONS

Patients presenting with penetrating TBI demonstrated increased coagulopathy compared to those with blunt TBI as measured by TEG and need for transfusion. PFA results did not correlate with TEG findings in this population.

Use of Viscoelastography in Malignancy-Associated Coagulopathy and Thrombosis: A Review

The relationship between malignancy and coagulopathy is one that is well documented yet incompletely understood. Clinicians have attempted to quantify the hypercoagulable state produced in various malignancies using common coagulation tests such as prothrombin time, activated partial thromboplastin time, and platelet count; however, due to these tests' focus on individual aspects of coagulation during one specific time point, they have failed to provide clinicians the complete picture of malignancy-associated coagulopathy (MAC). Viscoelastic tests (VETs), such as thromboelastography (TEG) and rotational thromboelastometry (ROTEM), are whole blood analyses that have the advantage of providing information related to the cumulative effects of plasma clotting factors, platelets, leukocytes, and red cells during all stages of the coagulation and fibrinolytic processes. VETs have gained popularity in the care of trauma patients to objectively measure trauma-induced coagulopathy (TIC), but the utility of VETs remains yet unrealized in many other medical specialties. The authors discuss the similarities and differences between TIC and MAC, and propose a mechanism for the hypercoagulable state of MAC that revolves around the thrombomodulin-thrombin complex as it switches between activating the protein C anticoagulation pathway or the thrombin activatable fibrinolysis inhibitor coagulation pathway. Additionally, they review the current literature on the use of TEG and ROTEM in patients with various malignancies. Although limited research is currently available, early results demonstrate the utility of both TEG and ROTEM in the prediction of hypercoagulable states and thromboembolic complications in oncologic patients.

Mixing Studies in Patients With Prolonged Activated Partial Thromboplastin Time or Prothrombin Time

BACKGROUND

Patients presenting for surgery may have isolated or combined prolonged activated partial thromboplastin time (aPTT) and/or prothrombin time (PT). In patients not receiving anticoagulants or with no identifiable cause for abnormal clot formation, a mixing study is performed. The index of circulating anticoagulant (ICA) has been used to predict the presence of an inhibitor, usually a lupus anticoagulant.

METHODS

We retrospectively reviewed the results of mixing studies performed at Northwestern Memorial Hospital, between January 1, 2010 and February 29, 2012. We determined the number of samples that normalized or remained prolonged, the clotting factors associated with prolonged test results, and the presence of coagulation inhibitors. We calculated the ICA in the samples with prolonged aPTT and PT to determine its ability to predict a lupus anticoagulant. The primary comparison of interest was the diagnostic utility of the ICA at cutoff values of 11% for predicting the presence of lupus anticoagulant.

RESULTS

There were 269 mixing studies performed: 131 samples with prolonged aPTT; 95 with prolonged PT; and 43 with both prolonged aPTT and prolonged PT. Of the samples with a prolonged aPTT, 55 of 131 (42%) normalized, 36 of 131 (27%) partially corrected, and 40 of 131 (31%) remained prolonged. Thirty-three of 95 samples (35%) with prolonged PT normalized, while 62 of 95 (65%) remained prolonged. Eight of 43 (19%) mixing studies of patients with prolonged PT and aPTT normalized; the aPTT normalized, but the PT remained prolonged in 17 of 43 (39%); the PT normalized, but the aPTT remained prolonged in 7 of 43 (16%); and both tests remained prolonged in 11 of 43 (26%) samples. Prolongations in the aPTT were primarily associated with low activities of CF XII, while the majority of the prolongations in PT were secondary to low activities in CF VII. Combined prolongations were secondary to deficiencies in both the intrinsic and extrinsic as well as the common pathways. An ICA >11% had 100% (95% CI, 59%-100%) sensitivity, 53% (95% CI, 35%-70%) specificity, and 77% (95% CI, 62%-92%) accuracy in predicting the presence of lupus anticoagulant in patients with prolonged aPTT.

CONCLUSIONS

Normalization of the aPTT and PT in a mixing study was associated with low clotting factor activity. The ICA may be helpful in predicting the presence of a lupus anticoagulant. As anesthesiologists take ownership of the perioperative surgical home, we need to understand the clinical implications of the results of mixing studies.

Thromboelastometry as a diagnostic tool in mild bleeding disorders: A prospective cohort study

BACKGROUND

Major guidelines emphasise the potential of visco-elastic methods to overcome the limitations of conventional laboratory assays in the peri-operative setting. Their sensitivity regarding mild bleeding disorders (MBDs), the most common bleeding disorders in the general population, is however unknown.

OBJECTIVE

The aim of this study was to investigate the sensitivity of thromboelastometry for diagnosis of MBD.

DESIGN

A single-centre prospective cohort study.

SETTING

Haematology outpatient unit of a tertiary general hospital in Central Switzerland.

PATIENTS

All consecutive patients referred over a 32-month period with a suspected bleeding disorder were included and thromboelastometry was conducted using a ROTEM delta (EXTEM, INTEM and FIBTEM). Diagnostic work-up was performed according to current guidelines including the ISTH bleeding assessment tool (ISTH BAT).

MAIN OUTCOME MEASURES

Distribution of clotting time (CT) and maximum clot firmness (MCF) results in relation to the presence of MBD.

RESULTS

Two hundred and seventeen patients were assessed; the median [IQR] age was 39 years [28 to 57]; 151 patients were women (70%). MBD was diagnosed in 97 patients (45%), no MBD was found in 100 patients (46%) and a systemic disorder recognised in 20 patients (9%). Presence of MBD was not associated with a significant difference in thromboelastometry variables (0.2 s in CT EXTEM, 95% CI -2.3 to 2.7; -0.2 mm in MCF EXTEM, 95% CI -1.8 to 1.5; -0.7 s in CT INTEM, 95% CI -12.6 to 11.2; 0.6 mm in MCF INTEM, 95% CI -1.2 to 1.3; 0.8 mm in MCF FIBTEM, 95% CI -1.6 to 1.4) and most results were within the established reference ranges.

CONCLUSION

Our data did not support the use of thromboelastometry as a diagnostic tool in patients with MBD.

Assessment of agreement and interchangeability between the TEG5000 and TEG6S thromboelastography haemostasis analysers: a prospective validation study

Background

TEG6S® and TEG5000® (Haemonetics Corp, USA) are haemostasis analysers that measure viscoelasticity properties of whole blood. Both use different mechanisms to assess similar components of the coagulation process. The aim of this study was to assess agreement and interchangeability between the TEG6S and TEG5000 analysers.

Methods

3.5 mL whole blood was collected from 25 adult patients in a tertiary intensive care unit (ICU). Analysis was performed using TEG6S and TEG5000 haemostatic platforms. Agreement between platforms was measured using Lin’s concordance coefficient (Lin’s CC), further validated using intraclass correlation coefficients and reduced major axis regression (RMAR).

Results

Sixteen (64%) patients were male; mean (range) age: 59yo (23–86). TEG6S and TEG5000 systems were broadly interchangeable. The majority of TEG variables demonstrated almost perfect or substantial agreement and minimal proportional bias (maximum amplitude demonstrated a fixed bias). LY30%, however, demonstrated poor agreement and a proportional bias. Lin’s CC coefficients (95% CI, RMAR slope, intercept) between TEG6S and TEG5000 variables were: R time: 0.78 (0.64–0.92, 0.76, 0.92); K time: 0.82 (0.69–0.94, 1.30, − 0.93); alpha angle: 0.79 (0.64–0.95, 1.04, − 1.43); maximum amplitude (MA): 0.90 (0.83–0.96, 0.99, − 5.0); LY30%: 0.34 (0.1–0.58, 0.43, 0.04).

Conclusions

Adult patients with critical illness demonstrate almost perfect agreement in the R time and MA, substantial agreement in K time and alpha angle, but poor agreement in LY30%, as measured by the TEG6S and TEG5000 analysers. With the exception of LY30%, the TEG6S and TEG5000 platforms appear interchangeable. This has important implications for use in clinical practice and multi-site research programs.

Trial registration

ANZCRT number: 12617000062325, registered 12/Jan17. Retrospectively registered.

Electronic supplementary material

The online version of this article (10.1186/s12871-019-0717-7) contains supplementary material, which is available to authorized users.

Effects of modification of trauma bleeding management: A before and after study

OBJECTIVE

We hypothesised that the association of tranexamic acid (TXA) administration and thromboelastometry-guided haemostatic therapy (TGHT) with implementation of Damage Control Resuscitation (DCR) reduced blood products (BP) use and massive transfusion (MT).

METHODS

Retrospective comparison of 2 cohorts of trauma patients admitted in a university hospital, before (Period 1) and after implementation of DCR, TXA (first 3-hours) and TGHT (Period 2). Patients were included if they received at least 1 BP (RBC, FFP or platelet) or coagulation factor concentrates (fibrinogen or prothrombin complex) during the first 24-hours following the admission.

RESULTS

380 patients were included. Patients in Period 2 (n = 182) received less frequently a MT (8% vs. 33%, P < 0.01), significantly less BP (RBC: 2 units [1-5] vs. 6 [3-11]; FFP: 0 units [0-2] vs. 4 [2-8]) but more fibrinogen concentrates (3.0 g [1.5-4.5] vs. 0.0 g [0.0-3.0], P < 0.01). Multivariate logistic regression analysis identified Period 1 as being associated with an increased risk of receiving MT (OR: 26.1, 95% CI: 9.7-70.2) and decreased survival at 28 days (OR: 2.0, 95% CI: 1.0-3.9). After propensity matching, the same results were observed but there was no difference for survival and a significant decrease for the cost of BP (2370 ± 2126 vs. 3284 ± 3812 €, P: 0.036).

CONCLUSION

Following the implementation of a bundle of care including DCR, TGHT and administration of TXA, we observed a decrease to the use of blood products, need for MT and an improvement of survival.

Traditional and non-traditional anticoagulation management during extracorporeal membrane oxygenation

Unfractionated heparin (UFH) is the anticoagulant of choice during extracorporeal membrane oxygenation (ECMO) support. Despite its favorable pharmacologic properties, management of heparin anticoagulation during ECMO remains a major challenge. To date, little is known about the optimal monitoring strategy or the heparin dose offering the best safety/efficacy profile. Therefore, it remains unclear if the heparin dose should be adapted to target a specific "clotting time" [e.g., activated clotting time (ACT) or activated partial thromboplastin time (aPTT)] or a heparin concentration, measured by coagulation factor anti-Xa assay. In addition, no study has compared the relevance of modern viscoelastic coagulation tests over the single value of a clotting time or heparin concentration value. Although guidelines for anticoagulation during ECMO support have been published, the absence of evidence limits the quality of the recommendations provided, which explains the major intra- and inter-institutional variability observed. Large prospective multicenter trials are urgently needed to investigate the optimal anticoagulation management strategy during ECMO support.

Review: The Perioperative Use of Thromboelastography for Liver Transplant Patients

Thromboelastography (TEG) is a viscoelastic test that allows rapid evaluation of clot formation and fibrinolysis from a sample of whole blood. TEG is increasingly utilized to guide blood product resuscitation in surgical patients and transfusions for liver transplant patients. Patients with severe liver failure have significant derangement of their clotting function due to impaired production of procoagulant and anticoagulant factors. Traditional coagulation studies are limited by the short time needed for the result and provide little information about the dynamics and strength of clot formation. In addition, traditional coagulation studies do not correlate well with bleeding episodes and may lead to over-transfusion of various blood products. Evidence is less robust regarding the use of TEG for transfusion management decisions in severe liver failure patients awaiting, undergoing, or immediately after liver transplant surgery. However, the available evidence suggests that systematic implementation of TEG rather than traditional coagulation studies results in the administration of fewer blood products without increased mortality or complications. The purpose of this study is to review the literature regarding the use of TEG in liver failure patients prior to liver transplant, intraoperatively, and postoperatively. Additional high-quality randomized controlled studies should be performed to evaluate the use of TEG to guide transfusion decisions, particularly in the postoperative period following liver transplantation.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

The effect of 3 resuscitative fluid therapies on hemostasis as measured by rotational thromboelastometry in dogs

BACKGROUND

Evidence suggests that administration of intravenous fluids impairs hemostasis. Thromboelastometry (TEM) may provide a more sensitive measure of the fluid effects on hemostasis than traditional coagulation tests.

OBJECTIVE

The study aim was to determine if resuscitative fluid therapy affects hemostasis, as measured by TEM.

MATERIALS AND METHODS

Using a randomized crossover design, 6 healthy dogs were administered intravenous colloid, crystalloid, and hypertonic saline at therapeutic doses. Whole blood samples were taken at baseline, 1, 4, and 8 h posttreatment for TEM analysis and measurement of PT, APTT, and fibrinogen. Univariate ANOVA on transformed data evaluated differences between groups and within groups. When significant differences were noted (P = .003), a Tukey test was performed.

RESULTS

A statistically significant interaction between individual dogs and treatment was noted for most TEM variables. There was a significant decrease in clot firmness from baseline in the TEM assessment of the intrinsic pathway. Colloid treatment correlated with significantly higher clot firmness in the TEM extrinsic pathway assessment, which decreased over time, and PT was significantly shorter in colloid-treated dogs. Overall, PT was significantly prolonged at one hour; however, all PT values were within the RI. The fibrinogen concentration was significantly different between all treatments.

CONCLUSIONS

Clinically relevant doses of resuscitative fluids resulted in a decreased clot firmness in the intrinsic pathway, as measured by TEM, which affected hemostatic variables in healthy dogs. There was also a significant individual response to treatment. The changes noted in this study are not expected to result in clinically apparent bleeding.

Thrombodynamics, a new global coagulation test: Measurement of heparin efficiency

The actual coagulation status may be reliably measured using only highly sensitive global functional tests; however, they are not numerous and all of them have disadvantages. Thrombodynamics (TD), a novel global coagulation test, is sensitive to hypo- and hypercoagulable states. The main properties of this test were investigated, and its capabilities for hemostasis analysis were verified through pharmacodynamic monitoring of the most widely used anticoagulants, heparins. The anticoagulant effects in the plasma of donors (n = 20) and patients after hip replacement (n = 20) spiked with unfractionated heparin or enoxaparin were measured in vitro to eliminate the influence of pharmacokinetic factors. Sensitivity for heparins was compared for activated partial thromboplastin time, thrombin generation tests and TD. TD was shown to reliably characterize the pharmacodynamics of any heparin in the entire range of its prophylactic and therapeutic concentrations. Inter-individual variability for the anticoagulant action of heparins was also calculated using the TD data. This variability did not differ between the investigated groups and did not exceed 12% and 20% for the stationary clot growth rate in the presence of unfractionated heparin and enoxaparin, respectively. That finding was in accordance with the values determined earlier using the thrombin generation test. The study results showed that TD has advantages over the other global methods of coagulation analysis. These advantages are good standardization, high reproducibility, independence of the parameter values from patient age and gender, and a narrower parameter distribution in a normal population. These results indicate that TD is a promising universal assessment method that improves the quality of hemostasis analysis because it more reliably detects deviations from the parameters' reference values.

Immunohaemostasis: a new view on haemostasis during sepsis

Host infection by a micro-organism triggers systemic inflammation, innate immunity and complement pathways, but also haemostasis activation. The role of thrombin and fibrin generation in host defence is now recognised, and thrombin has become a partner for survival, while it was seen only as one of the "principal suspects" of multiple organ failure and death during septic shock. This review is first focused on pathophysiology. The role of contact activation system, polyphosphates and neutrophil extracellular traps has emerged, offering new potential therapeutic targets. Interestingly, newly recognised host defence peptides (HDPs), derived from thrombin and other "coagulation" factors, are potent inhibitors of bacterial growth. Inhibition of thrombin generation could promote bacterial growth, while HDPs could become novel therapeutic agents against pathogens when resistance to conventional therapies grows. In a second part, we focused on sepsis-induced coagulopathy diagnostic challenge and stratification from "adaptive" haemostasis to "noxious" disseminated intravascular coagulation (DIC) either thrombotic or haemorrhagic. Besides usual coagulation tests, we discussed cellular haemostasis assessment including neutrophil, platelet and endothelial cell activation. Then, we examined therapeutic opportunities to prevent or to reduce "excess" thrombin generation, while preserving "adaptive" haemostasis. The fail of international randomised trials involving anticoagulants during septic shock may modify the hypothesis considering the end of haemostasis as a target to improve survival. On the one hand, patients at low risk of mortality may not be treated to preserve "immunothrombosis" as a defence when, on the other hand, patients at high risk with patent excess thrombin and fibrin generation could benefit from available (antithrombin, soluble thrombomodulin) or ongoing (FXI and FXII inhibitors) therapies. We propose to better assess coagulation response during infection by an improved knowledge of pathophysiology and systematic testing including determination of DIC scores. This is one of the clues to allocate the right treatment for the right patient at the right moment.

The hypercoagulability paradox of chronic kidney disease: The role of fibrinogen

BACKGROUND

Chronic kidney disease (CKD) patients have increased rates of bleeding as well as thrombosis. Fibrinogen and platelets combine to generate a mature clot, but in CKD platelets are dysfunctional. Therefore, we hypothesize that CKD patients have increased clot strength due to elevated fibrinogen levels.

METHODS

Retrospective review of CKD patients (n = 84) who had rTEG and fibrinogen levels measured. They were compared to healthy controls (n = 134).

RESULTS

CKD patients had statistically significant increases in ACT, angle, MA and decreases in LY30 compared to controls. Fibrinogen levels were increased in CKD patients compared to reference range. Fibrinogen levels had a positive correlation with MA (rho = 0.709, p < 0.0001) in CKD patients.

CONCLUSIONS

Patients with CKD manifest a coagulopathy consisting of delayed clot formation, but increased final clot strength and decreased clot breakdown. Furthermore, the elevated clot strength is mediated by increased fibrinogen levels in CKD patients.

Assessment of Haemostasis in patients undergoing emergent neurosurgery by rotational Elastometry and standard coagulation tests: a prospective observational study

BACKGROUND

Rotational elastometry (ROTEM) has been shown useful to monitor coagulation in trauma patients and in major elective surgery. In this study, we aimed to evaluate the utility of ROTEM to identify hemostatic disturbances and to predict the need for transfusion, compared with standard coagulation tests (SCTs) in patients undergoing emergent neurosurgery.

METHODS

Over a four-year period, adult patients who met criteria for emergent neurosurgery lasting more than 90 min were included in the study. Blood was collected preoperatively and analyzed with SCTs (international normalized ratio [INR], fibrinogen concentration, prothrombin time [PT or Quick], partial thromboplastine time [PTT], fibrinogen concentration and platelet count), and ROTEM assays. Correlations between SCTs and ROTEM parameters as well as receiver operating characteristic curves were performed to detect a coagulopathic pattern based on standard criteria and the need for transfusing at least 3 units of packed red blood cells (PRBCs).

RESULTS

In a cohort of 92 patients, 39 (42%) required ≥3 PRBCs and a coagulopathic pattern was identified in 32 patients based on SCTs and in 19 based on ROTEM. There was a strong correlation between PTT and INTEM coagulation time (R = 0.76) as well as between fibrinogen concentrations and FIBTEM maximal clot firmess (R = 0.70). The need for transfusion (≥ 3 PRBCs) was best predicted by the maximal clot firmess of EXTEM and FIBTEM (AUC of 0.72 and 0.71, respectively) and by fibrinogen concentration (AUC of 0.70).

CONCLUSIONS

In patients undergoing emergent neurosurgery, ROTEM analysis provides valid markers of early coagulopathy and predictors of blood transfusion requirements.

The effect of sepsis and septic shock on the viscoelastic properties of clot quality and mass using rotational thromboelastometry: A prospective observational study

PURPOSE

The study purpose was to define changes in coagulation across the sepsis spectrum using rotational thromboelastometry (ROTEM).

METHODS

Sepsis patients were recruited on admission to the Emergency Department and Intensive Care Units of a large teaching hospital in Wales. ROTEM markers of clot development and fibrinolysis were determined, as well as standard coagulation markers. A healthy control group matched for age and gender was also recruited (n=44).

RESULTS

100 patients were recruited (50 sepsis, 20 severe sepsis and 30 septic shock). Maximum clot firmness was significantly higher in the sepsis (p<0.001) and severe sepsis (p=0.012) groups than the healthy control (71.6±4.5 and 70.4±4.1 vs 64.4 respectively). In septic shock there was prolonged clot development; however, maximum clot firmness remained normal. Fibrinolytic function was significantly impaired in septic shock, which was also significantly associated with 28-day mortality (p<0.001).

CONCLUSIONS

ROTEM indicated significantly enhanced clot structural development in sepsis and severe sepsis, which could be indicative of a hypercoagulable phase. In septic shock, despite there being a prolongation of clotting pathways and impaired fibrinolysis, clot mass was comparably normal, suggestive of the development of a clot with healthy characteristics.