Viscoelastic testing: Critical appraisal of new methodologies and current literature

Comparative assessment of hemostasis in septic patients and healthy controls using standard coagulation tests and whole-blood thromboelastometry

BACKGROUND

Sepsis is associated with dysregulation of procoagulant, anticoagulant, and fibrinolytic pathways.

AIMS

To compare the measurements of coagulation activation, clot formation, stabilization, and lysis between rotational thromboelastometry (ROTEM) and standard coagulation tests (SCTs) on patients with early sepsis (SP) and healthy controls (HC).

METHODS

This observational study included 30 SP and 30 HC. At study inclusion, SCTs and ROTEM analyses were conducted. A modified ROTEM with exogenous tPA was used to investigate fibrinolysis resistance.

RESULTS

SP had longer prothrombin time, higher fibrinogen levels and lower platelet count compared to HC. On ROTEM, clotting initiation was longer in SP than in HC but median clotting time maintained within reference ranges. SP had higher maximum velocity of clot formation, clot firmness, elasticity, and platelet component than HC. Clot lysis indices (CLI) were higher in EXTEM and APTEM (without and with added tPA) in SP compared to HC. The difference in CLI between APTEM and EXTEM was lower for both native and tPA-spiked samples in SP compared with HC.

CONCLUSIONS

While SCTs suggest SP are hypocoagulable, VET revealed normal coagulation initiation in more than 80 % of SP. Compared to HC, SP had increased clot propagation, firmness and elasticity, and decreased platelet-mediated clot retraction and lysis. In sepsis, VET provide more comprehensive information about hemostatic changes than SCTs.

What, When, and Why: Viscoelastic Hemostatic Assays and Their Uses in Trauma Resuscitation

Viscoelastic hemostatic assays (VHAs) have become a valuable tool in guiding transfusion therapy, particularly in trauma care. While various forms of VHA exist, all provide a quantitative assessment of clot kinetics, strength, and dissolution. Studies have demonstrated that VHA can reduce both mortality and utilization of blood products in the general population. Interpreting VHA results requires consideration of specific patient factors, such as age and altered physiological properties as in pregnancy and the process of aging. Further research is needed to establish accurate reference ranges for these specific populations. This review article provides a comprehensive overview of the technical aspects of VHA as well as their clinical uses in trauma resuscitation.

A Modified Viscoelastic Point-of-Care Method for Rapid Quantitative Detection of Enoxaparin: A Single-Centre Observational Study

Background: Laboratory monitoring of the effect of low-molecular-weight heparins (LMWHs) is generally not necessary. However, prompt evaluation of heparin inhibitory effects (i.e., anti-Xa activity) is important in cases of life-threatening bleeding, need for urgent surgery or acute thromboembolism under LMWH treatment. We aimed to establish a simple and reliable point-of-care method for the detection of enoxaparin. Methods: Eighty patients under enoxaparin therapy and ten healthy volunteers without any anticoagulant treatment were enrolled. Simultaneous measurements of anti-Xa activity using the chromogenic method and clotting times in the absence and presence of polybrene using viscoelastometric assays containing Russell's viper venom (RVV-test) were performed on the ClotPro device. Results: Among the measured and derived RVV-test parameters, the ratio of the RVV clotting times (RVV CT) detected in the absence and presence of polybrene showed the best statistically significant correlation with anti-Xa activity (r = 0.774, p < 0.001). Based on ROC analysis, we designated RVV CT ratios of 1.02, 1.23 and 1.6 as the best cut-off values for separating anti-Xa ranges below and above 0.3 and 0.6 IU/mL, respectively. If the RVV CT ratio is below or above 1.23, the anti-Xa activity is suggested to be below 0.6 IU/mL or above 0.3 IU/mL with high certainty, respectively. Further differentiation is possible if the RVV CT ratio is measured below 1.02 or above 1.6. In these cases, the measured anti-Xa values are below 0.3 IU/mL or above 0.6 IU/mL, respectively, with high probability and good predictive values. Conclusions: Our method can provide semiquantitative information on the effect of enoxaparin and the expected anti-Xa activity within 10 min in real clinical situations.

New device, old algorithm? Bridging generations in perioperative coagulation management

Viscoelastic testing permits targeted correction of coagulopathy in bleeding patients. As new generations of viscoelastic testing platforms become available, research exploring similarities and differences with older devices can provide insight for institutions seeking to use the newer technologies. Care must be taken to ensure such studies are designed to produce clinically meaningful guidance for adapting existing treatment algorithms to accommodate the latest viscoelastic testing technology.

Major Bleeding in the Emergency Department: A Practical Guide for Optimal Management

Major bleeding is a life-threatening condition with high morbidity and mortality. Trauma, gastrointestinal bleeding, haemoptysis, intracranial haemorrhage or other causes of bleeding represent major concerns in the Emergency Department (ED), especially when complicated by haemodynamic instability. Severity and source of bleeding, comorbidities, and prior use of anticoagulants are pivotal factors affecting both the clinical status and the patients' differential response to haemorrhage. Thus, risk stratification is fundamental in the initial assessment of patients with bleeding. Aggressive resuscitation is the principal step for achieving haemodynamic stabilization of the patient, which will further allow appropriate interventions to be made for the definite control of bleeding. Overall management of major bleeding in the ED should follow a holistic individualized approach which includes haemodynamic stabilization, repletion of volume and blood loss, and reversal of coagulopathy and identification of the source of bleeding. The aim of the present practical guide is to provide an update on recent epidemiological data about the most common etiologies of bleeding and summarize the latest evidence regarding the bundles of care for the management of patients with major bleeding of traumatic or non-traumatic etiology in the ED.

Complex Pattern of Platelet Activation/Reactivity After SARS-CoV-2 Infection

COVID-19 and post-COVID (long COVID) are associated with thromboembolic complications; however, it is still not clear whether platelets play a leading role in this phenomenon. The platelet hyperreactivity could result from the direct interaction between platelets and viral elements or the response to inflammatory and prothrombotic factors released from blood and vessel cells following infection. The existing literature does not provide clear-cut answers, as the results determining platelet status vary according to methodology. Elevated levels of soluble markers of platelet activation (P selectin, PF4), increased platelet aggregates, and platelet-derived microparticles suggest the activation of platelets circulating in the bloodstream of COVID-19 patients. Similarly, platelets isolated from COVID-19 patients demonstrate increased reactivity in response to collagen, thrombin, and ADP. By contrast, an analysis of whole blood from COVID-19 patients indicates the reduced activation of the fibrinogen receptor. Similarly, some in vitro studies report potential targets for SARS-CoV-2 in platelets, whereas others do not indicate any direct effect of the virus on platelets. The aim of this work is to review and evaluate the reliability of the methodology for testing platelet function after contact with SARS-CoV-2. Despite the diversity of methods yielding varying results and the influence of plasma components or blood cells, it can be concluded that platelets play an important role in the development of thrombotic complications after exposure to SARS-CoV-2.

The thromboelastogram is confounded by hematocrit in clinical samples tested on both mechanical and acoustic platforms

Red blood cells are critical participants in normal hemostasis, but in vitro experiments have shown that the thromboelastogram (TEG) maximum amplitude has a paradoxical inverse relationship with hematocrit. This study reviewed all samples at a single academic institution where any mechanical (TEG 5000) or acoustic (TEG 6s) TEG was drawn within 5 min of hematocrit measurement. A total of 7,176 samples were identified using complete TEG and conventional coagulation test data (6,384 mechanical, 744 acoustic, and 48 both). In the primary analysis, hematocrit was negatively associated with the maximum amplitude on both mechanical and acoustic platforms after adjusting for relevant confounders. This suggests that the thromboelastogram may misrepresent the contribution of red blood cells in normal hemostasis.

Anesthetic Implications of Factor XI Deficiency: A Clinical Case Study and Review of Literature

Factor XI deficiency, a rare but significant coagulopathy, poses unique challenges in perioperative management, particularly in obstetric settings. This review provides an in-depth exploration of the pathophysiology, diagnosis, and anesthetic implications of factor XI deficiency, thereby emphasizing the useful role of anesthesiologists. The variable bleeding phenotype of the disorder necessitates a nuanced understanding and tailored management strategies to mitigate severe perioperative bleeding risks. Conventional coagulation tests, while useful, often fall short in predicting bleeding risks, underscoring the importance of advanced diagnostic tools, such as viscoelastic testing. Viscoelastic testing provides real-time data on clot stability, which allows for immediate intervention and more targeted therapeutic strategies compared to standard coagulation tests. A clinical case of a 25-year-old patient with factor XI deficiency undergoing emergency surgery for an ectopic pregnancy illustrates the application of viscoelastic testing in managing acute bleeding and optimizing patient outcomes and advocates for the development of standardized protocols, continuous monitoring techniques, and enhanced training programs to improve the perioperative care of patients with factor XI deficiency, providing anesthesiologists with the tools necessary to navigate the complexities of factor XI deficiency in the perioperative environment. Integrating these advanced diagnostic and therapeutic approaches could significantly improve patient safety and surgical outcomes in patients with complex coagulopathy.

Hemostasis in Pre-Eclamptic Women and Their Offspring: Current Knowledge and Hemostasis Assessment with Viscoelastic Tests

Pre-eclampsia (PE) is a placenta-mediated disease and remains a major cause of maternal and neonatal mortality and morbidity. As PE develops, normal pregnancy's hypercoagulable balance is disrupted, leading to platelet hyperactivation, excessive pathological hypercoagulability, and perturbed fibrinolysis. This narrative review aims to summarize the current knowledge regarding hemostasis in PE compared with healthy gestation and the potential effects of maternal PE on neonatal hemostasis. Finally, it aims to discuss hemostasis assessments for normal pregnancies and PE, emphasizing the role of viscoelastic tests, namely, thromboelastography (TEG) and thromboelastometry (ROTEM), for monitoring PE-associated hemostatic alterations. The use of TEG/ROTEM for assessing the hemostatic profile of PE women has been little considered, even though conventional coagulation tests (CCTs) have not helped to monitor hemostasis in this population. Compared with normal pregnancy, TEG/ROTEM in PE reveals an excessive hypercoagulability analogous with the severity of the disease, characterized by higher-stability fibrin clots. The TEG/ROTEM parameters can reflect PE severity and may be used for monitoring and as predictive markers for the disease.