Hyperfibrinolysis drives mechanical instabilities in a simulated model of trauma induced coagulopathy

A surface-functionalized whole blood-based dielectric microsensor for assessment of clot firmness in a fibrinolytic environment

Accurate assessment of fibrin clot stability can predict bleeding risk in coagulopathic conditions such as thrombocytopenia and hypofibrinogenemia. Hyperfibrinolysis - a clinical phenotype characterized by an accelerated breakdown of the fibrin clot - makes such assessments challenging by obfuscating the effect of hemostatic components including platelets or fibrinogen on clot stability. In this work, we present a biofunctionalized, microfluidic, label-free, electronic biosensor to elicit unique, specific, and differential responses from the multifactorial processes of blood coagulation and fibrinolysis ex vivo. The microsensor tracks the temporal variation in the normalized real part of the dielectric permittivity of whole blood (<10 μL) at 1 MHz as the sample coagulates within a three-dimensional, parallel-plate, capacitive sensing area. Surface biofunctionalization of the microsensor's electrodes with physisorption of tissue factor (TF) and aprotinin permits real-time assessment of the coagulation and fibrinolytic outcomes. We show that surface coating with TF and manual addition of TF result in a similar degree of acceleration of coagulation kinetics in human whole blood samples. We also show that surface coating with aprotinin and manual addition of aprotinin yield similar results in inhibiting tissue plasminogen activator (tPA)-induced upregulated fibrinolysis in human whole blood samples. Validated through a clinically relevant, complementary assay - rotational thromboelastometry for clot viscoelasticity - we finally establish that a microsensor dual-coated with both TF and aprotinin detects the hemostatic rescue in the tPA-induced hyperfibrinolytic profile of whole blood and the hemostatic dysfunction due to concurrent platelet depletion in the blood sample, thus featuring enhanced ability in evaluating complex, combinatorial coagulopathies.

Variability of fibrinolytic activity in pregnant patients exposed to tissue plasminogen activator: an in vitro study utilizing rotational thromboelastometry

BACKGROUND

The investigation into the variability of fibrinolysis in obstetric patients is notably limited despite its relevance to postpartum hemorrhage. We investigate an in vitro model of fibrinolysis measured by rotational thromboelastrometry (ROTEM) in maternal blood samples with lysis stimulated by tissue plasminogen activator (tPA).

METHODS

Written informed consent was obtained from 19 patients at term pregnancy during admission to the labor and delivery unit. Patients who were taking medication affecting coagulation were excluded. Tissue plasminogen activator was added to whole blood samples to a final concentration of 100 or 220 ng/mL prior to ROTEM testing.

RESULTS

The addition of tPA produced high intra-individual fibrinolytic variability for clot firmness and lysis parameters. Patients responded differently to each tPA dose ranging from clot lysis within the range of 0 ng/mL tPA group to complete clot lysis. The coefficient of variation (CV) values for the 220 ng/mL tPA group were: EXTEM MCF 0.510, EXTEM LI30 1.601, FIBTEM MCF 0.349, FIBTEM LI30 2.097. CV values for the 100 ng/mL tPA group were: EXTEM MCF 0.144, EXTEM LI30 1.038, FIBTEM MCF 0.096, FIBTEM LI30 1.238.

CONCLUSION

We demonstrate a wide range of fibrinolytic response in the obstetric population to exogeneous tPA. We found subgroups of patients that were very responsive to tPA and insensitive to tPA. This study represents a preliminary exploration into classifying the obstetric fibrinolytic phenotypes. Further research will integrate relevant coagulation factors to establish a predictive model for testing susceptibility to lysis that can be applied at the point of care.

Comprehensive Analysis of the Role of Fibrinogen and Thrombin in Clot Formation and Structure for Plasma and Purified Fibrinogen

Altered properties of fibrin clots have been associated with bleeding and thrombotic disorders, including hemophilia or trauma and heart attack or stroke. Clotting factors, such as thrombin and tissue factor, or blood plasma proteins, such as fibrinogen, play critical roles in fibrin network polymerization. The concentrations and combinations of these proteins affect the structure and stability of clots, which can lead to downstream complications. The present work includes clots made from plasma and purified fibrinogen and shows how varying fibrinogen and activation factor concentrations affect the fibrin properties under both conditions. We used a combination of scanning electron microscopy, confocal microscopy, and turbidimetry to analyze clot/fiber structure and polymerization. We quantified the structural and polymerization features and found similar trends with increasing/decreasing fibrinogen and thrombin concentrations for both purified fibrinogen and plasma clots. Using our compiled results, we were able to generate multiple linear regressions that predict structural and polymerization features using various fibrinogen and clotting agent concentrations. This study provides an analysis of structural and polymerization features of clots made with purified fibrinogen or plasma at various fibrinogen and clotting agent concentrations. Our results could be utilized to aid in interpreting results, designing future experiments, or developing relevant mathematical models.

Injury Severity is a Key Contributor to Coagulation Dysregulation and Fibrinogen Consumption

Background

Traumatic injury is a leading cause of death for those under the age of 45, with 40% occurring due to hemorrhage. Severe tissue injury and hypoperfusion lead to marked changes in coagulation, thereby preventing formation of a stable blood clot and increasing hemorrhage associated mortality.

Objectives

We aimed to quantify changes in clot formation and mechanics occurring after traumatic injury and the relationship to coagulation kinetics, and fibrinolysis.

Methods

Plasma was isolated from injured patients upon arrival to the emergency department. Coagulation kinetics and mechanics of healthy donors and patient plasma were compared with rheological, turbidimetric and thrombin generation assays. ELISA's were performed to determine tissue plasminogen activator (tPA) and D-dimer concentration, as fibrinolytic markers.

Results

Sixty-three patients were included in the study. The median injury severity score (ISS) was 17, median age was 37.5 years old, and mortality rate was 30%. Rheological, turbidimetric and thrombin generation assays indicated that trauma patients on average, and especially deceased patients, exhibited reduced clot stiffness, increased fibrinolysis and reduced thrombin generation compared to healthy donors. Fibrinogen concentration, clot stiffness, D-dimer and tPA all demonstrated significant direct correlation to increasing ISS. Machine learning algorithms identified and highlighted the importance of clinical factors on determining patient outcomes.

Conclusions

Viscoelastic and biochemical assays indicate significant contributors and predictors of mortality for improved patient treatment and therapeutic target detection.

ESSENTIALS

Traumatic injury may lead to alterations in a patient's ability to form stable blood clotsA study was performed to assess how trauma severity affects coagulation kineticsKey alterations were observed in trauma patients, who exhibit weaker and slower forming clotsPaired with machine learning methods, the results indicate key aspects contributing to mortality.