Computational model of tranexamic acid on urokinase mediated fibrinolysis

Understanding the coagulation process is critical to developing treatments for trauma and coagulopathies. Clinical studies on tranexamic acid (TXA) have resulted in mixed reports on its efficacy in improving outcomes in trauma patients. The largest study, CRASH-2, reported that TXA improved outcomes in patients who received treatment prior to 3 hours after the injury, but worsened outcomes in patients who received treatment after 3 hours. No consensus has been reached about the mechanism behind the duality of these results. In this paper we use a computational model for coagulation and fibrinolysis to propose that deficiencies or depletions of key anti-fibrinolytic proteins, specifically antiplasmin, a1-antitrypsin and a2-macroglobulin, can lead to worsened outcomes through urokinase-mediated hyperfibrinolysis.

Cost-effectiveness evaluation of the PROPPR trial transfusion protocols

BACKGROUND

There have been no prior investigations of the cost effectiveness of transfusion strategies for trauma resuscitation. The Pragmatic, Randomized, Optimal Platelet and Plasma Ratios (PROPPR) study was a Phase III multisite, randomized trial in 680 subjects comparing the efficacy of 1:1:1 transfusion ratios of plasma and platelets to red blood cells with the 1:1:2 ratio. We hypothesized that 1:1:1 transfusion results in an acceptable incremental cost-effectiveness ratio, when estimated using patients' age-specific life expectancy and cost of care during the 30-day PROPPR trial period.

STUDY DESIGN AND METHODS

International Classification of Diseases, Ninth Revision codes were prospectively collected, and subjects were matched 1:2 to subjects in the Healthcare Utilization Program State Inpatient Data to estimate cost weights. We used a decision tree analysis, combined with standard costs and estimated years of expected survival to determine the cost effectiveness of the two treatments.

RESULTS

The 1:1:1 group had higher overall costs for the blood products but were more likely to achieve hemostasis and decreased hemorrhagic death by 24 hours (p = 0.006). For every 100 patients treated in the 1:1:1 group, eight more achieved hemostasis than in the 1:1:2 group. At 30 days, the total hospital cost per 100 patients was $5.6 million in the 1:1:1 group compared with $5.0 million in the 1:1:2 group. For each 100 patients, the 1:1:1 group had 218.5 more years of life expectancy. This was at a cost of $2994 per year gained.

CONCLUSION

The 1:1:1 transfusion ratio in severely injured hemorrhaging trauma patients is a very cost-effective strategy for increasing hemostasis and decreasing trauma deaths.

Heterogeneity of Integrin αIIbβ3 Function in Pediatric Immune Thrombocytopenia Revealed by Continuous Flow Cytometry Analysis

Immune thrombocytopenia (ITP) is an autoimmune condition primarily induced by the loss of immune tolerance to the platelet glycoproteins. Here we develop a novel flow cytometry approach to analyze integrin α_IIbβ₃ functioning in ITP in comparison with Glanzmann thrombasthenia (GT) (negative control) and healthy pediatric donors (positive control). Continuous flow cytometry of Fura-Red-loaded platelets from whole hirudinated blood was used for the characterization of platelet responses to conventional activators. Calcium levels and fibrinogen binding were normalized to ionomycin-induced responses. Ex vivo thrombus formation on collagen was observed in parallel-plate flow chambers. Platelets from all ITP patients had significantly higher cytosolic calcium concentration in the quiescent state compared to healthy donors (15 ± 5 nM vs. 8 ± 5 nM), but calcium increases in response to all activators were normal. Clustering analysis revealed two subpopulations of ITP patients: the subgroup with high fibrinogen binding (HFB), and the subgroup with low fibrinogen binding (LFB) (8% ± 5% for LFB vs. 16% ± 3% for healthy donors in response to ADP). GT platelets had calcium mobilization (81 ± 23 nM), fibrinogen binding (5.1% ± 0.3%) and thrombus growth comparable to the LFB subgroup. Computational modeling suggested phospholipase C-dependent platelet pre-activation for the HFB subgroup and lower levels of functional integrin molecules for the LFB group.

Direct oral anticoagulant plus antiplatelet therapy: prescribing practices and bleeding outcomes

Concurrent antiplatelet therapy (APT) is common during warfarin therapy but is less well-documented during direct oral anticoagulant (DOAC) therapy. Combined anticoagulant and APT use has been associated with increased bleeding risk without providing additional protection against thrombosis. This study aimed to describe single-center prescribing rates of DOAC + APT as well as compare bleeding rates between DOAC monotherapy and DOAC + APT cohorts. Patients receiving DOAC therapy were evaluated for APT use at the time of hospital discharge. Patients were categorized into DOAC monotherapy and DOAC + APT cohorts. Primary outcomes included DOAC + APT prescribing rate as well as rates of major bleeding and clinically relevant non-major bleeding (CRNMB) within six months after hospital discharge. Secondary outcomes included rates of thromboembolism and all-cause mortality. Of 407 patients receiving DOAC therapy, 78 (19.2%) also received APT at hospital discharge. Common indications for APT included secondary cardiovascular event prevention (57.7%) and primary cardiovascular event prevention (29.5%). The indication for APT could not be determined in 12.8% of patients. The major bleeding rate was 1.3% for DOAC + APT and 1.2% for DOAC monotherapy (p = 0.95). The CRNMB rate was 10.2% for DOAC + APT and 6.4% for DOAC monotherapy (p = 0.23). Thromboembolism and mortality were infrequent in both cohorts. DOAC + APT was documented in approximately 1 of 5 patients. Adding APT to DOAC therapy did not significantly increase the major bleeding or CRNMB rates compared to DOAC monotherapy but the sample size limits drawing conclusions about the safety of these regimens. Targeting primary prevention or unclear indications for APT could be a focus of future interventions.

Serum insulin levels are associated with vulnerable plaque components in the carotid artery: the Rotterdam Study

BACKGROUND

To investigate the association between fasting serum insulin and glucose levels with atherosclerotic plaque composition in the carotid artery. Impaired insulin and glucose levels are implicated in the etiology of cardiovascular disease; however, their influence on the formation and composition of atherosclerotic plaque remains unclear.

METHODS

In 1740 participants (mean age 72.9 years, 46% women, 14.4% diabetes mellitus) from the population-based Rotterdam Study, we performed carotid MRI to evaluate the presence of calcification, lipid core, and intraplaque hemorrhage in carotid atherosclerosis. All participants also underwent blood sampling to obtain information on serum insulin and glucose levels. Using logistic regression models, we assessed the association of serum insulin and glucose levels (per s.d. and in tertiles) with the different plaque components, while adjusting for sex, age, intima-media thickness, and cardiovascular risk factors.

RESULTS

Serum insulin levels were associated with the presence of intraplaque hemorrhage (adjusted odds ratio (OR): 1.42 (95% CI: 1.12-1.7)) We found no association with the presence of calcification or lipid core. Sensitivity analyses restricted to individuals without diabetes mellitus yielded similar results. No associations were found between serum glucose levels and any of the plaque components.

CONCLUSIONS

Serum insulin levels are associated with the presence of vulnerable components of carotid plaque, specifically with intraplaque hemorrhage. These findings suggest a complex role for serum insulin in the pathophysiology of carotid atherosclerosis and in plaque vulnerability.

The Monocyte-to-Lymphocyte Ratio at Hospital Admission Is a Novel Predictor for Acute Traumatic Intraparenchymal Hemorrhage Expansion after Cerebral Contusion

PURPOSE

To explore the potential of monocyte-to-lymphocyte ratio (MLR) at hospital admission for predicting acute traumatic intraparenchymal hematoma (tICH) expansion in patients with cerebral contusion. Patients and Methods. This multicenter, observational study included patients with available at-hospital admission (baseline) and follow-up computed tomography for volumetric analysis (retrospective development cohort: 1146 patients; prospective validation cohort: 207 patients). Semiautomated software assessed tICH expansion (defined as ≥33% or 5 mL absolute growth). MLR was acquired from routine blood tests upon admission. We constructed two predictive models: basic combined model of clinical and imaging variables and MLR combined model of both MLR and other variables in the basic model. Receiver operating characteristic (ROC) analysis and decision curve analysis (DCA) were used to estimate the performance of MLR for predicting acute tICH expansion.

RESULTS

MLR was significantly larger in patients with acute tICH expansion compared to those without acute tICH expansion (mean [SD], 1.08 [1.05] vs. 0.59 [0.37], P < 0.001). A nonlinear positive relationship between MLR and the incidence of acute tICH expansion was observed. Multivariate logistic regression indicated MLR as an independent risk factor for acute tICH expansion (odds ratio (OR), 5.88; 95% confidence interval (CI), 4.02-8.61). The power of the multivariate model for predicting acute tICH expansion was substantially improved with the inclusion of MLR (AUC 0.86 vs. AUC 0.74, P < 0.001), as was also observed in an external validation cohort (AUC 0.83 vs. AUC 0.71, P < 0.001). The net benefit of MLR model was higher between threshold probabilities of 20-100% in DCA. For clinical application, a nomogram derived from the multivariate model with MLR was introduced. In addition, MLR was positively associated with 6-month unfavorable outcome.

CONCLUSION

MLR is a novel predictor for traumatic parenchymatous hematoma expansion. A nomogram derived from the MLR model may provide an easy-to-use tool for predicting acute tICH expansion and promoting the individualized treatment of patients with hemorrhagic cerebral contusion. MLR is associated with long-term outcome after cerebral contusion.

Varying effects of tyrosine kinase inhibitors on platelet function-A need for individualized CML treatment to minimize the risk for hemostatic and thrombotic complications?

Since their introduction, tyrosine kinase inhibitors (TKIs, eg, imatinib, nilotinib, dasatinib, bosutinib, ponatinib) have revolutionized the treatment of chronic myeloid leukemia (CML). However, long-term treatment with TKIs is associated with serious adverse events including both bleeding and thromboembolism. Experimental studies have shown that TKIs can cause platelet dysfunction. Herein, we present the first side-by-side investigation comparing the effects of currently used TKIs on platelet function and thrombin generation when used in clinically relevant concentrations. A flow cytometry multiparameter protocol was used to study a range of significant platelet activation events (fibrinogen receptor activation, alpha granule, and lysosomal exocytosis, procoagulant membrane exposure, and mitochondrial permeability changes). In addition, thrombin generation was measured in the presence of TKIs to assess the effects on global hemostasis. Results show that dasatinib generally inhibited platelet function, while bosutinib, nilotinib, and ponatinib showed less consistent effects. In addition to these general trends for each TKI, we observed a large degree of interindividual variability in the effects of the different TKIs. Interindividual variation was also observed when blood from CML patients was studied ex vivo with whole blood platelet aggregometry, free oscillation rheometry (FOR), and flow cytometry. Based on the donor responses in the side-by-side TKI study, a TKI sensitivity map was developed. We propose that such a sensitivity map could potentially become a valuable tool to help in decision-making regarding the choice of suitable TKIs for a CML patient with a history of bleeding or atherothrombotic disease.

Coagulant Effects and Mechanism of Schefflera heptaphylla (L.) Frodin

Schefflera heptaphylla (L.) Frodin, are commonly used in anti-inflammatory, analgesic, traumatic bleeding and hemostasisas. In this paper, the coagulation effect of the ethanol extract (Set), ethyl acetate phase (Sea) and n-butanol phase (Sbu) was evaluated by prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT) and fibrinogen content (FIB) assays in vitro. Then, Three main lupanine triterpenes (compounds A-C) were isolated and identified from Sea and Sbu by a bioassay-guided method and their structure were identified as 3α-Hydroxy-lup-20(29)-ene-23, 28-dioic acid, betulinic acid 3-O-sulfate and 3α-Hydroxy-lup-20(29)-ene-23, 28-dioic acid 28-O-(α-l-rhamnopyranosyl(1→4)-O-β-d-glucopyranosyl(1→6))-β-d-glucopyranoside) by spectroscopic data analysis. Among of them, compound B was confirmed to have significant coagulant effect in vitro. Furthermore, the pro-coagulation mechanism of S. heptaphylla extracts and compound B were investigated by measuring whole blood viscosity (WBV), plasma viscosity (PV), erythrocyte sedimentetion rate (ESR), pack cell volume (PCV), APTT, PT, TT, and FIB in vivo. Meanwhile, the levels of thromboxane B2 (TXB2), 6-keto prostaglandin F1α (6-keto-PGF1α), endothelial nitric oxide synthase (eNOS) and (endothelin-1) ET-1 were detected. The bleeding time (BT) was tested by tail bleeding method, which proved the traumatic bleeding and hemostasis activities of S. heptaphylla. The pharmacology experiments showed that the Set, Sea, Sbu and compound B has significant pro-coagulation effect. In addition, compound B might be the main constituent of pro-coagulation in S. heptaphylla These results could support the fact that S. heptaphylla could be used traditionally to cure traumatic bleeding, and the pro-coagulation effects were associated with the regulation of vascular endothelium active substance and hemorheology parameters.

New advances in the diagnosis of von Willebrand disease

von Willebrand disease (VWD) is the most common autosomal inherited bleeding disorder, with an estimated prevalence of 1 in 1000 individuals. VWD is classified into quantitative and qualitative forms. Diagnosis of VWD is complex and requires (1) a personal history of bleeding symptoms, (2) family history of bleeding or VWD, and (3) confirmatory laboratory testing. There are certain bleeding assessment tools to objectively measure bleeding symptoms in patients that have been shown to correlate with the diagnosis as well as the severity of VWD. Laboratory diagnosis requires at least initially a measurement of von Willebrand factor (VWF) antigen levels, VWF platelet binding activity (VWF:RCo, VWF:GPIbM, and VWF:GPIbR), and factor VIII (FVIII) activity. Additional testing to confirm the specific subtype may include VWF collagen binding activity, low-dose ristocetin VWF-platelet binding, FVIII-VWF binding, VWF multimer analysis, and VWF propeptide antigen. Recent advances have been made regarding some of these assays. Molecular testing in VWD is not found to be useful in "low VWF" or most type 1 VWD cases but may be informative in patients with severe type 1 VWD, type 1C VWD, type 2 VWD, or type 3 VWD for accurate diagnosis, genetic counseling, and appropriate treatment. The diagnostic algorithm for VWD is complex, but advances continue to be made in improving VWF functional assays and diagnostic pathways.

Tranexamic Acid for Acute Hemorrhage: A Narrative Review of Landmark Studies and a Critical Reappraisal of Its Use Over the Last Decade

The publication of the Clinical Randomization of an Antifibrinolytic in Significant Hemorrhage-2 (CRASH-2) study and its intense dissemination prompted a renaissance for the use of the antifibrinolytic agent tranexamic acid (TXA) in acute trauma hemorrhage. Subsequent studies led to its widespread use as a therapeutic as well as prophylactic agent across different clinical scenarios involving bleeding, such as trauma, postpartum, and orthopedic surgery. However, results from the existing studies are confounded by methodological and statistical ambiguities and are open to varied interpretations. Substantial knowledge gaps remain on dosing, pharmacokinetics, mechanism of action, and clinical applications for TXA. The risk for potential thromboembolic complications with the use of TXA must be balanced against its clinical benefits. The present article aims to provide a critical reappraisal of TXA use over the last decade and a "thought exercise" in the potential downsides of TXA. A more selective and individualized use of TXA, guided by extended and functional coagulation assays, is advocated in the context of the evolving concept of precision medicine.

Factor VIII replacement is still the standard of care in haemophilia A

Prophylactic factor VIII (FVIII) has dramatically improved haemophilia A treatment, preventing joint bleeding and halting the deterioration of joint status. FVIII products with an extended plasma half-life further improve patients' quality of life and increase therapeutic adherence. New licensed classes of non-replacement products include prophylactic emicizumab, which is administered subcutaneously up to every 4 weeks. However, this drug is not suitable for acute bleeding episodes or management of major surgery, and long-term data on the impact of emicizumab on joint health, FVIII inhibitor development and thrombotic risk are awaited. Prophylaxis with FVIII replacement remains the standard of care in haemophilia A, with the aim of achieving a level of haemostasis control that allows patients to meet their lifestyle goals.

D-dimer levels enhance the discriminatory capacity of bleeding risk scores for predicting in-hospital bleeding events in acute pulmonary embolism

INTRODUCTION

Bleeding is a major complication of anticoagulation in acute pulmonary embolism (APE) while estimating individual bleeding risk remains challenging. Elevated D-dimer levels (DD) have been shown to predict bleeding events.

OBJECTIVES

(1) direct comparison of the capacity of bleeding risk prediction scores (VTE-BLEED, RIETE, HAS-BLED, HEMORR₂HAGES) to prognosticate in-hospital bleeding events in the acute phase of APE in a real-life population of APE patients;(2) augmentation of the discriminative capacity of fore mentioned scores with DD.

MATERIALS

Post-hoc analysis of a prospective observational study. DD levels were measured using the VIDAS D-dimer Exclusion test. Receiver operating characteristic curves, areas under the curve (AUC) for bleeding prediction were calculated for scores and DD. Bleeding scores+DD were compared using an established index quantifying the reclassification of patients (net reclassification index, NRI).

RESULTS

310 APE patients were included. 35(11.3%) bleeding events occurred (hematomas, GI, urinary tract, retroperitoneal, uterine, CNS, respiratory tract): 17 major (MB) and 18 clinically-relevant non-major bleedings (CRNMB), none were fatal. All scores had satisfactory AUCs (0.754-0.767), except HAS-BLED (AUC = 0.512; 0.455-0.569). DD were higher in patients with bleeding events (29,911 ng/ml vs. 4805 ng/ml, p = .031), AUC 0.621(0.520-0.721), p = .02. DD = 5750 ng/ml was characterized by OR = 2.3(95%CI 1.05-5.0) for all bleeding events. Adding DD improved the discriminatory capacity of tested scores in the non-high risk of bleeding category, NRI 0.07-03.

CONCLUSIONS

Of the tested scores RIETE, HEMORR₂HAGES, VTE-BLEED performed best at identifying APE patients at risk of in-hospital bleeding complications. DD levels may predict in-hospital bleeding events and may improve identifying patients classified as non-high risk who experience bleeding complications.

The risk of major bleeding in patients with suspected heparin-induced thrombocytopenia

BACKGROUND

The presence of a hypercoagulable disorder such as heparin-induced thrombocytopenia (HIT) may protect against anticoagulant-associated bleeding.

OBJECTIVES

To determine the incidence of major bleeding in patients with suspected HIT.

METHODS

We performed a retrospective analysis of 310 patients suspected of having HIT from the Hospital of the University of Pennsylvania and an affiliated community hospital. We compared the cumulative incidence of major bleeding following suspicion for HIT by ultimate HIT status (HIT+ or HIT-) and exposure to an alternative anticoagulant (Tx+ or Tx-). Secondary outcomes included the incidence of new/progressive thrombosis and 30-day mortality.

RESULTS

The incidence of major bleeding was high in the HIT+Tx+, HIT- Tx+, and HIT-Tx- groups (35.7%, 44.0%, and 37.3%, respectively). The time to first major bleeding event did not differ between groups (P = .24). Factors associated with increased risk of major bleeding included intensive care unit admission (HR 2.24, 95% CI 1.44-3.47), platelet count < 25 × 109 /L (HR 2.13, 1.10-4.12), and renal dysfunction (HR 1.56, 1.06-2.27); 35.7% of HIT+Tx+, 13.8% HIT-Tx+, and 9.3% of HIT-Tx- patients experienced new or progressive thrombosis. Mortality was similar among the three groups (26.2% HIT+Tx+, 34.5% HIT-Tx+, and 26.7% of HIT-Tx- [P = .34]).

CONCLUSIONS

Among patients with suspected HIT, major bleeding was common regardless of HIT status. Contrary to our hypothesis, HIT+ patients were not protected from major bleeding. A better understanding of bleeding risk is needed to inform management decisions in patients with suspected HIT.

Effect of tranexamic acid administration on acute traumatic coagulopathy in rats with polytrauma and hemorrhage

Trauma and hemorrhagic shock can lead to acute traumatic coagulopathy (ATC) that is not fully reversed by prehospital resuscitation as simulated with a limited volume of fresh whole blood (FWB) in a rat model. Tranexamic Acid (TXA) is used as an anti-fibrinolytic agent to reduce surgical bleeding if administered prior to or during surgery, and to improve survival in trauma if given early after trauma. It is not clear from the existing clinical literature whether TXA has the same mechanism of action in both settings. This study sought to explore the molecular mechanisms of TXA activity in trauma and determine whether administration of TXA as a supplement to FWB resuscitation could attenuate the established ATC in a rat model simulating prehospital resuscitation of polytrauma and hemorrhagic shock. In a parallel in-vitro study, the effects on clotting assays of adding plasmin at varying doses along with either simultaneous addition of TXA or pre-incubation with TXA were measured, and the results suggested that maximum anti-fibrinolytic effect of TXA on plasmin-induced fibrinolysis required pre-incubation of TXA and plasmin prior to clot initiation. In the rat model, ATC was induced by polytrauma followed by 40% hemorrhage. One hour after trauma, the rats were resuscitated with FWB collected from donor rats. Vehicle or TXA (10mg/kg) was given as bolus either before trauma (TXA-BT), or 45min after trauma prior to resuscitation (TXA-AT). The TXA-BT group was included to contrast the coagulation effects of TXA when used as it is in elective surgery vs. what is actually feasible in real trauma patients (TXA-AT group). A single dose of TXA prior to trauma significantly delayed the onset of ATC from 30min to 120min after trauma as measured by a rise in prothrombin time (PT). The plasma d-dimer as well as plasminogen/fibrinogen ratio in traumatized liver of TXA-BT were significantly lower as compared to vehicle and TXA-AT. Wet/dry weight ratio and leukocytes infiltration of lungs were significantly decreased only if TXA was administrated later, prior to resuscitation (TXA-AT). In conclusion: Limited prehospital trauma resuscitation that includes FWB and TXA may not correct established systemic ATC, but rather may improve overall outcomes of resuscitation by attenuation of acute lung injury. By contrast, TXA given prior to trauma reduced levels of fibrinolysis at the site of tissue injury and circulatory d-dimer, and delayed development of coagulopathy independent of reduction of fibrinogen levels following trauma. These findings highlight the importance of early administration of TXA in trauma, and suggest that further optimization of dosing protocols in trauma to exploit TXA’s various sites and modes of action may further improve patient outcomes.

Topical tranexamic acid inhibits fibrinolysis more effectively when formulated with self-propelling particles

BACKGROUND

Endogenous fibrinolytic activation contributes to coagulopathy and mortality after trauma. Administering tranexamic acid (TXA), an antifibrinolytic agent, is one strategy to reduce bleeding; however, it must be given soon after injury to be effective and minimize adverse effects. Administering TXA topically to a wound site would decrease the time to treatment and could enable both local and systemic delivery if a suitable formulation existed to deliver the drug deep into wounds adequately.

OBJECTIVES

To determine whether self-propelling particles could increase the efficacy of TXA.

METHODS

Using previously developed self-propelling particles, which consist of calcium carbonate and generate CO2 gas, TXA was formulated to disperse in blood and wounds. The antifibrinolytic properties were assessed in vitro and in a murine tail bleeding assay. Self-propelled TXA was also tested in a swine model of junctional hemorrhage consisting of femoral arteriotomy without compression.

RESULTS

Self-propelled TXA was more effective than non-propelled formulations in stabilizing clots from lysis in vitro and reducing blood loss in mice. It was well tolerated when administered subcutaneously in mice up to 300 to 1000 mg/kg. When it was incorporated in gauze, four of six pigs treated after a femoral arteriotomy and without compression survived, and systemic concentrations of TXA reached approximately 6 mg/L within the first hour.

CONCLUSIONS

A formulation of TXA that disperses the drug in blood and wounds was effective in several models. It may have several advantages, including supporting local clot stabilization, reducing blood loss from wounds, and providing systemic delivery of TXA. This approach could both improve and simplify prehospital trauma care for penetrating injury.

Acquired Factor V Deficiency Associated with CFPM Administration

BACKGROUND

Acquired factor V deficiency (AFVD) caused by Factor V (FV) inhibition is a rare event, characterized by prolonged prothrombin time and activated partial thromboplastin time. To date, various factors were reported as triggers for developing FV inhibitor. Clinical symptoms range from asymptomatic to life-threatening bleeding. Case Report and Conclusions: Here, we report an 84-year-old Japanese male on hemodialysis due to renal failure who developed subcutaneous hemorrhage after administration of cefepime (CFPM) to treat bacteremia. Deficient FV activity (< 1.0%) was identified and AFVD with FV inhibitor titer of 9 BU/mL was diagnosed. Although the patient had multiple risks for developing FV inhibitor, CFPM was thought to be the major culprit in this case. After the diagnosis, oral prednisolone (30 mg/day) was initiated, but the patient died of respiratory/cardiac failure, unrelated to AFVD.

Trauma-targeted delivery of tranexamic acid improves hemostasis and survival in rat liver hemorrhage model

BACKGROUND

Trauma-associated hemorrhage and coagulopathy remain leading causes of mortality. Such coagulopathy often leads to a hyperfibrinolytic phenotype where hemostatic clots become unstable because of upregulated tissue plasminogen activator (tPA) activity. Tranexamic acid (TXA), a synthetic inhibitor of tPA, has emerged as a promising drug to mitigate fibrinolysis. TXA is US Food and Drug Administration-approved for treating heavy menstrual and postpartum bleeding, and has shown promise in trauma treatment. However, emerging reports also implicate TXA for off-target systemic coagulopathy, thromboembolic complications, and neuropathy.

OBJECTIVE

We hypothesized that targeted delivery of TXA to traumatic injury site can enable its clot-stabilizing action site-selectively, to improve hemostasis and survival while avoiding off-target effects. To test this, we used liposomes as a model delivery vehicle, decorated their surface with a fibrinogen-mimetic peptide for anchorage to active platelets within trauma-associated clots, and encapsulated TXA within them.

METHODS

The TXA-loaded trauma-targeted nanovesicles (T-tNVs) were evaluated in vitro in rat blood, and then in vivo in a liver trauma model in rats. TXA-loaded control (untargeted) nanovesicles (TNVs), free TXA, or saline were studied as comparison groups.

RESULTS

Our studies show that in vitro, the T-tNVs could resist lysis in tPA-spiked rat blood. In vivo, T-tNVs maintained systemic safety, significantly reduced blood loss and improved survival in the rat liver hemorrhage model. Postmortem evaluation of excised tissue from euthanized rats confirmed systemic safety and trauma-targeted activity of the T-tNVs.

CONCLUSION

Overall, the studies establish the potential of targeted TXA delivery for safe injury site-selective enhancement and stabilization of hemostatic clots to improve survival in trauma.

Termination of bleeding by a specific, anticatalytic antibody against plasmin

BACKGROUND

Excessive, plasmin-mediated fibrinolysis augments bleeding and contributes to death in some patients. Current therapies for fibrinolytic bleeding are limited by modest efficacy, low potency, and off-target effects.

OBJECTIVES

To determine whether an antibody directed against unique loop structures of the plasmin protease domain may have enhanced specificity and potency for blocking plasmin activity, fibrinolysis, and experimental hemorrhage.

METHODS

The binding specificity, affinity, protease cross-reactivity and antifibrinolytic properties of a monoclonal plasmin inhibitor antibody (Pi) were examined and compared with those of epsilon aminocaproic acid (EACA), which is a clinically used fibrinolysis inhibitor.

RESULTS

Pi specifically recognized loop 5 of the protease domain, and did not bind to other serine proteases or nine other non-primate plasminogens. Pi was ~7 logs more potent in neutralizing plasmin cleavage of small-molecule substrates and >3 logs more potent in quenching fibrinolysis than EACA. Pi was similarly effective in blocking catalysis of a small-molecule substrate as α2 -antiplasmin, which is the most potent covalent inhibitor of plasmin, and was a more potent fibrinolysis inhibitor. Fab or chimerized Fab fragments of Pi were equivalently effective. In vivo, in a humanized model of fibrinolytic surgical bleeding, Pi significantly reduced bleeding to a greater extent than a clinical dose of EACA.

CONCLUSIONS

A mAb directed against unique loop sequences in the protease domain is a highly specific, potent, competitive plasmin inhibitor that significantly reduces experimental surgical bleeding in vivo.

A Retrospective Study Comparing the Effectiveness and Safety of EXOSEAL Vascular Closure Device to Manual Compression in Patients Undergoing Percutaneous Transbrachial Procedures

BACKGROUND

This study aimed to assess the safety and efficacy of EXOSEAL vascular closure device (EVCD) insertion by comparing its performance with manual compression (MC) in achieving hemostasis at the brachial artery puncture site.

METHODS

A retrospective study of brachial artery access by using either MC or EVCD for achieving hemostasis from March 2016 to October 2017 was conducted. Patients with Stanford type B aortic dissection (TBAD) undergoing percutaneous transbrachial procedures were included. Time to hemostasis (TTH) was the primary efficacy end point. Seven-day incidence of major access site-related complications was the primary safety end point. TTH and major and minor complications associated with treatment of these 2 groups were also evaluated.

RESULTS

A total of 157 patients with TBAD undergoing percutaneous transbrachial procedures entered the analysis. Of these, 107 patients underwent EVCD insertion and 50 patients underwent MC. The baseline characteristics of the 2 groups were similar. TTH was significantly shorter for EVCD over MC (P < 0.05). The TTH ≥10 min in the MC group was 100.0% (n = 50), but in the EVCD group, it was ≤2 min, 87.9% (n = 107); 2-5 min, 7.5% (n = 107); and ≥10 min, 4.7% (n = 107). The EVCD group had several major complications, while the MC group had none. Two patients (1.9%, n = 107) required vascular repair, one patient (0.6%, n = 107) required blood transfusion, and 1 patient (0.6%, n = 107) developed upper limb numbness and weakness after EVCD deployment. Minor complication such as the occurrence of hematoma (≤5 cm) in the MC group was 4 (8.0%) but was also 4 (3.7%) in the EVCD group, showing statistically significant difference (P = 0.030). The incidence of ecchymosis was 8 (7.5%) in the EVCD group when compared with 13 (26.0%) in the MC group, which showed statistically significant difference (P = 0.001). Other major and minor complications showed no significant differences between these 2 groups.

CONCLUSIONS

After invasive procedures by 6F percutaneous access via the brachial artery in preprocedurally fully anticoagulated patients, TTH was significantly reduced in patients who underwent EVCD when compared with patients who underwent MC. MC is a safer and more convenient way to achieve hemostasis but has higher incidence of minor complications.

Women and inherited bleeding disorders - A review with a focus on key challenges for 2019

The area of women and inherited bleeding disorders has undergone quick expansion in recent years. More patients are being identified and expertise to diagnose and manage these patients is now essential for practising physicians. Programs to help educate and empower patients and caregivers are now in place. Common inherited bleeding disorders affecting women include von Willebrand disease (VWD), inherited platelet disorders, and rare inherited bleeding disorders such as factor VII (FVII) deficiency and factor XI (FXI) deficiency. Specific clinical tools have been developed to help clinicians and patients screen for the presence of these bleeding disorders in both adult and pediatric populations. Affected women can experience heavy menstrual bleeding and resulting iron deficiency anemia, postpartum hemorrhage, and hemorrhagic ovarian cysts which need to be properly managed. Excessive bleeding can adversely affect quality of life in these women. Front line therapy for bleeding in mild cases focuses on the use of non-specific hemostatic agents such as DDAVP ®, tranexamic acid and hormonal agents but specific factor replacement and/or blood products may be required in more severe cases, in severe bleeding or as second line treatment when bleeding is not responsive to first line agents. Iron status should be optimised in these women especially in pregnancy and use of an electronic app can now help clinicians achieve this. These patients should ideally be managed by a multidisciplinary team whenever possible even remotely. Although clinical research has closed some knowledge gaps regarding the diagnosis and management of these women, there remains significant variation in practise and lack of evidence-based guidelines still exists in many spheres of clinical care in which caregivers must rely on expert opinion. Ongoing efforts in education and research will continue to improve care for these women and restore quality of life for them.

Risk of thromboembolic and bleeding outcomes following hematological cancers: A Danish population-based cohort study

BACKGROUND

Therapeutic advances have improved survival after hematological cancers. In turn, patients may be at increased risk of thromboembolic and bleeding events.

OBJECTIVES

To examine the risks of myocardial infarction (MI), ischemic stroke, venous thromboembolism (VTE), and bleeding requiring hospital contact in patients with hematological cancers.

METHODS

We conducted a Danish population-based cohort study (2000-2013). We identified all adult hematological cancer patients and sampled a general population comparison cohort in a 1:5 ratio matched by age, sex, previous thromboembolic events, bleeding, and solid cancer. Ten-year absolute risks of thromboembolism and bleeding were calculated and hazard ratios (HRs) were computed, controlling for matching factors.

RESULTS

Among 32 141 hematological cancer patients, the 10-year absolute risk of any thromboembolic or bleeding complication following hematological cancer was 19%: 3.3% for MI, 3.5% for ischemic stroke, 5.2% for VTE, and 8.5% for bleeding. Except among patients with myeloid leukemia, acute lymphoid leukemia, or myelodysplastic syndrome, the risk of thromboembolic events surpassed that of bleeding. The hematological cancer cohort overall was at increased risk for MI [HR = 1.36, 95% confidence interval (CI): 1.25-1.49], ischemic stroke (HR = 1.22, 95% CI: 1.12-1.33), VTE (HR = 3.37, 95% CI: 3.13-3.64), and bleeding (HR = 2.39, 95% CI: 2.26-2.53) compared with the general population.

CONCLUSIONS

Approximately 2 of 10 hematological cancer patients experienced MI, ischemic stroke, VTE, or bleeding requiring hospital contact within 10 years. The hematological cancer cohort had higher hazards of MI, ischemic stroke, VTE, and bleeding requiring hospital contact than a general population comparison cohort.

Drug levels and bleeding complications in atrial fibrillation patients treated with direct oral anticoagulants

Essentials Currently, DOACs are given at fixed doses and do not require laboratory monitoring. Direct oral anticoagulant-specific measurements were performed at trough and peak. Patients who developed bleeding events showed higher DOAC plasma levels at peak. This study suggests the need of a more accurate DOAC dose assessment.

BACKGROUND

Direct oral anticoagulants (DOACs) are administered at fixed dose. The aim of the study was to evaluate the relationship between DOAC C-trough or C-peak plasma levels and bleeding complications in patients with non-valvular atrial fibrillation (NVAF).

METHODS

Five hundred sixty five consecutive naive NVAF patients were enrolled. The DOAC measurements at C-trough and at C-peak (available in 411 patients) were performed at steady state, within the first month of treatment. Major bleeding (MB), clinically relevant non-major bleeding (CRNMB), and minor bleeding (MinB), occurring during 1 year of follow-up after blood sampling, were recorded. For each DOAC, interval of C-trough and C-peak levels was subdivided into four equal classes and results were attributed to these classes; the median values of results were also calculated.

RESULTS

Two hundred eight patients were on apixaban, 185 on dabigatran, and 172 on rivaroxaban. For 1-[qqqdeletezzz] year follow up for all patients, we observed: 19 MB (3.36%), 6 CRNMB (1.06%), and 47 MinB (8.31%). The prevalence of bleeding patients with anticoagulant levels in the upper classes of C-peak activity (II + III + IV) was higher than that in the lowest class. Normalized results of C-peak levels were higher in patients with bleeding than in those without bleeding.

CONCLUSIONS

Bleeding complications during DOAC treatment were more frequent among atrial fibrillation (AF) patients with higher C-peak anticoagulant levels. In addition to a previous study that showed an increased risk of thrombotic complications in the patients with low C-trough levels, this study seems to indicate that patients with NVAF on DOACs would need a more accurate definition of their optimal therapeutic window.