Platelet Hemostasis Research Articles

Hemostasis in patients with primary myelofibrosis treated with ruxolitinib

Aim. To evaluate the effect of ruxolitinib therapy on hemostasis in patients with primary myelofibrosis (PMF).Materials and methods. 30 patients with PMF were examined, 16 of them received ruxolitinib (group 1) at the time of examination and 14 were untreated (group 2). The control group consisted of 30 healthy individuals. A complete blood count was performed, the platelets aggregation, the activity of Willebrand factor, factor VIII and natural anticoagulants were evaluated. In the thrombin generation test, the endogenous thrombin potential (ETP, nM×min) was determined; sensitivity to thrombomodulin and coagulation index were calculated. Kruskal-Wallis test with post hoc Dunn test was used to compare groups.Results. Hemoglobin and platelet count were lower in group 1 compared to group 2 and control. Platelet aggregation with collagen was lower in patients with PMF than in the control group, and lower in group 1 than in group 2: 2.2 (1.6; 5.7) % vs 41.6 (3.4; 64.8) %, p < 0.05. In patients in group 1, the activity of Willebrand factor – 150.0 (122.5; 195) % and factor VIII – 173 (148.5; 200) % was higher (p < 0.05) than in the control: 97 (84.8; 110) % and 104 (85; 130) % respectively. Antithrombin did not differ in the PMF and control group. Protein S was reduced in both groups with PMF: group 1 – 70 (58; 86,6) %, group 2 – 65 (43,6; 107,5) %, control – 102 (86; 109,0) %, p < 0.001. ETP and sensitivity to thrombomodulin in groups 1 and 2 were low, p < 0.001. The coagulation index tended to higher values than in the control: 5.3 (3.0; 11.4) – group 1; 3.2 (2.4; 7.3) – group 2; control – 1.9 (1.6; 2.2), p = 0.073.Conclusion. Ruxolitinib therapy leads to the failure of the platelet hemostasis, the procoagulant activity of plasma with an increase in the activity of Willebrand factor and factor VIII and a decrease in the activity of protein S.

Peculiarities of Hemostasis and Proteomics in Patients With Acute Myocardial Infarction and Healthy Volunteers After SARS-CоV-2 Infection.

To identify the features of plasma, platelet hemostasis, and proteomic composition of the blood plasma in patients with acute myocardial infarction (AMI) and healthy volunteers after COVID-19. The study included patients with AMI who have recently had COVID-19 (AMI-post-COVID, n=56) and patients with AMI who have not recently had COVID-19 (AMI-control, n=141). Healthy volunteers constituted the control groups and were also divided into control-post-COVID (n=32) and control-control (n=71) groups. Previous SARS-CoV-2 infection was determined by anti-N IgG in the blood serum, the level of which persists for 6-10 months after the disease. Hemostasis was evaluated by thromboelastometry (on whole blood), thrombodynamics (on platelet-poor plasma), fibrinolysis, impedance aggregometry, and proteomic analysis. The AMI-post-COVID and AMI-control groups had higher values of thrombus growth rate, size and density based on the data of thromboelastometry and thrombodynamics, as well as increased concentrations of the complement system components, proteins regulating the state of the endothelium, and a number of acute-phase and procoagulant proteins compared to the control groups. Furthermore, in the AMI-post-COVID group, compared to the AMI-control group, the thrombus density was lower, and its lysis rates were higher when measured by the thrombodynamics method on platelet-poor plasma, while the platelet aggregation induced by ADP and thrombin was higher. Also, in the control-post-COVID group, compared to the control-control group, the thrombus formation rate was lower, whereas, in contrast, the thrombus size as measured by the thrombodynamics method and the platelet aggregation induced by arachidonic acid and thrombin were higher. In addition, in the AMI-post-COVID group, compared to the AMI-control group, the concentrations of proteins involved in inflammation and hemostasis were lower. Patients with AMI who have recently had COVID-19 are characterized by a less pronounced activation of the immune response compared to patients with AMI who have not had COVID-19. This may be due to long-term chronic inflammation and depletion of components of the immune activation system after SARS-CoV-2 infection. Long-term activation of the hemostasis system in both patients with AMI and healthy volunteers after COVID-19 is primarily due to the platelet component of hemostasis.

Analysis of platelet hemostasis in patients on the background of dual antiplatelet therapy for 12 months

Analysis of platelet hemostasis in patients on the background of dual antiplatelet therapy for 12 months

Interaction between warfarin and selected superfoods: a comprehensive review of potential mechanisms and their clinical significance

Warfarin is one of the oldest and still widely used anticoagulant agents. Interactions between warfarin and herbs have been intensively studied in recent years. However, due to the growing worldwide interest and consumption of herbal products this area requires further investigations. Patients on warfarin should receive special attention from their physicians, especially concerning the concomitant use of herbal products. In this study, we provide a comprehensive review of the mechanisms and clinical significance of interactions between warfarin and selected plants, also frequently referred to as superfoods: Linum usitatissimum, Moringa oleifera, Lindera aggregata, and Nigella sativa. We carried out a non-systematic review of the literature using PubMed using the key terms: warfarin, interaction, Linum usitatissimum, Moringa oleifera, Lindera aggregata, Nigella sativa, CYP2C9, CYP3A4, serum albumin, blood coagulation, antiplatelet. We analyzed articles published up to 2024. The wealth of phytoconstituents contained in reviewed plants favor the occurrence of potential interactions with warfarin. Possible mechanisms involved in these interactions include plasma and platelet hemostasis processes and warfarin pharmacokinetics, i.e. distribution and hepatic metabolism. Critical evaluation of the risk of warfarin-herb interaction is challenging and still inconclusive because most of the sources of evidence are in vitro and animal studies. Therefore we expect human clinical studies evaluating the risk of combined use of warfarin and discussed plants in the near future. To summarize, we hope that the results of our study will help healthcare professionals in their daily practice and improve the safety and effectiveness of warfarin pharmacotherapy.

Advances in Platelet-Dysfunction Diagnostic Technologies.

The crucial role of platelets in hemostasis and their broad implications under various physiological conditions underscore the importance of accurate platelet-function testing. Platelets are key to clotting blood and healing wounds. Therefore, accurate diagnosis and management of platelet disorders are vital for patient care. This review outlines the significant advancements in platelet-function testing technologies, focusing on their working principles and the shift from traditional diagnostic methods to more innovative approaches. These improvements have deepened our understanding of platelet-related disorders and ushered in personalized treatment options. Despite challenges such as interpretation of complex data and the costs of new technologies, the potential for artificial-intelligence integration and the creation of wearable monitoring devices offers exciting future possibilities. This review underscores how these technological advances have enhanced the landscape of precision medicine and provided better diagnostic and treatment options for platelet-function disorders.

Platelets, inflammation, and purinergic receptors in chronic kidney disease

Platelets are anucleated cells that circulate in the bloodstream. Historically, platelets were thought to perform a singular function—stop bleeding via clotting. While platelets do play a key role in hemostasis and thrombosis, recent studies indicate that platelets also modulate inflammation, and this platelet-induced inflammation contributes to the pathophysiology of various diseases such as atherosclerosis and diabetes mellitus. Thus, in recent years, our understanding of platelet function has broadened. In this review, we revisit the classic role of platelets in hemostasis and thrombosis and describe the newly recognized function of platelets in modulating inflammation. We cover the potential use of purinergic receptor antagonists to prevent platelet-modulated inflammation, particularly in patients with chronic kidney disease, and finally, we define key questions that must be addressed to understand how platelet-modulated inflammation contributes to the pathophysiology of chronic kidney disease.

Platelet Membrane-Coated r-SAK Improves Thrombolytic Efficacy by Targeting Thrombus.

Thrombolytic therapy is one of the most effective treatments for thrombus dissolution and recanalization of blocked vessels in thrombotic diseases. However, the application of the thrombolytic strategy has been limited due to unsatisfactory thrombolytic efficacy, relatively higher bleeding complications, and consequently restricted indications. Recombinant staphylokinase (r-SAK) is a third-generation thrombolytic agent produced by genetic engineering technology, which exhibits a better thrombolytic efficacy than urokinase and recombinant streptokinase. Inspired by the natural affinity of platelets in hemostasis and pathological thrombosis, we developed a platelet membrane (PM)-coated r-SAK (PM-r-SAK). Results from animal experiments and human in vitro studies showed that the PM-r-SAK had a thrombolytic efficacy equal to or better than its 4-fold dose of r-SAK. In a totally occluded rabbit femoral artery thrombosis model, the PM-r-SAK significantly shortened the initial recanalization time compared to the same dose and 4-fold dose of r-SAK. Regarding the recanalized vessels, the PM-r-SAK prolonged the time of reperfusion compared to the same dose and 4-fold dose of r-SAK, though the differences were not significant. An in vitro thrombolytic experiment demonstrated that the thrombolytic efficacy of PM-r-SAK could be inhibited by platelet-poor plasma from patients taking aspirin and ticagrelor. PM coating significantly improves the thrombolytic efficacy of r-SAK, which is related to the thrombus-targeting activity of the PM-r-SAK and can be inhibited by aspirin- and ticagrelor-treated plasma.

Alternative Methods for the Detection of Superoxide Anion Generation in Platelets.

Reactive oxygen species (ROS) are highly unstable oxygen-containing molecules. Their chemical instability makes them extremely reactive and gives them the ability to react with important biological molecules such as proteins, nucleic acids, and lipids. Superoxide anions are important ROS generated by the reduction of molecular oxygen reduction (i.e., acquisition of one electron). Despite their initial implication exclusively in aging, degenerative, and pathogenic processes, their participation in important physiological responses has recently become apparent. In the vascular system, superoxide anions have been shown to modulate the differentiation and function of vascular smooth muscle cells, the proliferation and migration of vascular endothelial cells in angiogenesis, the immune response, and the activation of platelets in hemostasis. The role of superoxide anions is particularly important in the dysregulation of platelets and the cardiovascular complications associated with a plethora of conditions, including cancer, infection, inflammation, diabetes, and obesity. It has, therefore, become extremely relevant in cardiovascular research to be able to effectively measure the generation of superoxide anions byhuman platelets,understand the redox-dependent mechanisms regulating the balance between hemostasis and thrombosis and, eventually,identify novel pharmacological tools for the modulation of platelet responses leading to thrombosis and cardiovascular complications. This study presents three experimental protocols successfully adopted for the detection of superoxide anions in platelets and the study of the redox-dependent mechanisms regulating hemostasis and thrombosis: 1) dihydroethidium (DHE)-based superoxide anion detection by flow cytometry; 2) DHE-based superoxide anion visualization and analysis by single platelet imaging; and 3) spin probe-based quantification of superoxide anion output in platelets by electron paramagnetic resonance (EPR).

Correction of endothelial dysfunction in patients with type 2 diabetes mellitus, diabetic kidney disease and non-alcoholic steatohepatitis

Background. Non-alcoholic fatty liver disease and chronic kidney disease are public health concerns worldwide due to their increasing prevalence, adverse prognosis, and health care burden. The purpose of the study was to determine the probable effect of a combination of metformin, rosuvastatin, essential phospholipids and quercetin on the blood lipids, endothelial function, fibrinolysis system and platelet hemostasis, which are factors for the progression of nonalcoholic steatohepatitis. Materials and methods. Studies were performed on the dynamics of treatment in 60 patients with non-alcoholic fatty liver disease, type 2 diabetes mellitus and diabetic kidney disease (stage I–III). Depending on the prescribed treatment at random, the examined patients were divided into 2 groups. Twenty-eight persons of the first group received a low-calorie diet with dietary restrictions, essential phospholipids, metformin hydrochloride, rosuvastatin. Thirty-two patients from the second group received quercetin in addition to similar dietary recommendations, essential phospholipids, hypoglycemic and hypolipidemic therapy. The mean age of patients was 53.80 ± 3.52 years. The comparison group consisted of 30 healthy individuals of the corresponding age. Results. To evaluate the degree of endothelial-protective effect of quercetin on the background of the recommended protocol therapy, markers of endothelial dysfunction, fibrinolysis and platelet hemostasis were studied. NO content significantly reduced (1.7 times) in patients of group 2 before treatment, increased by 1.5 times (p < 0.05). This can be explained by the effect of quercetin, as well as the use of metformin, which reduces the degree of insulin resistance and the level of hyperlipidemia. Conclusions. The effectiveness of a combination therapy for non-alcoholic steatohepatitis and type 2 diabetes mellitus with diabetic kidney disease using essential phospholi­pids, statins and metformin with the addition of quercetin is higher than that of traditional therapy, as it significantly restores the functional state of the endothelium, eliminates the phenomena of hypercoagulation syndrome without the additional prescription of antiplatelet agents.

The Model for Clinical, Laboratory, and Genetic Prediction of Recurrent Ischemic Stroke against the Background of Laboratory Aspirin Resistance using Machine Learning

The aim of the study was to determine the incidence of laboratory aspirin resistance; and to study the associations of genetic markers and clinical and laboratory parameters (including parameters of the platelet hemostasis) in patients with non-cardioembolic ischemic stroke using machine learning methods to assess the prognosis of recurrent ischemic strokes. Clinical and laboratory data (including induced platelet aggregation) were analyzed from 296 patients with ischemic stroke who were treated in the stroke center of City Clinical Hospital No. 1 named after. N.I. Pirogov. The frequencies of polymorphic variants of the ITGB3, GPIba, TBXA2R, ITGA2, PLA2G7, HMOX1, PTGS1, PTGS2, ADRA2A, ABCB1, PEAR1 genes and intergenic region 9p21.3) in patients with non-cardioembolic ischemic stroke, which were identified using hydrogel biochip technology, were determined. Using the developed machine learning model, additional clinical and genetic factors influencing the development of laboratory aspirin resistance and recurrent ischemic stroke were studied. In the future, the identified factors can be used for differentiated prevention of recurrent ischemic strokes.

Platelets in Hemostasis, Thrombosis, and Inflammation After Major Trauma.

Trauma currently accounts for 10% of the total global burden of disease and over 5 million deaths per year, making it a leading cause of morbidity and mortality worldwide. Although recent advances in early resuscitation have improved early survival from critical injury, the mortality rate in patients with major hemorrhage approaches 50% even in mature trauma systems. A major determinant of clinical outcomes from a major injury is a complex, dynamic hemostatic landscape. Critically injured patients frequently present to the emergency department with an acute traumatic coagulopathy that increases mortality from bleeding, yet, within 48 to 72 hours after injury will switch from a hypocoagulable to a hypercoagulable state with increased risk of venous thromboembolism and multiple organ dysfunction. This review will focus on the role of platelets in these processes. As effectors of hemostasis and thrombosis, they are central to each phase of recovery from injury, and our understanding of postinjury platelet biology has dramatically advanced over the past decade. This review describes our current knowledge of the changes in platelet behavior that occur following major trauma, the mechanisms by which these changes develop, and the implications for clinical outcomes. Importantly, supported by research in other disease settings, this review also reflects the emerging role of thromboinflammation in trauma including cross talk between platelets, innate immune cells, and coagulation. We also address the unresolved questions and significant knowledge gaps that remain, and finally highlight areas that with the further study will help deliver further improvements in trauma care.

ТРУДНОСТИ ВЕРИФИКАЦИИ ПРИЧИН ГЕМОРРАГИЧЕСКОГО СИНДРОМА В ПРАКТИКЕ ВРАЧА-НЕОНАТОЛОГА

Problems related to the study of the coagulation status of patients during the neonatal period are well known to neonatologists. Hemorrhagic disorders in the period of the newborn can be caused by deficiency of vitamin K-dependent factors, intrauterine infection, hereditary coagulopathy, primary and secondary disorders of platelet hemostasis and a number of other reasons. Clinical manifestations of hemorrhagic syndrome in a newborn child are non-specific, allowing to suspect the type of blood flow, however, conducting selective hemostatic therapy is possible only after laboratory identification of the disease. Among congenital coagulopathies, hemophilia A is the most frequently encountered, while clinical manifestations of the disease occur during the neonatal period only in the case of the presence of a severe form of the disease. Meanwhile, in the practice of pediatricians and neonatologists, vascular tumors are encountered quite rarely, including Kazabach-Merritt syndrome – a potentially life-threatening condition in which hemangioendotheliomas grow rapidly and reach gigantic sizes, combined with severe thrombocytopenia and coagulopathy. In this article, two clinical cases of severe hemophilia A in newborn boys with basic factor VIII activity of less than 1% are presented, as well as a case of infantile hemangioendothelioma of the liver in a newborn baby. In the article, the directions of the laboratory search for disorders of primary and secondary hemostasis were analyzed, which allowed the diagnosis to be clarified and the appropriate hemostatic therapy to be selected.

СЛУЧАЙ НАСЛЕДСТВЕННОГО НАРУШЕНИЯ СВЕРТЫВАНИЯ КРОВИ В РАННЕМ НЕОНАТАЛЬНОМ ПЕРИОДЕ

The article describes a case of bleeding that occurred on the first day of life in an infant with severe hemophilia A, analyzes the directions of clinical and laboratory search for disorders of the primary and secondary blood coagulation, which made it possible to clarify the diagnosis and select appropriate hemostatic therapy. Hemorrhagic disorders in the neonatal period can be caused by a deficiency of vitamin K-dependent factors, intrauterine infection, hereditary coagulopathies, primary and secondary disorders of platelet hemostasis and a number of other reasons. Clinical manifestations of hemorrhagic syndrome in a newborn child are nonspecific; they allow one to suspect the type of bleeding, but not identify the cause of the bleeding. Additional studies reflecting the viscoelastic properties of the clot have made it possible to evaluate the effectiveness of hemostatic therapy. To clarify the true cause of bleeding, in addition to thorombeastography, it became necessary to supplement the examination of the child with factor analysis based on classical clotting tests. In terms of diagnosing blood coagulation disorders, thromboelastography had no advantages over classical factor analysis.

Laporan Kasus : Feline Immunodeficiency Virus pada Kucing Moi di Surabaya

Feline immunodeficiency (FIV) is a disease caused by retroviridae of the lentivirus genus and is dangerous for cats. This virus attacks the cat's immune system. FIV disease can be transmitted horizontally via as saliva and body fluids. 5-month-old black and white Persian cat named Moi, brought by the owner with complaints of vomiting yesterday, refusing to eat and drink, soft stool, no coughing and sneezing, weakness. On physical examination showed a temperature of 40.1 °C with a body weight of 1.5 kg, clinical symptoms were found in the form of gingivitis, canker sores, conjunctivitis, pale pink mucous membranes, fever, flu symptoms from the nose with clear discharge, crepitus in both ears. Diagnosis of Moi Cats based on anamnesis, physical examination, clinical symptoms, and supporting examinations is diagnosed with Feline immunodeficiency virus (FIV). Case are treated using a combination of antibiotics, anti-inflammatories, fluid therapy, antiemetics, gastrointestinal linings, immune boosters, blood boosters, and cardiac pacemakers. After 4 days the cat Moi was declared dead due to failure of platelet hemostasis, bleeding, and heart failure.

Screening for Key Structural Differences in Thrombosis Versus Hemostasis through Single Platelet Analysis

INTRODUCTION: Taking a single platelet analysis (SPA) approach to score platelet activation states distribution within a thrombus provides a unique opportunity to examine cellular difference in the process of thrombotic versus hemostatic clot formation. Potentially, it may reveal platelet activation states are dispensable for hemostasis but critical for thrombosis, e.g., platelet infill within the interior cavities of thrombus. Hence, our goal of determining the distribution of platelet activation states and of a-granule content release in an occlusive clot compared to a hemostatic thrombus. METHODS: We used a femoral artery model in mice in which occlusive clots were induced by ferric chloride and hemostatic processes occurred within a puncture wound. Images were produced by wide area transmission electron microscopy of full thrombi cross sections, 3.185 nm XY pixel size, at various depths. We mapped and analyzed 2D images of ferric chloride induced clotting using automated SPA with locally run Zeiss Arivis Pro software. Through automated SPA, we segmented and mapped the distribution of tens of thousands of platelets and trapped red blood cells versus the vessel wall and associated vascular damage. The incidence of condensed and decondensed a-granules, an indicator of platelet secretion activity, was scored through Cloud implemented APEER models. Occlusive clot cross sections were analyzed at multiple scales to reveal the distribution of platelet activation states based on platelet shape or to reveal a-granule release state (condensed versus decondensed granules). For the simpler problem of SPA of puncture wound hemostasis, we manually scored platelet activation states across tens of thousands of platelets. RESULTS AND CONCLUSIONS: With respect to occlusive clotting, several significant results and conclusions emerged from the platelet shape analysis. In the occlusive clot, we observed that activated platelets adhering directly to the damaged area of the vessel wall, exposed intima, lost their shape, becoming oval with extended pseudopods to more compressed, compacted tightly adherent shape compared to circulating, discoid platelets. Tightly adherent platelets formed column-like projections that structured the interior of the clot. Alpha-granule secretion was apparent. Most interestingly, the interior space between columns was filled with loosely adherent elongated, discoid-shaped platelets that frequently contained decondensed a-granules indicative of granule release (Figure 1). To the best of our knowledge, these data are the first indications that discoid platelets can secrete at least partially, their a-granule contents. In addition to platelets in various activation states, ~7% of the clot cross-sectional area was occupied by shape distorted red blood cells trapped in clusters. Any morphological effect of the red blood cells on platelet activation was restricted to a short distance of ~5 microns. Our SPA analysis of the femoral artery, puncture wound thrombi, support at least two conclusions: 1) Decondensed a-granules were abundant in discoid platelets coating the intravascular “crown” of the 20 min post puncture thrombus, i.e., a-granule secretion by discoid platelet is found in both hemostasis and thrombosis. 2) Circular folding of the hemostatic thrombus to give complete infill of the artery would place discoid platelets within central interior portions of an occlusive clot. We suggest that there may well be shared principles of assembly between the two situations. Importantly, the intravascular accumulation of discoid platelets in hemostasis occurs post-bleeding cessation. Therefore, drugs selectively affecting this state would target preferentially thrombotic clots in which clot infill results in the accumulation of discoid platelets. Figure 1: Distribution of platelets within a cross section through the middle of a ferric chloride induced, occlusive femoral clot. A)Platelet rich clot showing extensive platelet adhesion to the intima, white line encircling the platelet rich clot, inset blowup of the centrally located discoid platelets B) Distribution of red blood cells (red) and elongated, discoid shaped platelets (yellow). C) Cloud based SPA of red blood cells, platelets (yellow), condensed a-granules (light blue) and decondensed a-granules (magenta). D) Global distributions of granules (light blue and magenta) relative to platelets.

The influence of temperature on platelet hemostasis induced by various agonists

The influence of temperature on platelet hemostasis induced by various agonists

Hemostasiological Aspects of PCI: Periprocedural Changes in the Activity of the Platelet Link of Hemocoagulation on the Background of Prior Double Antiplatelet Therapy in Patients with Chronic Coronary Syndrome

The aim. To analyze changes in the activity of the platelet link of hemocoagulation in patients with chronic coronary syndrome before and after percutaneous coronary intervention (PCI) against the background of prior antiplatelet therapy.
 Materials and methods. We examined 67 patients (mean age 65.2±8.6 years) who were undergoing inpatient treatment at the National Amosov Institute of Cardiovascular Surgery of the National Academy of Medical Sciences of Ukraine. Patients with different regimens of antiplatelet therapy were compared before and after PCI. At the time of hospitalization, patients were receiving both monotherapy and dual antiplatelet therapy (those with a history of myocardial infarction up to 12 months) in standard doses. The control group consisted of 25 people of similar age (62.7±6.5 years). The activity of platelet hemostasis was evaluated by the turbidimetric method and the light transmission fluctuation method. Statistical processing was carried out using the MedStat v.5.2 and Statistica 8.0 software.
 Results. Before PCI, dual antiplatelet therapy using aspirin and ticagrelor suppressed the activity of platelet hemostasis, compared to dual antiplatelet therapy with acetylsalicylic acid and clopidogrel. Patients receiving monotherapy did not achieve the desired effect. After PCI, the group of patients who took the combination of aspirin and ticagrelor responded better to the therapy than those who received aspirin and clopidogrel.
 Conclusions. The use of dual antiplatelet therapy with acetylsalicylic acid and ticagrelor reduced both spontaneous and induced aggregation.

Molecular mechanisms of catch bonds and their implications for platelet hemostasis.

Adhesive molecular bonds between blood cells are essential for thrombosis and hemostasis as they provide means for platelet adhesion, aggregation, and signaling in flowing blood. According to the nowadays conventional definition, a "catch" bond is a type of non-covalent bio-molecular bridge, whose dissociation lifetime counter-intuitively increases with applied tensile force. Following recent experimental findings, such receptor-ligand protein bonds are vital to the blood cells involved in the prevention of bleeding (hemostatic response) and infection (immunity). In this review, we examine the up-to-date experimental discoveries and theoretical insights about catch bonds between the blood cells, their biomechanical principles at the molecular level, and their role in platelet thrombosis and hemostasis.

Coarse-grained simulations of von Willebrand factor adsorption to collagen with consequent platelet recruitment.

A multimeric glycoprotein of blood plasma-Von Willebrand factor (VWF)-mediates platelet adhesion to the fibrillar collagen of the subendothelial matrix if the blood vessel walls are damaged. The adsorption of VWF to collagen is thus essential for the initial stages of platelet hemostasis and thrombosis, as it plays a role of a molecular bridge between the injury and platelet adhesion receptors. Biomechanical complexity and sensitivity to the hydrodynamics are inherent in this system, therefore, modern computational methods supplement experimental studies of biophysical and molecular mechanisms that underlie platelet adhesion and aggregation in the blood flow. In the present paper, we propose a simulation framework for the VWF-mediated platelet adhesion to a plane wall with immobilized binding sites for VWF under the action of shear flow. VWF multimers and platelets are represented in the model by particles connected by elastic bonds and immersed in a viscous continuum fluid. This work complements the scientific field by taking into account the shape of a flattened platelet, but keeping a compromise between the detail of the description and the computational complexity of the model.

Epic Fail? Try Again

We read with interest the manuscript titled “Failure of Crotalidae Immune F(ab’)2 Equine Antivenom to Achieve Control in a Southern Pacific Rattlesnake Envenomation” by Levine et al. The authors indicate that their patient “failed to respond adequately to F(ab’)2AV” because his initially unmeasurable platelet count reached a maximum of 102,000/μL at 56 hours after envenomation. We have several concerns with this conclusion. Adequate platelet response in the setting of venom-induced hemotoxicity is not universally defined. Although some patients may have complete reversal of thrombocytopenia after a single antivenom dose, others may have increasing platelet numbers but never achieve a platelet count of >150,000/μL. A 2011 study by Yin et al1Yin S. Kokko J. Lavonas E. et al.Factors associated with difficulty achieving initial control with crotalidae polyvalent immune fab antivenom in snakebite patients.Acad Emerg Med. 2011; 18: 46-52Crossref PubMed Scopus (21) Google Scholar suggested that it “may not be reasonable to attempt to completely control” thrombocytopenia. Antivenom may have been underdosed initially. F(ab’)2AV is dosed at 10 vials over 1 hour and repeated hourly until initial control is obtained, as evidenced by the halt of proximal swelling and improvement in laboratory markers. However, as above, there is no consensus on specific numeric goals.2Anavip [Package Insert]. Franklin, TN: Rare Disease Therapeutics, Inc.Google Scholar Although the patient received 10 vials initially, his next dose approximately 1 to 2 hours later was only 4 vials. He received the remaining 6 vials after approximately 9 hours. His platelet count continued to increase. The trend suggests that earlier administration may have prevented persistent thrombocytopenia. After viper envenomation, platelets may be sequestered, pro- and anti-aggregated, and destroyed through multiple mechanisms, leading to recurrent or refractory thrombocytopenia, which is difficult to predict in the absence of routine venomic studies on individual patients. This inability to reliably predict the mechanism of thrombocytopenia results in the inability to predict platelet response to antivenom.3Shen C. Liu M. Mackeigan D.T. et al.Viper venoms drive the macrophages and hepatocytes to sequester and clear platelets: novel mechanism and therapeutic strategy for venom-induced thrombocytopenia.Arch Toxicol. 2021; 95: 3589-3599Crossref PubMed Scopus (4) Google Scholar,4De Queiroz M.R. de Sousa B.B. da Cunha Pereira D.F. et al.The role of platelets in hemostasis and the effects of snake venom toxins on platelet function.Toxicon. 2017; 133: 33-47Crossref PubMed Scopus (45) Google Scholar Owing to platelet sequestration and aggregation, antivenom should quickly reverse thrombocytopenia. However, with platelet destruction or consumption, levels would not increase until the patient could synthesize more platelets de novo. This patient may have had ongoing platelet consumption to repair venom-induced tissue damage, yet the authors did not describe the progression of cytotoxicity. The lack of fibrinogen trend also makes the inference of ongoing venom effect problematic. Rattlesnake antivenom is best suited not to resolve thrombocytopenia but to reverse defibrination, so the significance of persistent thrombocytopenia in the absence of fibrinogen levels is unclear.5Dudley S. Smelski G. Massey D.J. et al.Fashionably late: A characterization of late coagulopathies in rattlesnake envenomations between Fab and F (ab’) 2 antivenoms.Toxicon. 2022; 212: 49-54Crossref Scopus (0) Google Scholar Twenty-three years of unpublished data from the Arizona Poison and Drug Information Center shows that persistent thrombocytopenia after antivenom is common regardless of which of the two commercially available antivenoms is used (FabAV or F[ab’]2AV). Considering cases with thrombocytopenia during initial hospital stay, 197 of 556 (35.43%) FabAV patients and 39 of 107 (36.45%) F(ab’)2AV patients were discharged with a platelet count of < 150,000/μL. Some patients did not develop thrombocytopenia until after discharge. Among FabAV patients, 106 of 472 (22.46%) developed delayed thrombocytopenia compared with only 7 of 130 (5.38%) F(ab’)2AV patients. Similar rates of persistent thrombocytopenia in the inpatient setting suggest that destruction of platelets occurs in some patients regardless of antivenom manufacturer. The difference in delayed thrombocytopenia suggests that the longer half-life of F(ab’)2AV continues to protect against thrombocytopenia compared with FabAV. Finally, the authors did not provide an illustration of the patient’s overall clinical picture throughout his hospital stay, including progression of edema, pain, and coagulation factors. Isolated thrombocytopenia is not an indication to provide more antivenom as bleeding due to thrombocytopenia is unlikely if there is no defibrination. A patient with stabilization of other indicators, despite persistent thrombocytopenia, has had an adequate response to antivenom. As always in medicine, treat the patient, not the number.