Red blood cells: their dual role in thrombus formation

Hematocrit Predicts Poor Prognosis in Patients with Acute Ischemic Stroke or Transient Ischemic Attack

This study aims to investigate the association between HCT (Hematocrit) levels and adverse outcomes in patients with acute ischemic stroke (AIS) or transient ischemic attack (TIA); 14,832 participants from the China National Stroke Registry-III with AIS or TIA were analyzed. Participants were categorized into quartiles based on baseline HCT levels. The primary outcome was poor functional outcomes (modified Rankin Scale ≥ 3) during three months, with secondary outcomes including all-cause death, stroke recurrence, and combined vascular events. Logistic regression or Cox regression models were used to assess the relationship between HCT and clinical outcomes. Compared to the third quartile, patients in the lowest quartile group showed increased risk of poor functional outcome (adjusted OR: 1.35, 95% CI: 1.15-1.58, p < 0.001), patients in the lowest quartile had a higher risk of all-cause death (adjusted HR: 1.68, 95% CI: 1.06-2.68, p = 0.028), as did those in the highest quartile (adjusted HR: 2.02, 95% CI: 1.26-3.25, p = 0.004). Sensitivity analysis shows that the association of HCT with all-cause death weakened, while the association with poor functional outcome was strengthened after excluding patients with recurrent stroke. Our results indicated that HCT level could be used as a short-term predictor for poor functional outcomes and all-cause death in patients with AIS or TIA.

Effect of different acupuncture sequences of Huiyangjiuzhen acupoints on blood glucose and hemorheology in the anesthetized rabbits

Background and objective

Hemorheology and blood glucose are commonly used to estimate the risks of thrombosis and stress hyperglycemia after anaesthesia. The sequence of acupoint stimulation might influence the therapeutic effects of acupuncture. In the current study, we aimed at investigating the effect of different acupuncture sequences of "Huiyangjiuzhen" acupoints on the blood glucose and hemorheology in anesthetized rabbits.

Methods

Twenty-five rabbits were randomly divided into five groups, including the control group (CG), the positive-sequence group (PSG), the reverse-sequence group (RSG), the disorder-sequence group (DSG), and the random group (RG). Except for the CG and RG, the rabbits in other groups were acupunctured with different sequences of "Huiyangjiuzhen"acupoints when the rabbits were anesthetized. The acupoints in rabbits of the RG were chosen randomly. The levels of blood glucose and hemorheology indexes before and after anaesthesia was detected.

Results

In the PSG, Hηb 200/s, Mηb 30/s, Hηr 200/s, ERI, hematocrit and plasma viscosity levels were decreased, and the blood glucose level was not changed. In the DSG, the levels of Mηb 30/s and hematocrit were decreased, and the blood glucose was increased. In the CG, RSG and RG, no hemorheology indexes were changed and the blood glucose was increased.

Conclusion

"Huiyangjiuzhen" acupuncture could decrease the risks of post-operative thrombosis and stress hyperglycemia in anesthetized rabbits. This effectiveness depends on both acupuncture and acupuncture sequence at the "Huiyangjiuzhen" acupoints.

Inflammation as a cause of acute myocardial infarction in patients with myeloproliferative neoplasm

Myeloproliferative neoplasms (MPN) are a group of diseases characterized by the clonal proliferation of hematopoietic progenitor or stem cells. They are clinically classifiable into four main diseases: chronic myeloid leukemia, essential thrombocythemia, polycythemia vera, and primary myelofibrosis. These pathologies are closely related to cardio- and cerebrovascular diseases due to the increased risk of arterial thrombosis, the most common underlying cause of acute myocardial infarction. Recent evidence shows that the classical Virchow triad (hypercoagulability, blood stasis, endothelial injury) might offer an explanation for such association. Indeed, patients with MPN might have a higher number and more reactive circulating platelets and leukocytes, a tendency toward blood stasis because of a high number of circulating red blood cells, endothelial injury or overactivation as a consequence of sustained inflammation caused by the neoplastic clonal cell. These abnormal cancer cells, especially when associated with the JAK2V617F mutation, tend to proliferate and secrete several inflammatory cytokines. This sustains a pro-inflammatory state throughout the body. The direct consequence is the induction of a pro-thrombotic state that acts as a determinant in favoring both venous and arterial thrombus formation. Clinically, MPN patients need to be carefully evaluated to be treated not only with cytoreductive treatments but also with cardiovascular protective strategies.

Whole blood thrombin generation shows a significant hypocoagulable state in patients with decompensated cirrhosis

BACKGROUND

Patients with cirrhosis have a normal to increased thrombin generation (TG) capacity in platelet-poor plasma (PPP). By reflecting the contribution of all circulating blood cells, whole blood (WB) TG may allow a more physiological assessment of coagulation.

OBJECTIVES

We compared WB-TG vs PPP-TG in patients with cirrhosis.

METHODS

Assessment of coagulation included routine tests, factor VIII, natural anticoagulants, PPP-TG, and WB-TG. TG assays were performed with and without thrombomodulin. Twenty-five healthy subjects were included as controls.

RESULTS

We included 108 patients (Child-Pugh A/B/C, 44/24/40). Compared with controls, patients had significantly lower platelet count, longer international normalized ratio, higher FVIII, and lower levels of protein C/S and antithrombin. Regarding thrombomodulin-modified TG assays, in compensated cirrhosis, both PPP-TG and WB-TG indicated an increased TG capacity, as reflected by an endogenous thrombin potential (ETP) significantly higher than controls. In contrast, in decompensated cirrhosis, PPP-TG indicated a hypercoagulable state with increased ETP, higher peak height, and shorter time-to-peak than controls, whereas WB-TG revealed a progressive impairment of TG kinetics and total capacity, ultimately resulting in a profound hypocoagulable state in patients with Child-Pugh C cirrhosis (ie, significant prolongation of lag time and time-to-peak with reduction of both ETP and peak height). In decompensated patients, bacterial infections and severity of anemia were associated with a further reduction of both ETP and peak height.

CONCLUSION

Compensated cirrhosis is associated with an increased TG capacity. In decompensated cirrhosis, contrary to PPP-TG, which indicates hypercoagulability, WB-TG shows a significant hypocoagulable state. The clinical value of these findings deserves further investigation.

The Ways of the Virus: Interactions of Platelets and Red Blood Cells with SARS-CoV-2, and Their Potential Pathophysiological Significance in COVID-19

The hematological effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are important in COVID-19 pathophysiology. However, the interactions of SARS-CoV-2 with platelets and red blood cells are still poorly understood. There are conflicting data regarding the mechanisms and significance of these interactions. The aim of this review is to put together available data and discuss hypotheses, the known and suspected effects of the virus on these blood cells, their pathophysiological and diagnostic significance, and the potential role of platelets and red blood cells in the virus's transport, propagation, and clearance by the immune system. We pay particular attention to the mutual activation of platelets, the immune system, the endothelium, and blood coagulation and how this changes with the evolution of SARS-CoV-2. There is now convincing evidence that platelets, along with platelet and erythroid precursors (but not mature erythrocytes), are frequently infected by SARS-CoV-2 and functionally changed. The mechanisms of infection of these cells and their role are not yet entirely clear. Still, the changes in platelets and red blood cells in COVID-19 are significantly associated with disease severity and are likely to have prognostic and pathophysiological significance in the development of thrombotic and pulmonary complications.

Role of red blood cells in clinically relevant bleeding tendencies and complications

The multiple roles of red blood cells (RBCs) are often neglected as contributors in hemostasis and thrombosis. Proactive opportunities to increase RBC numbers, either acutely or subacutely in the case of iron deficiency, are critical as RBCs are the cellular elements that initiate hemostasis together with platelets and stabilize fibrin and clot structure. RBCs also possess several functional properties to assist hemostasis: releasing platelet agonists, promoting shear force-induced von Willebrand factor unfolding, procoagulant capacity, and binding to fibrin. Additionally, blood clot contraction is important to compress RBCs to form a tightly packed array of polyhedrocytes, making an impermeable seal for hemostasis. All these functions are important for patients having intrinsically poor capacity to cease bleeds (ie, hemostatic disorders) but, conversely, can also play a role in thrombosis if these RBC-mediated reactions overshoot. One acquired example of bleeding with anemia is in patients treated with anticoagulants and/or antithrombotic medication because upon initiation of these drugs, baseline anemia doubles the risk of bleeding complications and mortality. Also, anemia is a risk factor for reoccurring gastrointestinal and urogenital bleeds, pregnancy, and delivery complications. This review summarizes the clinically relevant properties and profiles of RBCs at various steps of platelet adhesion, aggregation, thrombin generation, and fibrin formation, including both structural and functional elements. Regarding patient blood management guidelines, they support minimizing transfusions, but this approach does not deal with severe inherited and acquired bleeding disorders where a poor hemostatic propensity is exacerbated by limited RBC availability, for which future guidance will be needed.

The Acute and Chronic Effects of Resistance and Aerobic Exercise in Hemostatic Balance: A Brief Review

Hemostatic balance refers to the dynamic balance between blood clot formation (coagulation), blood clot dissolution (fibrinolysis), anticoagulation, and innate immunity. Although regular habitual exercise may lower the incidence of cardiovascular diseases (CVD) by improving an individual’s hemostatic profile at rest and during exertion, vigorous exercise may increase the risk of sudden cardiac death and venous thromboembolism (VTE). This literature review aims to investigate the hemostatic system’s acute and chronic adaptive responses to different types of exercise in healthy and patient populations. Compared to athletes, sedentary healthy individuals demonstrate similar post-exercise responses in platelet function and coagulatory and fibrinolytic potential. However, hemostatic adaptations of patients with chronic diseases in regular training is a promising field. Despite the increased risk of thrombotic events during an acute bout of vigorous exercise, regular exposure to high-intensity exercise might desensitize exercise-induced platelet aggregation, moderate coagulatory parameters, and up-regulate fibrinolytic potential via increasing tissue plasminogen activator (tPA) and decreasing plasminogen activator inhibitor (PAI-1) response. Future research might focus on combining different types of exercise, manipulating each training characteristic (frequency, intensity, time, and volume), or investigating the minimal exercise dosage required to maintain hemostatic balance, especially in patients with various health conditions.

Platelet-Neutrophil Association in NETs-Rich Areas in the Retrieved AIS Patient Thrombi

Histological structure of thrombi is a strong determinant of the outcome of vascular recanalization therapy, the only treatment option for acute ischemic stroke (AIS) patients. A total of 21 AIS patients from this study after undergoing non-enhanced CT scan and multimodal MRI were treated with mechanical stent-based and manual aspiration thrombectomy, and thromboembolic retrieved from a cerebral artery. Complementary histopathological and imaging analyses were performed to understand their composition with a specific focus on fibrin, von Willebrand factor, and neutrophil extracellular traps (NETs). Though distinct RBC-rich and platelet-rich areas were found, AIS patient thrombi were overwhelmingly platelet-rich, with 90% of thrombi containing <40% total RBC-rich contents (1.5 to 37%). Structurally, RBC-rich areas were simple, consisting of tightly packed RBCs in thin fibrin meshwork with sparsely populated nucleated cells and lacked any substantial von Willebrand factor (VWF). Platelet-rich areas were structurally more complex with thick fibrin meshwork associated with VWF. Plenty of leukocytes populated the platelet-rich areas, particularly in the periphery and border areas between platelet-rich and RBC-rich areas. Platelet-rich areas showed abundant activated neutrophils (myeloperoxidase+ and neutrophil-elastase+) containing citrullinated histone-decorated DNA. Citrullinated histone-decorated DNA also accumulated extracellularly, pointing to NETosis by the activated neutrophils. Notably, NETs-containing areas showed strong reactivity to VWF, platelets, and high-mobility group box 1 (HMGB1), signifying a close interplay between these components.

EASL Clinical Practice Guidelines on prevention and management of bleeding and thrombosis in patients with cirrhosis

The prevention and management of bleeding and thrombosis in patients with cirrhosis poses several difficult clinical questions. These Clinical Practice Guidelines have been developed to provide practical guidance on debated topics, including current views on haemostasis in liver disease, controversy regarding the need to correct thrombocytopenia and abnormalities in the coagulation system in patients undergoing invasive procedures, and the need for thromboprophylaxis in hospitalised patients with haemostatic abnormalities. Multiple recommendations in this document are based on interventions that the panel feels are not useful, even though widely applied in clinical practice.

Undiagnosed polycythemia, an uncommon cause of Wallenberg syndrome: A case report

A 26‐year‐old man presented with difficulty swallowing, dizziness, hiccups, and Horner's syndrome. Clinical and neuroimaging collaboration confirmed lateral medullary syndrome. Polycythemia was identified as the only attributable risk factor. However, the cause of polycythemia could not be assessed further. Polycythemia was managed with phlebotomy.

Hemoglobin Concentration and Clinical Outcomes After Acute Ischemic Stroke or Transient Ischemic Attack

Background

Anemia or low hemoglobin can increase the risk of stroke. However, the association between hemoglobin and outcomes after stroke is uncertain. In this study, we aimed to investigate the association between hemoglobin and clinical outcomes, including mortality, poor functional outcome, stroke recurrence, and composite vascular events at 1 year.

Methods and Results

We included the patients diagnosed with acute ischemic stroke or transient ischemic attack from the Third China National Stroke Registry. We used the Cox model for mortality, stroke recurrence, and composite vascular events and the logistic model for the poor functional outcome to examine the relationship between hemoglobin and clinical outcomes. In addition, we used the restricted cubic spline to evaluate the nonlinear relationship. This study included 14 159 patients with acute ischemic stroke or transient ischemic attack. After adjusted for potential cofounders, both anemia and high hemoglobin were associated with the higher risk of mortality (hazard ratio [HR], 1.73; 95% CI, 1.39–2.15; HR, 2.71; 95% CI, 1.95–3.76) and poor functional outcome (odds ratio [OR], 1.36; 95% CI, 1.18–1.57; OR, 1.42; 95% CI, 1.07–1.87). High hemoglobin, but not anemia, increased the risk of stroke recurrence (HR, 1.37; 95% CI, 1.05–1.79) and composite vascular events (HR, 1.41; 95% CI, 1.08–1.83). There was a U‐shaped relationship between hemoglobin and mortality and poor functional outcome.

Conclusions

Abnormal hemoglobin was associated with a higher risk of all‐cause mortality, poor functional outcome, stroke recurrence, and composite vascular events. More well‐designed clinical studies are needed to confirm the relationship between hemoglobin and clinical outcomes after stroke.

From Blood to Regenerative Tissue: How Autologous Platelet-Rich Fibrin Can Be Combined with Other Materials to Ensure Controlled Drug and Growth Factor Release

The purpose of this review is to examine the latest literature on the use of autologous platelet-rich fibrin as a drug and growth factor carrier system in maxillofacial surgery. Autologous platelet-rich fibrin (PRF) is a unique system that combines properties such as biocompatibility and biodegradability, in addition to containing growth factors and peptides that provide tissue regeneration. This opens up new horizons for the use of all beneficial ingredients in the blood sample for biomedical purposes. By itself, PRF has an unstable effect on osteogenesis: therefore, advanced approaches, including the combination of PRF with materials or drugs, are of great interest in clinics. The main advantage of drug delivery systems is that by controlling drug release, high drug concentrations locally and fewer side effects within other tissue can be achieved. This is especially important in tissues with limited blood supply, such as bone tissue compared to soft tissue. The ability of PRF to degrade naturally is considered an advantage for its use as a "warehouse" of controlled drug release systems. We are focusing on this concentrate, as it is easy to use in manipulations and can be delivered directly to the surgical site. The target audience for this review are researchers and medical doctors who are involved in the development and research of PRFs further studies. Likewise, surgeons who use PRF in their work to treat patients and who advice patients to take the medicine orally.

Peripheral Blood Cytopenia and Risk of Cardiovascular Disease and Mortality

Background

Individual blood cell count abnormalities have been associated with cardiovascular disease and increased mortality. In this study, we defined a “cytopenia phenotype,” reflecting bone marrow hypoproliferation, to determine if peripheral blood cytopenia is associated with increased cardiovascular disease and mortality risk.

Methods and Results

Study participants were derived from a biracial observational cohort study, REGARDS (Reasons for Geographic and Racial Differences in Stroke), that enrolled 30 239 Black and White participants aged ≥45 years between 2003 and 2007. Median follow up was ≈9 years. The current study included 19 864 participants from REGARDS study (37.9% men, 40% Black participants) who have complete blood count available at study enrollment. We defined a cytopenia phenotype based on age‐, sex‐, and race‐adjusted lowest fifth percentile of blood counts. Multivariable Cox proportional hazards models estimated the hazard ratios (HR) and 95% CI of cytopenia for mortality and incident cardiovascular disease in adjusted models. Mean age of the study participants was 64 years (SD:9.7). The prevalence of cytopenia was 1.9% (n=378). Cytopenia was associated with increased risk of all‐cause mortality (HR, 1.73; 95% CI, 1.34–2.22) and cardiovascular disease mortality (HR, 1.56; 95% CI, 1.11–2.29). Cytopenia was associated with stroke risk in Black but not White participants (HR, 1.96 versus 0.86; P‐interaction for race=0.08) and was not associated with coronary heart disease risk.

Conclusions

We defined a cytopenia phenotype with clinical implications for mortality and stroke risk in a large biracial and geographically diverse population. Whether generated through somatic mutations or decreased organ function, cytopenia was associated with mortality risk and was a race‐specific risk factor for stroke.

Physical forces regulating hemostasis and thrombosis: Vessels, cells, and molecules in illustrated review

This illustrated review focuses on the physical forces that regulate hemostasis and thrombosis. These phenomena span from the vessel to the cellular to the molecular scales. Blood is a complex fluid with a viscosity that varies with how fast it flows and the size of the vessel through which it flows. Blood flow imposes forces on the vessel wall and blood cells that dictates the kinetics, structure, and stability of thrombi. The mechanical properties of blood cells create a segmented flowing fluid whereby red blood cells concentrate in the vessel core and platelets marginate to the near-wall region. At the vessel wall, shear stresses are highest, which requires a repertoire of receptors with different bond kinetics to roll, tether, adhere, and activate on inflamed endothelium and extracellular matrices. As a thrombus grows and then contracts, forces regulate platelet aggregation as well as von Willebrand factor function and fibrin mechanics. Forces can also originate from platelets as they respond to the external forces and sense the stiffness of their local environment.

Anemia-Induced Bleeding in Patients with Platelet Disorders

Anemia is not only a consequence of bleeding, but also a modifiable risk factor for bleeding in patients with thrombocytopenia or platelet function defects. In this review we outline the mechanism of anemia-induced bleeding in patients with platelet disorders, which involves a disturbance in normal red blood cell (RBC) rheology and reduced platelet margination to the endothelial surface due to a decrease in RBC mass, leading to impaired primary hemostasis and bleeding. Biologically, anemia reduces the mass of RBCs in the central column of flowing blood through a vessel resulting in fewer platelets coming into contact with the endothelial surface at the periphery of the flowing blood column. Thus, anemia results in impaired primary hemostasis. Von Willebrand factor (vWF) is another component of primary hemostasis and vWF deficiency, especially a deficiency of the highest vWF multimers, can also manifest with bleeding when concomitant anemia occurs. Clinically, patients at greatest risk for anemia-induced bleeding include patients with hematological malignancies in whom anemia and thrombocytopenia occur as a result of the underlying disease or the myelotoxic effects of treatment; patients with renal insufficiency with uremic thrombocytopathy and hypoproliferative anemia; and patients with inherited or acquired bleeding disorders affecting primary hemostasis (eg, Bernard-Soulier syndrome, von Willebrand disease) with chronic blood loss and iron deficiency anemia. Underlying abnormalities of any components of primary hemostasis plus concomitant anemia may result in major bleeding disorders; therefore, correction of remediable abnormalities-most notably, correction of the anemia- would be expected to have important clinical benefit. In this review we discuss how the correction of the anemia may lead to improvement of bleeding outcomes in patients with a primary hemostatic defect, supported by evidence from animal models, clinical trials and clinical experience.

Heterozygous mutation SLFN14 K208N in mice mediates species-specific differences in platelet and erythroid lineage commitment

Schlafen 14 (SLFN14) has recently been identified as an endoribonuclease responsible for cleaving RNA to regulate and inhibit protein synthesis. Early studies revealed that members of the SLFN family are capable of altering lineage commitment during T-cell differentiation by using cell-cycle arrest as a means of translational control by RNase activity. SLFN14 has been reported as a novel gene causing an inherited macrothrombocytopenia and bleeding in human patients; however, the role of this endoribonuclease in megakaryopoiesis and thrombopoiesis remains unknown. To investigate this, we report a CRISPR knock-in mouse model of SLFN14 K208N homologous to the K219N mutation observed in our previous patient studies. We used hematological analysis, in vitro and in vivo studies of platelet and erythrocyte function, and analysis of spleen and bone marrow progenitors. Mice homozygous for this mutation do not survive to weaning age, whereas heterozygotes exhibit microcytic erythrocytosis, hemolytic anemia, splenomegaly, and abnormal thrombus formation, as revealed by intravital microscopy, although platelet function and morphology remain unchanged. We also show that there are differences in erythroid progenitors in the spleens and bone marrow of these mice, indicative of an upregulation of erythropoiesis. This SLFN14 mutation presents distinct species-specific phenotypes, with a platelet defect reported in humans and a severe microcytic erythrocytosis in mice. Thus, we conclude that SLFN14 is a key regulator in mammalian hematopoiesis and a species-specific mediator of platelet and erythroid lineage commitment.

The role of bone marrow-derived cells in venous thromboembolism

Venous thrombosis is a life-threatening condition with high morbidity and mortality. Abnormal functioning of different cells in the blood is an integral part of its pathogenesis. In this review, we describe the contribution of bone marrow-derived cells to the development of this debilitating disease. We present both epidemiological and clinical data demonstrating involvement of various cell types in venous thrombosis, and discuss potential mechanisms underlying these effects. Modern concepts including recently discovered new paradigms in thrombosis, such as neutrophil extracellular traps, mast cells, and polyphosphate, are summarized.

Anabolic steroid excess and myocardial infarction: From ischemia to reperfusion injury

Anabolic steroids (AS) are synthetic testosterone-derivatives developed by the pharmaceutical industry to mimic testosterone biological effects. So far, AS have been implicated in the treatment of pathological conditions, such as hypogonadism, anemia, and cachexia. Since their discovery, though, AS have been illicitly used by elite and recreational athletes, bodybuilders and weightlifters in order to enhance athletic and aesthetic performance. This practice is characterized by cycles of administration and withdrawal, the combination of different AS compounds, and administration of doses 50 - 1000 times higher than those recommended for therapeutic purposes. AS excess has been correlated to cardiovascular detrimental effects, including cardiac hypertrophy, arrhythmias, and hypertension. Particularly, acute myocardial infarction (AMI) has been extensively reported by clinical and post-mortem studies. Atherosclerosis, hypercoagulability state, increased thrombogenesis and vasospasm have arisen as potential causes of myocardial ischemia in AS users. Additionally, several experimental reports have demonstrated that AS can increase the susceptibility to cardiac ischemia/reperfusion injury, whereas the cardioprotection elicited by physical exercise and ischemic postconditioning is blunted. Altogether, these factors can contribute to increased AMI morbidity and mortality during AS excess, particularly when AS are combined with other compounds, such as thyroid hormones, growth hormones, insulin, and diuretics.

Mean Corpuscular Volume Predicts Adverse Outcomes Following Peripheral Angioplasty With Stenting and Is Associated With On-Treatment Platelet Reactivity

Structural aspects of red blood cells have been associated with cardiovascular disease. No data linking mean corpuscular volume (MCV) to clinical outcomes and on-treatment platelet reactivity in patients with peripheral artery disease (PAD) are available. We investigated a composite of atherothrombotic events and target vessel restenosis or reocclusion following infrainguinal stenting for stable PAD. Residual platelet reactivity was measured by light transmission aggregometry (LTA) and the VerifyNow assays. We included 104 patients receiving dual antiplatelet therapy (DAPT) with aspirin and clopidogrel. In receiver-operating characteristic analysis, MCV effectively discriminated between patients with and without adverse outcomes and identified a MCV ≤90.8 fL as optimal cutoff. Adverse outcomes occurred significantly more often in patients with low MCV (log-rank P = .002). In univariable Cox regression analysis, low MCV was associated with an increased risk of future adverse outcomes (hazard ratio [HR]: 2.662 [95%CI: 1.304-5.434]; P = .007) and remained significantly associated after adjustment (HR: 2.591 [95%CI: 1.242-5.403]; P = .011). Mean corpuscular volume was inversely correlated with arachidonic acid (AA)- and adenosine diphosphate (ADP)-inducible platelet reactivity by LTA and with the VerifyNow aspirin assay. Low MCV is associated with adverse outcomes over 2 years following infrainguinal stenting. Mean corpuscular volume correlates inversely with AA- and ADP-inducible platelet reactivity during DAPT.

Abnormal platelet activity in dogs and cats - impact and measurement

Abnormal platelet activity can either lead to bleeding tendencies or inappropriate thrombus formation and can occur secondarily to a wide variety of disease processes, with a range of clinical consequences and severity. This article will discuss the pathophysiology of platelet function abnormalities and consider a logical diagnostic approach applicable to veterinary practice. Recent advances in platelet function testing will then be discussed, with regards to detection of platelet dysfunction and tailoring of pharmacological manipulation. Although many of these tests are still confined to research or academic institutions, techniques for indirectly assessing platelet function are starting to become more widely available. Although we still require further research to develop guidelines for the use of these tests in clinical decision-making, the recent advances in this field are an exciting step forward in being able to detect and manage platelet dysfunction in both primary care and referral practice.

Red Blood Cell Dysfunction in Critical Illness

Oxygen (O2) delivery, which is fundamental to supporting patients with critical illness, is a function of blood O2 content and flow. This article reviews red blood cell (RBC) physiology and dysfunction relevant to disordered O2 delivery in the critically ill. Flow is the focus of O2 delivery regulation: O2 content is relatively fixed, whereas flow fluctuates greatly. Thus, blood flow volume and distribution vary to maintain coupling between O2 delivery and demand. This article reviews conventional RBC physiology influencing O2 delivery and introduces a paradigm for O2 delivery homeostasis based on coordinated gas transport and vascular signaling by RBCs.

[Thrombosis and platelet dysfunction in myeloproliferative neoplasms]

Myeloproliferative neoplasms are acquired hematological malignancies, mainly affecting the adult and whose morbidity and mortality stems from haemostasis disorders. The most frequently encountered complications include thrombosis, affecting preferentially the arterial territory, but also atypical locations such as splanchnic vein thrombosis. The pathophysiology of these thromboses is complex and involves different actors: blood cells, endothelium and flow conditions. Numerous studies have been conducted to identify risk factors for thrombosis. To date, only two risk factors have been validated through prospective studies (age over 60 years old, history of thrombotic events) and allow classification of patients as "low risk" and "high risk" as the basis for current treatment recommendations. Haemorrhagic manifestations, less frequent than thrombosis, are mainly related to an alteration of primary haemostasis and are therefore manifested by mucocutaneous bleeding. In these patients, platelet dysfunctions and/or acquired Willebrand syndromes can be found. The pathophysiology of thrombosis and platelet dysfunction during myeloproliferative neoplasms remains to date partially unknown. In this review, we offer to focus on physiopathological mechanisms as well as the latest advances in their understanding.

Arterial and venous thrombosis by high platelet count and high hematocrit: 108 521 individuals from the Copenhagen General Population Study

BACKGROUND

It is unclear whether high platelet count or high hematocrit predict risk of thrombosis in individuals from the general population.

OBJECTIVES

We tested the hypothesis that individuals from the general population with high platelet count or high hematocrit have high risk of arterial and venous thrombosis.

METHODS

We prospectively followed 108 521 individuals from The Copenhagen General Population Study for a median of 8 years. Platelet count and blood hematocrit were measured at study entry.

RESULTS AND CONCLUSION

Multivariable adjusted hazard ratios for individuals with platelet counts in the top 5 percentiles (>398 × 109 /L) vs in the 25th-75th percentiles (231-316 × 109 /L) were 1.77 (95% confidence interval [CI], 1.38-2.24) for arterial thrombosis in the brain (38 and 26 events/10 000 person-years) and 0.82 (95%, 0.61-1.11) for arterial thrombosis in the heart (23 and 28 events/10 000 person-years). For individuals with hematocrit values in the top 5 percentiles (women/men: >45/>48%) vs the 25th-75th percentiles (women/men: 38.1-42/41.1-45%), hazard ratios were 1.27 (95% CI, 0.91-1.75) for arterial thrombosis in the brain (40 and 26 events/10 000 person-years) and 1.46 (95% CI, 1.06-2.00) for arterial thrombosis in the heart (43 and 25 events/10 000 person-years). Neither high platelet count nor high hematocrit was associated with risk of venous thromboembolism. When excluding individuals with myeloproliferative neoplasia from the main analyses, results on risk of thrombosis were similar. In this prospective study, high platelet counts were associated with 1.8-fold risk of arterial thrombosis in the brain, whereas high hematocrit was associated with 1.5-fold risk of arterial thrombosis in the heart.

Myeloproliferative Neoplasms: A Primer for Radiologists

The myeloproliferative neoplasms (MPNs) are a heterogeneous group of diseases including polycythemia vera, essential thrombocythemia, and primary myelofibrosis. Knowledge of the radiological and clinical features of MPNs and their associated complications is critical for interpreting radiologists. The purpose of this article is to provide a primer to radiologists summarizing the modern understanding of MPNs from an imaging-based perspective, including common disease-related findings and complications related to hematopoietic cell transplant.

Bleeding risk and complications associated with percutaneous ultrasound-guided liver biopsy in cats

OBJECTIVES

Liver biopsy is necessary for a diagnosis of liver disease; however, post-biopsy bleeding is a concern. The aim of this study was to describe the extent of bleeding and the occurrence of complications after percutaneous ultrasound-guided liver biopsy (PUGLB) in cats.

METHODS

The medical records of 30 cats that had a PUGLB were retrospectively reviewed. Using human guidelines, bleeding was classified as minor or major when the absolute change in packed cell volume (ΔPCV) was <0 and >-6% or ≤-6%, respectively. Complications were defined as physiologic compromise necessitating an intervention, or death. The relationship between ΔPCV and the occurrence of complications and the signalment, initial PCV, coagulation parameters, serum liver enzymes and bilirubin, number of biopsies, histological diagnosis, ultrasound findings, radiologist experience, concurrent procedures and vitamin K administration were assessed using Fisher's exact test, ANOVA and Pearson's correlation coefficient, with a P value <0.05 considered significant.

RESULTS

All cats had a decrease in PCV after biopsy. The mean ΔPCV was -6.9% ± 4.1%. Minor and major bleeding occurred in 13/30 (43.3%) and 17/30 (56.7%) cats, respectively, and non-lethal bleeding complications occurred in 5/30 (16.7%). Cats with complications had a lower pre-biopsy PCV ( P <0.003). Major bleeding was more likely with a diagnosis of hepatic lipidosis ( P = 0.03). There was no correlation between ΔPCV or complications and signalment, coagulation parameters, serum parameters, number of biopsies, ultrasound findings, radiologist experience, concurrent procedures and vitamin K administration.

CONCLUSIONS AND RELEVANCE

PUGLB is a relatively safe procedure in cats, although many cats have a subclinical decrease in PCV. As conventional coagulation tests did not predict complications or the magnitude of ΔPCV, there is a need for more sensitive indicators of bleeding risk in cats undergoing PUGLB.

Assessment of blood morphology, electrolyte level as well as kidney and liver function before and after leaving the water in a winter swimmers during the entire winter swimming season - a case study

Study aim: The aim of the study was to assess blood morphology, electrolyte level as well as indices of kidney function and the activity of selected liver enzymes determining liver function before and after exiting the water in a winter swimmer (“Walrus”) from the “Kaloryfer” (“Radiator”) Krakow Winter Swimming Club during the whole winter bathing season. Materials and methods: The subject of research was a winter swimmer from the “Radiator” Krakow Winter Swimming Club  a 53-year-old male. Blood was collected from the subject: at the beginning of the winter swimming season, during (five times) and at the end of the season (each time before and after getting out of the water); time maintaining in water: 10 minutes. Results: Analysing the average values of the indices before and after exiting the water, statistically significant increases were noted in AST [U/L] by 6.4% and LDH [U/L] by 2.45%, as well as a decrease in Na+ [mmol/l] by 1.14%, Clˉ [mmol/l] by 1.78% and urea [mmol/l] by 3.64%. Conclusions: Regular baths taken by the winter swimmers in cold water did not affect blood morphology indices and did not cause pathological changes in kidney profile. Furthermore, slight fluctuations regarding the concentration of electrolytes in the blood serum and changes in the hepatic profile additionally “externalised” health problems, which appeared prior to winter swimming.

ACVIM consensus statement on the diagnosis and treatment of chronic hepatitis in dogs

This consensus statement on chronic hepatitis (CH) in dogs is based on the expert opinion of 7 specialists with extensive experience in diagnosing, treating, and conducting clinical research in hepatology in dogs. It was generated from expert opinion and information gathered from searching of PubMed for manuscripts on CH, the Veterinary Information Network for abstracts and conference proceeding from annual meetings of the American College of Veterinary Medicine and the European College of Veterinary Medicine, and selected manuscripts from the human literature on CH. The panel recognizes that the diagnosis and treatment of CH in the dog is a complex process that requires integration of clinical presentation with clinical pathology, diagnostic imaging, and hepatic biopsy. Essential to this process is an index of suspicion for CH, knowledge of how to best collect tissue samples, access to a pathologist with experience in assessing hepatic histopathology, knowledge of reasonable medical interventions, and a strategy for monitoring treatment response and complications.

Fluid resuscitation during persistent postpartum haemorrhage and maternal outcome: A nationwide cohort study

OBJECTIVE

To determine the association between increasing volumes of crystalloids and colloids administered before transfusion of packed red blood cells in women with persistent postpartum haemorrhage and adverse maternal outcomes.

STUDY DESIGN

Retrospective cohort study in the Netherlands. Women with persistent postpartum haemorrhage and known clear fluids volume for resuscitation were included. Women who received ≤2 L of clear fluids were the reference group. We determined the effect of every additional litre of clear fluids on total blood loss, severe maternal morbidity and mortality. Results were adjusted for patient and bleeding characteristics.

RESULTS

Of the 883 included women, 199 received ≤2 L of clear fluids. Median blood loss for the reference group was 2.9 L (interquartile range 2.2-3.4). Adjusted mean difference in blood loss compared with the reference group was 0.2 L (95% confidence interval -0.1 to 0.5) for women in the >2 to ≤3 L, 0.4 L (0.1-0.7) for the >3 to ≤4 L category, 0.6 L (0.5-0.7) for the >4 to ≤5 L category, and 1.9 L (1.5-2.3) for the >5 to ≤7 L category. Adjusted odds ratios for adverse maternal outcomes were 1.0 (0.7-1.6), 1.2 (0.8-1.9), 1.8 (1.1-3.1) and 4.4 (2.6-7.5) for women in the 2 to ≤3 L category, >3 to ≤4 L, >4 to ≤5 L, and >5 to ≤7 L volume categories respectively. Results were similar in strata of different severities of bleeding.

CONCLUSION

Clear fluids volume >4 L was independently associated with adverse maternal outcome in women with persistent postpartum haemorrhage.

Platelet function, coagulation and fibrinolysis in patients with previous coronary and cerebrovascular ischemic events

OBJECTIVES

Ischemic stroke (IS) or transient ischemic attack (TIA) history is present in 4-17% of patients with coronary artery disease (CAD). This subgroup of patients is at high risk for both ischemic and bleeding events. The aim of this study was to determine the role of platelet aggregability, coagulation and endogenous fibrinolysis in patients with CAD and previous IS or TIA.

METHODS

A prospective case-control study that included 140 stable CAD patients divided into two groups: the CASE group (those with a previous IS/TIA, n=70) and the CONTROL group (those without a previous IS/TIA, n=70). Platelet aggregability (VerifyNow Aspirin® and VerifyNow P2Y12®), coagulation (fibrinogen and thromboelastography by Reorox®) and endogenous fibrinolysis (D dimer and plasminogen activator inhibitor-1) were evaluated.

RESULTS

Patients in the CASE group presented significantly higher systolic blood pressure levels (135.84±16.09 vs 123.68±16.11, p<0.01), significantly more previous CABG (25.71% vs 10%, p=0.015) and significantly higher calcium channel blocker usage (42.86% vs 24.29%, p=0.02) than those in the control group. In the adjusted models, low triglyceride values, low hemoglobin values and higher systolic blood pressure were significantly associated with previous IS/TIA (CASE group). Most importantly, platelet aggregability, coagulation and fibrinolysis tests were not independently associated with previous cerebrovascular ischemic events (CASE group).

CONCLUSION

Platelet aggregability, coagulation and endogenous fibrinolysis showed similar results among CAD patients with and without previous IS/TIA. Therefore, it remains necessary to identify other targets to explain the higher bleeding risk presented by these patients.

Association Between Changes in Hemoglobin Concentration and Cardiovascular Risks and All-Cause Mortality Among Young Women

Background Anemia is considered to increase the risk of mortality in high-risk populations, but its effect has not been examined among young populations. This study aimed to determine the effect of hemoglobin (Hb) concentration and its changes on the risk of acute myocardial infarction ( AMI ), stroke, cerebrovascular disease and all-cause mortality among young women. Methods and Results We analyzed data from the Korean National Health Information Database on 808 143 women aged 20 to 39 years without any cardiocerebrovascular disease. A 1-time Hb concentration and changes in Hb over a 2-year period were calculated as exposures. Participants were followed for a median of 10 years to determine the risk of AMI , stroke, cerebrovascular disease, and all-cause mortality. There were U- or J-shaped associations between Hb concentration or change in Hb and AMI , stroke, cerebrovascular disease, and all-cause mortality. Increasing the Hb concentration from normal to high increased the risk for AMI (hazard ratio [95% confidence interval]: 1.49 [1.08-2.04]). With regard to the risk for stroke, increasing the Hb concentration from a normal to a high range increased the risk (hazard ratio [95% confidence interval]: 1.10 [1.02-1.35]), and decreasing the Hb concentration from a high to a normal range decreased this risk (hazard ratio [95% confidence interval]: 0.80 [0.60-0.97]). Improving anemia to the normal Hb range decreased all-cause mortality (hazard ratio [95% confidence interval]: 0.81 [0.69-0.94]); however, overcorrection of Hb concentration (Hb≥14.0 g/dL) was not significant. Conclusions These findings suggest that regular Hb analysis may assist in identifying young women who are at risk of AMI , stroke, cerebrovascular disease, and all-cause mortality.

Platelet-RBC interaction mediated by FasL/FasR induces procoagulant activity important for thrombosis

Red blood cells (RBCs) influence rheology, and release ADP, ATP, and nitric oxide, suggesting a role for RBCs in hemostasis and thrombosis. Here, we provide evidence for a significant contribution of RBCs to thrombus formation. Anemic mice showed enhanced occlusion times upon injury of the carotid artery. A small population of RBCs was located to platelet thrombi and enhanced platelet activation by a direct cell contact via the FasL/FasR (CD95) pathway known to induce apoptosis. Activation of platelets in the presence of RBCs led to platelet FasL exposure that activated FasR on RBCs responsible for externalization of phosphatidylserine (PS) on the RBC membrane. Inhibition or genetic deletion of either FasL or FasR resulted in reduced PS exposure of RBCs and platelets, decreased thrombin generation, and reduced thrombus formation in vitro and protection against arterial thrombosis in vivo. Direct cell contacts between platelets and RBCs via FasL/FasR were shown after ligation of the inferior vena cava (IVC) and in surgical specimens of patients after thrombectomy. In a flow restriction model of the IVC, reduced thrombus formation was observed in FasL-/- mice. Taken together, our data reveal a significant contribution of RBCs to thrombosis by the FasL/FasR pathway.

Inhibition of prolyl hydroxylase domain proteins selectively enhances venous thrombus neovascularisation

BACKGROUND

Hypoxia within acute venous thrombi is thought to drive resolution through stabilisation of hypoxia inducible factor 1 alpha (HIF1α). Prolyl hydroxylase domain (PHD) isoforms are critical regulators of HIF1α stability. Non-selective inhibition of PHD isoforms with l-mimosine has been shown to increase HIF1α stabilisation and promote thrombus resolution.

OBJECTIVE

The aim of this study was to investigate the therapeutic potential of PHD inhibition in venous thrombus resolution.

METHODS

Thrombosis was induced in the inferior vena cava of mice using a combination of flow restriction and endothelial activation. Gene and protein expression of PHD isoforms in the resolving thrombus was measured by RT-PCR and immunohistochemistry. Thrombus resolution was quantified in mice treated with pan PHD inhibitors AKB-4924 and JNJ-42041935 or inducible all-cell Phd2 knockouts by micro-computed tomography, 3D high frequency ultrasound or endpoint histology.

RESULTS

Resolving venous thrombi demonstrated significant temporal gene expression profiles for PHD2 and PHD3 (P < 0.05), but not for PHD1. PHD isoform protein expression was localised to early and late inflammatory cell infiltrates. Treatment with selective pan PHD inhibitors, AKB-4924 and JNJ-42041935, enhanced thrombus neovascularisation (P < 0.05), but had no significant effect on overall thrombus resolution. Thrombus resolution or its markers, macrophage accumulation and neovascularisation, did not differ significantly in inducible all-cell homozygous Phd2 knockouts compared with littermate controls (P > 0.05).

CONCLUSIONS

This data suggests that PHD-mediated thrombus neovascularisation has a limited role in the resolution of venous thrombi. Directly targeting angiogenesis alone may not be a viable therapeutic strategy to enhance venous thrombus resolution.

Management of postpartum hemorrhage: how to improve maternal outcomes?

Postpartum hemorrhage is the leading cause of maternal mortality and severe morbidity. Despite efforts to improve maternal outcomes, management of postpartum hemorrhage still faces at least four challenges, discussed in this review. First, current definitions for severe postpartum hemorrhage hamper early identification of women with a high risk of adverse outcomes. Adaptations to the definitions and the use of clinical tools such as shock index and early warning systems may facilitate this early identification. Second, surgical and radiological interventions to prevent hysterectomy are not always successful. More knowledge on the influence of patient and bleeding characteristics on the success rates of these interventions is necessary. Scarce data suggest that early timing of intrauterine balloon tamponade may improve maternal outcomes, whereas early timing of arterial embolization seems to be unrelated to maternal outcomes. Third, fluid resuscitation with crystalloids and colloids is unavoidable in the early phases of postpartum hemorrhage but may result in dilutional coagulopathy. Effects of different volumes of clear fluids on the occurrence of dilutional coagulopathy and maternal outcomes is unknown. Fourth, a better understanding of diagnosis and correction of coagulopathy during postpartum hemorrhage is needed. Low plasma fibrinogen levels at the start of postpartum hemorrhage predict progression to severe hemorrhage, but standard coagulation screens are time consuming. A solution may be point-of-care coagulation testing; however, clinical usefulness during postpartum hemorrhage has not been demonstrated. To date, early administration of tranexamic acid is the only hemostatic intervention that was proven to improve outcomes in women with postpartum hemorrhage.

Phosphatidylserine-exposing blood and endothelial cells contribute to the hypercoagulable state in essential thrombocythemia patients

The mechanisms of thrombogenicity in essential thrombocythemia (ET) are complex and not well defined. Our objective was to explore whether phosphatidylserine (PS) exposure on blood cells and endothelial cells (ECs) can account for the increased thrombosis and distinct thrombotic risks among mutational subtypes in ET. Using flow cytometry and confocal microscopy, we found that the levels of PS-exposing erythrocytes, platelets, leukocytes, and serum-cultured ECs were significantly higher in each ET group [JAK2, CALR, and triple-negative (TN) (all P < 0.001)] than those in controls. Among ET patients, those with JAK2 mutations showed higher levels of PS-positive erythrocytes, platelets, neutrophils, and serum-cultured ECs than TN patients or those with CALR mutations, which show similar levels. Coagulation function assays showed that higher levels of PS-positive blood cells and serum-cultured ECs led to markedly shortened coagulation time and dramatically increased levels of FXa, thrombin, and fibrin production. This procoagulant activity could be largely blocked by addition of lactadherin (approx. 70% inhibition). Confocal microscopy showed that the FVa/FXa complex and fibrin fibrils colocalized with PS on ET serum-cultured ECs. Additionally, we found a relationship between D-dimer, prothrombin fragment F1 + 2, and PS exposure. Our study reveals a previously unrecognized link between hypercoagulability and exposed PS on cells, which might also be associated with distinct thrombotic risks among mutational subtypes in ET. Thus, blocking PS-binding sites may represent a new therapeutic target for preventing thrombosis in ET.

Hematocrit Values Predict Carotid Intimal-Media Thickness in Obese Patients With Non-Alcoholic Fatty Liver Disease: A Cross-Sectional Study

BACKGROUND

Literature data suggest with some criticism that full-fledged cardiovascular (CV) events (acute or chronic) are likely predicted by blood components, which are reported to be associated with the presence/severity of non-alcoholic fatty liver disease (NAFLD). This study was aimed at determining which marker(s) derived from blood count, such as white blood cells, neutrophils, neutrophil/lymphocyte ratio, platelet count, hemoglobin, mean corpuscular volume, hematocrit values were associated with ear or subclinical atherosclerosis, in obese patients of various classes suffering from NAFLD.

METHODS

One hundred consecutive obese patients presenting NAFLD at ultrasound, with low prevalence of co-morbidities and no history or instrumental features of CV diseases, underwent carotid intima-media thickness (IMT) assessment by Doppler ultrasonography. All of them were studied taking into account anthropometric parameters, the metabolic profile, and inflammatory markers.

RESULTS

White blood cells and neutrophil count showed no statistical association with IMT, which was predicted by the amount of visceral adiposity, as appreciated by ultrasonography. After adjusting for visceral adiposity and smoking status, only age and hematocrit contextually predicted early atherosclerosis, evaluated as IMT. Visceral adiposity was a confounding factor in foreseeing IMT.

CONCLUSION

Hematocrit values along with the patient's age suggest an initial atherosclerosis, evaluated as IMT, and if this finding is confirmed in larger cohorts, could be added to other canonical CV risk factors. Inferences can be enhanced by future prospective studies that aim to identify the relationships between incident cardio-metabolic cases and this hematologic parameter.

Platelets from flowing blood attach to the inflammatory chemokine CXCL16 expressed in the endothelium of the human vessel wall

Endothelial chemokine CXC motif ligand 16 (CXCL16) expression is associated with atherosclerosis, while platelets, particularly those attaching to atherosclerotic plaque, contribute to all stages of athero-sclerotic disease. This investigation was designed to examine the role of CXCL16 in capturing platelets from flowing blood. CXCL16 was expressed in human atherosclerotic plaques, and lesion severity in human carotid endarterectomy specimens was positively correlated with CXCL16 levels. CXCL16 expression in plaques was co-localised with platelets deposited to the endothelium. Immobilised CXCL16 promoted CXCR6-dependent platelet adhesion to the human vessel wall, endothelial cells and von Willebrand factor during physiologic flow. At low shear, immobilised CXCL16 captured platelets from flowing blood. It also induced irreversible platelet aggregation and a rise in intra-platelet calcium levels. These results demonstrate that endothelial CXCL16’s action on platelets is not only limited to platelet activation, but that immobilised CXCL16 also acts as a potent novel platelet adhesion ligand, inducing platelet adhesion to the human vessel wall.

A comparative study of prothrombin complex concentrates and freshfrozen plasma for warfarin reversal under static and flow conditions

Prothrombin complex concentrates (PCCs) and fresh-frozen plasma (FFP) have been clinically used for acute warfarin reversal. The recovery of prothrombin time (PT) or international normalised ratio (INR) is often reported as an endpoint, but haemostatic efficacies of PCCs and FFP may not be fully reflected in static clotting test in platelet-poor plasma. Using various in vitro assays, we compared the effects of two PCC preparations (3-factor PCC; Bebulin and 4-factor PCC; Beriplex) and FFP on warfarin reversal under static and flow conditions. First, we added an aliquot of either PCC (0.3 or 0.72 U/ml) or 20% FFP (v/v) to commercial warfarin plasma (INR 3.2, or 10.3), and then measured PT, factor II, factor VII, and thrombin generation. Subsequently, we collected whole blood samples from six consented warfarin-treated patients with mean INR 3.0 ± 0.5 (range 2.5–3.7), and compared clot formation under flow conditions at 280 s-1 before and after addition of either PCC preparation (0.3 and 0.6 U/ml) or 20% of FFP (v/v). PT/INR were restored by either PCC in plasma with INR 3.0, but they were more effectively corrected by 4-factor PCC than 3-factor PCC in plasma with INR 10.3. Effects of FFP were similar to 0.3U/ml of PCCs in terms of PT, but FFP was less efficacious than PCCs in recovering thrombin generation or factor II levels. In flow experiments, the onset of thrombus formation was shortened by either PCC, but not by FFP, contrary to shortened PT values. For warfarin reversal 20% volume replacement with FFP is inferior to PCCs.

The Extracranial Consequences of Subarachnoid Hemorrhage

BACKGROUND

Subarachnoid hemorrhage (SAH) is managed across the full spectrum of healthcare, from clinical diagnosis to management of the hemorrhage and associated complications. Knowledge of the pathogenesis and pathophysiology of SAH is widely known; however, a full understanding of the underlying molecular, cellular, and circulatory dynamics has still to be achieved. Intracranial complications including delayed ischemic neurologic deficit (vasospasm), rebleed, and hydrocephalus form the targets for initial management. However, the extracranial consequences including hypertension, hyponatremia, and cardiopulmonary abnormalities can frequently arise during the management phase and have shown to directly affect clinical outcome. This review will provide an update on the pathophysiology of SAH, including the intra- and extracranial consequences, with a particular focus on the extracranial consequences of SAH.

METHODS

We review the literature and provide a comprehensive update on the extracranial consequences of SAH that we hope will help the management of these cohort of patients.

RESULTS

In addition to the pathophysiology of SAH, the following complications were examined and discussed: vasospasm, seizures, rebleed, hydrocephalus, fever, anemia, hypertension, hypotension, hyperglycemia, hyponatremia, hypernatremia, cardiac abnormalities, pulmonary edema, venous thromboembolism, gastric ulceration, nosocomial infection, bloodstream infection/sepsis, and iatrogenic complications.

CONCLUSIONS

Although the intracranial complications of SAH can take priority in the initial management, the extracranial complications should be monitored for and recognized as early as possible because these complications can develop at varying times throughout the course of the condition. Therefore, a variety of investigations, as described by this article, should be undertaken on admission to maximize early recognition of any of the extracranial consequences. Furthermore, because the extracranial complications have a direct effect on clinical outcome and can lead to and exacerbate the intracranial complications, monitoring, recognizing, and managing these complications in parallel with the intracranial complications is important and would allow optimization of the patient's management and thus help improve their overall outcome.

Anesthetic Management of Pediatric Liver and Kidney Transplantation

Pediatric patients with liver dysfunction and renal failure may exhibit many comorbidities. There are often associated congenital syndromes to be taken into account. Liver and renal transplantation offer a solution and substantial improvement in quality of life. Anesthetic management of pediatric liver and renal transplantation has not been well described. There are key differences between adults and children undergoing these procedures, and acknowledgment of some key principles provide a solid foundation to optimize perioperative outcomes. This article provides an overview of the perioperative management and considerations in pediatric patients undergoing liver and renal transplantation.

Red blood cells in thrombosis

Red blood cells (RBCs) have historically been considered passive bystanders in thrombosis. However, clinical and epidemiological studies have associated quantitative and qualitative abnormalities in RBCs, including altered hematocrit, sickle cell disease, thalassemia, hemolytic anemias, and malaria, with both arterial and venous thrombosis. A growing body of mechanistic studies suggests that RBCs can promote thrombus formation and enhance thrombus stability. These findings suggest that RBCs may contribute to thrombosis pathophysiology and reveal potential strategies for therapeutically targeting RBCs to reduce thrombosis.

Role of red blood cells in the anemia-associated bleeding under high shear conditions

BACKGROUND

Red blood cells (RBCs) contribute to hemostasis under blood-flow, and anemia might contribute to a hemorrhagic diathesis. The majority of current laboratory techniques to assess hemostasis do not consider the effects of RBCs. An assay to determine the role of RBCs in hemostasis could be beneficial for clinical management.

OBJECTIVES

To investigate the influence of RBCs in hemostasis.

METHODS

Hemostasis was investigated using a novel microchip flow-chamber system (T-TAS^® ) in an anemic patient with von Willebrand disease. Subsequently, the effects of RBCs in total thrombus analysis system (T-TAS) were examined using reconstituted whole blood at various hematocrit levels.

RESULTS

In vivo: When the patient was anemic and demonstrated persisted hemorrhagic symptoms despite the maintained adequate von Willebrand factor ristocetin cofactor activity levels, thrombus formation determined by T-TAS was delayed. However, transfusions of RBCs resolved bleeding symptom and, accordingly, the thrombus formation in T-TAS improved. In vitro: Thrombus formation determined by T-TAS at 1000 s^-1 was dose-dependent on hematocrit (the time to reach 10 kPa (T₁₀ ): 10.0 ± 0, 9.5 ± 1.4, 6.7 ± 2.4, 2.8 ± 1.6 min at hematocrits of 0%, 12.5%, 25% and 50%, respectively). Markedly defective thrombus formation (T₁₀ >10 min) was confirmed at a hematocrit <25% at 2000 s^-1 .

CONCLUSION

Red blood cells play an essential role in hemostasis under high shear, and RBC transfusions could be effective for refractory bleeding in patients with anemia. T-TAS measurements appear to reflect the hemostatic consequences of diminished red cell numbers under blood-flow, and could provide a valuable means for monitoring patients.

Effect of restrictive versus liberal red cell transfusion strategies on haemostasis: systematic review and meta-analysis

Red cells play a key role in normal haemostasis in vitro but their importance clinically is less clear. The objective of this meta-analysis was to assess if correction of anaemia by transfusing red cells at a high haemoglobin threshold (liberal transfusion) is superior to transfusion at a lower haemoglobin threshold (restrictive transfusion) for reducing the risk of bleeding or thrombotic events. We searched for randomised controlled trials in any clinical setting that compared two red cell transfusion thresholds and investigated the risk of bleeding. We searched for studies published up to October 19, 2016 in The Cochrane Central Register of Controlled Trials, MEDLINE, PubMed, Embase, and the Transfusion Evidence Library and ISI Web of Science. Relative risks (RR) or Peto Odds Ratios (pOR) were pooled using a random-effect model. Nineteen randomised trials with 9852 participants were eligible for inclusion in this review. Overall there was no difference in the risk of any bleeding between transfusion strategies (RR 0.91, 95 % confidence interval [CI] 0.74 to 1.12). The risk of severe or life-threatening bleeding was lower with a restrictive strategy (RR 0.75, 95 % CI 0.57 to 0.99). There was no difference in the risk of thrombotic events (RR 0.83, 95 % CI 0.61 to 1.13). The risk of any bleeding was not reduced with liberal transfusion and there was no overall difference in the risk of thrombotic events. Data from the included trials do not support aiming for a high haemoglobin threshold to improve haemostasis. PROSPERO registration number CRD42016035519.

Elevated hematocrit enhances platelet accumulation following vascular injury

Red blood cells (RBCs) demonstrate procoagulant properties in vitro, and elevated hematocrit is associated with reduced bleeding and increased thrombosis risk in humans. These observations suggest RBCs contribute to thrombus formation. However, effects of RBCs on thrombosis are difficult to assess because humans and mice with elevated hematocrit typically have coexisting pathologies. Using an experimental model of elevated hematocrit in healthy mice, we measured effects of hematocrit in 2 in vivo clot formation models. We also assessed thrombin generation, platelet-thrombus interactions, and platelet accumulation in thrombi ex vivo, in vitro, and in silico. Compared with controls, mice with elevated hematocrit (RBC^HIGH) formed thrombi at a faster rate and had a shortened vessel occlusion time. Thrombi in control and RBC^HIGH mice did not differ in size or fibrin content, and there was no difference in levels of circulating thrombin-antithrombin complexes. In vitro, increasing the hematocrit increased thrombin generation in the absence of platelets; however, this effect was reduced in the presence of platelets. In silico, direct numerical simulations of whole blood predicted elevated hematocrit increases the frequency and duration of interactions between platelets and a thrombus. When human whole blood was perfused over collagen at arterial shear rates, elevating the hematocrit increased the rate of platelet deposition and thrombus growth. These data suggest RBCs promote arterial thrombosis by enhancing platelet accumulation at the site of vessel injury. Maintaining a normal hematocrit may reduce arterial thrombosis risk in humans.

Multi-Constituent Simulation of Thrombus Deposition

In this paper, we present a spatio-temporal mathematical model for simulating the formation and growth of a thrombus. Blood is treated as a multi-constituent mixture comprised of a linear fluid phase and a thrombus (solid) phase. The transport and reactions of 10 chemical and biological species are incorporated using a system of coupled convection-reaction-diffusion (CRD) equations to represent three processes in thrombus formation: initiation, propagation and stabilization. Computational fluid dynamic (CFD) simulations using the libraries of OpenFOAM were performed for two illustrative benchmark problems: in vivo thrombus growth in an injured blood vessel and in vitro thrombus deposition in micro-channels (1.5 mm × 1.6 mm × 0.1 mm) with small crevices (125 μm × 75 μm and 125 μm × 137 μm). For both problems, the simulated thrombus deposition agreed very well with experimental observations, both spatially and temporally. Based on the success with these two benchmark problems, which have very different flow conditions and biological environments, we believe that the current model will provide useful insight into the genesis of thrombosis in blood-wetted devices, and provide a tool for the design of less thrombogenic devices.

Role of red blood cells in haemostasis and thrombosis

In contrast to an obsolete notion that erythrocytes, or red blood cells (RBCs), play a passive and minor role in hemostasis and thrombosis, over the past decades there has been increasing evidence that RBCs have biologically and clinically important functions in blood clotting and its disorders. This review summarizes the main mechanisms that underlie the involvement of RBCs in hemostasis and thrombosis in vivo, such as rheological effects on blood viscosity and platelet margination, aggregation and deformability of RBCs; direct adhesion and indirect biochemical interactions with endothelial cells and platelets, etc. The ability of stored and pathologically altered RBCs to generate thrombin through exposure of phosphatidylserine has been emphasized. The procoagulant and prothrombotic potential of RBC-derived microparticles transfused with stored RBCs or formed in various pathological conditions associated with hemolysis has been described along with prothrombotic effects of free hemoglobin and heme. Binding of fibrinogen or fibrin to RBCs may influence their effects on fibrin network structure, clot mechanical properties, and fibrinolytic resistance. Recent data on platelet-driven clot contraction show that RBCs compressed by platelets pulling on fibrin form a tightly packed array of polyhedral erythrocytes, or polyhedrocytes, which comprises a nearly impermeable barrier important for hemostasis and wound healing. RBCs may perform dual roles, both helping to stem bleeding but at the same time contributing to thrombosis in a variety of ways.