New perspectives on the thrombotic complications of haemolysis

Magnetic particles with polymeric shells bearing lithocholic and folic acid moieties: Nano-warriors to fight colon cancer

In the study, we aimed to investigate the activity of nanoformulations containing 5-fluorouracil and polymer-magnetic hybrids bearing membrane-penetrating and ligand-receptor-recognizing agents against colorectal cancer cells. The formation and characterization of iron oxide particles covered with polymeric shells comprising lithocholic acid and folic acid moieties are presented. The efficiency of nanoformulations combined by the simple mixing of low doses of 5-fluorouracil with the obtained hybrids was demonstrated against DLD-1 and HT-29 colon cancer cells. The most pronounced cytotoxic potential against HT-29 cells was observed in the cases of particles based on block and randomly arranged copolymers functionalized by FA motifs with depletion of viable cells by approximately 50 % compared to control cells and cells treated by 5-FU applied in free form. In the case of the DLD-1 cell line, the percentage of viable DLD-1 cells decreased by about 30 to 40% after treatment with the block and randomly arranged copolymer decorated by FA-moiety, when compared to 5-FU at the free form and the untreated control. The induction of apoptosis associated with PS-translocation was determined to be the main mechanism of their cytotoxic effects. Moreover, the safety profiles of the nanoformulations were established through hemolysis assay and the analysis of the viability of human colorectal fibroblasts. It was indicated that all tested nanoparticles met the compatibility requirements at the in vitro level. It should be emphasized that in many cases, there was a significant improvement in the compatibility of hybrids with the FA motif compared to non-functionalized hybrids with the addition of 5-FU. These findings suggest that the presence of FA might modulate the toxicity of chemotherapeutic agents.

Organizing Pneumonia in a Case of Cold Agglutinin Disease with Pulmonary Thrombosis

Cold agglutinin disease is a subtype of autoimmune hemolytic anemia that occurs via the activation of specific anti-red blood cell antibodies (agglutinins) at low temperatures. Autoimmune hemolytic anemia has been reported to cause interstitial pneumonia; however, the underlying mechanism remains unclear. We herein report a 46-year-old man diagnosed with cold agglutinin disease complicated by pulmonary thrombosis and organizing pneumonia. Treatment with prednisolone improved the course of cold agglutinin disease and organizing pneumonia in a similar manner. To our knowledge, this is the first report of cold agglutinin associated with organizing pneumonia, suggesting a potential link between the two.

Management of Venous and Arterial Thrombosis

A thrombus is a hemostatic plug localized in a blood vessel [...].

Multiquery Similarity Searching Models: An Alternative Approach for Predicting Hemolytic Activity from Peptide Sequence

The desirable pharmacological properties and a broad number of therapeutic activities have made peptides promising drugs over small organic molecules and antibody drugs. Nevertheless, toxic effects, such as hemolysis, have hampered the development of such promising drugs. Hence, a reliable computational tool to predict peptide hemolytic toxicity is enormously useful before synthesis and experimental evaluation. Currently, four web servers that predict hemolytic activity using machine learning (ML) algorithms are available; however, they exhibit some limitations, such as the need for a reliable negative set and limited application domain. Hence, we developed a robust model based on a novel theoretical approach that combines network science and a multiquery similarity searching (MQSS) method. A total of 1152 initial models were constructed from 144 scaffolds generated in a previous report. These were evaluated on external data sets, and the best models were fused and improved. Our best MQSS model I1 outperformed all state-of-the-art ML-based models and was used to characterize the prevalence of hemolytic toxicity on therapeutic peptides. Based on our model's estimation, the number of hemolytic peptides might be 3.9-fold higher than the reported.

Hemolytic Anemia as a Provoking Factor for Recurrent Venous Thromboembolism: A Case Report

Warm antibody autoimmune hemolytic anemia (WAIHA) is a rare disease that leads to the destruction of red blood cells in the reticuloendothelial system through the mediation of agglutinins (immunoglobulin G (IgG) type in most cases) that attach to the erythrocyte wall at 37 °C. The association of WAIHA and venous thromboembolism (VTE) seems to be higher than other hemolytic disorders classically associated with VTE and there is a current investigation aimed at clarifying this association and establishing some criteria to use anticoagulant treatment in patients with WAIHA. Despite this, WAIHA is a rare cause for the development of recurrent VTE under secondary prophylactic anticoagulant treatment, with only a few cases described in the literature. We present the case of a patient who developed a recurrence of deep vein thrombosis during a WAIHA episode despite treatment with acenocoumarol and a review of the literature.

Effect of the apron in the mechanical characterisation of hyperelastic materials by means of biaxial testing: A new method to improve accuracy

Biological soft tissues and polymers used in biomedical applications (e.g. in the cardiovascular area) are hyperelastic incompressible materials that commonly operate under multi-axial large deformation fields. Their characterisation requires biaxial tensile testing. Due to the typically small sample size, the gripping of the specimens commonly relies on rakes or sutures, where the specimen is punctured at the edges of the gauge area. This approach necessitates of an apron, excess of material around the gauge region. This work analyses the apron influence on the estimated mechanical response of biaxial tests performed by using a rakes gripping system, with the aim of verifying the test accuracy and propose improved solutions. In order to isolate the effect of the apron, avoiding the influence of anisotropy and inhomogeneity typical of most soft tissues, homogeneous and isotropic hyperplastic samples made from a uniform sheet of casted silicone were tested. The stress-strain response of specimens with different apron sizes/shapes was measured experimentally by means of biaxial testing and digital image correlation. Tests were replicated numerically, to interpret the experimental findings. The apron surrounding the gauge area acts as an additional annular constraint which stiffens the system, resulting in a significant overestimate in the stress values. This error can be avoided by introducing specific cuts in the apron. The study quantifies, for the first time, the correlation between the apron size/shape and the experimental stress overestimation, proposing a research protocol which, although identified on homogeneous hyperelastic materials, can be useful in providing more accurate characterisation of both, synthetic polymers and soft tissues.

Elevated Hemolysis Index is associated with higher risk of cardiovascular diseases

OBJECTIVES

In vivo hemolysis is associated with thromboembolism. Although an increased Hemolysis Index (HI) can be due to in vitro as well as in vivo hemolysis, both reflects a more fragile erythrocyte population. We therefore hypothesized that HI above upper reference limit would be associated with an increased risk of cardiovascular disease (CVD).

METHODS

We identified persons with two elevated HI (HI+) from blood samples analyzed at a university hospital laboratory from 2012 to 2017. We compared their risk of CVD with the risk in matched comparators with normal HI and from the general population. HI+ persons and comparators were followed from start date (date of the second elevated HI) until the first of the main outcome: CVD, emigration, death, or end of observation time on December 31, 2018.

RESULTS

In 43,102 unique HI+ persons, the risk of developing CVD was 40% higher compared with the general population and 13% higher compared with the matched blood sample cohort. HI+ was associated with a significantly increased cumulative incidence of both arterial and venous CVD compared with the matched blood sample cohort and the general population (respectively 47 and 14% for arterial CVD; 78 and 24% for venous CVD). Moreover, overall mortality risk was significantly higher in patients with HI+ than in the two comparator groups.

CONCLUSIONS

Elevated HI is associated with increased risk of arterial and venous CVD and with increased mortality. Our findings imply that HI may contribute as a CVD risk biomarker.

Clinical and laboratory characteristics of patients with cold agglutinin disease: A retrospective analysis at a tertiary medical center

BACKGROUND

Cold agglutinin disease (CAD) is relatively rare and has primarily been reported as retrospective case series.

AIM

We reviewed our experience with CAD to shed light on this disease.

STUDY SETTINGS AND DESIGN

This was a retrospective review of all patients with CAD managed at our institution between 2007 and 2018.

MATERIALS AND METHODS

The study was approved by our institutional review board. We extracted patients' demographic, clinical, and laboratory data, blood transfusions, and outcomes from their electronic medical records.

STATISTICAL ANALYSIS USED

Statistical analysis was performed using SPSS version 17. The method of Kaplan-Meier was used to plot survival curves.

RESULTS

Forty-eight patients fulfilled the inclusion criteria for CAD. The median age of patients was 73.1 (range, 43-99) years; 36 (75%) were female. The majority (n = 38; 79.2%) of patients were Caucasians. Most patients (n = 25, 52.1%) presented with symptomatic anemia. Eight patients were asymptomatic. The median hemoglobin level was 8.6 g/dL (range, 3-12 g/dL); 7 (14.6%) patients had concurrent thrombocytopenia. Lactate dehydrogenase was elevated in 40/47 (85.1%) patients and haptoglobin was below normal in 35/46 (76.1%) patients. Coagulopathy was observed in 19 (52.8%) of 36 patients. Sixteen (33.3%) patients required blood transfusion during admission at the time of diagnosis with a median number of 3.5 red blood cell units. Twenty-five (52.1%) patients were alive after a median follow-up of 50.1 months. The 5-year and 10-year survival was estimated at 58.2% and 30.8%, respectively.

CONCLUSION

CAD poses considerable burden on patients and health-care systems. Patients vary widely in their disease severity and course.

G6PD deficiency-does it alter the course of COVID-19 infections?

Despite the existence of well-founded data around the relationship between reactive oxygen species (ROS) and glucose-6-phosphate dehydrogenase (G6PD), current research around G6PD-deficient patients with viral infections, and limitations as a result of their condition, are inadequate. Here, we analyze existing data around immunological risks, complications, and consequences of this disease, particularly in relation to COVID-19 infections and treatment. The relationship between G6PD deficiency and elevated ROS leading to increased viral load suggests that these patients may confer heightened infectivity. Additionally, worsened prognoses and more severe complications of infection may be realized in class I G6PD-deficient individuals. Though more research is demanded on the topic, preliminary studies suggest that antioxidative therapy which reduces ROS levels in these patients could prove beneficial in the treatment of viral infections in G6PD-deficient individuals.

Extended Cellular Deposits on Gas Exchange Capillaries are Not an Indicator of Clot Formation: Analysis of Different Membrane Oxygenators

Antithrombogenic coatings of artificial surfaces within extracorporeal membrane oxygenation (ECMO) circuits improved its bio- and hemocompatibility. However, there is still a risk of thrombus formation in particular within the membrane oxygenator (MO). Since inflammatory cells are essential components within clots, the aim was to identify the extent of cellular accumulations on gas exchange capillaries from different ECMO systems. Thirty-four MOs (PLS, n = 27, Getinge; Hilite 7000 LT, n = 7, Fresenius Medical Care, Germany) were collected from adult patients. The extent of cellular deposits on gas exchange capillaries was classified using nuclear 4',6-diamidino-2-phenylindole staining and fluorescence microscopy. All Hilite oxygenators exhibited small cellular deposits. In contrast, the cellular distribution was heterogeneous on capillaries from PLS oxygenators: small deposits (34%), clusters (44%) and membrane-spanning cell structures (pseudomembranes) (22%). Overall, the median fluorescence intensity was significantly higher in the PLS group. Nevertheless, within 3 days before MO removal, there was no alteration in critical parameters (d-dimer and fibrinogen levels, platelet counts, and pressure drop across the MO). In conclusion, despite the histological differences on the gas capillaries from different types of oxygenators, there was no further evidence of increased inflammation and coagulation parameters that indicate clot formation within oxygenators.

Monoclonal Gammopathy of Thrombotic Significance

The current review provides an overview of the thrombotic risk observed in patients with MG who do not otherwise require treatment. We discuss clinical and biomarker studies that highlight the heterogenous hemostatic profile observed in these patients and how knowledge has evolved over the past 20 years. Biomarker studies suggest shared biologic features between multiple myeloma and monoclonal gammopathy of undetermined significance (MGUS), which involves both hypercoagulability and platelet activation. Hemostatic abnormalities identified in MGUS patients cannot be translated into clinical practice as they lack correlation to clinical events. The prothrombotic phenotype of MGUS patients has not been ascertained yet, but novel data on coagulation markers are promising. We also review rare conditions associated with the thrombogenic properties of the monoclonal protein that predispose to arterial, venous or microthrombotic events and demonstrate that the M-protein can be linked to clinically significant thrombotic events. Cryoglobulinemia, cryofibrinogenemia, cryo-crystaloglobulinemia and MG-related antiphospholipid syndrome are reviewed. We propose the new umbrella term "monoclonal gammopathy of thrombotic significance" (MGTS) to refer to significant, recurrent thrombotic events in patients with MGUS that provide a rationale for targeting the underlying plasma cell clone. Identifying MGUS patients at high risk for thrombotic events is currently a challenge.

A Nanomedicine Structure-Activity Framework for Research, Development, and Regulation of Future Cancer Therapies

Despite their clinical success in drug delivery applications, the potential of theranostic nanomedicines is hampered by mechanistic uncertainty and a lack of science-informed regulatory guidance. Both the therapeutic efficacy and the toxicity of nanoformulations are tightly controlled by the complex interplay of the nanoparticle's physicochemical properties and the individual patient/tumor biology; however, it can be difficult to correlate such information with observed outcomes. Additionally, as nanomedicine research attempts to gradually move away from large-scale animal testing, the need for computer-assisted solutions for evaluation will increase. Such models will depend on a clear understanding of structure-activity relationships. This review provides a comprehensive overview of the field of cancer nanomedicine and provides a knowledge framework and foundational interaction maps that can facilitate future research, assessments, and regulation. By forming three complementary maps profiling nanobio interactions and pathways at different levels of biological complexity, a clear picture of a nanoparticle's journey through the body and the therapeutic and adverse consequences of each potential interaction are presented.

Infrequent Thrombotic Complications in Japanese Patients with Warm Autoimmune Hemolytic Anemia

Objective Patients with autoimmune hemolytic anemia (AIHA) are considered to be at an increased risk of thrombosis, and prophylaxis for venous thromboembolism (VTE) is often recommended. However, the occurrence of thrombosis in Asian patients has not been specifically studied. Thrombotic complications and features of Japanese warm AIHA (WAIHA) patients were studied to see if Japanese patients were at an increased risk of thrombosis and should receive prophylaxis for VTE. Patients and Methods Forty-seven consecutive patients with warm WAIHA were retrospectively studied. Twenty-nine patients were diagnosed as primary cases and 18 as secondary cases, and 10 patients were diagnosed with Evans syndrome. Results No patient presented with thrombosis, and over a median observation period of 15 months, 3 patients had ischemic cerebral vascular accidents. However, all three of those patients had other known risks for thrombosis, with only one taking thrombotic prophylaxis. No venous thrombosis occurred in any patients during the follow-up period. There was no mortality associated with thrombosis. D-dimer levels were often elevated in patients with WAIHA, indicating that the coagulation was activated in a considerable number of patients, but not to such a level as to be associated with clinically overt thrombosis. Conclusion Thrombotic complications occur infrequently in Japanese WAIHA patients, and these individuals do not appear to be at a particularly increased risk of thrombosis because of WAIHA. The indication of VTE prophylaxis should be determined individually, considering other risks.

Survival in autoimmune hemolytic anemia remains poor, results from a nationwide cohort with 37 years of follow-up

Introduction

Autoimmune hemolytic anemia (AIHA) is considered a chronic disease, with an overall good prognosis. However, recent reports indicate pre‐mature mortality. Causes of death have not been evaluated previously.

Methods

In a nationwide setting, we identified all patients with warm type AIHA or cold agglutinin disease (CAD), and age–sex‐matched comparators from Denmark, 1980–2016. We estimated overall survival and cause‐specific mortality from anemia, infection, cardiovascular causes, hematological or solid cancer, bleeding, or other causes, using cumulative incidence proportions.

Results

We identified 1460 patients with primary AIHA, 1078 with secondary AIHA, 112 with CAD, and 130 801 comparators. One‐year survival and median survival were, 82.7% and 9.8 years for primary AIHA, 69.1% and 3.3 years for secondary AIHA, and 85.5% and 8.8 years for CAD. Prognosis was comparable to the general population only in patients with primary AIHA below 30 years. In all other age and subgroups, the difference was considerable. Cumulated cause‐specific mortality at 1 year was increased among patients versus comparators.

Discussion

All groups of autoimmune hemolytic anemia are associated with increased overall and cause‐specific mortality compared to the general population. This probably reflects unmet needs in both treatment and follow‐up programs.

Mitochondrial reactive oxygen species scavenging attenuates thrombus formation in a murine model of sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is characterized by hemolysis-associated platelet dysfunction that leads to increased risk of thrombosis and plays a role in the high morbidity and mortality of the disease. The mechanisms by which hemolysis induces platelet activation remain unclear. We recently demonstrated that patients with SCD showed increased platelet mitochondrial reactive oxygen species (mtROS) production that correlates with markers of hemolysis and platelet activation. Experiments in isolated platelets demonstrated that mtROS stimulated platelet activation. However, the role of hemolysis-induced mtROS in thrombus formation in vivo remains unclear.

OBJECTIVES

Here, we hypothesize that scavenging of mtROS attenuates the propensity for thrombosis in mouse models of hemolysis.

METHODS

We used models of hemolysate infusion into wildtype mice as well as the Berkley transgenic mouse model of SCD, a chronic mode of hemolysis, to test the effect of hemolysis on platelet mtROS production and thrombosis.

RESULTS

We show that infusion of hemolysate in wildtype mice induces platelet mtROS production and decreases time to vessel occlusion in a model of ferric chloride-induced carotid artery thrombosis. Increased mtROS and propensity for thrombosis was also observed in the Berkley transgenic mouse model of SCD. Notably, treatment with mtROS scavengers decreased platelet mtROS levels and attenuated the propensity for thrombus formation in both models.

CONCLUSIONS

These data demonstrate that mtROS significantly contribute to the mechanism of hemolysis-induced thrombosis in vivo and suggest a potential role for mitochondrially targeted antioxidant therapy in hemolysis and SCD-related thrombosis.

The mystery of 'saturation gap' and falsely normal G6PD: a case of primaquine-induced haemolysis in Plasmodium vivax malaria infection

Eradication therapy in Plasmodium vivax in variants of glucose-6-phosphate dehydrogenase (G6PD) deficiency individuals remains a clinical challenge. We present a case of primaquine-induced methaemoglobinaemia and haemolytic anaemia in a patient with falsely normal qualitative G6PD result during initial presentation, which was complicated with clinical sequelae of thrombosis. Further investigations showed moderate degree of G6PD deficiency. Our patient responded well to vitamin C and a modified weekly regimen of primaquine with no evidence of malaria relapse.

The Controversial Role of Glucose-6-Phosphate Dehydrogenase Deficiency on Cardiovascular Disease: A Narrative Review

Cardiovascular disorders (CVD) are highly prevalent and the leading cause of death worldwide. Atherosclerosis is responsible for most cases of CVD. The plaque formation and subsequent thrombosis in atherosclerosis constitute an ongoing process that is influenced by numerous risk factors such as hypertension, diabetes, dyslipidemia, obesity, smoking, inflammation, and sedentary lifestyle. Among the various risk and protective factors, the role of glucose-6-phosphate dehydrogenase (G6PD) deficiency, the most common inborn enzyme disorder across populations, is still debated. For decades, it has been considered a protective factor against the development of CVD. However, in the recent years, growing scientific evidence has suggested that this inherited condition may act as a CVD risk factor. The role of G6PD deficiency in the atherogenic process has been investigated using in vitro or ex vivo cellular models, animal models, and epidemiological studies in human cohorts of variable size and across different ethnic groups, with conflicting results. In this review, the impact of G6PD deficiency on CVD was critically reconsidered, taking into account the most recent acquisitions on molecular and biochemical mechanisms, namely, antioxidative mechanisms, glutathione recycling, and nitric oxide production, as well as their mutual interactions, which may be impaired by the enzyme defect in the context of the pentose phosphate pathway. Overall, current evidence supports the notion that G6PD downregulation may favor the onset and evolution of atheroma in subjects at risk of CVD. Given the relatively high frequency of this enzyme deficiency in several regions of the world, this finding might be of practical importance to tailor surveillance guidelines and facilitate risk stratification.

Thrombotic Complications in Patients with Immune-Mediated Hemolysis

Autoimmune hemolytic anemias are rare and heterogeneous disorders characterized by hemolysis, which is a well-recognized risk factor for thrombosis. The most common immune-mediated anemias are represented by autoimmune hemolytic anemia and paroxysmal nocturnal hemoglobinuria, both associated with a high rate of thrombosis. Multiple pathophysiological mechanisms for thrombosis have been proposed, involving hemolysis itself and additional effects of the immune system. Despite the increasing awareness of the thrombotic risk in these conditions, evidence-based guidance on prevention and management of thrombotic events is lacking. We herein report available evidence on epidemiological data on thrombosis and thrombophilia in immune-mediated hemolysis, together with possible underlying pathophysiological mechanisms. In addition, we summarize current recommendations for treatment of thrombosis in immune-mediated hemolysis. In particular, we address the issue of thrombotic complications treatment and prophylaxis by proposing a therapeutic algorithm, focusing on specific situations such as splenectomy and pregnancy.

[Abnormal urine color assessment: The urine wheel]

Looking at the urine for diagnostic purposes, once performed by ancient Egyptians, can still provide some valuable clues in modern medicine. Several diseases have been named after their associated urine color and this underlines the clinical value of visual urine inspection: blue diaper disease, purple urine bag syndrome, black urine disease or porphyria. Abnormal urine color could be challenging for the clinician: it may reveal neoplastic disease (urologic cancer; melanoma), cell lysis (rhabdomyolysis; hemolysis), infection (lymphatic filariasis; malaria), enzyme deficiency (porphyria; alkaptonuria), medication or food intake. In this article, we present the diagnostic approach, the mechanisms involved and the main causes of abnormal urine color.

JAK2V617F positive polycythemia vera with paroxysmal nocturnal hemoglobinuria and visceral thromboses: a case report and review of the literature

Background

Polycythemia vera (PV) is characterized by red cell mass expansion in the peripheral blood and can be complicated with thrombosis, bleeding, evolution to acute myeloid leukemia (AML) or a fibrotic phase. Paroxysmal nocturnal hemoglobinuria (PNH) in an acquired clonal haematopoietic stem cell disorder associated with chronic intravascular hemolysis, venous thrombosis, defective hematopoiesis, frequent episodes of infection and, rarely, leukemic transformation. Herein, we report an interesting case of a patient with coexistence of PNH clones and a JAK2V617F positive PV, with unusual thromboses without hemolysis.

Case presentation

A 51-year-old woman presented with increased levels of hematocrit, multiple liver, spleen, and left kidney infarctions and ascites; further investigation revealed a JAK2V617F-positive polycythemia vera and the presence of a significant PNH population (more than 90% CD55– CD59– cells among both granulocytes and red blood cells). Interestingly, the patient has experienced severe thrombotic events without any signs or symptoms of hemolysis.

Conclusions

This case raises questions over uncharted aspects of the PNH etiopathogenesis and its potential association with myeloproliferative neoplasms (MPN) and highlights the difficulty of diagnosing and managing patients with more than one potentially thrombophilic conditions, especially with established and severe thromboses.

Advances in extracorporeal membrane oxygenator design for artificial placenta technology

Extreme prematurity, defined as a gestational age of fewer than 28 weeks, is a significant health problem worldwide. It carries a high burden of mortality and morbidity, in large part due to the immaturity of the lungs at this stage of development. The standard of care for these patients includes support with mechanical ventilation, which exacerbates lung pathology. Extracorporeal life support (ECLS), also called artificial placenta technology when applied to extremely preterm (EPT) infants, offers an intriguing solution. ECLS involves providing gas exchange via an extracorporeal device, thereby doing the work of the lungs and allowing them to develop without being subjected to injurious mechanical ventilation. While ECLS has been successfully used in respiratory failure in full-term neonates, children, and adults, it has not been applied effectively to the EPT patient population. In this review, we discuss the unique aspects of EPT infants and the challenges of applying ECLS to these patients. In addition, we review recent progress in artificial placenta technology development. We then offer analysis on design considerations for successful engineering of a membrane oxygenator for an artificial placenta circuit. Finally, we examine next-generation oxygenators that might advance the development of artificial placenta devices.

Massive intrasplenic arterial thrombosis in a patient with chronic ITP during the development of an Evans syndrome

Long-term safety and efficacy of eltrombopag in adults with persitent/chronic primary immune thrombocytopenia (ITP) evaluated in EXTEND study, showed a high response rate (80%) but, in the clinical safety study, it was observed that 6% of the patients presented venous and arterial thrombotic events. In addition, in the course of the disease, autoimmune hemolytic anemia (Evans syndrome, ES) may occur and could increase the risk of thrombosis. We report an interesting case of splenic rupture due to massive intrasplenic arterial thrombosis in the course of ES in a patient with chronic ITP treated with eltrombopag. The purpose of this case report is to highlight the potential increase in thrombotic risk that may involve the use of eltrombopag in hemolysis situations in patients with ITP.

Linking Labile Heme with Thrombosis

Thrombosis is one of the leading causes of death worldwide. As such, it also occurs as one of the major complications in hemolytic diseases, like hemolytic uremic syndrome, hemorrhage and sickle cell disease. Under these conditions, red blood cell lysis finally leads to the release of large amounts of labile heme into the vascular compartment. This, in turn, can trigger oxidative stress and proinflammatory reactions. Moreover, the heme-induced activation of the blood coagulation system was suggested as a mechanism for the initiation of thrombotic events under hemolytic conditions. Studies of heme infusion and subsequent thrombotic reactions support this assumption. Furthermore, several direct effects of heme on different cellular and protein components of the blood coagulation system were reported. However, these effects are controversially discussed or not yet fully understood. This review summarizes the existing reports on heme and its interference in coagulation processes, emphasizing the relevance of considering heme in the context of the treatment of thrombosis in patients with hemolytic disorders.

Hemolysis and Plasma Free Hemoglobin During Extracorporeal Membrane Oxygenation Support: From Clinical Implications to Laboratory Details

Venovenous and venoarterial extracorporeal membrane oxygenation (ECMO) are lifesaving supports that are more and more frequently used in critically ill patients. Despite of major technological improvements observed during the last 20 years, ECMO-associated hemolysis is still a complication that may arise during such therapy. Hemolysis severity, directly appreciated by plasma free hemoglobin concentration, may be present with various intensity, from a nonalarming and tolerable hemolysis to a highly toxic one. Here, we propose a review dedicated to extracorporeal membrane oxygenation (ECMO)-associated hemolysis, with a particular emphasis on pathophysiology, prevalence, and clinical consequences of such complication. We also focus on laboratory assessment of hemolysis and on the limits that have to be known by clinicians to prevent and manage hemolytic events.

Innate coagulability changes with age in stored packed red blood cells

BACKGROUND

Packed red blood cell (pRBC) units administered during resuscitation from hemorrhagic shock are of varied storage ages. We have previously shown that RBC-derived microparticles' impact on thrombogenesis. However, the impact of storage age on pRBC coagulability is unknown. Therefore, we sought to investigate the effect of storage age on innate coagulability and aggregability of stored pRBCs.

METHODS

pRBCs prepared from male C57BL/6J mice were stored in Additive Solution-3 according to our standardized murine blood banking protocols for 14 days. Rotational thromboelastometry (ROTEM) was used to assess the innate coagulation status of fresh and 14-day old pRBCs. Viscoelastic coagulation parameters of clotting time (CT), clot formation time (CFT), alpha angle, and maximum clot firmness (MCF) were analyzed to determine coagulability. Plasma was added to the fresh pRBCs and 15-day old pRBCs to determine if the storage-associated coagulopathy was reversible with plasma. Statistical analyses were conducted with a Student's t-test.

RESULTS

Fifteen-day old pRBCs demonstrated a significant reduction in MCF (10.3 vs. 24.4 mm, P-value <0.001) and alpha angle (6.0 vs. 27.2 degrees, P-value <0.001) as well as significant prolongation of CFT and CT (1126.5 vs. 571.4 s, P-value <0.001) compared to fresh pRBCs. FFP addition to 15-day old and fresh pRBCs, demonstrated a significant reduction in MCF and persistent prolongation of CFT. This suggests that pRBCs lost coagulability as they aged and this deficit was not completely corrected by plasma administration.

CONCLUSIONS

Storage duration may be an important factor in coagulation potential of pRBCs. Transfusion with older pRBCs may contribute to coagulopathy in massively transfused patients.

Increased risk of thrombotic events in cold agglutinin disease: A 10-year retrospective analysis

BACKGROUND

Cold agglutinin disease (CAD) is a rare autoimmune hemolytic anemia mediated by IgM autoantibodies that trigger hemolysis via classical complement pathway. Increased incidence of thrombotic events (TEs) has been reported in patients with other forms of hemolysis. The incidence of TEs in patients with CAD is unknown.

OBJECTIVE

Evaluate TE risk in patients with CAD.

PATIENTS/METHODS

This is a matched cohort comparison study evaluating the risk of TEs in patients with CAD and without CAD over a 10-year period. A total of 608 patients with CAD were identified in the Optum Claims-Clinical data set by reviewing clinical notes for CAD terms and matched with up to 10 patients without CAD (N = 5873). TEs were defined as the first medical claim for a TE using International Classification of Diseases, Ninth and Tenth Revision codes. Cox regression models were used to estimate time to first TE. Sensitivity analyses were conducted to estimate TE risk among patients with primary CAD.

RESULTS

At least 1 TE occurred in 29.6% of patients with CAD and 17.6% of patients without CAD. The proportion of patients experiencing venous, arterial, and cerebral TEs were each higher among CAD patients. The overall risk of having TEs was higher in patients with CAD (adjusted hazard ratio [aHR], 1.94; 95% confidence interval [CI], 1.64-2.30). Patients with presumed primary CAD also demonstrated an increased risk of TEs (aHR, 1.80; 95% CI, 1.46-2.22). Patients with CAD with the fewest comorbidities had 2.44-fold higher risk of having a TE (95% CI, 1.70-3.52).

CONCLUSIONS

Patients with CAD have an increased risk of TEs when compared with a matched non-CAD population.

A Computational Approach for Mapping Heme Biology in the Context of Hemolytic Disorders

Heme is an iron ion-containing molecule found within hemoproteins such as hemoglobin and cytochromes that participates in diverse biological processes. Although excessive heme has been implicated in several diseases including malaria, sepsis, ischemia-reperfusion, and disseminated intravascular coagulation, little is known about its regulatory and signaling functions. Furthermore, the limited understanding of heme's role in regulatory and signaling functions is in part due to the lack of curated pathway resources for heme cell biology. Here, we present two resources aimed to exploit this unexplored information to model heme biology. The first resource is a terminology covering heme-specific terms not yet included in standard controlled vocabularies. Using this terminology, we curated and modeled the second resource, a mechanistic knowledge graph representing the heme's interactome based on a corpus of 46 scientific articles. Finally, we demonstrated the utility of these resources by investigating the role of heme in the Toll-like receptor signaling pathway. Our analysis proposed a series of crosstalk events that could explain the role of heme in activating the TLR4 signaling pathway. In summary, the presented work opens the door to the scientific community for exploring the published knowledge on heme biology.

Fatal fulminant hemolysis-associated pulmonary embolism in mixed-type autoimmune hemolytic anemia: A case report

RATIONALE

Autoimmune hemolytic AQ5 anemia (AIHA) is an immune disorder caused by antibodies directed against unmodified autologous red blood cells. In rare cases, AIHA is comorbid with other immunological disorders; for instance, when AIHA is complicated with immunologic thrombocytopenic purpura (ITP) it is called Evans Syndrome (ES). These multiple autoimmune mechanisms are referred to as "immunological tolerance loss," which is known as a characteristic autoimmunity specific for AIHA. And there are no estimation of the risk for thromboembolism in the "immunological tolerance loss" case.

PATIENT CONCERNS

A 66-year-old man was diagnosed with ES after autologous stem cell transplantation for malignant lymphoma. His background immunological status was complicated because AIHA was mixed-type (warm and cold antibody type). The direct/indirect Coombs tests were positive. The anticomplement antibody was positive and his cold hemagglutinin level had increased. Anticardiolipin antibodies were negative: anticardiolipin β2GPI antibody ≤1.2 U/mL (<3.5), anticardiolipin immunoglobulin G antibody ≤8 U/mL (<10), and anticardiolipin immunoglobulin M antibody ≤5 U/mL (<8).

DIAGNOSES

ITP and mixed-type AIHA.

INTERVENTIONS

The patient achieved complete response by initial prednisolone therapy; however, he did not respond to corticosteroid therapy after AIHA recurrence. He required the red blood cell transfusion due to the progression of hemolytic anemia.

OUTCOMES

On the fourth day of refractory treatment following AIHA recurrence, the patient had acute respiratory failure with severe hypoxia and died. The cause of death was identified as pulmonary embolism (PE) based on the laboratory data and echocardiography findings, and a literature search suggested rapidly progressive hemolysis-induced PE.

LESSONS

Although infrequent, comorbid thromboembolism to AIHA is well documented; however, a mixed-type AIHA case complicated with thromboembolism has not been previously reported. The combined pathophysiology of AIHA and thromboembolism should be considered in the clinical course of hemolysis. Our case suggested multiple immunological background, ITP, and mixed type AIHA, could be associated to a risk for thromboembolism (TE).

Splenectomy and the incidence of venous thromboembolism and sepsis in patients with autoimmune hemolytic anemia

INTRODUCTION

The impact of splenectomy on venous thrombosis (VTE), abdominal thrombosis (abVTE) and sepsis in autoimmune hemolytic anemia (AIHA) is unclear.

METHODS

Using the California Discharge Dataset 1991-2014, 4756 AIHA patients were identified. Cumulative incidences (CI) of VTE, abVTE, and sepsis were determined in patients with and without splenectomy. Using propensity score matching adjusted for competing risk of death, the association between VTE, abVTE and sepsis with splenectomy was determined.

RESULTS

In those without splenectomy, the CIs of VTE, abVTE, and sepsis were 1.4%, 0.2%, and 4.3% respectively, compared to 4.4%, 3.0% and 6.7% with splenectomy. Splenectomy was associated with increased risk for VTE in immediate (HR 2.66, CI 1.36-5.23) and late (HR 3.29, CI 2.10-5.16) post-operative periods. AbVTE was increased in immediate post-operative period (HR 34.11, CI 4.93-236.11). Sepsis was only increased in late post-operative period (HR 2.20, CI 1.75-2.77). In multivariate models, older age, having >1 comorbidity and having VTE, abVTE, and sepsis were associated with increased mortality. Splenectomy was not associated with increased mortality.

DISCUSSION

Splenectomy in AIHA was associated with significant early thrombotic risk and long-term morbidity. Future research should evaluate the role of splenectomy in AIHA patients, and potential long-term thrombotic and antibiotic prophylaxis.

The Hemocompatibility of Nanoparticles: A Review of Cell-Nanoparticle Interactions and Hemostasis

Understanding cell-nanoparticle interactions is critical to developing effective nanosized drug delivery systems. Nanoparticles have already advanced the treatment of several challenging conditions including cancer and human immunodeficiency virus (HIV), yet still hold the potential to improve drug delivery to elusive target sites. Even though most nanoparticles will encounter blood at a certain stage of their transport through the body, the interactions between nanoparticles and blood cells is still poorly understood and the importance of evaluating nanoparticle hemocompatibility is vastly understated. In contrast to most review articles that look at the interference of nanoparticles with the intricate coagulation cascade, this review will explore nanoparticle hemocompatibility from a cellular angle. The most important functions of the three cellular components of blood, namely erythrocytes, platelets and leukocytes, in hemostasis are highlighted. The potential deleterious effects that nanoparticles can have on these cells are discussed and insight is provided into some of the complex mechanisms involved in nanoparticle-blood cell interactions. Throughout the review, emphasis is placed on the importance of undertaking thorough, all-inclusive hemocompatibility studies on newly engineered nanoparticles to facilitate their translation into clinical application.

Immunotoxicity Considerations for Next Generation Cancer Nanomedicines

Although interest and funding in nanotechnology for oncological applications is thriving, translating these novel therapeutics through the earliest stages of preclinical assessment remains challenging. Upon intravenous administration, nanomaterials interact with constituents of the blood inducing a wide range of associated immunotoxic effects. The literature on the immunological interactions of nanomaterials is vast and complicated. A small change in a particular characteristic of a nanomaterial (e.g., size, shape, or charge) can have a significant effect on its immunological profile in vivo, and poor selection of specific assays for establishing these undesirable effects can overlook this issue until the latest stages of preclinical assessment. This work describes the current literature on unintentional immunological effects associated with promising cancer nanomaterials (liposomes, dendrimers, mesoporous silica, iron oxide, gold, and quantum dots) and puts focus on what is missing in current preclinical evaluations. Opportunities for avoiding or limiting immunotoxicity through efficient preclinical assessment are discussed, with an emphasis placed on current regulatory views and requirements. Careful consideration of these issues will ensure a more efficient preclinical assessment of cancer nanomedicines, enabling a smoother clinical translation with less failures in the future.

The blood compatibility challenge. Part 3: Material associated activation of blood cascades and cells

Following protein adsorption/activation which is the first step after the contact of material surfaces and whole blood (part 2), fibrinogen is converted to fibrin and platelets become activated and assembled in the form of a thrombus. This thrombus formation is the key feature that needs to be minimized in the creation of materials with low thrombogenicity. Further aspects of blood compatibility that are important on their own are complement and leukocyte activation which are also important drivers of thrombus formation. Hence this review summarizes the state of knowledge on all of these cascades and cells and their interactions. For each cascade or cell type, the chapter distinguishes statements which are in widespread agreement from statements where there is less of a consensus. STATEMENT OF SIGNIFICANCE: This paper is part 3 of a series of 4 reviews discussing the problem of biomaterial associated thrombogenicity. The objective was to highlight features of broad agreement and provide commentary on those aspects of the problem that were subject to dispute. We hope that future investigators will update these reviews as new scholarship resolves the uncertainties of today.

Sickle red blood cells are more susceptible to in vitro haemolysis when exposed to normal saline versus Plasma-Lyte A

BACKGROUND

Normal saline has been the fluid of choice for resuscitation, rehydration and fluid replacement during plasma or red cell exchange/cytapheresis. There are increased concerns about its clinical effects and data showing it causes more haemolysis in vitro than buffered solutions such as Plasma-Lyte A.

METHODS

We investigated whether normal saline or Plasma-Lyte A was associated with greater haemolysis during hours of in vitro incubation with both normal red cells and samples from patients with sickle cell anaemia.

RESULTS

Sickle red cells haemolysed more than normal red cells did in both crystalloid solutions. The results of 24-hour exposure to saline were particularly striking (median of 163 mg/dl (IQ range 105-247) for sickle red cells vs. 53 (48-92) for normal red cells (P < 0·0001). In patient samples containing variable quantities of haemoglobin S red cells, increased haemoglobin S was associated with increased haemolysis. This effect was greater for normal saline than Plasma-Lyte A (P = 0·12).

CONCLUSIONS

These in vitro models demonstrate that short-term ex vivo exposure of sickle red cells to normal saline leads to greater haemolysis than short-term exposure of normal red cells, and this effect is exacerbated by normal saline. Whether use of normal saline causes increased haemolysis in vivo is unknown. Given recent evidence that normal saline increases renal failure and mortality in critically ill patients, further studies are urgently needed.

[Hemolytic disorders and venous thrombosis: An update]

Many factors can contribute to the risk of venous thrombosis observed in hemolytic diseases. Some mechanisms are related to hemolysis by itself, while others seem more specific to each disease. Despite recent advances in the quantification of this risk and in understanding its physiopathology, the association of hemolysis with venous thrombosis is often unknown. The purpose of this general review is to clarify the main pro-thrombotic mechanisms during hemolysis and to synthesize the clinical data currently available. We will focus on the main types of hemolytic pathologies encountered in current practice, namely paroxysmal nocturnal hemoglobinuria, hemoglobinopathies, auto-immune hemolytic anemia and thrombotic microangiopathies.

Coagulation and Bleeding Management in Pediatric Extracorporeal Membrane Oxygenation: Clinical Scenarios and Review

Extracorporeal membrane oxygenation (ECMO) is a life-saving procedure that requires careful coagulation management. Indications for ECMO continue to expand, leading to more complicated patients treated by ECMO teams. At our pediatric institution, we utilize a Coagulation Team to guide anticoagulation, transfusion and hemostasis management in an effort to avoid the all-to-common complications of bleeding and thrombosis. This team formulates a coagulation plan in conjunction with a multidisciplinary ECMO team after careful review of all available laboratory data as well as the patient's clinical status. Here, we present our general strategies for ECMO management in various clinical scenarios and a review of the literature pertaining to coagulation management in the pediatric ECMO setting.

[A case of autoimmune hemolytic anemia diagnosed by occurrence of cardioembolic stroke]

A 79-year-old woman came to us because of sudden onset of dysarthria. She had taken apixaban due to her non-valvular atrial fibrillation. A neurological examination revealed mild facial palsy of her right side, and magnetic resonance imaging showed acute brain infarction at the left frontal lobe. There were no stenotic lesions on intracranial or extracranial magnetic resonance angiography, and she was diagnosed with cardioembolic stroke. Intravenous infusion of heparin and edaravone was initiated, and her neurological symptoms improved. However, she gradually developed jaundice and anemia. Gastro-intestinal bleeding was not observed, and her blood test met the diagnostic criteria for hemolytic anemia. Because both the direct Coombs test and cold agglutinin were positive, she was diagnosed with mixed-type autoimmune hemolytic anemia. Although her serum hemoglobin level decreased to 7.0 g/dl on the 12th hospital day, her anemia gradually improved after steroidal therapy with transfusion. It was revealed that she had shown mild anemia (hemoglobin: 9.2-10.9 g/dl) and hyperbilirubinemia (total bilirubin: 1.8-2.6 mg/dl) for 6 months. Therefore, her latent autoimmune hemolytic anemia became activated with the occurrence of cardioembolic stroke. Autoimmune hemolytic anemia might have promoted cardiac thrombus formation despite the administration of an anticoagulant in this case. It should be noted that autoimmune hemolytic anemia can develop as thrombotic disease. In the present case, autoimmune hemolytic anemia was diagnosed based on the development of cardioembolic stroke.

Venous thromboembolic events during warm autoimmune hemolytic anemia

Thrombotic manifestations are a hallmark of many auto-immune diseases (AID), specially of warm autoimmune hemolytic anemia (wAIHA), as 15 to 33% of adults with wAIHA experience venous thromboembolic events (VTE). However, beyond the presence of positive antiphospholipid antibodies and splenectomy, risk factors for developing a VTE during wAIHA have not been clearly identified. The aim of this retrospective study was to characterize VTEs during wAIHA and to identify risk factors for VTE. Forty-eight patients with wAIHA were included, among whom 26 (54%) had secondary wAIHA. Eleven (23%) patients presented at least one VTE, that occurred during an active phase of the disease for 10/11 patients (90%). The frequency of VTE was not different between primary and secondary AIHA (23.7 vs. 19.2%; p = 0.5). The Padua prediction score based on traditional risk factors was not different between patients with and without VTE. On multivariate analysis, total bilirubin ≥ 40 μmol/L [odds ratio (OR) = 7.4; p = 0.02] and leucocyte count above 7x10⁹/L (OR = 15.7; p = 0.02) were significantly associated with a higher risk of thrombosis. Antiphospholipid antibodies were screened in 9 out the 11 patients who presented a VTE and were negative. Thus, the frequency of VTE is high (23%) during wAIHA and VTE preferentially occur within the first weeks of diagnosis. As no clinically relevant predictive factors of VTE could be identified, the systematic use of a prophylactic anticoagulation should be recommended in case of active hemolysis and its maintenance after hospital discharge should be considered. The benefit of a systematic screening for VTE and its procedure remain to be determined.

How I diagnose and treat venous thromboembolism in sickle cell disease

The incidence of venous thromboembolism (VTE) in adult patients with sickle cell disease (SCD) is high. However, overlapping features between the clinical presentation of VTE and SCD complications and a low index of suspicion for thrombosis can influence patient management decisions. VTE in SCD can therefore present management challenges to the clinical hematologist. Herein, we present 3 distinct clinical vignettes that are representative of our clinical practice with SCD patients. These vignettes are discussed with specific reference to the hypercoagulable state in SCD patients, recent VTE diagnosis and anticoagulant therapy guidelines from the general population, and evaluation of the risk of bleeding as a result of long-term exposure to anticoagulant therapy. We examine current diagnostic and treatment options, highlight limitations of the existing clinical prognostic models that offer personalized guidance regarding the duration of anticoagulation, and propose a clinical approach to guide the decision to extend anticoagulation beyond 3 months.

Elevated free hemoglobin and decreased haptoglobin levels are associated with adverse clinical outcomes, unfavorable physiologic measures, and altered inflammatory markers in pediatric cardiac surgery patients

BACKGROUND

There are data suggesting that free hemoglobin (Hb), heme, and iron contribute to infection, thrombosis, multiorgan failure, and death in critically ill patients. These outcomes may be mitigated by haptoglobin.

STUDY DESIGN AND METHODS

164 consecutively treated children undergoing surgery for congenital heart disease were evaluated for associations between free Hb and haptoglobin and clinical outcomes, physiologic metrics, and biomarkers of inflammation RESULTS: Higher perioperative free Hb levels (and lower haptoglobin levels) were associated with mortality, nosocomial infection, thrombosis, hours of intubation and inotropes, increased interleukin-6, peak serum lactate levels, and lower nadir mean arterial pressures. The median free Hb in patients without infection (30 mg/dL; 29 interquartile range [IQR], 24-52 mg/dL) was lower than in those who became infected (39 mg/dL; IQR, 33-88 mg/ 31 dL; p = 0.0046). The median mechanical ventilation requirements were 19 (IQR, 7-72) hours in patients with higher levels of haptoglobin versus 48 (IQR, 18-144) hours in patients with lower levels (p = 0.0047). Transfusion dose, bypass duration, and complexity of surgery were all significantly correlated with Hb levels and haptoglobin levels. Multivariate analyses demonstrated that these variables were independently and significantly associated with outcomes.

CONCLUSIONS

Elevated pre- and postoperative levels of free Hb and decreased levels of haptoglobin were associated with adverse clinical outcomes, inflammation, and unfavorable physiologic metrics. Transfusion, RACHS score, and duration of bypass were associated with increased free Hb and decreased haptoglobin. Further investigation of the role of hemolysis and haptoglobin as potential mediators or markers of outcomes is warranted.

Expediting red blood cell transfusions by syringing causes significant hemolysis

BACKGROUND

Techniques commonly used to expedite blood transfusions include pneumatically pressurizing red blood cell (RBC) bags or manual syringing its contents. We compared these techniques on RBC hemolysis using a simulated transfusion model.

STUDY DESIGN AND METHODS

Fifteen warmed RBC units that were 12.3 ± 4.3 (95% confidence interval [CI], 10.1-14.5) days old were each subjected to two experimental rapid transfusion techniques. RBCs from each technique were directed through 18- and 22-gauge cannulas attached to blood administration sets. One technique involved RBC bag pressurization to 300 mmHg. The other employed a 20-mL syringe to effect forceful, manual aspiration from the RBC bag followed by forceful, manual RBC injection. The control group was gravity driven without cannulas. Free hemoglobin (Hb) concentrations were measured and percent hemolysis was calculated.

RESULTS

Free Hb concentrations and percent hemolysis (median [95% CI]) were similar in the control (0.05 [0.03-0.08] g/dL and 0.13% [0.09%-0.17%], respectively) and pressurized experiments (0.06 [0.05-0.09] g/dL; 0.14% [0.12%-0.22%]), respectively. Syringing resulted in 10-fold higher free Hb concentrations (0.55 [0.38-0.92] g/dL) and percent hemolysis (1.28% [1.03%-2.15%]) than when employing the control (p < 0.0001) or pressurization (p < 0.0001) techniques. Cannula sizes studied did not affect hemolysis.

CONCLUSION

Forceful manual syringing caused significant hemolysis and high free Hb concentrations. Pressurizing RBC bags induced no more hemolysis than after gravity-facilitated transfusions. Syringing to expedite RBC transfusions should be avoided in favor of pneumatic RBC bag pressurization.

Positive predictive value of diagnosis coding for hemolytic anemias in the Danish National Patient Register

Purpose

The nationwide public health registers in Denmark provide a unique opportunity for evaluation of disease-associated morbidity if the positive predictive values (PPVs) of the primary diagnosis are known. The aim of this study was to evaluate the predictive values of hemolytic anemias registered in the Danish National Patient Register.

Patients and methods

All patients with a first-ever diagnosis of hemolytic anemia from either specialist outpatient clinic contact or inpatient admission at Odense University Hospital from January 1994 through December 2011 were considered for inclusion. Patients with mechanical reason for hemolysis such as an artificial heart valve, and patients with vitamin-B12 or folic acid deficiency were excluded.

Results

We identified 412 eligible patients: 249 with a congenital hemolytic anemia diagnosis and 163 with acquired hemolytic anemia diagnosis. In all, hemolysis was confirmed in 359 patients, yielding an overall PPV of 87.1% (95% confidence interval [CI]: 83.5%–90.2%). A diagnosis could be established in 392 patients of whom 355 patients had a hemolytic diagnosis. Diagnosis was confirmed in 197 of the 249 patients with congenital hemolytic anemia, yielding a PPV of 79.1% (95% CI: 73.5%–84.0%). Diagnosis of acquired hemolytic anemia could be confirmed in 136 of the 163 patients, resulting in a PPV of 83.4% (95% CI: 76.8%–88.8%). For hemoglobinopathy PPV was 84.1% (95% CI: 77.4%–89.4%), for hereditary spherocytosis PPV was 80.6% (95% CI: 69.5%–88.9%), and for autoimmune hemolytic anemia PPV was 78.4% (95% CI: 70.4%–85.0%).

Conclusion

The PPV of hemolytic anemias was moderately high. The PPVs were comparable in the three main categories of overall hemolysis, and congenital and acquired hemolytic anemia.

Mechanical blood trauma in assisted circulation: sublethal RBC damage preceding hemolysis

After many decades of improvements in mechanical circulatory assist devices (CADs), blood damage remains a serious problem during support contributing to variety of adverse events, and consequently affecting patient survival and quality of life. The mechanisms of cumulative cell damage in continuous-flow blood pumps are still not fully understood despite numerous in vitro, in vivo, and in silico studies of blood trauma. Previous investigations have almost exclusively focused on lethal blood damage, namely hemolysis, which is typically negligible during normal operation of current generation CADs. The measurement of plasma free hemoglobin (plfHb) concentration to characterize hemolysis is straightforward, however sublethal trauma is more difficult to detect and quantify since no simple direct test exists. Similarly, while multiple studies have focused on thrombosis within blood pumps and accessories, sublethal blood trauma and its sequelae have yet to be adequately documented or characterized. This review summarizes the current understanding of sublethal trauma to red blood cells (RBCs) produced by exposure of blood to flow parameters and conditions similar to those within CADs. It also suggests potential strategies to reduce and/or prevent RBC sublethal damage in a clinically-relevant context, and encourages new research into this relatively uncharted territory.

Free hemoglobin increases von Willebrand factor-mediated platelet adhesion in vitro: implications for circulatory devices

Intravascular hemolysis occurs in patients on extracorporeal membrane oxygenation. High levels of free acellular adult hemoglobin (free HbA) are associated with clotting in this mechanical device that can result in thrombotic complications. Adsorption of fibrinogen onto the surface of biomaterial correlates with platelet adhesion, which is mediated by von Willebrand factor (VWF). Because free Hb interacts with VWF, we studied the effect of hemoglobin (Hb) on platelet adhesion to fibrin(ogen) under conditions of different hydrodynamic forces. This effect was investigated using purified human HbA and fibrinogen, extracellular matrix, collagen, or purified plasma VWF as surface-coated substrates to examine flow-dependent platelet adhesion. Antibodies and VWF-deficient plasma were also used. Free Hb (≥50 mg/dL) effectively augmented platelet adhesion, and microthrombi formation on fibrin(ogen), extracellular matrix, and collagen at high shear stress. The effect of free Hb was effectively blocked by anti-glycoprotein Ibα (GPIbα) antibodies or depletion of VWF. Unexpectedly, free Hb also promoted firm platelet adhesion and stable microthrombi on VWF. Lastly, we determined that Hb interacts directly with the A1 domain. This study is the first to demonstrate that extracellular Hb directly affects the GPIbα-VWF interaction in thrombosis, and describes another mechanism by which hemolysis is connected to thrombotic events.

Venous thromboembolism related to warm autoimmune hemolytic anemia: a case-control study

BACKGROUND

The risk of venous thromboembolism (VTE) during warm autoimmune hemolytic anemia (wAIHA) is apparent in several published series. Unlike proximate disorders (autoimmune thrombocytopenia, non-immune hemolytic diseases) little is known about the presentation and risk factors for VTE in this setting.

OBJECTIVE

To determine the frequency, presentation and risk factors for VTE associated with wAIHA.

METHODS

We performed a single center retrospective study of adult patients (>18years) followed for wAIHA between 2009 and 2013. VTE risk factors were systematically assessed. The characteristics of patients with or without VTE were compared. VTE presentation and precipitating factors were analyzed. The Padua VTE risk score was calculated in each case.

RESULTS

Forty patients were included. wAIHA was idiopathic in 24 patients (60%). Twelve patients (30%) had Evans syndrome. Mean lowest hemoglobin level was 6.6g/dl [3.7-11.5]. Eight patients (20%) presented VTE after the appearance of wAIHA, at a mean age of 52.5years. All patients had pulmonary embolus, associated with a deep venous thrombosis in 4 cases. At the time of VTE 7/8 patients had frank hemolysis (median hemoglobin level: 7g/dL) and 6/8 were outpatients with a low Padua VTE risk score. The frequency of usual VTE risk factor was similar in cases and controls. By contrast, lowest hemoglobin level was significantly lower in patients that experienced VTE (5.3 vs 7.2g/dL, p=0.016). During the first episode of wAIHA, patients with concurrent VTE had a more pronounced anemia (5.3 vs 7.4g/dL, p=0.026). At the time of VTE, anemia was more severe when no other precipitating factor was present (6 vs 8.9g.dL, p=0.04).

CONCLUSION

In our cohort, 20% of patients with wAIHA presented VTE. The vast majority of VTE occurred during severe hemolytic flares and were not attributable to usual VTE risk factors. VTE prophylaxis is advisable in any patient admitted for wAIHA, irrespective of Padua VTE risk score. Prophylaxis also seems reasonable for outpatients with marked hemolysis.

Unconjugated bilirubin inhibits proteolytic cleavage of von Willebrand factor by ADAMTS13 protease

BACKGROUND

Bilirubin is a yellow breakdown product of heme catabolism. Increased serum levels of unconjugated bilirubin are conditions commonly seen in premature neonates and adults with acute hemolysis including thrombotic microangiopathy. Previous studies have shown that unconjugated bilirubin lowers plasma ADAMTS13 activity, but the mechanism is not fully understood.

OBJECTIVES

The study is to determine whether unconjugated bilirubin directly inhibits the cleavage of von Willebrand factor (VWF) and its analogs by ADAMTS13.

METHODS

Fluorogenic, surface-enhanced laser desorption/ionization time-of-flight mass spectrometric assay, and Western blotting analyses were used to address this question.

RESULTS

Unconjugated bilirubin inhibits the cleavage of F485-rVWF73-H, D633-rVWF73-H, and GST-rVWF71-11K by ADAMTS13 in a concentration-dependent manner with a half-maximal inhibitory concentration of ~13, ~70, and ~17 μmol L(-1) , respectively. Unconjugated bilirubin also dose-dependently inhibits the cleavage of multimeric VWF by ADAMTS13 under denaturing conditions. The inhibitory activity of bilirubin on the cleavage of D633-rVWF73-H and multimeric VWF, but not F485-rVWF73-H, was eliminated after incubation with bilirubin oxidase that converts bilirubin to biliverdin. Furthermore, plasma ADAMTS13 activity in patients with hyperbilirubinemia increased after treatment with bilirubin oxidase.

CONCLUSIONS

Unconjugated bilirubin directly inhibits ADAMTS13's ability to cleave both peptidyl and native VWF substrates in addition to its interference with certain fluorogenic assays. Our findings may help proper interpretation of ADAMTS13 results under pathological conditions. Whether elevated serum unconjugated bilirubin has prothrombotic effect in vivo remains to be determined in our future study.