Anticoagulation with the oral direct thrombin inhibitor dabigatran does not enlarge hematoma volume in experimental intracerebral hemorrhage

A Combination of Ex Vivo and In Vivo Strategies for Evaluating How Much New Oral Anticoagulants Exacerbate Experimental Intracerebral Bleeding

Background  Intracerebral hemorrhage is the most serious complication of anticoagulant therapy but the effects of different types of oral anticoagulants on the expansion of these hemorrhages are still unclear. Clinical studies have revealed controversial results; more robust and long-term clinical evaluations are necessary to define their outcomes. An alternative is to test the effect of these drugs in experimental models of intracerebral bleeding induced in animals. Aims  To test new oral anticoagulants (dabigatran etexilate, rivaroxaban, and apixaban) in an experimental model of intracerebral hemorrhage induced by collagenase injection into the brain striatum of rats. Warfarin was used for comparison. Methods  Ex vivo anticoagulant assays and an experimental model of venous thrombosis were employed to determine the doses and periods of time required for the anticoagulants to achieve their maximum effects. Subsequently, volumes of brain hematoma were evaluated after administration of the anticoagulants, using these same parameters. Volumes of brain hematoma were evaluated by magnetic resonance imaging, H&E (hematoxylin and eosin) staining, and Evans blue extravasation. Neuromotor function was assessed by the elevated body swing test. Results and Conclusions  The new oral anticoagulants did not increase intracranial bleeding compared with control animals, while warfarin markedly favored expansion of the hematomas, as revealed by magnetic resonance imaging and H&E staining. Dabigatran etexilate caused a modest but statistically significant increase in Evans blue extravasation. We did not observe significant differences in elevated body swing tests among the experimental groups. The new oral anticoagulants may provide a better control over a brain hemorrhage than warfarin.

Animal models for the study of intracranial hematomas (Review)

Intracranial hematomas (ICH) are a frequent condition in neurosurgical and neurological practices, with several mechanisms of primary and secondary injury. Experimental research has been fundamental for the understanding of the pathophysiology implicated with ICH and the development of therapeutic interventions. To date, a variety of different animal approaches have been described that consider, for example, the ICH evolutive phase, molecular implications and hemodynamic changes. Therefore, choosing a test protocol should consider the scope of each particular study. The present review summarized investigational protocols in experimental research on the subject of ICH. With this subject, injection of autologous blood or bacterial collagenase, inflation of intracranial balloon and avulsion of cerebral vessels were the models identified. Rodents (mice) and swine were the most frequent species used. These different models allowed improvements on the understanding of intracranial hypertension establishment, neuroinflammation, immunology, brain hemodynamics and served to the development of therapeutic strategies.

Vildagliptin improves neurological function by inhibiting apoptosis and ferroptosis following intracerebral hemorrhage in mice

Intracerebral hemorrhage (ICH) is a fatal health problem which lacks effective treatment. The apoptosis caused by hematoma constituents, and the ferroptosis due to iron overload, are prominent contributors of neurologic impairment after ICH. Targeting cell death pathways may thus be a therapeutic strategy for neuroprotection and functional recovery in ICH. Vildagliptin (Vilda), a dipeptidyl peptidase (DPP)-4 inhibitor, has been reported to have potent anti-apoptosis and anti-ferroptotic capacity. However, it is not clear whether Vilda has anti-cell death efficacy in ICH. In the present study, the potential neuroprotective effect of Vilda in ICH mice was investigated. Mice were randomly divided into three groups: sham, ICH + saline or ICH + Vilda. ICH was induced by collagenase type VII micro-injection into the right basal ganglia. Vilda (50 mg/kg/day; gavage) daily treatment for 3 days after ICH improved neurological deficit scores, reduced hematoma volume, and inhibited degeneration of neurons. The activation of microglia/macrophages and infiltration of neutrophil were restrained by Vilda. Moreover, Vilda attenuated brain cell apoptosis as determined by TUNEL staining, raised Bcl-2 protein level, and simultaneously suppressed Bax as validated by western blots. In addition, Vilda reduced malondialdehyde level, elevated glutathione peroxidase brain content, and alleviated iron deposition at 3 days after ICH in mice. In conclusion, Vilda exerts neuroprotective effects in ICH, at least in part by inhibiting neuroinflammation, and preventing neuronal apoptosis and ferroptosis following ICH.

Novel targets, treatments, and advanced models for intracerebral haemorrhage

Intracerebral haemorrhage (ICH) is the second most common type of stroke and a major cause of mortality and disability worldwide. Despite advances in surgical interventions and acute ICH management, there is currently no effective therapy to improve functional outcomes in patients. Recently, there has been tremendous progress uncovering new pathophysiological mechanisms underlying ICH that may pave the way for the development of therapeutic interventions. Here, we highlight emerging targets, but also existing gaps in preclinical animal modelling that prevent their exploitation. We particularly focus on (1) ICH aetiology, (2) the haematoma, (3) inflammation, and (4) post-ICH pathology. It is important to recognize that beyond neurons and the brain, other cell types and organs are crucially involved in ICH pathophysiology and successful interventions likely will need to address the entire organism. This review will spur the development of successful therapeutic interventions for ICH and advanced animal models that better reflect its aetiology and pathophysiology.

Formyl peptide receptor 1 signaling potentiates inflammatory brain injury

Acute brain insults elicit pronounced inflammation that amplifies brain damage in intracerebral hemorrhage (ICH). We profiled perihematomal tissue from patients with ICH, generating a molecular landscape of the injured brain, and identified formyl peptide receptor 1 (FPR1) as the most abundantly increased damage-associated molecular pattern (DAMP) receptor, predominantly expressed by microglia. Circulating mitochondrial N-formyl peptides, endogenous ligands of FPR1, were augmented and correlated with the magnitude of brain edema in patients with ICH. Interactions of formyl peptides with FPR1 activated microglia, boosted neutrophil recruitment, and aggravated neurological deficits in two mouse models of ICH. We created an FPR1 antagonist T-0080 that can penetrate the brain and bind both human and murine FPR1. T-0080 attenuated brain edema and improved neurological outcomes in ICH models. Thus, FPR1 orchestrates brain inflammation after ICH and could be targeted to improve clinical outcome in patients.

In vivo characterization of spontaneous microhemorrhage formation in mice with cerebral amyloid angiopathy

The pathophysiology of microhemorrhages in the context of cerebral amyloid angiopathy (CAA) remains poorly understood. Here we used in vivo two-photon microscopy in aged APP/PS1 mice with mild-to-moderate CAA to assess the formation of microhemorrhages and their spatial relationship with vascular Aβ depositions in the surrounding microvascular network. Mice with chronic cranial windows were intravenously injected with fluorescent dextran to visualize the vessels and a fluorescently labeled anti-fibrin antibody to visualize microhemorrhages. Focal vessel irradiations resulted in extravascular fibrin-positive clots at individual rupture sites that remained visible for weeks. Spontaneous extravascular fibrin-positive clots were more often observed in 19-month-old transgenic APP/PS1 mice compared to their wild-type littermate controls (p = 0.039), after heparin administration. In the transgenic mice, these spontaneous leakage sites frequently occurred at arteriolar segments without CAA at bifurcations or vessel bends. These findings suggest that the presence of vascular Aβ per se does not directly predispose vessels to leak, but that complex flow dynamics within CAA-affected vascular networks likely play a role. Our in vivo approach for the detection of individual spontaneous leakage sites may be used in longitudinal studies aimed to assess structural and functional alterations at the single-vessel level leading up to microhemorrhage formation.

The Role of Thrombin in Brain Injury After Hemorrhagic and Ischemic Stroke

Thrombin is increased in the brain after hemorrhagic and ischemic stroke primarily due to the prothrombin entry from blood either with a hemorrhage or following blood-brain barrier disruption. Increasing evidence indicates that thrombin and its receptors (protease-activated receptors (PARs)) play a major role in brain pathology following ischemic and hemorrhagic stroke (including intracerebral, intraventricular, and subarachnoid hemorrhage). Thrombin and PARs affect brain injury via multiple mechanisms that can be detrimental or protective. The cleavage of prothrombin into thrombin is the key step of hemostasis and thrombosis which takes place in every stroke and subsequent brain injury. The extravascular effects and direct cellular interactions of thrombin are mediated by PARs (PAR-1, PAR-3, and PAR-4) and their downstream signaling in multiple brain cell types. Such effects include inducing blood-brain-barrier disruption, brain edema, neuroinflammation, and neuronal death, although low thrombin concentrations can promote cell survival. Also, thrombin directly links the coagulation system to the immune system by activating interleukin-1α. Such effects of thrombin can result in both short-term brain injury and long-term functional deficits, making extravascular thrombin an understudied therapeutic target for stroke. This review examines the role of thrombin and PARs in brain injury following hemorrhagic and ischemic stroke and the potential treatment strategies which are complicated by their role in both hemostasis and brain.

Clinical and Radiological Characteristics of Vitamin K Versus Non-Vitamin K Antagonist Oral Anticoagulation-Related Intracerebral Hemorrhage

BACKGROUND/OBJECTIVE

Recent studies indicated that functional outcome after intracranial hemorrhage (ICH) related to direct oral anticoagulation (DOAC-ICH) is similar, if not better, than vitamin K antagonist (VKA)-related ICH (VKA-ICH) due to a smaller initial hematoma volume (HV). However, the association with hematoma expansion (HE) and location is not well understood.

METHODS

We retrospectively analyzed 102 consecutive patients with acute non-traumatic ICH on oral anticoagulation therapy to determine HV and HE stratified by hematoma location, and the relation to the 90-day outcome.

RESULTS

DOAC-ICH (n = 25) and VKA-ICH (n = 77) had a similar admission HV and HE (unadjusted p > 0.05, each). Targeted reversal strategies were used in 93.5% of VKA-ICH versus 8% of DOAC-ICH. After adjustment, an unfavorable 90-day functional outcome (modified Rankin scale score 4-6) was independently associated with a lower admission Glasgow Coma Scale score (OR 1.63; 95% CI 1.26-2.10; p < 0.001) and greater HV (OR 1.03; 95% confidence interval (CI) 1.00-1.05; p = 0.046). After exclusion of patients without follow-up head computed tomography to allow for adjustment by occurrence of HE, VKA-ICH was associated with an approximately 3.5 times greater odds for a poor 90-day outcome (OR 3.64; 95% CI 1.01-13.09; p = 0.048). However, there was no significant association of the oral anticoagulant strategy with 90-day outcome in the entire cohort (OR 2.85; 95% CI 0.69-11.86; p = 0.15).

CONCLUSIONS

DOAC use did not relate to worse HE, HV, and functional outcome after ICH, adding to the notion that DOAC is a safe alternative to VKA even in the absence of access to targeted reversal strategies (which are still not universally available).

The Research Progress of Direct Thrombin Inhibitors

Blood coagulation is the process of changing the blood from the flowing state to the gel state. It is an important part of the hemostatic function. Coagulation is a process by which a series of coagulation factors are sequentially activated, and finally thrombin is formed to form fibrin clot. Direct thrombin inhibitors are important anticoagulant drug. These drugs can selectively bind to the active site of thrombin, inhibit thrombin activity, have strong action and high specificity, and have important significance in the clinical treatment of thrombus diseases. Some of them come from natural products of animals or plants, and many of them have been applied in the clinic. The other part is derived from the design, synthesis and activity studies of small molecule inhibitors. This review discusses the progress of direct thrombin inhibitors in recent years.

Secondary Bleeding During Acute Experimental Intracerebral Hemorrhage

Background and Purpose- Mechanisms contributing to acute hematoma growth in intracerebral hemorrhage are not well understood. Neuropathological studies suggest that the initial hematoma may create mass effect that can tear vessels in the vicinity by shearing, causing further bleeding and hematoma growth. Methods- To test this in mice, we simulated initial intracerebral hemorrhage by intrastriatal injection of a liquid polymer that coagulates upon contact with tissue and measured the presence and volume of bleeding secondary to the mass effect using Hemoglobin ELISA 15 minutes after injection. Results- Secondary hemorrhage occurred in a volume-dependent (4, 7.5, or 15 μL of polymer) and rate-dependent (0.05, 0.5, or 5 μL/s) manner. Anticoagulation (warfarin or dabigatran) exacerbated the secondary hemorrhage volume. In a second model of hematoma expansion, we confirmed that intrastriatal whole blood injection (15 μL, 0.5 μL/s) also caused secondary bleeding, using acute Evans blue extravasation as a surrogate. Anticoagulation once again exacerbated secondary hemorrhage after intrastriatal whole blood injection. Secondary hemorrhage directly and significantly correlated with arterial blood pressures in both nonanticoagulated and anticoagulated mice, when modulated by phenylephrine or labetalol. Conclusions- Our study provides the first proof of concept for secondary vessel rupture and bleeding as a potential mechanism for intracerebral hematoma growth.

Cerebral microbleeds: Beyond the macroscope

While being increasingly recognized in clinical routine, brain microbleeds remain a puzzling finding for physicians. These small dot-like lesions are thought to be old perivascular collections of hemosiderin deposits. They can be found in different neurological settings such as cerebrovascular or neurodegenerative diseases. While their microscopic size would suggest considering these lesions as anecdotal, they are now regarded as biomarkers of severity of an underlying cerebrovascular disease. Their natural history and the interactions with surrounding brain cells remain unknown. However, their presence may impact therapeutic decisions. Deciphering the biological mechanisms leading to, or following microbleeds would enable us to address a key question: do microbleeds arise and impact the surrounding parenchyma like a miniature version of intracerebral hemorrhages or do they represent a different kind of injury? We hereby discuss, based on both clinical and experimental literature, the gap between the definition of microbleeds coming from neuroimaging and the pathophysiological hypotheses raised from histopathological and experimental data. Our analysis supports the need for a convergent effort from clinicians and basic scientists to go beyond the current “macro” view and disclose the cellular and molecular insights of these cerebral hemorrhagic microlesions.

Aspirin treatment does not increase microhemorrhage size in young or aged mice

Microhemorrhages are common in the aging brain and are thought to contribute to cognitive decline and the development of neurodegenerative diseases, such as Alzheimer’s disease. Chronic aspirin therapy is widespread in older individuals and decreases the risk of coronary artery occlusions and stroke. There remains a concern that such aspirin usage may prolong bleeding after a vessel rupture in the brain, leading to larger bleeds that cause more damage to the surrounding tissue. Here, we aimed to understand the influence of aspirin usage on the size of cortical microhemorrhages and explored the impact of age. We used femtosecond laser ablation to rupture arterioles in the cortex of both young (2–5 months old) and aged (18–29 months old) mice dosed on aspirin in their drinking water and measured the extent of penetration of both red blood cells and blood plasma into the surrounding tissue. We found no difference in microhemorrhage size for both young and aged mice dosed on aspirin, as compared to controls (hematoma diameter = 104 +/- 39 (97 +/- 38) μm in controls and 109 +/- 25 (101 +/- 28) μm in aspirin-treated young (aged) mice; mean +/- SD). In contrast, young mice treated with intravenous heparin had an increased hematoma diameter of 136 +/- 44 μm. These data suggest that aspirin does not increase the size of microhemorrhages, supporting the safety of aspirin usage.

Hematoma Expansion Following Intracerebral Hemorrhage: Mechanisms Targeting the Coagulation Cascade and Platelet Activation

Hematoma expansion (HE), defined as a greater than 33% increase in intracerebral hemorrhage (ICH) volume within the first 24 hours, results in significant neurological deficits, and enhancement of ICH-induced primary and secondary brain injury. An escalation in the use of oral anticoagulants has led to a surge in the incidences of oral anticoagulation-associated ICH (OAT-ICH), which has been associated with a greater risk for HE and worse functional outcomes following ICH. The oral anticoagulants in use include vitamin K antagonists, and direct thrombin and factor Xa inhibitors. Fibrinolytic agents are also frequently administered. These all act via differing mechanisms and thus have varying degrees of impact on HE and ICH outcome. Additionally, antiplatelet medications have also been increasingly prescribed, and result in increased bleeding risks and worse outcomes after ICH. Aspirin, thienopyridines, and GPIIb/IIIa receptor blockers are some of the most common agents in use clinically, and also have different effects on ICH and hemorrhage growth, based on their mechanisms of action. Recent studies have found that reduced platelet activity may be more effective in predicting ICH risk, hemorrhage expansion, and outcomes, than antiplatelet agents, and activating platelets may thus be a novel target for ICH therapy. This review explores how dysfunctions or alterations in the coagulation and platelet cascades can lead to, and/or exacerbate, hematoma expansion following intracerebral hemorrhage, and describe the mechanisms behind these effects and the drugs that induce them. We also discuss potential future therapy aimed at increasing platelet activity after ICH.

Dabigatran reduces endothelial permeability through inhibition of thrombin-induced cytoskeleton reorganization

Dabigatran etexilate (DE), a new oral anti-coagulant, is a direct thrombin inhibitor. Clinical trials showed the favorable benefit-to-risk profile of DE compared to warfarin for the prevention of ischemic stroke in patients with atrial fibrillation. Remarkably, patients treated with dabigatran showed reduced rates of intracerebral hemorrhage compared to warfarin. As the breakdown of endothelial barrier integrity is associated with hemorrhagic events and as thrombin increases endothelial permeability, we hypothesized that dabigatran preserves the endothelial barrier by inhibiting thrombin-induced permeability. We assessed leakage of fluorescein isothiocyanate (FITC)-dextran through the endothelial monolayer and measured trans-endothelial electrical resistance of the endothelial monolayer after treatment of thrombin or thrombin pre-incubated with dabigatran. Thrombin increased the permeability of endothelial cells. Dabigatran effectively blocked the ability of thrombin to increase permeability. Dabigatran inhibited the formation of actin stress fibers induced by thrombin and inhibited consequent destabilization of junctional protein complexes and intercellular gap formation. The interaction of thrombin with protease activated receptor-1 activates the Rho A guanosine triphosphate (GTP)ase-myosin light chain (MLC) phosphorylation signaling axis, leading to actin cytoskeleton changes. This signaling pathway was effectively inhibited by dabigatran in endothelial cells. Consistently, the number of phosphorylated MLC-positive cells was significantly decreased in ischemic tissue of rat brains. These results indicate dabigatran blocks the ability of thrombin to induce vascular permeability and the resulting underlying signaling cascade in endothelial cells. Our findings provide evidence that dabigatran may confer a lower risk of intracerebral hemorrhage by preserving endothelial barrier integrity.

Comparing intracerebral hemorrhages associated with direct oral anticoagulants or warfarin

OBJECTIVES

This cross-sectional survey explored the characteristics and outcomes of direct oral anticoagulant (DOAC)-associated nontraumatic intracerebral hemorrhages (ICHs) by analyzing a large nationwide Japanese discharge database.

METHODS

We analyzed data from 2,245 patients who experienced ICHs while taking anticoagulants (DOAC: 227; warfarin: 2,018) and were urgently hospitalized at 621 institutions in Japan between April 2010 and March 2015. We compared the DOAC- and warfarin-treated patients based on their backgrounds, ICH severities, antiplatelet therapies at admission, hematoma removal surgeries, reversal agents, mortality rates, and modified Rankin Scale scores at discharge.

RESULTS

DOAC-associated ICHs were less likely to cause moderately or severely impaired consciousness (DOAC-associated ICHs: 31.3%; warfarin-associated ICHs: 39.4%; p = 0.002) or require surgical removal (DOAC-associated ICHs: 5.3%; warfarin-associated ICHs: 9.9%; p = 0.024) in the univariate analysis. Propensity score analysis revealed that patients with DOAC-associated ICHs also exhibited lower mortality rates within 1 day (odds ratio [OR] 4.96, p = 0.005), within 7 days (OR 2.29, p = 0.037), and during hospitalization (OR 1.96, p = 0.039).

CONCLUSIONS

This nationwide study revealed that DOAC-treated patients had less severe ICHs and lower mortality rates than did warfarin-treated patients, probably due to milder hemorrhages at admission and lower hematoma expansion frequencies.

Anticoagulants inhibit proteolytic clearance of plasma amyloid beta

We recently discovered a plasma proteolysis pathway, termed the FXII-FVII pathway which is composed of coagulation proteases, and found it to be mainly responsible for the clearance of Aβ42 in the plasma in mice. Aβ42 and Aβ40 are the main Aβ forms in Alzheimer’s disease (AD). In the present study, in vitro assays, wild type (WT) mice and J20 mice (a transgenic AD model) are used to assess the degradation of Aβ40 and Aβ42 by the FXII-FVII pathway and the impact of anticoagulants on such degradation. Four clinically available and mechanistically distinct anticoagulants are evaluated, including dabigatran, enoxaparin (EP), rivaroxaban and warfarin. Each anticoagulant significantly elevates plasma level of synthetic Aβ42 in WT mice, among which EP is the most effective. The differential efficacies of the anticoagulants in elevating plasma Aβ42 level match closely with their inhibitory mechanisms towards the FXII-FVII pathway. Plasma Aβ40 is also degraded by the FXII-FVII pathway and is protected by EP. Moreover, the FXII-FVII pathway is significantly activated in J20 mice, but EP inhibits the activation and significantly elevates plasma levels of both Aβ40 and Aβ42. Taken together, our results shed new light on Aβ metabolism, reveal a novel function of anticoagulants, and suggest a novel approach to potentially developing plasma Aβ as an AD biomarker.

Challenges for intraventricular hemorrhage research and emerging therapeutic targets

INTRODUCTION

Intraventricular hemorrhage (IVH) affects both premature infants and adults. In both demographics, it has high mortality and morbidity. There is no FDA approved therapy that improves neurological outcome in either population highlighting the need for additional focus on therapeutic targets and treatments emerging from preclinical studies. Areas covered: IVH induces both initial injury linked to the physical effects of the blood (mass effect) and secondary injury linked to the brain response to the hemorrhage. Preclinical studies have identified multiple secondary injury mechanisms following IVH, and particularly the role of blood components (e.g. hemoglobin, iron, thrombin). This review, with an emphasis on pre-clinical IVH research, highlights therapeutic targets and treatments that may be of use in prevention, acute care, or repair of damage. Expert opinion: An IVH is a potentially devastating event. Progress has been made in elucidating injury mechanisms, but this has still to translate to the clinic. Some pathways involved in injury also have beneficial effects (coagulation cascade/inflammation). A greater understanding of the downstream pathways involved in those pathways may allow therapeutic development. Iron chelation (deferoxamine) is in clinical trial for intracerebral hemorrhage and preclinical data suggest it may be a potential treatment for IVH.

Anticoagulation increases alveolar hemorrhage in mice infected with influenza A

Influenza A virus infection is a common respiratory tract infection. Alveolar hemorrhage has been reported in patients with influenza pneumonia and in mice infected with influenza A. In this study, we investigated the effect of two anticoagulants on alveolar hemorrhage after influenza A virus (IAV) infection of wild‐type mice. Wild‐type mice were anticoagulated with either warfarin or the direct thrombin inhibitor dabigatran etexilate and then infected with a mouse‐adapted influenza virus (A/Puerto Rico/8/34 H1N1). Alveolar hemorrhage was assessed by measuring hemoglobin levels in the bronchoalveolar lavage fluid (BALF). We also measured vascular permeability and viral genomes in the lung, as well as white blood cells, inflammatory mediators, and protein in BALF. Survival and body weight were monitored for 14 days after influenza A infection. In infected mice receiving either warfarin or dabigatran etexilate we observed decreased activation of coagulation in the BALF and increased alveolar hemorrhage. Warfarin but not dabigatran etexilate increased vascular permeability and mortality of influenza A‐infected mice. Anticoagulation did not affect levels of influenza A genomes, white blood cells, inflammatory mediators, or protein in the BALF. Our study indicates that systemic anticoagulation increases alveolar hemorrhage in influenza A‐infected mice.

Dabigatran ameliorates post-haemorrhagic hydrocephalus development after germinal matrix haemorrhage in neonatal rat pups

We aim to determine if direct thrombin inhibition by dabigatran will improve long-term brain morphological and neurofunctional outcomes and if potential therapeutic effects are dependent upon reduced PAR-1 stimulation and consequent mTOR activation. Germinal matrix haemorrhage was induced by stereotaxically injecting 0.3 U type VII-S collagenase into the germinal matrix of P7 rat pups. Animals were divided into five groups: sham, vehicle (5% DMSO), dabigatran intraperitoneal, dabigatran intraperitoneal + TFLLR-NH₂ (PAR-1 agonist) intranasal, SCH79797 (PAR-1 antagonist) intraperitoneal, and dabigatran intranasal. Neurofunctional outcomes were determined by Morris water maze, rotarod, and foot fault evaluations at three weeks. Brain morphological outcomes were determined by histological Nissl staining at four weeks. Expression levels of p-mTOR/p-p70s6k at three days and vitronectin/fibronectin at 28 days were quantified. Intranasal and intraperitoneal dabigatran promoted long-term neurofunctional recovery, improved brain morphological outcomes, and reduced intracranial pressure at four weeks after GMH. PAR-1 stimulation tended to reverse dabigatran's effects on post-haemorrhagic hydrocephalus development. Dabigatran also reduced expression of short-term p-mTOR and long-term extracellular matrix proteins, which tended to be reversed by PAR-1 agonist co-administration. PAR-1 inhibition alone, however, did not achieve the same therapeutic effects as dabigatran administration.

The Severity of Intracranial Hemorrhages Measured by Free Hemoglobin in the Brain Depends on the Anticoagulant Class: Experimental Data

Background and Purpose. Anticoagulant therapy is broadly used to prevent thromboembolic events. Intracranial hemorrhages are serious complications of anticoagulation, especially with warfarin. Direct oral anticoagulants reduce but do not eliminate the risk of intracranial hemorrhages. The aim of this study is to determine the degree of intracranial hemorrhage after application of anticoagulants without additional triggers. Methods. Rats were treated with different anticoagulant classes (vitamin K antagonists, heparin, direct thrombin inhibitor, and factor Xa inhibitor). Brain hemorrhages were assessed by the free hemoglobin concentration in the brain parenchyma. Results. Vitamin K antagonists (warfarin and brodifacoum) significantly increased free hemoglobin in the brain. Among direct oral anticoagulants, thrombin inhibitor dabigatran also significantly increased free hemoglobin in the brain, whereas treatment with factor Xa inhibitor rivaroxaban did not have significant effect on the free hemoglobin concentration. Conclusions. Our data indicates that the severity of brain hemorrhages depends on the anticoagulant class and it is more pronounced with vitamin K antagonists.

Direct Oral Anticoagulants Form Thrombus Different From Warfarin in a Microchip Flow Chamber System

Direct oral anticoagulants (DOACs) have low risk of intracranial hemorrhage compared to warfarin. We sought to clarify the different mechanisms responsible for suppression of bleeding events using the Total Thrombus-formation Analysis System (T-TAS), a flow-microchip chamber with thrombogenic surfaces. Blood samples were obtained at Off- and On-anticoagulant (trough) from 120 consecutive patients with atrial fibrillation (warfarin; n = 29, dabigatran; n = 19, rivaroxaban; n = 47, apixaban; n = 25), which were used for T-TAS to compute the area under the curve (AUC) (AR₁₀-AUC₃₀) in the AR chip, and to measure plasma concentrations of DOACs at On-anticoagulant. In addition, the two-dimensional area covered by thrombi (%) in the capillary was analyzed every 3 minutes after sample applications. The AR₁₀-AUC₃₀ correlated weakly and negatively with plasma concentrations of DOACs, and the levels at On-anticoagulant were lower in all groups than at Off-anticoagulant. AR₁₀-AUC₃₀ levels at Off- and On-anticoagulant were identical among the groups. The thrombi areas in early phase were significantly larger in rivaroxaban and apixaban than warfarin and dabigatran groups. The findings suggested that visual analysis of the AR-chip can identify the differential inhibitory patterns of warfarin and DOACs on thrombus formation under flow condition.

Outcome of intracerebral hemorrhage associated with different oral anticoagulants

Objective:

In an international collaborative multicenter pooled analysis, we compared mortality, functional outcome, intracerebral hemorrhage (ICH) volume, and hematoma expansion (HE) between non–vitamin K antagonist oral anticoagulation–related ICH (NOAC-ICH) and vitamin K antagonist–associated ICH (VKA-ICH).

Methods:

We compared all-cause mortality within 90 days for NOAC-ICH and VKA-ICH using a Cox proportional hazards model adjusted for age; sex; baseline Glasgow Coma Scale score, ICH location, and log volume; intraventricular hemorrhage volume; and intracranial surgery. We addressed heterogeneity using a shared frailty term. Good functional outcome was defined as discharge modified Rankin Scale score ≤2 and investigated in multivariable logistic regression. ICH volume was measured by ABC/2 or a semiautomated planimetric method. HE was defined as an ICH volume increase >33% or >6 mL from baseline within 72 hours.

Results:

We included 500 patients (97 NOAC-ICH and 403 VKA-ICH). Median baseline ICH volume was 14.4 mL (interquartile range [IQR] 3.6–38.4) for NOAC-ICH vs 10.6 mL (IQR 4.0–27.9) for VKA-ICH (p = 0.78). We did not find any difference between NOAC-ICH and VKA-ICH for all-cause mortality within 90 days (33% for NOAC-ICH vs 31% for VKA-ICH [p = 0.64]; adjusted Cox hazard ratio (for NOAC-ICH vs VKA-ICH) 0.93 [95% confidence interval (CI) 0.52–1.64] [p = 0.79]), the rate of HE (NOAC-ICH n = 29/48 [40%] vs VKA-ICH n = 93/140 [34%] [p = 0.45]), or functional outcome at hospital discharge (NOAC-ICH vs VKA-ICH odds ratio 0.47; 95% CI 0.18–1.19 [p = 0.11]).

Conclusions:

In our international collaborative multicenter pooled analysis, baseline ICH volume, hematoma expansion, 90-day mortality, and functional outcome were similar following NOAC-ICH and VKA-ICH.

Volume and Characteristics of Intracerebral Hemorrhage with Direct Oral Anticoagulants in Comparison with Warfarin

Background

Patients undergoing anticoagulation therapy often experience intracerebral hemorrhages (ICHs), and warfarin in particular is known to increase hematoma expansion in ICHs, which results in a poor outcome. Recent studies reported that, in comparison with warfarin, direct oral anticoagulants (DOACs) cause fewer ICHs with better functional outcome. However, since it is still unknown whether DOACs are associated with a smaller hematoma volume of ICHs, we aimed to compare the volume, hematoma expansion, and outcomes associated with ICHs treated with DOACs and warfarin.

Methods

We performed a prospective multicenter cross-sectional study. The subjects included patients with acute ICHs who received either DOACs or warfarin. We evaluated the clinical characteristics, and measured initial and follow-up ICH volumes. The volume of ICHs and hematoma expansion were compared between the DOAC and warfarin groups. Mortality and modified Rankin score at discharge were evaluated as outcomes.

Results

There were 18 patients in the DOAC group and 71 in the warfarin group. The baseline characteristics were similar between the 2 groups. Initial median hematoma volume of ICHs in the DOAC group was significantly lower than that in the warfarin group (6.2 vs. 24.2 mL, respectively; p = 0.04). In cases involving follow-up computed tomography scanning, the median hematoma volume of ICHs at follow-up was lower in the DOAC group than in the warfarin group (initial: DOACs 4.4 vs. warfarin 13.5 mL; follow-up: 5.0 vs. 18.4 mL, respectively; p = 0.05). Further, the hematoma in ICHs associated with DOACs did not expand. Although the mortality of ICHs associated with DOACs (11%) was lower than that associated with warfarin (24%), this difference was not statistically significant. The univariate analysis showed that the anticoagulant type (DOACs vs. warfarin) and sex (male vs. female) were associated with ICH volume. The multivariable linear regression showed that the use of DOACs (compared to warfarin; β: −0.23, p = 0.03) and female sex (compared to male; β: −0.25, p = 0.02) were associated with a small hematoma volume.

Conclusions

Based on the results of the present study, in terms of the risks associated with ICHs, the use of DOACs appears to be safer than warfarin for anticoagulation therapy. Further studies are required to validate these findings.

Risk of long-term anticoagulation under sustained severe arterial hypertension: A translational study comparing warfarin and the new oral anticoagulant apixaban

New oral anticoagulants for the prevention of stroke and systemic embolism in patients with atrial fibrillation have recently been introduced. In this translational study, we explored the risk of long-term anticoagulation on intracerebral hemorrhage under sustained severe arterial hypertension. We initiated anticoagulation with warfarin or apixaban in spontaneously hypertensive rats prone to develop severe hypertension and subsequent intracerebral bleeding complications. A non-anticoagulated group served as control. During an 11-week-study period, blood pressure, anticoagulation parameters, and clinical status were determined regularly. The incidence of histopathologically proven intracerebral hemorrhage was defined as the primary endpoint. Both warfarin and apixaban anticoagulation was fairly stable during the study period, and all rats developed severe hypertension. Intracerebral hemorrhage was determined in 29% (4/14) of warfarin rats and in 10% (1/10) of apixaban rats. Controls did not show cerebral bleeding complications (chi-square not significant). Mortality rate at study termination was 33% (2/6) in controls, 43% (6/14) in the warfarin group, and 60% (6/10) in the apixaban group. Animals died from extracerebral complications in most cases. Our study describes an experimental intracerebral hemorrhage model in the context of sustained hypertension and long-term anticoagulation. Extracerebral bleeding complications occurred more often in warfarin-treated animals compared with apixaban and control rats.

[Direct oral anticoagulants and acute stroke : Insights into translational research studies]

In recent years a considerable number of translational research studies on intracerebral hemorrhage and ischemic stroke have been published, which are characterized by a particular proximity to practical clinical questions. Animal research has provided insights into the pathophysiological processes and therapy effects, which have so far only been insufficiently investigated in clinical studies. This includes the effectiveness of a rapid reversal of anticoagulation in cases of anticoagulation-associated intracerebral hemorrhage and the safety of thrombolytic treatment in ischemic stroke occurring during treatment with anticoagulants. With the approval of the direct oral anticoagulants these problems have become of particular contemporary relevance. Of course, results from experimental translational studies on stroke cannot be directly translated into clinical routine. Nevertheless, these investigations help to understand the underlying processes and mechanisms and provide proof of concept data for new treatment strategies. This review summarizes the most relevant results in this field of research with a particular focus on practical clinical questions.

Clinical and radiological course of intracerebral haemorrhage associated with the new non-vitamin K anticoagulants

BACKGROUND

Clinical outcome and mortality in intracerebral haemorrhage (ICH) associated with anticoagulant treatment is poor. Novel direct oral anticoagulant drugs (NOACs) are increasingly prescribed. Management of NOAC-associated ICH might be more challenging. The aim of this study was to compare the clinical and radiological course of ICH patients being treated with different forms of oral anticoagulant drugs.

METHOD

The study is a retrospective observational study. Haemorrhage in other intracranial compartments except the ventricular system were explicitly excluded. Four groups were categorised and compared with regard to their clinical and radiological course (NOACs, vitamin K antagonists [VKAs], platelet inhibitors and patients without anticoagulant/antiplatelet drugs). Clinical as well as radiological parameters were analysed.

RESULTS

Overall, 182 patients were included (2011 to early 2016). Twenty-five patients with NOAC-associated ICH were included (47 with VKAs, 50 with platelet inhibitors and 60 patients without anticoagulant/antiplatelet drugs). The frequency of NOAC-associated ICH increased over the years. Diabetes was found significantly more often in the NOAC patients (p = 0.05). The clinical and radiological courses in the three different patient groups with impaired coagulation were similar. Mortality was significantly higher in patient groups with impaired coagulation (p = 0.04) compared to those without anticoagulant/antiplatelet drugs. Multivariate analysis revealed the Glasgow Coma Scale (GCS) score as a strong predictor for worse outcome and mortality.

CONCLUSIONS

The frequency of NOAC-associated ICH increased in the last 5 years. Diabetes might be a risk factor for ICH when receiving NOACs. Clinical outcome in NOAC-associated ICH is poor and mortality is as high as in patients with other oral anticoagulant/antiplatelet drugs.

Intracerebral Hemorrhage: Perihemorrhagic Edema and Secondary Hematoma Expansion: From Bench Work to Ongoing Controversies

Intracerebral hemorrhage (ICH) is a medical emergency, which often leads to severe disability and death. ICH-related poor outcomes are due to primary injury causing structural damage and mass effect and secondary injury in the perihemorrhagic region over several days to weeks. Secondary injury after ICH can be due to hematoma expansion (HE) or a consequence of repair pathway along the continuum of neuroinflammation, neuronal death, and perihemorrhagic edema (PHE). This review article is focused on PHE and HE and will cover the animal studies, related human studies, and clinical trials relating to these mechanisms of secondary brain injury in ICH patients.

Targeting Secondary Hematoma Expansion in Spontaneous Intracerebral Hemorrhage - State of the Art

Spontaneous intracerebral hemorrhage (SICH), defined broadly as intracerebral hemorrhage not related to trauma, results in long-term disability or death in a large proportion of afflicted patients. Current management of this disease is predominantly supportive, including airway protection, optimization of hemodynamic parameters, and management of intracranial pressure. No active treatments that demonstrate beneficial effects on clinical outcome are currently available. Animal models of SICH have allowed for the elucidation of multiple pathways that may be attractive therapeutic targets. A minority of these, such as aggressive blood pressure management and recombinant activated factor VII administration, have led to large-scale clinical trials. There remains a critical need for further translational research in the realm of SICH.

Treatment with FTY720 has no beneficial effects on short-term outcome in an experimental model of intracerebral hemorrhage

BACKGROUND

No evidence-based therapy is available for patients with acute intracerebral hemorrhage (ICH). In view of the profound inflammatory reaction in the perilesional tissue, we investigated in a well-characterized experimental model whether the administration of the immunomodulator fingolimod (FTY720) is neuroprotective in acute ICH.

METHODS

ICH was induced by means of a stereotactic intrastriatal injection of collagenase type VII-S. FTY720 (1 mg/kg) was administered intraperitoneally 1 h after ICH induction. Hematoma volume was assessed spectrophotometrically at 24 h after ICH induction. The following endpoints were determined at 24 and 72 h, respectively: mortality rate and neurologic outcomes, edema formation, and MMP-9 activity.

RESULTS

Twenty-four hour after ICH induction, hematoma volume was not statistically different between groups. No difference was found in mortality and neurologic outcomes at 24 and 72 h between FTY720 treated mice and controls. Edema formation was present in both groups on the ipsilateral side with no statistical difference between groups at both time points. No difference was found in MMP-9 levels after 24 and 72 h between groups.

CONCLUSIONS

Our results suggest that FTY720 has no beneficial effects in the acute phase of experimental ICH.

Anticoagulation Therapy in Traumatic Brain Injury

BACKGROUND

Optimal anticoagulation therapy (AT) in patients with traumatic brain injury (TBI) is a challenging task and proper management is strongly correlated with clinical outcomes. Only limited data are available on AT after TBI and practical decision making is based on the opinion of experts. This review sought to critically assess different therapeutic options using AT and antiplatelet agents in the perioperative period after TBI.

METHODS

A comprehensive review of the literature was performed to summarize relevant data on AT in patients with TBI.

RESULTS

Patients with preinjury AT with TBI require emergent neurosurgical treatment and they are also at high risk of developing thromboembolic complications or hematoma expansion. New oral anticoagulants offer a lower incidence of intracranial hemorrhage compared with warfarin. The rate of intracranial hemorrhage during new oral anticoagulants or heparin therapy is significantly lower than that with vitamin K antagonists.

Volume and functional outcome of intracerebral hemorrhage according to oral anticoagulant type

OBJECTIVE

To compare intracerebral hemorrhage (ICH) volume and clinical outcome of non-vitamin K oral anticoagulants (NOAC)-associated ICH to warfarin-associated ICH.

METHODS

In this multicenter cross-sectional observational study of patients with anticoagulant-associated ICH, consecutive patients with NOAC-ICH were compared to those with warfarin-ICH selected from a population of 344 patients with anticoagulant-associated ICH. ICH volume was measured by an observer blinded to clinical details. Outcome measures were ICH volume and clinical outcome adjusted for confounding factors.

RESULTS

We compared 11 patients with NOAC-ICH to 52 patients with warfarin-ICH. The median ICH volume was 2.4 mL (interquartile range [IQR] 0.3-5.4 mL) for NOAC-ICH vs 8.9 mL (IQR 4.0-21.3 mL) for warfarin-ICH (p = 0.0028). In univariate linear regression, use of warfarin (difference in cube root volume 1.61; 95% confidence interval [CI] 0.69 to 2.53) and lobar ICH location (compared with nonlobar ICH; difference in cube root volume 1.52; 95% CI 2.20 to 0.85) were associated with larger ICH volumes. In multivariable linear regression adjusting for confounding factors (sex, hypertension, previous ischemic stroke, white matter disease burden, and premorbid modified Rankin Scale score [mRS]), warfarin use remained independently associated with larger ICH (cube root) volumes (coefficient 0.64; 95% CI 0.24 to 1.25; p = 0.042). Ordered logistic regression showed an increased odds of a worse clinical outcome (as measured by discharge mRS) in warfarin-ICH compared with NOAC-ICH: odds ratio 4.46 (95% CI 1.10 to 18.14; p = 0.037).

CONCLUSIONS

In this small prospective observational study, patients with NOAC-associated ICH had smaller ICH volumes and better clinical outcomes compared with warfarin-associated ICH.

Oral anticoagulant therapy in atrial fibrillation patients at high stroke and bleeding risk

Atrial fibrillation (AF) is associated with a 5-fold greater risk of ischemic stroke or systemic embolism compared with normal sinus rhythm. Cardioembolic AF-related strokes are often more severe, fatal or associated with greater permanent disability and higher recurrence rates than strokes of other aetiologies. These strokes may be effectively prevented with oral anticoagulant (OAC) therapy, using either vitamin K antagonists (VKAs) or non-vitamin K antagonist OACs (NOACs) such as the direct thrombin inhibitor dabigatran or direct factor Xa inhibitors rivaroxaban, apixaban or edoxaban. Most AF patients have a positive net clinical benefit from OAC, excluding those with AF and no conventional stroke risk factors. Balancing the risks of stroke and bleeding is necessary for optimal use of OAC in clinical practice, and modifiable bleeding risk factors must be addressed. Concerns remain over 'non-changeable' bleeding risk factors such as older age, significant renal or hepatic impairment, prior stroke(s) or prior bleeding event(s) and active malignancies. Such AF patients are often termed 'special' AF populations, due to their 'special' risk profile that includes increased risks of both thromboembolic and bleeding events, and due to fear of bleeding complications these AF patients are often denied OAC. Evidence shows, however, that the absolute benefits of OAC are the greatest in patients at the highest risk, and NOACs may offer even a greater net clinical benefit compared to warfarin particularly in these high risk patients. In this review article, we summarize available data on stroke prevention in AF patients at increased risk of both stroke and bleeding and discuss the use of NOACs for thromboprophylaxis in these 'special' AF populations.

Intracranial bleedings in patients on long-term anticoagulant treatment: Benefits from oral thrombin and factor Xa inhibitors in clinical practice

Dabigatran, a direct thrombin inhibitor and activated factor X inhibitors, rivaroxaban and apixaban, used in the prevention of stroke or systemic embolism in patients with nonvalvular atrial fibrillation (AF), have several advantages over vitamin K antagonists (VKAs). The non-vitamin K oral anticoagulants (NOACs) have been shown to reduce the risk of intracranial bleedings by 50%. The current review summarizes the available data on the epidemiology, mechanisms and treatment of intracranial bleedings observed on oral anticoagulation with the focus on the specificity of NOACs in this context.

Organ-specific bleeding patterns of anticoagulant therapy: lessons from clinical trials

Anticoagulants are effective at preventing and treating thrombosis, but can cause bleeding. For decades, vitamin K antagonists (VKAs) have been the only available oral anticoagulants. The development of non-VKA oral anticoagulants (NOACs), which inhibit either factor Xa or thrombin stoichiometrically, has provided alternatives to VKAs for several indications. The results of recent large-scale randomised controlled trials comparing NOACs with VKAs for the prevention of stroke in patients with non-valvular atrial fibrillation (AF) have produced some unexpected results. As a group, NOACs showed similar efficacy as warfarin, but a reduced risk of major bleeding. The reduction in bleeding with NOACs was greatest with intracranial hemorrhage. In contrast, the relative risk of gastro-intestinal bleeding was increased with some NOACs. In this review, we explore the potential mechanisms as well as the implications of these organ-specific bleeding patterns.

[Hemorrhagic stroke and new oral anticoagulants]

The recent release of new oral anticoagulants (NOAC) raises the question of the management of intracranial hemorrhage occurring during treatment with these molecules. Dabigatran, rivaroxaban and apixaban have different pharmacological characteristics that physicians need to know to adjust their prescription to each patient. Studies of efficacy and safety prior to the marketing of these molecules showed a decreased risk of intracranial hemorrhage compared with vitamin K antagonists. However, no reliable data are available regarding the prognosis of these hemorrhages occurring during NOAC treatment. In addition, there is no specific antidote and reversal protocol validated in humans. So, physicians are in a difficult situation when critical bleeding occurs. The timing of recovering normal hemostatic capacity is then a determinant factor of prognosis. Studies in animals or healthy volunteers showed a correction of the biological parameters using prothrombin complex concentrates activated or not, without reducing the volume of hematoma. On this basis, proposals have been issued by the french group of interest for perioperative hemostasis (GIHP) for the management of bleeding under NOAC treatment, which include management of intracranial hemorrhage.

Intracranial hemorrhage mortality in atrial fibrillation patients treated with dabigatran or warfarin

BACKGROUND AND PURPOSE

In randomized trials, patients with atrial fibrillation (AF) receiving dabigatran, a direct oral anticoagulant, had lower risk of intracranial bleeding (ICB) than those on warfarin. However, concerns exist about potential worse outcomes in dabigatran users if bleeding occurs, given the lack of approved reversal agents. Thus, we examined in-hospital mortality in AF patients with ICB being treated with dabigatran versus warfarin in a real-world population in the United States.

METHODS

We analyzed healthcare utilization claims in the Truven Health Marketscan Research Databases. The study sample included patients with AF admitted to a hospital with a primary diagnosis of ICB. Information on medications, inpatient, and outpatient diagnoses was obtained from available claims. Propensity score-adjusted risk ratios and 95% confidence intervals of in-hospital mortality comparing current users of dabigatran versus warfarin were estimated using relative risk regression.

RESULTS

Among 2391 AF patients admitted with ICB (2290 on warfarin, 101 on dabigatran), 531 died during their admission. In-hospital mortality was similar in those treated with warfarin (22%) or dabigatran (20%). Compared with warfarin users, the propensity score-adjusted risk ratio (95% confidence interval) of mortality in dabigatran users was 0.93 (0.62-1.37). Associations were similar across different ICB subtypes (intracerebral hemorrhage, subarachnoid hemorrhage, and subdural hematoma).

CONCLUSIONS

In this sample of AF patients with ICB on oral anticoagulants, dabigatran was not associated with higher in-hospital mortality compared with warfarin. Hence, reluctance to use dabigatran because of a lack of approved reversal agents is not supported by our results.

Neuroprotective effects of argatroban and C5a receptor antagonist (PMX53) following intracerebral haemorrhage

Intracerebral haemorrhage (ICH) is a subtype of stroke that associated with neurological dysfunction and inflammation, which may be ameliorated by a neuroprotective strategy targeting the complement cascade. The protective effect of C5a-receptor antagonist (PMX53) solely and in combination with thrombin antagonist (argatroban) was investigated in the ICH mouse model, respectively. Adult male C57BL/6J wild-type (WT) mice and C3(-/-) mice were randomized to receive PMX53/argatroban 1, 3 and 5 days after ICH. A double injection technique was used to infuse 25 μl of autologous whole blood into the right striatum. Mice in the sham group received only needle insertion. Brain water content and mRNA of inflammatory factors were measured on the first, third and fifth days after ICH, respectively. Neurological dysfunction was assessed using a 28-point neurological scoring system in the three cohorts, namely, on days 1, 3 and 5 following ICH. Animals treated with PMX53/argatroban demonstrated significant improvements in neurological function and fewer neurological apoptosis detected by TUNEL [terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labelling] and βIII-tubulin dual-staining compared with vehicle-treated animals. Compared with sham-treated mice, the brain water content in argatroban/PMX53-treated mice was decreased significantly in both the ipsilateral cortex and ipsilateral striatum. Administration of PMX53/argatroban provided a synergistic neuroprotective effect via reducing inflammatory factors and brain oedema, leading to improvements in neurofunctional outcome. The results of this study indicated that simultaneous blockade of the thrombin and C5a receptors represent a promising neuroprotective strategy in haemorrhagic stroke.

Translational insights into traumatic brain injury occurring during dabigatran or warfarin anticoagulation

To date, only limited data are available on the effects of pretreatment with novel oral anticoagulants in the event of traumatic brain injury (TBI). We determined intracerebral hemorrhage volume and functional outcome in a standardized TBI model in mice treated with warfarin or dabigatran. Additionally, we investigated whether excess concentrations of dabigatran could increase bleeding and whether this was preventable by using prothrombin complex concentrate (PCC). C57 mice were treated orally with warfarin or dabigatran; sham-treated mice served as controls. Effective anticoagulation was verified by measurement of international normalized ratio and diluted thrombin time, and TBI was induced by controlled cortical impact (CCI). Twenty-four hours after CCI, intracerebral hemorrhage volume was larger in warfarin-pretreated mice than in controls (10.1 ± 4.9 vs 4.1 ± 1.7 μL; analysis of variance post hoc P=0.001), but no difference was found between controls and dabigatran-pretreated mice (5.3 ± 1.5 μL). PCC applied 30 minutes after CCI did not reliably reduce intracerebral hemorrhage induced by excess dabigatran concentration compared with saline (10.4 ± 11.2 vs 8.7 ± 7.1 μL). Our data suggest pathophysiological differences in TBI occurring during warfarin and dabigatran anticoagulation. The reduced hemorrhage formation under dabigatran therapy could present a safety advantage compared with warfarin. An excess dabigatran concentration, however, can increase hemorrhage.

Intracranial hemorrhage during dabigatran treatment

BACKGROUND

The incidence of intracranial bleeding during dabigatran treatment is lower than that during warfarin treatment. The characteristics of intracranial hemorrhage during dabigatran therapy, however, remain unclear.

METHODS AND RESULTS

The clinical data and treatment summaries of 9 intracranial bleeds that developed during dabigatran treatment in 8 patients with non-valvular atrial fibrillation were retrospectively reviewed. Five patients had small-moderate subdural hematomas, 2 had intracerebral hemorrhage and 1 had traumatic subarachnoid and parenchymal hemorrhage associated with cerebral contusion. Activated partial thromboplastin time upon admission ranged from 31.6 to 72.4s. After admission, systolic blood pressure in the 2 patients with intracerebral hemorrhage was maintained below 140 mmHg, and the subdural hematomas in 4 patients were surgically treated. None of the hematomas became enlarged and outcome was good in most cases.

CONCLUSIONS

Hematomas that arise due to acute intracranial bleeding during dabigatran treatment seem to remain small to moderate, hard to expand, and manageable.

Blood-spinal cord barrier disruption contributes to early motor-neuron degeneration in ALS-model mice

Humans with ALS and transgenic rodents expressing ALS-associated superoxide dismutase (SOD1) mutations develop spontaneous blood-spinal cord barrier (BSCB) breakdown, causing microvascular spinal-cord lesions. The role of BSCB breakdown in ALS disease pathogenesis in humans and mice remains, however, unclear, although chronic blood-brain barrier opening has been shown to facilitate accumulation of toxic blood-derived products in the central nervous system, resulting in secondary neurodegenerative changes. By repairing the BSCB and/or removing the BSCB-derived injurious stimuli, we now identify that accumulation of blood-derived neurotoxic hemoglobin and iron in the spinal cord leads to early motor-neuron degeneration in SOD1(G93A) mice at least in part through iron-dependent oxidant stress. Using spontaneous or warfarin-accelerated microvascular lesions, motor-neuron dysfunction and injury were found to be proportional to the degree of BSCB disruption at early disease stages in SOD1(G93A) mice. Early treatment with an activated protein C analog restored BSCB integrity that developed from spontaneous or warfarin-accelerated microvascular lesions in SOD1(G93A) mice and eliminated neurotoxic hemoglobin and iron deposits. Restoration of BSCB integrity delayed onset of motor-neuron impairment and degeneration. Early chelation of blood-derived iron and antioxidant treatment mitigated early motor-neuronal injury. Our data suggest that BSCB breakdown contributes to early motor-neuron degeneration in ALS mice and that restoring BSCB integrity during an early disease phase retards the disease process.

Comparison of the effect of edoxaban, a direct factor Xa inhibitor, with a direct thrombin inhibitor, melagatran, and heparin on intracerebral hemorrhage induced by collagenase in rats

INTRODUCTION

Intracerebral hemorrhage (ICH) is a major clinical concern with anticoagulation therapy. The effect of a new oral direct FXa inhibitor, edoxaban, was determined in a rat model of ICH and compared with a direct thrombin inhibitor, melagatran, and heparin.

METHODS

To induce ICH, 0.1 U collagenase type VII was injected into the striatum of male Wistar rats under anesthesia with thiopental or halothane. Immediately after ICH induction, edoxaban, melagatran, or heparin were infused intravenously. Five hours after ICH induction, the brain was removed and ICH size was measured. To estimate the margin of safety, antithrombotic effects were evaluated in a rat venous thrombosis model.

RESULTS

Edoxaban at 6mg/kg/h significantly increased ICH volume (1.8-fold) and prolonged prothrombin time (PT) 2.8-fold compared to the vehicle group. No deaths were observed with edoxaban. Melagatran at 1mg/kg/h increased ICH volume at 1mg/kg/h (2.8-fold) with 6.1-fold PT prolongation. At 3mg/kg/h, all rats died due to severe ICH (3.9-fold). Heparin at both 100 and 500U/kg/h significantly increased ICH. At 500U/kg/h, 5 out of 8 rats died. The doses required for 50% inhibition of thrombosis of edoxaban, melagatran, and heparin were 0.045mg/kg/h, 0.14mg/kg/h, and 55U/kg/h, respectively. The safety margins between antithrombotic and ICH exacerbation effects of these anticoagulants were 133, 7.1, and 1.8, respectively.

CONCLUSION

The safety margin of edoxaban was wider than that of melagatran or heparin. These results suggest that edoxaban may be preferable from the perspective of ICH exacerbation risk.

Imaging of contrast medium extravasation in anticoagulation-associated intracerebral hemorrhage with dual-energy computed tomography

BACKGROUND AND PURPOSE

Contrast medium extravasation (CE) in intracerebral hemorrhage (ICH) is a marker of ongoing bleeding and a predictor of hematoma expansion. The aims of the study were to establish an ICH model in which CE can be quantified, characterized in ICH during warfarin and dabigatran anticoagulation, and to evaluate effects of prothrombin complex concentrates on CE in warfarin-associated ICH.

METHODS

CD1-mice were pretreated orally with warfarin, dabigatran, or vehicle. Prothrombin complex concentrates were administered in a subgroup of warfarin-treated mice. ICH was induced by stereotactic injection of collagenase VIIs into the right striatum. Contrast agent (350 μL Isovue 370 mg/mL) was injected intravenously after ICH induction (2-3.5 hours). Thirty minutes later, mice were euthanized, and CE was measured by quantifying the iodine content in the hematoma using dual-energy computed tomography.

RESULTS

The optimal time point for contrast injection was found to be 3 hours after ICH induction, allowing detection of both an increase and a decrease of CE using dual-energy computed tomography. CE was higher in the warfarin group compared with the controls (P=0.002). There was no significant difference in CE between dabigatran-treated mice and controls. CE was higher in the sham-treated warfarin group than in the prothrombin complex concentrates-treated warfarin group (P<0.001).

CONCLUSIONS

Dual-energy computed tomography allows quantifying CE, as a marker of ongoing bleeding, in a model of anticoagulation-associated ICH. Dabigatran induces less CE in ICH than warfarin and consequently reduces risks of hematoma expansion. This constitutes a potential safety advantage of dabigatran over warfarin. Nevertheless, in case of warfarin anticoagulation, prothrombin complex concentrates reduce this side effect.