Abrupt oxygen decrease influences thrombosis and bleeding in stenosed and endothelium-injured rabbit carotid arteries.

BACKGROUND AND OBJECTIVE: Blood oxygen concentration decrease may be associated with haemostatic impairments. We aimed to study the effect of oxygen decrease in a rabbit model of thrombosis and bleeding. METHODS: A total of 44 rabbits were anaesthetized, ventilated and monitored for blood pressure, blood arterial gas, temperature and carotid blood flow. The Folts model was used: a stenosis (75%) and an injury were carried out on the carotid artery, inducing thrombosis. Blood flow decreased as thrombus size increased until the pressure gradient was such that the thrombus was released and local arterial blood flow was suddenly restored. This is known as a cyclic flow reduction. After counting baseline cyclic flow reductions during a 20-min period (P1), rabbits were randomized blindly to one of three groups: hyperoxic, FiO2=100%; normoxic, FiO2 was decreased to obtain a PaO2 between 80 and 120 mmHg; hypoxic, PaO2 < 80 mmHg. Then CFRs were recorded over a second 20-min period (P2). At the end of the experiment, a hepatosplenic section was done and the amount of blood loss was recorded. After each period, the following parameters were measured: blood gas, ear-immersion bleeding time, haemoglobin, platelet count, prothrombin time, activated partial thromboplastin time and fibrinogen. RESULTS: Oxygen decrease during hypoxic and normoxic periods was associated with a decrease in cyclic flow reductions. Bleeding time increased in the hypoxic group unless hepatosplenic bleeding remained stable. A slight increase in activated partial thromboplastin time was observed in the normoxic and hypoxic groups. CONCLUSION: An abrupt decrease in oxygen administration was responsible for an antithrombotic effect. Increase in bleeding time occurred during hypoxia. No clinically relevant variation of any haemostasis parameters was observed.

[Vitamine K antagonists overdose: Physician adherence to the French guidelines]. / Surdosages en antivitamines K : audit de la prise en charge hospitalière.

INTRODUCTION: Vitamin K antagonists (VKA) are drugs with a major risk of side effect. Guidelines have been published in 2008 by the Haute Autorité de santé (HAS) concerning the management of an excessively elevated INR ratio. Our research aimed to assess physicians' adherence to those guidelines. METHODS: We realized a retrospective, multicentric study. One hundred and ten cases of excessively elevated INR ratio were identified and analyzed. RESULTS: Overall physicians adherence was 58%. However, patients with the most elevated INR, i.e., INR>6, were treated according to guidelines in only 33% of the cases. The use of vitamin K was the major source of mistakes. The rate of mortality was 20%. CONCLUSION: Adherence to HAS guidelines seems finally limited. It is necessary to put in place procedures to secure the behavior of physicians.

Recombinant activated factor VII efficacy and safety in a model of bleeding and thrombosis in hypothermic rabbits: a blind study.

BACKGROUND: Recombinant activated factor VII (rFVIIa) is increasingly used to secure hemostasis in hemorrhagic situations in trauma and surgical patients. Hypothermia is often observed in these clinical settings. OBJECTIVE: To study the efficacy and safety of rFVIIa in hypothermia in a rabbit model of bleeding and thrombosis. METHODS: Sixty-nine rabbits were anesthetized, ventilated and monitored for blood pressure, temperature and carotid flow. The Folts model was used: a stenosis (75%) and an injury were carried out on the carotid artery, inducing thrombosis. Blood flow decreased as thrombus size increased until the pressure gradient was such that the thrombus was released and local arterial blood flow was suddenly restored. This is known as a cyclic flow reduction (CFR). After counting baseline CFRs during a 20-min period (P1), rabbits were randomized blindly to one of four groups: normothermic (NT) placebo or rFVIIa (150 microg kg(-1)), hypothermic (HT) (34 degrees C) placebo or rFVIIa. Then CFRs were recorded over a second period (P2). At the end of the experiment, a hepato-splenic section was performed and the amount of blood loss was recorded. After each period, the following were measured: ear immersion bleeding time (BT), hemoglobin, platelet count, prothrombin time (PT), activated partial thromboplastin time (aPTT) and fibrinogen. RESULTS: Hypothermia increased BT and blood loss. These effects were reversed by rFVIIa. In NT rabbits, rFVIIa shortened BT but did not reduce blood loss. rFVIIa-treated rabbits bled similarly regardless of temperature. The incidence of CFRs was higher in treated than placebo animals regardless of temperature. rFVIIa decreased PT and aPTT without modifying platelet count or fibrinogen level. CONCLUSION: Hemostatic efficacy of rFVIIa was maintained in hypothermia. However, the number of CFRs was higher in the rFVIIa-treated group than in the placebo groups, whether for NT or HT rabbits.

[Digestive surgery and varicose vein surgery]. / Chirurgie digestive et varices.

The thromboembolic risk related to surgery may be considered as low for varicose vein surgery and non major digestive surgery. It could be defined as moderate in case of large dissection, long duration of procedures and emergency cases. The risk may be considered as high for major abdominal surgery involving cancer surgery or not and bariatric surgery. The absence of prophylaxis can be proposed for low risk surgery (grade B). However, elastic compression stocking are effective for all cases of digestive surgery and suggested to be used (grade A). There are no data concerning the moderate risk situation. Therefore, experts recommend the use of elastic compression stockings or low doses of LMWH (grade D). High-risk surgery requires the use of high doses of LMWH recommended for reasons of efficacy, tolerance, and easiness to use (grade A). Associated elastic stockings is efficious (grade B). The duration of prophylaxis lasts generally 7-10 days. Extension to 1 month is recommended for major abdominal cancer surgery (grade A).

Morphological and kinetic abnormalities of platelets in hypercholesterolemic rabbits.

Hypercholesterolemia (HC = hypercholesterolemia or hypercholesterolemic) was produced in rabbits by feeding them diets supplemented with cholesterol and peanut oil. Platelet counts and volumes, white cell counts, reticulocyte counts, and hematocrits were determined at intervals for 8-12 weeks in blood from HC animals and controls on a normal rabbit diet. Microthrombocytosis was a consistent occurrence in the presence of HC, developing as early as 2 weeks into the diet. Microthrombocytosis was generally associated with normal platelet counts, but mild thrombocytosis occurred late in the diet at the time of the highest levels of serum cholesterol (greater than 1300 mg/dl). Platelets from HC rabbits were morphologically normal by transmission electron microscopy. Survivals of 51Cr-labeled platelets from HC and non-HC rabbits were measured in HC and non-HC recipients. The results identified an intrinsic defect in the ability of HC platelets to survive in the circulation. They also confirmed previous findings of an environmental defect in HC that causes shortened platelet survival.

Comparative arterial antithrombotic activity of clopidogrel and acetyl salicylic acid in the pig.

We investigated the comparative antithrombotic properties of clopidogrel, an analogue of ticlopidine, and aspirin, using the Folts' model on femoral arteries in 22 pigs. On each animal, clopidogrel or aspirin were used to treat the thrombotic process on the left femoral artery and to prevent this process on the right femoral artery. Sequentially: an injury and stenosis were carried out on the left femoral artery; the thrombotic process was monitored with a Doppler during a 30-min observation period for cyclic flow reductions or permanent cessation of flow; after the first cyclic flow reduction occurred, clopidogrel (5 mg kg-1) or aspirin (2.5, 5, 100 mg kg-1) were injected intravenously; if cyclic flow reductions were abolished, epinephrine (0.4 micrograms kg-1 min-1) was injected to try to restore cyclic flow reductions and/or permanent cessation of flow; then injury and stenosis were applied on the right femoral artery. Before and after injection of clopidogrel or aspirin, ear immersion bleeding times and ex-vivo platelet aggregation were performed. Clopidogrel (n = 7) abolished cyclic flow reductions were efficiently prevented, even for two injuries. Basal bleeding time (5 min 28) was lengthened (> 15 min, 30 min after clopidogrel and remained prolonged even after 24 h). ADP-induced platelet aggregation was inhibited (more than 78%). Comparatively, aspirin had a moderate and no dose-dependent effect. Aspirin 2.5 mg kg-1 (n = 6) abolished cyclic flow reductions in 2 animals, CFR reoccurred spontaneously in one animal and epinephrine restored it in a second animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Aprotinin could promote arterial thrombosis in pigs: a prospective randomized, blind study.

Haemostatic properties of aprotinin could be associated with an increased risk of thrombosis. A randomized, blinded study was conducted to consider the potential thrombogenicity of aprotinin, using the Folts' model on femoral arteries in 12 pigs. The flow variations were measured by a pulsed Doppler in anaesthetised animals. Ear immersion bleeding time was performed. During the first part of the study, a stenosis was performed successively on both femoral arteries, each for a period of 30 min, without prior injury, to assess the integrity of the vessel, and to check that the arteries did not develop cyclic flow reductions (CFR), permanent cessation of flow (PCF) or partial thrombosis, when a stenosis is applied. Then the clamp was released and a bolus of placebo (saline), or aprotinin (4 millions KIU, followed by a continuous infusion of 1 million KIU.h-1), was administered. At the end of the bolus, the second part of the study began. Stenosis was applied to the arteries. If CRF, PCF, or partial thrombosis were observed without prior injury then the infused drug (aprotinin or saline) was considered a prothrombotic drug, and the opposite artery was studied. For each animal, right and left femoral artery segments were fixed and studied (morphologic study). Eighteen arteries were studied. In the aprotinin group, 6 arteries out of 8 developed an unexpected thrombosis, as compared with only 2 out of 10 arteries in the control group (p = 0.02). The morphologic study confirmed the occurrence of thrombosis in 4 out of 7 arteries in the aprotinin group, as compared with only 1 out of 9 in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

How does ticlopidine treatment lower plasma fibrinogen?

Many clinical studies have evaluated the clinical efficiency of ticlopidine in vascular pathology and in few of these studies the plasma Fg level was determined as a biological parameter and not a primary end point. All these studies are heterogeneous because plasma Fg concentration have been measured using various methods, patients were included at various time after the acute event and were followed over a period of 1 to 24 months of treatment with ticlopidine, patients suffered from various pathology: peripheral arterial disease, cerebrovascular disease, diabetes or polycythemia vera. Despite the heterogeneity of these prospective studies, a general trend indicates a decrease in the plasma Fg levels by 10 to 25% with ticlopidine compared to placebo. This decrease in circulating Fg was associated with clinical improvement, and, when studied, hemorheological modifications (decreases in whole blood and plasma viscosities). The mechanism of ticlopidine action is discussed.

Platelet membrane glycoproteins and platelet functions during storage in the presence of a proteinase inhibitor.

The effect of the proteinase inhibitor aprotinin on membrane glycoproteins and functions of platelets stored for 5 days in platelet-rich plasma was tested. Platelet membrane glycoprotein content was determined by flow cytometry or immunoblot techniques using different monoclonal antibodies. ADP- and ristocetin-induced platelet aggregation and adhesion to collagen were tested in parallel. Using the flow-cytometry technique i) a progressive decrease in the percentage of platelets reacting with the different monoclonal antibodies was observed during storage ii) a 30% reduction of the GPIb mean fluorescence intensity (MFI) was observed after 5 days storage while the MFI of the GP IIb-IIIa complex was not modified. Using the immunoblot technique, a decrease in the amount of both the GPIb alpha and the component of Mr 100,000 was observed, while a 50,000 Mr fragment appeared progressively. Platelet adhesion and aggregation were reduced after 24 hours of storage. Aprotinin prevented neither the GPIb alpha reduction nor the modifications of the functions of human platelets stored in their autologous plasma.

Risk factors and outcomes for atherothrombotic disease in French patients: the RIVAGE study. RIsque VAsculaire Group d'Etude.

This prospective observational study was designed to delineate the course of atherosclerotic disease in a representative group of French patients receiving standard medical care and to look for clinical and laboratory factors predictive of recurrent cardiovascular events. The 2416 study patients (75.2% men and 24.8% women) had diagnoses of peripheral arterial disease (stage II or III), ischemic heart disease (stable angina or myocardial infarction), or cerebrovascular disease (transient ischemic attack or stroke); 2004 patients (82.9%) had only one of these diagnoses, and 412 (17.1%) had more than one. Among patients with a given stage of peripheral arterial disease, mean age was older in the women than in the men. Coronary disease and cerebrovascular disease were more severe in the men. During the 18-month follow-up, 408 cardiovascular events were recorded in 380 patients (15.7% of the overall study group). In patients who had a single clinical event at inclusion, subsequent clinical events usually occurred in the same vascular bed. The incidences of coronary and cerebral events were correlated with age and the incidence of peripheral events with smoking status. Fatal events were correlated with age but not with the baseline diagnosis, except for a weak relationship with peripheral arterial disease. In a subset of 411 patients who had laboratory tests, plasma fibrinogen level was the only independent predictor of recurrence for all cardiovascular events; this parameter was more closely correlated with fatal events than with all events.

D-dimer: a characteristic of the coagulation state of each patient with chronic atrial fibrillation.

BACKGROUND AND OBJECTIVE: It is accepted that patients with atrial fibrillation (AF) are characterised by increased levels of plasmatic D-dimers, with a wide inter-individual variability depending on the patients and therapeutic characteristics, but it has not been established if this level was predictive of the risk of arterial thromboembolic event. In order to answer such a question, it has to be established if the D-dimer level in a given patient is characteristic of such a patient (stable over time) if also fluctuating with time (and useless to characterise the patient). METHODS AND RESULTS: One hundred thirty clinically stable patients with chronic AF were recruited (anticoagulant: group 1, antiaggregant aspirin: group 2, no antithrombotic: group 3). During the follow-up of patients without clinical events (n=63), it is notable that in patients with D-dimer levels <500 ng/ml, these remained <1000 ng/ml, in patients with levels between 500 and 1000 ng/ml, these did not reach 1590 ng/ml, and in those with D-dimers >1000 ng/ml, the levels remained relatively stable. Mean age and D-dimer levels were lower in group 1 (74.4 years and 509.1 ng/ml, respectively) than in group 2 (82.4 years, p=0.0003 and 1015.7 ng/ml, p<0.0001, respectively) and in group 3 (79.3 years and 1289.3 ng/ml, p<0.0001, respectively). The effect of the antithrombotic therapy was independent of the age of patients (p=0.017). CONCLUSION: D-dimer levels in patients with chronic AF remain in the same range over time. They are lower on anticoagulant therapy than on antiaggregant or no antithrombotic therapy, irrespective of age. Thus, D-dimers appear to be a useful parameter for assessing the degree of hypercoagulability of patients whatever their age.

Biochemical and functional abnormalities in hypercholesterolemic rabbit platelets.

This study was designed to elucidate changes in rabbit platelet lipids induced by a cholesterol rich diet and to explore the possible correlation of these lipid changes with platelet abnormalities. Pronounced biochemical alterations were observed when serum cholesterol levels of 700-1000 mg% were reached. Hypercholesterolemic (HC) platelets contained 37% more neutral lipids and 16% less phospholipids than the controls. Lysolecithin, cholesterol esters and phosphatidylinositol (PI) levels were increased in HC platelets, and the levels of phosphatidylcholine (PC) were decreased. The cholesterol/phospholipid molar ratio of lipidemic platelets increased from 0.55 +/- 0.011 to 0.89 +/- 0.016 (P less than 0.01) in eight weeks. HC platelets had 90% more arachidonic acid (AA) in the PI than normal platelets. No significant changes in AA of PC were observed. Platelet function was monitored by the uptake and release of [14C]serotonin in platelet rich plasma (PRP), using varying concentrations of collagen as an aggregating agent. The uptake of [14C]serotonin in HC and normal platelets ranged from 78-94%. The percent of [14C]serotonin released from normal and HC platelets was proportional to the concentration of collagen. However, lipidemic platelets were hyperreactive to low concentrations of collagen. Incorporation of 50 microM acetylsalicylic acid into the aggregating medium suppressed the release of [14C]serotonin in normal PRP by more than 90%, but had only a partial effect on lipidemic PRP.

[The role of thrombotic and hemostatic mechanisms in the initial phases of atherosclerosis]. / Participation des mécanismes de la thrombose et de l'hémostase aux étapes initiales de l'athérosclérose.

The factors of thrombosis (endothelium, haemostasis, coagulation, fibrinolysis) are implicated from the initiating phase of atherosclerotic lesions. Their participation is more established (and studied) in the later phases of intraluminal evolution of atherosclerosis, of thromboembolic complications of the lesions and interventional procedures. The traditional theory of response to physical lesions of the endothelium as an initiating factor of atherosclerotic lesions, which gave platelets an essential role, has been replaced by that linking an early functional lesion of the endothelium and a cellular response by monocytes infiltrating the vessel wall, becoming macrophages. The macrophages participate in changes of the LDL in the wall, ingest the lipids at the same time as the smooth muscle cells which have migrated and proliferated from the media to the intima. The lipid overload, especially with oxidised LDL, is intracellular at first in these foam cells, then extracellular as the cells die. During the early stages, all the tissue factors of activation and development of coagulation are present in the vessel wall and then within the lesion. This intra-cellular coagulation results in the production of thrombi in the tissues and the transformation of fibrinogen to fibrin. These stages precede and participate in cellular proliferation and extracellular lipid deposits. Factors of tissular thrombolysis (the uPA pathway) play a part in cellular immigration and proliferation. It is only at a later stage that the lesion activates intravascular coagulation and fibrinolysis which, in conditions of variable equilibrium, will result in the clinical complications of the atherosclerotic process. All these factors therefore participate firstly in the tissues and then within the lumen, in the progression and complications of atherosclerosis which for these reasons is often called atherothrombotic disease. The comprehension of these mechanisms is essential for the development and interpretation of tests and treatment applied to different stages of the disease, which is all the more complex given that in a given patient at a given time, lesions at different stages are present in the arterial network.

[Antiphospholipid antibodies: cause of thrombosis or an epiphenomenon?]. / Anticorps antiphospholipides: cause des thromboses ou épiphénomène?

Antiphospholipid antibodies (aPL) present in systemic lupus erythematosus and the primary antiphospholipid syndrome are a well-known risk factor for thrombosis. Most of them require the presence of a cofactor, beta 2-glycoprotein I for anticardiolipin antibodies, prothrombin for lupus anticoagulant. These aPL are of the "immune" type. APL are also found in various non-immunological conditions, in which repeated endothelial or membranous damages appear to be frequent, but thromboses are rare. Most of these aPL are cofactor-independent, except those induced by chlorpromazine, and might belong to "natural" antibodies.

[Direct and indirect effects of epoietin alpha in an experimental model of thrombosis and bleeding in the rabbit]. / Etude des effets directs et indirects de l'érythropoïétine dans un modèle expérimental de thrombose et de saignement chez le lapin.

OBJECTIVES: To study direct and indirect effects of EPO on haemostasis. STUDY DESIGN: Experimental, randomised. ANIMALS: Forty-eight New Zealand rabbits. METHOD: Animals were anaesthetised, ventilated and monitored continuously for blood pressure, heart rate, body temperature, and carotid blood flow variations and were randomised into four groups: control, EPO bolus 2400 IU kg(-1), fractionated EPO (one injection a week of 600 IU kg(-1) for 4 weeks), homologous red blood cell transfusion to reach the Ht level of the fractionated EPO group. A compression injury and a 75% stenosis of the carotid artery triggered a series of cyclic flow reductions (CFRs). CFRs were observed for a 20 min period in each group. Ear immersion bleeding time (BT) and hepato-splenic bleeding were performed at the end of the experiment. Biology was performed at the end of the thrombosis period: blood cells count, Hte, activated partial thromboplastin time, fibrinogen, arachidonic-induced platelet aggregation, EPO dosages. RESULTS: No significant increase in thrombosis (CFRs) in the two EPO groups and in the transfused group. Increase in Hte in the fractionated EPO group versus control. Group EPO bolus: decrease in BT and hepato-splenic bleeding versus control; decrease in hepato-splenic bleeding versus fractionated EPO group, increase in platelet aggregation velocity versus control. CONCLUSION: EPO did not increase the thrombotic risk in this rabbit model. EPO bolus decreased BT and hepato-splenic bleeding.

Hepatosplenic candidiasis in the era of new antifungal drugs: a study in Paris 2000-2007.

We report a retrospective study of 24 patients with haematological malignancy and hepatosplenic candidiasis. Clinical and biological features were similar to previous reports. No patient previously received antifungal prophylaxis. Liver or spleen histological examination revealed yeasts in 6/24 patients (25%) on direct examination but all cultures were negative. After a median duration of 7 months, antifungal treatment was discontinued in 58% of the patients with no relapse. Eleven (46%) patients died during follow up. After multivariate analysis, independent factors associated with death were the duration of neutropenia (p 0.022) and relapsing haematological malignancy (p 0.015).

Prothrombin G20210A carriers the genetic mutation and a history of venous thrombosis contributes to thrombin generation independently of factor II plasma levels.

SUMMARY BACKGROUND: The prothrombin (PT) G20210A gene mutation is a common risk factor for venous thrombosis (VT), which is mainly mediated through an increase in factor II (FII) plasma levels. High FII plasma levels may act through an increase in endogenous thrombin potential (ETP) a key step in hemostasis and thrombosis. While FII may be the main contributor to ETP in PT G20210A carriers, the knowledge of other environmental or genetic factors influencing ETP may help to better identify those at risk of VT. AIMS: ETP was determined in 472 non-carriers of PT G20210A (PT-) and in 325 unrelated carriers of PT G20210A (PT+) with (symptomatic n = 158) or without (asymptomatic, n = 167) a history of VT. All PT+ were heterozygous and free of other thrombophilic defects. RESULTS: ETP was higher in asymptomatic PT+ than in PT- (2038 +/- 371 vs. 1616 +/- 267 nmol L(-1) min; P < 0.0001). ETP was significantly higher in symptomatic PT+ than in controls PT+ (2129 +/- 430 vs. 2038 +/- 371 nmol L(-1) min; P = 0.01). Multivariate analyses evidenced the importance of FII and fibrinogen plasma levels in determining ETP. DISCUSSION: After taking these variables into account, a personal history of VT remained associated with ETP in PT+ carriers. Moreover, PTG20210A still contributes to ETP after consideration of FII levels. CONCLUSION: In conclusion, the increase in ETP observed in carriers is not entirely explained by higher FII or fibrinogen plasma levels but also by the history of VT.