Étude du rôle des plaquettes sanguines dans l’anaphylaxie

Anaphylactic shock is the most severe expression of immediate hypersensitivity reactions. The mechanisms leading to these reactions are still poorly understood and may involve platelets, especially in the most severe forms. Our results indicate that, although platelets are not a primary effector during IgE-mediated anaphylactic reactions, they contribute significantly to modulate the severity of the reaction in different experimental models of anaphylaxis, with a different response depending on the mechanism of the reaction. The mechanisms responsible for this effect are not yet identified. Targeting the Platelet Activating Factor receptor seems to be interesting from a therapeutic point of view. A better characterization of the models used and the mechanisms responsible for the reactions in humans should allow a better understanding of the contribution of platelets to the severity of anaphylactic shock.Le choc anaphylactique est l’expression la plus sévère des réactions d’hypersensibilité immédiate. Les mécanismes conduisant à ces réactions sont encore mal compris et pourraient impliquer les plaquettes, notamment dans les formes les plus sévères. Nos résultats indiquent que, bien que les plaquettes ne soient pas un effecteur primaire au cours des réactions anaphylactiques médiées par les IgE, elles contribuent de manière significative à moduler la sévérité de la réaction dans différents modèles expérimentaux d’anaphylaxie, avec une réponse différente selon le mécanisme à l’origine de la réaction. Les mécanismes responsables de cet effet ne sont pour l’heure pas identifiés. Le ciblage du récepteur du Platelet Activating Factor semble être intéressant d’un point de vue thérapeutique. Une meilleure caractérisation des modèles utilisés et des mécanismes responsables des réactions chez l’Homme devrait permettre de mieux comprendre la contribution des plaquettes à la sévérité du choc anaphylactique

Reply to the authors of “Age-adjusted D-dimer cut-off levels to exclude venous thromboembolism in COVID-19 patients”

International audienceWe thank the authors for taking interest in the 2021 updated GIHP/GFHT proposals on thromboprophylaxis for COVID-19 patients. The authors proposed to consider an ageadjusted D-dimer cutoff to exclude venous thromboembolism (VTE) in COVID-19 patients. We would like to clarify this misunderstanding regarding D-dimers during COVID-19. I

Prevention of thrombotic risk in hospitalized patients with COVID-19 and hemostasis monitoring.

COVID-19 is an infection induced by the SARS-CoV-2 coronavirus, and severe forms can lead to acute respiratory distress syndrome (ARDS) requiring intensive care unit (ICU) management. Severe forms are associated with coagulation changes, mainly characterized by an increase in D-dimer and fibrinogen levels, with a higher risk of thrombosis, particularly pulmonary embolism. The impact of obesity in severe COVID-19 has also been highlighted.In this context, standard doses of low molecular weight heparin (LMWH) may be inadequate in ICU patients, with obesity, major inflammation, and hypercoagulability. We therefore urgently developed proposals on the prevention of thromboembolism and monitoring of hemostasis in hospitalized patients with COVID-19.Four levels of thromboembolic risk were defined according to the severity of COVID-19 reflected by oxygen requirement and treatment, the body mass index, and other risk factors. Monitoring of hemostasis (including fibrinogen and D-dimer levels) every 48 h is proposed. Standard doses of LMWH (e.g., enoxaparin 4000 IU/24 h SC) are proposed in case of intermediate thrombotic risk (BMI  120 kg), or unfractionated heparin (UFH) if renal insufficiency (200 IU/kg/24 h, IV), is proposed. The thrombotic risk was defined as very high in obese patients with ARDS and added risk factors for thromboembolism, and also in case of extracorporeal membrane oxygenation (ECMO), unexplained catheter thrombosis, dialysis filter thrombosis, or marked inflammatory syndrome and/or hypercoagulability (e.g., fibrinogen > 8 g/l and/or D-dimers > 3 μg/ml). In ICU patients, it is sometimes difficult to confirm a diagnosis of thrombosis, and curative anticoagulant treatment may also be discussed on a probabilistic basis. In all these situations, therapeutic doses of LMWH, or UFH in case of renal insufficiency with monitoring of anti-Xa activity, are proposed.In conclusion, intensification of heparin treatment should be considered in the context of COVID-19 on the basis of clinical and biological criteria of severity, especially in severely ill ventilated patients, for whom the diagnosis of pulmonary embolism cannot be easily confirmed

Impact of COVID-19 and lockdown regarding blood transfusion

BACKGROUND: The outbreak of a SARS-CoV-2 resulted in a massive afflux of patients in hospital and intensive care units with many challenges. Blood transfusion was one of them regarding both blood banks (safety, collection, and stocks) and consumption (usual care and unknown specific demand of COVID-19 patients). The risk of mismatch was sufficient to plan blood transfusion restrictions if stocks became limited. STUDY DESIGN AND METHODS: Analyses of blood transfusion in a tertiary hospital and blood collection in the referring blood bank between February 24 and May 31, 2020. RESULTS: Withdrawal of elective surgery and non-urgent care and admission of 2291 COVID-19 patients reduced global activity by 33% but transfusion by 17% only. Only 237 (10.3) % of COVID-19 patients required blood transfusion, including 45 (2.0%) with acute bleeding. Lockdown and cancellation of mobile collection resulted in an 11% reduction in blood donation compared to 2019. The ratio of reduction in blood transfusion to blood donation remained positive and stocks were slightly enhanced. DISCUSSION: Reduction of admissions due to SARS-CoV-2 pandemic results only in a moderate decrease of blood transfusion. Incompressible blood transfusions concern urgent surgery, acute bleeding (including some patients with COVID-19, especially under high anticoagulation), or are supportive for chemotherapy-induced aplasia or chronic anemia. Lockdown results in a decrease of blood donation by cancellation of mobile donation but with little impact on a short period by mobilization of usual donors. No mismatch between demand and donation was evidenced and no planned restriction to blood transfusion was necessary

Coronavirus Disease 2019: Associated Multiple Organ Damage

A 56-year-old man presented a particularly severe and multisystemic case of coronavirus disease 2019 (COVID-19). In addition to the common lung and quite common pulmonary embolism and kidney injuries, he presented ocular and intestinal injuries that, to our knowledge, have not been described in COVID-19 patients. Although it is difficult to make pathophysiological hypotheses about a single case, the multiplicity of injured organs argues for a systemic response to pulmonary infection. A better understanding of physiopathology should feed the discussion about therapeutic options in this type of multifocal damage related to severe acute respiratory syndrome coronavirus 2

Prevention of venous thromboembolism and haemostasis monitoring in patients with COVID-19: Updated proposals (April 2021)

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