Vascular
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To effectively balance bleeding and clotting in surgical patients, the surgeon needs a fundamental knowledge of coagulation biology. The endothelium and activated platelets play crucial roles in coagulation. Activated platelets and damaged endothelial cells provide a platform of negatively charged phospholipids that not only bind coagulation factors and their complexes but also accelerate the conversion of inactive zymogens to active serine proteases. ⋯ Correctly diagnosing and appropriately treating perioperative bleeding in surgical patients require a basic understanding of the most common bleeding and clotting disorders. This article provides an overview of the characteristic features of common coagulopathic conditions and their treatment options. Given the challenge of balancing bleeding and clotting in surgical patients, hemostatic management must be tailored to each patient and should take into account the patient's genetic and acquired risk factors and the acute disturbances in bleeding and clotting caused by surgical intervention.
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Heparin is the predominant anticoagulant used in cardiac and vascular surgery. Heparin-induced thrombocytopenia (HIT) is one of the most serious and life-threatening adverse drug reactions associated with heparin use. In addition to the development of thrombocytopenia, HIT is associated with a high risk (40-50%) of thrombotic complications. ⋯ The risk of HIT varies significantly depending on the type of heparin (unfractionated heparin greater than low-molecular-weight heparin), duration of heparin use, and patient population (surgery greater than medical). Readily available serologic assays for serum antibodies against H-PF4 allow for rapid confirmation of a clinical diagnosis of HIT. Owing to the high risk of thrombosis associated with HIT, antithrombotic therapy with direct thrombin inhibitors (lepirudin or argatroban) should be started when serologic assays confirm clinical suspicion.
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The prospect of surgery without blood loss is an emerging reality. Use of a blood conservation strategy is gaining increasing recognition as a sound and practical approach, especially for the majority of large blood loss surgeries. However, critical situations still occur in which transfusions are necessary or unavoidable for the short-term survival of the patient. ⋯ Increasingly, hospitals are adopting blood conservation strategies as part of their routine practice. Blood conservation is a rapidly evolving field in which active research is expanding our understanding of the molecular, physiologic, and clinical aspects of hematopoiesis, circulatory response, coagulation enigmas, artificial oxygen carriers, and the impact of anemia on organ function. Ongoing research offers the possibility of replacement or elimination of allogeneic blood transfusions in a variety of clinical settings.
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Review Historical Article
Bovine thrombin: history, use, and risk in the surgical patient.
Thrombin is a common hemostatic drug used in surgical practice for over 100 years because of its simplicity and efficacy. Thrombin converts fibrinogen to fibrin, activates platelets, and induces vascular contraction. It is available in multiple forms, including human thrombin, bovine thrombin, and, most recently, human recombinant thrombin. ⋯ Patients with multiple elevated antibodies prior to surgery are also more likely to sustain adverse events. Animal studies confirm these immunological responses seen in humans. With the available clinical and laboratory data, a less immunogenic yet biologically effective thrombin should be available for use in our surgical patients.
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The successful management of patients with arterial or venous vascular disease is increasingly dependent on the effective use of pharmacotherapeutic agents. Anticoagulation therapies for thromboembolic disease are continually improving, and platelet inhibition remains a cornerstone treatment for all patients with atherosclerotic disease. Early ischemic complications can be avoided by proper preoperative prescription, intraoperative management, and postoperative pharmacotherapy. ⋯ Unfractionated or low-molecular-weight heparin, warfarin, and long-term platelet inhibition can improve survival, reduce the risk of other vascular bed ischemic events, and improve the long-term success of the target revascularization procedure. An overview of evidence-based antithrombotic strategies will include a discussion of patients who undergo the two most common open vascular reconstructive procedures, carotid endarterectomy and infrainguinal bypass. The appropriate use of antithrombotic therapy for vascular reconstructive surgery patients has important implications for both short- and long-term patient outcomes.