Anaesthesia
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There has been an explosion of interest in the ability of tranexamic acid to reduce morbidity and mortality in surgical and traumatic bleeding. Tranexamic acid has been shown to reduce mortality due to traumatic bleeding by a third, without apparent safety issues. It is now clearly established that intravenous tranexamic acid reduces blood loss in patients with surgical bleeding and the need for transfusion. ⋯ However, clinical studies suggest that there is no increased efficacy in using a higher dose, and that a dose of 1 g intravenously in an adult patient has maximal efficacy, which is not increased by higher doses. The CRASH-2 trauma trial clearly showed no increase in thrombotic events after its use in trauma, indeed there was a significant reduction in myocardial infarction. However, trials of tranexamic acid in surgery have failed to adequately study its effects on the risk of postoperative venous and possible reduction in arterial thrombo-embolism, and this needs to be the subject of future research.
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The management of antithrombotic therapy in the peri-operative setting is a common problem, balancing haemorrhagic risk with continued treatment and thrombotic risk when discontinued. High-quality evidence is lacking regarding the optimal approach for patients on oral anticoagulants or antiplatelet agents. ⋯ Aspirin can be continued for most procedures. Dual antiplatelet agents for patients with a recently inserted coronary artery stent should be continued if possible but decisions should be individualised and taken after multidisciplinary discussion.
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Understanding the complex immunological consequences of red cell transfusion is essential if we are to use this valuable resource wisely and safely. The decision to transfuse red cells should be made after serious considerations of the associated risks and benefits. ⋯ Red cell transfusions should be acknowledged as immunological exposures, with consequences weighed against expected benefits. This article reviews immunological consequences and the emerging evidence that may inform risk-benefit considerations in clinical practice.
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The aetiology and management of haemostatic abnormalities in critical care patients are considered in this narrative review. The mechanisms of normal haemostasis and derangements that occur as a result of sepsis and organ dysfunction are discussed. Finally, the management of haemostatic abnormalities as they relate to critical care practice are considered, including the management of heparin-induced thrombocytopenia.
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There is a considerable difference between the mechanism of action of the lysine analogues, tranexamic acid and epsilon-aminocaproic acid, and the serine protease inhibitor aprotinin. Aprotinin acts to inactivate free plasmin, but with little effect on bound plasmin, whereas the lysine analogues are designed to prevent excessive plasmin formation by fitting into plasminogen's lysine-binding site to prevent the binding of plasminogen to fibrin. Aprotinin is associated with a reduction in bleeding and transfusion requirements following major surgery, and has a dose-response profile, compared with no dose-response effect in the one study investigating tranexamic acid in cardiac surgical patients. Following its withdrawal in 2007, which is explained in detail in this review, the regulators have now licensed aprotinin for myocardial revascularisation only, which is relatively low-risk for bleeding.