Anaesthesia
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Allogeneic red cell transfusion is a commonly used treatment to improve the oxygen carrying capacity of blood during the peri-operative period. Increasing arterial oxygen content by increasing haemoglobin does not necessarily increase tissue oxygen delivery or uptake. Although the evidence-base for red cell transfusion practice is incomplete, randomised studies across a range of clinical settings, including surgery, consistently support the restrictive use of red cells, with no evidence of benefit for maintaining patients at higher haemoglobin thresholds (liberal strategy). ⋯ The degree to which the optimal haemoglobin concentration or transfusion trigger should be modified for patients with additional specific risk factors (e.g. ischaemic heart disease), remains less clear and requires further research. Although most clinical practice guidelines recommend restrictive use of red cells, and many blood transfusion services have seen marked falls in overall usage of red cells, the use of other blood components such as fresh frozen plasma, platelets, and cryoprecipitate has risen. In clinical practice, administration of fresh frozen plasma is usually guided by laboratory tests of coagulation, mainly prothrombin time, international normalised ratio and activated partial thromboplastin time, but the predictive value of these tests to predict bleeding is poor.
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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.
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We describe the development and laboratory assessment of a refined prototype tactile feedback device for the safe and accurate application of cricoid pressure. We recruited 20 operating department practitioners and compared their performance of cricoid pressure on a training simulator using both the device and a manual unaided technique. ⋯ Most importantly, the percentage of force applications that deviated from target by more than 10 N decreased from 18% to 7% (p < 0.01). The device requires no prior training, is cheap to manufacture, is single-use and requires no power to operate, whilst ensuring that the correct force is always consistently applied.