Transfusion medicine reviews
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In an exciting era with many alternatives to the old anticoagulants heparin and warfarin emerging on the scene, awareness of the possibility to reverse their effect is mandatory. In this review, the traditional antidotes for warfarin (vitamin K, plasma, and prothrombin complex concentrate) and for heparin (protamine) are described together with the newer alternatives (recombinant activated factor VII, concatameric peptides, and recombinant platelet factor 4). ⋯ The small direct thrombin inhibitors may be reversed with activated prothrombin complex concentrate but not with recombinant activated factor VII, whereas the latter agent appears to be effective against the pentasaccharides and the recombinant nematode anticoagulant protein C2. Additional options that may become available in the future are also discussed briefly.
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The Serious Hazards of Transfusion (SHOT) scheme is a UK-wide, independent, professionally led hemovigilance system focused on learning from adverse events. SHOT was established in 1996 as a confidential reporting system for significant transfusion-related events, building an evidence base to support blood safety policy decisions, clinical guidelines, clinician education, and improvements in transfusion practice. Recommendations are formulated by an independent steering group drawn from medical royal colleges and professional bodies. ⋯ Cumulative SHOT data have documented the decline in transfusion-related graft vs host disease after implementation of leucodepletion and have highlighted transfusion-related acute lung injury and bacterial contamination of platelets as important causes of death and morbidity. The UK blood services have developed strategies to reduce these risks. Future SHOT data will evaluate the success of these and other blood safety improvements.
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Cardiac surgery affects both coagulation and platelet function. Revision of surgery due to bleeding has to be performed in 2% to 6% of patients undergoing cardiac surgery and is generally associated with a marked deterioration in prognosis. Factors contributing to acquired hemostatic abnormalities in cardiac surgery include the use of anticoagulants as well as the activation and consumption of coagulation factors and platelets induced by the extracorporeal circulation. ⋯ In contrast to point of care methods, laboratory assessment of hemostasis is more time-consuming and, thus, often not as rapidly available as required. At this time, the therapy for perioperative hemostatic abnormalities is based mainly on the administration of blood components (fresh frozen plasma and platelet concentrates). In the future, recombinant activated factor VIIa might prove to be a therapeutic option in patients with otherwise untractable bleeding, but the efficacy of recombinant activated factor VIIa has yet to be defined for this indication.
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Critically ill patients receive an extraordinarily large number of blood transfusions. Between 40% and 50% of all patients admitted to intensive care units (ICUs) receive at least one allogeneic red blood cell (RBC) unit and average close to 5 U of RBCs during their ICU admission. RBC transfusion is not risk-free, and there is little evidence that "routine" transfusion of stored allogeneic RBCs is beneficial to critically ill patients. ⋯ Similarly, in critically ill patients, rHuEPO therapy will also stimulate erythropoiesis. In randomized placebo-controlled trials, therapy with rHuEPO resulted in a significant reduction in allogeneic RBC transfusions. Strategies to increase the production of RBCs are complementary to other approaches to reduce blood loss in the ICU and decrease the transfusion threshold in the management of all critically ill patients.
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Repair of thoracoabdominal aortic aneurysms (TAAA) is associated with major blood loss, often exceeding the patient's intravascular volume, and complex intraoperative and postoperative coagulopathies necessitating large-volume transfusion of blood products. Abnormalities sufficient to cause thrombocytopenia or clinically important prolongation of clotting parameters are rarely present before surgery in elective aneurysms but are more common with ruptured aneurysms. ⋯ Adjuncts to reduce blood losses and blood product use include low-dose aprotinin or epsilon -aminocaproic acid, intraoperative blood salvaging, and acute normovolemic hemodilution. In TAAA repair, an average blood loss of 5000 to 6000 mL and average transfusion of allogeneic blood products of 50 to 60 U are to be anticipated.