Transfusion medicine reviews
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Blood transfusion remains one of the commonest interventions carried out upon individuals undergoing cardiac surgery. Despite this, the scientific rationale on which to base this decision is limited. Currently, hemoglobin concentration is often used as the sole guide as to when a transfusion may be required. ⋯ Furthermore, oxygen requirements during the initial perioperative phase are reduced because of the effect of general anesthesia and hypothermia during cardiopulmonary bypass. When deciding to transfuse, consideration should be given to red cell volume, circulatory status, and oxygen requirement. It is possible that such an all-encompassing approach would reduce the incidence of unnecessary, and potentially counterproductive, red cell transfusion in cardiac surgery.
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Use of recombinant Factor VIIa (rFVIIa) has extended to nonhemophiliac patients anticipated to be at risk of major bleeding (prophylactic) or who have uncontrolled bleeding (therapeutic). The aim of this review was to systematically appraise randomized controlled trial (RCT) evidence for effectiveness of rFVIIa, by updating and extending the earlier Cochrane Systematic Review. Up to January 2007, 17 RCTs were identified in which rFVIIa was used to try to reduce bleeding in patients undergoing planned high blood loss surgery or in acute situations such as trauma, gastrointestinal bleeding, and intracerebral hemorrhage (ICH). ⋯ Selected subgroup analysis or secondary outcome results for other therapeutic trials appeared promising but were usually associated with methodological limitations. The thromboembolic adverse event incidence in subjects who received rFVIIa is of concern and occurred despite a common trial exclusion criterion of patients with a history of previous thromboembolic or vasoocclusive disease. The reasons for increasing use of this drug off license remain unclear, and the results of further trials are required to establish effectiveness.
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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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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.