State-of-the-art blood conservation strategies following repair of aortic aneurysms and acute aortic dissection
Current Research Cardiology
P atients surgically treated for thoracic aortic aneurysms, acute aortic syndromes encompassing type A intramural hematoma, penetrating aortic ulcers and acute type A aortic dissection area at an increased risk for blood loss that can complicate surgical repair (1) and lead to life-threatening coagulopathy (2). Major blood loss is defined as a loss of ≥20% total blood volume. Five to seven percent of cardiac surgery procedures are associated with severe bleeding and up to 50% of patients
... of patients require blood transfusions (3). This increases complication rates, length of intensive care unit (ICU) stay, incidence of multisystem organ failure, hospital stay and mortality. There are multiple factors that are responsible including patient hypothermia, hemodilution, fibrinolysis, platelet dysfunction, and activation of a proinflammatory coagulopathic state due to surgery and cardiopulmonary bypass (CPB). The beneficial effect of blood transfusion needs to be carefully balanced to avoid potential adverse reactions and complications such as transfusion reactions, transmitted infections, metabolic disequilibration, acute lung injury and negative impact on immunological function (4). This has led to the development of multiple algorithms that aim to reduce blood loss, promote blood conservation and aid rapid hemostasis. The present review discusses wide-ranging current multimodal strategies deployed pre-, intra-and postoperatively after complex aortic surgery to minimize transfusion and blood product use. PharmacotheraPy to increase blood volume and reduce blood loss To decrease the exposure to allogeneic blood transfusion (ABT), a reduction of the perioperative blood loss is important. This reduction may be achieved through the pre-, peri-and postoperative management of pharmacological adjuvants that decrease bleeding and pharmacological alternatives to stimulate erythropoiesis and increase oxygen transport. Routine use of antiplatelet drugs is limited where possible preoperatively (5,6). It is normal to continue acetylsalicylic acid preoperatively because there is good evidence that demonstrates adverse outcomes in cardiovascular and neurological end points when it is suddenly discontinued (5) . In the elective setting, unless there are compelling specific reasons, other antiplatelet agents (ADP receptor inhibitors [eg, clopidogrel, prasugrel, ticagrelor]; phosphodiesterase inhibitors [eg, cilostazol]; adenosine reuptake inhibitors [eg, dipyridamole; thromboxane inhibitors [eg, terutoban]) are discontinued. Patients taking warfarin/vitamin K antagonists are bridged with intravenous heparin until the operation. This specifically applies to patients on vitamin K antagonists for metallic cardiac valves because the risk for thrombosis is high and has catastrophic consequences. Patients on warfarin for other indications, such as deep vein thrombosis, pulmonary emboli and atrial fibrillation, are bridged with low-molecular-weight heparins, with the dose omitted the day before the operation to normalize coagulation before surgery. Patients with low hemoglobin counts preoperatively need appropriate loading and supplementation with iron. Patients who are unable to receive blood products (eg, Jehovah's Witnesses) or have metabolic reason for pre-operative anemia require treatment with recombinant erythropoietin (5). restrictive transfusion theraPy Almost all randomized controlled trials (RCTs) have shown that the use of restrictive transfusion therapy in euvolemic surgical patients does not increase the rates of postoperative morbidity or mortality, or the length of hospital stay, while it does reduce both the percentage of transfused patients and the volume of allogeneic blood administered (5). Patients without signs of perioperative ischemia tolerate hemoglobin levels as low as 80 g/L without increased postoperative morbidity or mortality in review K schulte, r attia. state-of-the-art blood conservation strategies following repair of aortic aneurysms and acute aortic dissection. curr res cardiol 2014;1(1):17-22. Cardiac surgery is associated with excessive bleeding and complex aortic surgery poses a higher risk for bleeding diathesis. Predictors of bleeding include patient factors such as older age, emergency surgery, lower body surface area and the use of perioperative antiplatelet agents. Operative factors include prolonged cardiopulmonary bypass (CPB) time, complexity of surgery, reoperative surgery and prolonged hypothermia. Between 2% and 15% of patients require re-exploration for bleeding. Although a surgically correctable source is found in 50% to 67% of cases, bleeding and surgical re-exploration are independent predictors of adverse outcome. The use of allogeneic transfusions is associated with numerous adverse outcomes such as an increase in nosocomial infection and mortality in critically ill patients. Blood conservation strategies and steps to minimize bleeding are the desired clinical goal. Preoperative antiplatelet agents are limited when possible. Transfusion triggers use hemoglobin levels and platelet counts to guide treatment. Advanced measurements (whole body oxygen-carrying capacity, oxygen consumption, oxygen extraction ratios and oxygen delivery) represent accurate methods to estimate the need for transfusion. Intraoperative deployment of minimally invasive techniques and meticulous hemostasis reduce blood loss. Modified strategies for CPB are discussed such as using activated clotting time-guided heparinization, retrograde autologous priming of the CPB circuit, autotransfusion and cell salvage. Postoperative use of autologous transfusion strategies, and pharmacological adjuncts, such as aprotinin, lysine analogues epsilon-aminocaproic acid and tranexamic acid, are discussed. Specific correction of coagulation using fresh frozen plasma, cryoprecipitate or factor VIIa may be required. The multimodality approach to blood loss aims to optimize outcomes in highrisk aortic surgical patients.