Implications and Management of Anemia in Cardiac Surgery: Current State of Knowledge
The following are key points about anemia in the setting of cardiac surgery:
1. Anemia (hemoglobin <10 g/dl) is common among patients undergoing cardiac surgery, with a prevalence ranging from 16-54%.
2. While it is unclear what hemoglobin level is optimal during cardiac surgery, multiple large observational studies have suggested that preoperative anemia is associated with increased noncardiac morbidity and mortality after cardiopulmonary bypass (CPB). Anemia should be investigated and corrected before surgical intervention.
3. While some have suggested the administration of erythropoietin (EPO) preoperatively as a means to increase red blood cell (RBC) mass, this strategy may potentially contribute to adverse outcomes.
4. Multiple mechanisms are responsible for intraoperative anemia, including CPB priming volume, crystalloid solutions, and bleeding due to technical factors or coagulopathy. Intraoperative anemia is associated with adverse neurologic, renal, cardiac, and pulmonary outcomes.
5. The management of postoperative anemia may start with “safe” practices that include avoiding hemodilution, limiting excessive blood draws, and emphasizing intraoperative hemostasis.
6. Antifibrinolytics may reduce blood loss and RBC use, and the Society of Thoracic Surgeons blood conservation update gives a Class I recommendation for the use of lysine analogues during cardiac surgery. E-aminocaproic acid and tranexamic acid are the most commonly used agents.
7. Platelets may be used to manage persistent microvascular bleeding in the operating room, but their use prophylactically is not indicated.
8. The management of postoperative anemia requires a balance between the risks associated with substantial anemia and the adverse outcomes that may come with RBC transfusions. Patients may be able to tolerate a reasonable level of anemia postoperatively.
9. Multiple mechanisms are responsible for the adverse outcomes that may be associated with liberal use of RBC transfusions postoperatively. These factors include transfusion-related acute lung injury, transfusion-related circulatory overload, and immunomodulation. The impact of storage on the RBC product is another consideration.
10. Future research should clarify the relationship between the adverse outcomes of anemia and the benefits and risks of interventions to correct it.
Keywords: Prevalence, Erythropoietin, Erythrocytes, Hemodilution, Immunomodulation, Cardiopulmonary Bypass, Hemostasis, Postoperative Period
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