High or low hematocrits during cardiopulmonary bypass for patients undergoing coronary artery bypass graft surgery? An evidence-based approach to the question.

We have observed an inverse relationship between a CPB Hct <20% and the need for cardiac support and hospital mortality. These data call for an aggressive and concerted effort to avoid a CPB Hct of <20%. The focus should be directed at women and small men since this subset of patients are most likely to experience low CPB Hct. A comprehensive, multimodality blood-conservation plan that involves the use of erythropoietin, aprotinin, preoperative autologous donation, shed blood reinfusion, and minimal phlebotomy for blood testing was proposed by Rosengart and colleagues based on their experience in caring for 50 Jehovah's Witness patients. Efforts to conserve blood and ensure hemostasis should cover the entire spectrum of care, including preoperative phlebotomy (for blood tests), diagnostic and interventional procedures, and intraoperative and postoperative care. Further work is needed to understand the mechanism for the relationship between low Hct and adverse outcomes. Each open-heart center should consider the Hct question carefully, examining both the published literature and their own results related to CPB Hct and patient outcomes.