Globally, over two million individuals undergo cardiac surgery annually, and about one third receive at least one unit of allogeneic RBCs. Based on limited data from small randomized controlled trials and retrospective studies, both the American and European guidelines on patient blood management for cardiac surgery suggest that acute normovolemic hemodilution (ANH) may be considered to reduce RBC transfusions during surgery. ANH, which involves removal of whole blood before anesthesia and replacing it with crystalloid solution to maintain normovolemic volumes, is performed in about 20% of all cardiac surgery departments in the U.S. To determine if ANH reduces the need for RBC transfusion for cardiac surgery patients, researchers randomized 2010 cardiac surgery patients in 11 countries to receive either ANH (n=1010; median age, 59 years; 22% female; 78% white) or standard care (n=1000; median age, 61 years; 19% female; 78% white). Patients in the ANH arm had >650 mL whole blood withdrawn before surgery that was then reinfused after surgery. During the perioperative period, 27% of patients (274/1005) in the ANH arm received an RBC transfusion compared to 29% (291/997) in the standard care arm (relative risk, 0.93; 95% C.I., 0.81 to 1.07; p=0.34). The median number of RBC units transfused in both arms was two units with an interquartile range of one to four units in the ANH arm and one to three in the standard care arm. The risks of 30-day mortality and adverse events were similar between arms. Further studies are needed to confirm that ANH does not reduce RBC transfusion need in cardiac surgery patients.
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