Approximately one to two million cardiac surgery operations are performed worldwide each year accounting for about 80% of all surgical blood use. Recently, patient blood management guidelines endorse acute normovolemic hemodilution (ANH) for use during cardiac surgery in which part of the patient’s blood is removed and replaced with IV fluid prior to or during the surgery. Stored autologous blood is re-infused after the surgery or during surgery in cases of severe bleeding. Benefits of ANH may include decreased blood viscosity, increased efficiency of the heart, and potential preservation of clotting factors and platelets, thereby reducing the need for allogenic blood transfusions. To assess the optimal volume of ANH to reduce allogenic blood transfusions, 110 adult patients undergoing cardiac surgery with an intermediate-high risk of transfusion were randomly assigned to moderate-ANH (5 to 8 mL/kg; N=55) or large-AHN (12 to 15 mL/kg; N=55) arms of a partially blinded controlled trial in China. Both the number of RBC units and incidence of RBC transfusion were lower in patients in the large-ANH arm (p=0.012 and p=0.042, respectively), and an inverse relationship was found between volume of ANH and RBC units (Spearman r= -0.48). Furthermore, post-operative bleeding was significantly lower in the large-ANH arm compared to the moderate-AHN arm (3.6% vs. 18.2%, p=0.029). Further research is needed to confirm these results.
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