Restrictive Transfusion StratEgy Adjusted by SvO2 During Cardiac Surgery

Cardiac surgery represents only a small fraction of all surgical procedures, but consumes a significant proportion of the stored red blood cells (RBC), with almost 50% of patients receiving a perioperative transfusion. Since RBC transfusion is associated with an increased risk of morbidity and mortality, blood patient management strategy has been promoted to favour prevention of anaemia, reduction of bleeding and limitation of transfusion. Current guidelines recommend haemoglobin (Hb) threshold as low as 7 g/dL, but still with a wide possible range (7 to 9 g/dl) and suggest that Hb alone may not be the best criteria for triggering transfusion. As Hb is an oxygen carrier, the rationale for RBC transfusion should be to increase tissue oxygen delivery. Central venous oxygen saturation (central SvO2), which is related to the balance between tissue oxygen delivery and consumption, is easily measurable in cardiac surgery. In a previous study, the investigators showed that in anaemic patients having undergone cardiac surgery, restrictive transfusion according to central SvO2 allowed a significant reduction in RBC transfusion incidence in the ICU. The investigators hypothesize that a restrictive transfusion strategy adjusted by SvO2 during all the perioperative period of cardiac surgery may reduce further the incidence of RBC transfusion. Limiting RBC transfusion to patients with a low SvO2 could save unnecessary transfusions, without increasing the anaemia related risk.