Effect of dilutional anemia that can be treated with only one unit of red blood cell transfusion on tissue oxygenation in cardiac surgery patients

Abstract

Background/aim: Cardiac surgery, especially in the presence of cardiopulmonary bypass (CPB), is associated with an inflammatoryreaction that may promote microcirculatory alterations, in addition to the general impact on system hemodynamics. Anemia andtransfusion make patients more susceptible to the deleterious effects of CPB. In this study, it was aimed to evaluate the effect of dilutionalanemia, which is caused by CPB and can be treated with 1–2 units of red blood cell (RBC) transfusion, on global tissue oxygenationparameters in cardiac surgery patients.Materials and methods: This prospective observational study comprised 127 patients who had a relatively stable operation periodwithout any major anesthetic or surgical complications (e.g., operation duration >5 h, bleeding or hemodilution requiring more than1–2 units of RBCs, or unstable hemodynamics, requiring inotropic support of more than 5 µg/kg/min dopamine). Patients wereobservationally divided into two groups: minimally transfused (Group Tr) and nontransfused (Group NTr). Global tissue oxygenationparameters were evaluated after anesthesia induction (T1) and at the end of the operation (T3) and compared between the groups.Results: Group Tr consisted of patients who had significantly lower preoperative hemoglobin values than Group NTr patients. Thedilutional anemia of all Group Tr patients could be corrected with 1 unit of RBCs. The lactate levels at T3, increment rates of lactate,and venoarterial carbon dioxide pressure difference (ΔpCO2) levels [(T3 – T1) : T1] in Group Tr were significantly higher than those inGroup NTr.Conclusion: Dilutional anemia as a result of CPB mostly occurs in patients with borderline preoperative hemoglobin concentrationsand its correction with RBC transfusion does not normalize the degree of microcirculatory and oxygenation problems, which thepatients are already prone to because of the nature of CPB. Preventing dilutional anemia and transfusion, especially in patients withpreoperative borderline hemoglobin levels, may therefore reduce the burden of impaired microcirculation-associated organ failure inon-pump cardiac surgery