Effects of blood transfusion on oxygen extraction ratio and central venous saturation in children after cardiac surgery

BACKGROUND: Red blood cell transfusion is common in critically ill children after cardiac surgery. Since the threshold for hemoglobin (Hb) transfusion need is not well defined, the threshold Hb level at which dependent critical oxygen uptake-to-delivery (VO(2)-DO(2)) status compensation is uncertain. OBJECTIVES: To assess the effects of blood transfusion on the oxygen extraction ratio (O(2)ER) and central venous oxygen saturation (ScvO(2)) to identify a critical O(2)ER value that could help us determine the critical need for blood transfusion. DESIGN: Prospective, observational cohort study. SETTING: Cardiac Surgical Intensive Care Unit at Prince Sultan Cardiac Center in Qassim, Saudi Arabia. PATIENTS AND METHODS: Between January 2013 and December 2015, we included all children with cardiac disease who underwent surgery and needed a blood transfusion. Demographic and laboratory data with physiological parameters before and 1 and 6 hours after transfusion were recorded and O(2)ER before and 6 hours after transfusion was computed. Cases were divided into two groups based on O(2)ER: Patients with increased O(2)ER (O(2)ER >40%) and normal patients without increased O(2)ER (O(2)ER ≤40%) before transfusion. MAIN OUTCOME MEASURE(S): Changes in O(2)ER and ScvO(2) following blood transfusion. RESULTS: Of 103 patients who had blood transfusion, 75 cases had normal O(2)ER before transfusion while 28 cases had increased O(2)ER before transfusion. Following blood transfusion, O(2)ER and ScvO(2) improved in the group that had increased O(2)ER before transfusion, but not in the group that had normal O(2)ER before transfusion. CONCLUSIONS: The clinical and hemodynamic indicators O(2)ER and ScvO(2) may be considered as markers that can indicate a need for blood transfusion. LIMITATIONS: The limitation of this study is the small number of patients that had increased O(2)ER before transfusion. There were few available variables to assess oxygen consumption.