Mitochondrial oxygen tension in critically ill patients receiving red blood cell transfusions: a multicenter observational cohort study

Purpose Currently, there is no marker of efficacy of red blood cell (RBC) transfusion. This study describes the impact of RBC transfusion on mitochondrial oxygen tension (mitoPO(2)) and mitochondrial oxygen consumption (mitoVO(2)) in critically ill patients with anemia. Methods Critically ill patients with a hemoglobin concentration < 10 g/dL, for whom a single RBC unit had been ordered, were included. MitoPO(2) was measured with the COMET device immediately before RBC transfusion, 0.5 h, 1 h, 3 h, and 24 h after RBC transfusion. MitoVO2 was calculated from dynamic mitoPO(2) measurements during cessation of local oxygen supply. Results Sixty-three patients participated, median age 64.0 (interquartile range (IQR) 52.3-72.8) years, median hemoglobin concentration before transfusion 7.4 (IQR 7.1-7.7) g/dL. Median mitoPO(2) values were 55.0 (IQR 49.6-63.0) mmHg before RBC transfusion, 51.0 (IQR 41.5-61.2) directly after and 67.3 (IQR 41.6-83.7) at 24 h after RBC transfusion. Median mitoVO(2) values were 3.3 (IQR 2.1-5.9) mmHg/s before RBC transfusion, 3.7 (IQR 2.0-5.1) mmHg/s directly after, and 3.1 (IQR 2.5-4.8) mmHg/s 24 h after RBC transfusion. In the higher Hb concentration group (> 7 g/dL), we saw a dissociation of the effect of RBC transfusion on mitoPO(2) versus on mitoVO(2) values. MitoPO(2) and mitoVO(2) values were not associated with commonly used parameters of tissue perfusion and oxygenation. ConclusionRBC transfusion did not alter mitoPO(2) and mitoVO(2) in critically ill patients with anemia. MitoPO(2 )and mitoVO(2) values were not notably associated with Hb concentrations, parameters of severity of illness and markers of tissue perfusion or oxygenation. Given the high baseline value, it cannot be excluded nor confirmed whether RBC can improve low mitoPO(2).