Are multiple blood transfusions really a cause of acute respiratory distress syndrome?

Background and objectives: Multiple blood transfusions are considered a common cause of acute respiratory distress syndrome (ARDS). We hypothesized that ARDS is more a consequence of ARDS risk factors (in particular circulatory shock) requiring transfusions than a result of the transfusions themselves. Methods: This retrospective study included 103 patients admitted during a 10-month period to an 858-bed university hospital who received multiple transfusions (more than six units of packed red blood cells in 24 h). Results: Ten patients developed ARDS; they were more commonly admitted with circulatory shock (36 (38.7%) vs. 8 (80%), P = 0.01), polytrauma (7 (7.5%) vs. 4 (40%), P = 0.01) or thoracic trauma (3 (3.2%) vs. 4 (40%), P = 0.01). The sequential organ-failure assessment (SOFA) score at admission was higher in patients who developed ARDS than in those who did not (9.0 +/- 3.1 vs. 5.6 +/- 3.4, P < 0.005). The total amount of transfusion in the first 24 h was 14.0 +/- 6.8 U in the ARDS patients and 10.6 +/- 7.3 U in the other patients (P = 0.17); the differences remained non-significant in the following days. During the first 24 h, patients who developed ARDS received more fresh frozen plasma than those who did not (21.8 +/- 10.6 U vs. 10.7 +/- 14.7 U, P = 0.02). Patients who developed ARDS had lower PaO2/FiO2 ratios (114 +/- 61 mmHg vs. 276 +/- 108 mmHg, P = 0.01), lower arterial pH (7.27 +/- 0.10 vs. 7.34 +/- 0.11, P = 0.06) and higher minute volume (10.6 +/- 2.8 L min(-1) vs. 7.9 +/- 1.8 L min(-1), P = 0.03) than patients without ARDS. Multivariable analysis retained thoracic trauma and hypoxaemia during the first 24 h (but not multiple transfusions) as independent risk factors for ARDS. Conclusions: In this retrospective study, the development of ARDS in massively transfused patients was less related to poly-transfusion than to other factors related to circulatory shock, polytrauma or thoracic trauma. Thoracic trauma and a low PaO2 during the first 24 h were identified as independent risk factors for ARDS.