Effects of anemia and blood transfusion on clot formation and platelet function in patients with septic shock: a substudy of the randomized TRISS trial

BACKGROUND: The effects of anemia and red blood cell (RBC) transfusion on markers of clot formation and platelet function in patients with septic shock are unknown. We assessed these effects in a randomized transfusion trial of patients with septic shock. STUDY DESIGN AND METHODS: We performed a prospective substudy of the Transfusion Requirements in Septic Shock (TRISS) trial, randomly assigning patients in the intensive care unit with septic shock and hemoglobin concentration of 9.0 g/dL or less to transfusion with one unit of RBCs at a hemoglobin level of 9.0 g/dL or a level of 7.0 g/dL. We assessed thromboelastography (TEG), multiple electrode aggregometry (MEA), platelet count, and international normalized ratio (INR) immediately before and after the first blood transfusion and again 3 hours after. The effects of hemoglobin level were analyzed using multiple linear regression and the association between markers of hemostasis and subsequent bleeding by Cox regression models. RESULTS: We included 58 patients in this substudy. We observed no differences in whole blood clot formation, platelet count or function, or INR between patients with hemoglobin levels of 7.0 and 9.0 g/dL, and we found no effect of RBC transfusion on these markers. Platelet function, assessed by MEA, but not whole blood clot formation, was associated with subsequent bleeding. CONCLUSIONS: In patients with septic shock, the level of anemia and the transfusion of RBCs did not appear to influence clot formation or platelet function. Low platelet function, as evaluated by MEA, was associated with increased risk of subsequent bleeding.