BACKGROUND AND OBJECTIVES: Transfusion of red blood cells (RBC) is beneficial for the patient but can also be harmful, as randomized trials have demonstrated increased infection rates, bleeding and mortality. The study aim was to investigate the response of the vascular system (the haemostatic function and the endothelium) to RBC transfusion.

MATERIALS AND METHODS: Blood was sampled from patients with various transfusion-dependent haematologic diseases before 1 and 24 h after RBC transfusion. Primary and secondary haemostasis was evaluated by whole-blood impedance aggregometry (Multiplate) and by thromboelastography (TEG). Samples were analysed by ELISA for biomarkers reflecting endothelial activation and damage (sICAM-1, syndecan-1, sThrombomodulin (sTM), sVE-Cadherin), platelet activation (sCD40L) and inflammation (hsCRP).

RESULTS: A total of 58 patients were enrolled in the study. Median age was 71 years. Compared to before transfusion, patients had slightly reduced coagulability 1 h after RBC transfusion, assessed by TEG. However, transfusion of older RBC products (>14 days) was associated with increased coagulability (all P < 0·05). The level of syndecan-1 increased slightly 24 h after transfusion (median 12·4 (IQR 9-23) vs. 13·2 (9-25) ng/ml, P < 0·01), indicating increased glycocalyx degradation.

CONCLUSION: Overall, RBC transfusion was associated with reduced coagulability and endothelial glycocalyx degradation. Transfusion of older RBCs was however associated with increased coagulability. The changes observed were small to moderate and the clinical relevance of these findings should be investigated in larger studies.