Red blood cells (RBCs) are stored up to 35-42days at 2-6°C in blood banks. During storage, the RBC membrane is challenged by energy depletion, decreasing pH, altered cation homeostasis, and oxidative stress, leading to several biochemical and morphological changes in RBCs and to shedding of extracellular vesicles (EVs) into the storage medium. These changes are collectively known as RBC storage lesions. EVs accumulate in stored RBC concentrates and are, thus, transfused into patients. The potency of EVs as bioactive effectors is largely acknowledged, and EVs in RBC concentrates are suspected to mediate some adverse effects of transfusion. Several studies have shown accumulation of lipid raft-associated proteins in RBC EVs during storage, whereas a comprehensive phospholipidomic study on RBCs and corresponding EVs during the clinical storage period is lacking. Our mass spectrometric and chromatographic study shows that RBCs maintain their major phospholipid (PL) content well during storage despite abundant vesiculation. The phospholipidomes were largely similar between RBCs and EVs. No accumulation of raft lipids in EVs was seen, suggesting that the primary mechanism of RBC vesiculation during storage might not be raft -based. Nonetheless, a slight tendency of EV PLs for shorter acyl chains was observed.

SUMMARY Objectives The current trends in RBC use and pre‐ and post‐transfusion Hb levels were analysed to improve practice and to provide international comparison. Background Indications for RBC transfusion have changed with growing scientific evidence. The lowest acceptable haemoglobin (Hb) level has decreased, and transfusing single units instead of pairs has become the new standard. Evidence‐based guidelines and patient blood management (PBM) programmes increase clinician awareness of rational RBC use. In Finland, however, no formal PBM programme has been established to date. Methods The study was registry‐based, retrospective and observational. All RBC transfusions for adult patients from 2011 to 2016 in the southern region of Finland were analysed. Results RBC usage decreased from 34·9 to 27·5 units per 1000 population (P < 0·001). The percentage of single‐unit transfusions increased from 57·9 to 66·7%, and the median pre‐ and post‐transfusion Hb levels decreased from 8·4 to 8·2 g dL−1 (P < 0·001) and 9·9 to 9·6 g dL−1 (P < 0·001), respectively. The proportion of transfusions with pre‐transfusion Hb ≥ 9·0 g dL−1 decreased during the study period but remained high, being 29·5% in 2011 and still 25·2% in 2016. Conclusions Consumption of RBCs has decreased despite aging population and increasing healthcare performance demands. The results indicate more rational and evidence‐based RBC use. Nevertheless, the transfusion rate and pre‐ and post‐transfusion Hb are still sufficiently high to enable more restrictive transfusion practice.