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Donor base management: painting Gabriel's horn – Comment on Beckman et al., 2016

Surprisingly, over the past decade, the total demand for red blood cell (RBC) units has dropped by 20–30% in Canada, the United States, Australia and Europe. The surprise is in the fact that, if anything, a rise in RBC use had been predicted (Williamson & Devine, 2013). Beckman et al. have described this situation and some of its consequences for Australia, Canada and the United States in this journal (Beckman et al., 2016). Moreover, they reason that the proportional use of RBC units of the blood group O-negative (Oneg) and cytomegaly virus (CMV)-negative units have increased. They show that, in contrast to Australia, in the United States, the absolute use of Oneg units has also decreased. The authors argue that the trend in RBC demand will raise the costs for Oneg donor recruitment and warrants reflecting on Oneg use. Appealingly, they used the metaphor of Gabriel’s horn paradox to describe the trend that, although the total demand can be met with a finite stock, differential demand will prevent meeting all individual demand. Gabriel’s horn (also called Torricelli’s trumpet) is a geometric figure that has infinite surface area but finite volume (https://en.wikipedia.org/wiki/Gabriel%27s_ Horn). Gabriel’s horn paradox is also known as the ‘painter’s paradox’: to fill Gabriel’s horn, you need a finite amount of paint; however, the surface area of the very same horn has an infinite size, challenging the way to paint all of its inner surface. What has happened? The emphasis on patient blood management in elective situations – especially cardiovascular and orthopaedic surgery – has been a main driver for the decline in RBC use. Preoperative assessment of anaemia, improved surgical techniques, reusing of perioperative blood loss and rationalising patients’ needs are the mainstays of lowering the demand of RBC units. In all of these cases, the patients’ blood group is known. In contrast, stricter guidelines on blood group matching enforced by regulations and authorised protocols in many countries have indeed presented a driver for a rise in Oneg RBC use. In particular, when the patient’s blood group cannot be assessed in due time, guidelines force the medical team to transfuse Oneg RBC units. To our knowledge, the number of such acute situations – the majority being trauma patients and unexpected massive bleedings as encountered in (aortic) vessel ruptures – has not increased or decreased (much) over the past decade in the developed world and accounts for only about 4% of RBCs transfused. However, a large, absolute change in Oneg RBC use