Sanne de Bruin

166 Chapter 6 is that RBCs with a different phenotype were immediately captured in the spleen and were thus not represented in the blood samples after transfusion. In this study we showed that the metabolic profile is better in fresh RBCs and second, after two days the PTR of fresh RBCs is higher than longer stored RBCs. Better pres- ervation of 2,3-DPG levels could potentially increase the capacity of RBCs to transport oxygen. This has several potential clinical benefits: improved preservation of 2,3-DPG levels could potentially increase the capacity of RBCs to transport oxygen. Furthermore, compared to 35 day old RBCs, fresh RBCs were shown to have higher levels of PPP metabolites up to 1 day post transfusion (despite similar G6PD activity), suggestive of an increased overall antioxidant potential. In addition, increased PTR could reduce the number of RBC transfusions, reducing harmfull side-effects and costs. However, in crit- ically ill patients, it is shown that transfusion of fresh RBCs does not improve outcome compared to longer stored RBCs 40–42 . Nonetheless, for patients with a long termdepen- dency on RBC transfusion due to chronic blood disorders such as sickle cell anemia and thalasemia, it would be beneficial to increase the interval between transfusions. We hypothesize that in these patients, transfusion of fresh RBC could increase the interval between RBC transfusion resulting in a reduced number of transfusions in the longterm, and thereby limiting long term side effects of transfusion including iron overload. This study has various strengths including the use of an autologous transfusion in healthy volunteers. Using this approach, we ensured that each volunteer served as their own control and we thereby excluded the immunological effects of antigenmismatched blood. The most important limitation of this study is that the PTR was not assessed in the first 10 minutes after transfusion. It is therefore unknown whether transfused RBCs are cleared in the first 10minutes. Subjects received a 2 days stored and a 35 days stored RBC concentrate simultaneously. We calculated the distribution of the two populations in the RBC concentrate and the distribution of the transfused products in the recovered RBCs after transfusion. If a difference in the ratio before and after transfusionwas found, this would suggest that one population was cleared faster than the other. As 35-days stored RBCs suffer more metabolic damage from storage than 2-days stored RBCs, we expected increased clearance of the 35-days stored RBCs. On an individual level, differ- ences were found between the ratio in the transfusion product and the ratio in the re- covered RBCs after transfusion. But on group level, no statistically significant difference was found to indicate a relatively faster clearance of 2 days or 35 days stored RBCs in the first 10 minutes. However, it is possible that our study was not sufficiently powered to detect these differences. A more precise method to estimate clearance in the first 10 min would be to precisely assess circulating volume, followed by calculation of the