Sanne de Bruin

212 Chapter 9 10 g/dL) for the primary outcome: major adverse cardiovascular event and/or all-cause mortality 4 . In addition, patients allocated to a restrictive transfusion strategy devel- oped less infections and less acute lung injury. A second RCT in anaemic patients with myocardial ischemia is currently recruiting patients, (MINT, NCT02981407), comparing the same transfusion strategies. If both the MINT and the REALITY can show the safety of a Hb trigger of 8 g/dL, this would be a major change in current transfusion practice. After implementation of a more restrictive transfusion strategy for these patients, the next step could be to assess the safety of an even lower transfusion trigger of 7 g/dL. Currently a transfusion trigger of 7 g/dl is considered restrictive, but no studies have assessed lower thresholds yet. Therefore, it remains unclear what the optimal Hb level trigger is. The threshold of 7 g/dL is partly determined from data in studies on Jehovah witnesses who refuse blood transfusion for religious reasons. In these patients, a higher mortality andmorbidity rate was observedwhen Hb levels dropped below 7 g/dL. Due to the retrospective character of these data, these conclusions might be confounded. One of the most likely confounding factors is that patients who are more severely ill more often developed a severe anaemia. We could also state that despite a low Hb level, still a large proportion of the patients survived without major complications. Furthermore, in resting healthy volunteers, it is shown that inducing an acute isovolumic anaemia of 5 g/dL by acutely removing blood did not result in impaired critical oxygen delivery, which was assessed by oxygen consumption (VO 2 ), lactate levels and ST changes on electro- cardiogram 5 . This suggest that there is room to investigate, preferably in a stepwise manner, if a Hb transfusion trigger lower than 7 g/dL is safe in patients. To do so, the first step is to identify patients who are most likely to benefit from a more restrictive strategy. We would argue that non-bleeding female patients could be the first subpopu- lation transfused at lower Hb levels. Under normal conditions women have significantly lower Hb levels (12-16 g/dL) than men (14-18 g/dL). Consequently, women are used to lower Hb levels thanmen, and therefore theymight bemore resilient to lower Hb levels. We found that Hb level remains themost important RBC transfusion trigger. While other RBC transfusion triggers than Hb levels such as hypotension, tachycardia and increased lactate levels are commonly used according to our surveys from chapter 2 and 3 , this was not the case in our single centre study in chapter 4 . In only two out of seventeen RBC transfusion events in this study, tachycardia and increased lactate levels played a role in the decision to transfuse the patient. Due to the small sample size in this single centre study, it is not possible to generalize these findings. Therefore, the use of other transfusion triggers will be studied in a larger population of patients inmultiple centres. This large international study is currently recruiting patients, in succession to the pilot