A multi-centre randomised controlled trial of Transfusion Indication Threshold Reduction on transfusion rates, morbidity and healthcare resource use following cardiac surgery (TITRe 2)

Cardiac surgery centres transfuse over 6% of all units of red blood cell (RBC) used in the UK. Although RBC transfusion is essential in some patients for the management of life-threatening haemorrhage, in most cases decisions to transfuse are made because the haemoglobin (Hb) concentration has fallen to a level or threshold at which the physician is uncomfortable. The transfusion threshold varies between units and physicians, contributing to wide variation in the percentage of cardiac surgery patients who are transfused with RBC (25% to 95%). The threshold variation stems from a lack of evidence as to what constitutes a safe level of anaemia following cardiac surgery. Unnecessary blood transfusions increase healthcare costs both directly, because blood is an increasingly scarce and expensive resource, and indirectly, due to complications associated with transfusion. Transfusion may cause complications by reducing patients' ability to fight off infection and respond to the stress that surgery puts on the body, as well as the better known, but rare complication of infection transmission. Randomised trials have suggested that, in other patient groups, only transfusing when the Hb level drops below 7.0g/dL reduces transfusion rates as well as complications. However, to date there has been no large high quality randomised trial of different transfusion thresholds in a population of cardiac surgery patients. We propose to test the hypothesis that lowering the RBC transfusion threshold from a haemoglobin (Hb) level of 9.0g/dL ("liberal") control group, similar to current practice at most centres) to 7.5g/dL ("restrictive") reduces postoperative complications and NHS costs in cardiac surgery patients. The study is a UK multi-centre, randomised controlled trial that aims to assign 2000 patients to a restrictive or liberal post-operative transfusion threshold. The primary outcome will be a composite of infectious and ischaemic events in the first three months after randomisation.