In 2001, Spiess referred to current transfusion practice as a 'silent epidemic'. His description is still accurate. In 2006, almost half of all patients undergoing coronary artery bypass grafting in the united states received blood transfusion and the probability of receiving blood is greater when procedures are more complex. Although the infectious risk of blood transfusion have been successfully minimised the weight of evidence increasingly suggests that transfusing less in stable patients could prevent a significant amount of morbidity and mortality. This study will help guide management in those in whom transfusion is avoidable.