Open-heart surgery frequently results in abnormal clotting, which in turn results in excessive blood loss and the need for transfusion of multiple blood products to patients and leads to adverse outcomes. Prompt identification of any clotting abnormalities after cardiac surgery reduces blood loss and blood product transfusion and may improve outcomes. Currently, however, this monitoring is dependent on standard laboratory-based tests of clotting that have a long turnaround time (30-45 min) and do not measure some important aspect of clotting. There are now other monitoring options that are carried out at patients’ bedside, providing results more quickly than standard laboratory tests (within 2-5 minutes for some), and measure more aspects of clotting, providing more information on possible causes of any abnormalities. In this study, we will compare the cost-effectiveness of two of these newer monitoring techniques with standard laboratory-based tests by assigning 150 patients who will be undergoing open-heart surgery to one of the three monitoring techniques (50 patients will be assigned by chance to each group). In each group, an explicit algorithm based on the monitoring technique of that group will be used to guide all transfusion decisions. Between-group differences in number of units of blood products transfused (primary outcome), amount of blood loss, rate of adverse events, and cost of monitoring will be measured. The objective of the study is to determine which of the three methods is most cost-effective in terms of these outcomes.