Background: Severe hemorrhage is a common complication of cardiac surgeries, particularly those performed via cardiopulmonary bypass. Perioperative hemorrhage shows a spectrum of severity, with excessive bleeding being documented in 2% to 11% of patients. Cardiopulmonary bypass (CPB) is the primary cause of intraoperative hemorrhage. Objective: improvement of outcome in cases undergoing elective cardiac surgery on cardio-pulmonary bypass by reducing blood products transfusion. Material and methods: Rotational Thromboelastometry, long cardiopulmonary bypass term and Adult Cardiac Surgeries were searched for in PubMed, Google Scholar, and The Egyptian Knowledge Bank. Only the most current or comprehensive studies were included after the authors thoroughly filtered references from the pertinent literature, which comprised all the recognised studies and reviews. Documents written in languages other than English have been ignored due to a lack of translation funds. Unpublished works, oral presentations, conference abstracts, and dissertations were generally agreed upon not to qualify as scientific research. Conclusion: Long cardiopulmonary bypass term, the greatest predictor of microvascular bleeding, is a distinct risk factor for development of death rate and illness following cardiac operation. Bleeding risk increases when the CPB duration exceeds 120 minutes. Clotting factor loss can also occur as a consequence of intraoperative cell-saving devices. Fibrinolysis is also induced by platelet dysfunction and clotting factor degradation, as plasminogen activation during CBP and heparinization both contribute to this process.  Hypothermia may impair the function of platelets and enzymes. Platelet adhesion and aggregation are inhibited at body temperatures below 33 °C.