A b s t r a c tBackground: Commonly used cardiopulmonary bypass systems with cardiotomy reservoir, oxygenator, and roller pump require preoperative crystalloid filling. Radical reduction of the filling fluid volume and replacing it with the patient's own blood has a fundamental impact on the outcome. Aim:A comparison of cardiopulmonary bypass filled with the patient's blood, applied in Poland for the first time, and the classical system filled with crystalloids.Methods: Non-randomised trial in which patients undergoing coronary artery bypass grafting were divided into two groups: first operated on with use of cardiopulmonary bypass system with the patient's own blood priming, and a control group operated on with standard technique. Levels of haemoglobin (HGB), haematocrit (HCT), platelets, leukocytes, creatinine, protein, C-reactive protein, procalcitonin, volume of transfused blood products, postoperative drain output, time to extubation, and consumption of catecholamines were compared. Results:The results of a study comparing the classical system with the blood-filled system (n = 60) showed a significantly smaller decrease in HGB and HCT levels (p = 0.001), resulting in reduction of blood product transfusions by 75% (p = 0.03). The new type of extracorporeal circulation reduced the total postoperative drain output by approximately 28% (p = 0.003). The systemic inflammatory response syndrome (SIRS) was less pronounced and the tissue perfusion was better due to smaller degree of haemodilution leading to better organ and heart protection. The patients required shorter mechanical ventilation times in the perioperative period. Conclusions:The use of a new system of cardiopulmonary bypass filled with the patient's blood reduces the postoperative decrease in HGB and HCT, the amount of transfused blood products, and total postoperative drain output. It also shortens the time spent on mechanical ventilatory support.