In this study we have evaluated 32 patients who underwent open heart surgery with extracorporeal circulation. The aim of the study was to determine the influence of duration of surgical procedure, amount of bleeding after surgery, duration of assisted ventilation, need for mechanical and pharmacological assistance on the occurrence of complications in the early postoperative period. Sixteen patients who developed signs of systemic infection were evaluated. Other 16 patients had similar clinical characteristics and they were operated on the same day or within the same week as patients in the first group and they served as the controls. There was a statistically significant difference between those two groups in the duration of surgical procedure, amount of blood loss after surgery, amount of transfusions and duration of mechanical ventilation. The group of patients with systemic infection and other complications required in the majority cases left ventricular support and developed multiorgan system failure that resulted in a higher rate of mortality. In conclusion, this study shows that the causes of complications and systemic infection in the early postoperative period could be due to a greater blood loss following surgery, demand for blood transfusions and duration of mechanical ventilation.