The incidence of infective endocarditis (IE) is approximately 15 in 100,000 and is increasing. This rise is related to the use of cardiac implants [
1]. Survival after cardiac valve implants can be long, during which there is a low but continuous risk for the development of prosthetic valve IE [
1] or for other comorbid conditions such as colorectal neoplasia, which can serve as port-of-entry for bacteremia and subsequent IE [
2]. Mortality of IE can be up to 20% in the first month and 30% at 6 months [
3]. In some patients, cardiac surgery is required because of persisting sepsis, intracardiac tissue destruction, hemodynamic deterioration [
4] or persisting vegetation with risk for septic emboli. The optimal timing of surgery remains a major challenge. For routine cardiac surgery, 20% to 40% of the patients require transfusion [
5]. In complex cases, the transfusion rate is higher [
6], especially with repeat surgery, urgent surgery during ongoing sepsis, or prolonged cardiopulmonary bypass (CPB) time because of intracardiac damage. In all these conditions, there is a risk for with subsequent increase in surgical bleeding, which affects need for transfusion. IE itself has also an effect on coagulation: IE activates the primary precursors of the coagulation cascade. This leads to an increased reactivity of platelet and to the propagation of enhanced coagulation because of a decreased fibrinolysis [
7]. Moreover, elevated fibrinogen levels are often documented in the acute phase of infection and inflammation [
8]. This hypercoagulable state has been observed through laboratory parameters [
9]. A viscoelastic testing by rotational thromboelastometry can be used to direct preoperative supplementation of fibrinogen in patients with IE needing cardiac reoperation. A good understanding of the coagulation status is necessary, to avoid unnecessary transfusion. Nevertheless, measurement of INR, PT and aPTT are not helpful while the patient is still on heparin. A blood count (RBC, platelets) may indicate the need for transfusion, but such a count does not supply information concerning the platelet function. Measurement of plasma fibrinogen might be useful [
10]. Transfusion itself has also serious adverse effects in 1.1%, of the recipients [
11], but this may be underreported. A relation between the number of transfused units and 30-day morbidity and mortality rate was documented [
12]. Examples were transfusion-related acute lung injury [
13] and infections [
14], even after attempts of removal of white blood cells [
15,
16]. Compared to a liberal transfusion policy, a restricted transfusion policy was associated with less time in the intensive care unit, a shorter mechanical ventilation time, and a reduced length of stay in the hospital [
17]. There are several pathophysiologic processes that occur progressively during RBCs aging in cold storage: accumulation of lactic acid, formation of methemoglobin, and of reactive oxygenated compounds, denaturation and precipitation of hemoglobin degradation products, and a reduced cytoskeletal deformability [
18]. These changes reduce the capacity of the RBC pass through narrow vessels and to deliver oxygen effectively. Moreover, a median of 17.6% of the transfused allogeneic RBC are removed from the recipient’s circulation, either by spontaneous destruction or by phagocytosis [
19]. This contributes to acidosis, hyperkaliemia, high levels of free heme, and oxidized iron. Patients could become more vulnerable to postoperative acute renal injury, arrhythmias and infection [
18]. This problem is illustrated in one series of cardiac surgical patients: those receiving older RBCs were more likely to suffer systemic infection and fatality, compared to those who received more recently stored blood [
20]. These effects would not be expected with autologous whole blood collection with short storage time. Avoidance of these adverse transfusion should be attempted in patients with IE, which are uniquely vulnerable. The research questions are: can the need for transfusion be predicted in patients undergoing cardiac surgery for IE and what are the consequences of blood transfusion in these patients