A process developed since 1970 with the aim of avoiding blood transfusions in patients who do not want to use allogenic blood (donor), either for religious or personal reasons. It must be performed since, although the management of blood is highly safe, it is not exempt from complications, be they immunological, infectious or caused by the so–called “deposit disease“ (where the stored blood undergoes changes in its cytoskeleton becoming less deformable and more fragile, breaking easily). It is performed by removing blood from the patient as soon as he is anesthetized and infusing physiological serum in the proportion of 3:1, thus maintaining a volume of liquid that keeps the arterial pressure in normal values. This removed blood remains in the operating room and is returned to the patient when the surgery is finished.