These observations offer an interpretation for the well-known deleterious effects of excessive hemodilution during CPB, supported by many studies where an association between nadir hematocrit (HCT) on CPB and bad outcomes (especially renal) was found (6-8). It is reasonable to hypothesize that a low oxygen delivery may determine an ischemic damage to the kidney, that due to its peculiar circulation is particularly susceptible to a decrease in the oxygen supply.