Hemodilution: modeling and clinical aspects

Hemodilution is defined as the dilution of the concentration of red blood cells and plasma constituents by partially substituting the blood with colloids or crystalloids and it is a strategy to avoid exposure of patients to the hazards of homologous blood transfusions. Several mathematical models and computer simulations have been introduced to validate the efficacy of hemodilution; the amount of maximal allowable blood loss and final postoperative hematocrit or hemoglobin has been calculated. The basic prerequisite for preserving tissue oxygenation during hemodilution is adequate oxygen delivery and therefore all determinants of oxygen transport should be monitored. Compensatory mechanisms such as increased cardiac output and stroke volume occur following hemodilution. When debating the use of colloid and crystalloid during fluid replacement, it is imperative to think about all of the components of the Starling equation. In order to better analyze the clinical outcome of hemodilution, more realistic mathematical models should be developed.