A mathematical model of cell salvage compared and combined with normovolemic hemodilution

Mathematical models have been used to describe the factors that affect cell salvage (CS) and normovolemic hemodilution (ANH). Here, the CS and ANH models were used to compare these two techniques alone or in combination with each other.

Variables used for a hypothetical patient included an estimated blood volume of 5000 mL, a presurgery hematocrit (Hct) of 45 percent, and a transfusion trigger of 21 percent. The model accounts for both the effect of decreasing the Hct due to blood loss and the effect of increasing Hct due to the readministration of blood in an isovolemic patient. The efficacy of CS and ANH is defined to be the maximum allowable blood loss for a fixed blood volume and a fixed transfusion trigger.

Comparison of CS with ANH showed that 3 units of ANH was comparable to CS when CS recovery rates ranged from 19 to 24 percent. For a patient with a blood volume of 5000 mL and a starting Hct of 40 percent, 3 units of ANH would allow for 3972 mL of blood to be lost before crossing a 21-percent transfusion trigger, whereas CS with a 125-mL bowl would allow for 7611 mL.

When comparing ANH to CS, this mathematical model would suggest that CS has the potential to offer significantly greater red blood cell avoidance than does ANH; however, the combination of ANH with CS may offer allogeneic avoidance superior to either technique alone.