Preoperative autologous blood donation: benefit or detriment? A mathematical analysis

Advocates of preoperative autologous blood donation (PABD) often fail to consider the needs of individual patients and the effects of donation on hematocrit. Mathematical modeling is used here to analyze PABD.

A model of PABD was constructed to simulate the transfusion of red cells once a predetermined minimum hematocrit was reached. Preoperatively deposited units not needed to maintain a hematocrit at this level were not transfused. Final hematocrits were compared to the hematocrit that would be expected if the patient had not donated blood for his or her own operative use.

For many patients, particularly those with normal initial hematocrits, large estimated blood losses must occur before the minimum hematocrit is reached. It is also known that patients donating multiple units typically cannot maintain their baseline hematocrit. In such cases, for blood losses of any volume, the final hematocrit was lower if units were collected preoperatively and transfusion did not occur. Preoperatively donating patients are more likely to be transfused earlier and more frequently than nondonating patients. Derived figures, based on individual patient values, help predict which patients will benefit most from PABD.

PABD may actually lead to decreased postoperative hematocritis (with enhanced risk of ischemia) and otherwise unnecessary transfusions.