Intraoperative bleeding: a mathematical model for minimizing hemoglobin loss.

Background: The rationale for intraoperative blood transfusion is often based on incorrect concepts and criteria.

Study Design And Methods: A mathematical model based on physiologic measures and describing the usual pattern of surgical blood loss is presented, and a theoretical means of minimizing intraoperative hemoglobin loss with hypervolemic hemodilution is proposed.

Results: Intraoperative hemoglobin loss is often overestimated especially in connection with high-volume blood loss. The model of intraoperative hypervolemic hemodilution shows significant improvement in hemoglobin concentration in the immediate postoperative period, compared with normovolemic conditions. The difference is most marked at a high volume of blood loss and a high degree of maintained hypervolemia.

Conclusion: The practice of intraoperative blood transfusion according to volume of blood lost is to be discouraged, and regular monitoring of the hematocrit is necessary to avoid unnecessary transfusion. The theoretical advantages of hypervolemic hemodilution warrant further testing of the model in a clinical setting.