Intraoperative pediatric blood transfusion therapy: a review of common issues. Part II: transfusion therapy, special considerations, and reduction of allogenic blood transfusions.

Massive blood transfusion is defined as the loss of one or more circulating blood volumes. It is, therefore, important to calculate the patient’s estimated blood volume (EBV) and to relate this to the volume of blood products and other fluids administered (Table 1). In addition the anesthesiologist should estimate how much blood will be allowed to be lost before the initiation of packed RBC transfusion. The patient’s EBV is generally related in part to the patient’s age as well as body habitus. Younger patients have a higher fraction of their weight as blood while more obese patients have a lower fraction. Once the patient’s circulating blood volume has been estimated then a further simple calculation allows estimation of the maximal allowable blood loss (MABL). A simple mathematical calculation is: