Calculating Exchange Volumes for Exchange Transfusions in a Patient with Sickle Cell Disease

 

volume in mL for manual partial exchange =

= ((hematocrit desired in percent) – (hematocrit initial in percent)) * (total blood volume) / ((hematocrit of replacement product in percent) – (0.5 * ((hematocrit desired in percent) + (hematocrit initial in percent))))

 

volume in mL for an automated exchange transfusion =

= (hematocrit initial in percent) / 100 * (total blood volume)

 

where:

• The usual hematocrit for a packed red cell product is 70-80%.

• A rough estimate of total blood volume in children is 80 mL/kg and in adults is 65 mL/kg. Males tend to have a slightly greater blood volume than females. A person at the extremes of body weight would need a more explicit equation (see Chapter 2).

• The equation for automated exchange transfusion is "(hematocrit initial) * (total blood volume)". In the footnote in Wayne et al they refer to hematocrit for packed RBCs as 0.7-0.8. I'm assuming then that (hematocrit in percent) / 100 is appropriate, else the number would be very large.