Calculating the required transfusion volume in children

The traditional method of calculating blood volume for pediatric transfusion in the UK is weight (kg) x aimed increment in hemoglobin concentration (Hb; g/dL) x the transfusion factor, usually quoted at 3 or 4. This equation is without evidence base. The aim was to assess how the volume of red cells (RBCs) affects the increase in serum Hb in children and to devise a formula that allows accurate volume calculation.

All pediatric intensive care charts for 2 years were examined retrospectively. The immediate pre- and posttransfusion Hb estimations and the precise volumes of RBC transfused were recorded. Fluid boluses and hemorrhagic loss during the transfusion were documented.

A total of 7679 patient charts were examined with a total of 564 transfusions. All patients who were bleeding, had drain losses, or had concurrent colloid infusions were excluded, giving 379 data points. The correlation gradient between mL per kg blood transfused and increase in Hb was 5.02. There was no significant association between effect and patient weight, age, starting Hb, transfusion time, or sex. No significant difference was found in Hb at 1 and 7 hours posttransfusion.

The following equation should be used to calculate transfusion volumes: weight (kg) x increment in Hb (g/dL) x 3/(hematocrit [Hct] level of RBCs). This predicts that with a UK standard Hct of 0.6, 10 mL/kg gives an increment of 2 g/dL. Care must be taken not to risk hypervolemia, while minimizing donor exposure. Hb estimation 1 hour after transfusion is the same as 7 hours after transfusion.