About the Pediatric Blood Transfusion Volume Calculator
This calculator estimates the volume of packed red blood cells (PRBCs) needed to raise a child's hematocrit from a current level to a target level. It uses a standard blood-volume formula built from the patient's weight, an age-appropriate estimate of total blood volume, and the hematocrit of the donor unit being transfused.
How the volume is calculated
The calculation has two steps:
- Estimate total blood volume: Blood volume (mL) = weight (kg) x a blood-volume factor in mL/kg. Neonates and infants carry more blood per kilogram (roughly 85 mL/kg) than older children (about 80 mL/kg) or adolescents approaching adult size (about 70 mL/kg).
- Solve for transfusion volume: Volume (mL) = Blood volume (mL) x (Target hematocrit - Current hematocrit) / Donor unit hematocrit. Stored packed red cell units typically have a hematocrit around 55-65%, so a default of 60% is used unless the blood bank reports a different figure for the specific unit.
Dividing the resulting volume by the patient's weight gives mL/kg, which is the unit most transfusion protocols use to describe a dose and to compare against typical single-session limits.
Reading the result
Most pediatric transfusion protocols aim for roughly 10-15 mL/kg of packed red cells per session, infused over 2-4 hours, to reduce the risk of transfusion-associated circulatory overload. If the calculated volume exceeds that per-kilogram range, clinicians often split the total into two sessions or slow the infusion rather than giving it all at once, particularly in infants or children with cardiac or renal disease.
When to consult a professional
This tool performs the standard volume arithmetic for planning and education. It does not replace a clinician's order, a blood bank's product-specific hematocrit, or a hospital's transfusion protocol. Any decision to transfuse, the product ordered, and the infusion rate should be confirmed with the treating physician and blood bank.