What is the amount of blood required for a transfusion in a 3-year-old pediatric patient?

Blood Transfusion Volume for a 3-Year-Old Child

For a 3-year-old child requiring red blood cell transfusion, administer 10 mL/kg of packed red blood cells, which will increase hemoglobin by approximately 20 g/L (2 g/dL). 1, 2

Calculating Transfusion Volume

Standard Dosing Formula

• Blood should always be prescribed by volume (mL/kg) rather than units in pediatric patients to ensure accurate dosing 1, 2
• The standard transfusion volume is 10 mL/kg of packed red blood cells 1, 2
• For a typical 3-year-old weighing approximately 14-15 kg, this translates to 140-150 mL of packed red blood cells 1, 2

Expected Hemoglobin Response

• Each 10 mL/kg transfusion increases hemoglobin by 20 g/L (2 g/dL) 1, 2, 3
• The expected hematocrit increase is approximately 6% per 10 mL/kg transfused 2
• This formula applies consistently across pediatric patients older than 3 months of age 1

Alternative Calculation Method

If you need to calculate a specific hemoglobin increment, use this formula: 3

Volume (mL) = Weight (kg) × Desired Hb increment (g/dL) × 3 / (Hematocrit of RBC unit)

• With standard UK/US packed red blood cells (hematocrit 0.6), this simplifies to: Weight × Desired increment × 5 3
• This formula has been validated in pediatric intensive care settings with 379 transfusion episodes 3

Critical Safety Considerations

Volume Overload Risk

• A 3-year-old has an estimated blood volume of 70-75 mL/kg (approximately 1000-1125 mL total for a 14-15 kg child) 4
• The standard 10 mL/kg transfusion represents approximately 13-14% of total blood volume, which is generally safe but requires monitoring for hypervolemia 2, 4
• Children are at particular risk for electrolyte imbalance and hypothermia during rapid blood product administration 1

Transfusion Rate

• Typical infusion rate is 10-20 mL/kg/hour (30-60 minutes for the calculated volume) 1
• Use a 170-200 μm filter giving set for red blood cell transfusion 1

Monitoring Requirements

• Measure hemoglobin before and after every unit transfused along with clinical assessment 1
• Hemoglobin measured at 1 hour post-transfusion is equivalent to 7 hours post-transfusion, so early assessment is reliable 3
• Children have higher rates of serious adverse transfusion events compared to adults, requiring careful monitoring 2

Transfusion Thresholds for 3-Year-Olds

Hemodynamically Stable Patients

• Apply a restrictive transfusion strategy for children older than 3 months 1
• The general threshold for stable pediatric patients is hemoglobin <70 g/L (7 g/dL) 1, 5

Clinical Context Modifications

• Acute blood loss or unstable patients: Consider transfusion at hemoglobin 78-80 g/L (7.8-8.0 g/dL) 5
• Patients requiring high FiO₂ (>0.6) or inotropic support: Use higher thresholds around 80 g/L (8.0 g/dL) 5
• Hematologic conditions: May transfuse at lower thresholds around 70 g/L (7.0 g/dL) 5

Common Pitfalls to Avoid

• Never order "1 unit" of blood for a 3-year-old—always calculate and prescribe the specific volume in mL 1, 2
• Do not use adult transfusion volumes—pediatric physiology requires weight-based calculations 1, 6
• Avoid rapid transfusion without warming—children are particularly susceptible to hypothermia 1
• Do not assume higher is better—restrictive strategies are appropriate for most stable children and reduce donor exposure 1