Pediatric Blood Volume Calculation
The estimated blood volume in pediatric patients ranges from 70-100 mL/kg, with newborns having higher volumes (up to 100 mL/kg) and older children averaging around 70 mL/kg. 1, 2
Age-Specific Blood Volume Estimates
Blood volume varies significantly by age:
- Term Neonates: 85-100 mL/kg 1
- Young Infants (0-6 months): 80-85 mL/kg 1
- Older Infants (6-24 months): 75-80 mL/kg 1
- Children (2-11 years): 75 mL/kg 1
- Adolescents (11-18 years): 70-75 mL/kg 1
- Adults: 70 mL/kg 1
Clinical Applications
Transfusion Calculations
- A transfusion of 10 mL/kg of red blood cells should increase hemoglobin by approximately 20 g/L (2 g/dL) 2
- Expected Hb rise can be calculated using: Hb rise (g/dL) = Volume transfused (mL/kg) ÷ 5 2
Fluid Resuscitation
- For hemorrhagic shock, initial blood product dosing should be calculated based on the estimated blood volume:
Practical Considerations
Blood Sampling
- Blood draws for laboratory testing should be carefully calculated to avoid iatrogenic anemia
- For most children up to 3 years old, blood draws should not exceed 1 mL/kg body weight 3
- For blood cultures, weight-based sampling is recommended:
- <11 kg: 1-1.5 mL
- 11-17 kg: 7.5 mL 4
Massive Transfusion Protocol
- During active hemorrhage, use a 1:1:1 ratio of RBCs:FFP:platelets 2
- Blood should be prescribed in volume (mL) rather than units for pediatric patients 1
- Monitor for electrolyte imbalances and hypothermia during rapid blood product administration, as children are particularly susceptible 1
Common Pitfalls
- Overestimation in older children: Using 80-85 mL/kg for all pediatric patients can lead to overestimation in older children and adolescents
- Underestimation in neonates: Using adult values (70 mL/kg) for neonates can lead to inadequate resuscitation
- Failure to adjust for clinical context: Blood volume may be affected by underlying conditions (dehydration, heart disease, etc.)
- Not accounting for weight-based differences: Always calculate blood product volumes based on the patient's weight rather than using standard adult units
Blood volume estimation is essential for appropriate fluid management, transfusion therapy, and medication dosing in pediatric patients. Using age-appropriate estimates helps optimize outcomes and reduce complications.