Plasma Volume in an 11-Year-Old Child
For a healthy 11-year-old child, plasma volume is approximately 40-45% of total blood volume, which translates to roughly 900-1,200 mL depending on the child's weight (typically 12-35 kg in this age range). 1
Total Blood Volume Calculation
The foundation for determining plasma volume starts with total blood volume:
- Children aged 2-11 years have a circulating blood volume of approximately 75 mL/kg 1, 2
- For an 11-year-old at the upper end of this range (around 35 kg), total blood volume would be approximately 2,600 mL 1
- For a smaller 11-year-old (around 25 kg), total blood volume would be approximately 1,875 mL 2
Plasma Volume Derivation
Plasma volume constitutes approximately 55% of total blood volume, with the remaining 45% being cellular components (primarily red blood cells). 3
Using the weight-based approach:
- Lower range: A 25 kg child with 1,875 mL total blood volume → plasma volume ≈ 1,030 mL
- Upper range: A 35 kg child with 2,600 mL total blood volume → plasma volume ≈ 1,430 mL
Important Clinical Considerations
Individual Variation Factors
The 75 mL/kg estimate does not account for several critical variables that affect actual plasma volume 2:
- Hydration status: Dehydration reduces plasma volume disproportionately to red cell mass
- Body composition: Children with higher lean body mass have proportionally greater plasma volumes 3
- Training status: Endurance-trained children may have 10-15% higher plasma volumes than sedentary peers 4
- Pubertal stage: Children entering puberty (common at age 11) may show transitional values between childhood and adolescent ranges 3
Normalization to Lean Body Mass
Lean body mass (LBM) is the most accurate anthropometric parameter for predicting plasma volume, showing no significant variation by sex or pubertal stage 3. This is superior to simple weight-based calculations because it accounts for differences in body composition that become increasingly important around age 11 as puberty begins.
Clinical Applications
When calculating safe blood draw volumes or assessing fluid requirements:
- Always use weight-based calculations rather than age-based estimates alone 2
- For blood product dosing, fresh frozen plasma is dosed at 10-15 mL/kg, which represents approximately 13-20% of total plasma volume in this age group 2
- Each percentage of blood volume lost represents a more significant physiologic insult in children compared to adults due to smaller absolute volumes 2
Transition to Adolescent Values
At age 11, some children (particularly those entering puberty early) may already be transitioning to adolescent blood volume estimates of 70-75 mL/kg 1, 2. This represents the lower end of the range and should be considered for more physically mature 11-year-olds, which would yield proportionally lower plasma volumes (approximately 850-1,100 mL for a 35 kg adolescent).