BSA Calculation: 1.42 m²
For a patient weighing 45.5 kg and height 155 cm, the body surface area (BSA) is approximately 1.42 m².
Calculation Method
The most widely validated and recommended formula for BSA calculation is the DuBois and DuBois formula, which has been extensively referenced in clinical guidelines and remains the standard for indexing cardiac measurements, drug dosing, and physiological parameters 1, 2.
DuBois Formula:
BSA (m²) = 0.007184 × Height(cm)^0.725 × Weight(kg)^0.425
For your patient:
- BSA = 0.007184 × (155)^0.725 × (45.5)^0.425
- BSA ≈ 1.42 m²
Alternative Formulas
While the DuBois formula is most commonly used, several alternative formulas exist with comparable accuracy:
Mosteller Formula (simplified):
- BSA = √[(Height(cm) × Weight(kg))/3600]
- BSA = √[(155 × 45.5)/3600] ≈ 1.42 m²
Haycock Formula:
- BSA = 0.024265 × Height(cm)^0.3964 × Weight(kg)^0.5378
- BSA ≈ 1.42 m²
Clinical Context
BSA is essential for:
- Indexing cardiac measurements (left ventricular mass, chamber volumes) 1, 3
- Normalizing aortic dimensions - particularly important as BSA is the most used method to normalize aortic measurements, with ascending thoracic aorta >22 mm/m² considered dilated 2
- Drug dosing calculations - especially chemotherapy and critical care medications 4
- Assessing burn extent - using Lund and Browder charts 4
- Dialysis adequacy calculations 5, 6
Important Caveats
Limitations at extremes of body habitus: BSA formulas may be less accurate in patients with:
- Severe obesity or malnutrition 5, 6
- Extreme body compositions (very high or low body fat percentage) 7
- Amputations - require adjustment factors 5
For this patient with BMI ≈ 19 kg/m² (normal range), the standard DuBois formula provides accurate BSA estimation without need for adjustment.
When indexing measurements: Consider using height-based indexing (height^2.7) rather than BSA for certain cardiac parameters in patients at extremes of body size, as the relationship between BSA and body volume is not linear 1.