Body surface area

Body Surface Area (BSA)

Body Surface Area (BSA) is a measurement used in many medical tasks, including the calculation of drug dosages and the assessment of metabolic rates. It is a more accurate measure of metabolic mass than body weight because it is less affected by abnormal adipose mass.

Calculation Methods

Several formulas have been developed to estimate BSA, with the most commonly used being the Du Bois and Du Bois formula, the Mosteller formula, and the Haycock formula.

Du Bois and Du Bois Formula

The Du Bois and Du Bois formula, developed in 1916, is one of the earliest and most widely used formulas:

<math>BSA = 0.007184 \times Height^{0.725} \times Weight^{0.425}</math>

where height is in centimeters and weight is in kilograms.

Mosteller Formula

The Mosteller formula is a simpler approximation that is often used in clinical settings:

<math>BSA = \sqrt{\frac{Height \times Weight}{3600}}</math>

This formula also uses height in centimeters and weight in kilograms.

Haycock Formula

The Haycock formula is another method that is particularly useful for pediatric patients:

<math>BSA = 0.024265 \times Height^{0.3964} \times Weight^{0.5378}</math>

Clinical Applications

BSA is used in various clinical settings, including:

• Chemotherapy Dosing: Many chemotherapy drugs are dosed based on BSA to ensure efficacy while minimizing toxicity.
• Renal Function Assessment: BSA is used to normalize glomerular filtration rate (GFR) measurements.
• Cardiac Index Calculation: The cardiac index, which is the cardiac output divided by BSA, is used to assess cardiac function.

Limitations

While BSA is a useful measure, it has limitations. It does not account for variations in body composition, such as muscle mass versus fat mass. Additionally, the formulas are based on average body types and may not be accurate for individuals with extreme body sizes or shapes.

See Also

• Body mass index
• Lean body mass
• Surface area to volume ratio

References

• Du Bois D, Du Bois EF. "A formula to estimate the approximate surface area if height and weight be known." Archives of Internal Medicine 1916;17:863-71.
• Mosteller RD. "Simplified calculation of body-surface area." N Engl J Med. 1987 Oct 22;317(17):1098.
• Haycock GB, Schwartz GJ, Wisotsky DH. "Geometric method for measuring body surface area: A height-weight formula validated in infants, children, and adults." J Pediatr. 1978 Jul;93(1):62-6.