Body surface area

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In physiology and medicine, the body surface area (BSA) is the measured or calculated surface of a human body. For many clinical purposes BSA is a better indicator of metabolic mass than body weight because it is less affected by abnormal adipose mass. Estimation of BSA is simpler than many measures of volume.

1 Uses
2 Calculation
3 Normal values
4 References
5 External links

[edit] Uses

Examples of uses of the BSA:

Renal function is usually fractioned over the BSA to gain an appreciation of the true required glomerular filtration rate (GFR);
The Quetelet index uses a somewhat modified form of the BSA;
The cardiac index is a measure of cardiac output divided by the BSA, giving a better approximation of the required cardiac output;
Chemotherapy is often dosed according to the patient's BSA.
Glucocorticoid dosing is also expressed in terms of BSA for calculating maintenance doses or to compare high dose use with maintenance requirement.

[edit] Calculation

Various calculations have been published to arrive at the BSA without direct measurement:

The Dubois & Dubois formula:^[1]:

${BSA (m^2)}=0.007184 \times {weight \mbox{ (kg)}}^{0.425} \times {height \mbox{ (cm)}}^{0.725}$

or alternatively expressed:

${BSA (m^2)}=\frac{{weight \mbox{ (kg)}}^{0.425} \times {height \mbox{ (cm)}}^{0.725}}{139.2}$

One commonly used formula is the Mosteller formula, published in 1987^[2] and adopted for use by the Pharmacy and Therapeutics Committee of the Cross Cancer Institute, Edmonton, Alberta, Canada:

${BSA (m^2)}= \sqrt\frac{weight \mbox{ (kg)} \times height \mbox{ (cm)} }{3600}$

Other formulas include the Haycock formula^[3]:

${BSA (m^2)}=0.024265 \times {weight \mbox{ (kg)}}^{0.5378} \times {height \mbox{ (cm)}}^{0.3964}$

the Gehan and George formula^[4]:

${BSA (m^2)} = 0.0235 \times weight \mbox{ (kg)}^{0.51456} \times height \mbox{ (cm)}^{0.42246}$

the Boyd formula^[5]:

${BSA (m^2)} = 0.0003207 \times weight \mbox{ (g)}^{(0.7285 - 0.0188 \log_{10}{weight \mathrm{ (g)}})} \times height \mbox{ (cm)}^{0.3}$

[edit] Normal values

"Normal" BSA is generally taken to be 1.73 m² for an adult.

Average BSA values
Neonate	0.25	m²
Child 2 years	0.5	m²
Child 9 years	1.07	m²
Child 10 years	1.14	m²
Child 12-13 years	1.33	m²
For men	1.9	m²
For women	1.6	m²

[edit] References

^ Du Bois & Du Bois,Arch Intern Med 1916, 17:863
^ Mosteller RD. "Simplified calculation of body-surface area". N Engl J Med 1987; 317:1098. PMID 3657876.
^ 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, 93:62-66.
^ Gehan EA, George SL, Cancer Chemother Rep 1970, 54:225-235
^ http://www.ispub.com/journals/IJA/Vol2N2/bsa.htm (from Boyd E, The growth of the surface area of the human body. Minneapolis: University of Minnesota Press, 1935.)

[edit] External links

BC Cancer network BSA calculation guidelines.
Online Body Surface Area Calculator (Dubois Formula)
Online Body Surface Area Calculator (Mosteller Formula)
Web CoolTool to Calculate BSA using any of the five formulae

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