Body surface area - AbsoluteAstronomy.com

Physiology

Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...

and medicine

Medicine

Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

, the body surface area (BSA) is the measured or calculated surface of a human body

Human body

The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs.By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life...

. For many clinical purposes BSA is a better indicator of metabolic mass than body weight because it is less affected by abnormal adipose mass. Nevertheless, there have been several important critiques of the use of BSA in determining the dosage of medications with a narrow therapeutic index

Therapeutic index

The therapeutic index is a comparison of the amount of a therapeutic agent that causes the therapeutic effect to the amount that causes death or toxicity ....

like many chemotherapy medications. Typically there is a 4-10 fold variation in cytotoxic drug clearance between individuals due to differing activity of drug elimination processes related to genetic and environmental factors. This can lead to significant overdosing and even more perniciously to underdosing (and increased risk of cancer recurrence). It is also thought to be a distorting factor in Phase I and II trials that may result in potentially helpful medications being prematurely rejected. The trend to personalized medicine

Personalized medicine

Personalized medicine is a medical model emphasizing in general the customization of healthcare, with all decisions and practices being tailored to individual patients in whatever ways possible...

is one approach to counter this weakness. Estimation of BSA is simpler than many measures of volume.

Uses

Examples of uses of the BSA:

Renal clearance
Renal function
Renal function, in nephrology, is an indication of the state of the kidney and its role in renal physiology. Glomerular filtration rate describes the flow rate of filtered fluid through the kidney...

is usually divided by 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
Cardiac index
Cardiac index is a vasodynamic parameter that relates the cardiac output to body surface area , thus relating heart performance to the size of the individual...

is a measure of cardiac output
Cardiac output
Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...

divided by the BSA, giving a better approximation of the required cardiac output;
Chemotherapy
Chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....

is often dosed according to the patient's BSA.
Glucocorticoid
Glucocorticoid
Glucocorticoids are a class of steroid hormones that bind to the glucocorticoid receptor , which is present in almost every vertebrate animal cell...

dosing is also expressed in terms of BSA for calculating maintenance doses or to compare high dose use with maintenance requirement.

Calculation

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

The Dubois & Dubois formula::

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