Body Surface Area
Overview
Body Surface Area (BSA) is a measurement used in many medical tasks. It is a measure of the total surface area of the human body. The calculation of body surface area is important in medicine, particularly where the administration of drugs is required. The BSA is frequently used in determining the dosage of medications with a narrow therapeutic index, such as chemotherapy. The BSA is also used in physiology and nutrition, to better understand the body's metabolic processes and nutritional needs.
Calculation Methods
There are several methods to calculate the body surface area. The most commonly used methods include the Du Bois formula, Mosteller formula, Haycock formula, Gehan and George formula, and Boyd formula. Each of these methods uses different parameters and calculations to estimate the body surface area.
Du Bois Formula
The Du Bois formula is one of the earliest and most commonly used methods to calculate the body surface area. It was developed by Dr. Du Bois and Dr. Du Bois in 1916. The formula is as follows:
BSA = 0.007184 * Height(cm)^0.725 * Weight(kg)^0.425
This formula is often used in clinical pharmacology and provides a BSA value in square meters (m^2).
Mosteller Formula
The Mosteller formula is another commonly used method to calculate the body surface area. It was developed by Dr. Mosteller in 1987. The formula is as follows:
BSA = sqrt([Height(cm) * Weight(kg)]/3600)
Like the Du Bois formula, the Mosteller formula also provides a BSA value in square meters (m^2).
Haycock Formula
The Haycock formula is a method to calculate the body surface area that was developed by Dr. Haycock and colleagues in 1978. The formula is as follows:
BSA = 0.024265 * Height(cm)^0.3964 * Weight(kg)^0.5378
This formula is often used in pediatric medicine due to its accuracy in estimating the BSA of children.
Gehan and George Formula
The Gehan and George formula is a method to calculate the body surface area that was developed by Dr. Gehan and Dr. George in 1970. The formula is as follows:
BSA = 0.0235 * Height(cm)^0.42246 * Weight(kg)^0.51456
This formula is often used in oncology and other fields where precise BSA calculations are necessary.
Boyd Formula
The Boyd formula is a method to calculate the body surface area that was developed by Dr. Boyd in 1935. The formula is as follows:
BSA = 0.03330 * (Weight(g)^0.6157 - 1800) * Height(cm)^0.3
This formula is often used in neonatology and pediatrics due to its accuracy in estimating the BSA of newborns and infants.
Applications in Medicine
The body surface area has a wide range of applications in medicine. It is used in the calculation of drug dosages, particularly for drugs with a narrow therapeutic index. The BSA is also used in the assessment of cardiac function, as it allows for a more accurate estimation of cardiac output. In addition, the BSA is used in the calculation of renal function, as it is used to normalize the glomerular filtration rate.
Drug Dosage Calculation
The calculation of drug dosages is one of the most common applications of the body surface area. Many drugs, particularly those with a narrow therapeutic index, are dosed based on the patient's BSA. This is because the BSA provides a better estimate of the patient's metabolic rate than body weight alone. Therefore, dosing based on BSA allows for a more accurate and individualized drug dosage.
Cardiac Function Assessment
The body surface area is also used in the assessment of cardiac function. The BSA is used to normalize the cardiac output, which is the volume of blood pumped by the heart per minute. By normalizing the cardiac output to the BSA, physicians can compare the cardiac function of individuals of different sizes.
Renal Function Calculation
The body surface area is used in the calculation of renal function. The glomerular filtration rate (GFR), which is a measure of the kidneys' ability to filter waste from the blood, is often normalized to the BSA. This allows for a more accurate estimation of renal function, particularly in individuals of different sizes.