Body surface area was developed as a metric to use in the modulation of various pharmacological therapies, as well as a standard tool by which to index various physiologic measurements such as glomerular filtration rate and cardiac output. There exist many variations in formulae to calculate an individual’s body surface area, but one of the most widely used techniques to calculate this value is the Du Bois and Du Bois formula. The formula is as follows[1]:
Body Surface Area= 0.007184 x (Height(m)^0.725) x (Weight(kg)^0.425)
A predominant area of concern in calculating body surface area is that many different equations are used in the calculation. As such, some of the equations may yield vastly different results from others. In the clinical context, this presents a significant challenge. For example, body surface area is used to calculate the dosing regimen for many medications to ensure the medication’s therapeutic window is maintained, and adverse effects avoided. Significant variances in body surface area calculations potentially result in over- or under-dosing of drugs and failure to obtain the targeted effects of the drug.[2]
The body surface area metric holds a significant place in both pharmacology and physiologic data measurement. Body surface area is most commonly used to guide the dosing of chemotherapeutic drugs. Early chemotherapy research found that the effects of these cancer treatments were much more consistent among individuals when dosed according to body surface area as opposed to bodyweight alone.[3]
Body surface area is also useful to assess the degree of severity in severe burn injury patients. It is crucial to accurately assess the percentage of total body surface area that a patient has sustained burns to stratify the severity best and guide the management of patients with burn injuries.[4] Physiologic information can be calculated in part using body surface area.
Another essential use of body surface area is in the calculation of a patient's cardiac index, a measure of the physiologic status of cardiac function. The formula for the cardiac index is (liters/min)/(body surface area).[5] Further, the use of clinical tools, such as nomograms, utilizes the patient's height and weight displayed graphically to calculate their body surface area as well.
Clinical teams managing patients in hospital units or clinics which administer and manage chemotherapy treatment regimens should possess a sound understanding of how to calculate body surface area. It should be a routinely observed metric for any patient under the care of a chemotherapy treatment plan. Furthermore, clinical providers, nursing staff, and allied healthcare workers who work in burn injury units should also develop an understanding of the calculation of body surface area, and it’s implications specifically in the management of burn injuries.
In summary, all staff caring for patients should have an understanding of how to calculate the body surface area. In patient populations in which it’s utility is particularly underscored, this skill is even more vital. Furthermore, physicians, medical students, and nurses need to develop an understanding of body surface area as it relates to chemotherapy, metering the severity of burn injuries, and in understanding physiologic parameters.
[1] | Burton RF, Estimating body surface area from mass and height: theory and the formula of Du Bois and Du Bois. Annals of human biology. 2008 Mar-Apr; [PubMed PMID: 18428011] |
[2] | Sigurdsson TS,Lindberg L, Six commonly used empirical body surface area formulas disagreed in young children undergoing corrective heart surgery. Acta paediatrica (Oslo, Norway : 1992). 2020 Feb 3; [PubMed PMID: 32010999] |
[3] | Kaestner SA,Sewell GJ, Chemotherapy dosing part I: scientific basis for current practice and use of body surface area. Clinical oncology (Royal College of Radiologists (Great Britain)). 2007 Feb; [PubMed PMID: 17305252] |
[4] | Retrouvey H,Chan J,Shahrokhi S, Comparison of two-dimensional methods versus three-dimensional scanning systems in the assessment of total body surface area estimation in burn patients. Burns : journal of the International Society for Burn Injuries. 2018 Feb; [PubMed PMID: 28797577] |
[5] | Patel N,Makaryus AN, Physiology, Cardiac Index 2020 Jan; [PubMed PMID: 30969727] |