Body surface area

A moment s insight is sometimes worth a life s experience. 

Body surface area of animals is difficult to measure. It is much easier to weigh them. Thus, a relationship between body mass and surface area would be useful. 

We know that body mass must be proportional to body volume, and that volume has dimensions of length cubed (L ). Surface area has dimensions of length squared (p). Thus, we would expect surface area to be related to body mass to the two-thirds power  

Body surface area of humans is given by the DuBois formula (Johnson, 1999)  

FIGURE 7.4.3 Log-log plot of bird wing area against body mass for birds. (From Rayner, J.M.V., Curr. Ornithol. 5, 1, 1987. With permission.) 

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This energy, normalized per unit of body surface area (M/Ap) where... 

Body surface area The total surface area of the human body, determined from the Du Bois Index. 

The percentage of the body surface area covered by clothing. 

Du Bois area The total body surface area of a person. 

When using animal inhalation e.xpcrimcnts to estimate lifetime human risks for partially soluble vapors or gases, the air concentration (ppm) is generally considered to be the equivalent dose between species based on cqui alcnt c.xposure times (measured as fractions of a lifetime). For inhalation of particulates or completely absorbed gases, the amount absorbed per unit of body surface area is considered to be the equivalent dose between species. 

Table 23.2 Heat emission from the human body (aduit maie, body surface area 2 m ) (From CiBSE Guidebook A)...

If the drug dose is based on body surface area (m2) the same meHiod of calculation may be used. 

Nomogram for Estimating Body Surface Area of Infants and Young Children... 

Appendix E contains two body surface area nomograms—one for infants and young children and one for older children and adults. 

Elevated trichloroethylene levels in expired air were measured in subjects who immersed one hand in an unspecified concentration of trichloroethylene for 30 minutes (Sato and Nakajima 1978). Guinea pigs, exposed to dilute concentrations of aqueous trichloroethylene (-0.020 to 0.110 ppm) over a majority of their body surface area for 70 minutes, excreted 59% of the administered dose in the urine and feces 95% of the metabolized dose was excreted in 8.6 days (Bogen et al. 1992). No other studies were located for humans or animals regarding excretion after dermal exposure to trichloroethylene. 

NOEL (mg kg Q x body mass (kg) x 10 qgmg body surface area(cm2) x safety factor... 

Bums (thermal injury) in >30% of body surface area... 

Peritoneal dialysis (PD) utilizes similar principles as hemodialysis in that blood is exposed to a semipermeable membrane against which a physiologic solution is placed. In the case of PD, however, the semipermeable membrane is the peritoneal membrane, and a sterile dialysate is instilled into the peritoneal cavity. The peritoneal membrane is composed of a continuous single layer of mesothelial cells that covers the abdominal and pelvic walls on one side of the peritoneal cavity, and the visceral organs, including the GI tract, liver, spleen, and diaphragm on the other side. The mesothelial cells are covered by microvilli that increase the surface area of the peritoneal membrane to approximate body surface area (1 to 2 m2). 

The patient s psoriatic condition remains well controlled for about 10 years, then flare-ups become a frequent occurrence. The patient did not respond well to UVB therapy used alone. He is currently presenting with fairly extensive plaque psoriasis, affecting about two-thirds of his body surface area. 

The measured height and weight, along with the body surface area, if applicable, should be readily available, along with... 

Normalized for a 70-kg patient or body surface area of 1.73m2 all costs are estimated and may vary. G6PD, glucose-6-phosphate dehydrogenase, AWP, average wholesale price. 

BSA Body surface area CVP Central venous pressure... 

Cardiac index Cardiac output (see below) normalized for body surface area (cardiac index = cardiac output/body surface area). 

Glomerular filtration rate (GFR) The volume of plasma that is filtered by the glomerulus per unit time, usually expressed as mL/minute or mL/minute/1.73 m2, which adjusts the value for body surface area. GFR is the primary index used to describe overall renal function. 

Age does not significantly affect plasma concentrations or disposition of ibuprofen however, investigators have determined that the onset of antipyresis and maximum antipyretic effect is greater in children less than one year old as compared to children older than 6 years [43]. The authors hypothesized that this accelerated response was related to the greater relative body surface area of the young child. It should be noted that cystic fibrosis patients do have a higher clearance of ibuprofen [43a]. 

A casualty with skin lesions covering between 5 and 50% of the body surface area (BSA), or a casualty with mild to moderate pulmonary effects after 6 hours postexposure, or a casualty with eye injuries. 

Tazarotene (Tazorac) is a synthetic retinoid that is hydrolyzed to its active metabolite, tazarotenic acid, which modulates keratinocyte proliferation and differentiation. It is available as a 0.05% or 0.1% gel and cream and is applied once daily (usually in the evening) for mild to moderate plaque psoriasis. Adverse effects are dose- and frequency related and include mild to moderate pruritus, burning, stinging, and erythema. Application of the gel to eczematous skin or to more than 20% of body surface area is not recommended because this may lead to extensive systemic absorption. Tazarotene is often used with topical corticosteroids to decrease local adverse effects and increase efficacy. 

The psoriasis area and severity index is a uniform method to determine the extent of body surface area affected, along with the degree of erythema, induration, and scaling. Severity scores are rated as <12 (mild), 12 to 18 (moderate), and >18 (severe). 

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