Total Body Surface Area (TBSA) is a measurement defining the percentage of a person’s skin affected by a burn injury. This calculation is fundamental in burn care, as it guides two immediate and crucial treatment decisions: fluid resuscitation and triage. Determining the precise amount of intravenous fluids needed to prevent shock, known as the Parkland formula, depends entirely on this percentage. The TBSA percentage also helps medical personnel decide if the patient needs transfer to a specialized burn center for definitive care.
Determining Which Burn Depths Are Counted
TBSA calculation is applied only to burns that penetrate beyond the top layer of skin. Burns are classified by depth, typically categorized as first, second, third, or fourth degree. Superficial burns (first-degree) involve only the epidermis and are excluded from TBSA calculation. They do not cause the massive fluid shifts that necessitate aggressive fluid resuscitation.
Only partial-thickness and full-thickness burns are included in the final TBSA percentage. Partial-thickness burns (second-degree) extend into the dermis, usually presenting with blisters and a painful, moist wound bed. Full-thickness burns (third and fourth-degree) destroy both the epidermis and the dermis, sometimes extending into underlying fat, muscle, or bone. Including only these deeper burns ensures the TBSA score accurately reflects the patient’s need for immediate medical intervention.
The Rule of Nines
The Rule of Nines is a rapid and simple method used almost exclusively for estimating TBSA in adults. This system divides the adult body into anatomical regions, each representing approximately 9% or a multiple of 9% of the total body surface area. Its speed makes it useful for initial assessment in pre-hospital or emergency department settings. While efficient, the Rule of Nines can be less precise for very obese individuals or non-adult patients.
The adult breakdown assigns percentages as follows:
- The entire head and neck region is 9%.
- Each complete arm, including the hand, is 9%.
- The front of the torso (anterior trunk) is 18%.
- The back of the torso (posterior trunk) is 18%.
- Each complete leg, including the foot, is 18%.
- The remaining 1% is allocated to the genital or perineum region.
By summing the percentages of these burned regions, medical professionals quickly arrive at a total percentage to guide immediate care.
The Lund-Browder Chart
The Rule of Nines is inaccurate for children due to significant differences in body proportions compared to adults. Infants and young children have a proportionally larger head and smaller lower extremities. The Lund-Browder Chart was developed to provide a more accurate, age-adjusted method for calculating TBSA in the pediatric population. This chart is considered the gold standard in burn centers because it accounts for developmental changes in body surface distribution.
The chart uses a diagram of the human body divided into specific regions, each assigned a percentage that changes with the patient’s age. For example, an infant’s head can represent up to 19% of their TBSA, compared to 9% for an adult. Conversely, a young child’s lower extremities account for a smaller percentage, which increases as the child grows.
Medical staff outline the burned areas directly onto the diagram and sum the age-specific percentages to determine the final TBSA. This detailed, age-specific adjustment helps prevent systematic overestimation of burns in children, a common risk when using the adult Rule of Nines. Accurate TBSA estimation is vital for children because they require fluid resuscitation at a lower burn percentage threshold than adults.
The Palmar Method
The Palmar Method, or Hand Method, is a simple estimation technique used for burns that are small, irregular, or scattered across the body. It estimates patches of burn that do not fit neatly into the large anatomical segments used by the Rule of Nines or the Lund-Browder Chart. The underlying principle is that the patient’s entire palm, including all five fingers held together, represents approximately 1% of their total body surface area.
This measurement must use the patient’s own hand size, not the hand of the medical professional performing the assessment. Clinicians mentally or visually superimpose the patient’s palm over the burned area to count how many “palms” the burn covers. This technique is valuable in pre-hospital or resource-limited settings where detailed charts may not be readily available. Its simplicity makes it a universally available tool for assessing minor or patchy burns.