To calculate the Total Body Surface Area (TBSA) percentage burned, you divide the area of the body that is burned by the total surface area of the body. This percentage is crucial for determining the severity of the burn and guiding treatment. Several methods are used to estimate TBSA, with the "Rule of Nines" being the most common for adults and the Lund-Browder chart being more accurate, especially for children.
Here's a breakdown of common methods:
1. Rule of Nines (Adults)
The Rule of Nines assigns percentage values to different body regions, approximating the surface area of each.
- Head: 9%
- Each Arm: 9%
- Each Leg: 18%
- Anterior Trunk: 18%
- Posterior Trunk: 18%
- Genitals (Perineum): 1%
Calculation Example: If an adult has burns covering their entire anterior trunk and their entire right leg, the TBSA burned is approximately 18% (anterior trunk) + 18% (right leg) = 36%.
Advantages: Quick and easy to use.
Disadvantages: Less accurate for children or individuals with atypical body proportions. It also overestimates TBSA in obese individuals.
2. Lund-Browder Chart
The Lund-Browder chart is a more precise method, especially for children, as it adjusts the percentages based on age and body proportion. It accounts for the fact that the relative surface area of the head is larger in infants and young children compared to adults. Burn care centers typically use this method.
How it works: The chart provides varying percentages for different body parts based on age. The burn surface area is sketched onto the chart, and the corresponding percentages are totaled.
Advantages: More accurate than the Rule of Nines, particularly for pediatric patients.
Disadvantages: Requires specialized charts and more time to complete accurately.
3. Palmar Method (Rule of Palms)
The Palmar method approximates that the patient's palm (including the fingers) is equal to 1% of their total body surface area. This is particularly useful for estimating smaller, scattered burns.
How it works: Estimate the number of palms needed to cover the burned area and multiply by 1%.
Calculation Example: If the burned area is roughly the size of five of the patient's palms, the TBSA burned is approximately 5%.
Advantages: Useful for estimating small or irregular burn areas.
Disadvantages: Less accurate for larger burn areas.
Factors Affecting TBSA Calculation Accuracy:
- Obesity: Can lead to overestimation of TBSA using the Rule of Nines.
- Age: The Lund-Browder chart is more accurate for children.
- Burn Depth: While TBSA focuses on surface area, consider that deeper burns contribute to greater overall morbidity and mortality.
- Experience: Accurate assessment requires experience and training in burn evaluation.
Estimating TBSA is a critical first step in burn management, informing fluid resuscitation, medication dosages, and overall treatment plans. While the methods described provide reasonable approximations, the Lund-Browder chart generally provides the most accurate assessment, especially for pediatric patients.
