Final answer:
TBSA in children under 9 years old is calculated using methods like the Lund and Browder chart, which adjusts the percentage of TBSA for each body region according to growth and development stages.
Step-by-step explanation:
Calculating the Total Body Surface Area (TBSA) in patients, especially in children under 9 years old, is crucial for medical treatments like dosing of medications and planning fluid resuscitation in burn patients. The most widely used method for estimating TBSA in children is the Lund and Browder chart, which takes into account the changes in body surface area that occur with growth and development. This chart has different columns for various age groups, such as children ages 0 to 2.5, children ages 2.5 to 6, children ages 6-13, and children ages 13-20. Each body region's percentage of TBSA is adjusted for the child's age, reflecting the proportional differences in surface area among body parts as a child grows.