Calculating the degree of a burn involves two key aspects: determining the depth and estimating the extent of the burn. First-degree burns are not included in the total body surface area (TBSA) calculation.
1. Determining Burn Depth
Burn depth is classified into three main degrees:
- First-degree burns: These affect only the epidermis (outer skin layer). They cause redness, pain, and mild swelling. Examples include mild sunburns.
- Second-degree burns: These involve the epidermis and part of the dermis (the layer beneath the epidermis). They are characterized by blisters, intense pain, swelling, and redness.
- Third-degree burns: These extend through the entire epidermis and dermis, potentially reaching underlying tissues like fat, muscle, or bone. The skin may appear white, charred, or leathery; pain may be absent due to nerve damage.
Burn depth is officially assessed 24 hours after the injury, as blisters and other injury manifestations may evolve. (Determining Burn Depth - MN Dept. of Health)
2. Estimating Burn Extent (Total Body Surface Area - TBSA)
The extent of the burn is expressed as a percentage of the patient's total body surface area (TBSA). The most common method for estimating TBSA is the Rule of Nines:
- Head: 9%
- Each arm: 9%
- Anterior chest and abdomen: 18%
- Posterior chest and back: 18%
- Each leg: 18%
- Perineum: 1%
([Several methods are available to estimate the percentage of total body surface area burned. Rule of Nines...](reference text)) (Rule of 9s for Adults: 9% for each arm, 18% for each leg, 9% for head,18% for front torso, 18% for back torso.) Note that the Rule of Nines is an estimation, and more precise methods may be used in clinical settings.
Example: A patient with second-degree burns covering their entire left arm and the anterior chest would have a TBSA of 27% (9% + 18%).
This TBSA estimation is crucial for fluid resuscitation calculations, such as the Parkland formula: Total fluid (ml) = 4 mL × weight (kg) × %TBSA. (The total amount of fluid to be given during the initial 24 hours = 4 ml of LR × patient's weight (kg) × % TBSA.)
Conclusion
Accurate assessment of both burn depth and extent is vital for appropriate treatment and prognosis. The Rule of Nines provides a quick estimation of TBSA, crucial for fluid management. Remember that first-degree burns are excluded from the TBSA calculation.
