U01.11.070 Estimation of body surface area

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Learning Objectives

Master the Rule of 9’s for rapid estimation of Total Body Surface Area (TBSA) in burn patients. Identify the clinical signs and diagnostic findings of Inhalation Injury, a critical complication of thermal and chemical trauma.

1. Estimation of TBSA: The Rule of 9’s

The Rule of 9’s is a standardized tool used to assess the extent of burn injuries, which is essential for determining fluid resuscitation needs (e.g., via the Parkland Formula).

Body Region Surface Area Percentage Notes for Calculation
Head & Neck 9% 4.5% anterior / 4.5% posterior.
Each Upper Limb 9% (Total 18%) 4. 4,5% anteriore / 4,5% posteriore per braccio.
Trunk (Thorax & Abdomen) 36% 18% anterior / 18% posterior.
Each Lower Limb 18% (Total 36%) 9% anterior / 9% posterior per leg.
Perineum / Genitalia 1% Small but critical for fluid and infection risk.

2. Inhalation Injury

Inhalation injury occurs when noxious stimuli (smoke, heat, or irritants like NH3) cause damage to the respiratory tract. This is a leading cause of mortality in fire victims.

Feature Clinical / Diagnostic Findings
Physical Exam Singed nasal hairs, facial burns, soot in the oropharynx, and carbonaceous sputum.
Bronchoscopy Severe edema, airway congestion, and soot deposition.
Complications Chemical tracheobronchitis, pneumonia, and ARDS (Acute Respiratory Distress Syndrome).

3. High-Yield Clinical Correlation

Prompt recognition of inhalation injury is vital because airway edema can progress rapidly, necessitating early prophylactic intubation.

Pathogen/Irritant Effect on the Respiratory Tract
Particulates (< 1 μm) Reach deep alveoli; trigger inflammatory response.
Smoke/Heat Direct thermal injury to the upper airway; massive swelling.

Activity:

High-Yield Mnemonics & Tips:

  • Rule of 9’s: If the question asks about a single leg (front and back), it is 18%. If it’s just the front of one leg, it is 9%.
  • Airway Warning: Always prioritize the airway in burn patients with facial burns or soot in the mouth.
  • ARDS: Watch for worsening oxygenation and diffuse “white-out” on CXR within 24–48 hours of inhalation.

Activity: