A 32-year-old man is brought to the emergency department 6 hours after a flame burn injury affecting 35% of his body surface area (BSA). He has erythematous and blistered skin with severe pain. On examination, the burned areas blanch on pressure but sensation is intact. Which investigation is most appropriate to assess the depth of thermal injury and guide management?

Explanation

## Assessment of Burn Depth — Investigation of Choice ### Clinical Context The patient presents with a second-degree (partial-thickness) burn based on clinical features: erythema, blistering, pain sensation, and blanching on pressure. Determining burn depth is critical for prognosis and deciding between conservative management and surgical intervention. ### Why Laser Doppler Flowmetry (LDF) is the Gold Standard **Key Point:** Laser Doppler flowmetry is the most specific non-invasive investigation for assessing microvascular perfusion in burned skin and predicting healing potential. **High-Yield:** LDF measures blood flow in the dermal microvasculature: - **Viable skin** (superficial burns): High perfusion signal → spontaneous healing expected - **Non-viable skin** (deep burns): Low or absent perfusion signal → surgical excision and grafting needed - **Intermediate zone** (indeterminate depth): Moderate signal → requires serial assessment ### Mechanism Laser Doppler uses a low-power laser beam to measure red blood cell movement. The Doppler shift in reflected light is proportional to microvascular blood flow. This allows differentiation of: - Superficial partial-thickness burns (healing in 2–3 weeks) - Deep partial-thickness burns (healing in 3–4 weeks or requiring grafting) - Full-thickness burns (no healing potential) ### Advantages Over Other Modalities | Investigation | Principle | Limitation | |---|---|---| | **Laser Doppler Flowmetry** | Microvascular perfusion | Equipment-dependent; requires expertise | | Thermography | Infrared heat emission | Non-specific; cannot differentiate depth reliably | | Ultrasound | Acoustic impedance | Poor sensitivity for early burn depth; mainly used for scar assessment | | Histopathology | Tissue architecture | Invasive; destroys tissue; not practical for acute management | **Clinical Pearl:** LDF can predict which deep partial-thickness burns will heal spontaneously vs. those requiring grafting, reducing unnecessary surgery and improving functional outcomes. **Tip:** In NEET PG exams, when asked about "investigation of choice" for burn depth assessment, think **perfusion** — only LDF directly measures blood flow in the burned dermis. [cite:Park 26e Ch 9]