Which clinical feature best distinguishes a deep partial-thickness (2nd degree deep) burn from a full-thickness (3rd degree) burn?

Explanation

## Distinguishing Deep Partial-Thickness from Full-Thickness Burns ### Depth and Structural Involvement **Key Point:** Deep partial-thickness (deep 2nd degree) burns destroy the epidermis and most of the dermis but spare some dermal appendages (hair follicles, sweat glands, sebaceous glands). Full-thickness (3rd degree) burns destroy the entire epidermis and dermis, obliterating all appendages. ### Clinical Feature Comparison | Feature | Deep Partial-Thickness (Deep 2°) | Full-Thickness (3°) | |---------|-----------------------------------|---------------------| | **Pain sensation** | Severe pain (nerve endings intact in deep dermis) | Painless (all nerve endings destroyed) | | **Appearance** | Mottled red/white, blistered, wet surface | Leathery, charred, dry, waxy, or translucent | | **Blanching** | May blanch slowly or not at all | No blanching | | **Hair follicles** | Some intact (pull test positive) | All destroyed (pull test negative) | | **Healing** | Slow epithelialization from appendages; high scarring risk | No spontaneous healing; requires grafting | | **Eschar** | May form but softer | Hard, thick, adherent eschar | ### Why Severe Pain is the Best Discriminator **High-Yield:** Pain is the most reliable bedside clinical discriminator: - **Deep 2° burns** retain viable sensory nerve endings in the deep dermis → **severe pain on touch and air exposure** - **3° burns** have complete nerve destruction → **painless** (patient may report only pressure sensation from deeper tissues) **Clinical Pearl:** A burn that is exquisitely painful to light touch is almost certainly deep partial-thickness, not full-thickness. This distinction guides fluid resuscitation, grafting urgency, and prognosis. ### Why Other Features Are Less Specific - **Leathery, charred appearance:** This is characteristic of 3° burns, but some deep 2° burns can appear darkly mottled or even charred in appearance, making visual assessment alone unreliable. - **Hair follicle presence:** While true, this requires close inspection and is less immediately apparent at the bedside than pain response. - **Eschar formation:** Both deep 2° and 3° burns can form eschar; timing and character overlap, making this less discriminating. [cite:ATLS 10th Edition Ch 7]