Assessment of burn depth

Burn depth depends, in thermal injury, upon:
• the temperature of the burning agent;
• the mode of transmission of heat;
• the duration of the contact.
Much of this information can be obtained from taking a good history of the injury. Clinical examination of the burn wound may also show characteristic features.
Skin anatomy
The epidermis is the most superficial layer of the skin and provides the waterproofing layer. It is constantly replaced from the basal layer. The dermis is the thicker underlying area that supplies the strength and integrity of the skin. It has a rich blood supply from the subdermal capillary network. It contains the adnexal structures — hair follicles, sebaceous glands and sweat glands. These adnexal structures contain epithelial cells that can proliferate and heal a partial-thickness wound by epithelialisatton.
Superficial burns
These have the ability to heal themselves by epithelialisation alone. Epidermal burns look red, are painful, blisters are not present, and they heal rapidly without sequelae. Superficial dermal burns are blistered and painful; they should heal by epithelialisation within 14 days without scarring, but some­times leave long-term pigmentation changes.
Deep burns
These have lost all adnexal structures and if left can only heal by second intention with scarring. Deep dermal burns may be blistered and have a blotchy red appearance with no capillary return on pressure and absent sensation to pinprick. Full-thickness burns have a white or charred appearance; again sensation is absent. This charred layer consists of denatured, contracted dermis and is called an eschar.
In practice most burns contain areas of differing burn depth. Decision making is easy where burns are obviously superficial or obviously deep, with difficulties arising in the distinction between the deeper superficial burns and deep dermal burns.