A severe thermal injury is one of the most devastating physical and psychological injuries a person can suffer. The overall incidence of burn injuries has been declining over the past decade, with 500,000 burn injuries per year and only 3250 deaths. This trend is due in large part to public health initiatives to improve fire safety as well as advancements in critical care. Most burn injuries are due to flame burns, but scald burns follow closely as the second most common type of injury. Most burns are less than 10% total body surface area (TBSA), but for patients who suffer large TBSA burns, the hospital length of stay can last months, with much of that time in the intensive care unit (ICU). These patients frequently require lifelong care due to the physical and psychological effects of the injury and the suffering endured from repeated surgeries and wound care.
ANATOMY & PHYSIOLOGY OF THE SKIN
The skin is the largest organ of the body, ranging in area from 0.25 m2 in the newborn to 1.8 m2 in the adult. It consists of three layers: the epidermis, the dermis (corium), and the hypodermis. The outermost cells of the epidermis are dead cornified cells that act as a tough protective barrier against the environment, including bacterial invasion and chemical exposure. These cells vary in thickness in different parts of the body and are thickest on the palms of the hand and soles of the feet. The inner cells of the epidermis are metabolically active, producing compounds such as growth factor, which help the ongoing replication process every 2 weeks, and contain melanocytes, which are specialized cells of the epidermis that produce melanin. Most humans have a similar number of melanocytes but vary in the amount melanin produced.
The second layer, the dermis (0.06-0.12 mm), is composed chiefly of fibrous connective tissue. The dermis contains the blood vessels and nerves to the skin and the epithelial appendages of specialized function such as sweat glands. The dermis is a barrier that prevents loss of body fluids by evaporation and loss of excess body heat. Sweat glands help maintain body temperature by controlling the amount of water that evaporates. Some other important functions can be found within the dermis, which is interlaced with sensory nerve endings that mediate the sensations of touch, pressure, pain, heat, and cold. This is a protective mechanism that allows an individual to adapt to changes in the physical environment. The skin produces vitamin D, which is synthesized by the action of sunlight on certain intradermal cholesterol compounds.
The hypodermis is made mostly of fatty tissues that attach the dermis to the underlying tissue of muscle and bones. It provides a pathway for nerves and blood vessels and provides insulation to assist with thermoregulation.