A severe thermal injury is one of the most devastating physical
and psychological injuries a person can suffer. Over 2 million injuries
due to burns require medical attention each year in the United States,
with 14,000 deaths resulting. Fires in the home are responsible
for only 5% of burn injuries but for 50% of burn
deaths—most due to smoke inhalation. About 75,000 patients
require hospitalization every year, and 25,000 of those remain hospitalized
for over 2 months—evidence of the severity of illness associated
with this injury.
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 two layers: the epidermis and the dermis (corium).
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. The inner cells of the epidermis
are metabolically active, producing compounds like growth factor, which
help the ongoing replication process every 2 weeks. The second,
thicker 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
like sweat glands. The nerve endings that mediate pain are found in the dermis.
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. The dermis is
also 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 depth of the burn (Figure 14–1)
significantly affects all subsequent clinical events. The depth may be difficult to determine and in some cases is not known until after spontaneous healing has occurred or when the eschar is surgically removed or separates, exposing the wound bed.
Layers of the skin showing depth of first-degree, second-degree, and third-degree burns.
Traditionally, burns have been classified as first-, second-, and
third-degree, but the current emphasis on burn healing has led to
classification as partial-thickness burns, which can heal spontaneously,
and full-thickness burns, which require skin grafting, although deep partial-thickness burns are usually excised and grafted as well.
A first-degree burn involves only the epidermis
and is characterized by erythema and minor microscopic changes;
tissue damage is minimal, protective functions of the skin are ...