Wounds

Disease/Disorder

Anatomy or system affected: All

Specialties and related fields: Critical care, emergency medicine, family medicine, internal medicine

Definition: Breakdown in the protective function of the skin; resulting in disruptions or breaks in the continuity of any body tissue.

Wounds might arise because of violence, accident, or intentional procedure, such as surgery. They may be classified according to the instrument responsible, such as a knife, bullet, or shrapnel, or according to the way in which they occurred, such as a burn or a crushing wound.

Surgeons describe wounds according to their general appearance. A wound may be described as incised, when a sharp cutting instrument is involved; lacerated, when the tissue is damaged, cut, or torn; abrasion, when a superficial layer of skin is removed; contused, when a forceful blow to the tissue leaves the skin intact, causing bluish/blackish discoloration; avulsed, when part of the tissue is torn apart; punctured, when the outer opening is rather small; penetrating; and nonpenetrating, when the external tissue remains intact. Fractures are also classified in several terms, such as incomplete, complete, closed, or open. The depth of the tissue injury classifies burns as first, second, or third degree.

Generally, wounds may be classified as open or closed. Closed wounds involve no external hemorrhage, and their degree of seriousness is related to the force of the blow and its direction, the age of the victim, and other physiological and anatomical factors. Normally, internal hemorrhage stops abruptly or by applying direct pressure, with the blood and fluid absorbed within a few days. More bleeding occurs when larger internal vessels are damaged, with subsequent collection of the blood in tissues, forming a hematoma that may take several weeks to be absorbed. The impact on a body part may result in damage to a part that is not directly involved at the time of impact. Thus, a fall on an outstretched hand may injure not only the flesh and bones of the hand itself but also the scaphoid part of the wrist, or even the elbow or shoulder. During a car accident, a stationary body part may be heavily affected by the transmission of impact from a relatively mobile part; when occurring in the neck, this type of injury is commonly known as whiplash. First aid procedures for fractures, sprains, and strains include ice packs, crutches, elevation, and splinting.

Infections resulting from wounds. Open wounds take place when the skin and/or mucous membranes are broken, thus allowing the invasion of hazardous foreign material, such as bacteria or dirt, into the tissues. This invasion may lead to infection, which is particularly serious when the disruption of the skin is considerable. Generally, injuries from sharp instruments (such as a needle, knife, or bullet) cause little tissue damage, except to the part that they penetrate. The great danger lies in the injury of a vital organ and from the foreign objects that are on the surface of the instrument. Injuries from irregular objects (such as bomb fragments or a jagged knife) create much more damage, which leads to longer recuperation periods. Skin is elastic and well supplied with blood, which means that superficial cuts heal easily. The subcutaneous fatty tissues and muscles are not as rich in blood supply, and their damage is more serious and long-lasting, especially because it is easier for infection to occur. Fragmentation of bone in an open wound is particularly troublesome, since the fragments cannot survive without blood and will act as foreign substances, thus creating a serious infection. Injuries to joints, nerves, or major capillaries (such as arteries) will complicate the state of the open wound.

The contamination of the wound may start immediately after the causative incident. Nonbacterial contamination is more serious when organic substances are involved. In bacterial contamination, the most serious results are seen with virulent bacteria that are nourished by dead tissue and organic foreign material, sometimes leading to gas gangrene. Such infection generally spreads unchecked and can be stopped only by surgical removal or amputation, in order to avoid death. Other infections are caused by streptococcal and staphylococcal bacteria and are characterized by the local production of swelling, redness, and pus. Finally, tetanus is another type of wound infection. It starts with serious muscle spasms a few days after the injury and, left untreated, often leads to death.

The healing process. When an open wound occurs, the tissues are cut and the edges of the wound separate, pulled apart by the elasticity of the skin. Blood flowing from the wound fills the resulting cavity, fibrin is produced, and the blood clots, creating a scab. During the first twenty-four hours after the injury, the scab shrinks, drawing the edges of the skin together. Special cells called histiocytes and macrophages digest the debris in the wound, such as blood seepage, dead cells, and other foreign bodies, two to three days after the injury. Connective tissue cells called fibroblasts grow inward from the margins of the wound to close the cavity three to five days after injury. The fibroblasts produce a protein called collagen that provides strength to the new skin.

The red-colored capillaries slowly disappear and are replaced by white collagen. Thus, upon removal of the scab, a layer of reddish granulation tissue appears, which covers the subcutaneous tissue. A thin, gray membrane extends outward from the skin edges and covers the whole surface. Contraction brings the epithelial sheets from the two sides together, and eventually the skin around the wound is reproduced. Wounds that cross normal skin creases become depressed below the level of the surrounding skin. The resulting scars, which are very low in capillaries, do not become tanned with sunlight exposure, and they produce neither hair nor sweat, which is indicative of skin that is less than fully functional. They are much whiter than the surrounding skin.

Treatment. Medical treatment of wounds requires first the control of bleeding by direct pressure or bandaging. In the case of small cuts, local irrigation and the use of disinfection include the external use of oxidizing agents (such as hydrogen peroxide) and of nonpolar ointments (such as petroleum jelly) to combat invading polar bacteria. A large area of injury or dead tissue is managed surgically, either by debridement or through amputation. Sutured wounds heal faster because stitches bring the skin edges together. Foreign surgical material introduced in a wound may be absorbed by the tissues, which is exactly what happens when catgut is used to close the wounded tissue. Body factors are also crucial in the overall healing; these include age, the concurrent presence of diseases such as uncontrolled hypertension and diabetes, and nutrition that includes adequate quantities of protein and anti-oxidants, such as vitamin C. Hospitals take elaborate precautions to prevent infections through sterilization, hand sanitation, good air filtration, the use of ultraviolet light to kill bacteria in the operating room, and the administration of antibiotics. The skin in the area of any surgery is treated with antiseptics and is carefully protected with sterilized cloth.

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