Wound care and healing

Wound care

A wound can be intentional (e.g., from a surgical incision) or accidental, and it may be open or closed. An open wound has an outward opening; the skin is broken, exposing the underlying tissues. A closed or nonpenetrating wound does not have an outward opening, but the underlying tissues are damaged, as in a hematoma, contusion, or bruise. Closed wounds usually are the result of some type of blunt trauma to the body. An aseptic (i.e., clean) wound is not infected with pathogens. Septic wounds are infected with pathogens.

Open wounds may be classified according to the appearance of their openings. An incised wound has a clean edge and is made with a cutting instrument. An incised wound may be the result of surgery, an accident, or a knife wound. A lacerated wound has torn or mangled tissues and is made by a dull or blunt instrument. A penetrating or puncture wound is caused by a sharp, slender object, such as a needle or an ice pick, passing through the skin into the underlying tissues. A perforated wound is a penetrating wound that passes through to a body organ or cavity, such as a gunshot wound.

Wound healing

All wounds go through a healing or repair process that has four phases. Hemostasis is the first phase. Blood vessels contract to control hemorrhage, and blood platelets form a network that acts as a glue to plug the wound. After a cascade of chemical reactions, fibrin is released into the wound and clotting begins. Fibrin continues to collect red blood cells (RBCs), and the clot dries into a scab.

The second, or inflammatory, phase focuses on destroying bacteria and removing debris. Special white blood cells (WBCs), called macrophages, arrive to clear away bacteria and dead tissue. This phase usually lasts about 1 to 4 days. During this phase, edema, erythema (redness), heat, and pain can occur.

The third phase, proliferation, encompasses wound healing and new growth; this lasts 5 to 20 days. During this phase, the tissues repair themselves. New cells form, and the wound continues to contract and seal. If the wound is a clean surgical incision, complete contraction usually occurs and a cicatrix forms.

The final phase, the remodeling phase, extends from day 21 onward. Clean, shallow wounds may contract in the first two stages; large or mangled wounds require the time and cellular activity of this final phase to build a bridge of new tissue to close the gap of the wound. The cells produce a fibrous protein substance called collagen (i.e., connective tissue) that gives the wounded tissues strength and forms scar tissue. Scar tissue is not true skin; it usually is very strong, but it lacks the elasticity of normal skin tissue. There is no blood supply or nerves in scar tissue.

Several factors influence the healing process. People who are young, in good general health, and have adequate nutrition heal more rapidly. Adequate protection and rest of the injured area also enhance the healing process. Destruction or reinjury during the second phase can delay healing and increase scarring. Wounds are susceptible to infection because the normal skin barrier is broken. If debris is present in a wound as the result of the breakdown of various cellular components, this dead (i.e., necrotic) tissue acts as a culture medium for bacterial growth. Suppuration (i.e., pus) contains necrotic tissue, bacteria, dead WBCs, and other products of tissue breakdown. Necrotic tissue must be removed; debris removal is called debridement, which may occur naturally or may be performed surgically.

Sometimes the provider may prefer no dressing or bandage on small wounds. This is called open wound healing. There are some advantages to open wound healing:

• Air can circulate freely around the wound.
• The wound is not irritated or rubbed by a dressing.
• The wound stays dry, which inhibits bacterial growth, reducing the chance of infection.
• Sutures stay dry and hold together better.
• Any preexisting infection remains localized and is not spread by the dressing or bandage.