IMPEDIMENTS TO WOUND HEALING

Unfortunately, not all wounds heal in a timely or predictable manner. There are multiple factors that negatively impact wound healing. Some of these are related to the patient’s overall health status, and others are environmental. One of the most serious impediments to wound healing is infection (discussed above). Other impediments to wound healing are discussed below.

Re-Injury

Re-injury can slow or stop wound healing. Pushes and pulls that would have no effect on healthy parts of the body can reopen a healing wound even when it is protected by a well-made dressing. Similarly, if there is significant skin tension surrounding the wound (e.g., over a bent knee), the healing wound will not be able to seal tightly (see below).

Ischemia/Hypoxia

Oxygen is required in all phases of wound healing, from inflammation to re-epithelialization, and any condition that results in decreased oxygen supply (hypoxia) to the wound bed will impede wound progress.

Ischemia of a wound can arise from too much physical tension across the wound; ineffective oxygenation of the blood (anemia, lung problems, smoking); or reduced circulation (atherosclerosis, heart failure, kidney failure, vasoconstriction, too much pressure on the wound). Differences in the available blood supplies account, in part, for the fact that facial wounds tend to heal better than foot wounds.

The importance of local circulation to wound healing is reflected in the healthcare maxim “wounds that don’t bleed don’t heal.” Circulation brings oxygen, which aids healing. A wound that continues to bleed, however, is not proceeding to the next step in healing. A crumbling (friable) wound bed is not healing and may indicate infection.

Local Skin Tension

Skin and its underlying tissues are normally under tension. Most skin in the body is being stretched, at least slightly, by the adjacent skin and the underlying structures, but the actual tension at any one location varies along the surface of the body. Movement changes skin tension: bending a joint stretches the overlying skin, while contracting a muscle tends to reduce tension in the overlying skin. Skin creases and skin wrinkles are indications of lines of least tension; on the face, the lines of facial expression are also lines of least tension. As a rule, the lines of least skin tension are perpendicular to the long axis of underlying muscles.

Skin tension is negligible along skin creases, moderate over relaxed joints and muscles, and high over bent joints (knees and elbows) and the skull. During a cutting, ripping, or puncturing injury, the tension from the adjacent intact skin pulls the free edges of the wound apart. In places where the wounded skin is under greater tension, the wound gapes more widely and heals more slowly, and the resulting scar is relatively large.

Obesity increases tension on the abdomen and difficulty due to movement of the panniculus (overhanging folds of subcutaneous fat, which may weigh several pounds), particularly when the panniculus moves to the sides and away from center line. Thus, obesity delays wound healing due to mechanical forces.

Patient Factors

DISEASES

Certain diseases are noted for causing poor wound healing. The most common of the problem diseases is diabetes mellitus. Scars formed from wounds in people with diabetes have less collagen, and the collagen that is laid down is more brittle than normal. Diabetes also damages blood vessels and makes the skin more prone to ischemia. The reduced circulation is especially notable in the feet, and foot wounds are notorious for not healing well in patients with diabetes (see also “Diabetic Foot Ulcers” later in this course).

To make matters worse, diabetes leads to peripheral neuropathy. Patients lose sensation in their fingers and toes, so diabetic injuries tend to go unnoticed in the extremities. Finally, people with diabetes have a weakened inflammatory response and are more susceptible than other people to developing tissue infections.

NUTRITION

Nutrition plays a vital role in all stages of wound healing. For instance, malnourished people begin to break down their proteins as a source of energy, and this slows healing. Specific vitamin deficiencies also lead to poor wound healing, such as vitamin K deficiency, which impairs blood clotting.

Patients with wounds are advised to have a nutrition consult, especially for complex wounds, wounds that are slow to heal, and when there are any concerns about the patient’s nutritional status. Such a consult addresses the following concerns, among others:

• Carbohydrates are the body’s source of energy. Glucose is the primary source of fuel for collagen synthesis, which is needed for wound healing. The types of carbohydrates consumed should be mainly complex carbohydrates, such as fruits, vegetables, and whole grains. These are also good sources of fiber, minerals, and vitamins.
• Protein is required for the restoration and production of enzymes that contribute to wound healing, cell duplication, and collagen and connective tissue creation. Increased protein levels are associated with better wound healing rates. The European Pressure Injury Advisory Panel, National Pressure Injury Advisory Panel, and the Pan Pacific Pressure Injury Advisory Panel (EPIAP/NPIAP/PPPIA, 2019) International Guideline recommends 1.25–1.5 grams of protein per kilogram of body weight daily for persons with a pressure injury and for those who are malnourished or at risk for malnourishment. However, the patient’s renal function and coexisting conditions must be taken into account when regulating protein intake. Several amino acids, such as L-arginine, glutamine, and cysteine, play vital roles in wound healing.
• Fats provide a concentrated source of energy as well as a standby source of energy in the form of deposited triglycerides in the adipose tissue. Healthy sources of fat include vegetable, olive, and nut oils, along with fatty fish, nuts and nut butters, and dairy products. Fats are required for cell membrane formation, and the demand for fatty acids appears to increase in the presence of a wound. Lipid constituents are required for tissue growth, collagen, and extracellular matrix synthesis.
• Micronutrients is another term for vitamins and minerals. These are critical for wound healing. Although several micronutrients play a role in the wound healing process, vitamin A, vitamin C, and zinc have been identified as the most important.
• During the inflammatory phase of wound healing, vitamin A is responsible for increasing the quantity of macrophages and monocytes in the wound bed. Thus, vitamin A deficiency impedes the transformation of monocytes into macrophages, which can slow or halt healing. Vitamin A also plays a part in activating cellular differentiation in fibroblasts and collagen production, and it promotes epithelialization. Vitamin A is found in eggs, fish, and dark green vegetables.
• Vitamin C is an antioxidant (an element that inhibits or reduces damage caused to cells by free radicals), which is crucial for collagen production. It also plays a vital part in the creation of new blood vessels and assists with iron absorption. Vitamin C is also a needed component in immune function. Vitamin C deficiency prolongs wound healing time, increases the risk for infection, and leads to weak collagen, which is the basis of scurvy. Good sources of Vitamin C include citrus fruits, leafy green vegetables, and tomatoes.
• Zinc is needed for protein metabolism, collagen production, and cell proliferation. Wound drainage can lead to a swift decrease in zinc, with resultant deficiency. This can cause diminished collagen strength, reduction in the rate of epithelial cell production, and poor wound healing. There is no clinical evidence to support zinc supplementation. High levels of zinc can impede wound healing. Good dietary sources of zinc include meats, seafood, beans, nuts, whole grains, and dairy products.
  (Baranoski & Ayello, 2020; Rosenthal, 2020; WebMD, 2022)

HYPERGLYCEMIA

Tight glycemic control is important in wound healing and preventing complications. Hyperglycemia can negatively impact the inflammatory phase of wound healing and the formation of granulation tissue. It can also result in decreased tensile strength of collagen and epithelial resurfacing. To maintain adequate wound healing, it is recommended to maintain blood glucose between 140–180 mg/dL (WOCN, 2022).

SMOKING

Tobacco contains a mixture of chemicals, many of which are highly toxic. Patients who smoke have poor wound healing in addition to suffering a number of other skin problems (wrinkling, premature skin aging, higher risks of squamous cell carcinoma, psoriasis, and hair loss). Smoking causes vascular constriction, which decreases circulation and leads to chronic wounds. Research has also demonstrated that patients who smoke experience more wound pain than those who do not smoke. This increase in pain sensation is due to chemicals in tobacco negatively affecting the body’s perception of pain signals (WOCN, 2022).

DEHYDRATION

Patients who are dehydrated may have impaired kidney function and reduced blood volume, leading to decreased blood pressure and perfusion, which can slow wound healing.

Healthcare Impediments

Medical care of wounds is an attempt to overcome obstacles to natural healing. In the course of managing a wound, clinicians reduce the amount of contamination, minimize the area that must be filled by new tissue, maintain moist granulation tissue, and protect the healing area. However, efforts at facilitating wound healing sometimes introduce new impediments.

PROBLEMATIC DRUGS, SOLUTIONS, AND OINTMENTS

Chemotherapy drugs negatively affect wound healing during the treatment period and immediately afterward. However, since they are an essential part of cancer treatment for many patients, it is important that the wound care team work closely with the patient’s oncologist to develop a safe therapeutic plan for wound care.

Steroids have a negative impact on wound healing when they are taken in doses greater than 30 mg per day. Glucocorticoids (e.g., Prednisone) limit the proliferation of fibroblasts and the production of collagen, thus making scars relatively weak. Vitamin A applied topically to the wound bed has been shown to help counteract the local effects of steroids on wound healing while not interfering with their systemic therapeutic value.

The antiseptic solutions 10% povidone-iodine, 3% hydrogen peroxide, and 0.5% chlorhexidine can slow wound healing by destroying healthy cells as well as infected ones. Antiseptics should always be used judiciously in wound care and for a limited period of time, usually 7–10 days.

Creams and ointments can also be impediments to wound healing. Silver sulfadiazine, used in infected wounds, must be thoroughly cleaned from the wound bed during dressing changes. Although early studies showed statistically faster healing rates when Neosporin ointment was used, bacitracin is more commonly used as an antibiotic ointment due to sensitivities to Neosporin. Moisturizing creams such as Eucerin and topical steroids such as triamcinolone should not be used in open wounds. Patients must be cautioned about the use of over-the-counter products in wound care and that nothing should be applied to the wound without first discussing it with their wound care practitioner.

X-RAYS

Ionizing radiation damages actively dividing cells. In wounds, the regrowing epithelium, newly growing blood vessels, and fibroblasts that form new connective tissue are likely to be damaged by a large dose of ionizing radiation. Normal X-ray imaging is usually not a problem. Cancer therapies, however, give relatively high doses of ionizing radiation, and in areas of the body exposed to radiation therapy, wounds heal poorly and infections are more common.