Wound Bed Preparation
Sharon A. Aronovitch, PhD, RN, ACNS-BC, CWOCN-AP
Excelsior College, Albany, NY
Aronovitch SA. Wound bed preparation. Consultant. 2012;52(6):459-460.
When wounds become chronic—ie, have not proceeded expediently through the four stages of healing and/or have languished for 3 months or more, usually “stuck” in the inflammatory or proliferative phase—a number of patient and wound factors must be considered and addressed. Patient factors include comorbid conditions that affect healing (eg, diabetes mellitus, venous insufficiency, and arterial disease). Wound factors include compromised tissue viability, infection and inflammation, moisture balance, and wound edges that fail to come together. An evidence-based, patient-centered approach will incorporate condition-specific management such as improved glucose control with wound care that removes the obstacles that prevent healing progression.
FOUR STAGES OF HEALING
All wounds heal by progressing through four specific phases. During the first phase, the vascular response, which is initiated on wounding, bleeding stops when blood vessels constrict, the coagulation process ensures clotting, fibrin mesh forms for temporary wound closure, and various body fluids help cleanse the wound. In the second (inflammatory) phase, vasodilation, capillary permeability, polymorphonuclear leukocyte activation, and macrophage migration occur and/or increase, and the body provides inflammatory regulators, growth factors, enzymes, and nutrients to cleanse the wound and mediate the healing process. The actual “filling in” of the wound occurs during the proliferative phase, as tissue granulation, contraction, and epithelialization provide the connective tissue and bring the wound edges together. Finally, during the maturation phase, tissues strengthen and remodel toward complete healing. It is worth noting the following:
- Not all wounds regenerate with the same tissue. Unlike a laceration or abrasion, deep wounds heal with scar tissue.
- Remodeling does not mean the lost tissue is reconstructed in the wound bed.
Chronic wound patient assessment usually reveals an underlying cause for nonhealing—ie, what is thwarting the wound closure process. Some systemic factors include diabetes and other metabolic conditions, respiratory and vascular disorders that impair the flow of blood to the wound, immune conditions or therapy, and medications. Diabetes can affect circulation (fatty deposits in the arteries subsequent to the disease can slow blood flow), sensation (neuropathy in the feet can lead to unnoticed injury), and the immune system (compromised by high blood glucose levels).
Venous ulcers, the most common and most costly lower limb wounds, are the result of vein obstruction or valve, vein, or calf muscle dysfunction. Arterial ulcers are related to insufficient blood supply and like venous ulcers almost always occur in the lower extremities. Pressure ulcers develop as a result of unrelieved pressure, usually over bony prominences.
When to refer. The physician presented with a chronic wound should be able to distinguish from among these diagnoses and assess for patient factors that need to be managed before local wound therapies can commence with success. Patients with uncontrolled glucose levels may require the help of an endocrinologist. Arterial ulcers require the skills of a vascular surgeon or interventionalist to address the underlying ischemia.
A practical mnemonic (TIME: tissue, infection/inflammation, moisture, edge of wound) was developed to help clinicians effectively prepare the chronic wound to regain its ability to heal. Tissue (T) must be assessed for viability. Necrotic (nonviable or deficient) tissue or slough—ie, tissue that appears black, brown, yellow, or fibrinous—and eschar—dried out, leathery, thick tissue—is a barrier to healing and can conceal areas in which bacteria can proliferate. Such tissue should be removed unless leaving it serves a protective purpose or the patient is not a good surgical candidate and removal would do more harm than good.
Thus, debridement is the first step in wound bed preparation. Debridement may be performed surgically, through use of products that contain enzymes (eg, Healthpoint Biotherapeutics’ Santyl) or facilitate mechanical tissue removal, through use of maggots (biological debridement), or autolytically (utilizing the body’s own substances). The debridement method should be chosen based on wound type, size, position, and moisture; anticipated pain; the length of the procedure; and how these factors will affect the patient.
Infection and/or inflammation (I) must be addressed. Wounds with high bacterial counts are less likely to heal. The four classic signs of infection are color, increased temperature, pain, and swelling. Chronic wounds additionally may display increased exudate, increased tenderness, friable granulation tissue, foul odor, and increasing size (including depth).
Addressing infection or inflammation is subject to where the wound is situated on the bacterial continuum—contaminated (non-replicating organisms), colonized (organisms are present but not causing injury to the patient), critically colonized (organisms are beginning to inflict local tissue damage), or infected (organisms are sufficient to cause systemic problems). Contaminated or colonized wounds may be managed with cleansing and appropriate local treatment (dressings); antiseptic use should be selective according to product indications. Topical antimicrobial and silver-containing product use may be initiated when the wound is determined to be critically colonized; antibiotics should be reserved for systemic infection.
Bacteria may be quantified via biopsy, swabbing, or fluid aspiration. Among the pathogens requiring immediate attention regardless of quantity are Mycobacteriaceae, anthrax bacillus, toxin-producing Corynebacterium diphtheriae, Erysipelothrix spp, invasive dimorphic fungi, and some parasitic organisms. Gram-positive organisms and enterococci, beta-haemolytic streptococci, and Staphylococcus aureus tend to colonize during the first 4 weeks of wound development. After the initial 4 weeks, anaerobic organisms such as Proteus spp, Escherichia coli, and Klebsiella spp proliferate. Often, these organisms combine for a more virulent synergistic effect.
Topical and systemic management of infected wounds can be enhanced by relieving local pressure, managing stress factors, controlling edema, improving glycemic control, revascularizing ischemic tissue, improving nutrition, decreasing immunosuppressive therapy (if possible), and encouraging cessation of smoking and drug use.
Wound moisture (M) needs to be kept in balance. Exudate can be beneficial to the healing process, but in excess it can inhibit healing. As noted in the first article in this series (“Assessing and Managing a Moist Wound Environment,” CONSULTANT, March 2012, page 214), individual dressings are specifically designed to maintain a good moisture balance; product indications for exudate control or moisture facilitation should be carefully scrutinized, always with an appreciation for wound etiology.
The wound edges (E) ultimately must advance toward one another. In chronic wounds, the epidermis does not migrate across the wound bed, the result of compromised fibroblasts and keratinocytes and/or infection. Several products are designed to enhance wound edge progression, and include various skin substitutes, skin grafting, and other biological or adjunctive therapies. Physicians are encouraged to consult wound specialists or surgeons when more invasive approaches seem necessary.
The physician faced with a patient with a chronic wound should be mindful of the fact that the wound may be stalled in the inflammatory or proliferative phase of healing. Being aware of patient factors that can stymie healing, enhancing viable tissue, treating infection/inflammation, maintaining a wound environment that promotes moisture balance, and facilitating wound edge advancement will help re-start the healing process. Referral for specialized wound care management is a factor of the patient’s comorbid conditions and whether the physician is familiar with and experienced in providing the elements of TIME. In all cases, the ability of the patient or caregiver to adhere to and manage the prescribed treatment or dressing/product must be a priority.
Dr Aronovitch is faculty program director, graduate nursing program, Excelsior College, Albany, NY.
[Editor’s note: This article is the second in a series on wound management. The first article (“Assessing and Managing a Moist Wound Environment,” CONSULTANT, March 2012, page 214) is available on our web site at https://www.consultant360.com/article/assessing-and-managing-moist-wound-environment.]