Wound Healing
Phases of Wound Healing
Whether wounds are closed by primary intention, subject to delayed primary closure or left to heal by secondary intention, the wound healing process is a dynamic one which can be divided into three phases. It is critical to remember that wound healing is not linear and often wounds can progress both forwards and back through the phases depending upon intrinsic and extrinsic forces at work within the patient.
The phases of wound healing are2:
§ Inflammatory phase
§ Proliferation phase
§ Maturation phase
The inflammatory phase is the body’s natural response to injury. After initial wounding, the blood vessels in the wound bed contract and a clot is formed.
Once haemostasis has been achieved, blood vessels then dilate to allow essential cells; antibodies, white blood cells, growth factors, enzymes and nutrients to reach the wounded area. This leads to a rise in exudate levels so the surrounding skin needs to be monitored for signs of maceration. It is at this stage that the characteristic signs of inflammation can be seen; erythema, heat, oedema, pain and functional disturbance. The predominant cells at work here are the phagocytic cells; ‘neutrophils and macrophages’; mounting a host response and autolysing any devitalised ‘necrotic / sloughy’ tissue.
During proliferation, the wound is ‘rebuilt’ with new granulation tissue which is comprised of collagen and extracellular matrix and into which a new network of blood vessels develop, a process known as ‘angiogenesis’.
Healthy granulation tissue is dependent upon the fibroblast receiving sufficient levels of oxygen and nutrients supplied by the blood vessels. Healthy granulation tissue is granular and uneven in texture; it does not bleed easily and is pink / red in colour.
The colour and condition of the granulation tissue is often an indicator of how the wound is healing. Dark granulation tissue can be indicative of poor perfusion, ischaemia and / or infection.
Epithelial cells finally resurface the wound, a process known as ‘epithelialisation’.
Maturation is the final phase and occurs once the wound has closed. This phase involves remodelling of collagen from type III to type I.
Cellular activity reduces and the number of blood vessels in the wounded area regress and decrease.
What is a Wound?
A wound may be described in many ways; by its aetiology, anatomical location, by whether it is acute or chronic, by the method of closure, by its presenting symptoms or indeed by the appearance of the predominant tissue types in the wound bed. All definitions serve a critical purpose in the assessment and appropriate management of the wound through to symptom resolution or, if viable, healing.
A wound by true definition is a breakdown in the protective function of the skin; the loss of continuity of epithelium, with or without loss of underlying connective tissue (i.e. muscle, bone, nerves)2following injury to the skin or underlying tissues/ organs caused by surgery, a blow, a cut, chemicals, heat/ cold, friction/ shear force, pressure or as a result of disease, such as leg ulcers or carcinomas.
Wounds heal by primary intention or secondary intention depending upon whether the wound may be closed with sutures or left to repair, whereby damaged tissue is restored by the formation of connective tissue and re-growth of epithelium4
Structure and Function of the Skin:
§ The skin is one of the largest organs in the body in surface area and weight.
The skin consists of two layers:
the epidermis and the dermis. Beneath the dermis lies the hypodermis or subcutaneous fatty tissue.
The skin has three main functions: protection, regulation and sensation.
Wounding affects all the functions of the skin.
§ The skin is an organ of protection. The primary function of the skin is to act as a barrier. The skin provides protection from: mechanical impacts and pressure, variations in temperature, micro-organisms, radiation and chemicals.
§ The skin is an organ of regulation.
The skin regulates several aspects of physiology, including: body temperature via sweat and hair, and changes in peripheral circulation and fluid balance via sweat. It also acts as a reservoir for the synthesis of Vitamin D.
§ The skin is an organ of sensation.
The skin contains an extensive network of nerve cells that detect and relay changes in the environment. There are separate receptors for heat, cold, touch, and pain. Damage to these nerve cells is known as neuropathy, which results in a loss of sensation in the affected areas. Patients with neuropathy may not feel pain when they suffer injury, increasing the risk of severe wounding or the worsening of an existing wound.
§
Theory of Moist Wound Healing
The principle of moist wound healing challenges the normal physiological process of wound repair; ‘dry healing’ seen by the formation of a scab. It is recognised that in moist occlusive / semi-occlusive environments, epithelialisation occurs at twice the rate when compared to a dry one.
Moist wound healing can be achieved with advanced wound care dressings; a wet environment can be detrimental as this can lead to maceration and tissue breakdown.
Moist wound healing is not suitable for all wounds. Necrotic digits due to ischaemia and / or neuropathy should be kept dry or monitored very closely (daily often).
These patients experience problems fighting infection. Modern wound dressings can be used but the wound needs to be monitored closely to identify for early signs of clinical infection and to prevent maceration. Skin barrier preparations which are easy to use, do not sting even on vulnerable or sore skin, such as LBF ‘no sting’ barrier wipes may be used around the wound if exudate levels are high and a risk of maceration is present.
Wound Classification
Wounds may be classified by several methods; their etiology, location, type of injury or presenting symptoms, wound depth and tissue loss or clinical appearance of the wound. Separate grading tools exist for Pressure Ulcers (EPUAP), Burns (Rule of Nines), Diabetic Foot Ulcers (Wagner / San Antonio) and General Wounds.
General wounds are classified as being:
§ Superficial (loss of epidermis only)
§ Partial thickness (involve the epidermis and dermis)
§ Full thickness (involve the dermis, subcutaneous fat and sometimes bone)
The most common method for classification of a wound is identification of the predominant tissue types present at the wound bed; i.e. black – necrotic and the respective amount of each expressed as a percentage. This classification method is very visual, supports good assessment and planning and assists with continuous reassessment.
Patient Assessment
Patient assessment is critical to ensure good wound healing outcomes. A ‘unified patient centred approach’ should be adopted which takes into account the systemic, regional and local factors which may affect wound healing. It is important to assess the patient and the wound to aid appropriate dressing selection and then accurate treatment interventions can be planned. A multi-disciplinary approach should always be considered.
Assess the Patient
Assess the patient and consider systemic factors which may affect wound healing. These include; co-morbidities / disease processes such as cardiovascular, diabetes, immunosuppressant conditions, carcinomas, psychosocial conditions, medication, age and nutritional status. Any known allergies should be recorded.
Assess the Regional Area
Regional factors to consider include vascular disease, infection and pain.
Assess the Local Wound Area
The local wound bed should be assessed in terms of the type and amount of each respective tissue type present (necrotic, sloughy, granulating) and also the level of pain, infection, exudate and odour present.
Assess the Current Dressing Regime
Assess the current dressing for signs of leakage and strikethrough and assess efficacy in terms of wear time, pain at dressing change and in situ.
At assessment the wound should be measured and the depth of tissue loss expressed as a grade. If the wound is a cavity, then all areas of undermining should be probed, measured and documented. Ideally all wounds should be mapped and photographed. A treatment plan should be selected providing clear rationale for the dressings selected and frequency of dressing changes
Dressing of Wounds
Wounds in some areas of the body are particularly difficult to dress, despite the wide range of dressing products available. This paper aims to set out some generic principles that may assist when dressing wounds in awkward areas.
Introduction
It is widely documented that patients with chronic wounds identify problems such as malodour, dressing leakage and pain as high on their list of priorities[1]. If these are not dealt with the patient may withdraw from social contact and become isolated because of embarrassment or curb their activities for fear of dressing leakage.
Despite the existence of a huge range of dressing products in a wide variety of shapes and sizes, dressing wounds in some anatomical areas continues to be a challenge for many clinicians. Although dressing manufacturers have designed products to cope with the curves and uneven textures of living human anatomy, these are usually limited to one or two sizes. However, it is possible to adapt these ready-made products.
Identifying patient needs
The first step in ensuring a good dressing fit is a thorough, holistic assessment of the patient. This must consider factors such as how the patient's lifestyle impacts on the dressing. For example, if the patient is an otherwise fit and healthy child it is likely that the dressing will be subjected to considerable wear and tear and this should be considered during selection. In addition, the patient may see other objectives as a priority over wound healing and meeting these is vital in obtaining concordance.
Previous dressings used should be reviewed and any problems that occurred considered. An example of this would be a dressing that always leaked from, or failed to stick at, one particular edge.
Adapting ready-made products
Once the patient's needs have been identified and the dressing requirements ascertained, the best solution may be to adapt an available dressing. Many standard square or rectangular products can be cut and folded to make appropriate shapes to fit different sizes of wounds. Pre-formed shapes designed for specific body areas such as the heel may also prove to be useful elsewhere on the body, for example in the axilla.
When cutting and shaping products a number of key principles should be borne in mind:
1. Follow local infection control guidelines to prevent infection and/or cross-infection
2. Always use sharp, clean scissors when cutting products to prevent shredding of dressing edges and contamination
3. Always cut across the peelable back on adhesive dressings, otherwise the backing paper will be difficult to remove
4. Round off cut edges to reduce the chance of uneven edges catching on bedding and clothing
5. For adhesive dressings, keep the backing paper as a template for future use; for non-adhesive dressings, trace the outline on to the packaging
6. Do not cut absorbent materials that contain super-absorbent powder or granules or dressings that liberate cellulose fluff pulp as this would release particulates into the wound
7. Most manufacturers recommend placing a dressing centrally over the wound. Consider the effect of gravity and place the dressing to account for the direction of fluid drainage
8. Do not apply dressings or tape with too much tension as this may cause blistering or a tourniquet effect
9. Always take care of the surrounding skin. Use of skin protection is generally recommended - for example skin protectant wipes or barrier creams
10. Bear in mind that although some dressings may provide padding and reduction in friction, they may not relieve pressure
11. Thin products conform better than their thicker counterparts and are less likely to roll at the edges. Although inherently less absorbent, if a thin dressing stays in place its use will be more cost-effective than that of a thicker dressing that leaks or rolls
12. To improve the adhesion of an adherent product, gently warm it by rubbing between the hands before application
13. Where necessary, carefully remove any hair from the area before applying a dressing.
Areas that clinicians may find difficult to dress include: ears, axillae, joints, hands, sternum, the peristomal area, buttocks and sacrum, feet, heels and digits. Other problematic areas that are more complex include peri-anal and perineal regions. Some of the principles discussed here may help when dealing with wounds in these areas but they have very specific problems outside the remit of this guide.
Ears
Occasionally patients develop pressure damage on their ears. This is most commonly caused by tubing or elastic from an oxygen mask held tightly in place to ensure patients receive adequate oxygenation. This problem is frequently compounded by wearing glasses. Similar problems also occur on the nose, either over the bridge or around the nostrils.
