Hard-to-heal wounds Made Easy
21/11/11 | Complex wounds, Wellbeing and concordance | Vowden P.
Most people have, at some stage in their life, experienced a wound. For the majority, healing is a simple and rapid process and, although the wound may leave a visible scar, it is not associated with persistent pain, excessive exudate, odour or distress. In some patients, healing is prolonged and accompanied by major symptoms, which adversely affects their quality of life. Clinicians therefore face the dual challenge to meet patient expectations of prompt and trouble-free wound healing, and to recognise and act appropriately for those patients in which wound healing may be prolonged.
What is a hard-to-heal wound?
A hard-to-heal wound has been defined as one that fails to heal with standard therapy in an orderly and timely manner. This definition applies equally to both acute and chronic wounds and is independent of the wound type and aetiology.
Many wounds, particularly those in an elderly population with significant comorbidities, prove challenging to manage. Audit data from both Bradford[2-5] and Hull[6,7] has demonstrated that delayed healing occurs in a variety of wound types. Although delayed healing appears to be common, it is frequently not recognised early enough and can pose a major problem, increasing clinical workloads and cost.
Why do some wounds not heal?
One of the characteristics of multi-celled organisms is the ability to replicate and self-repair. The normal healing process is a well-orchestrated, complex and interlinked series of four well-recognised overlapping phases.
The process starts with haemostasis, progresses through a destructive inflammatory phase and then a restorative proliferative phase. It finishes with remodelling of the wound area. In this process, components of the extracellular matrix, interacting with recruited cells, play an important role in coordinating key processes in healing. The normal process can be interrupted at any stage and is vulnerable to a variety of intrinsic and extrinsic inhibitory factors.
What factors affect healing?
Wound aetiology, patient age and the presence of significant comorbidities all impact on the healing process, as do factors such as wound size and depth, location of the wound, wound duration and the presence of a heavy bioburden.
Age and hard-to-heal wounds
Age affects healing in a number of ways. Elderly patients tend to have significant comorbidities and are more likely to be on multiple medications, which impact on healing. Ageing itself also affects both the rate and quality of the healing process. Large wounds often take longer to heal than small wounds and, as such, are more likely to develop complications such as infection, which may then slow healing. For chronic wounds, size may relate to the severity of the underlying causative condition and the status of the surrounding skin, both of which have the potential to delay healing. In addition, the persistent inflammatory process associated with non-healing and long wound duration degrades the extracellular matrix and vascular supply to the wound, resulting in poor cellular function and senescence - a loss of a cell's power to divide and grow.
Patients with hard-to-heal wounds may have a number of comorbid conditions that affect the healing process. Diabetes is a significant factor and can affect healing in the following ways:
- Cell membrane structure may be altered, affecting cell motility and deformability and the cellular response to local and systemic signalling proteins
- The extracellular membrane may be damaged by non-enzymatic glycosylation, affecting both its structure and function
- The inflammatory response and response to infection may be modified by changes in both chemotaxic and phagocytic function of white cells
- The blood supply to the wound area may be reduced by both occlusive arterial disease, changes in the distribution of blood flow (shunting) and a reduction in angiogenesis function (the growth of new blood vessels) affecting the ingrowth of new blood vessels to the wound
- The presence of a neuropathy allowing ongoing trauma to the wounded area.
As described, wound healing is dependent on cell replication, the formation of a new supporting matrix and the elimination of damaged, necrotic, foreign or infecting material. All of these processes are energy dependent and only occur effectively in the presence of an adequate blood supply and the delivery of nutrients and oxygen to the wounded area.
This process is impaired in the presence of systemic disease (cardiac and respiratory failure), regional ischaemia (peripheral vascular disease) and local ischaemia within the wound, secondary to poor neo-vascularisation and angiogenesis.
Infection and Inflammation
Inflammation is a necessary component of the healing process, but is detrimental if it continues at an inappropriate level beyond the initial phases of healing, or is stimulated by other events such as infection within a wound. Diseases such as rheumatoid arthritis and medication (eg steroids) alter the inflammatory process. This can have a detrimental effect on healing.
The reason for delayed healing may not be related solely to an abnormality within the wound itself (Box 1). Available healthcare resources, product availability and the skill and knowledge of healthcare professionals may also influence outcome and healing time, as will the complexity of the wound itself.
Can you predict when a wound is hard to heal?
In most wounds, healing progress should be visible within a four-week period. Figure 1 outlines the process of recognising a hard-to-heal wound and provides a useful check list to allow for the early identification of potentially slow healing wounds.
Much can be gleaned from a detailed initial wound and patient assessment when issues such as ischaemia, associated comorbidities and infection, amongst others, may be identified and a broad idea of healing potential derived. Such assessments must, however, be accurate and reproducible if treatment is to be delivered effectively.
Recognition of non-healing demands a careful reassessment of both the wound, the region of the wound, the patient and the systems of care so that both extrinsic and intrinsic barriers to healing may be identified. For many wounds one or more of the following three key intrinsic abnormalities will be present and delay or prevent healing:
- Abnormal or persistent inflammation.
In addition, the presence of exposed bone or tendon, on which it is difficult to establish healthy granulation tissue, are recognised as obstacles to rapid wound healing[11,12].
The more complex the wound in relation to the underlying pathology and comordibites, the greater the likelihood that the wound will be hard to heal.