The art - and science - of wound healing

Wound care is a pivotal role for the practice nurse. Knowledge of the physiology of the healing process and the science of wound management are rapidly expanding fields that nurses need to stay abreast of if they are to provide effective treatment to patients.

The healing process and the management of wounds are both simple and complex. From a simplistic viewpoint you should, in essence, use:

• A wet dressing for a dry wound
• A dry dressing for a wet wound
• An antimicrobial dressing for a colonised wound.

Most people, given a few tips, can provide an ideal wound healing environment. However, the complexity of wound care is such that even those with years of experience will never be able to call themselves 'experts'. The science of wound healing progresses so quickly that keeping abreast of all the developments would require the daily reading of an impossible number of journals. Nevertheless, wound healing is one of the most satisfying roles undertaken by nurses. Not only can it change the life of the individual with a wound, but in some cases, can also save that life.

Management of traumatic and surgical wounds has had a chequered history. For example, in 1346 at the Battle of Crecy, France, foot soldiers were issued with cobwebs to staunch haemorrhage caused by trauma. Two centuries later, the eminent surgeon Ambroise Pare rejected boiling oil as a primary dressing after amputation, preferring a mixture of oil of turpentine, rosewater, and egg. After running out of the usual recommended remedies, Pare declared that,

'Man may dress the wound, but only God can heal'.

This is as true today as it was in Pare's time. Our expensive and intelligent dressings can still only provide an optimum wound-healing environment to prepare the wound to heal itself. In other words, it is not the use of particular dressings that heal the wound, but the selection of the right dressing for the individual wound, based on comprehensive assessment, experience and up-to-date knowledge, that will lead to healing.

THE HEALING PROCESS

Wound healing involves a complex series of interactions between different cell types, cytokine mediators, and the extracellular matrix. There are four phases of normal wound healing:1

1. Haemostasis - formation of a stable clot through aggregation of platelets and formation of fibrin mesh. Platelets also secrete cytokines that initiate the subsequent stages of the healing process.

2. Inflammation - erythema, swelling and warmth, often associated with pain. Plasma and polymorphonucleocytes are released into the surrounding tissue and form the first line of defence against infection. Macrophages provide the second line of defence and also secrete a variety of chemotactic and growth factors to direct the next phase.

3. Proliferation - characterised by the presence of 'pebbled' red tissue in the wound base. This phase involves the replacement of dermal and, in deeper wounds, sub-dermal tissue, and contraction of the wound.

4. Remodelling - this can take up to 2 years and involves remodelling of the dermal tissues to provide greater tensile strength.

Although the wound healing process is continuous each phase is distinct, with each phase overlapping the next. However, these interactions only occur in the acute wound and not in the complex chronic wound. To enable the chronic wound to progress the underlying pathology must be addressed and an ideal dressing selected.

Much is written about the ideal wound healing environment,2-4.and it is usually directed at the type of dressing that should be used. This is not necessarily useful as the type of dressing required relies on how the underlying pathology is addressed. For example, if the wound is a pressure ulcer, then even the most appropriate dressing will never heal the wound if the pressure is not relieved; if it is a venous leg ulcer, then the wound will not heal if compression is not properly applied. Likewise, an arterial wound requires the input of a vascular surgeon to ensure the internal problem is rectified so that the dressing can then provide the correct environment to encourage the wound to heal. If a wound is colonised with bacteria there is a potential for wound healing to be delayed, due to raised chronic proteolytic enzymes and a raised pH, unless the bacteria are reduced. Any or all of these problems need to be addressed first so that the wound can then progress toward healing.

pH IN DELAYED WOUND HEALING

The normal pH of human blood is slightly alkaline at between 7.35 - 7.45. Above or below this range means symptoms and disease.⁵ The role of wound bed pH, which has a natural, slightly acid extracellular pH of around 6, has proven to be of fundamental importance during the healing of chronic wounds.⁶ Prolonged chemical acidification of the wound bed has been shown to increase the healing rate in chronic venous leg ulcers.⁷

In the acute phase, protease levels rise in response to wounding and, when present in appropriate concentrations, they promote cell migration and activate growth factors. Protease levels then decrease as the wound heals. In chronic wounds, however, protease levels rise and remain elevated and the pH is raised to an alkaline level. This becomes damaging to wounds and the surrounding tissues. (Figure 1) If a pH value is taken in the wound in figure 1, it will be found to be high, possibly as high as 8.4. To promote healing of this wound it is important to lower the wound pH, and subsequently the level of damaging proteolytic enzymes. This can easily be accomplished through use of dressings such as honey, iodine cadexomers and silver dressings. All of these dressings will lower the pH and reduce bacterial colonisation.

There is, however, some debate about whether pH is always expected to be low.⁸ Research is ongoing and methods of treatment may change in the future as our understanding increases. In the meantime, the Eastbourne Wound Healing Centre (EWHC) continues to treat wounds successfully by reducing the level of pH in wounds.

BACTERIAL COLONISATION

Bacterial colonisation, as described above, can be destructive in a wound. However, colonisation is often misdiagnosed and this can lead to inappropriate and sometimes dangerous use of antibiotics leading to Clostridium difficile or methicillin-resistant Staphylococcus aureus (MRSA). Colonisation should be simple for the nurse to assess and deal with through use of antibacterial dressings, whereas clinical infection should nearly always be dealt with using systemic antibiotics. There is no place for topical antibiotic therapy in this situation. The signs and symptoms that can help differentiate between clinical infection and bacterial colonisation are listed in Table 1.

With experience it may be possible to identify the colonising bacteria in a wound from the colour and the odour. For instance, most nurses could identify the common Pseudomonas aeruginosa. It produces a bright green discharge in a wound and has a sweet, almost musty odour. Pseudomonas is easily treated with either honey or silver dressings whereas maggots do not survive well in the pseudomonas environment. Pseudomonas colonisation (in the author's experience) is often painful and destroys the surrounding tissues causing a wound to enlarge.

Staphylococcus aureus often has a muddy, red/brown colour and an odour of old blood. This can be reduced through use of honey, maggot therapy, polyhexamethylene biguanide (PHMB) dressings, Sorbact or silver dressings. This bacterium quite often sits in the slough on a wound but does not necessarily interfere with healing.

Haemolytic streptococcus may sometimes be identified because there are clots of blood in the dressing on removal. This particular bacterium can destroy a wound very quickly. If any wound is enlarging and has clots of blood, a swab should be taken and antibiotics requested. However, swabbing a wound is no longer common practice as it is unnecessary if the above rules of assessment are applied.⁹ A swab will only direct the prescriber to what is sitting on the surface of the wound and not to what could potentially be present in the host tissues beneath the wound.

THE RIGHT DRESSING FOR THE RIGHT WOUND

Once the holistic assessment of the patient is complete, the underlying pathology addressed and the wound examined, then selection of the dressing, using the wound healing continuum,10 (Figure 2) should be straightforward.

If the wound is dry, which is usually at the black, necrotic end of the continuum, then wet dressings such as hydrogel sheets are required. These should continue to be used until the wound begins to autolytically debride and produce high levels of exudate. Once the wound becomes 'wet' then drier dressings are required, such as alginates, hydrofibres or superabsorbent dressings. As the wound progresses towards the red and pink area foams and protective dressings are required.

If the wound is colonised, antibacterial dressings such as honey, silver, PHMB, Sorbact and iodine cadexomers are required to reduce the colonisation of the wound.

Once the wound enters the red or granulating phase, then aggressive cleansing of the wound should never be undertaken as it can damage the newly forming blood vessels in the base of the wound.

THE PATIENT'S PROBLEM

The actual problem experienced by patients is often not the wound itself, but the manifestation of the wound symptoms. Pain, exudate loss and odour can be all prevailing and can ruin quality of life for any patient at any age. Wound healing is about treatment of the patient and their wound and not about managing the symptoms. Placing Gamgee pads to mop up fluid or carbon to reduce odour is management of symptoms and not dealing with the cause. Once the cause is identified, the pathology addressed and an appropriate dressing selected then it is less likely that the wound will overtake the patient's social life and they will be better able to deal with it.

THE EWHC APPROACH

The Eastbourne Wound Healing Centre (EWHC) has a very successful healing rate.¹¹ There may be many reasons for this, but the holistic and individual care that each patient receives is likely to be a major factor. Each patient:

• Is greeted at the door by a 'welcomer' who offers tea or coffee and will chat to the patient while they wait
• Sees the same Specialist Clinician at each visit
• Is given an hour for treatment
• Has access to the multidisciplinary team for individual specialised problems
• Has access to the most appropriate dressing for their individual requirements

EWHC has an open door policy for any clinician who wishes to visit. This has dual benefits. It provides a learning environment for clinicians and also, by giving patients access to clinicians who are learning, promotes the patients' confidence and belief that they are being treated by specialists. This confidence may help the patient relax and stress reduction can only assist in the fight to heal the wounds.

It should also be remembered that pain has a physical manifestation. It is a stressor and will reduce the healing potential in a wound. Pain management is therefore an important part of wound management.

CONCLUSION

It is increasingly clear, through both research and clinical practice, that healing will only occur when:

• There has been a holistic assessment of the patient
• The underlying pathology is addressed
• Pain is relieved
• Psychosocial needs are met
• An educated diagnosis has been made
• Appropriate resources are available, and
• Resources are intelligently used.

It is these parameters for wound healing that form the basis of patient treatment

At the beginning of this article, we said that wound healing is both simple and complex. The patient's pathology must be addressed and pain reduced. This all belongs to the science of wound healing. The selection of dressings is a mixture of art and science... the 'art' depends on continued experience, but we should also be constantly aware of advances in the 'science' and be open to change our practice in line with emerging evidence.

Nevertheless, wet dressings on a dry wound, dry dressings on a wet wound, with antibacterial to any wound with odour is a simplistic, but effective approach, and, as the wound heals, you will be able to bask in the satisfaction of a job well done!

REFERENCES

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5. Majno G, Joris I. Cells, tissues and disease: principles of general pathology. 1996. Oxford. Blackwell Science
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10. Gray D, White RJ, Cooper P. The wound healing continuum. In White RJ, ed. The Silver Book. London. Quay Books. MA Healthcare Ltd. 2003 11. Sayer A. Cost savings in wound care clinical management. Practice Management 2009; October: 26-8