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Managing wound malodour: from antibiotics to honey

Una Adderley
RGN DN BSc BA
Tissue Viability Prescribing Specialist Nurse Scarborough, Whitby and Ryedale PCT
E:una.adderley@acute.sney.nhs.uk

Wound malodour is usually deeply distressing to both patients and carers. Neal's patient-centred definition that a malodorous wound is "any wound assessed as being offensive (smelly) by the patient, carer or practitioner" is a useful reminder that smell is an individual experience.(1) Malodour may be closely linked with fear of advancing disease, and the memory of malodour may cause distress even after the death of a patient.(2)
The subjective nature of odour can make assessment difficult for the clinician. Using a scoring tool (see Table 1) can ensure that the clinical team share a common perception of the extent of the problem and any changes. However, the ethics of using such a tool should be carefully considered if it is possible that the use of such a tool may increase a patient's awareness or anxiety regarding the issue of malodour.

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Causes of malodour
Malodour in wounds can be caused by necrotic tissue, infection or heavy colonisation by microbes, stale exudate, or a combination of all three. Effective treatment can begin only when the cause has been identified.
Healthy skin can become necrotic tissue when the blood supply to the skin becomes impaired, leading to tissue hypoxia. This can be due to an enlarging tumour under the skin or a "fungating tumour" that extends into the skin structure and that ruptures or occludes blood vessels. Pressure damage in immobile patients and ­arterial occlusion from atherosclerosis will also lead to necrosis from tissue hypoxia. Wounds filled with debris, slough and necrotic tissue are an ideal breeding ground for anaerobic bacteria, which cause malodour.
Infection may be the primary cause of tissue breakdown as well as secondary to necrosis. Malodorous wounds usually contain at least two anaerobic bacteria in addition to aerobic bacteria.(4) Anaerobic pathogens destroy healthy cells by competing for available oxygen supplies and producing toxins that damage healthy tissue. Malodour occurs when the anaerobic bacteria break down proteins in dead tissue, leading to tissue liquefaction and the release of volatile fatty acids with pungent odour.
Heavy colonisation of a wound may also lead to malodour, although a malodorous wound is not necessarily clinically infected. The criteria for wound infection includes: abscesses, cellulitis, discharge, delayed healing, discolouration, friable, bleeding granulation tissue, unexpected pain, tenderness, pocketing/bridging at base of wound, abnormal smell and wound breakdown.(5) Without these signs, a wound is more likely to be heavily colonised with the wide variety of skin flora and fauna that usually exist on the surface of the skin but generally cause no problems.
Stale exudate can also be a source of malodour. Modern dressings are designed to minimise the frequency of dressing changes to promote healing. However, infection or excess exudate may necessitate more frequent dressing changes, as warm, moist places can become malodorous. Most people choose to wash sweaty feet and change their socks frequently to avoid malodour; malodorous wounds require similar attention.

Managing malodour
When managing malodour, the primary aim should be to prevent or alleviate the underlying cause, but in some situations, such as advancing fungating cancer or arterial disease, this may not be possible.
Malodorous wounds should receive gentle wound cleansing to wash away stale exudate; cleansing and dressing changes should be as frequent as necessary to minimise odour. Debridement of slough and necrotic tissue will reduce the focus for pathogenic bacteria, although some malodorous wounds will be fragile and require very gentle debridement. For example, fungating wounds are prone to bleeding, and autolytic debridement may be the only safe option.
Infection should be treated with the appropriate systemic antibiotics. Bacterial swabs may help identify which organisms are likely to be causing malodour, but cultures for sensitivity may identify only a broad range of skin flora or fauna without specifically identifying the causative agents. A detailed request form that clearly describes both the nature of the wound and the clinical problem will help the microbiologist select the sensitivity test most likely to identify the problem-causing agent. 
Systemic treatment such as oral metronidazole is often the treatment of choice, but oral antibiotic therapy can have unpleasant side-effects and is not always effective. When a malodorous wound has an impaired blood supply, oral systemic antibiotics may not reach the wound site. Topical applications of antimicrobials such as metronidazole gel, or the use of antibacterial dressings that contain cadexomer iodine, honey, silver sulphadiazine or nanocrystalline silver may be more effective.  However, unless the underlying cause can be alleviated, the problem will recur, and the clinician should consider the need for long-term management. 
In the case of heavy colonisation it may not be necessary to use systemic antibiotics. A topical broad-spectrum antimicrobial, such as the slow-release silver-impregnated dressings that have recently become available, may be sufficient to correct the bacterial balance of a wound. At present, there is no evidence to suggest which silver- impregnated dressing is superior in clinical performance. Silver-impregnated dressings are currently available on prescription in the form of foams, hydrocolloids, soft polymer wound contact layers, spun hydrocolloids and barrier dressings. It would seem logical to select dressings based on the conditions of the wound. For example, if a spun hydrocolloid would have been the appropriate choice for an exudating wound with suspected heavy colonisation, then a silver-impregnated spun hydrocolloid would have the additional benefit of an antimicrobial.
Most manufacturers of silver-impregnated products are suggesting there should be evidence of improvement within 2 weeks of treatment. Since an antimicrobial should restore the bacterial balance within a wound, it is unlikely that treatment with the antimicrobial will need to continue until healing occurs. A course of up to 4 weeks is usually sufficient. However, in some cases, wounds will begin to deteriorate once the antimicrobial dressing is ceased. In these cases, the manufacturers recommend a longer course of treatment.
Another recent addition to the Drug Tariff is manuka honey-impregnated dressings. Although there is no conclusive research evidence to support the use of honey, it has attracted the interest of both patients and clinicians. The manufacturers of these dressings present case studies to show the effectiveness of honey in decreasing malodour. However, the application of honey can increase exudate levels, which may  be problematic.

Exudate
Infection and malodour are often accompanied by excess exudate. Effective exudate management is essential to prevent saturated dressings that will quickly become stale and offensive. Where appropriate, patients can be encouraged to undertake their own dressing changes so that they can change dressings when they feel the need, rather than being dependent on the clinician. Activated- charcoal dressings will absorb malodour, but since moisture inactivates charcoal, saturated dressings will become ineffective. Occlusive dressings may help contain malodour, and wound drainage pouches can sometimes provide a solution for excessive exudate. Deodorisers can mask odour, but patients and carers can find the scent of the deodoriser more overpowering than the malodour. 
Like many sensory signals, malodour alerts us to a condition requiring attention. In some cases, malodour may act as a warning sign of impending infection, and prompt action may enable the clinician to reduce this risk. In other cases, it may not be possible to cure the condition, but effective management of malodour is important to promote quality of life and the patient's sense of wellbeing.

References

  1. Neal K.Treating fungating lesions. Nursing Times 1991;87(23):84-6.
  2. Doyle D.Domiciliary ­terminal care. Edinburgh:  Churchill Livingstone; 1987.
  3. Haughton W, Young T. Common problems in wound care: malodorous wounds.Br J Nurs 1995;4:959-63.
  4. Collier M. Malodour and infected wounds. A patient-centred approach. Leg Ulcer Forum 2001;14:12-4.
  5. Cutting K, Harding K.Criteria for identifying wound infection.J Wound Care 1994;3:198-201.