Antimicrobial dressings


It is vital to ensure that the benefits of using antimicrobial dressings outweigh the potential negative effects on wound healing.


Other products which control bioburden by physical methods, e.g. by binding bacteria in exudate within the dressing, or by debridement, are not discussed within this document.


Wound bioburden and antimicrobial dressings All wounds contain micro-organisms, yet the majority are not infected and go on to heal successfully. In these cases, the bioburden of the wound and the host’s immune system are in balance. However, if this balance shifts in favour of the microbes, or if wound healing is impaired, the micro-organisms (usually bacteria) multiply and invade tissues resulting in a prolonged and inappropriate inflammatory response, tissue damage and delayed healing and, if left unchecked, systemic illness9


. When this shift in balance


occurs, immediate intervention is needed. From a clinical management perspective, it is this recognition of the state of the wound with respect to bacterial load that is a challenge10


. Definition


made easy


Box 2 outlines the relationship between wound bioburden and the need to intervene with antimicrobial dressings.


It is important to consider if the wound is not healing because of a rising bacterial load (in which case antimicrobial dressings may assist wound healing), or if the bacterial load is increasing because the wound is not healing (antimicrobial dressings are unlikely to assist wound healing but may help prevent spreading infection).


Infection Wound infection is defined as the presence of multiplying organisms which overwhelm the body’s immune system. It results in toxin release that is likely to delay wound healing and result in active signs and symptoms of infection (Box 2).


Identifying wound infection Identification of wound infection is a clinical skill and clinicians should be aware of the signs and symptoms, e.g. erythema, pain, swelling, localised heat and purulence, particularly those that occur in the wound type they encounter most frequently (since infection may produce


Box 2Wound bioburden and the need for antimicrobial intervention11, 12 Term


Contamination Colonisation


Micro-organisms do not increase in number or cause clinical problems. Wound healing should occur successfully without topical antimicrobial dressing intervention


Micro-organisms multiply, but wound tissues are not damaged. Wound healing should occur successfully without topical antimicrobial dressing intervention UNLESS there are concerns about the patient’s overall health or immune system function


Critical colonisation/ covert infection1


Infection


Micro-organisms multiply to an extent that wound healing is impaired. While classical clinical signs and symptoms of infection may be absent (pain, heat, erythema, oedema and purulence), more subtle local signs and symptoms may be present especially in chronic wounds1, 7, 13


. Topical antimicrobial dressings are indicated


Bacteria multiply, healing is disrupted and wound tissues are damaged (local infection). The wound may extend into previously healthy tissue. Topical agents may control bacterial growth and improve the wound healing environment. Patients with poor host defence may need systemic antibiotic therapy. Bacteria may produce problems nearby (spreading infection), or cause infection throughout the body (systemic infection), for which both systemic antibiotics and topical antimicrobial dressings are indicated


different signs and symptoms in wounds of different types and aetiologies1, 7


.


In acute or surgical wounds in otherwise healthy patients, infection is usually obvious. However, in chronic wounds and debilitated patients, diagnosis may rely on recognition of subtle local signs or non- specific general signs (such as malaise and loss of appetite). Other criteria include7, 13 n Increased discharge n Delayed healing n Wound breakdown


:


n Pocketing at the base of the wound n Epithelial bridging


n Unexpected pain or tenderness n Friable granulation tissue


n Discolouration of the wound bed n Abscess formation n Malodour.


A thorough patient history and good clinical assessment skills should enable the clinician to establish if the wound is infected and if antimicrobial intervention is necessary14


.


It is important to recognise and differentiate the signs and symptoms of localised, spreading and systemic infection.


How do I recognise when a wound is at risk of infection? Clinicians need to be extra vigilant of patients with an increased risk of wound infection. These include those who are taking medication which dampens down the immune system, such as corticosteroids, cytotoxic agents and immunosuppressants. Also, those with comorbidities such as diabetes mellitus, an immunocompromised status, hypoxia and poor tissue perfusion due to anaemia or arterial/cardiac/ respiratory disease, renal impairment, malignancy, rheumatoid arthritis, obesity and malnutrition are at an increased risk1


. S.2


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