Wound dressings: an introduction

There are many wound dressing products currently available for the management of all wound types. Before using a wound dressing, it is important that all healthcare practitioners are aware of:

• properties of the dressing
• recommended clinical indications for use
• evidence supporting use
• manufacturer information sheet

Wound dressings can vary depending on the materials used and how they are made, the identified properties of the product and recommended clinical indications (manufacturers information). A wound dressing can be classified as:

Passive – a covering that simply keeps the wound ‘out of sight, out of mind’.

Interactive – a modern wound management product that has been designed to optimise the local wound environment to promote healing.

Active – a wound management product that is designed to correct a known deficiency in the local wound healing environment, and has been indicated to stimulate the wound healing process (Collier, 2003). Examples include negative pressure wound

Many absorbent materials are non-occlusive, permeable dressings that allow moisture to be absorbed and evaporated into the atmosphere. Many absorbent dressings are made of a soft viscose, polyester bonded pad that may or may not have an external polyethylene contact layer. Product performance depends on maintenance of position, absorbency capacity fluid retention, confirmability of material and weight of product when wet. The use of other skin-care products may affect the absorbency of these dressings.

Indications:

• protection for primarily closed or lightly exuding wounds
• more absorbent versions (usually thicker) may be suitable for the management of some chronic wounds

Precautions:

• bleeding wounds, especially arterial bleeds
• maceration – skin damaged at a cellular level by the presence of moisture

These dressings are made of absorbent polymers, some of which expand when they absorb fluid. More absorbent types may be used for chronic wound management – defined as a heavily exuding wound that can produce 5 ml/10 cm2 of exudate every 24 hours.

Indications:

• protection
• lightly exuding and chronic wounds

Precautions:

• bleeding wounds, especially arterial bleeds
• maceration – skin damaged at a cellular level by the presence of moisture
• excoriation – a skin abrasion that is usually superficial and results from mechanical injury

Manufactured from salts of alginic acid (sourced from brown seaweed). On contact with wound exudate, an ionic exchange occurs in the alginate, leading to the formation of a hydrophilic gel. This reaction depends on the amount of guluronic and mannuronic acid used in manufacture, which also affects the product’s ability to absorb exudate, retain its shape, and removal of the dressing from the wound. The dressing can be available as a sheet, rope or cavity filler. Alginate dressings can absorb 15–20 times their weight in fluid, with capacity ranging from 15–25 gm/100 cm2.

Indications:

• absorption
• wounds producing moderate to large volumes of exudate
• manage bleeding – some alginates are licensed as haemostats
• autolytic debridement

Precautions:

• dry necrotic wounds – the absence of exudate prevents the fibres from gelling and creating an optimal wound healing environment
• friable tumours – may cause bleeding at the time of dressing change
• maceration – skin

The most popular topical applications are those that incorporate iodine, silver, honey and PHMB (polyhexamethylene biguanide). Passive mechanisms for sequestered or binding of bacteria also exist, such as DACC (dialkylcarbamoyl chloride) in combination with a variety of other base materials (eg Cutimed). PHMB is most commonly used in wound cleansing solutions.

Indications:

• wound cleansing
• reduction of bioburden within the wound margins
• breakdown and management of biofilms – minimising the redevelopment of a biofilm within the wound margins

Precautions:

• skin sensitivity
• adherence of base materials
• iodine-based products should be avoided in patients under 2 years, during pregnancy and lactation, and patients with thyroid disease

Made up of sterile elastic sheets of polyurethane, coated with a hypoallergenic acrylic adhesive on one side. Semi-permeable films are permeable to air and water vapour, but occlusive to fluids and bacteria. These dressings are generally not known for absorbency, but can manage small amounts of fluid if the film has an integrated central pad. The main difference between product types is the identified moisture-vapour transmission rate (MVTR), ability to act as a carrier (thin sheet of foam or a semi-permeable film) and their application. Films are highly flexible and transparent materials, which can be used as both primary and secondary dressings.

Indications:

• protection
• surgical wound sites
• minor trauma and burns – reported to minimise pain on donor sites

Precautions:

• exuding wounds
• dressing securement – ensure the film will not affect the MVTR of the dressing underneath

A primary dressing, made of polyurethane in a variety of forms, including simple foam sheets, film-backed foam sheets, polyurethane foam gels (hydro polymer) and cavity fillers (tube dressings) with different adhesives applied for dressing securement. One variety of foam has additional additives (eg glycerine and a surfactant).

Indications:

• low to moderate exudate production
• can be used as secondary dressing in conjunction with other materials

Precautions:

• dry wounds – foams are designed to absorb exudate
• erythematous reactions – thought to be a sensitised reaction to the polyurethane foam or an increased blood flow response, owing to improved thermal insulation of the wound being dressed
• lateral wicking of exudate across the foam cells – reaction is caused by peri-wound skin contact with the caustic components (proteases) within wound exudate
• maceration – skin damaged at a cellular level by the presence of moisture

Made up of a carrier (thin sheet of foam or a semi-permeable film) coated with an absorbent mass containing sodium carboxymethylcellulose and other gel-forming agents. These dressings are constructed using a cross-linked matrix, and are usually used in sheet form (thick or thin), but granules and pastes are also available. They are occasionally combined with other materials, such as alginates.

Indications:

• clean, granulating and/or sloughy or necrotic wounds
• very limited absorbency capacity – the amount of exudate that a hydrocolloid dressing can absorb will depend on the MVTR of the backing layer

Precautions:

• use with caution on infected wounds – Hess (2000) indicated that hydrocolloids should not be used on infected wounds, as the occlusive structure of the product may promote conditions that encourage the growth of anaerobic bacteria
• odour often associated with prolonged use (usually noted on removal) – from the collection of stagnant exudate between the dressing and

Traditionally, these dressings were made of an activated charcoal cloth integrated with padding material and a layer of hydrophobic (repelling water) material. An antimicrobial agent may also be added. Contemporary versions combine charcoal with an advanced wound dressing material, and function to improve the odour-absorbing properties, extending the potential clinical indications of these dressings.

Indications:

• discharging, infected and malodourous wounds

Precautions:

• not indicated for dry wounds

The functionality of the dressing varies depending on the type of product, for example, a starch-based matrix, fibrous type (with gel-blocking action), superabsorbent polymers or a mix of collagen and cellulose (form a gel when in contact with wound exudate).

Indications:

• chronic wound management

Precautions:

• starch-based versions should not be used on wounds requiring debridement
• generally not indicated for dry wounds

The use of dry and gauze impregnated dressings is not generally advocated, as they do not create an optimum wound healing environment and have been reported to cause pain and trauma during removal (Collier and Hollinworth, 2000). A new generation of low adherent dressings have been developed for minor wounds and grazes. They are generally composed of a silicone coating or soft silicone coating polymerised onto a viscose or polyamide fabric.

Indications:

• friable skin
• lightly exuding or granulating wounds

Precautions:

• sensitivity
• maceration – skin damaged at a cellular level by the presence of moisture
• skin stripping with traditional base materials coated with paraffin/iodine

If unsure which wound dressing to use, contact your tissue viability nurse/team, or the relevant manufacturers for clarification of the properties of the dressings available to you on your local guidelines or trust formulary. The recommended clinical indications and the evidence that supports the clinical use of the products must always be thoroughly checked before a particular wound dressing is used.

Collier M. The elements of wound assessment. Nurs Times. 2003;99(13):48-49.

Collier M, Hollinworth H. 2000. Pain and tissue trauma during dressing change. Nursing Standard 14(4) 71-73. https://doi.org/10.7748/ns2000.06.14.40.71.c2865 

Cowan T. Wound Care Handbook 2023-2024. 16th Ed. London: MA Healthcare; 2023.

Hess CT. When to use hydrocolloid dressings. Adv Skin Wound Care. 2000;13(2):63-64.