Synthetic wound dressings

Introduction

Synthetic wound dressings originally consisted of two types; gauze-based dressings and paste bandages such as zinc paste bandages. In the mid-1980s the first modern wound dressings were introduced which delivered important characteristics of an ideal wound dressing: moisture keeping and absorbing (e.g. polyurethane foams, hydrocolloids) and moisture keeping and antibacterial (e.g. iodine-containing gels).

During the mid 1990s, synthetic wound dressings expanded into the following groups of products:

• Vapour-permeable adhesive films
• Hydrogels
• Hydrocolloids
• Alginates
• Synthetic foam dressings
• Silicone meshes
• Tissue adhesives
• Barrier films
• Silver- or collagen-containing dressings.

Silver-containg dressing

Silver-containg dressing

Silver-containg dressing

Ideal wound dressing

No single dressing is suitable for all types of wounds. Often a number of different types of dressings will be used during the healing process of a single wound. Dressings should perform one or more of the following functions:

• Maintain a moist environment at the wound/dressing interface
• Absorb excess exudate without leakage to the surface of the dressing
• Provide thermal insulation and mechanical protection
• Provide bacterial protection
• Allow gaseous and fluid exchange
• Absorb wound odour
• Be non-adherent to the wound and easily removed without trauma
• Provide some debridement action (remove dead tissue and/or foreign particles)
• Be non-toxic, non-allergenic and non-sensitising (to both patient and medical staff)
• Sterile.

Classification of wound dressings

Synthetic wound dressings can be broadly categorized into the following types.

Wound types and dressings

The following table describes some of the many different types of wound dressings and their main properties.

Dressing type	Properties
Gauze	Dressings can stick to the wound surface and disrupt the wound bed when removed Only use on minor wounds or as secondary dressings
Tulle	Dressing does not stick to wound surface Suitable for flat, shallow wound Useful in patient with sensitive skin eg Jelonet®, Paranet®
Semipermeable film	Sterile sheet of polyurethane coated with acrylic adhesive Transparent allowing wound checks Suitable for shallow wound with low exudate eg OpSite®, Tegaderm®
Hydrocolloids	Composed of carboxymethylcellulose, gelatin, pectin, elastomers and adhesives that turn into a gel when exudate is absorbed. This creates a warm, moist environment that promotes debridement and healing Depending on the hydrocolloid dressing chosen can be used in wounds with light to heavy exudate, sloughing or granulating wounds Available in many forms (adhesive or non-adhesive pad, paste, powder) but most commonly as self-adhesive pads eg DuoDERM®, Tegasorb®
Hydrogels	Composed mainly of water in a complex network or fibres that keep the polymer gel intact. Water is released to keep the wound moist Used for necrotic or sloughy wound beds to rehydrate and remove dead tissue. Do not use for moderate to heavily exudating wounds eg Tegagel®, Intrasite®
Alginates	Composed of calcium alginate (a seaweed component). When in contact with wound, calcium in the dressing is exchanged with sodium from wound fluid and this turns dressing into a gel that maintains a moist wound environment Good for exudating wounds and helps in debridement of sloughing wounds Do not use on low exudating wounds as this will cause dryness and scabbing Dressing should be changed daily eg Kaltostat®, Sorbsan®
Polyurethane or silicone foams	Designed to absorb large amounts of exudates Maintain a moist wound environment but are not as useful as alginates or hydrocolloids for debridement Do not use on low exudating wounds as this will cause dryness and scabbing eg Allevyn®, Lyofoam®
Hydrofibre	Soft non-woven pad or ribbon dressing made from sodium carboxymethylcellulose fibres Interact with wound drainage to form a soft gel Absorb exudate and provide a moist environment in a deep wound that needs packing
Collagens	Dressings come in pads, gels or particles Promote the deposit of newly formed collagen in the wound bed Absorb exudate and provide a moist environment

Different types of wounds and the different stages of a healing wound require different dressings or combinations of dressings. The following table shows suitable dressings for particular wound types.

	Wound type	Dressing type
	Clean, medium-to-high exudate (epithelialising)	Paraffin gauze Knitted viscose primary dressing
	Clean, dry, low exudate (epithelialising)	Absorbent perforated plastic film-faced dressing Vapour-permeable adhesive film dressing
	Clean, exudating (granulating)	Hydrocolloids Foams Alginates
	Slough-covered	Hydrocolloids Hydrogels
	Dry, necrotic	Hydrocolloids Hydrogels

The dressings may require secondary dressings such as absorbent pad and bandages.

Adverse effects of dressings

Wound dressings can cause problems, including:

• Maceration (sogginess) of surrounding skin (change dressing frequently and use a more absorbent dressing)
• Irritant contact dermatitis (protect skin with emollient or barrier film)
• Allergic contact dermatitis (uncommon: change dressing type, apply topical steroids)