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Topic Seven: Super Absorbent Dressings

The main function of these dressings is the absorption and containment of exudate. Dressings that can help to optimally manage wound exudate and promote a balanced environment are key to improving wound and patient outcomes.

Super absorbent polymers (SAPs) have been used since the 1980s and are commonly found in nappies, incontinence and feminine hygiene products. In recent years, there has been a considerable increase in the number of wound dressings that contain SAPs (Ousey, Atkin, & White, 2013).

Composition and Properties

Super absorptive dressings are multi-layered devices that provide either a semi-adherent quality or a non-adherent layer. They are made from a variety of materials, consisting of an inner absorbent core combined with a highly absorptive layer of fibres, such as cellulose, cotton or rayon. These dressings are designed to minimise adherence to the wound and manage exudate.

Super absorbent polymers are compounds that can absorb and retain large volumes of liquid relevant to their mass. Polymers are classified as non-ionic, without electrical charge (e.g. polyurethane foam dressings), or ionic polymers, with electrical charge. Non-ionic polymer chains are linked closely together or coiled and do not have much capacity for absorbing fluid. Dressings containing non-ionic polymers, such as polyurethane foams, are used for wounds with low volumes of exudate (White et al., 2012).

Ionic polymers have negatively charged side arms that repel the linking polymer chains away from each other. The repelling ions cause the ionic polymers to stay spread apart, thus creating more space in the polymer chain and allowing for extremely high absorption rates (Pytlik, Morino & Moritz, 2005).

Dressings containing ionic polymers with increased absorption capacity, such as calcium alginate dressings, are suitable for wounds with moderate to high levels of exudate (Walker & Parsons, 2010). However, these dressings can sometimes lose structural integrity and disintegrate due to the large volumes of liquid absorbed.

Super absorbent dressings were subsequently developed and are able to absorb more fluid, retain the fluid they absorb, and are associated with a reduced dressing change frequency (Gardner, 2012), which can result in lower costs. They have the ability to swell to many times their original size and weight, holding large volumes of fluid while maintaining their structure (Dhodapkar, Borde & Nandy, 2009).

However, the mere presence of SAPs does not guarantee optimal wound dressing performance. The fluid handling capacity of these dressings varies substantially, depending on the design and construction of the polymer, which may or may not be combined with other components to influence fluid handling (Cutting & Westgate, 2012).

Indications for use

SAPs are indicated for moderate to highly exuding wounds. They are designed to absorb and retain fluid and thus reduce the risk of leakage and maceration (Wiegand & White, 2013). Their substantial absorption capacity allows extended wear time, thus reducing the frequency of dressing changes and the number of times the wound is disturbed while protecting the surrounding skin (Stephen-Haynes, 2011).

Practitioners must manage the wound environment so that the moisture levels are optimal for healing. The challenge is to maintain optimum moisture in an ever-changing wound environment with minimum interference to the wound bed, i.e. the least number of dressing changes whilst removing exudate from the surrounding skin (Bale, 1997; Adderley, 2008).

As might be anticipated, the swelling of an absorbent dressing in a confined space (i.e. between the compression bandage and the wound) is likely to increase localised pressure. An alteration of sub-bandage pressure in this range of products deserves consideration as it may lead to detrimental effects on ulcer healing, patient comfort, and compliance with compression therapy (Cook, 2011).