Alginate dressings still can be misunderstood
Understanding composition helps
Question: What are the main indications for alginate dressings, and what side effects are associated with them?
Answer: Alginate dressings are generally well-accepted by those who use them and are considered easy to use, convenient to apply and remove, and effective. However, despite this general acceptance, many clinicians still do not completely understand alginate dressings. Ironically, one reason may be that alginates have been used in one form or another for half a century. The literature, which tends to be weighted more heavily with testing and discussion of newer types of dressings, is sparse on the topic of alginates.
The potential benefits of alginate dressings can be better appreciated if you know something of their composition and function. Alginate dressings are derived from seaweed. The alginate fiber absorbs and interacts with fluid and turns into a hydrophilic gel.
Alginates tend to keep wounds moist and foster the formulation of granulation tissue. Upon removal, the dressing can be washed away with saline irrigation. This feature brings with it some important benefits: Dressing removal does not interfere with the formation of the granulation bed because it does not rip out healing or necrotic tissue, and dressing changes usually are pain-free. In laboratory studies, alginate dressings have been shown to enhance some wound healing processes at the cellular level while not others. For instance, alginates have been found in vitro to increase the proliferation of fibroblasts; however, they also appear to decrease the proliferation of keratinocytes and microvascular endothelial cells.4 Another desirable characteristic of alginates is that dressing fibers that get trapped in a wound biodegrade quickly.
Alginate dressings, because of their absorptive characteristics, are often applied to wounds that produce large amounts of exudate. Alginate dressings (such as Sorbsan, Kaltostat, and Tegagen) may gel to varying degrees in terms of the integrity of the gel, but function similarly. The gel forms a moist covering over the wound bed and keeps it from drying out. Without the presence of exudate from the wound, these dressings cannot function optimally. Therefore, alginates do not function well when applied to dry, sloughy wounds or those that are covered with hard necrotic tissue.1 The choice of secondary dressing to hold the alginate on the wound is also important in terms of maintaining the gel's moisture. As has been discussed previously in Wound Care, dressings can vary by brand, and this is certainly true with alginates. In one study comparing four alginate dressings (Algosteril, Comfeel Alginate, Kaltostat, and Sorbsan), researchers found that the dressings varied by certain characteristics, including fluid-retaining ability, adherence, and dressing residue. No difference was found in the dressings' effect on epithelialization.6
Many clinicians prefer alginates for dressing heavily exuding chronic wounds such as venous leg ulcers, diabetic ulcers, and pressure ulcers. Alginate dressings usually are available in two physical formats: a nonwoven sheet (good for shallow wounds) and a swatch of fibers or rope (good for packing wounds of depth). In one study investigating the use of alginates vs. dextranomer in treating full-thickness pressure ulcers, 74% of wounds treated with alginate reduced in size by at least 40% after four weeks. Only 42% of wounds treated with dextranomer reached a similar reduction after eight weeks. The study also suggested that alginates may have pharmacological properties that bear further investigation.5
Alginates also have been used successfully on acute wounds such as skin graft donor sites. In prospective controlled trials, alginates demonstrated the ability to improve the re-epithelialization of split-thickness skin graft donor sites compared to paraffin gauze. Twenty-one of 30 wounds dressed with alginate were completely healed after 10 days, as compared to only seven of 21 wounds dressed with paraffin gauze.2 Another study concluded that alginates were equivalent to scarlet red dressings in promoting epithelialization of skin graft sites. However, the patients treated with alginates reported less pain.3
Some clinicians prefer alginates for dressing shallow, heavily exuding wounds, such as leg ulcers. For these wounds, alginates in the form of sheet dressings are a logical choice. Sheet alginates sometimes are used effectively to treat diabetic foot wounds. When used to dress deep wounds, alginates in the form of a ribbon or rope are more effective than sheets.
As for side effects, few are associated with alginate dressings in chronic wound care. In the literature, foreign body reaction has been mentioned as one risk, but not in cases associated with chronic wound care. Still, irrigation of the wound following alginate use is recommended to remove any debris that might provide a source of infection.
References
1. Thomas S. A structured approach to the selection of dressings. World Wide Wounds 1997; http://www.smtl.co.uk/World-Wide-Wounds/1997/july/Thomas-Guide/Dress-Select.html.
2. O'Donoghue JM, O'Sullivan ST, Beausang ES, et al. Calcium alginate dressings promote healing of split skin graft donor sites. Acta Chir Plast 1997; 39:53-55.
3. Bettinger D, Gore D, Humphries Y. Evaluation of calcium alginate for skin graft donor sites. Burn Care Rehabil 1995; January:59-61.
4. Doyle JW, Roth TP, Smith RM, et al. Effects of calcium alginate on cellular wound healing processes modeled in vitro. J Biomed Mater Res 1996; 32:561-568.
5. Sayag J, Meaume S, Bohbot S. Healing properties of calcium alginate dressings. J Wound Care 1996; 5:357-362.
6. Agren MS. Four alginate dressings in the treatment of partial thickness wounds: A comparative experimental study. J Plast Surg 1996; 49:129-134.
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