Alginate Dressings: A Gentle Touch

Alginates have proved themselves to be the ideal dressing for medium to high exuding wounds over the past thirty years; the literature demonstrates their value as a gentle, almost pain free primary dressing for a range of indications from donor sites to cavity wounds.

Introduction

Alginate dressings, originally derived from seaweed, have been used for many years for a variety of wounds. The substance was used as a haemostatic agent (Gilchrist and Martin 1983), particularly in dentistry, but no companies now hold product licenses for haemostasis.

Like many long established products, there are comparatively few large, well-randomized studies (Thomas 2000a,b,c). In recent years, while alginates have been used as controls for studies of newer materials, few researchers have explored the properties of alginates themselves.

Alginate dressings consist of naturally occurring polysaccharides that are derived from the cell walls of brown seaweed. They are manufactured as non-woven, fibrous sheets or rope-like packing. The dressings have been shown to be ideal for moderate to heavily exudating wounds (Limova 2003), though they do require a secondary dressing; such as a film if the wound is relatively dry, or an absorbent pad if there is heavy exudate.

In an exuding wound bed, alginate dressing fibres form part of the gel and do not have to be manually removed, provided the dressings are used, as recommended, for moderate to heavily exudating wounds (Limova 2003). This avoids the need to disturb granulating tissue, and makes the task of dressing removal easier for both professional and patient. (Gilchrist and Martin 1983). The dressings are manufactured to be easily prepared for the wound, either by cutting the square product or moulding the ‘rope’ preparations.

Few studies have compared different alginate dressings; one reported no significant differences in their effect on epithelialisation, but did identify handling differences, in a pig study of four brands (Agren 1996). A more recent study compared two brands, used for the treatment of leg ulcers, and also found minor differences (such as wound odour), but no significant differences in healing performance (Limova 2003).

Few studies have investigated the secondary dressings most appropriate for alginates. In all but those with very high exudate, it would seem logical to use an occlusive dressing, for infection control reasons, as with any exuding wound (Lawrence 1994), and there several factors to consider in the selection, such as convenience and ease of use for the professional; comfort and pain on removal for the patient; cost. In one small study, Beldon (2004) compared dressings on the basis of which provided the greatest comfort, had the fastest healing time and could be removed without trauma, and found that alginate with film cover was the superior choice – with the added benefit of being able to assess the need for dressing change without interfering with the existing dressing. However, there is little information on the ideal secondary dressing, so selection will depend on first principles.

Indications

Alginates are one of the dressings of choice for any moderate to highly exuding wounds, and studies have demonstrated their value in a variety of wound types:

1. Split skin graft donor sites

Alginates made their first big impression in wound care in the 1980s, as dressings for split skin graft donor sites; they rapidly showed that they were superior to paraffin gauze, the usual dressing for donor sites at that time. A study comparing the two dressings had to be abandoned by Attwood (1989), as there was consistently better healing under the alginates. These findings have been confirmed more recently by O'Donoghue et al (1997).

More recent studies suggest that newer materials, such as polyurethane foam dressings, may also have a role with these wounds; so far, however, there is not enough clinical evidence to conclude that such dressings should replace alginates (Vaingankar 2001), but there is a wider choice of dressings available.

Groves and Lawrence (1986) reported on the ability of alginate dressings to reduce blood loss from skin graft donor sites, with significant haemostasis being achieved in the immediate post operative period.

Dressing removal is also an issue with split skin graft donor sites; a study that compared calcium alginate and a silicone-coated polyamide net dressing found no significant difference in the pain associated with dressing changes. However, in the net dressing arm of the trial, absorbent gauze adhered to the donor site through the fenestrations in the dressing, and a layer of paraffin gauze had to be inserted between the experimental dressing and the cotton gauze, after the painful experiences of the first two patients (O'Donoghue et al 2000).

2. Burns

The dressing removal benefits found in donor site management may also apply in the management of burns too. Surgery can increase complications, both by increasing local bleeding, and adding the risk of skin grafts being removed with the dressing. Kneafsey et al (1996) report that the control of minor haemorrhage during excision and grafting following deep burns to the hand is difficult; while postoperative haematoma can reduce graft take. Using alginates during and after the operation was found to be of immense help in minimizing these problems.

3. Cavity Wounds

Alginate dressings are extremely absorbent, making them particularly useful for removal of moderate to large amounts of exudate (Motta 1989); this can make the dressings particularly useful for cavity wounds and infected surgical wounds.

A controlled trial comparing calcium alginate with the more traditional saline-soaked gauze for packing abscess cavities, following incision and drainage, found that the alginate packs were significantly easier to remove, with significantly less pain than the traditional pack (Dawson et al 1992).

Despite the introduction of newer, more absorbent dressings, alginate rope is still widely used in packing cavities. Sadly, the limited research in this area does not include any definitive comparisons between alginates and other materials; there is a need for such research to consider fluid handling properties, as well as ease of use and patient comfort on dressing application and removal.

There is little doubt that vacuum dressings are having a major impact on cavity wounds (Smith 2004), but there is still a need for research on cost-effectiveness, particularly with smaller cavity wounds, in order to reassess the role of more traditional dressings.

4. Pressure ulcers

High grade pressure ulcers often exude considerable amounts of fluid; one study set out to compare a sequential strategy - calcium alginate for four weeks, followed by hydrocolloid dressings - with treatment by hydrocolloids alone. Significantly faster healing was found in the sequential treatment group than in the control group (Belmin et al 2002).

When the efficacy of an alginate dressing was compared to that of an established protocol (using dextranomer paste in full-thickness pressure ulcers), a highly significant advantage was found in favour of the alginate; median time taken to achieve this healing was four weeks with alginate and more than eight weeks in the control group (Sayag et al 1996).

5. Diabetic foot lesions

Another study aimed at comparing both the efficacy and tolerance of an alginate wound dressing, with a paraffin gauze dressing, in the treatment of diabetic foot lesions, and found the alginate to be significantly better, in terms of healing (p=0.04), frequency of re-dressing (p=0.07), and in the pain associated with dressing changes (p=0.047) (Lalau et al 2002).

6. Leg Ulcers

Alginates may have a role in heavily exuding leg ulcers, but there is a dearth of helpful clinical studies. A key issue is the selection of appropriate secondary dressings, and this issue is highlighted by Schultze’s study (2001), which compared an alginate plus secondary dressing with a polyurethane foam dressing in managing leg ulcers. A longer wear time was observed in the polyurethane dressing group compared with the alginate group (p = 0.001), but the study did not find significant differences in healing, and did not investigate alternative secondary dressings.

Advantages of Alginates

Motta (1989) argued that alginate dressings were cost-effective because the frequency of dressing change was significantly reduced (compared to contemporary dressings).

Alginate dressings, used in moderate to heavily exuding wounds, maintain a moist environment at the wound, that promotes healing and the formation of granulation tissue, and as the dressing can be rinsed away with saline irrigation, removal of the dressing does not interfere with healing granulation either, a factor that makes dressing changes virtually painless (Motta 1989).

This major benefit has been tested and confirmed against several other dressings, even where no other clinical advantage is demonstrated (Bettinger et al 1995), and in a variety of different wound types, where the pain associated with dressing removal is a major issue, including haemorrhoidectomy (Ingram et al 1998).

Calcium alginates are effective haemostats in wound dressings (Steenfos and Agren 1998), acting as calcium ion donors with a potentiating effect on coagulation and platelet activation. The benefit does vary between products, with alginates containing zinc ions having a greater effect (Segal et al 1998). Neither of these studies considered arterial bleeding, in which alginates are contraindicated.

In comparisons with paraffin gauze, the quality of healing has been found to be significantly better when alginate dressings have been used (Attwood 1989, Basse et al 1992)

Limitations of Alginates

Barnett and Varley (1987) found that cellular reactions could be provoked in full thickness wound models without occlusion, where there was an insufficient volume of wound exudate to completely wet the alginate fibres. Similar findings have been reported in animal studies (Suzuki et al 1998), but clinical reports involving human subjects have proved impossible to find.

These experimental studies might have been rather different if the authors had used occlusion appropriately, and assessed each wound for its suitability for the dressing; alginates are best avoided unless there is sufficient exudate to form a gel which would almost entirely remove the risk of alginate fibres remaining in the wound bed.

A manufacturer’s in vitro study found that a hydrofibre dressing sequesters and retains micro-organisms upon exposure to simulated wound fluid significantly more effectively than an alginate (p < 0.05), and may help in reducing the microbial load in wounds. The clinical significance of this remains to be confirmed (Bowler 1999).

Odell et al (1994) reported a florid foreign body giant cell reaction elicited by an alginate used as a haemostat in a dental cavity, and not removed afterward. This further emphasizes the need to confine alginates to wounds where there is sufficient moisture to form a gel that can easily be flushed away with saline solution; and to remove excess alginate material from dry areas.

Bhalla et al (2002) reported a calcium alginate pack left in place to control bleeding following excision of the left submandibular gland. After an extended period of time, the pack excited a foreign body reaction, which appeared to be a recurrence of the tumour on, when seen on a computed tomogram.

Dressing Formulation

The Prescription Pricing Authority (2007) lists four varieties of alginate dressings:

1. Alginate dressing - For medium to heavily exuding wounds.

These dressings are not ideal for infected wounds, and should not be used on dry wounds, or those covered with dry necrotic tissue. They are manufactured in a variety of sizes, from 5cm x 5cm to 30cm x 61cm – these dressings are designed to lay flat on the wound bed, and should be trimmed to fit inside the area where exudate appears. If required, a double layer may be used, but in all cases a retention dressing is required, and an absorbent pad is an option. If the dressing is to remain in place days, then the user must decide if an occlusive dressing is required to maintain the moisture required for best effect and easy removal, or whether absorbent materials will be required to avoid strikethrough and leakage.

Current UK brands are ActivHeal, Algisite M, Algivon, Algosteril, Curasorb, Curasorb Plus, Curasorb Zn, Kaltostat, Melgisorb, Sorbalgon, Sorbsan, Suprasorb A, Tegagen, and Trionic.

2. Alginate Dressing with Absorbent Backing - For medium to heavily exuding wounds.

With similar uses as the standard dressing, absorbent padding is provided for ease of application. Sizes range from 7.5cm x 10cm to 19cm x 24cm (with a 15cm x 20cm contact area).

Current UK brands are Sorbsan Plus and Sorbsan Plus SA (with adhesive border).

3. Alginate Containing Hydrocolloid Dressing - For medium to heavily exuding wounds.

Sizes range from 5cm x 5cm to 10cm x 20cm.

Current UK brands are SeaSorb Soft, Urgosorb Pad

4. Capillary Action Absorbent Dressing

For low to heavily exuding wounds; these are not appropriate for very vascular wounds (e.g. fungating wounds), or where there is a risk of arterial bleeding (research showing haemostatic properties has focussed on .

Current UK brands are Acticoat Absorbent, ActivHeal, Algisite M-Rope, Algosteril Rope, Curasorb Rope, Curasorb Zn Rope, Curasorb Zn Rope, Kaltostat, Melgisorb Cavity, SeaSorb Soft Filler, Sorbalgon T, Sorbsan Packing, Sorbsan Ribbon, Suprasorb A, Tegagen, Trionic Rope, Urgosorb Rope,

The future of Alginates

Alginate dressings have been shown to be useful as carriers of therapeutic agents. As early as 1993, a comparison of dry alginate dressing, saline moistened alginate dressing and bupivacaine hydrochloride (0.5%) moistened alginate dressing in post-operative split skin graft donor sites, showed a significant reduction (p < 0.04) in post-operative pain in the bupivacaine-alginate group at 24 and 48 hours (Butler et al 1993).

A number of recent pilot studies have investigated using alginates to carry other active agents, but while these look promising, their value and place in wound care have yet to be confirmed.

Van der Weyden (2005) reported antibacterial, anti-inflammatory and deodorizing success, using a honey-impregnated alginate dressing. This was a case history of a man with challenging venous ulcers.

The value of silver as a topical anti-microbial agent is not in doubt, but the efficacy of specific silver-bearing wound products is remains controversial (Hermans 2006). Silver sulfadiazine-loaded alginate ‘microspheres’ may be able to deliver silver sulfadiazine in a controlled fashion, controlling infection for extended time period with reduced dressing frequency, while enabling easier assessment of the wound; laboratory studies are ongoing (Shanmugasundaram 2006). Silver-releasing dressings for wounds at high risk of infection may influence prognosis; however, the evaluation of these advantages is complex and methodology will need to be refined before proper evaluation can take place (Meaume 2005).

The Relevance of Alginates

With the huge number of new dressings made available in recent years, it is inevitable that others dressings will equal the benefits offered by alginates, and research increasingly uses alginate dressings as the control, rather than the experimental dressing (Armstrong and Ruckley 1997, Schultze 2001, Vaingankar 2001). Thus far, however, such trials suggest a need for further investigation rather than substantiate a claim for all-round superiority.

Thomas reviewed the literature on alginate dressings, and found that, despite their widespread use, alginates have featured in few properly controlled clinical studies (Thomas 2000a,b,c). He concluded that alginates do offer advantages over traditional dressings for some clinical indications and highlighted the lack of understanding about the importance of secondary dressing systems that must be used in with alginate dressings; the choice of both the primary alginate dressing and the secondary dressing can influence treatment outcomes.

It is a little sad to report, several years later, that no one has accepted the challenge to investigate the most appropriate secondary dressings. It would be useful to confirm that a vapour-permeable film dressing is best for low-exudate wounds, as first principles suggest, and still more useful to investigate the role of absorbent secondary dressings, in the context of the ideal frequency of dressing changes, and the implications for wound infection – and infection control.

Many dressings with similar indications to alginates have never been directly compared with them in properly controlled trials. As most modern dressings are much more expensive than alginates, even allowing for secondary dressings (Prescription Pricing Authority 2007), practitioners really need such information to make the best, most cost effective, choices.

This article is intended to remind clinical nurses of the potential usefulness of this versatile dressing; it has been around too long to get the fanfares associated with newer products, but it remains effective, and is almost unrivalled in its ability to make dressing changes a more gentle experience for the patient.

For the specialist, alginates remain a viable alternative to more complex and expensive products, and still have a place in the tissue viability armoury. Now, more than ever, practitioners need to examine all the options available for a particular situation; if the wound requires a dressing that is easy to handle, largely pain-free on removal, has haemostatic qualities and excellent fluid handling ability, then alginates still have no rival. But in the many cases where only one or two of these qualities are required, other dressings may be as good – then it becomes a matter of a cost effective solution. Few dressings can match alginates in a value for money comparison; still fewer can offer the gentle touch.

References

References have been deliberately excluded from this web publication, as - sadly - plagiarism and other academic theft has become such a problem, and I do not wish to facilitate that. However, The references can be made available for other needs. Please write with your request - and the rationale for it. I apologise for any inconvenence; but I know you understand.

Submitted: July 2007© Andrew Heenan