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What are alginate dressings?
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An alginate dressing is a natural wound dressing derived from different types of algae and seaweeds. Highly absorbent and biodegradable alginate dressings have been successfully applied to cleanse a wide variety of secreting lesions.
The high absorption is achieved via strong hydrophilic gel formation. This limits wound secretions and minimizes bacterial contamination. Alginate fibres trapped in a wound are readily biodegraded. Alginate dressings maintain a physiologically moist microenvironment that promotes healing and the formation of granulation tissue.
Alginates can be rinsed away with saline irrigation, so removal of the dressing does not interfere with healing granulation tissue. This makes dressing changes virtually painless. Alginate dressings are very useful for moderate to heavily exudating wounds.
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How do alginate dressings work?
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Alginate dressings are dry until they come into contact with the wound, whereupon they 'up-take' fluid into the space between their fibres, and into the fibres themselves. This can help to absorb significant amounts of exudate. Once they have formed into a gel, alginates can also aid healing through promoting the growth of fresh epidermis.
The gel that is formed by an alginate dressing helps to stop the wound from drying out and aids debridement. Not all alginates are the same: the amount of fluid absorbed varies from product to product.
Alginate dressings are often used for burns, since they are very easy to remove when they need to be changed. This dressing is also commonly used with ulcers, including diabetic skin ulcers which can be very difficult to treat with other types of dressings.
They literally rinse of the skin's surface with a saline application or rinse or simply slough off with the gel and tissue when the wound is cleaned. Unlike other dressings, the key to successfully using calcium alginate dressings is to keep them off of the healthy tissue and just applied to the wound area. You would then use gauze and medical tape to hold in place.
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What are the main indications for alginate dressings?
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Alginates have been shown to be useful in a variety of situation; sloughy wounds which also produce a degree of exudate may be dressed with alginate dressings such as Sorbsan, Tegagen, Kaltostat (or other gel forming polysaccharide dressings).
The gel which is formed as these products absorb exudate forms a moist covering over the slough preventing it from drying out. These dressings require moisture to function correctly, so alginates are not indicated for dry sloughy wounds or those covered with hard necrotic tissue.
For shallow, heavily exuding wounds such as leg ulcers, fibrous sheet dressings made from alginate fibre may be used, while cavity wounds, traditionally packed with gauze soaked in saline, hypochlorite, or proflavine, are now more commonly dressed with alginate fibre in the form of ribbon or rope.
For epithelizing wounds, alginates have an advantage over cellulose dressings in that they can be removed without causing pain or trauma if they are first well soaked with sodium chloride solution.
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Are there any side effects of alginate dressings?
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Few studies mention side effects; certainly alginate use is characterised by convenience in application and removal, as confirmed by descriptive studies.
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Is there any difference between alginate dressing brands?
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Yes. A study compared four different calcium alginate dressings (Algosteril, Comfeel Alginate, Kaltostat and Sorbsan) with respect to wound fluid retaining ability, adherence, dressing residues, epithelialisation and inflammatory cell infiltration using a standardised partial-thickness wound model in domestic pigs.
Wound fluid spread laterally onto surrounding normal skin by about 40% more with Sorbsan than with the other alginate dressings after 24h (P = 0.026).
The corresponding figure after 66h was 20% (P = 0.030). Algosteril (mean 1.7 [sem 0.3]) adhered significantly (P = 0.014) more to the wounds than Comfeel Alginate (mean 0.2 [0.2]). Kaltostat (mean 1.8 [0.3]) left significantly (P = 0.038) more dressing residues on the wound surface at dressing removal than the Comfeel Alginate dressing (mean 0.8 [0.2]).
In the effect on epithelialisation or dermal inflammation there was no statistically significant difference at significance level 5% among the four alginate dressings, as assessed by light microscopy. In summary, the four alginate dressings showed significant differences in important handling characteristics but did not differ significantly in their effect on epithelialisation.
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Is alginate an effective haemostat?
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The value of alginates in this area has been challenged; a prospective, randomised clinical trial to compare the effectiveness of calcium alginate swabs versus traditional cotton swabs in the control of blood loss after extraction of deciduous teeth included 101 healthy children, aged 3-5 years.
Teeth were extracted under general anaesthesia and blood collected for measurement in order to compare blood loss using the two systems. The number of teeth extracted ranged from 1-14; total blood loss ranged from 0.53-78.13 ml with a median of 12.9 ml. Calcium alginate swabs, used in 51 subjects, were not found to produce any clinical or statistical advantage over traditional cotton swabs.
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Does zinc make a difference to haemostatic performance?
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Alginates act as calcium ion (Ca) donors as they contain mannuronic (M) or guluronic (G) groups with a high Ca content. A study compared the effects of calcium and zinc containing alginates and non-alginate dressings on blood coagulation and platelet activation to determine which was the best haemostat.
The study showed that alginate materials activated coagulation more than non-alginate materials. The extent of coagulation activation was affected differently by the alginate M or G group composition. It was demonstrated that alginates containing zinc ions had the greatest potentiating effect on prothrombotic coagulation and platelet activation.
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Can alginates reduce post-operative donor site pain?
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A prospective double blind controlled trial examined the differences in post-operative split skin graft donor site pain between sites dressed with three differently treated types of dressing; a dry calcium alginate dressing, a saline moistened calcium alginate dressing and a bupivacaine hydrochloride (0.5%) moistened calcium alginate dressing.
There was a significant reduction in post-operative pain in the calcium alginate and bupivacaine group (group 3) at 24 and 48h when compared to the other two groups (p < 0.04). There was no difference in ease of removal of dressings or the quality of wound healing on day 10 between the three groups.
This study suggested a significant reduction in post-operative pain in bupivacaine soaked calcium alginate, without reducing the beneficial effects of the calcium alginate on donor site healing.
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Are alginates effective with full-thickness pressure ulcers?
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A prospective, randomised, controlled trial of 92 patients with full-thickness pressure ulcers set out to compare the efficacy of an alginate wound dressing with an established local treatment with dextranomer paste.
During treatment, a minimal 40% reduction in wound area was obtained in 74% of the patients in the alginate group and in 42% of those in the dextranomer group. The median time taken to achieve this goal was four weeks with alginate and more than eight weeks in the control group. Mean surface area reduction per week was 2.39 cm2 (sd 3.54) and 0.27 cm2 (sd 3.21) in the alginate and dextranomer groups respectively (p = 0.0001).
This difference was still highly significant when the sub-groups of almost completely healed subjects at the end of the study were considered. This striking healing efficacy of an alginate dressing suggests it possesses pharmacological properties which require further investigation.
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How useful are alginates for packing deep wounds?
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A controlled trial set out to compare calcium alginate with the more traditional saline-soaked gauze for packing abscess cavities, following incision and drainage. Patients were randomized to receive either calcium alginate (16 patients) or gauze dressing (18 patients). At the first dressing change the patient marked on a linear analogue scale the pain experienced; the nurse noted similarly the ease of removal of the dressing.
Calcium alginate was significantly less painful to remove after operation (P less than 0.01), and also easier to remove (P less than 0.01) than gauze dressings. If abscess cavities are packed after incision and drainage, calcium alginate appears to be an improvement on conventional dressings.
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Does alginate packing affect scan results?
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A study examined the CT and MR appearances of four packing materials commonly used in otolaryngologic surgery. Bismuth and iodoform paraffin paste, aqueous betadine gauze, calcium sodium alginate, and triadocortyl cream were examined.
CT attenuation values were measured using phantoms containing packing materials; MR characteristics were examined by packing the external auditory meati of volunteers. Two illustrative case reports also are presented. Bismuth and iodoform paraffin paste has a high CT attenuation (> 3000 Hounsfield units) resulting in severe image degradation attributable to streak artifact. Aqueous betadine gauze was of high attenuation (258 Hounsfield units; SD, 16.5) but did not cause image degradation.
The attenuation value of calcium sodium alginate coincided with that of muscle, and the attenuation value of triadocortyl creme coincided with that of fat. On MR, calcium sodium alginate and bismuth and iodoform paraffin paste had imaging characteristics similar to muscle and aqueous betadine gauze had appearances similar to bone marrow.
Triadocortyl cream had a high signal equal to that of fat on T1-weighted images but a lower signal similar to bone marrow on T2-weighted images. The authors concluded that the presence of bismuth and iodoform paraffin paste can give rise to clinically important image degradation on CT. More seriously, residual packing material - including alginate - may be misinterpreted as infection or tissue necrosis.
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What is the role of alginates in foot care?
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Alginate dressings have been employed in footcare for many years, for sinus drainage and in the treatment of fissures, hypergranulation tissue, interdigital maceration, heloma molle and other lesions. Alginates have been used effectively in the treatment of diabetic and trophic foot ulcers.
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What are the various forms of alginate dressings available in the market?
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Alginate dressings are manufactured in a range of presentations from flat sheets to rope and ribbons. Flat sheets tend to be used for superficial wounds with the rope and ribbon versions used to lightly pack cavity wounds. Probes are included in some alginate dressing packs to help with packing cavities.
However, packing cavities is not recommended if the opening of the wound is smaller than the width of the probe. In addition, there are super absorbent and self-adhesive versions of alginate dressings.
If the alginate dressing is not self-adhesive the use of a secondary dressing will be required and selection of this secondary dressing may affect the performance of the alginate dressing.
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