Technology and product reviews
of a calcium salt, fibres of calcium alginate are formed. This provides the foundation for alginate wound dressings[1-3]
. Alginate solutions will react with many divalent Page Points
1. Alginates are extracted from a variety of species of seaweeds.
2. Probably the major reason for selecting an alginate dressing is to manage wound exudate.
3. Alginate dressings are manufactured in a range of presentations from flat sheets to rope and ribbons.
or trivalent cations to form gels, with the nature of the gel strongly dependent upon the mix of M, G and MG groups in the alginate. Alginates that are high in M groups have a flat ribbon-like molecular appearance while areas high in G groups have a much more buckled chain shape. These differences in molecular appearance
affect gel formation, with high M alginates forming gels quicker, with a softer and more elastic gel than that produced by a G-rich alginate, which holds calcium and forms a gel slowly[3]
Allergies to any components of the dressing
Third degree burns. In addition, great caution should be taken when alginates are used in the dressing of tumours with friable tissue, which will have exposed blood vessels, as removal of the dressing may cause fresh bleeding.
TYPES OF DRESSING Alginate dressings are manufactured in a range of presentations from flat sheets to rope and ribbons[4]
. Flat sheets tend to be used for . G-rich alginates form gels slowly as the
buckled shape acts as an 'egg box' into which the calcium ions are packed[3]
. and held strongly
(chelated) by the structure of the tetrahydropyran ring of the α-L-guluronic acid monomer and the presence of hydroxyl oxygen atoms[1]
To accelerate gel formation, a mix of sodium
alginate and calcium alginate fibres are incorporated into an alginate dressing, with the sodium alginate added to accelerate the gelling process. Therefore, alginate dressings may vary both in their composition of calcium alginate and sodium alginate fibres, but also in the proportion of M and G groups present within each of the two alginate fibres.
References
4.MA Healthcare Ltd.Wound Care
Handbook 2011–2012. MA Healthcare Ltd, London.
5. Richards AJ, Hagelstein SM, Patel
GK, Ivins NM, Sweetland HM, Harding KG. Early use of negative pressure therapy in combination with silver
dressings in a difficult breast abscess. Int Wound J 2011; 8(6): 608–11.
6. Opanson S, Magnette A,
Meuleneire F, Harding K. Askina® Calgitrol® Made Easy.Wounds Int 2012; March 3(1).
7. Chrisman CA. Care of chronic
wounds in palliative care and end-of- life patients. Int Wound J 2010; 7(4): 214–35.
8. Sweeney IR, Miraftab M, Collyer G. A critical review of modern and emerging absorbent dressings used to treat exuding wounds.
Available at: http://onlinelibrary.
wiley.com/doi/10.1111/j.1742- 481X.2011.00923.x/abstract (accessed 8 May, 2012).
INDICATIONS AND CONTRAINDICATIONS Alginate dressings have three main characteristics that influence their indications for use. These are their ability to: Provide a moist environment at the wound bed
Absorb exudate Achieve haemostasis[5]
. In addition, they are able to reduce wound pain,
lower the bio-burden of the wound, reduce odour and absorb proteinases[6-8]
. If there is prolonged or
atypical inflammation then the wound produces abnormally high levels of proteinases, which have a detrimental effect on cell proliferation and growth factor production. Therefore, absorption of the proteinases into the wound dressing potentially lowers the elevated proteinase level and its detrimental impact on the healing process.
There are some contraindications for the use
of alginate dressings including: Dry wounds Wounds with minimal exudate Surgical implantations
26 Wounds International Vol 3 | Issue 2 | ©Wounds International 2012
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[4]
.
In addition, there are super absorbent and self-adhesive versions of alginate dressings[4]
.
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.
WHY SELECT AN ALGINATE? The major reason for selecting an alginate dressing is to manage wound exudate as it is claimed that they can absorb 15–20 times their own weight in wound fluid[4]
. Given this
capacity, it would appear prudent to use a second absorbent dressing, such as a pad or foam dressing as the secondary dressing when alginates are used. Although alginates can absorb much of the exudate produced by a heavily exuding wound, some wounds may exceed the dressing’s capacity for fluid uptake. Therefore, a secondary absorbent dressing can be used to contain any excess exudate. However, semi-permeable films have also been used as secondary dressings. A film dressing might be used for a wound exuding less fluid, which would not require an additional (and more expensive) foam dressing. When an alginate dressing comes into
contact with wound exudate there is an ion exchange between the calcium ions in the alginate and the sodium ions in blood or exudate. When sufficient calcium ions are replaced by sodium ions, the alginate fibres swell, partially dissolve and form a gel. The chemical composition of the alginate dressing also impacts on the dressing's ease of
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