Technology update Rediscovering alginate dressings


removal from the wound. G-rich alginates will only swell slightly during use and can be removed as an intact dressing, while dressings high in M alginates will swell to a greater extent and dissolve, allowing them to be removed through irrigation. Alginates can be used in a variety of wound


types where exudate is present, including:  Pressure ulcers  Venous leg ulcers  Diabetic foot ulcers  Post-operative wounds  Cavity wounds  Traumatic wounds  Malignant wounds  Pilonidal sinus wounds  Donor sites  Partial thickness burns [6-12]


. Generally, alginate dressings can be left


in place for 5–7 days. However, the dressing should be changed when it has reached its capacity for absorbing wound exudate. This is normally indicated by ‘strike through’ of fluid to the secondary dressing. In the case of infected wounds, daily inspection of the wound bed may be required. If the saturated alginate overlaps onto


the periwound skin it can cause maceration, therefore, clinicians should cut the alginate to the shape of the wound and apply a periwound skin protectant (such as a no-sting barrier film). Some alginate manufacturers recommend placing the dressing over the wound and the periwound skin with no requirement to cut the dressing to shape[5]


it should be removed once haemostasis has been achieved, otherwise the blood-soaked dressing will dry out and adhere to the wound bed making removal difficult and potentially painful for the patient. Alginate dressings are not recommended as a treatment for wounds that are bleeding heavily. These require alternative methods to achieve haemostasis, such as diathermy and cautery.


SILVER IN ALGINATE DRESSINGS Alginate dressings have been combined with other materials, for example, carboxymethylcellulose, zinc and silver[4]


. There


has been considerable interest in combining silver and alginate dressings since the addition of silver results in increased antimicrobial activity when tested in laboratory conditions[14-16]


. This


would suggest that the alginate dressings containing silver may be suitable for infected wounds. However, they should be used according to general best practice guidance for antimicrobial dressings[17]


, which states that for


the majority of patients, the initial prescription should normally be for 14 days with a formal review of treatment objectives at around seven days. A review should be conducted at each dressing change by a qualified clinician, and no prescription should extend beyond 14 days without discussion with a local specialist unless previously agreed or indicated by clinical need.


— if


in doubt, the clinician should always follow the manufacturer's instructions. As the volume of exudate reduces there is always the potential for the alginate to adhere to the wound bed if not saturated with wound fluid. In these situations the alginate should be moistened prior to removal and an alternative dressing used to achieve moisture balance at the wound bed.


FLUID-HANDLING PROPERTIES Absorbency should be reported as fluid uptake per standard dressing area (100cm2


) rather


than by dressing weight, given that dressings are supplied in a standard size rather than by their weight[13]


of alginate dressings may range[1] grams/100cm2


. On this basis, the absorbency from 16.16 with


to 24.7 grams/100cm2


absorbency also reduced where compression bandages are used[1]


(compressed dressings


have less capacity for fluid uptake, probably due to changes in their physical shape). If the alginate is used to control bleeding


RELEVANT LITERATURE Thomas[1]


provides an excellent review of


the use of alginate dressings (along with a wide range of other dressing materials) and this source should be considered as a basic introduction to the use and evaluation of wound dressings. The commercial production and basic


chemistry of alginic acid and the alginates has also been discussed in depth by McHugh [3]


, while


two recent Cochrane reviews detailed the role of alginate dressings in the treatment of diabetic foot ulcers [18–19]


. Given the paucity of randomised


controlled trials that have compared alginates (and other wound dressings), neither review was able to reach a definitive conclusion regarding the value of alginate dressings in diabetic foot ulcer care, with one stating that: 'Currently, there is no research evidence to suggest that alginate wound dressings are more effective in healing foot ulcers in people with diabetes than other types of dressing, however, many trials in this field are very small.'


References


9. Clark R, Bradbury S. Silvercel Non-Adherent Made Easy.Wounds Int 2010; 1(5): 1–6.


10. Harris CL, Holloway S. Development of an evidence- based protocol for care of pilonidal sinus wounds healing by secondary intent using a modified Reactive Delphi procedure. Part 2: methodology, analysis and results. Int Wound J 2012; 9(2): 173–188.


11. Higgins L, Wasiak J, Spinks A, Cleland H. Split-thickness skin graft donor site management: a randomized controlled trial comparing polyurethane with calcium alginate dressings. Int Wound J 2012; 9(2):126–131.


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