Evaluation of Two Calcium Alginate Dressings in the Management of Venous Ulcers

Index: 
Ostomy Wound Manage. 2003;49(9):26-33.
Marketa Limova, MD

   Chronic wounds are a significant problem worldwide, resulting in substantial morbidity and cost to healthcare systems. Chronic venous insufficiency affects approximately 5% of the adult population in developed countries, and the prevalence of chronic ulcerations is believed to be 1% in the world population.1-3

Even in situations with "good wound care," typical patients with venous ulcers may require 12 to 24 weeks to heal.3,4 In a study of 260 patients with venous ulcers treated with multilayer compression bandages, 32% did not achieve complete wound closure after 24 weeks of care and had a mean wound duration of 62.4 weeks.3

   Using occlusive dressings to cover chronic wounds and maintaining a moist wound environment facilitate healing far better than the traditional approach of a simple covering material and medicated ointment. Different types of moisture-retentive dressings have been developed and can be grouped into several categories based upon their chemical properties.5 Gel-forming dressings such as calcium alginates, which absorb the wound exudate to form a non-adherent gel, have been shown to accelerate wound healing in a moist environment,6 facilitate debridement, and help prevent trauma to the wound bed and periwound skin. The use of calcium alginate dressings has been evaluated in many clinical situations, including split-thickness skin graft donor sites,7-11 diabetic foot ulcers,12-14 pressure ulcers,15-17 and venous insufficiency ulcers.18-20 Because alginate dressings show significant differences in important handling characteristics,21 the performance characteristics of various calcium alginate dressings provide additional information upon which to base treatment decisions.

Methods

   The purpose of this open, randomized, controlled clinical study was to compare the performance characteristics and clinical effect of two calcium alginate dressings in the management of venous ulcers: 3M Tegagen™ HG (High Gelling) Alginate Dressing (3M Health Care, St. Paul, Minn.) - Alginate A - and Sorbsan™ Topical Wound Dressing (Dow Hickam Pharmaceuticals Inc., Sugar Land, Tex.) - Alginate B. The secondary dressing and compression therapy were the same for both treatment groups: 3M Tegasorb™ Hydrocolloid Dressing (3M Health Care, St. Paul, Minn.); Medicopaste® Bandage (Graham-Field, Bay City, NY); and 3M Coban™ Self-Adherent Wrap (3M Health Care, St. Paul, Minn.). Two clinical sites (University of California, San Francisco, and Minarets Medical Group, Inc., Fresno, Calif.) enrolled all eligible outpatients attending wound clinics and willing to participate in this study. All patient-related visits occurred between September 1997 and April 1999. Patients provided informed consent and were randomized to one of the treatment groups according to the protocol randomization schedule. Dressing changes, wound assessments, and dressing performance evaluations were completed weekly. Patients were followed for a maximum of 6 weeks or until the venous ulcer no longer required the use of a calcium alginate dressing.

   Inclusion criteria. To participate in this study, patients had to be greater than or equal to 21 years of age, able to understand and undergo the product application and assessment procedures required, and willing to sign an informed consent form before enrollment. The patient had to have a venous insufficiency ulcer of at least 1 month's duration, with an area ranging from 3.0 cm2 to 100 cm2, and with a moderate (3 cc to 5 cc) to large (>5 cc) amount of exudate.

   Exclusion criteria. Patients were excluded if they had an ankle brachial index (ABI) <0.8, uncontrolled diabetes, underlying vasculitis, were on immunosuppressive therapy, or if the ulcer showed signs of infection. Patients with preexisting local skin disease or conditions that could affect study results or who were allergic to materials used in the study also were excluded.

   Initial assessment. The initial study visit included measurement and photodocumentation of the wound area, collection of ulcer history, and determination of ulcer status (stable, improving, or worsening). Wound assessments included: amount of exudate estimated by observation of the wound/dressing upon dressing removal (dry; small - 1 cc to 2 cc; medium - 3 cc to 5 cc; large - >5 cc), the presence of odor (none, mild, foul), color of exudate (serous, serosanguineous, purulent), and need for debridement (ie, surgical debridement not requiring anesthesia) of fibrin or necrotic tissue. The condition of the wound edges (0 = indistinct, diffuse; 1 = attached; 2 = not attached; 3 = rolled under, thickened; 4 = hyperkeratosis; 5 = fibrotic, scarred) and periwound skin (normal, denuded, macerated, flaky/dry) were assessed. If the periwound skin was denuded or macerated, 3M™ Cavilon™ No Sting Barrier Film (3M Health Care, St. Paul, Minn.) was applied to the affected area. The type and amount of necrotic tissue (0 = none, 1 = less than or equal to25%, 2 = 26% to 50%, 3 = 51% to 75%, 4 = 76% to 99%, 5 = 100%) were noted, as well as the amount of granular tissue and epithelialization (0 = 100%, 1 = 76% to 99%, 2 = 51% to 75%, 3 = 26% to 50%, 4 = less than or equal to 25%, 5 = none). The amount of edema was not assessed.

   Weekly assessments. At each weekly visit, the wound assessment included a wound tracing and a photograph. Dressing performance assessments were rated on a scale of 1 (very good) to 5 (very poor) and included exudate absorption, comfort during wear, ease of removal, comfort during removal, ease of application, and conformability to site. Dressing adherence to wound bed (yes or no) and residue following initial irrigation (percent of area covered: 1 = none, 2 = less than or equal to 25%, 3 = 26% to 50%, 4 = 51% to 75%, 5 = >75%) also were documented.

   Comfort during wear and removal were assessed by asking patients how the dressing felt and if they experienced itching, pain, or other problems. All wound assessments and dressing performance evaluations were completed by either the primary investigator or her designate (RN staff member). Both evaluators were trained by the company sponsor regarding study protocol and completing case report forms.

   Data analysis. Descriptive statistics were calculated for all variables. For continuous variables and for ordinal variables having five or more levels, differences between groups at baseline were assessed using Student's t-test. Chi-square test was used for nominal variables, and the nonparametric equivalent to the t-test (Mann Whitney U test) was used for ordinal variables with fewer than five categories. Significance was assessed at P <0.05.

   Weekly assessments for dressing performance and wound status were summarized across visits and adjusted for the number of visits before analysis. For example, the percentage of visits in which the wound had a foul odor was calculated for each patient. These percentages were averaged across patients, and the difference between the groups was assessed using the t-test. If the variable of interest was ordinal with five or more levels, the mean score across visits was calculated for each patient and differences between groups were assessed using the t-test. Change from baseline was calculated for percent epithelialization, granulation tissue, condition of the wound edges, and amount of necrotic tissue. The t-test was used to assess differences in change from baseline between the dressing groups. Significance was assessed at P <0.05.

Results

   Initially, 20 patients were enrolled in the study. One patient in the Alginate A group left the study after 1 week of treatment due to an unrelated adverse event and was not included in the analyses. Of the 19 patients completing the study, 10 were treated with Alginate A and 9 were treated with Alginate B. No significant differences between the two treatment groups with respect to patient age, gender, height, or weight (see Table 1) were observed. The two groups were also similar with respect to ulcer history and initial presentation.

  The mean initial wound areas for Alginate A and B groups were 6.9 cm2 and 8.5 cm2, respectively (see Table 2). Debridement (surgical not requiring anesthesia) at enrollment was needed in 70% of the wounds in the Alginate A group, compared to 33.3% of the wounds in the Alginate B group. All wounds exhibited medium to large amounts of exudate with necrotic tissue present. Purulent or serosanguineous exudate was present in 30% of the wounds in the Alginate A group, compared to 66.7% of the wounds in the Alginate B group. More foul odor was noted in the Alginate B group than in the Alginate A group (22.2% versus 10.0%). Approximately half of the patients in both treatment groups had macerated periwound skin. None of the initial wound assessments demonstrated statistically significant differences between the two groups.

   The mean numbers of days in study for Alginate A and Alginate B patients was 38.1 days (range 21 to 42 days) and 39.2 days (range 28 to 42 days), respectively. Weekly wound assessments were summarized across all visits (see Table 3). The presence of foul odor was less frequent in the Alginate A group (15.7%) than in the Alginate B group (58.5%), a statistically significant difference (P <0.02). The Alginate A group also had significantly less denuded periwound skin (9.0%) than the Alginate B group (31.9%) (P <0.04). Medication was applied to the periwound skin less often in the Alginate A group (31.3%) than the Alginate B group (65.2%), but this difference was not significant (P <0.07). In general, the Alginate B wound group required more weekly debridement. In this group, more wounds with medium to large amounts of exudate, purulent or serosanguineous drainage, necrotic tissue, or macerated periwound skin were observed but the differences were not statistically significant. Wound assessment results indicate no significant differences with respect to mean improvement in wound condition score from baseline for the condition of the wound edges, granular tissue, epithelialization, or necrotic tissue.

   By the end of the study, the average wound size decrease was 33.7% in the Alginate A group and 29.6% in the Alginate B group. Patients in the Alginate A group had 65 scheduled dressing changes and 4 unscheduled dressing changes. Patients in the Alginate B group had 60 scheduled dressing changes and one unscheduled dressing change. None of the Alginate A patients achieved complete wound closure (100% epithelialization) during the 6-week study, compared to two patients (22%) in the Alginate B group.

  For dressing assessment and performance, Alginate A dressings were rated significantly better than Alginate B dressings in absorbency, comfort, ease of removal, comfort during removal, ease of application, and dressing residue following irrigation (see Table 4). In addition, the average percent of dressing changes with adherence to wound bed also was significantly less in the Alginate A group (P <0.05). No patients in the Alginate A group noted dressing adherence to the wound bed, compared to 27.8% of patients in the Alginate B group.

Discussion

   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. Because the material can hold up to 20 times its weight in fluid, it is suited for moderate to heavily exudating wounds such as venous insufficiency ulcers.

   This open, randomized, comparative evaluation showed that dressing performance of Alginate A was significantly better than Alginate B in terms of exudate absorption, comfort during wear, ease of removal, comfort during removal, ease of application, (no) adherence to wound bed, and (lack of) residue following irrigation. The presence of foul odor and denuded skin were both less frequent in the Alginate A group than in the Alginate B group. No significant differences in rate of healing were noted between the two groups, although fewer wounds in the Alginate A group required debridement. Due to the small sample size, significant differences in healing could not be observed. Nevertheless, if a dressing is more convenient or requires less debridement of the wound, it will ultimately be less costly to the healthcare system. Also, if the dressing is more comfortable to wear, is better able to hold exudate, and has less foul odor, it will encourage patients and family to be more compliant with the overall treatment plan.

Conclusion

   In this small, randomized, controlled, open label study, Alginate A demonstrated better overall dressing performance characteristics and comfort. Larger clinical trials are needed to evaluate the effect of different dressings on their rate of healing as well as their impact on the overall cost of therapy.

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