Hydrogel Enriched With Sodium Alginate and Vitamins A and E for Diabetic Foot Ulcer: A Randomized Controlled Trial

Diabetic foot ulcers are full-thickness lesions that extend from the distal skin to the malleolus, and they are a significant complication of diabetes.¹ Up to 25% of patients with diabetes experience a DFU.² Diabetic neuropathy increases the risk of uncontrolled recurring lesions in the lower limbs and is a risk factor for foot and leg ulceration that may necessitate amputation.³ With an average healing time of 1 year, such ulcers are associated with poor clinical outcomes, increased morbidity and mortality, and worsening of quality of life.^4,5

Cutaneous traumas cause physiological cellular and tissue responses in the healing process; these include infiltration of inflammatory cells, epithelialization, granular tissue formation, extracellular matrix deposition, wound contraction, and tissue maturation. In diabetic wounds, this repair response cycle is altered, with inadequate secretion of extracellular matrix proteins and the deregulation of macrophage activity. Additionally, there is an increase in fibroblast apoptosis, impaired angiogenesis, and reepithelialization.⁶ Diabetes increases oxidative stress, causing chronic inflammation that damages cells that undergo senescence conversion, and as a result, become pro-inflammatory and perpetuate this phenotype in all tissues. Such cellular senescence may contribute to the chronification of ulcers, local ischemia, and an increase in bacterial load and necrotic tissue.⁷

Adequate WBP aids progression of the normal repair process in these situations.⁸ Debridement is essential to WBP and allows for the removal of necrotic tissue, thus reducing the number of microorganisms, toxins, and other substances that prevent healing.^9,10 The autolytic debridement method consists of keeping the wound wet so that the cells and endogenous enzymes remove the necrotic tissue. Hydrogels are a widely used type of autolytic debridement dressing. They consist of compounds of hydrophilic polymers inside an interdimensional matrix that can create a wet environment on the wound bed, thus facilitating endogenous enzymes in the autolysis of necrotic and apoptotic tissue.^11,12

A product that combines hydrogel with calcium alginate, oily acids, and vitamins A and E (Dersani Hidrogel; Laboratório Daudt Oliveira LTDA) is a new therapeutic option for treating a DFU. The hydrogel promotes autolytic debridement, and alginate stimulates new granulation tissue on the wound bed. Oily acids (capric acid triglycerides, lecithin, retinol palmitate, α-tocopherol) and vitamins A and E facilitate the reepithelialization process.¹³ In a recent case series, amorphous hydrogel enriched with oily acids and vitamins A and E was used to treat ulcers on the lower limbs of patients with diabetes. Of the 7 patients, 2 had achieved complete healing and 5 had experienced reductions in lesion area and PUSH score.¹⁴

Based on those promising results, the current clinical trial was designed to evaluate the efficacy of autolytic debridement promoted by hydrogel with sodium alginate enriched with oily acid and vitamins A and E to stimulate wound bed healing in DFUs. The microscopic effects of the hydrogel in promoting collagen production and reducing inflammatory infiltrates in the wound bed were qualitatively evaluated.

Study design

This was a single-blinded randomized controlled trial with a 12-week follow-up period. The main aim of the study was to assess the use of amorphous hydrogel enriched with oily acids and vitamins A and E in the treatment of DFU. The study was conducted in a specialty clinic that is considered a reference unit for the eastern region of São Paulo State, Brazil. The research was conducted over a 9-month period (April 2017 through December 2017). The study was performed according to the ethical requirements determined by Resolution no. 466, of December 12, 2012, of the Brazilian National Health Council and other regulations. The study was analyzed by the Ethics Committee in Research of the Santa Marcelina Hospital, São Paulo, Brazil with the consolidated report of approval no. 2.214.977, CAAE 65256817.0.0000.0066. Participation was voluntary, and none of the subjects received financial rewards as a result of their participation. The trial follows CONSORT.¹⁵
 

Participants

The inclusion criteria were patients aged 18 years or older with a medical diagnosis of type 2 diabetes, with at least 1 neuropathic wound larger than 1 cm² located on the dorsum or plantar region of the foot, with no clinical signs of infection (no cellulitis or purulent secretion) in the ulcer or periwound tissue, with pedis pulse, with a standard ankle-brachial index (0.9–1.30), with no sign of ischemia or indication of revascularization of lower limbs, with wound duration of at least 3 months before the study, with albumin above 3.5 mg/dL and hemoglobin A_1c less than 7%, and with no allergy to a hydrogel. Participants were required to adhere to the study procedures and freely sign an informed consent form. Exclusion criteria were as follows: corticosteroid dose greater than 5 mg daily, surgical debridement 3 days or fewer before the onset of the study, previous use of hydrogel, venous disease (venous ulcers), end-stage renal disease, HIV, pregnant or breastfeeding status, and participation in other studies evaluating dressings less than 30 days before recruitment for the current study.
 

Randomization

An open-source online software tool was used to perform the randomized distribution of participants into either a control group (group C) or an experimental group (group E) (http://www.randomization.com). The generator attributes treatments with randomized block sizes, while the user specifies only the number of individuals per block and the number of each type of block desired.
 

Masking

The researchers were blinded to patient history and follow-up care. The researcher in charge (a nurse) was responsible for preparing the participants for photographic evaluation by the 2 blinded researchers (a plastic surgeon and a wound enterostomal nurse). These researchers did not have access to any clinical or histological data for the participants, and they were not allowed to question participants about treatment follow-up.

The plastic surgeon performed the biopsy after wound cleansing to ensure that the researcher did not know the type of treatment and group to which the participant belonged.
 

Treatment protocol

Initially, 26 participants were included in the study, but only 19 reached study completion. The patients were randomly allocated into either group C or group E. All participants and their caretakers received instructions on how to change dressings per the randomized study group.

For group E, dressings were changed daily following the standard procedure of cleansing with 0.9% saline solution and application of amorphous hydrogel enriched with oily acids and vitamins A and E only in the area of the wound—thus avoiding contact with the surrounding skin—followed by placement of nonadherent cellulose acetate dressing and cotton gauze. For group C, wounds were cleansed with 0.9% saline solution, followed by application of nonadherent cellulose acetate dressing and cotton gauze. Dressings were changed daily, and all necessary material to perform dressing changes at home was provided at no extra cost to the participants.

Participants and caretakers agreed to follow the daily schedule for dressing changes. Every 4 weeks, the participants in both groups visited the outpatient unit for follow-up appointments and wound measurements. Treatment was continued for 12 weeks or until the wound was healed. All participants used therapeutic shoes explicitly designed for offloading.
 

Data collection and outcomes
measurement

At the initial assessment, the clinical history of each participant was obtained. In addition, the wound was photographed and the dimensions were measured using a planimeter to calculate the area of the lesion, the wound was classified using the Portuguese language version of the PUSH scale, biopsies of 3 mm from a central point of the wound bed were taken using the punch technique, and dressings were changed according to the protocol for the specific group (group C or group E). At 12-week follow-up, all participants were reevaluated; wounds were photographed, measured using a planimeter, and classified according to the PUSH scale; biopsy was performed; and dressing performance was evaluated.

Data on patient age, sex, previous diseases, comorbidities, life habits, duration of the open wound, and previous treatments were collected during the initial clinical evaluation. The photographic register was used to aid in calculating total wound area. At both the initial assessment and at 12-week follow-up, lesions were photographed using a digital camera (Coolpix L820; Nikon) at a median distance of 15 cm. A ruler was used for scale, but the ruler did not come in contact with the wound. The images were analyzed using the open-source software program Image J (version 1.36b; Wayne Rasband, National Institutes of Health, United States) (http://rsbweb.nih.gov/ij/index.html).

The PUSH instrument was initially created and validated by the PUSH Task Force of the National Pressure Ulcer Advisory Panel (now the National Pressure Injury Advisory Panel) for evaluating pressure ulcer healing.¹⁶ However, it was later validated for the evaluation of other types of wounds of diabetic origin¹⁷ and venous origin.^18,19 The PUSH tool uses 3 parameters in evaluating the wound healing process and intervention results: area of the wound, exudate amount, and type of wound tissue. These parameters are numerically classified as follows: area (0–10, with 0 being the smallest and 10 the largest wound size), exudate (none, 0; light, 1; moderate, 2; heavy, 3), and type of tissue (none, 0; epithelial, 1; granulation, 2; slough, 3; necrotic, 4). The higher the point tally, the more severe the wound. A wound enterostomal nurse and a plastic surgeon, neither of whom had contact with the participants, used the photographs to classify the wounds using the PUSH instrument.

Biopsied material removed from the wound bed was used for histological preparations and stained with hematoxylin and eosin and PSR. These biopsy specimens were used to evaluate the histological conditions of the wound bed in terms of changes in the inflammatory infiltrates and the deposition of new collagen fibers.
 

Statistical analysis

A descriptive analysis of the sample characteristics was carried out according to the study groups, showing the mean ± standard deviation and median (interquartile interval) for all variables evaluated at the onset of the study and at 12-week follow-up.

The Mann-Whitney nonparametric test was used to compare differences between the groups over the 12-week study period as well as between the groups at initial assessment and 12-week follow-up. The specific parameters studied included percent reduction in wound area, as well as changes in length × width, quantity of exudate, tissue type, and total PUSH score. Analyses were carried out with the aid of R software (version 3.4.1; The R Project for Statistical Computing).²⁰ For the hypothesis tests, a significance level of 5% was used.

A total of 35 individuals were selected for the current study, 9 of whom were ineligible for randomization. In total, 26 individuals were randomized into either group E (16 participants) or group C (10 participants). Four participants in group E were excluded from the study, 3 for missing appointments and 1 as a result of an adverse event that required the amputation of a limb owing to infection and sepsis. Two participants in group C were excluded from the study for missing appointments, and 1 was excluded as a result of an adverse event that required amputation owing to infection followed by sepsis. After these exclusions, 19 individuals were included in the analysis (Figure 1).

Due to the loss of participants, the authors had calculated the sample size power for all outcomes analyses (PUSH, wound area, exudate amount, and tissue type) using G*Power software (version 3.1.9.4; Apponic). Effect sizes below 0.80 were observed for 3 outcomes: wound area, amount of exudate, and tissue type, with estimated values of 0.49, 0.19, and 0.69, respectively. The sample power values for the relative difference in the outcomes of wound area, exudate amount, and tissue type were 0.99, 0.95, and 0.99, respectively. These results demonstrate that the sample size presents adequate statistical power to detect differences in these 3 outcomes.

The demographic and clinical characteristics of the sample (26 participants) are shown in Table 1. Comparison of the descriptive statistics of the evaluated variables at the initial assessment (26 participants) and at 12 weeks (19 participants) is shown in Table 2; values were calculated using the Mann-Whitney nonparametric test. No statistically significant differences were identified. The distribution of the wound area observed at the initial assessment and at 12-week follow-up by group is shown in Figure 2. Wound area was larger in group E at the initial assessment and remained so at 12-week follow-up.

Because of this visual difference in the initial instance, Table 3 proposes an evaluation of the differences for total areas in cm² and percentage of area reduction. No statistical significance for any variable was found. The box plot of the relative differences is shown in Figure 1C.

Figure 3 demonstrates the change in PUSH score over time. The κ statistic was used to calculate interobserver reliability, resulting in a value of 0.83. Both groups had PUSH score reduction after 12 weeks. eFigure 4 shows the change in wound area over time in a patient treated with enriched hydrogel.

Comparative images used in qualitative microscopic analysis of 2 patients—1 from group E and 1 from group C—are shown in eFigure 5. Inflammatory infiltrate was present at pretreatment in both groups; after 12 weeks, there was a reduction of the infiltrates in both groups. Polarization microscopy with PSR stain showed low or absent collagen production in both groups (eFigure 6).

Several new treatments have been developed to promote the wound healing process in diabetic ulcers. These include dressings that influence the wound microenvironment, allowing for the generation of conditions favorable to the tissue repair process. One such treatment alternative is a hydrogel enriched with alginate and vitamins A and E, composed of hydrophilic polymers that help remove nonviable tissues and create a moist environment, thereby allowing the body’s native enzymes to eliminate necrotic tissue.¹⁴

In the current clinical trial, the duration of treatment was 12 weeks, and the clinical and histologic aspects of the wound were evaluated. Of the 26 participants included, 2 required lower limb amputation owing to complications of local infection followed by sepsis. In a retrospective cohort study, 113 of the 192 participants who completed follow-up required amputation (58.9%).²¹ In that study, infection combined with bone or joint involvement was significantly associated with an increased risk of amputation (P =.035).

Homogeneity of clinical characteristics was demonstrated, with a mean age of 63.8 years in group E and 61.9 years in group C, and a mean long-term open ulcer duration of 586.6 days in group E and 687 days in group C. Aging is a systemic factor that may negatively affect the healing process.²² In the current study, the inclusion of only participants with normal albumin levels and hemoglobin A_1c was an attempt to avoid possible confounding factors, because malnutrition and hyperglycemia can negatively affect healing.

Patients in group E had larger lesions compared with patients in group C at the initial assessment. Although care was taken in the randomization and allocation of patients, this difference may have resulted in a bias in the results of this study, which may have negatively affected the evaluation of the results. It is known that the larger the initial area of a wound, the more difficult it is to achieve wound closure.²³

No significant difference between group C and group E was noted for any of the parameters studied (wound area, PUSH total score, PUSH subscores). Therefore, it was not possible to identify a positive effect of treatment with the hydrogel. The large difference between the initial median area of wounds between the groups may be the reason for this, because larger wounds have a lower chance of healing; thus, the PUSH result will be worse because the lesion dimensions are weighted heavily in the overall score.

Microscopic analysis revealed a decrease in inflammatory infiltrates in group E after 12 weeks of treatment. This is likely owing to the change in the wound bed by the action of the hydrogel, which promotes wound debridement. No significant increase in collagen production after hydrogel use was observed on quantitative analysis of the collagen fibers by PSR stain, however. This finding is consistent with the PUSH subscore for the type of wound tissue, which showed that the hydrogel treatment did not produce an apparent increase in granulation tissue. The increase in collagen production is essential for granulation tissue formation because the fibroblasts interact with this protein, causing wound contraction.²⁴

The authors of a systematic review conducted in 2013 indicated that hydrogel dressings were useful in the management of DFU compared with basic wound contact dressings, but the evidence was of lower quality owing to the large number of biases in the available studies.²⁵ Unfortunately, the current study could not be conclusive about the greater effectiveness of enriched hydrogel dressings to manage ulcers in patients with diabetes.

The difficulties and limitations of the current study may explain the limited results obtained. For example, the small sample size and the proportionately large number of patients lost from the study drastically affected the analysis of the outcomes, thus preventing the achievement of more robust results. Furthermore, the severe financial crisis in Brazil may be the reason a large number of participants dropped out of this study, because patients reported lacking the financial means to pay for follow-up laboratory studies and reported concerns about missing a day of work and the resulting risk of possible dismissal.

No evidence of benefit was found in this clinical study regarding the use of enriched hydrogel for the management of DFU compared with conventional dressings. Future studies with reduced patient absenteeism and increased sample size may offer more significant and robust results.