A pilot evaluation of a new multilayer wound dressing has confirmed its efficacy for transporting exudate containing toxic matrix metalloproteases (MMPs) away from chronic venous leg ulcers (VLUs). Conducted by Oscar M Alvarez (University Hospital; Rutgers New Jersey Medical School, Newark, USA) and Mark Granick (Rutgers New Jersey Medical School, Newark, USA), the evaluation also demonstrated that the Mepilex Border Flex dressing draws chronic exudate distally and away from wounds and their margins.
Presented by Alvarez at the Symposium on Advanced Wound Care Fall meeting (SAWC Fall 2019; 12-14 October, Las Vegas, USA), the study was selected as one of four winning oral abstract presentations. He began: “As you know, there is a hypothesis that chronic wounds have a prolonged, exaggerated inflammatory phase, and even in an uninfected wound, this is likely due to an imbalance of metalloproteases and gelatinases that break down the components of the provisional matrix as the wound tries to heal.”
While acute wound fluid is considered quite healthy for cells, chronic wound fluid is toxic, largely because of elevated levels of gelatinases such as MMP-2 and MMP-9 which, in cases of venous ulceration, prevent significant healing from taking place.
Discussing the objectives of the evaluation, Alvarez described the aim of this case series as two-fold; firstly, to study the absorptive profile of Mepilex Border Flex, ensuring that it is suitably designed to spread fluid away from the wound, and secondly, to determine how the use of the dressing impacts upon the balance of proteases in VLUs as they heal.
The method of the study required 10 VLU patients to be treated with the multilayer dressing in addition to compression therapy. As Alvarez explained, all patients included in the investigation had adequate arterial circulation—defined as an ankle-brachial index (ABI) of more than 0.75—and showed no signs of infection. In addition, all VLUs treated as part of the study were less than 25cm² in size, and follow-up visits were conducted weekly in order to measure and clinically evaluate the wounds.
In order to carry out the study, wound fluid was obtained at baseline (day zero, prior to initial treatment) and once every week, for four weeks, from both the wound and the wound dressing. Furthermore, homogenates were analysed using a custom multiplex kit for MMP-9.
Explaining how the dressing is structured, Alvarez outlined: “The dressing has a printed back layer which is waterproof, a retention layer that actually retains a lot of the fluid, and a spreading layer, which is really the unique part of the dressing, as well as a foam layer which rapidly absorbs exudate and a silicone layer that prevents trauma to the wound upon dressing removal.”
“A lot of people do not realise that when you put an absorptive dressing on a venous ulcer and you subsequently compress the wound,” Alvarez added, “it changes the complete profile of the dressing”. Furthermore, the presenter emphasised that if the size of the wound is over 60% of the surface area of the pad within the dressing, it will not succeed because the dressing will not absorb enough.
Results of the evaluation demonstrated a 46% decrease in wound fluid MMP-9 levels over the course of two weeks (p=0.042), following treatment with Mepilex Border Flex. After four weeks, those levels had been reduced even further, decreasing by 79% (p=0.029). Alvarez also revealed that significant levels of MMP-9 were detected in the spreading layer and retention layer of the dressing, which was supported by analysis that show MMP-9 had been transported distally up to 4cm away from the wound.
Alvarez concluded that Mepilex Border Flex represents an effective means of transporting chronic VLU exudate away from the wound with minimal swelling. He said: “The mean MMP levels decreased nearly 50% in two weeks, and this was statistically significant. Mepilex Border Flex also draws the chronic wound exudate outwards, and for use with VLU compression, optimal absorption depends on the capacity of the dressing and therefore size selection.”
I am reluctant to use a bordered foam with a waterproof back layer under a multi-layered compression wrap that will be left on for up to one week. I have seen the silicone border get very moist and this is often detrimental to the periwound.