Hypochlorous Acid: A Practical Choice for Instillation With Negative Pressure Wound Therapy When Surgical Closure is Anticipated

Wound cleansing is an essential part of wound therapy that allows transition to subsequent therapies in order to promote granulation tissue formation and epithelialization and provide wound coverage or primary closure. Negative pressure wound therapy with instillation and dwell time (NPWTi-d; V.A.C. VERAFLO Therapy, KCI) utilizes the instillation of topical wound solutions and negative pressure for wound cleansing and removal of infectious materials.^1-5 This approach has gained increasing utilization and interest due, in part, to the increasing complexity of wounds and patient conditions. Best practices for the use of NPWTi-d have shifted in recent years based on a growing body of evidence and expanded worldwide experience with the technology. Although initially largely used as a last-resort therapy, clinicians are using NPWTi-d to influence the wound healing process by combining the mechanisms of action of standard NPWT (ie, to draw wound edges together, promote perfusion and granulation tissue formation, remove exudate, and reduce edema) with the benefits of cyclic cleansing that dilutes and renders wound debris soluble.

Early experiences with NPWTi-d indicated the therapy assists with wound bed preparation. In the acute care setting where the length of hospital stay is so important, Kim et al³ and Gabriel et al⁴ showed the clinical efficacy of  NPWTi-d in comparison to traditional negative pressure wound therapy (NPWT) without instillation reduced the length of hospital stay and the number of operative debridements, along with fewer days to definitive surgical closure.
The 2019 international consensus guidelines update¹ notes NPWTi-d may be used as an adjunct therapy in traumatic wounds; surgical, including dehisced, wounds; diabetic wounds; venous leg ulcers; pressure injuries/ulcers; wounds with exposed intact bone; wounds with treated, underlying osteomyelitis; infected or contaminated wounds in the presence of orthopedic fixation hardware; full-thickness burns after excision; wounds resulting from evacuation of a hematoma and when hemostasis is achieved; and wounds that are a bridge between staged/delayed amputation. Compatible solutions that may be used with NPWTi-d with reticulated open cell foam-V (VERAFLO) or reticulated open cell foam; Cleanse Choice dressings include normal saline, hypochlorous acid (HOCl) solution, sodium hypochlorite solution (dilute Dakin’s solution 0.125%), acetic acid solution (0.25% to 1.0%), and polyhexamethylene biguanide (0.1%) + betaine (0.1%).

Although the consensus panel concluded that normal saline was their instillation solution of choice, other solutions may be of greater assistance in wound bed preparation, specifically when surgical closure is anticipated. However, bioburden must be addressed to achieve surgical success. Whether related to its mechanics or fluid dynamics, NPWTi-d can help reduce the bacterial load and subsequently the incidence of postoperative infection.

V.A.C. VERAFLO Therapy is designed to cleanse the wound through instillation of topical wound cleansers that can help soften and loosen wound debris. As part of the process, the therapy delivers topical antiseptic/antimicrobial wound solutions that can help reduce the bacterial population; remove solubilized wound debris and infectious materials, including planktonic bacteria; promote granulation tissue formation and perfusion; help prepare the wound for closure; and provide contained and controlled wound irrigation without the risk of bacterial aerosolization typically generated during manual lavage. Combining 2 hours of NPWT with intermittent instillation of fluid and allowing that fluid to dwell 20 minutes helps with wound cleansing and wound bed preparation. These settings can be adjusted depending on the size of the wound and amount of bacterial burden. NPWTi-d utilizes the instillation of topical wound solutions and negative pressure for wound cleansing and removal of infectious materials.^3-6

HOCl, discovered in 1832, was found to be more cell friendly than the key ingredient of Dakin’s solution, sodium hypochlorite (in common terminology, bleach), decreasing the level of bacteria in granulating wounds and allowing continued healing without cytotoxicity. Several HOCl acid products are available to the wound care clinician. Vashe Wound Solution (Urgo Medical North America) is a stable, highly concentrated, pure HOCl solution formulated at a pH of 5.5, the same pH level as healthy, healing skin. With its antimicrobial preservative, Vashe is able to remove microbial particles and wound debris. To date, no resistance to HOCl has been reported.

Bacterial presence in the wound bed does not necessarily impede healing, but the formation of microcolonies of bacteria (ie, biofilm) that are resistant to antibiotic therapy can result in a chronic inflammatory response that further thwarts healing. Robson⁷ described 2 biofilm components: polysaccharides and proteins. The former comprise long chains of simple sugars (monosaccharides) that potentially can be broken down by dynamic liquid flow and may be the mechanism by which Vashe works. Studies using Vashe show that the 2 components of biofilm are reduced because they have been broken down physically. The extracellular protective matrix of the biofilm is likely also disrupted by hydrolysis and nonenzymatic proteolysis.⁸

Day et al⁹ evaluated the mechanical efficacy of Vashe on methicillin-resistant Staphylococcus aureus and Pseudomonas biofilm in vivo and in vitro and found significant reduction in colony forming units as compared to normal saline; povidone-iodine eliminated most viable cells.

The clinical efficacy of Vashe on biofilm and wound bed preparation before surgical closure has not been studied to date. However, clinical experience regarding combination therapies of NPWTi-d and Vashe used before surgical closure in select patients has shown promise. The recent 2019 guidelines from the National Pressure Injury Advisory Panel (NPIAP) recommend the use of HOCl-based solutions in cleansing pressure ulcers. The following cases describe the management of pressure ulcers, generally keeping within those guidelines for wound cleansing; they provide useful methods of achieving wound closure via the use of NPWT, HOCl, and surgery when appropriate.  

Infected stage 4 sacral ulcer. A 68-year-old woman with a history of paraplegia presented with an acutely infected sacral ulcer clinically noted by evident discharge, foul smell, and progressive size. Wound cultures revealed S aureus.  The ulcer was treated in phases; phase 1 included surgical debridement, specifically excision of ulcer and partial ostectomy, followed immediately by NPWTi-d with HOCl. NPWT was administered for 2 hours with 20 minutes dwell time. After 48 hours of therapy, the patient was returned to the operating room. The ulcer was clean without evidence of ongoing infection, so  definitive closure with flap advancement was performed. Amnion particulate was placed as a regenerative tissue matrix to stimulate cellular proliferation to optimize healing. NPWT (PREVENA Therapy) was initiated on the incision immediately following closure (see Figure 1A-C). The patient was discharged to home after 48 hours of therapy, with PREVENA continued at home for an additional 7 days. At the end of this therapy, the surgical sites showed no evidence of infection. Ultimately, the patient developed recurrent ulcers and required additional wound therapy.
 

Multiple stage 4 pressure ulcers. A 46-year-old woman with paraplegia presented with multiple pressure ulcers on her sacrum, bilateral ischium, and bilateral hips, including an extensive left hip ulcer with the complete femoral head exposed. The patient was admitted emergently for acute progression of the left hip ulcer with exposed bone. Orthopedic intervention included a Girdlestone procedure for acute and chronic osteomyelitis of the femur. Postoperatively, the patient developed a hematoma and was returned to the operating room 2 days later for hematoma evacuation.

Her remaining ulcers then were addressed and treated in stages. Although no evidence of acute infection was noted, treatment was provided in phases because of the extent of the ulcers.  Phase 1 included surgical debridement, specifically excision of ulcer and partial ostectomy. NPWTi-d with HOCl was initiated immediately postoperatively per a NPWT protocol of 2 hours and 20 minutes dwell time. Following 48 hours of therapy, the patient was returned to the operating room where the ulcers were found to be clean without evidence of infection or necrotic debris. Definitive closure with flap advancement of the remaining ulcers was performed. Amnion particulate was placed as a regenerative tissue matrix to stimulate cellular proliferation to optimize healing and debride her ulcers. Incisional NPWT was initiated with a PREVENA CUSTOMIZABLE Dressing immediately following closure for 9 days.  

The patient was discharged to a long-term care facility after 48 hours of therapy. Upon removal of the dressing after 7 days of additional therapy at the care center, her incisions were intact with no evidence of infection.  She subsequently developed incisional dehiscence secondary to poor patient adherence, but the surgical sites remained without infection and were reclosed without incident (see Figure 2A-C).

Biofilm and the associated bacterial burden have been recognized as an impediment to wound progression. NPWT as an adjunct has been well accepted as a tool to assist with wound bed preparation, and more recently NPWTi-d has been advocated in the acute care setting to address these difficult wounds. HOCl, specifically Vashe, has been utilized as the solution instilled in these difficult wound types with good success. It is proposed that the ability of Vashe to eliminate bacteria and disrupt biofilm, both likely via fluid dynamics-related mechanical actions, may offer an important care option, particularly when addressing the cost and burden of pressure ulcers.