Comparison of antibacterial effects among three foams used with negative pressure wound therapy in an ex vivo equine perfused wound model

Polyurethane foam dressing with non-adherent membrane improves negative pressure wound therapy in pigs

OBJECTIVE

Negative pressure wound therapy (NPWT) is considered to be an effective technique to promote the healing of various wounds. The aim of this study was to evaluate different wound dressings combined with NPWT in treating wounds in Wuzhishan pigs.

METHOD

Excisions were made in the backs of the pigs and were covered with polyvinyl alcohol (PVA) dressing, polyurethane (PU) dressing or PU dressing with non-adherent membrane (PU-non-ad). NPWT was applied to the wound site. In the control group, basic occlusive dressing (gauze) without NPWT was applied. On days 0, 3, 7, 14, 21 and 28 post-surgery, the wound size was measured during dressing change, and wound healing rate (WHR) was calculated. In addition, blood perfusion within 2cm of the surrounding wound was measured by laser doppler flowmetry. Dressing specimen was collected and microbiology was analysed. Granulation tissues from the central part of the wounds were analysed for histology, vascular endothelial growth factor (VEGF) and cluster of differentiation 31 (CD31) mRNA expression.

RESULTS

The PU-non-ad-NPWT significantly (p<0.01) accelerated wound healing in the pigs. Further pathological analysis revealed that the non-adherent membrane effectively protected granulation tissue formation in PU-NPWT treated wounds. The blood perfusion analysis suggested that the non-adherent membrane improved the blood supply to the wound area. Microbiological analysis showed that non-adherent membrane decreased the bacterial load in the PU-NPWT dressing. VEGF and CD31 mRNA expression was upregulated in the wound tissue from the PU-non-ad-NPWT treated groups.

CONCLUSION

In this study, the PU dressing with non-adherent membrane was an ideal dressing in NPWT-assisted wound healing.

Ex vivo comparison of V.A.C.® Granufoam Silver™ and V.A.C.® Granufoam™ loaded with a first-in-class bis-dialkylnorspermidine-terphenyl antibiofilm agent

Implementation of negative pressure wound therapy (NPWT) as a standard of care has proven efficacious in reducing both the healing time and likelihood of nosocomial infection among pressure ulcers and traumatic, combat-related injuries. However, current formulations may not target or dramatically reduce bacterial biofilm burden following therapy. The purpose of this study was to determine the antibiofilm efficacy of an open-cell polyurethane (PU) foam (V.A.C.® Granufoam™) loaded with a first-in-class compound (CZ-01179) as the active release agent integrated via lyophilized hydrogel scaffolding. An ex vivo porcine excision wound model was designed to perform antibiofilm efficacy testing in the presence of NPWT. PU foam samples loaded with a 10.0% w/w formulation of CZ-01179 and 0.5% hyaluronic acid were prepared and tested against current standards of care: V.A.C.® Granufoam Silver™ and V.A.C.® Granufoam™. We observed statistically significant reduction of methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii biofilms with the CZ-01179 antibiofilm foam in comparison to current standard of care foams. These findings motivate further development of an antibiofilm PU foam loaded with CZ-01179.

Negative-Pressure Wound Therapy (NPWT) in Horses: A Scoping Review

Obtaining a healthy wound environment that is conductive to healing in horses can be challenging. Negative-pressure wound therapy (NPWT) has been employed in humans to enhance wound healing for decades. The existing evidence for the effectiveness of NPWT remains uncertain in equine medicine. The aim of this review is to investigate NPWT applications and benefits in horses. A scoping review was performed according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines for scoping reviews on three databases (PubMed, Web of Science-Thompson Reuters, and Wiley Online Library). Twenty-four manuscripts were considered. After removing duplicates, 17 papers underwent abstract screening. Of these, 16 + 1 (cited by others) were evaluated for eligibility according to PICOs, including no case reports/retrospective studies, four original articles, and three reviews. Fifteen manuscripts met the inclusion criteria. The focus of the articles was wound management; they included three reports of wounds communicating with synovial structures. Traumatic wounds and surgical-site infections are indications for NPWT. NPWT presents several advantages and few complications making it an attractive alternative to conventional wound management. However, randomized controlled trials should be performed to quantify the benefits and establish precise protocols in horses.

Use of Negative Pressure Wound Therapy in the Treatment of Limb Wounds: A Case Series of 42 Horses

Traumatic limb injuries are common in horses. Negative pressure wound therapy (NPWT) has been proven to promote wound healing in human medicine. It has also been described for the treatment of wounds in horses. In this retrospective study, clinical records of 42 (n = 42) animals were assessed. Categories of wounds, duration of NPWT application, frequency of resetting the NPWT device, technical complications, and tolerance to the procedure were recorded. 42 wounds were classified as bony (n = 15; 36 %), articular (n = 14; 33 %), tenosynovial (n = 9; 21%), muscular (n = 2; 5%) and cutaneous (n = 2; 5 %). NPWT was used to help (1) first intention healing by preoperative (n = 3; 7 %) or postoperative (n = 7; 17%) application, (2) second intention healing (n = 31; 74%), and (3) delayed primary closure (n = 1; 2%). Duration of NPWT application ranged from 2 to 36 days (mean 11.5), with the system staying in place for periods ranging from 1 to 7 days (mean 4.5). In 69% (n = 29) of the cases, healing was considered satisfactory at discharge. 26 % (n = 11) of horses were discharged whilst ideally NPWT should have been continued. 2 animals (n = 2; 5%) were euthanized after surgery due to unrelenting pain. The procedure was well tolerated except in 1 horse who showed signs of discomfort at the first application. This study demonstrated that NPWT with long periods of application can be used successfully to manage various types of limb wounds.

Effects of various wound dressings on microbial growth in perfused equine musculocutaneous flaps

OBJECTIVE

To compare the effect of multiple wound dressings on microbial growth in a perfused equine wound model.

SAMPLE

Abdominal musculocutaneous flaps from 16 equine cadavers.

PROCEDURES

8 full-thickness skin wound covered were created in each flap. Tissues were perfused with saline (0.9% NaCl) solution. Wounds were inoculated with methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa (10⁶ CFUs), incubated, and covered with a dressing containing activated charcoal, boric acid, cadexomer iodine, calcium alginate, manuka honey, nanoparticle silver, or polyhexamethylene biguanide or with a control (nonadherent gauze) dressing. Muscle biopsy specimens were obtained at baseline (immediately prior to dressing application) and 6, 12, 18, and 24 hours later for mean bacterial load (MBL) determination. The MBLs at each subsequent time point were compared with that at baseline within dressing types, and MBLs at each time point were compared among dressing types.

RESULTS

MBLs in MRSA-inoculated wounds covered with cadexomer iodine dressings were significantly decreased from baseline at the 6- and 12-hour time points. For P aeruginosa-inoculated wounds, MBLs were significantly increased from baseline in all wounds at various times except for wounds with cadexomer iodine dressings. The MBLs of wounds with cadexomer iodine dressings were lower than all others, although not always significantly different from those for wounds with boric acid, manuka honey, nanoparticle silver, and polyhexamethylene biguanide dressings.

CONCLUSIONS AND CLINICAL RELEVANCE

In this nonviable perfused wound model, growth of MRSA and P aeruginosa was most effectively reduced or inhibited by cadexomer iodine dressings. These results and the effect of the dressings on wound healing should be confirmed with in vivo studies.

Microfluidics Mediated Production of Foams for Biomedical Applications

Within the last decade, there has been increasing interest in liquid and solid foams for several industrial uses. In the biomedical field, liquid foams can be used as delivery systems for dermatological treatments, for example, whereas solid foams are frequently used as scaffolds for tissue engineering and drug screening. Most of the foam functionalities are largely correlated to their mechanical properties and their structure, especially bubble/pore size, shape, and interconnectivity. However, the majority of conventional foaming fabrication techniques lack pore size control which can induce important inhomogeneities in the foams and subsequently decrease their performance. In this perspective, new advanced technologies have been introduced, such as microfluidics, which offers a highly controlled production, allowing for design customization of both liquid foams and solid foams obtained through liquid-templating. This short review explores both the fabrication and the characterization of foams, with a focus on solid polymer foams, and sheds the light on how microfluidics can overcome some existing limitations, playing a crucial role in their production for biomedical applications, especially as scaffolds in tissue engineering.

Feasibility of a disposable canister-free negative-pressure wound therapy (NPWT) device for treating open wounds in horses

BACKGROUND

Wounds are among the most common medical conditions affecting horses and have a major economic impact on the horse industry. Wound healing in horses is distinct to that documented in other species, and often results in delayed healing and extensive scarring, with compromised functional and aesthetic outcomes. To date, there is no conventional method objectively proven to accelerate healing or to successfully prevent complications associated with second intention healing. Several effects of Negative Pressure Wound Therapy (NPWT) may be particularly useful to the management of wounds in horses. However, cumbersome designs of classic NPWT devices render them unsuitable for equine practice. A new lightweight, portable and disposable unit of NPWT (PICO®), should facilitate the use of this modality by equine practitioners. The aim of this study was to evaluate the feasibility of using this canister-free system to treat experimental open wounds in horses.

RESULTS

No difficulties were encountered with the application or maintenance of the PICO® system during the ex vivo experiment or during the preliminary in vivo experiment conducted on intact skin. All horses readily tolerated the PICO® but difficulties with adhesion and seal prevented the completion of the experimental wound study despite the use of many adjunctive adhesives.

CONCLUSION

The current PICO® dressing design is not suitable to be used as a dressing for open wounds in horses though the device is well tolerated by equine patients. A dressing with a wider adhesive edge, a superior adhesive and a more flexible pad would likely be better adapted to enable its future use in equine practice.

Wound Management: Wounds with Special Challenges

Distal limb wounds in horses heal substantially different than trunk wounds, commonly resulting in exuberant granulation tissue and exposed and sequestered bone. Surgical intervention of severe rectovaginal lacerations in the mare should be delayed until the tissues have heeled and scar tissue has remodeled. Wounds resulting in severe hemorrhage require appropriate emergent fluid therapy and potentially transfusion therapy.