Functional T lymphocytes infiltrate implanted polyvinyl alcohol foams during surgical wound closure therapy

Effect of Prophylactic Negative Pressure Wound Therapy vs Standard Wound Dressing on Surgical-Site Infection in Obese Women After Cesarean Delivery: A Randomized Clinical Trial

IMPORTANCE

Obesity increases the risk of both cesarean delivery and surgical-site infection. Despite widespread use, it is unclear whether prophylactic negative pressure wound therapy reduces surgical-site infection after cesarean delivery in obese women.

OBJECTIVE

To evaluate whether prophylactic negative pressure wound therapy, initiated immediately after cesarean delivery, lowers the risk of surgical-site infections compared with standard wound dressing in obese women.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter randomized trial conducted from February 8, 2017, through November 13, 2019, at 4 academic and 2 community hospitals across the United States. Obese women undergoing planned or unplanned cesarean delivery were eligible. The study was terminated after 1624 of 2850 participants were recruited when a planned interim analysis showed increased adverse events in the negative pressure group and futility for the primary outcome. Final follow-up was December 18, 2019.

INTERVENTIONS

Participants were randomly assigned to either undergo prophylactic negative pressure wound therapy, with application of the negative pressure device immediately after repair of the surgical incision (n = 816), or receive standard wound dressing (n = 808).

MAIN OUTCOMES AND MEASURES

The primary outcome was superficial or deep surgical-site infection according to the Centers for Disease Control and Prevention definitions. Secondary outcomes included other wound complications, composite of surgical-site infections and other wound complications, and adverse skin reactions.

RESULTS

Of the 1624 women randomized (mean age, 30.4 years, mean body mass index, 39.5), 1608 (99%) completed the study: 806 in the negative pressure group (median duration of negative pressure, 4 days) and 802 in the standard dressing group. Superficial or deep surgical-site infection was diagnosed in 29 participants (3.6%) in the negative pressure group and 27 (3.4%) in the standard dressing group (difference, 0.36%; 95% CI, -1.46% to 2.19%, P = .70). Of 30 prespecified secondary end points, 25 showed no significant differences, including other wound complications (2.6% vs 3.1%; difference, -0.53%; 95% CI, -1.93% to 0.88%; P = .46) and composite of surgical-site infections and other wound complications (6.5% vs 6.7%; difference, -0.27%; 95% CI, -2.71% to 2.25%; P = .83). Adverse skin reactions were significantly more frequent in the negative pressure group (7.0% vs 0.6%; difference, 6.95%; 95% CI, 1.86% to 12.03%; P < .001).

CONCLUSIONS AND RELEVANCE

Among obese women undergoing cesarean delivery, prophylactic negative pressure wound therapy, compared with standard wound dressing, did not significantly reduce the risk of surgical-site infection. These findings do not support routine use of prophylactic negative pressure wound therapy in obese women after cesarean delivery.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03009110.

Using negative pressure wound therapy to prevent surgical site infection

It is estimated that, at the very least, 5% of patients who undergo surgery develop a surgical site infection (SSI). There has been much interest in the use of negative pressure wound therapy (NPWT) as a prophylactic treatment to reduce the risk of SSI. Evidence suggests it can accelerate healing times, reduce both the length of hospital stay and the frequency of dressing changes, and improve patients' quality of life. The efficacy of traditional and portable NPWT systems is similar. However, the latter has an advantage in that it increases patient mobility and does not hinder individuals from carrying out activities of daily living. There are also economic data suggesting that portable NPWT devices are associated with long-term cost savings.

EWMA Document: Negative Pressure Wound Therapy

1. Introduction Since its introduction in clinical practice in the early 1990's negative pressure wounds therapy (NPWT) has become widely used in the management of complex wounds in both inpatient and outpatient care.¹ NPWT has been described as a effective treatment for wounds of many different aetiologies^2,3 and suggested as a gold standard for treatment of wounds such as open abdominal wounds,^4-6 dehisced sternal wounds following cardiac surgery^7,8 and as a valuable agent in complex non-healing wounds.^9,10 Increasingly, NPWT is being applied in the primary and home-care setting, where it is described as having the potential to improve the efficacy of wound management and help reduce the reliance on hospital-based care.¹¹ While the potential of NPWT is promising and the clinical use of the treatment is widespread, highlevel evidence of its effectiveness and economic benefits remain sparse.^12-14 The ongoing controversy regarding high-level evidence in wound care in general is well known. There is a consensus that clinical practice should be evidence-based, which can be difficult to achieve due to confusion about the value of the various approaches to wound management; however, we have to rely on the best available evidence. The need to review wound strategies and treatments in order to reduce the burden of care in an efficient way is urgent. If patients at risk of delayed wound healing are identified earlier and aggressive interventions are taken before the wound deteriorates and complications occur, both patient morbidity and health-care costs can be significantly reduced. There is further a fundamental confusion over the best way to evaluate the effectiveness of interventions in this complex patient population. This is illustrated by reviews of the value of various treatment strategies for non-healing wounds, which have highlighted methodological inconsistencies in primary research. This situation is confounded by differences in the advice given by regulatory and reimbursement bodies in various countries regarding both study design and the ways in which results are interpreted. In response to this confusion, the European Wound Management Association (EWMA) has been publishing a number of interdisciplinary documents^15-19 with the intention of highlighting: The nature and extent of the problem for wound management: from the clinical perspective as well as that of care givers and the patients Evidence-based practice as an integration of clinical expertise with the best available clinical evidence from systematic research The nature and extent of the problem for wound management: from the policy maker and healthcare system perspectives The controversy regarding the value of various approaches to wound management and care is illustrated by the case of NPWT, synonymous with topical negative pressure or vacuum therapy and cited as branded VAC (vacuum-assisted closure) therapy. This is a mode of therapy used to encourage wound healing. It is used as a primary treatment of chronic wounds, in complex acute wounds and as an adjunct for temporary closure and wound bed preparation preceding surgical procedures such as skin grafts and flap surgery. Aim An increasing number of papers on the effect of NPWT are being published. However, due to the low evidence level the treatment remains controversial from the policy maker and health-care system's points of view-particularly with regard to evidence-based medicine. In response EWMA has established an interdisciplinary working group to describe the present knowledge with regard to NPWT and provide overview of its implications for organisation of care, documentation, communication, patient safety, and health economic aspects. These goals will be achieved by the following: Present the rational and scientific support for each delivered statement Uncover controversies and issues related to the use of NPWT in wound management Implications of implementing NPWT as a treatment strategy in the health-care system Provide information and offer perspectives of NPWT from the viewpoints of health-care staff, policy makers, politicians, industry, patients and hospital administrators who are indirectly or directly involved in wound management.

Negative pressure wound therapy induces early wound healing by increased and accelerated expression of vascular endothelial growth factor receptors

Background

Negative pressure wound therapy (NPWT) is commonly used to accelerate wound healing, especially following thoracic surgery; however, the mechanism remains elusive. Given the important role of vasculogenesis in wound healing, we evaluated whether NPWT might accelerate vasculogenesis in the wound area. Toward this end, we investigated the temporal expression of vascular endothelial growth factor receptors (VEGFRs) in an NPWT-wound healing rabbit model.

Methods

Rabbits were divided into an NPWT group and a non-NPWT control group, and tissue samples were collected around wounds made in the skin of each rabbit at five time points: 0, 7, 14, 21, and 28 days after wound creation. Cryopreserved samples were then immunostained and subject to image analysis to evaluate the temporal changes in VEGFR1, VEGFR2, and VEGFR3 expression in the wound-healing process.

Results

Results of histological analysis of the temporal changes in VEGFR expression throughout the healing process showed that compared to the control group, VEGFR2 and VEGFR3 were abundantly and rapidly expressed in the NPWT group, and were expressed earlier than VEGFR1.

Conclusions

NPWT promotes the expression of VEGFR2 and VEGFR3, which provides insight into the mechanism by which NPWT accelerates wound healing.

Level of Evidence: Not ratable.

Use of vacuum-assisted closure to maintain viability of a skin flap in a dog

CASE DESCRIPTION

A 4-year-old sexually intact male Labrador Retriever-Poodle mix was admitted to the hospital for treatment of a wound in the left thoracic region. The wound had been debrided and primary closure had been performed by the referring veterinarian 4 days previously.

CLINICAL FINDINGS

The dog had a 20-cm-long wound covered by a large flap of skin that extended caudally from the scapula over the left side of the thorax. A 3-cm defect was evident at the cranioventral aspect of the wound, from which purulent material was being discharged. The skin flap was necrotic, and the skin surrounding the flap was bruised. Signs of pain were elicited when the wound and surrounding region were palpated. Other findings, including those of thoracic radiography, were unremarkable.

TREATMENT AND OUTCOME

The wound was debrided, and vacuum-assisted closure (VAC) was initiated for 3 days until a healthy bed of granulation tissue developed. A reconstructive procedure was performed with a rotation flap 3 days after VAC dressing removal. The VAC process was reinitiated 2 days following reconstruction because of an apparent failing of the skin flap viability. After 5 days of VAC, the flap had markedly improved in color and consistency and VAC was discontinued. Successful healing of the flap occurred without the need for debridement or additional intervention.

CLINICAL RELEVANCE

Use of VAC led to a good overall outcome for the dog, with complete healing achieved. Additional evaluation of this technique for salvaging failing skin flaps is warranted in dogs, particularly considering that no reliable method for flap salvage in veterinary species has been reported to date.

Closed Incision Negative-Pressure Therapy Is Associated with Decreased Surgical-Site Infections: A Meta-Analysis

BACKGROUND

Negative-pressure therapy has recently been used over closed incisions to decrease surgical-site occurrences, including infection and dehiscence. A meta-analysis was performed to evaluate the effectiveness of closed incision negative-pressure therapy in lowering the incidence of surgical-site infections compared with standard dressings.

METHODS

A literature search was conducted to find publications comparing closed incision negative-pressure therapy to standard incisional care. A fixed-effects model was used to assess between-study and between-incision location subgroup heterogeneity and effect size. Funnel plots were used to assess publication bias.

RESULTS

The overall weighted average rates of surgical-site infection in the closed incision negative-pressure therapy and control groups were 6.61 percent and 9.36 percent, respectively. This reflects a relative reduction in surgical site infection rate of 29.4 percent. A decreased likelihood of surgical-site infection was evident in the closed incision negative-pressure therapy group compared with the control group across all studies, and across all four incision location subgroups. Across all studies, odds of surgical-site infections decreased 0.564 (p < 0.00001). After excluding groin incision studies because of heterogeneity following sensitivity analysis, the odds of surgical-site infection decrease was still 0.496 (p < 0.00001). In addition, overall rates of dehiscence in closed incision negative-pressure therapy and control groups were 5.32 percent and 10.68 percent, respectively.

CONCLUSIONS

The results of this meta-analysis suggest that closed incision negative-pressure therapy is a potentially effective method for reducing surgical-site infections. It also appears that closed incision negative-pressure therapy may be associated with a decreased incidence of dehiscence, but the published data available were too heterogeneous to perform meta-analysis.

Risk factors for wound complications of closed calcaneal fractures after surgery: a systematic review and meta-analysis

BACKGROUND

To better clinical outcomes, open reduction and internal fixations (ORIFs) have been commonly performed in the case of closed displaced intra-articular calcaneal fractures (CDICFs). Nonetheless, postoperative wound complications remain a significant problem. Therefore, the aim of our study is to summarise relevant evidence investigating the risk factors for postoperative wound complications of CDICFs following ORIFs.

METHODS

A meta-analysis was conducted on relevant clinical studies to identify the risk factors for wound complications of CDICFs after ORIFs. Electronic databases were searched for all relevant studies up to October 2014. The Newcastle-Ottawa scale was used to evaluate the methodological quality, and study-specific odds ratios (ORs) were pooled using the fixed-effects model or random-effects model. Sensitivity analysis and meta-regression analysis was performed to evaluate the heterogeneity.

RESULTS

Ten observational studies involving 1559 patients with 1651 fractures were included in this meta-analysis. The results showed that diabetes (OR, 9.76; p < 0.01), no drainage (OR, 5.86; p < 0.01), fracture severity (OR, 3.31; p < 0.01) and bone graft (OR, 1.74; p < 0.01) were the risk factors for wound complications of CDICFs after ORIFs. A trend of more wound complications in patients with a history of smoking was detected. However, female patients, ORIFs performed within 14 days of injury, smoking, hypertension and drinking did not significantly increase the risk of wound complications (p > 0.05).

CONCLUSIONS

Based on available relevant evidence, bone graft, diabetes, no drainage and fracture severity were all associated with an increased risk of wound complications after ORIF for CDICFs.

A portable, disposable system for negative-pressure wound therapy

Negative-pressure wound therapy (NPWT) imparts a number of clinical effects that promote a healing response and, as such, is a well-established means of treating a variety of wound types. Historically, the technique has been primarily used in the hospital setting; however, the introduction of more portable devices has led to an increase in the use of NPWT in the homecare setting, thereby facilitating early discharge of patients from hospital and continuity of care in the community. Portable NPWT devices also have the potential to impact positively on patients' quality of life, allowing increased mobility and freedom to undertake normal activities of daily living. Following the development of its standard Avance® NPWT system and associated dressing kits, Mölnlycke Health Care (Gothenburg, Sweden) has introduced a single-patient-use, disposable NPWT system; Avance Solo. This has been developed with a view to maximising patient freedom and mobility, providing a single-patient-use NPWT solution for multi-week treatment to allow quick and easy discharge of patients from hospital to home, and reducing some of the challenges of logistics and administration associated with the provision of NPWT for the caregiver. As with the standard NPWT system, the single-patient use system is supplied with a number of products incorporating Safetac® adhesive technology to minimise the risk of patients suffering unnecessary pain and trauma associated with dressing changes. This article presents a series of case studies describing procedures and outcomes following the application of the Avance Solo single-patient-use system.

Simultaneous irrigation and negative pressure wound therapy enhances wound healing and reduces wound bioburden in a porcine model

Infected foot wounds are one of the most common reasons for hospitalization and amputation among persons with diabetes. The objective of the study was to investigate a new wound therapy system that employs negative pressure wound therapy (NPWT) with simultaneous irrigation therapy. For this study, we used a porcine model with full-thickness excisional wounds, inoculated with Pseudomonas aeruginosa. Wounds were treated for 21 days of therapy with either NPWT, NPWT with simultaneous irrigation therapy using normal saline or polyhexanide biguanide (PHMB) at low or high flow rates, or control. Data show that NPWT with either irrigation condition improved wound healing rates over control-treated wounds, yet did not differ from NPWT alone. NPWT improved bioburden over control-treated wounds. NPWT with simultaneous irrigation further reduced bioburden over control and NPWT-treated wounds; however, flow rate did not affect these outcomes. Together, these data show that NPWT with simultaneous irrigation therapy with either normal saline or PHMB has a positive effect on bioburden in a porcine model, which may translate clinically to improved wound healing outcomes.

Does the application of incisional negative pressure therapy to high-risk wounds prevent surgical site complications? A systematic review

PURPOSE

The application of incisional negative pressure wound therapy (INPWT) to clean, closed surgical incisions is a growing clinical practice. A systematic review was conducted to evaluate the effect of INPWT on surgical sites healing by primary intention. The primary outcomes of interest are incidence of complications (infection, dehiscence, seroma, hematoma, skin necrosis, or blistering).

METHODS

Two independent reviewers performed a search of the Ovid MEDLINE and EMBASE databases from 2006 to 2012 for published articles. Supplemental searches were performed using reference lists and conference proceedings. Studies were selected for inclusion based on predetermined inclusion and exclusion criteria. Data extraction regarding study quality, demographic and clinical characteristics, and outcomes was performed independently, and data on the incidence of infection was combined using a fixed-effects meta-analysis model.

RESULTS

Ten (5 randomized controlled trials and 5 observational) studies were included, which investigated the outcomes of 626 incisions on 610 patients. Six studies compared INPWT with sterile dry dressings (SDDs). The literature shows a significant decrease in rates of infection when using INPWT. RESULTS on dehiscence do show a decrease in some studies, but results are inconsistent to make a conclusion. Because of limited studies, it is difficult to make any assertions on seroma, hematoma, and skin necrosis.

CONCLUSIONS

This systematic review shows possible evidence of a decrease in the incidence of infection with application of INPWT. Looking at other variables such as dehiscence, seroma, hematoma, and skin necrosis show no consistent data and suggest further studies in order for proper recommendations for INPWT.

Wound Fluid in Diabetic Foot Ulceration

Valid and reproducible sampling techniques as well as processing protocols are required for the assessment of biomarkers and mediators contained in wound exudate. Moreover, the ideal technique should be easy to use even in daily clinical routine. This is challenging since wound fluid represents an inhomogeneous mixture of different exogenous and endogenous sources. Analyzing wound fluid, however, may facilitate clinical decision making. Many techniques for obtaining wound fluid have been described. There is very little validation data, and the array of different techniques appears confusing. Structuring and new standards are needed to avoid wound fluid sampling yielding an “undefined soup.” A lot of wound fluid parameters have been analyzed, although none of them have made its way into clinical practice. Nevertheless, basic principles of wound healing have been established from wound fluid analysis. With adequate techniques suitable for daily practice, basic research might foster our clinical understanding of wound healing with implications for new therapies. So far, research has mainly concentrated on analyzing available sample material with respect to either a wide variety of analytes or comparing acute with chronic wound exudate. Clinical endpoints such as healing or wound infection as well as longitudinal data may indeed be more valuable for clinical practice, enabling the discovery of meaningful biomarkers using a suitable technique.

A pilot study exploring quality of life experienced by patients undergoing negative-pressure wound therapy as part of their wound care treatment compared to patients receiving standard wound care

The use of negative pressure wound therapy (NPWT) has been widely documented as a technique to help heal complex wounds. This article presents the findings of a preliminary study which aimed to explore quality of life (QoL) experienced by patients undergoing NPWT as part of their wound care treatment in comparison to that of patients with a wound using traditional (standard) wound care therapies. A quasi-experimental study was undertaken, with patients treated in wound care/vascular clinics with chronic/acute wounds. QoL impact was measured using the Cardiff Wound Impact Schedule and administered post-consent at timed intervals. Our results identified that there were no real differences in QoL scores recorded by patients over the 12-week period. Although there was no overall interaction between the therapies used for wound healing, NPWT did have an effect on social life: during the first 2 weeks of the application of therapy, patients in the NPWT group reported an increase in the social life domain. The authors conclude that true QoL can only be elicited if an accurate baseline is established or if data is collected over a long enough period to allow comparison of scores over time.

Negative pressure therapy: theory and practice

Negative pressure (wound) therapy, synonymous with topical negative pressure or vacuum therapy mainly cited as branded VAC® (vacuum-assisted closure) therapy, is a mode of therapy used to encourage wound healing. It is used both as primary treatment of chronic and complex wounds and as an adjunct for temporary closure and wound bed preparation preceding surgical procedures such as skin grafts and flap surgery. The device has come into wide and successful use, although the physiological basis of its effect is not yet fully understood, and with a delay, increasingly evidence-based data become available. A meta-analysis was made of peer-reviewed publications (PubMed-Medline) chosen on the basis of inclusion of the terms randomized clinical trial, vacuum-assisted closure, and topical negative pressure. Scientific data were evaluated from experimental animal studies, randomized clinical trials, observations of clinical applications, and case reports on all known effects of VAC therapy. Systematic analysis of the data shows efficacy concerning induction of wound healing mechanisms, especially in the early stage. Increased perfusion can be considered proven. Data analysis shows positive efficacy for treatment of infection. Although this therapy appears effective and its superiority to conventional techniques has been demonstrated, there are still some critical votes concerning efficacy. Because its mechanisms of action remain unclear, and because there is still some gap between evidence-based data and the excellent clinical results, further prospective, randomized, blinded studies are needed. Even so, we conclude that vacuum therapy, used when indicated and especially by experienced surgeons, is an excellent tool to support wound healing.

Angiogenesis in wounds treated by microdeformational wound therapy

BACKGROUND

Mechanical forces play an important role in tissue neovascularization and are a constituent part of modern wound therapies. The mechanisms by which vacuum assisted closure (VAC) modulates wound angiogenesis are still largely unknown.

OBJECTIVE

To investigate how VAC treatment affects wound hypoxia and related profiles of angiogenic factors as well as to identify the anatomical characteristics of the resultant, newly formed vessels.

METHODS

Wound neovascularization was evaluated by morphometric analysis of CD31-stained wound cross-sections as well as by corrosion casting analysis. Wound hypoxia and mRNA expression of HIF-1α and associated angiogenic factors were evaluated by pimonidazole hydrochloride staining and quantitative reverse transcription-polymerase chain reaction (RT-PCR), respectively. Vascular endothelial growth factor (VEGF) protein levels were determined by western blot analysis.

RESULTS

VAC-treated wounds were characterized by the formation of elongated vessels aligned in parallel and consistent with physiological function, compared to occlusive dressing control wounds that showed formation of tortuous, disoriented vessels. Moreover, VAC-treated wounds displayed a well-oxygenated wound bed, with hypoxia limited to the direct proximity of the VAC-foam interface, where higher VEGF levels were found. By contrast, occlusive dressing control wounds showed generalized hypoxia, with associated accumulation of HIF-1α and related angiogenic factors.

CONCLUSIONS

The combination of established gradients of hypoxia and VEGF expression along with mechanical forces exerted by VAC therapy was associated with the formation of more physiological blood vessels compared to occlusive dressing control wounds. These morphological changes are likely a necessary condition for better wound healing.

The influence of low and high pressure levels during negative-pressure wound therapy on wound contraction and fluid evacuation

BACKGROUND

Negative-pressure wound therapy promotes healing by drainage of excessive fluid and debris and by mechanical deformation of the wound. The most commonly used negative pressure, -125 mmHg, may cause pain and ischemia, and the pressure often needs to be reduced. The aim of the present study was to examine wound contraction and fluid removal at different levels of negative pressure.

METHODS

Peripheral wounds were created in 70-kg pigs. The immediate effects of negative-pressure wound therapy (-10 to -175 mmHg) on wound contraction and fluid removal were studied in eight pigs. The long-term effects on wound contraction were studied in eight additional pigs during 72 hours of negative-pressure wound therapy at -75 mmHg.

RESULTS

Wound contraction and fluid removal increased gradually with increasing levels of negative pressure until reaching a steady state. Maximum wound contraction was observed at -75 mmHg. When negative-pressure wound therapy was discontinued, after 72 hours of therapy, the wound surface area was smaller than before therapy. Maximum wound fluid removal was observed at -125 mmHg.

CONCLUSIONS

Negative-pressure wound therapy facilitates drainage of wound fluid and exudates and results in mechanical deformation of the wound edge tissue, which is known to stimulate granulation tissue formation. Maximum wound contraction is achieved already at -75 mmHg, and this may be a suitable pressure for most wounds. In wounds with large volumes of exudate, higher pressure levels may be needed for the initial treatment period.

Navigating new technologies in negative pressure wound therapy

Plastic surgeons and their support staff are tasked with proficient management of a wide variety of complex wounds. Since its introduction, negative pressure wound therapy (NPWT) has increasingly been used within the plastic surgery specialty to improve and simplify wound management. Increased usage of the therapy has prompted the development of a myriad of new NPWT systems. While an expanded product selection allows greater choice to maximize patient outcomes, sound decision-making also requires a clear understanding of the characteristics of various NPWT systems and applications. Wound-specific NPWT systems of varying size are available for low- to moderate-severity wounds, clean closed incisions, and acute abdominal wounds. Wound size and severity, amount of exudate, and patient mobility issues have become important considerations when choosing an NPWT device. The purpose of this article is to familiarize the reader with the latest sophistications in NPWT systems to guide decision making and usage.

Influence on pressure transduction when using different drainage techniques and wound fillers (foam and gauze) for negative pressure wound therapy

Pressure transduction to the wound bed in negative pressure wound therapy (NPWT) is crucial in stimulating the biological effects ultimately resulting in wound healing. In clinical practice, either foam or gauze is used as wound filler. Furthermore, two different drainage techniques are frequently employed. One involves the connection of a non-perforated drainage tube to the top of the dressing, while the other involves the insertion of perforated drains into the dressing. The aim of this study was to examine the efficacy of these two different wound fillers and drainage systems on pressure transduction to the wound bed in a challenging wound (the sternotomy wound). Six pigs underwent median sternotomy. The wound was sealed for NPWT using different wound fillers (foam or gauze) and drainage techniques (see earlier). Pressures between 0 and -175 mmHg were applied and the pressure in the wound was measured using saline-filled catheters sutured to the bottom of the wound (over the anterior surface of the heart) and to the side of the wound (on the thoracic wall). The negative pressure on the wound bed increased linearly with the negative pressure delivered by the vacuum source. In a dry wound, the pressure transduction was similar when using the different wound fillers (foam and gauze) and drainage techniques. In a wet wound, pressure transduction was better when using a perforated drainage tube inserted into the wound filler than a non-perforated drainage tube connected to the top of the dressing (-116 ± 1 versus -73 ± 4 mmHg in the wound at a delivered pressure of -125 mmHg for foam, P < 0·01), regardless of the type of wound filler. Gauze and foam are equally effective at delivering negative pressure to the wound bed. Perforated drainage tubes inserted into the wound filler are more efficient than a non-perforated drainage tubes connected to the top of the dressing. The choice of drainage technique may be particularly important in wounds with a large volume of exudate.

[Vacuum-assisted closure therapy. Current status and basic research]

The gap between the broad clinical use of vacuum-assisted closure therapy (VT) and knowledge of the physiological mechanisms leading to its effectiveness is great. The value of the technique and its future development are dependent on research into these mechanisms. A meta-analysis evaluating the results of basic research on the effectiveness of VT was carried out based on peer reviewed publications. This is considered in relation to other therapeutic approaches of basic research to wound healing (growth factors etc.). Our study includes a concise description of the scientific background to the mechanisms of cell stimulation using basic work on tissue expansion, bone, vessel and nerve distraction as well as in vitro cell stimulation. Evaluation of the scientific data on all known effects of VT was made based on the results from experimental animal studies, the results of randomized clinical studies, observations on clinical applications and case reports. Assessment of the studies was based on design and significance as well as the appraisal of our own clinical experience. Data involving cellular effects (proliferation, synthesis, wound healing), systemic effects (mediators, systemic inflammatory disease), extracellular effects (perfusion, edema, local wound environment, stabilization, barriers) and complex effects of VT (inflammation, matrix function, blood supply) were examined. Systematic analysis of the data allows scientifically interested surgeons rapid access to the theme, the first, to this extent, extensive overview of the current scientific situation as well as a comprehensive bibliography for all areas involving the theme of mechanical cell stimulation. The authors list major areas for future research and encourage the development of multicenter studies.

Mechanisms governing the effects of vacuum-assisted closure in cardiac surgery

SUMMARY

: Vacuum-assisted closure has been adopted as the first-line treatment for poststernotomy mediastinitis as a result of the excellent clinical outcome achieved with its use. Scientific evidence regarding the mechanisms by which vacuum-assisted closure promotes wound healing has started to emerge, although knowledge regarding the effects on heart and lung function is still limited. The organs in the mediastinum are hemodynamically crucial, and in patients with poststernotomy mediastinitis, vulnerable bypass grafts and reduced cardiac function must be taken into consideration during vacuum-assisted closure therapy. This article provides an overview of the effects of vacuum-assisted closure on heart and lung function and summarizes the current knowledge on the mechanisms by which vacuum-assisted closure therapy promotes wound healing.

A biodegradable copolymer for the slow release of growth hormone expedites scarring in diabetic rats

In many diseases wound healing is impaired. This study was designed to establish whether the healing process in diabetes could be improved using a site-specific polymer delivery system containing hGH. The system was first optimized in in vitro experiments performed on cultured fibroblasts taken from healthy and diabetic rats and then tested in an incisional wound model created in the diabetic Wistar rat. In the in vitro experiments using cultured fibroblasts, cell viability, growth, and proliferation were determined, along with polymer degradation, hormone release rates and the expression of TGFbeta1 in the culture medium. For the in vivo experiments, polymer discs with/without GH were inserted through 3 cm incisions made on the backs of the animals. Wound specimens were obtained 7 and 30 days after surgery to evaluate inflammatory/apoptotic cells, metalloprotease expression and neoangiogenesis using microscopy and immunohistochemical techniques. The local administration of GH using a polymer delivery system did not affect the normal wound healing process. Conversely, when used in diabetic animals, epidermal and dermal repair was expedited. Our findings indicate that GH induces cell proliferation, enhances CD4(+) infiltration; increases extracellular matrix protein deposition; stimulates angiogenesis; and diminishes apoptosis at the diabetic wound site. These effects give rise to a comparable wound healing process to that observed in healthy animals.

Vacuum therapy in dermatology: a review

Modern wound therapy is developing continuously. Vacuum therapy is an established procedure to treat wounds. Available on the market is, among others, the V.A.C. (Vacuum Assisted Closure) therapy system. Here, we report the various effects of the vacuum therapy on wounds such as reducing the bacterial contamination, improving granulation and microcirculation and focus on the practical use of the V.A.C., possible complications, contraindications and the economic aspects of the therapy. Since V.A.C. therapy allows rapid mobilization of patients especially with postoperative or posttraumatic wounds, infrequent dressing changes and relative analgesia, this treatment modality is well-accepted by patients with acute or chronic wounds. One explanation for the high acceptance on part of the therapists and the widespread use of the method are the excellent clinical results.

The management of lower extremity wounds using topical negative pressure

The delivery of topical pressures at subatmospheric levels to heal acute and chronic wounds has been widely reported. This article reviews the role of this therapeutic modality to treat wounds of the lower extremity. Recent literature is re-viewed, and mechanisms of action of this process are also discussed.

Vacuum assisted closure: a review of development and current applications

Vacuum assisted closure is being increasingly used for wound management. This review examines the history of its development and appraises the current evidence on its use so far.

Vacuum-assisted closure complicated by erosion and hemorrhage of the anterior tibial artery

We report an erosion and hemorrhage of a left anterior tibial artery associated with a vacuum-assisted closure device. To our knowledge, this report represents the first arterial erosion associated with a vacuum-assisted closure device. We estimate our patient lost 6 units of blood. The hemorrhage was complicated by anticoagulation and a traumatic setting. Based on our complication, we believe great care should be taken when placing a vacuum-assisted closure device adjacent to an exposed artery.

Comparison of inflammatory and systemic sources of growth factors in acute and chronic human wounds

Inflammatory cells are generally assumed to be the primary source of most growth factors/cytokines that participate in wound healing. Correspondingly, most attempts to enhance wound healing have been directed at the wound itself. However, certain key factors such as insulin-like growth factor-I (IGF-I) and related proteins are present in blood in sufficient quantities to suggest significant contributions from outside the wound. Because little is known of the dynamics of IGF family members in wounds, particularly in human wounds, we serially measured the mRNAs and proteins of the IGF family in fluid and tissues taken from acute as well as chronically inflamed human wounds and compared them to their corresponding concentrations in blood. We also measured transforming growth factor-beta1 and -beta3, vascular endothelial growth factor, interleukin-1beta, matrix metalloproteinases and selected isomers/receptors, all of which are associated with inflammation. All IGF proteins reached their highest concentrations immediately after injury. No difference between IGF-I mRNA expression between acute and inflamed wounds was found. As a group, IGF-related proteins, in contrast to transforming growth factor-beta, vascular endothelial growth factor, and interleukin-1beta, are highly correlated to and are generally below their concentrations in blood and are not elevated by inflammation. The IGF family therefore appears to enter wounds, even inflamed wounds, mainly from blood. If blood IGF-I is low, wound levels are lower. This data suggests that healing impairment due to IGF-I deficiency can be readily detected and is, at least in part, easily and safely correctable.

Treatment of periprosthetic soft tissue infection of the groin following vascular surgical procedures by means of a polyvinyl alcohol-vacuum sponge system

Deep groin infections after prosthetic vascular surgical procedures represent a serious complication of surgical practice. Septicemia and/or erosive hemorrhage can both be consequences. In this situation, removal of the graft appears to be the only option. However, if the infection is detected early (type Szilagyi III), local treatment to eradicate the infection could serve as an alternative. Twenty-four patients with confirmed infection of the soft tissue adjacent to the prosthetic material in the groin were treated locally by implantation of a vacuum sponge system. Duration of this treatment was 2 weeks. All patients showed excellent tissue granulation of the wound area and the microbial stains were negative at the end of therapy. In 21 patients the wound could be primarily closed after explantation of the sponge. Three patients underwent open treatment because of a skin defect. After 12 months, the wounds had healed well in all patients. Histologic evaluation revealed a physiological healing process. Deep soft tissue infections of the groin adjacent to prosthetic vascular material (type Szilagyi III) can be treated effectively and safely with the vacuum sponge system. The treatment is inexpensive, easy to perform, and the initial vascular reconstruction can be preserved.