Role of oxygen in wound healing: a review of evidence

Advanced wound management approaches in Hidradenitis Suppurativa postsurgical lesions

The most appropriate management of recurrent Hidradenitis Suppurativa (HS) lesions consists of wide surgical removal of the lesions with subsequent healing by second intention. Successful wound healing depends on the choice of an adequate wound dressing, targeted to the features of the wound.We enrolled 25 patients randomized into three groups according to the advanced dressing used in second intention healing of postsurgical wounds (standard therapy, an oxygen-enriched oil-based medical device with prolonged release of reactive oxygen species [ROS], ultra-portable negative pressure therapy). Data on wound size, clinical appearance of the wound bed, and pain experienced by the patient were collected twice a week for 4 weeksNo statistically significant differences were observed between the different groups evaluated. Oxygen-enriched oil-based medical device with prolonged release of ROS can be included in the principle of HS-tissue, inflammation, moisture, and epithelium (TIME).

Gelatin methacryloyl (GelMA) loaded with concentrated hypoxic pretreated adipose-derived mesenchymal stem cells(ADSCs) conditioned medium promotes wound healing and vascular regeneration in aged skin

BACKGROUND

Aging skin is characterized by a disturbed structure and lack of blood supply, which makes it difficult to heal once injured. ADSCs secrete large amounts of cytokines, which promote wound healing and vascular regeneration through paracrine secretion, and the number of cytokines can be elevated by hypoxic pretreating. However, the components of ADSCs are difficult to retain in wounds. Gelatin methacrylate (GelMA) is a photopolymerizable hydrogel synthesized from gelatin and has recently emerged as a potentially attractive material for tissue engineering applications. GelMA loaded with concentrated hypoxic pretreated ADSCs conditioned medium could provide a new method of treating wounds in aged skin.

METHODS

Primary ADSCs were isolated from human adipose tissue and characterized by flow cytometry and differentiation test. ADSCs in passages 4-6 were pretreated in the hypoxic and normoxic environments to collect conditioned medium, the conditioned medium was then concentrated to prepare concentrated ADSCs conditioned medium(cADSC-CM)(the one collected from ADSCs under hypoxia was called hypo-CM ,and the one from normoxia was called nor-CM). The concentration of cytokines was detected. After treated with cADSC-CM, the abilities of proliferation, migration, and tube formation of human umbilical vascular endothelial cells (HUVECs) were assayed, and Akt/mTOR and MAPK signal pathway was detected using western blotting. GelMA+hypo-CM hydrogel was prepared, and a comprehensive evaluation of morphology, protein release efficiency, degradation rate, mechanical properties, and rheology properties were performed. Full-thickness skin wounds were created on the backs of 20-month-old mice. After surgery, GelMA, GelMA+F12, GelMA+hypo-CM, and GelMA+nor-CM were applied to the wound surface respectively. H&E, Masson, and immunohistochemistry staining were performed, and a laser Doppler perfusion imager was used to evaluate the blood perfusion. The student's t-test was used for analysis between two groups and a one-way analysis of variance (ANOVA) was used for analysis among multi groups.

RESULTS

Our results revealed that 1) wounds in aged skin healed more slowly than that in young skin and exhibited poorer perfusion; 2) hypoxic pretreated ADSCs secreted more cytokines including VEGF by activating HIF1α; 3) hypo-CM promoted proliferation and migration of HUVECs through VEGF/Akt/mTOR and MAPK signal pathway; 4) GelMA-hypoCM accelerated wound healing and angiogenesis in aged skin in vivo.

CONCLUSION

GelMA loaded with concentrated hypoxic pretreated adipose-derived mesenchymal stem cells conditioned medium could accelerate wound healing in aged skin by promoting angiogenesis.

Preliminary Characterization of a Polycaprolactone-SurgihoneyRO Electrospun Mesh for Skin Tissue Engineering

Skin is a hierarchical and multi-cellular organ exposed to the external environment with a key protective and regulatory role. Wounds caused by disease and trauma can lead to a loss of function, which can be debilitating and even cause death. Accelerating the natural skin healing process and minimizing the risk of infection is a clinical challenge. Electrospinning is a key technology in the development of wound dressings and skin substitutes as it enables extracellular matrix-mimicking fibrous structures and delivery of bioactive materials. Honey is a promising biomaterial for use in skin tissue engineering applications and has antimicrobial properties and potential tissue regenerative properties. This preliminary study investigates a solution electrospun composite nanofibrous mesh based on polycaprolactone and a medical grade honey, SurgihoneyRO. The processing conditions were optimized and assessed by scanning electron microscopy to fabricate meshes with uniform fiber diameters and minimal presence of beads. The chemistry of the composite meshes was examined using Fourier transform infrared spectroscopy and X-ray photon spectroscopy showing incorporation of honey into the polymer matrix. Meshes incorporating honey had lower mechanical properties due to lower polymer content but were more hydrophilic, resulting in an increase in swelling and an accelerated degradation profile. The biocompatibility of the meshes was assessed using human dermal fibroblasts and adipose-derived stem cells, which showed comparable or higher cell metabolic activity and viability for SurgihoneyRO-containing meshes compared to polycaprolactone only meshes. The meshes showed no antibacterial properties in a disk diffusion test due to a lack of hydrogen peroxide production and release. The developed polycaprolactone-honey nanofibrous meshes have potential for use in skin applications.

Predicting hyperbaric oxygen therapy success using the decision tree approach

Introduction

Hyperbaric oxygen therapy (HBOT), a procedure that involves the patient inhaling 100% oxygen gas under pressure, is currently used as an adjunctive treatment option for certain inflammatory conditions. HBOT can improve wound healing by increasing the rate of angiogenesis in injured tissue by increasing levels of vascular endothelial growth factor (VEGF). VEGF causes re-epithelialization, the migration of endothelial cells, and the formation of granulation tissue, which are involved in the wound healing process.

Methods

This study contains secondary data analyses of information previously collected in two separate studies, each concerning the effects of HBOT on diabetic foot ulcers and crush injury fractures at Prof. Dr. R. D. Kandou Hospital Manado and Siloam Hospital Manado from 2019 to early 2020.

Results

Based on the classification tree analysis, the predictors of HBOT success were leukocytes level (34%), platelet count (32%), and age (26%). The conditional inference tree analysis also indicated significant leukocyte levels, age, and platelet counts (p < 0.001), with which the interpretation of these results was the same as the classification tree analysis method. The results obtained from the random forest analysis revealed that the mean value of Gini reduction for leukocytes (207.3), platelets (110.2), age (97.9), and hemoglobin (57.9) can be used as indicators of successful HBOT. These three methods support that age, leukocytes, and platelets are determinants of HBOT success, while hemoglobin levels were only significant in one analysis method. Therefore, a new, proposed algorithm containing these factors was assembled from the results of this study.

Conclusion

HBOT cannot be separated from specific variables that contribute to and can predict its success.

Browning of White Adipocytes in Fat Grafts Associated With Higher Level of Necrosis and Type 2 Macrophage Recruitment

BACKGROUND

Induced browning adipocytes were assumed less viable and more prone to necrosis for their hypermetabolic property. A previous study showed that browning of adipocytes was more evident in fat grafts with necrosis in humans.

OBJECTIVES

The authors aimed to estimate whether fat transfer-induced browning biogenesis was associated with necrosis and its potential inflammation mechanisms in murine models.

METHODS

Human subcutaneous adipose from thigh or abdomen of 5 patients via liposuction was injected in 100 µL or 500 µL (n = 20 per group) into the dorsal flank of 6- to 8-week-old female nude mice fed with normal chow diet and harvested after 2, 4, 8, and 12 weeks. Control groups did not receive any grafting procedures (sham operation), where lipoaspirates were analyzed immediately after harvest. Histology and electronic microscopy, immunological analyses of browning markers, necrosis marker, and type I/II macrophages markers in mice were performed.

RESULTS

Histology and electronic microscopy showed browning adipocytes in fat grafts with a higher level of necrosis (0.435 ± 0.017 pg/mL for cleaved caspase-3, **P < 0.01), IL-6 (749.0 ± 134.1 pg/mL,***P < 0.001) and infiltration of type 2 macrophage profiles in mice (twofold increase, *P < 0.05).

CONCLUSIONS

Browning of adipocytes induced by fat transfer in mice is in parallel with post-grafting necrotic levels associated with elevated interleukin-6 and activated type 2 macrophage profiles, which promote browning development.

The repetitive application of cold atmospheric plasma (CAP) improves microcirculation parameters in chronic wounds

BACKGROUND

Chronic wounds, such as venous leg ulcers, diabetic foot ulcers, and pressure ulcers, impose a significant burden on patients and health care systems worldwide. Cold atmospheric plasma (CAP) accelerates wound healing and decreases bacterial load in chronic wounds in both in vitro and in vivo experiments. For the first time, we examined the effects of a repetitive application of CAP on the microcirculation in chronic wounds.

HYPOTHESIS

The repetitive application of cold atmospheric plasma application further improves microcirculation in chronic wounds.

METHODS

Twenty patients with chronic wounds were treated repetitively with CAP. The repetitive application consisted of three CAP sessions, each lasting 90 s and separated by a 10-minute microcirculation measuring period. Microcirculation parameters were assessed with combined Laser-Doppler-Flowmetry and spectrophotometry in a tissue depth of 2 mm.

RESULTS

Tissue oxygen saturation was significantly increased after the first CAP application. The effect amplitude and duration were further increased after the second and third CAP application with a maximum increase by 16,7% (percent change; p = 0,004 vs. baseline) after the third application. There was no significant increase in capillary blood flow until the third CAP application. After the third CAP application, an increase by 22,6% (p = 0,014) was observed. Postcapillary filling pressure was not significantly increased over the measuring period. The repetitive application of CAP further enhances the microcirculation in chronic wounds compared to a single application.

CONCLUSION

The repetitive application of CAP boosts and prolongs tissue oxygen saturation and capillary blood flow in chronic wounds compared to a single application. This insight could provide an impetus for new treatment protocols.

Inverse Poly-High Internal Phase Emulsions Poly(HIPEs) Materials from Natural and Biocompatible Polysaccharides

This paper shows one of the few examples in the literature on the feasibility of novel materials from natural and biocompatible polymers like inulin (INU) or glycol chitosan (GCS) templated by the formation of o/w (inverse) high internal phase emulsion (HIPE). To the best of our knowledge, this is the first example of inverse polyHIPEs obtained from glycol chitosan or inulin. The obtained polyHIPEs were specifically designed for possible wound dressing applications. The HIPE (pre-crosslinking emulsion) was obtained as inverse HIPE, i.e., by forming a cream-like 80:20 v/v o/w emulsion by using the isopropyl myristate in its oil phase, which is obtained from natural sources like palm oil or coconut oil. The surfactant amount was critical in obtaining the inverse HIPE and the pluronic F127 was effective in stabilizing the emulsion comprising up to 80% v/v as internal phase. The obtained inverse HIPEs were crosslinked by UV irradiation for methacrylated INU or by glutaraldehyde-crosslinking for GCS. In both cases, inverse poly-HIPEs were obtained, which were physicochemically characterized. This paper introduces a new concept in using hydrophilic, natural polymers for the formation of inverse poly-HIPEs.

Skin Wound Healing Process and New Emerging Technologies for Skin Wound Care and Regeneration

Skin wound healing shows an extraordinary cellular function mechanism, unique in nature and involving the interaction of several cells, growth factors and cytokines. Physiological wound healing restores tissue integrity, but in many cases the process is limited to wound repair. Ongoing studies aim to obtain more effective wound therapies with the intention of reducing inpatient costs, providing long-term relief and effective scar healing. The main goal of this comprehensive review is to focus on the progress in wound medication and how it has evolved over the years. The main complications related to the healing process and the clinical management of chronic wounds are described in the review. Moreover, advanced treatment strategies for skin regeneration and experimental techniques for cellular engineering and skin tissue engineering are addressed. Emerging skin regeneration techniques involving scaffolds activated with growth factors, bioactive molecules and genetically modified cells are exploited to overcome wound healing technology limitations and to implement personalized therapy design.

Preliminary Results of a New Treatment Strategy for Relapsed Left Ventricular Assist Device-Specific Infections

BACKGROUND

Relapsed ventricular assist device-specific infections are associated with high morbidity, mortality, and hospital costs. A new combination of cold atmospheric plasma and special dressing technique with negative pressure wound therapy with an additional underlay of carbon cloth and hypochlorite rinsing solutions has been developed and reported in this study.

METHODS

Between January 2016 and January 2018, 9 patients with relapsed infected driveline or pump pocket infection were treated with this new combined strategy. The primary endpoint was complete wound healing without recurrence of infection, defined as the presence at the same site within the first year after treatment. The secondary endpoint was control of infection, defined as a marked reduction of the infected area.

RESULTS

After a median treatment time of 3 weeks, an immediate response was observed in all patients, and complete healing was achieved in 6 patients. Five patients met the primary endpoint, and infection did not recur after a median follow-up of 17.5 (range, 12.1 to 21.8) months. One patient underwent heart transplantation 6 months after successful wound treatment (complete wound healing). The remaining 3 patients were discharged with controlled infection. After a median follow-up of 5.7 months, 1 destination therapy patient died at home, and 2 patients underwent urgent heart transplantation because of recurrence of infection caused by Pseudomonas aeruginosa. Side effects were not observed.

CONCLUSIONS

The new combination treatment offers a promising option for patients with ventricular assist device-relapsed infection. Despite this, further studies are warranted to confirm those encouraging preliminary results.

Impaired Neovascularization in Aging

Significance: The skin undergoes an inevitable degeneration as an individual ages. As intrinsic and extrinsic factors degrade the structural integrity of the skin, it experiences a critical loss of function and homeostatic stability. Thus, aged skin becomes increasingly susceptible to injury and displays a prolonged healing process. Recent Advances: Several studies have found significant differences during wound healing between younger and older individuals. The hypoxia-inducible factor 1-alpha (HIF-1α) signaling pathway has recently been identified as a major player in wound healing. Hypoxia-inducible factors (HIFs) are pleiotropic key regulators of oxygen homeostasis. HIF-1α is essential to neovascularization through its regulation of cytokines, such as SDF-1α (stromal cell-derived factor 1-alpha) and has been shown to upregulate the expression of genes important for a hypoxic response. Prolyl hydroxylase domain proteins (PHDs) and factor inhibiting HIF effectively block HIF-1α signaling in normoxia through hydroxylation, preventing the signaling cascade from activating, leading to impaired tissue survival. Critical Issues: Aged wounds are a major clinical burden, resisting modern treatment and costing millions in health care each year. At the molecular level, aging has been shown to interfere with PHD regulation, which in turn prevents HIF-1α from activating gene expression, ultimately leading to impaired healing. Other studies have identified loss of function in cells during aging, impeding processes such as angiogenesis. Future Directions: An improved understanding of the regulation of molecular mediators, such as HIF-1α and PHD, will allow for manipulation of the various factors underlying delayed wound healing in the aged. The findings highlighted in this may facilitate the development of potential therapeutic approaches involved in the alteration of cellular dynamics and aging.

Regulation and function of IL-22 in peritoneal adhesion formation after abdominal surgery

Peritoneal adhesion occurs frequently after gastrointestinal/gynecological surgery. Tissue repair and regeneration are very important during this process. IL-22 is an important cytokine that is secreted from immune cells but functions on mesenchymal cells, such as mesothelial cells. The objective of this study was to investigate the roles of IL-22 and its regulators during adhesion formation. Postsurgical peritoneal drainage fluid from patients and rodent models was examined by enzyme-linked immunosorbent assay and fluorescence-activated cell sorting. It was observed that IL-22 expression in the abdominal cavity was rapidly induced 12 hours after surgery and then slowly decreased to a lower, steady level for up to 7 days after surgery. However, neutralizing IL-22 at the time point at which the highest level of expression was observed failed to reduce adhesion, but neutralizing IL-22 at a later time point, i.e., 3 days after surgery, prevented adhesion significantly. The IL-22 receptor was induced on the mesothelial membrane, and IL-22BP, an inhibitor of IL-22, was reduced 3 days after surgery. Furthermore, IFN-γ was identified to have the ability to induce IL-22R, and IL-18, which was induced by the infiltrating macrophages, was found to inhibit IL-22BP expression both in vivo and in vitro. Together, these data suggest that IL-22 may promote adhesion formation and that the regulation of IL-22, IL-22R, and IL-22BP may have therapeutic potential to prevent adhesion formation after surgery without disturbing the normal immune process.

Prospective application of exosomes derived from adipose-derived stem cells in skin wound healing: A review

BACKGROUND

Wound healing has always been an intractable medical problem for both clinicians and researchers and a burden for patients both physically and financially. Poor wound healing at the injury site, especially in an exposed site, is associated with an unappealing esthetic appearance in patients and also results in a bad skin barrier, tissue infection and necrosis, loss of main function in extreme cases and other serious local and systemic consequences. There is a crucial and urgent need for newer, more efficacious methods for enhancing the healing process to achieve optimal outcomes morphologically and functionally. Recent advances have focused on developing therapies that promote tissue regeneration through positively activating the mechanism of tissue repair. Given the increasing high-quality studies concerning exosomes derived from adipose-derived stem cells (ADSCs-Exos), their potential use in accelerating or supporting the wound healing process has gained increasing attention in recent years.

AIMS

In this review, we present an overview of the recent advances in the field of ADSCs-Exos and investigate their benefit in wound healing for skin regeneration with the expectation of providing a perspective on how to best utilize this powerful cell-free therapy in the future.

METHODS

A retrospective review of the published data was conducted.

RESULTS

Most studies have shown the possible roles of ASCs-derived exosomes (ADSCs-Exos) in cutaneous wound healing through regulation of the inflammatory response and promotion of cell proliferation, migration, differentiation, angiogenesis and matrix reconstruction to provide a new perspective strategy for the use of ASCs-Exos in skin wound healing.

CONCLUSION

ADSCs-Exos are likely to achieve the best functionally and cosmetic skin wound healing while avoiding undesirable consequences. ADSCs-Exos represent a novel therapeutic tool in soft tissue repair; however, further randomized, double-blind, comparative clinical trials must be performed to determine the specific mechanisms, safety and other relevant cosmetic concerns.

Current management and perspectives in the treatment of ventricular assist device-specific infections

Occurrence of ventricular assist device (VAD)-specific infections is a serious complication that can jeopardize on the long run the effectiveness of VAD therapy. In the light of ongoing shortage of organ available for heart transplantation there will be in the next future an increase necessity of conservative strategies. A multidisciplinary approach including cardiac surgeons, cardiologist, infectious disease (ID) consultant and nuclear medicine physicians should be the first step for the diagnosis and treatment of VAD-specific infections. Early detection of infections and consequently early treatment with innovative strategies may help physicians to improve outcomes.

Preoperative Planning and Patient Optimization

This article reviews the literature that supports routine expectations for smoking cessation; weight loss; diabetic, nutritional, or metabolic optimization; and decolonization techniques before ventral hernia repair. These methods diminish postoperative complications. In an era of value-centric care, an upfront investment in patient optimization can improve the quality of the repair by reducing wound morbidity and hernia recurrence, naturally translating to a reduction in cost. The adoption of these practices and further study aimed at identifying other effective optimization techniques are encouraged.

Evaluating a novel oxygenating therapeutic for its potential use in the advancement of wound healing

Non-gaseous oxygen therapeutics are emerging technologies in regenerative medicine that aim to sidestep the undesirable effects seen in traditional oxygen therapies, while enhancing tissue and wound regeneration. Using a novel oxygenating therapeutic (Ox66™) several in vitro models including fibroblast and keratinocyte monocultures were evaluated for potential drug toxicity, the ability of cells to recover after chemical injury, and cell migration after scratch assay. It was determined that in both cell lines, there was no significant cytotoxicity found after independent treatment with Ox66™. Similarly, after DMSO-induced chemical injury, the health parameters of cells treated with Ox66™ were improved when compared to their untreated counterparts. Particles were also characterized using scanning electron microscopy and electron dispersive spectroscopy both individually and in conjunction with fibroblast growth. The data in this study showed that the novel wound healing therapeutic has potential in advancing the treatment of various types of acute and chronic wounds.

Wound bed preparation: TIME for an update

While the overwhelming majority of wounds heal rapidly, a significant proportion fail to progress through the wound-healing process. These resultant chronic wounds cause considerable morbidity and are costly to treat. Wound bed preparation, summarised by the TIME (Tissue, Inflammation/infection, Moisture imbalance, Epithelial edge advancement) concept, is a systematic approach for assessing chronic wounds. Each of these components needs to be addressed and optimised to improve the chances of successful wound closure. We present an up-to-date literature review of the most important recent aspects of wound bed preparation. While there are many novel therapies that are available to the treating clinician, often, there are limited data on which to assess their clinical value, and a lack of appreciation for adequate wound bed preparation needed before expensive therapy is used to heal a wound.

Randomized, controlled study of innovative spray formulation containing ozonated oil and α-bisabolol in the topical treatment of chronic venous leg ulcers

OBJECTIVE

Ozone therapy has a large clinical application in many therapeutic areas because of its well-known antimicrobial, immunological, and oxygenating properties. Recently, interest has grown regarding the application of ozonated oil for vascular leg ulcer treatment. The efficacy of an innovative spray formulation of ozonated oil and α-bisabolol combination in the topical treatment of chronic venous leg ulcers was evaluated compared with standard epithelialization cream.

DESIGN

A randomized controlled trial was conducted.

SETTING

A total of 29 patients older than 18 years with chronic venous leg ulcers for less than 2 years' duration were assessed.

PATIENTS

Patients were randomized to receive daily application of both ozonated oil and α-bisabolol or the control cream (vitamin A, vitamin E, talc, and zinc oxide) for 30 days.

MAIN OUTCOME MEASURES

Patients were evaluated on 4 different visits: at days 0, 7, 14, and 30. At each visit, the wound surfaces were measured. Wound area ratio and the speed of ulcer healing were calculated.

MAIN RESULTS

At the end of treatment, the proportion of patients with complete ulcer healing was higher with ozonated oil and α-bisabolol formulation (25% vs 0%). Furthermore, the changes in ulcer surface area were significant for ozonated oil and α-bisabolol formulation only (P < .05), in particular, observing a significant and progressive reduction of the wound surface by 34%, 59%, and 73%, after 7, 14, and 30 days of treatment, respectively.

CONCLUSION

The innovative spray formulation of ozonated oil and α-bisabolol combination shows promise as an important new therapeutic option in the adjuvant treatment of venous ulcers.

Advanced Therapeutic Dressings for Effective Wound Healing--A Review

Advanced therapeutic dressings that take active part in wound healing to achieve rapid and complete healing of chronic wounds is of current research interest. There is a desire for novel strategies to achieve expeditious wound healing because of the enormous financial burden worldwide. This paper reviews the current state of wound healing and wound management products, with emphasis on the demand for more advanced forms of wound therapy and some of the current challenges and driving forces behind this demand. The paper reviews information mainly from peer-reviewed literature and other publicly available sources such as the US FDA. A major focus is the treatment of chronic wounds including amputations, diabetic and leg ulcers, pressure sores, and surgical and traumatic wounds (e.g., accidents and burns) where patient immunity is low and the risk of infections and complications are high. The main dressings include medicated moist dressings, tissue-engineered substitutes, biomaterials-based biological dressings, biological and naturally derived dressings, medicated sutures, and various combinations of the above classes. Finally, the review briefly discusses possible prospects of advanced wound healing including some of the emerging physical approaches such as hyperbaric oxygen, negative pressure wound therapy and laser wound healing, in routine clinical care.

Managing infection: a holistic approach

All wound infection presents risks for the patient, but the risks are multiplied in the presence of a comorbidity such as diabetes, when they can potentially be fatal. Where diabetic foot ulcer (DFU) infection is concerned, early recognition is crucial. Prompt treatment, comprising wound cleansing, debridement of devitalised tissue and use of antimicrobial dressings, can stop locally infected ulcers from deteriorating further.

Effect of postoperative use of nasal oxygen catheter supplementation in wound healing following total knee arthroplasty

OBJECTIVES

Healing is an event that is fundamental to the success of total knee arthroplasty. The aims of the present study were to compare the rates of complications related to wound healing between two groups of volunteers submitted to total knee arthroplasty and to evaluate the effects of postoperative oxygen supplementation by means of a nasal catheter.

METHOD

A total of 109 patients who underwent total knee arthroplasty were randomized into two groups, namely, groups that did and did not receive postoperative oxygen supplementation via a nasal catheter. The surgical wound was monitored every day during the hospital stay and on the 7th, 14th, 21st, 30th and 42nd postoperative days. Characteristics related to healing were observed, including hyperemia, dehiscence, necrosis, phlyctenules and deep and superficial infection.

RESULTS

There were no cases of deep infection. Hyperemia was statistically correlated with the total number of complications in the groups, with oxygen demonstrated to be a protective factor against hyperemia. Approximately 30% of the patients who exhibited hyperemia had other complications, independent of oxygen supplementation.

CONCLUSION

Oxygen supplementation following total knee arthroplasty was shown to be effective in diminishing hyperemia around the operative wound. The development of hyperemia was a precursor to other complications, irrespective of whether oxygen supplementation was used.

Influence of oxygen on wound healing

Oxygen has an important role in normal wound healing. This article reviews the evidence concerning the role of oxygen in wound healing and its influence on the different stages of wound healing. The evidence reviewed has demonstrated that improving oxygenation may be helpful in limiting wound infection, although there is a lack of good quality studies on the role of oxygen in the proliferative phase and in reepithelialisation. Overall, the relationship between oxygen and wound healing is complex. Knowledge of this aspect is important as many treatment modalities for refractory wounds are based on these principles.

The Role of Hypoxia-Inducible Factor in Wound Healing

Significance: Poor wound healing remains a significant health issue for a large number of patients in the United States. The physiologic response to local wound hypoxia plays a critical role in determining the success of the normal healing process. Hypoxia-inducible factor-1 (HIF-1), as the master regulator of oxygen homeostasis, is an important determinant of healing outcomes. HIF-1 contributes to all stages of wound healing through its role in cell migration, cell survival under hypoxic conditions, cell division, growth factor release, and matrix synthesis throughout the healing process. Recent Advances: Positive regulators of HIF-1, such as prolyl-4-hydroxylase inhibitors, have been shown to be beneficial in enhancing diabetic ischemic wound closure and are currently undergoing clinical trials for treatment of several human-ischemia-based conditions. Critical Issues: HIF-1 deficiency and subsequent failure to respond to hypoxic stimuli leads to chronic hypoxia, which has been shown to contribute to the formation of nonhealing ulcers. In contrast, overexpression of HIF-1 has been implicated in fibrotic disease through its role in increasing myofibroblast differentiation leading to excessive matrix production and deposition. Both positive and negative regulators of HIF-1 therefore provide important therapeutic targets that can be used to manipulate HIF-1 expression where an excess or deficiency in HIF-1 is known to correlate with pathogenesis. Future Directions: Targeting HIF-1 during wound healing has many important clinical implications for tissue repair. Counteracting the detrimental effects of excessive or deficient HIF-1 signaling by modulating HIF-1 expression may improve future management of poorly healing wounds.

Extending the TIME concept: what have we learned in the past 10 years?(*)

The TIME acronym (tissue, infection/inflammation, moisture balance and edge of wound) was first developed more than 10 years ago, by an international group of wound healing experts, to provide a framework for a structured approach to wound bed preparation; a basis for optimising the management of open chronic wounds healing by secondary intention. However, it should be recognised that the TIME principles are only a part of the systematic and holistic evaluation of each patient at every wound assessment. This review, prepared by the International Wound Infection Institute, examines how new data and evidence generated in the intervening decade affects the original concepts of TIME, and how it is translated into current best practice. Four developments stand out: recognition of the importance of biofilms (and the need for a simple diagnostic), use of negative pressure wound therapy (NPWT), evolution of topical antiseptic therapy as dressings and for wound lavage (notably, silver and polyhexamethylene biguanide) and expanded insight of the role of molecular biological processes in chronic wounds (with emerging diagnostics and theranostics). Tissue: a major advance has been the recognition of the value of repetitive and maintenance debridement and wound cleansing, both in time-honoured and novel methods (notably using NPWT and hydrosurgery). Infection/inflammation: clinical recognition of infection (and non infective causes of persisting inflammation) is critical. The concept of a bacterial continuum through contamination, colonisation and infection is now widely accepted, together with the understanding of biofilm presence. There has been a return to topical antiseptics to control bioburden in wounds, emphasised by the awareness of increasing antibiotic resistance. Moisture: the relevance of excessive or insufficient wound exudate and its molecular components has led to the development and use of a wide range of dressings to regulate moisture balance, and to protect peri-wound skin, and optimise healing. Edge of wound: several treatment modalities are being investigated and introduced to improve epithelial advancement, which can be regarded as the clearest sign of wound healing. The TIME principle remains relevant 10 years on, with continuing important developments that incorporate new evidence for wound care.

Brief review: theory and practice of minimal fresh gas flow anesthesia

PURPOSE

The aim of this brief review is to provide an update on the theory regarding minimal fresh gas flow techniques for inhaled general anesthesia. The article also includes an update and discussion of the practical aspects associated with minimal-flow anesthesia, including the advantages, potential limitations, and safety considerations of this important anesthetic technique.

PRINCIPAL FINDINGS

Reducing the fresh gas flow to < 1 L·min(-1) during maintenance of anesthesia is associated with several benefits. Enhanced preservation of temperature and humidity, cost savings through more efficient utilization of inhaled anesthetics, and environmental considerations are three key reasons to implement minimal-flow and closed-circuit anesthesia, although potential risks are hypoxic gas mixtures and inadequate depth of anesthesia. The basic elements of the related pharmacology need to be considered, especially pharmacokinetics of the inhaled anesthetics. The third-generation inhaled anesthetics, sevoflurane and desflurane, have low blood and low tissue solubility, which facilitates rapid equilibration between the alveolar and effect site (brain) concentrations and makes them ideally suited for low-flow techniques. The use of modern anesthetic machines designed for minimal-flow techniques, leak-free circle systems, highly efficient CO(2) absorbers, and the common practice of utilizing on-line real-time multi-gas monitor, including essential alarm systems, allow for safe and cost-effective minimal-flow techniques during maintenance of anesthesia. The introduction of new anesthetic machines with built-in closed-loop algorithms for the automatic control of inspired oxygen and end-tidal anesthetic concentration will further enhance the feasibility of minimal-flow techniques.

CONCLUSIONS

With our modern anesthesia machines, reducing the fresh gas flow of oxygen to 0.3-0.5 L·min(-1) and using third-generation inhaled anesthetics provide a reassuringly safe anesthetic technique. This environmentally friendly practice can easily be implemented for elective anesthesia; furthermore, it will facilitate cost savings and improve temperature homeostasis.

Clinical results of the application of a hemoglobin spray to promote healing of chronic wounds

A new technological approach for supplying hypoxic chronic wounds with oxygen is a moist wound treatment with aqueous solutions containing tissue compatible oxygen binders. This facilitates diffusion of oxygen, necessary for the healing process, from the surroundings (room air through an open-porous wound padding) into the ulcerous tissue. A product that is still in development is a spray which contains hemoglobin obtained from domestic pigs.

Clinical investigations (a clinical trial, treatment observations and single patient uses) are presented, which were performed to create clinical data regarding efficiency and safety of this product. All data have shown that the application of the hemoglobin spray promoted wound healing in all analyzed cases.

Data from a clinical study in Mexico and subsequent therapy observations revealed that in 39 out of 42 patients (93%) the treated wounds were healed. 9 patients from a series of therapy observations in Monterrey (Mexico) showed similar observations. All treated wounds were closed. Single patient uses carried out in Witten (Germany; 6 wounds from 8 (75%)) and Prague (Czech Republic; 5 wounds from 5 (100%) were healed) further support these results: The application of hemoglobin spray can promote healing of chronic wounds.

Within the framework of the clinical investigation, the treatment observations, and the individual healing experiments the hemoglobin spray was applied more than 2,000 times onto chronic wounds of 82 patients. In all cases, the spray was well tolerated and there were no adverse event that might have been an adverse reaction to the hemoglobin spray.