Wound hypoxia and acidosis limit neutrophil bacterial killing mechanisms

Perioperative Hypothermia-A Narrative Review

Unintentional hypothermia (core temperature < 36 °C) is a common side effect in patients undergoing surgery. Several patient-centred and external factors, e.g., drugs, comorbidities, trauma, environmental temperature, type of anaesthesia, as well as extent and duration of surgery, influence core temperature. Perioperative hypothermia has negative effects on coagulation, blood loss and transfusion requirements, metabolization of drugs, surgical site infections, and discharge from the post-anaesthesia care unit. Therefore, active temperature management is required in the pre-, intra-, and postoperative period to diminish the risks of perioperative hypothermia. Temperature measurement should be done with accurate and continuous probes. Perioperative temperature management includes a bundle of warming tools adapted to individual needs and local circumstances. Warming blankets and mattresses as well as the administration of properly warmed infusions via dedicated devices are important for this purpose. Temperature management should follow checklists and be individualized to the patient's requirements and the local possibilities.

Molecular Biomarkers of Oxygen Therapy in Patients with Diabetic Foot Ulcers

Hyperbaric oxygen therapy (HBOT) and topical oxygen therapy (TOT) including continuous diffuse oxygen therapy (CDOT) are often utilized to enhance wound healing in patients with diabetic foot ulcerations. High pressure pure oxygen assists in the oxygenation of hypoxic wounds to increase perfusion. Although oxygen therapy provides wound healing benefits to some patients with diabetic foot ulcers, it is currently performed from clinical examination and imaging. Data suggest that oxygen therapy promotes wound healing via angiogenesis, the creation of new blood vessels. Molecular biomarkers relating to tissue inflammation, repair, and healing have been identified. Predictive biomarkers can be used to identify patients who will most likely benefit from this specialized treatment. In diabetic foot ulcerations, specifically, certain biomarkers have been linked to factors involving angiogenesis and inflammation, two crucial aspects of wound healing. In this review, the mechanism of how oxygen works in wound healing on a physiological basis, such as cell metabolism and growth factor signaling transduction is detailed. Additionally, observable clinical outcomes such as collagen formation, angiogenesis, respiratory burst and cell proliferation are described. The scientific evidence for the impact of oxygen on biomolecular pathways and its relationship to the outcomes in clinical research is discussed in this narrative review.

Enhanced Skin Incisional Wound Healing With Intracellular ATP Delivery via Macrophage Proliferation and Direct Collagen Production

This study sought to use a newly developed intracellular ATP delivery to enhance incisional wound healing to reduce surgical wound dehiscence and to explore possible mechanism for this effect. Thirty-five adult New Zealand white rabbits were used. Skin incisions were made on the back and closed. ATP-vesicles were mixed with a neutral cream for one side of the wounds while the neutral cream alone was used on the other side of the wounds. Laser speckle contrast imaging (LSCI), biomechanical, histological, and immunohistochemical analyses were performed 7 and 14 days after surgery, and macrophage culture was used to test the enhanced collagen production ability. Among them, 10 were used for wound perfusion study and 25 were used for wound biomechanical and histological/immunohistochemical studies. Wound tissue perfusion was reduced after surgery especially in early days. Wound tissue tensile strength, breaking stress, and elasticity were all much higher in the ATP-vesicle treated group than in the cream treated group at days 7 and 14. The healing was complemented by earlier macrophage accumulation, in situ proliferation, followed by direct collagen production. The results were further confirmed by human macrophage culture. It was concluded that intracellular ATP delivery enhanced healing strength of incisional wounds via multiple mechanisms.

Perioperative Lung Protection: Clinical Implications

In the past, it was common practice to use a high tidal volume (VT) during intraoperative ventilation, because this reduced the need for high oxygen fractions to compensate for the ventilation-perfusion mismatches due to atelectasis in a time when it was uncommon to use positive end-expiratory pressure (PEEP) in the operating room. Convincing and increasing evidence for harm induced by ventilation with a high VT has emerged over recent decades, also in the operating room, and by now intraoperative ventilation with a low VT is a well-adopted approach. There is less certainty about the level of PEEP during intraoperative ventilation. Evidence for benefit and harm of higher PEEP during intraoperative ventilation is at least contradicting. While some PEEP may prevent lung injury through reduction of atelectasis, higher PEEP is undeniably associated with an increased risk of intraoperative hypotension that frequently requires administration of vasoactive drugs. The optimal level of inspired oxygen fraction (FIO2) during surgery is even more uncertain. The suggestion that hyperoxemia prevents against surgical site infections has not been confirmed in recent research. In addition, gas absorption-induced atelectasis and its association with adverse outcomes like postoperative pulmonary complications actually makes use of a high FIO2 less attractive. Based on the available evidence, we recommend the use of a low VT of 6-8 mL/kg predicted body weight in all surgery patients, and to restrict use of a high PEEP and high FIO2 during intraoperative ventilation to cases in which hypoxemia develops. Here, we prefer to first increase FIO2 before using high PEEP.

Aseptic Reoperations Within 1 Year of Primary Total Knee Arthroplasty Markedly Increase the Risk of Later Periprosthetic Joint Infection

BACKGROUND

Despite the high rate of success of primary total knee arthroplasty (TKA), some patients are candidates for early aseptic reoperation. The goal of this study is to evaluate the risk of subsequent periprosthetic joint infection (PJI) in patients treated with an aseptic reoperation within 1 year of primary TKA.

METHODS

A retrospective review of our total joint registry compared 249 primary TKAs requiring an aseptic reoperation within 1 year following index arthroplasty to a control group of 17,867 TKAs not requiring reoperation within 1 year. Patients were divided into groups based on time from index TKA: (1) 90 days or less (114 TKAs) and (2) 91 to 365 days (135 TKAs). Mean age was 68 years with 57% female. Mean follow-up was 7 years.

RESULTS

At 2 years postoperatively, patients undergoing an aseptic reoperation within 90 days subsequently had a 9% PJI rate, while patients undergoing an aseptic reoperation between 91 and 365 days subsequently had a 3% PJI rate. The control group had a 0.4% PJI rate. Compared to the control group, patients undergoing an aseptic reoperation within 90 days had an elevated risk of PJI (hazard ratio, 9; P < .0001), as did patients who had a reoperation between 91 and 365 days (hazard ratio, 4; P < .0001).

CONCLUSION

Aseptic reoperation within 1 year of primary TKA was associated with a notably increased risk of subsequent PJI.

Effects of intraoperative high versus low inspiratory oxygen fraction (FiO2) on patient's outcome: A systematic review of evidence from the last 20 years

Despite numerous studies, controversies about the best intraoperative FiO2 remain. In 2016, the World Health Organization (WHO) recommended that adult patients undergoing general anaesthesia should be ventilated intraoperatively with an 80% FiO2 to reduce surgical site infection (SSI). However, several data suggest that hyperoxia could have adverse effects. In order to determine the potential effect of FiO2 on SSI, we included in this systematic review 23 studies (among which 21 randomised controlled trials [RCT]) published between 1999 and 2020, comparing intraoperative high versus low FiO2. Results were heterogeneous but most recent studies on one hand, and the largest RCTs on the other hand, reported no difference on the incidence of SSI regarding intraoperative FiO2 during general anaesthesia. There was also no difference in the incidence of SSI depending of intraoperative FiO2 in patients receiving regional anaesthesia. The review on secondary endpoints (respiratory and cardiovascular adverse events, postoperative nausea and vomiting, postoperative length-of-stay and mortality) also failed to support the use of high FiO2. On the opposite, some data from follow-up analyses and registry studies suggested a possible negative effect of high intraoperative FiO2 on long-term outcomes. In conclusion, the systematic administration of a high intraoperative FiO2 in order to decrease SSI or improve other perioperative outcomes seems unjustified in the light of the evidence currently available in the literature.

The effect of conservative oxygen therapy on systemic biomarkers of oxidative stress in critically ill patients

BACKGROUND

Supplemental oxygen is delivered to critically ill patients who require mechanical ventilation. Oxidative stress is a potential complication of oxygen therapy, resulting in damage to essential biomolecules such as proteins, lipids, and nucleic acids. Whether plasma levels of oxidative stress biomarkers vary based on how liberally oxygen therapy is applied during mechanical ventilation is unknown.

METHODS

We carried out an oxidative stress substudy nested within a large multi-centre randomized controlled trial in which critically ill adults were randomized to receive either conservative oxygen therapy or standard oxygen therapy. Blood samples were collected at enrolment, and daily thereafter for up to three days. The antioxidant ascorbate (vitamin C) was assessed using HPLC with electrochemical detection and protein oxidation using a sensitive protein carbonyl ELISA. We also assessed whether critically ill patients with different disease states exhibited varying levels of oxidative stress biomarkers.

RESULTS

A total of 125 patients were included. Mean ascorbate concentrations decreased over time (from 25 ± 9 μmol/L to 14 ± 2 μmol/L, p < 0.001), however, there was no significant difference between the conservative oxygen group and standard care (p = 0.2), despite a significantly lower partial pressure of oxygen (PaO₂) in the conservative oxygen group (p = 0.03). Protein carbonyl concentrations increased over time (from 208 ± 30 μmol/L to 249 ± 29 μmol/L; p = 0.016), however, there was no significant difference between the conservative and standard oxygen groups (p = 0.3). Patients with sepsis had significantly higher protein carbonyl concentrations than the other critically ill patients (293 ± 92 μmol/L vs 184 ± 24 μmol/L, p = 0.03). Within the septic subgroup, there were no significant differences in protein carbonyl concentrations between the two interventions (p = 0.4).

CONCLUSIONS

Conservative oxygen therapy does not alter systemic markers of oxidative stress in critically ill ventilated patients compared with standard oxygen therapy. Patients with sepsis exhibited elevated protein carbonyls compared with the other critically ill patients implying increased oxidative stress in this patient subgroup.

An Overview of Biopolymeric Electrospun Nanofibers Based on Polysaccharides for Wound Healing Management

Currently, despite the thoroughgoing scientific research carried out in the area of wound healing management, the treatment of skin injuries, regardless of etiology remains a big provocation for health care professionals. An optimal wound dressing should be nontoxic, non-adherent, non-allergenic, should also maintain a humid medium at the wound interfacing, and be easily removed without trauma. For the development of functional and bioactive dressings, they must meet different conditions such as: The ability to remove excess exudates, to allow gaseous interchange, to behave as a barrier to microbes and to external physical or chemical aggressions, and at the same time to have the capacity of promoting the process of healing by stimulating other intricate processes such as differentiation, cell adhesion, and proliferation. Over the past several years, various types of wound dressings including hydrogels, hydrocolloids, films, foams, sponges, and micro/nanofibers have been formulated, and among them, the electrospun nanofibrous mats received an increased interest from researchers due to the numerous advantages and their intrinsic properties. The drug-embedded nanofibers are the potential candidates for wound dressing application by virtue of: Superior surface area-to volume ratio, enormous porosity (can allow oxy-permeability) or reticular nano-porosity (can inhibit the microorganisms'adhesion), structural similitude to the skin extracellular matrix, and progressive electrospinning methodology, which promotes a prolonged drug release. The reason that we chose to review the formulation of electrospun nanofibers based on polysaccharides as dressings useful in wound healing was based on the ever-growing research in this field, research that highlighted many advantages of the nanofibrillary network, but also a marked versatility in terms of numerous active substances that can be incorporated for rapid and infection-free tissue regeneration. In this review, we have extensively discussed the recent advancements performed on electrospun nanofibers (eNFs) formulation methodology as wound dressings, and we focused as well on the entrapment of different active biomolecules that have been incorporated on polysaccharides-based nanofibers, highlighting those bioagents capable of improving the healing process. In addition, in vivo tests performed to support their increased efficacy were also listed, and the advantages of the polysaccharide nanofiber-based wound dressings compared to the traditional ones were emphasized.

Oxygen administration for postoperative surgical patients: a narrative review

Most postoperative surgical patients routinely receive supplemental oxygen therapy to prevent the potential development of hypoxemia due to incomplete lung re-expansion, reduced chest wall, and diaphragmatic activity caused by surgical site pain, consequences of hemodynamic impairment, and residual effects of anesthetic drugs (most notably residual neuromuscular blockade), which may result in atelectasis, ventilation–perfusion mismatch, alveolar hypoventilation, and impaired upper airway patency. Additionally, the World Health Organization guidelines for reducing surgical site infection have recommended the perioperative administration of high-dose oxygen, including during the immediate postoperative period. However, supplemental oxygen and hyperoxemia also have harmful effects on the respiratory and cardiovascular systems, with several clinical studies having reported an association between high perioperative oxygen administration and worse clinical outcomes. Recently, the increased availability of new and short-acting anesthetic drugs, comprehensive pharmacological knowledge, postoperative multimodal analgesia, and new minimally invasive surgery options could result in lower incidences of postoperative hypoxemia. Moreover, recommendations promoting high oxygen administration to prevent surgical site infections have been challenged, considering the lack of scientific investigations, and have not been widely accepted. Given the potential harmful effects of hyperoxemia, routine postoperative oxygen administration might not be recommended. Recent clinical studies have indicated that a conservative approach to oxygen therapy, where oxygen administration is titrated to achieve slightly lower oxygen levels than usual, could be safely implemented and decrease acutely ill patients’ susceptibility to hyperoxemia. Based on current evidence, appropriate monitoring, including peripheral oxygen saturation, and oxygen titration should be required during postoperative oxygen administration to avoid both hypoxemia and hyperoxemia. Future trials should therefore focus on determining the optimal oxygen target during postoperative care.

Perioperative and anesthetic risk factors of surgical site infection in patients undergoing pancreaticoduodenectomy: A retrospective cohort study

Background

Surgical site infection is a major perioperative issue. The morbidity of surgical site infection is high in major digestive surgery, such as pancreaticoduodenectomy. The comprehensive risk factors, including anesthetic factors, for surgical site infection in pancreaticoduodenectomy are unknown. The aim of this study was to investigate the perioperative and anesthetic risk factors of surgical site infection in pancreaticoduodenectomy.

Methods

This was a retrospective cohort study conducted in a single tertiary care center. A total of 326 consecutive patients who underwent pancreaticoduodenectomy between January 2009 and March 2018 were evaluated. Patients who underwent resection of other organs were excluded. The primary outcome was the incidence of surgical site infection, based on a Clavien-Dindo classification of grade 2 or higher. Multivariable logistic regression analysis was performed to investigate the association between surgical site infection and perioperative and anesthetic factors.

Results

Of the 326 patients, 116 (35.6%) were women. The median age was 70 years (interquartile range; 64–75). The median duration of surgery was 10.9 hours (interquartile range; 9.5–12.4). Surgical site infection occurred in 60 patients (18.4%). The multivariable analysis revealed that the use of desflurane as a maintenance anesthetic was associated with a significantly lower risk of surgical site infection than sevoflurane (odds ratio, 0.503; 95% confidence interval [CI], 0.260–0.973). In contrast, the duration of surgery (odds ratio, 1.162; 95% CI, 1.017–1.328), cerebrovascular disease (odds ratio, 3.544; 95% CI, 1.326–9.469), and ischemic heart disease (odds ratio, 10.839; 95% CI, 1.887–62.249) were identified as significant risk factors of surgical site infection.

Conclusions

Desflurane may be better than sevoflurane in preventing surgical site infection in pancreaticoduodenectomy. Cerebrovascular disease and ischemic heart disease are potential newly-identified risk factors of surgical site infection in pancreaticoduodenectomy.

Systematic review of the efficacy of topical haemoglobin therapy for wound healing

Hypoxia is a common cause of poor wound healing, for which a variety of oxygen therapies have been developed. In order to overcome the limitations of traditional methods of treatment, namely the type of equipment, its setting, safety and cost, local haemoglobin therapy has been developed, although no reviews have so far been published. Here, we systematically review the current evidence to establish the efficacy, scope, adverse reactions, and required precautions of this new form of therapy. A search of the literature was conducted in the PubMed, Embase, Scopus, CENTRAL, CINAHL, and Web of science databases, with 17 studies meeting the eligibility criteria, comprising one animal model study and 16 clinical studies. Local haemoglobin therapy is able to safely and effectively promote the healing of a variety of wounds, especially those that are chronic and non-healing. However, premature discontinuation of this treatment can result in impediment to wound healing and even deterioration of the wound. The distinct benefit of the elimination of slough and relief of pain suggests that this technique may represent a new generation of debridement technology. Furthermore, its ease of use and convenience enables patient self-management, thereby greatly reducing health care costs.

Personalised haemodynamic management targeting baseline cardiac index in high-risk patients undergoing major abdominal surgery: a randomised single-centre clinical trial

BACKGROUND

Despite several clinical trials on haemodynamic therapy, the optimal intraoperative haemodynamic management for high-risk patients undergoing major abdominal surgery remains unclear. We tested the hypothesis that personalised haemodynamic management targeting each individual's baseline cardiac index at rest reduces postoperative morbidity.

METHODS

In this single-centre trial, 188 high-risk patients undergoing major abdominal surgery were randomised to either routine management or personalised haemodynamic management requiring clinicians to maintain personal baseline cardiac index (determined at rest preoperatively) using an algorithm that guided intraoperative i.v. fluid and/or dobutamine administration. The primary outcome was a composite of major complications (European Perioperative Clinical Outcome definitions) or death within 30 days of surgery. Secondary outcomes included postoperative morbidity (assessed by a postoperative morbidity survey), hospital length of stay, mortality within 90 days of surgery, and neurocognitive function assessed after postoperative Day 3.

RESULTS

The primary outcome occurred in 29.8% (28/94) of patients in the personalised management group, compared with 55.3% (52/94) of patients in the routine management group (relative risk: 0.54, 95% confidence interval [CI]: 0.38 to 0.77; absolute risk reduction: -25.5%, 95% CI: -39.2% to -11.9%; P<0.001). One patient assigned to the personalised management group, compared with five assigned to the routine management group, died within 30 days after surgery (P=0.097). There were no clinically relevant differences between the two groups for secondary outcomes.

CONCLUSIONS

In high-risk patients undergoing major abdominal surgery, personalised haemodynamic management reduces a composite outcome of major postoperative complications or death within 30 days after surgery compared with routine care.

CLINICAL TRIAL REGISTRATION

NCT02834377.

The Lawrence D. Dorr Surgical Techniques & Technologies Award: Aseptic Reoperations Within One Year of Primary Total Hip Arthroplasty Markedly Increase the Risk of Later Periprosthetic Joint Infection

BACKGROUND

Despite the success of primary total hip arthroplasties (THAs), some patients will require an aseptic reoperation within 1 year of the index THA. The goal of this study is to evaluate the risk of subsequent periprosthetic joint infection (PJI) in patients undergoing an aseptic reoperation within 1 year of a primary THA.

METHODS

A retrospective review utilizing our institutional joint registry identified 211 primary THAs requiring aseptic reoperation within 1 year following index arthroplasty. A control group of 15,357 primary THAs not requiring reoperation within 1 year was identified. Patients were divided into groups based on time from primary THA to reoperation: (1) within 90 days (n = 112 THAs; 40% for dislocation, 34% for periprosthetic fracture) or (2) 91-365 days (n = 99 THAs; 37% for dislocation, 29% for periprosthetic fracture). Mean follow-up was 7 years.

RESULTS

Patients undergoing an aseptic reoperation within 90 days had a PJI rate of 4.8% at 2 years, while the 91-365 day group had a PJI rate of 3.2% at 2 years. The control group had a PJI rate of 0.2% at 2 years. Employing a multivariate analysis, reoperation within 90 days of index arthroplasty had an elevated risk of PJI (hazard ratio 8, P < .001) as did a reoperation between 91 and 365 days (hazard ratio 13, P < .001).

CONCLUSION

Aseptic reoperations within 1 year following primary THA resulted in an 8- to 13-fold increased risk of subsequent PJI. The risk was similar whether the aseptic reoperation was early (within 90 days) or later (91-365 days).

LEVEL OF EVIDENCE

Level III (Prognostic).

Role of oxygen in wound healing

Not only does oxygen play an essential role in each stage of the wound healing process. It also helps to increases host resistance to infection. Any impairment to the oxygen supply can therefore delay healing. This article explores the affects of oxygen on the wound cells and tissue, and explains how an adequate supply is required for granulation tissue formation and epithelialisation to occur

Stimuli-Responsive Delivery of Growth Factors for Tissue Engineering

Growth factors (GFs) play a crucial role in directing stem cell behavior and transmitting information between different cell populations for tissue regeneration. However, their utility as therapeutics is limited by their short half-life within the physiological microenvironment and significant side effects caused by off-target effects or improper dosage. "Smart" materials that can not only sustain therapeutic delivery over a treatment period but also facilitate on-demand release upon activation are attracting significant interest in the field of GF delivery for tissue engineering. Three properties are essential in engineering these "smart" materials: 1) the cargo vehicle protects the encapsulated therapeutic; 2) release is targeted to the site of injury; 3) cargo release can be modulated by disease-specific stimuli. The aim of this review is to summarize the current research on stimuli-responsive materials as intelligent vehicles for controlled GF delivery; Five main subfields of tissue engineering are discussed: skin, bone and cartilage, muscle, blood vessel, and nerve. Challenges in achieving such "smart" materials and perspectives on future applications of stimuli-responsive GF delivery for tissue regeneration are also discussed.

Current Strategies in Prevention of Postoperative Infections in Spine Surgery

STUDY DESIGN

Narrative review.

OBJECTIVES

Postoperative surgical site infections (SSIs) are among the most common acute complications in spine surgery and have a devastating impact on outcomes. They can lead to increased morbidity and mortality as well as greater economic burden. Hence, preventive strategies to reduce the rate of SSIs after spine surgery have become vitally important. The purpose of this article was to summarize and critically analyze the available evidence related to current strategies in the prevention of SSIs after spine surgery.

METHODS

A literature search utilizing Medline database was performed. Relevant studies from all the evidence levels have been included. Recommendations to decrease the risk of SSIs have been provided based on the results from studies with the highest level of evidence.

RESULTS

SSI prevention occurs at each phase of care including the preoperative, intraoperative, and postoperative periods. Meticulous patient selection, tight glycemic control in diabetics, smoking cessation, and screening/eradication of Staphylococcus aureus are some of the main preoperative patient-related preventive strategies. Currently used intraoperative measures include alcohol-based skin preparation, topical vancomycin powder, and betadine irrigation of the surgical site before closure. Postoperative infection prophylaxis can be performed by administration of silver-impregnated or vacuum dressings, extended intravenous antibiotics, and supplemental oxygen therapy.

CONCLUSIONS

Although preventive strategies are already in use alone or in combination, further high-level research is required to prove their efficacy in reducing the rate of SSIs in spine surgery before evidence-based standard infection prophylaxis guidelines can be built.

Association of Smoking and Other Factors With the Outcome of Mohs Reconstruction Using Flaps or Grafts

Importance

Smoking, a common lifestyle trait, is considered by many surgeons to be a major risk factor for postoperative complications. However, in the literature on local reconstruction, the association between smoking and the rate of postoperative complications after cutaneous tissue transfer is not well characterized.

Objective

To study the outcomes of flaps and grafts used in Mohs micrographic surgery reconstruction with respect to smoking status and patient-specific and surgery-specific variables.

Design, Setting, and Participants

This retrospective case-control study was conducted at a single tertiary referral center among 1008 patients who underwent Mohs reconstruction repaired by flap or graft between July 1, 2012, and June 30, 2016, and were selected via consecutive sampling. Cases with incomplete records or those in which a single flap or graft was used to repair multiple defects were excluded. Data analysis was performed from September 2017 to January 2018.

Main Outcomes and Measures

Postoperative acute and long-term complications. Acute complications included postsurgical infection, dehiscence, hematoma, uncontrolled bleeding, and tissue necrosis that required medical counseling or intervention. Long-term complications included functional or cosmetic outcomes that prompted the patient to request or the surgeon to offer additional intervention.

Results

Of the 1008 patients included in the study (396 women and 612 men), the median (SD) age was 70 (12) years (range, 21-90 years). A total of 128 patients (12.7%) were current smokers, 385 (38.2%) were former smokers, and 495 (49.1%) were never smokers. On multivariate logistic regression, current smoking (odds ratio [OR], 9.58; 95% CI, 3.63-25.3), former smoking (OR, 3.64; 95% CI, 1.41-9.38), larger defect size (OR, 2.25; 95% CI, 1.58-3.20), and the use of free cartilage graft (OR, 8.19; 95% CI, 2.02-33.1) were associated with increased risks of acute complications. For long-term complications, central face location (OR, 25.4; 95% CI, 6.16-106.5), use of interpolation flap or flap-graft combination (OR, 3.49; 95% CI, 1.81-6.74), larger flap size (OR, 1.42; 95% CI, 1.09-1.87), and basal cell carcinomas or other basaloid tumors (OR, 3.43; 95% CI, 1.03-11.5) were associated with an increased risk, whereas increased age (OR, 0.66 per 10-year interval; 95% CI, 0.54-0.80) was associated with decreased risk.

Conclusions and Relevance

This study suggests that both current and former smokers are at increased risk for acute postsurgical complications but that smoking status is not associated with long-term complications. These findings may allow the surgeon to better quantify the magnitude of risk and provide helpful information for patient counseling.

Level of Evidence

3.

Effects of oxygen on post-surgical infections during an individualised perioperative open-lung ventilatory strategy: a randomised controlled trial

BACKGROUND

We aimed to examine whether using a high fraction of inspired oxygen (FIO₂) in the context of an individualised intra- and postoperative open-lung ventilation approach could decrease surgical site infection (SSI) in patients scheduled for abdominal surgery.

METHODS

We performed a multicentre, randomised controlled clinical trial in a network of 21 university hospitals from June 6, 2017 to July 19, 2018. Patients undergoing abdominal surgery were randomly assigned to receive a high (0.80) or conventional (0.3) FIO₂ during the intraoperative period and during the first 3 postoperative hours. All patients were mechanically ventilated with an open-lung strategy, which included recruitment manoeuvres and individualised positive end-expiratory pressure for the best respiratory-system compliance, and individualised continuous postoperative airway pressure for adequate peripheral oxyhaemoglobin saturation. The primary outcome was the prevalence of SSI within the first 7 postoperative days. The secondary outcomes were composites of systemic complications, length of intensive care and hospital stay, and 6-month mortality.

RESULTS

We enrolled 740 subjects: 371 in the high FIO₂ group and 369 in the low FIO₂ group. Data from 717 subjects were available for final analysis. The rate of SSI during the first postoperative week did not differ between high (8.9%) and low (9.4%) FIO₂ groups (relative risk [RR]: 0.94; 95% confidence interval [CI]: 0.59-1.50; P=0.90]). Secondary outcomes, such as atelectasis (7.7% vs 9.8%; RR: 0.77; 95% CI: 0.48-1.25; P=0.38) and myocardial ischaemia (0.6% [n=2] vs 0% [n=0]; P=0.47) did not differ between groups.

CONCLUSIONS

An oxygenation strategy using high FIO₂ compared with conventional FIO₂ did not reduce postoperative SSIs in abdominal surgery. No differences in secondary outcomes or adverse events were found.

CLINICAL TRIAL REGISTRATION

NCT02776046.

Conservative oxygen therapy for mechanically ventilated adults with sepsis: a post hoc analysis of data from the intensive care unit randomized trial comparing two approaches to oxygen therapy (ICU-ROX)

PURPOSE

Sepsis is a common reason for intensive care unit (ICU) admission and mortality in ICU patients. Despite increasing interest in treatment strategies limiting oxygen exposure in ICU patients, no trials have compared conservative vs. usual oxygen in patients with sepsis.

METHODS

We undertook a post hoc analysis of the 251 patients with sepsis enrolled in a trial that compared conservative oxygen therapy with usual oxygen therapy in 1000 mechanically ventilated ICU patients. The primary end point for the current analysis was 90-day mortality. Key secondary outcomes were cause-specific mortality, ICU and hospital length of stay, ventilator-free days, vasopressor-free days, and the proportion of patients receiving renal replacement therapy in the ICU.

RESULTS

Patients with sepsis allocated to conservative oxygen therapy spent less time in the ICU with an SpO₂ ≥ 97% (23.5 h [interquartile range (IQR) 8-70] vs. 47 h [IQR 11-93], absolute difference, 23 h; 95% CI 8-38), and more time receiving an FiO₂ of 0.21 than patients allocated to usual oxygen therapy (20.5 h [IQR 1-79] vs. 0 h [IQR 0-10], absolute difference, 20 h; 95% CI 14-26). At 90-days, 47 of 130 patients (36.2%) assigned to conservative oxygen and 35 of 120 patients (29.2%) assigned to usual oxygen had died (absolute difference, 7 percentage points; 95% CI - 4.6 to 18.6% points; P = 0.24; interaction P = 0.35 for sepsis vs. non-sepsis). There were no statistically significant differences between groups for secondary outcomes but point estimates of treatment effects consistently favored usual oxygen therapy.

CONCLUSIONS

Point estimates for the treatment effect of conservative oxygen therapy on 90-day mortality raise the possibility of clinically important harm with this intervention in patients with sepsis; however, our post hoc analysis was not powered to detect the effects suggested and our data do not exclude clinically important benefit or harm from conservative oxygen therapy in this patient group.

CLINICAL TRIALS REGISTRY

ICU-ROX Australian and New Zealand Clinical Trials Registry number ACTRN12615000957594.

Obstetric perineal tears: risk factors, wound infection and dehiscence: a prospective cohort study

PURPOSE

To assess risk factors for perineal tears, wound infection and dehiscence among primiparous women.

METHODS

A prospective cohort study at four Danish hospitals (Odense, Esbjerg, Aarhus and Kolding) among 603 primiparous women sampled in three groups: 203 with none/labia/1st degree, 200 with 2nd degree, and 200 with 3rd/4th degree tears included between July 2015 and January 2018. Baseline data were obtained and a clinical examination of perineal wound healing was performed 11-21 days postpartum. Main outcome measurements were as follows: degree of perineal tear, 1st to 4th, analyzed with a case-control approach, infection (purulent drainage or wound abscess), and wound dehiscence (a gap between wound edges > 0.5 cm).

RESULTS

Instrumental delivery and birthweight > 4000 g increased the risk of 3rd/4th degree tears (adjusted Odds Ratio [aOR] 13.7, 95% confidence interval [CI] 5.48-34.1 and aOR 3.27, 95% CI 1.52-7.04, respectively). BMI > 35 kg/m2 increased the risk of wound infection and dehiscence (aOR 7.66, 95% CI 2.13-27.5 and aOR 3.46, 95% CI 1.10-10.9, respectively). Episiotomy tripled the risk of infection (aOR 2.97, 95% CI 1.05-8.41). Treatment with antibiotics during delivery and postpartum seemed to decrease the risk of dehiscence (aOR 0.32, 95% CI 0.15-0.70).

CONCLUSIONS

Instrumental delivery and high birth weight increased the risk of perineal tears. Severe obesity and episiotomy increased the risk of perineal wound complications. More focus on these women may be warranted postpartum. The use of prophylactic antibiotics among women in high risk of wound complications should be further investigated in interventional studies.

Practice patterns and perceptions of Australian and New Zealand anaesthetists towards perioperative oxygen therapy

We conducted a survey of Australian and New Zealand anaesthetists to determine self-reported practice of perioperative oxygen administration and to quantify perceptions regarding the perceived benefits and risks resulting from liberal oxygen therapy delivered in a manner consistent with the current World Health Organization guidelines. In addition, we sought feedback on the acceptability of several proposed clinical trial designs aiming to assess the overall effect of liberal and restricted perioperative oxygen regimens on patient outcomes. We developed a 23-question electronic survey that was emailed to 972 randomly selected Australian and New Zealand College of Anaesthetists (ANZCA) Fellows. We received responses from 282 of 972 invitees (response rate 29%). The majority of survey participants indicated that they routinely titrate inspired oxygen to a level they feel is safe (164/282, 58%) or minimise oxygen administration (82/282, 29%), while 5% of respondents indicated that they aim to maximise oxygen administration. The mean value for targeted intraoperative fraction inspired oxygen (FiO2) was 0.41 (standard deviation 0.12). Of the survey respondents, 2/282 (0.7%) indicated they believe that routine intra- and postoperative administration of ≥80% oxygen reduces the risk of surgical site infection. Well-designed and conducted randomised trials on this topic may help to better direct clinicians' choices. A high level of willingness to participate (80% of responses) in a study designed to investigate the impact of differing approaches to perioperative oxygen administration suggests that recruitment is likely to be feasible in a future study.

A mathematical model of the use of supplemental oxygen to combat surgical site infection

Infections are a common complication of any surgery, often requiring a recovery period in hospital. Supplemental oxygen therapy administered during and immediately after surgery is thought to enhance the immune response to bacterial contamination. However, aerobic bacteria thrive in oxygen-rich environments, and so it is unclear whether oxygen has a net positive effect on recovery. Here, we develop a mathematical model of post-surgery infection to investigate the efficacy of supplemental oxygen therapy on surgical-site infections. A 4-species, coupled, set of non-linear partial differential equations that describes the space-time dependence of neutrophils, bacteria, chemoattractant and oxygen is developed and analysed to determine its underlying properties. Through numerical solutions, we quantify the efficacy of different supplemental oxygen regimes on the treatment of surgical site infections in wounds of different initial bacterial load. A sensitivity analysis is performed to investigate the robustness of the predictions to changes in the model parameters. The numerical results are in good agreement with analyses of the associated well-mixed model. Our model findings provide insight into how the nature of the contaminant and its initial density influence bacterial infection dynamics in the surgical wound.

Surgical Site Infection: The Clinical and Economic Impact

Surgical site infection (SSI) following colorectal surgery is associated with worse postoperative outcomes, longer length of stay, and higher rates of readmission. SSI rates have been established as a surrogate metric for the overall quality of surgical care and are intricately tied to financial incentives and the public reputation of an institution. While risk factors and prevention mechanisms for SSI are well established, the rates of SSI remain high. This article discusses the clinical and economic impact of SSI and strategies for mitigating the risk of SSI through bundled prevention practices.

Prophylactic incisional negative pressure wound therapy reduces the risk of surgical site infection after caesarean section in obese women: a pragmatic randomised clinical trial

OBJECTIVE

To evaluate the reduction of surgical site infections by prophylactic incisional negative pressure wound therapy compared with standard postoperative dressings in obese women giving birth by caesarean section.

DESIGN

Multicentre randomised controlled trial.

SETTING

Five hospitals in Denmark.

POPULATION

Obese women (prepregnancy body mass index (BMI) ≥30 kg/m2 ) undergoing elective or emergency caesarean section.

METHOD

The participants were randomly assigned to incisional negative pressure wound therapy or a standard dressing after caesarean section and analysed by intention-to-treat. Blinding was not possible due to the nature of the intervention.

MAIN OUTCOME MEASURES

The primary outcome was surgical site infection requiring antibiotic treatment within the first 30 days after surgery. Secondary outcomes included wound exudate, dehiscence and health-related quality of life.

RESULTS

Incisional negative pressure wound therapy was applied to 432 women and 444 women had a standard dressing. Demographics were similar between groups. Surgical site infection occurred in 20 (4.6%) women treated with incisional negative pressure wound therapy and in 41 (9.2%) women treated with a standard dressing (relative risk 0.50, 95% CI 0.30-0.84; number needed to treat 22; P = 0.007). The effect remained statistically significant when adjusted for BMI and other potential risk factors. Incisional negative pressure wound therapy significantly reduced wound exudate whereas no difference was found for dehiscence and quality of life between the two groups.

CONCLUSION

Prophylactic use of incisional negative pressure wound therapy reduced the risk of surgical site infection in obese women giving birth by caesarean section.

TWEETABLE ABSTRACT

RCT: prophylactic incisional NPWT versus standard dressings postcaesarean in 876 women significantly reduces the risk of SSI.

Effect of Hyperoxygenation During Surgery on Surgical Site Infection in Colorectal Surgery

Purpose

Despite the use of different surgical methods, surgical site infection is still an important cause of mortality and morbidity in patients and imposes a considerable cost on the healthcare system. Administration of supplemental oxygen during surgery has been reported to reduce surgical site infection (SSI); however, that result is still controversial. This study was performed to evaluate the effect of hyperoxygenation during colorectal surgery on the incidence of wound infection.

Methods

This study was a prospective double-blind case-control study. The main aim of the study was to evaluate the effect of hyperoxygenation during colorectal surgery on the incidence of SSI. Also, secondary outcomes, such as atelectasis, pneumonia, respiratory failure, length of hospital stay, and required hospitalization in the intensive care unit were evaluated.

Results

SSI was recorded in 2 patients (2 of 40, 5%) in the hyperoxygenation group (FiO₂ 80%) and 6 patients (6 of 40, 15%) in the control group (FiO₂ 30%) (P < 0.05). Time of hospitalization was 6 ± 6.4 days in the hyperoxygenation group and 9.2 ± 2.4 days in the control group (P < 0.05).

Conclusion

This study showed a positive effect of hyperoxygenation in reducing SSI in colorectal surgery, especially surgery in an emergency setting. When the low risk, low cost, and effectiveness of this method in patients undergoing a laparotomy are considered, it is recommended for all patients undergoing colorectal surgery.

Characterisation of impaired wound healing in a preclinical model of induced diabetes using wide-field imaging and conventional immunohistochemistry assays

Major complications of diabetes lead to inflammation and oxidative stress, delayed wound healing, and persistent ulcers. The high morbidity, mortality rate, and associated costs of management suggest a need for non-invasive methods that will enable the early detection of at-risk tissue. We have compared the wound-healing process that occurs in streptozotocin (STZ)-treated diabetic rats with non-diabetic controls using contrast changes in colour photography (ie, Weber Contrast) and the non-invasive optical method Spatial Frequency Domain Imaging (SFDI). This technology can be used to quantify the structural and metabolic properties of in-vivo tissue by measuring oxyhaemoglobin concentration (HbO2 ), deoxyhaemoglobin concentration (Hb), and oxygen saturation (StO2 ) within the visible boundaries of each wound. We also evaluated the changes in inducible nitric oxide synthase (iNOS) in the dermis using immunohistochemistry. Contrast changes in colour photographs showed that diabetic rats healed at a slower rate in comparison with non-diabetic control, with the most significant change occurring at 7 days after the punch biopsy. We observed lower HbO2 , StO2 , and elevated Hb concentrations in the diabetic wounds. The iNOS level was higher in the dermis of the diabetic rats compared with the non-diabetic rats. Our results showed that, in diabetes, there is higher level of iNOS that can lead to an observed reduction in HbO2 levels. iNOS is linked to increased inflammation, leading to prolonged wound healing. Our results suggest that SFDI has potential as a non-invasive assessment of markers of wound-healing impairment.

Human Wounds and Its Burden: An Updated Compendium of Estimates

Significance: A 2018 retrospective analysis of Medicare beneficiaries identified that ∼8.2 million people had wounds with or without infections. Medicare cost estimates for acute and chronic wound treatments ranged from $28.1 billion to $96.8 billion. Highest expenses were for surgical wounds followed by diabetic foot ulcers, with a higher trend toward costs associated with outpatient wound care compared with inpatient. Increasing costs of health care, an aging population, recognition of difficult-to-treat infection threats such as biofilms, and the continued threat of diabetes and obesity worldwide make chronic wounds a substantial clinical, social, and economic challenge. Recent Advances: Chronic wounds are not a problem in an otherwise healthy population. Underlying conditions ranging from malnutrition, to stress, to metabolic syndrome, predispose patients to chronic, nonhealing wounds. From an economic point of view, the annual wound care products market is expected to reach $15-22 billion by 2024. The National Institutes of Health's (NIH) Research Portfolio Online Reporting Tool (RePORT) now lists wounds as a category. Future Directions: A continued rise in the economic, clinical, and social impact of wounds warrants a more structured approach and proportionate investment in wound care, education, and related research.

Multifunctional hypoxia imaging nanoparticles: multifunctional tumor imaging and related guided tumor therapy

Hypoxia is a common feature of most solid tumors. Having a comprehensive understanding of tumor hypoxia condition is a key to tumor therapy. Many hypoxia imaging nanoparticles have been used for tumor detection. However, simple optical hypoxia imaging is not enough for tumor diagnosis. Also, the tumor therapy process needs the information about the tumor hypoxia condition. Recently, researchers developed multimodal hypoxia tumor imaging nanoparticles and multifunctional hypoxia imaging-guided tumor therapy nanoparticles. The multimodal hypoxia imaging could produce more tumor region information and engage in functional tumor imaging to better understand the tumor condition. The multifunctional hypoxia imaging-guided tumor therapy could monitor the tumor therapy process and evaluate tumor therapeutic effect. Meanwhile, many challenges and limitations are still remaining in the application of multifunctional hypoxia nanoparticles. In this review, we first introduce the types of multifunctional hypoxia imaging nanoparticles. Then we focus on multimodal hypoxia imaging nanoparticles and hypoxia imaging-guided tumor therapy nanoparticles. We also discuss the challenges and future perspectives of this field. There has not been many studies in this field for now. We hope this review would bring more researchers' attention to this field so that it would substantially contribute to tumor precise therapy.

Surface-Adaptive and Initiator-Loaded Graphene as a Light-Induced Generator with Free Radicals for Drug-Resistant Bacteria Eradication

Since generating toxic reactive oxygen species is largely dependent on oxygen, bacteria-infected wounds' hypoxia significantly inhibits photodynamic therapy's antibacterial efficiency. Therefore, a novel therapeutic method for eradicating multidrug-resistant bacteria is developed based on the light-activated alkyl free-radical generation (that is oxygen independent). According to the polydopamine-coated carboxyl graphene (PDA@CG), an initiator-loaded and pH-sensitive heat-producible hybrid of bactericides was synthesized. According to fluorescence/thermal imaging, under the low pH of the bacterial infection sites, this platform turned positively charged, which allows their accumulation in local infection site. The plasmonic heating effects of PDA@CG can make the initiator decomposed to generate alkyl radical (R^•) under the followed near-infrared light irradiation. As a result, oxidative stress can be elevated, DNA damages in bacteria can be caused, and finally even multidrug-resistance death can be caused under different oxygen tensions. Moreover, our bactericidal could promote wound healing in vivo and negligible toxicity in vivo and in vitro and eliminate abscess. Accordingly, this study proves that combination of oxygen-independent free-radical-based therapy along with a stimulus-responsiveness moiety not only can be used as an effective treatment of multidrug-resistant bacteria infection, but also creates a use of a variety of free radicals for treatment of multidrug-resistant bacteria infection wounds.

Effect of Obesity on Complications in Short-Scar Breast Reduction: A Retrospective Study of 236 Consecutive Patients

Background

Prior studies have examined the relationship between obesity and adverse outcomes after reduction mammaplasty, suggesting a correlation between increasing body mass index (BMI) and postoperative complications. However, there is little data published regarding such correlation with respect to short-scar technique.

Methods

A total of 236 patients underwent short-scar mammaplasty with a superomedial pedicle from 2008 to 2014. The procedure was performed by a single surgeon at an academic medical center. Adverse outcomes included delayed healing, major wounds, nipple necrosis, fat necrosis, seroma, hematoma, infection, revision, and dog ear deformities. Univariate and multivariate logistic regression analyses were used to calculate crude and adjusted odds ratios for the association of BMI category with the development of any adverse outcome.

Results

Patients were grouped by the following BMI categories: <25 kg/m² (n = 27), 25 to <30 kg/m² (n = 71), 30 to <35 kg/m² (n = 73), 35 to <40 kg/m² (n = 45), and >40 kg/m² (n = 20). The mean follow-up period was 260 days. The total complication rate in each group was 22.2%, 23.9%, 27.4%, 33.3%, and 45.0%, respectively. Although the proportion of patients experiencing at least 1 adverse outcome increased across the ascending BMI categories (P trend = .145), there was no statistically significant difference between the groups.

Conclusion

This study of 236 patients who underwent short-scar reduction mammaplasty found a positive trend in the incidence of adverse outcomes as BMI increased. However, this was not statistically significant.

Development of a novel in situ gelling skin dressing: Delivering high levels of dissolved oxygen at pH 5.5

BACKGROUND AND AIMS

Wound healing requires appropriate oxygen and pH levels. Oxygen therapy and pH-modulating treatments have shown positive effects on wound healing. Thus, a dressing, which combines high levels of dissolved oxygen (DO) with the pH of intact skin, may improve wound healing. Our aims were to (1) formulate an in situ gelling dressing with high levels of DO and with the pH level of intact skin, (2) evaluate physical and chemical properties of the dressing, and (3) elucidate basic effects of elevated levels of DO on human skin cells in vitro.

METHODS

A dressing was formulated with 15 to 16 wt% poloxamer 407, acetate buffer, and oxygenated water. Stability of pH and DO, rheology, and shelf life were analysed. Furthermore, in vitro studies of the effect of increased levels of DO were performed.

RESULTS

An in situ gelling wound dressing, with a DO concentration ranging between 25 and 35 mg/L and a pH of 5.5, was formulated. The DO concentration was stable above 22 mg/L for at least 30 hours when applied on a surface at 35°C and covered for directed diffusion into the intended wound area. At storage, the dressing had stable pH for 3 months and stable DO concentration over 30 mg/L for 7 weeks. Increasing DO significantly enhanced intracellular ATP in human skin cells, without changing reactive oxygen species production, proliferation rate, or viability.

CONCLUSION

The developed dressing may facilitate wound healing by delivering controlled and stable oxygen levels, providing adjustable pH for optimized healing, and increasing intracellular ATP availability.

Neutrophils in Tissue Trauma of the Skin, Bone, and Lung: Two Sides of the Same Coin

Following severe tissue injury, patients are exposed to various danger- and microbe-associated molecular patterns, which provoke a strong activation of the neutrophil defense system. Neutrophils trigger and modulate the initial posttraumatic inflammatory response and contribute critically to subsequent repair processes. However, severe trauma can affect central neutrophil functions, including circulation half-life, chemokinesis, phagocytosis, cytokine release, and respiratory burst. Alterations in neutrophil biology may contribute to trauma-associated complications, including immune suppression, sepsis, multiorgan dysfunction, and disturbed tissue regeneration. Furthermore, there is evidence that neutrophil actions depend on the quality of the initial stimulus, including trauma localization and severity, the micromilieu in the affected tissue, and the patient's overall inflammatory status. In the present review, we describe the effects of severe trauma on the neutrophil phenotype and dysfunction and the consequences for tissue repair. We particularly concentrate on the role of neutrophils in wound healing, lung injury, and bone fractures, because these are the most frequently affected tissues in severely injured patients.

Effect of intraoperative hyperoxia on the incidence of surgical site infections: a meta-analysis

BACKGROUND

Whether supplemental intraoperative oxygen reduces surgical site infections remains unclear. Recent recommendations from the World Health Organization and Center for Disease Control to routinely use high inspired oxygen concentrations to reduce infection risk have been widely criticized. We therefore performed a meta-analysis to evaluate the influence of inspired oxygen on infection risk, including a recent large trial.

METHODS

A systematic literature search was performed. Primary analysis included all eligible trials. Sensitivity analyses distinguished studies of colorectal and non-colorectal surgeries, and excluded studies with high risk of bias. Another post-hoc sensitivity analysis excluded studies from one author that appear questionable.

RESULTS

The primary analysis included 26 trials (N=14,710). The RR [95%CI] for wound infection was 0.81 [0.70, 0.94] in the high vs. low inspired oxygen groups. The effect remained significant in colorectal patients (N=10,469), 0.79 [0.66, 0.96], but not in other patients (N=4,241), 0.86 [0.69, 1.09]. When restricting the analysis to studies with low risk of bias, either by strict inclusion criteria (N=5,047) or by researchers' judgment (N=12,547), no significant benefit remained: 0.84 [0.67, 1.06] and 0.89 [0.76, 1.05], respectively.

CONCLUSIONS

When considering all available data, intraoperative hyperoxia reduced wound infection incidence. However, no significant benefit remained when analysis was restricted to objective- or investigator-identified low-bias studies, although those analyses were not as well-powered. Meta-analysis of the most reliable studies does not suggest that supplemental oxygen substantively reduces wound infection risk, but more research is needed to fully answer this question.

Nanomedicines and gene therapy for the delivery of growth factors to improve perfusion and oxygenation in wound healing

Oxygen plays a key role in wound healing, and hypoxia is a major cause of wound healing impairment; therefore, treatments to improve hemodynamics and increase wound oxygenation are of particular interest for the treatment of chronic wounds. This article describes the roles of oxygen and angiogenesis in wound healing as well as the tools used to evaluate tissue oxygenation and perfusion and then presents a review of nanomedicines and gene therapies designed to improve perfusion and oxygenation and accelerate wound healing.

Topical oxygen therapy & micro/nanobubbles: a new modality for tissue oxygen delivery

Up to 15 billion dollars of US health care expenditure each year is consumed by treatment of poorly healing wounds whose etiologies are often associated with aberrancies in tissue oxygenation. To address this issue, several modes of tissue oxygen delivery systems exist, including Hyperbaric Oxygen Therapy (HBOT) and Topical Oxygen Therapy (TOT), but their efficacies have yet to be fully substantiated. Micro/nanobubbles (MNBs), which range anywhere from 100 μm to <1 μm in diameter and are relatively stable for hours, offer a new mode of oxygen delivery to wounds. The aim of this article is to systematically review literature examining the use of TOT for wound healing and use of MNBs for tissue oxygenation using the MEDLINE database. The search yielded 87 articles (12 MNB articles and 75 TOT articles), of which 52 met the inclusion criteria for this literature review (12 MNB articles and 40 TOT articles). Additionally, we present an analysis on the efficacy of our MNB generating technology and propose its use as a wound healing agent.