Wound hypoxia and acidosis limit neutrophil bacterial killing mechanisms

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.

Percutaneous drainage combined with hyperbaric oxygen therapy for pyogenic spondylitis with iliopsoas abscess

Study Design

A retrospective study.

Purpose

The purpose of this study was to evaluate outcomes in patients with pyogenic spondylitis accompanied by iliopsoas abscess who were treated by percutaneous drainage combined with hyperbaric oxygen (HBO) therapy.

Overview of Literature

To the best of our knowledge, there have been no previous reports of the use of percutaneous drainage combined with HBO therapy for the treatment of this condition.

Methods

Twenty-three patients (13 men, 10 women; mean age, 69.0 years; range, 45-85 years) were treated with percutaneous drainage combined with HBO therapy in addition to commonly used conservative therapy. Mean follow-up duration was 27.7 months (range, 12-48 months). Clinical outcomes and imaging examinations were retrospectively investigated.

Results

Symptoms such as low back pain, radicular pain, and hip pain resolved in all patients immediately after treatment. Mean time from the start of treatment to the return of C-reactive protein levels to normal or baseline values recorded before the onset of spondylitis was 28.3 days (range, 8-56 days). In the final set of follow-up radiographic studies, all patients were free from progressive destructive changes. Follow-up magnetic resonance images or computed tomography with contrast enhancement confirmed the disappearance or near-total resolution of the iliopsoas abscess cavity with healing of the pyogenic spondylitis in all 23 patients. No recurrences were observed during follow-up.

Conclusions

The present study suggests that patients with pyogenic spondylitis accompanied by iliopsoas abscess can be cured without a prolonged period of therapy or recurrence using this treatment.

Neutrophils generate microparticles during exposure to inert gases due to cytoskeletal oxidative stress

This investigation was to elucidate the mechanism for microparticle (MP) formation triggered by exposures to high pressure inert gases. Human neutrophils generate MPs at a threshold of ∼186 kilopascals with exposures of 30 min or more. Murine cells are similar, but MP production occurs at a slower rate and continues for ∼4 h, whether or not cells remain under pressure. Neutrophils exposed to elevated gas but not hydrostatic pressure produce MPs according to the potency series: argon ≃ nitrogen > helium. Following a similar pattern, gases activate type-2 nitric-oxide synthase (NOS-2) and NADPH oxidase (NOX). MP production does not occur with neutrophils exposed to a NOX inhibitor (Nox2ds) or a NOS-2 inhibitor (1400W) or with cells from mice lacking NOS-2. Reactive species cause S-nitrosylation of cytosolic actin that enhances actin polymerization. Protein cross-linking and immunoprecipitation studies indicate that increased polymerization occurs because of associations involving vasodilator-stimulated phosphoprotein, focal adhesion kinase, the H(+)/K(+) ATPase β (flippase), the hematopoietic cell multidrug resistance protein ABC transporter (floppase), and protein-disulfide isomerase in proximity to short actin filaments. Using chemical inhibitors or reducing cell concentrations of any of these proteins with small inhibitory RNA abrogates NOS-2 activation, reactive species generation, actin polymerization, and MP production. These effects were also inhibited in cells exposed to UV light, which photoreverses S-nitrosylated cysteine residues and by co-incubations with the antioxidant ebselen or cytochalasin D. The autocatalytic cycle of protein activation is initiated by inert gas-mediated singlet O2 production.

[Complications associated with inguinal orchiectomy and scrotal orchiectomy]

Inguinal excision of testis is technically an elementary surgical procedure. According to the indication (e.g., malignant tumors, infarction, inflammation), an inguinal or alternatively a transcrotal approach is possible. Despite its straightforwardness, surgery of the scrotum includes remarkable risks and complications such as postoperative hemorrhage, hematoma formation, infections, and disturbances of wound healing followed by insufficient unfavorable cosmetic results. Nerve injury may be accompanied by temporary or persistent paresthesias which have been documented in our patients undergoing orchiectomy.

Implementation of bundled interventions greatly decreases deep sternal wound infection following cardiovascular surgery

OBJECTIVE

Surgical site infection (SSI), particularly deep sternal wound infection (DSWI), is a serious complication after cardiovascular surgery because of its high mortality rate. We evaluated the effectiveness of an SSI bundle to reduce DSWI and identify the risk factors for DSWI.

METHODS

During the period January 2004 to February 2012, 1374 consecutive patients undergoing cardiovascular surgery via sternotomy were included. The cohort was separated into periods from January 2004 through February 2007 (period I, 682 patients) and March 2007 through February 2012 (period II, 692 patients). During period II, all preventive measures for DSWI were completed as an SSI bundle. We compared the DSWI rate between the 2 periods. Univariate and multivariate analyses were performed for the entire period to identify the risk factors for DSWI.

RESULTS

DSWI occurred in 13 patients (1.9%) during period I and in 1 patient (0.14%) during period II. The DSWI rate during period II was significantly decreased by 93%, compared with period I (P=.001). Independent risk factors for DSWI included obesity (odds ratio [OR], 3.4; 95% confidence interval [CI], 1.00-11.75; P=.049), the use of 4 sternal wires (OR, 8.2; 95% CI, 1.39-48.14; P=.020), long operative time (OR, 4.4; 95% CI, 1.20-16.23; P=.026), and postoperative renal failure (OR, 9.0; 95% CI, 2.44-33.30; P=.001).

CONCLUSIONS

Complete implementation of simple multidisciplinary prevention measures as a bundle can greatly decrease the incidence of DSWI.

Obesity and surgical wound healing: a current review

Objective. The correlation between obesity and deficient wound healing has long been established. This review examines the current literature on the mechanisms involved in obesity-related perioperative morbidity. Methods. A literature search was performed using Medline, PubMed, Cochrane Library, and Internet searches. Keywords used include obesity, wound healing, adipose healing, and bariatric and surgical complications. Results. Substantial evidence exists demonstrating that obesity is associated with a number of postoperative complications. Specifically in relation to wound healing, explanations include inherent anatomic features of adipose tissue, vascular insufficiencies, cellular and composition modifications, oxidative stress, alterations in immune mediators, and nutritional deficiencies. Most recently, advances made in the field of gene array have allowed researchers to determine a few plausible alterations and deficiencies in obese individuals that contribute to their increased risk of morbidity and mortality, especially wound complications. Conclusion. While the literature discusses how obesity may negatively affect health on various of medical fronts, there is yet to be a comprehensive study detailing all the mechanisms involved in obesity-related morbidities in their entirety. Improved knowledge and understanding of obesity-induced physiological, cellular, molecular, and chemical changes will facilitate better assessments of surgical risks and outcomes and create efficient treatment protocols for improved patient care of the obese patient population.

Store-operated Ca²⁺ entry mediated regulation of polarization in differentiated human neutrophil-like HL-60 cells under hypoxia

The regulation of neutrophil polarization by calcium entry is critical for maintaining an effective host response. Hypoxia has a major effect on the apoptosis of neutrophils, however the role of store-operated Ca2+ entry (SOCE) in neutrophil polarization under hypoxia remains to be elucidated. In the present study, we examined the polarization of differentiated human neutrophil-like HL-60 (dHL-60) cells exposed to hypoxia (3% O2) and the results demonstrated that the percentage of polarized cells following exposure to an N-formyl-Met-Leu-Phe (fMLP) gradient in the Zigmond chamber was increased. We examined stromal interaction molecule 1 (STIM1) and Orai1 expression in dHL-60 cells during hypoxia, and it was observed that the expression of STIM1 and Orai1 was significantly reduced at day 2. However, no apparent change was observed on the first day, indicating that this effect is dependent on stimulation time. Fluo-4/acetoxymethyl (AM) ester imaging also demonstrated that SOCE was decreased in dHL-60 cells. The plasmid overexpression assay demonstrated that the response of polarization was returned to the control level. We demonstrated the inhibitory role of SOCE on the polarization of dHL-60 cells under hypoxic conditions, which may be the mechanism for the adaptation of neutrophils to hypoxia. SOCE is also suggested to be a key modulator of immune deficiency under hypoxic conditions and is potentially a therapeutic target.

Prevention of surgical site infections

In the current era of pay-for-performance standards, the incidence of surgical site infections is increasingly becoming an institutional marker of quality assurance. Surgical site infections lead to increased morbidity and mortality in the surgical population and contribute to an already rising healthcare cost. As a result, the surgical community goes to great lengths to prevent this costly and occasionally lethal complication. Many practices are evidence based, however, many are not. In this article, the most commonly used preventive strategies in practice today and the evidence behind each are reviewed. In addition, an overview of the epidemiology, pathophysiology and microbiology of surgical site infections will be provided.

Analysis of surgical site infection after musculoskeletal tumor surgery: risk assessment using a new scoring system

Surgical site infection (SSI) has not been extensively studied in musculoskeletal tumors (MST) owing to the rarity of the disease. We analyzed incidence and risk factors of SSI in MST. SSI incidence was evaluated in consecutive 457 MST cases (benign, 310 cases and malignant, 147 cases) treated at our institution. A detailed analysis of the clinical background of the patients, pre- and postoperative hematological data, and other factors that might be associated with SSI incidence was performed for malignant MST cases. SSI occurred in 0.32% and 12.2% of benign and malignant MST cases, respectively. The duration of the surgery (P = 0.0002) and intraoperative blood loss (P = 0.0005) was significantly more in the SSI group than in the non-SSI group. We established the musculoskeletal oncological surgery invasiveness (MOSI) index by combining 4 risk factors (blood loss, operation duration, preoperative chemotherapy, and the use of artificial materials). The MOSI index (0-4 points) score significantly correlated with the risk of SSI, as demonstrated by an SSI incidence of 38.5% in the group with a high score (3-4 points). The MOSI index score and laboratory data at 1 week after surgery could facilitate risk evaluation and prompt diagnosis of SSI.

MR Imaging of Stem Cell Transplants in Arthritic Joints

About 43 million individuals in the US currently suffer from disabilities due to arthritis. Cartilage defects are the major source of pain in the affected joints. Current treatments, whilst alleviating some of the clinical symptoms, prove insufficient to cure the underlying irreversible cartilage loss. Stem cells represent a unique source for restoration of cartilage defects. Pre-clinical and clinical trials are currently pursued to investigate the potential of various types of stem cells and stem cell derived chondrocytes to repair arthritic joints. A major challenge with all stem cell-mediated tissue regeneration approaches is death of the transplanted cells with clearance by the immune system. Our current inability to diagnose successful or unsuccessful engraftment of transplanted cells non-invasively in vivo represents a major bottleneck for the development of successful stem cell therapies. A large variety of non-invasive Magnetic Resonance (MR) imaging techniques have been developed over the last decade, which enable sensitive in vivo detection of Matrix Associated Stem Cell Implants (MASI) and early diagnosis of related complications. While initially focused on successfully harvesting cellular MR imaging approaches with easily applicable SuperParamagnetic Iron Oxide Nanoparticles (SPIO), our team began to observe details that will facilitate clinical translation. We therefore started a broader effort to define a comprehensive set of novel, clinically applicable imaging approaches for stem cell transplants in patients. We established immediately clinically applicable nanoparticle labeling techniques for tracking stem cell transplants with MR imaging; we have evaluated the long term MR signal effects of iron oxide nanoparticle labeled MASI in vivo; and we have defined distinct signal characteristics of labeled viable and apoptotic MASI. This review article will provide an overview over these efforts and discuss important implications for clinical translation.

Perioperative supplemental oxygen to reduce surgical site infection after open fixation of high-risk fractures: a randomized controlled pilot trial

BACKGROUND

Higher concentrations of fraction of inspired oxygen (FIO2) have been shown to be associated with lower risk for surgical site infection in multiple studies outside the domain of orthopedic surgery. We evaluated the efficacy of high FIO2 administered during the perioperative period to reduce the rate of surgical site infection after open fixation of lower-extremity fractures at high risk of infection.

METHODS

We conducted a randomized controlled, parallel design, double-blind study. Patients sustaining high-energy tibial plateau, tibial pilon, and calcaneus fractures treated in a staged fashion were selected for enrollment because these injuries are associated with high risk of infection. The study population included 222 patients with 235 fractures. Consenting patients were randomized by random number sequence to either the treatment or the control group. Treatment group patients received 80% FIO2 intraoperatively and for 2 hours afterward. Control group patients received 30% FIO2 during the same period. Surgeons, patients, and personnel who performed wound assessments were blinded to group assignment. The primary outcome measure was surgical site infection as defined by the Centers for Disease Control criteria for postoperative wound infection.

RESULTS

The overall rates of postoperative surgical site infection were 12% (14 of 119 fractures) in the treatment group and 16% (19 of 116 fractures) in the control group (p = 0.31). Multivariate analysis, accounting for risk factors for infection, yielded the closest to a statistically significant reduction in the odds of infection with treatment (odds ratio, 0.54; p = 0.17). No treatment-associated events were observed.

CONCLUSION

Use of a high concentration of FIO2 during the perioperative period is safe and shows a trend toward reduction of surgical site infection in patients undergoing open operative fixation of high-energy traumatic lower-extremity fractures. Further study in a larger patient population is indicated.

LEVEL OF EVIDENCE

Therapeutic study, level III.

The medical use of oxygen: a time for critical reappraisal

Oxygen treatment has been a cornerstone of acute medical care for numerous pathological states. Initially, this was supported by the assumed need to avoid hypoxaemia and tissue hypoxia. Most acute treatment algorithms, therefore, recommended the liberal use of a high fraction of inspired oxygen, often without first confirming the presence of a hypoxic insult. However, recent physiological research has underlined the vasoconstrictor effects of hyperoxia on normal vasculature and, consequently, the risk of significant blood flow reduction to the at-risk tissue. Positive effects may be claimed simply by relief of an assumed local tissue hypoxia, such as in acute cardiovascular disease, brain ischaemia due to, for example, stroke or shock or carbon monoxide intoxication. However, in most situations, a generalized hypoxia is not the problem and a risk of negative hyperoxaemia-induced local vasoconstriction effects may instead be the reality. In preclinical studies, many important positive anti-inflammatory effects of both normobaric and hyperbaric oxygen have been repeatedly shown, often as surrogate end-points such as increases in gluthatione levels, reduced lipid peroxidation and neutrophil activation thus modifying ischaemia-reperfusion injury and also causing anti-apoptotic effects. However, in parallel, toxic effects of oxygen are also well known, including induced mucosal inflammation, pneumonitis and retrolental fibroplasia. Examining the available 'strong' clinical evidence, such as usually claimed for randomized controlled trials, few positive studies stand up to scrutiny and a number of trials have shown no effect or even been terminated early due to worse outcomes in the oxygen treatment arm. Recently, this has led to less aggressive approaches, even to not providing any supplemental oxygen, in several acute care settings, such as resuscitation of asphyxiated newborns, during acute myocardial infarction or after stroke or cardiac arrest. The safety of more advanced attempts to deliver increased oxygen levels to hypoxic or ischaemic tissues, such as with hyperbaric oxygen therapy, is therefore also being questioned. Here, we provide an overview of the present knowledge of the physiological effects of oxygen in relation to its therapeutic potential for different medical conditions, as well as considering the potential for harm. We conclude that the medical use of oxygen needs to be further examined in search of solid evidence of benefit in many of the current clinical settings in which it is routinely used.

High-concentration oxygen and surgical site infections in abdominal surgery: a meta-analysis

BACKGROUND

There has been recent interest in using high-concentration oxygen to prevent surgical site infections (SSIs). Previous meta-analyses in this area have produced conflicting results. With the publication of 2 new randomized controlled trials (RCTs) that were not included in previous meta-analyses, an updated review is warranted. Our objective was to perform a meta-analysis on RCTs comparing high- and low- concentration oxygen in adults undergoing open abdominal surgery.

METHODS

We completed independent literature reviews using electronic databases, bibliographies and other sources of grey literature to identify relevant studies. We assessed the overall quality of evidence using grade guidelines. Statistical analysis was performed on pooled data from included studies. A priori subgroup analyses were planned to explain statistical and clinical heterogeneity.

RESULTS

Overall, 6 studies involving a total of 2585 patients met the inclusion criteria. There was no evidence of a reduction in SSIs with high-concentration oxygen (risk ratio 0.77, 95% confidence interval 0.50-1.19, p = 0.24). We observed substantial heterogeneity among studies.

CONCLUSION

There is moderate evidence that high-concentration oxygen does not reduce SSIs in adults undergoing open abdominal surgery.

Hyperbaric oxygen therapy as adjunctive treatment of diabetic foot ulcers

The widespread use of HBO as an adjunctive treatment of diabetic foot ulcers has been founded on weak scientific evidence, but the consistency in positive outcomes in trials evaluating HBO on ulcer healing is noteworthy, not least as these results are in concert with data from in vitro and physiologic studies supporting the theoretical framework of HBO reversing hypoxia-induced abnormality. The long-term ulcer-healing rates of the nonrandomized controlled studies before the recent study by Margolis and colleagues, 77% with HBO versus 25% with standard treatment, are in concert with 1-year follow-up data from the 2 double-blind RCTs, 54% versus 25%. These 2 trials have put the use of HBO on firmer ground, but several issues, including health economics, developing robust selection criteria for treatment, optimizing treatment protocols, and identifying standards for when to start and stop treatment, remain to be elucidated. Not least, outcomes from further high-quality studies are needed. At present, HBO may be used as an adjunctive therapy in a select group of patients with diabetic foot ulcers that are difficult to heal.

Effects of stromal cell derived factor-1 and CXCR4 on the promotion of neovascularization by hyperbaric oxygen treatment in skin flaps

Hyperbaric oxygen (HBO) is known to increase the survival of skin flaps by promoting neovascularization; however, the detailed mechanisms involved are not fully understood. In the present study, we aimed to characterize the effects of HBO treatment on neovascularization and skin flap survival. We also analyzed the mechanisms associated with the expression of angiogenic molecules, such as stromal cell derived factor-1 (SDF‑1) and its specific receptor CXCR4, to assess the effects of SDF-1 and CXCR4 on the promotion of neovascularization by HBO treatment in skin flaps. The epigastric pedicle skin flap model was established in rats that were randomly divided into the following groups: i) sham‑operated (SH group); ii) ischemia followed by reperfusion and analysis on the third and fifth day (IR3d and IR5d groups, respectively) postoperatively; iii) ischemia followed by reperfusion, HBO treatment and analysis on the third and fifth day (HBO3d and HBO5d groups, respectively) postoperatively. In the two HBO groups, animals received 1 h of HBO treatment in a 2.0 ATA chamber with 100% O2 twice per day for 3 days and then daily for 2 consecutive days following surgery. On the postoperative third and fifth day, skin flap survival measurement, histological analysis, immunohistochemical staining and western blotting for SDF‑1 and CXCR4 expression, were performed. Compared with those of the IR groups, skin flap survival, microvessel density (MVD) and expression of SDF‑1 and CXCR4 proteins were significantly increased in the HBO groups. Pearson's correlation analysis demonstrated a positive correlation between MVD and the high expression of SDF‑1 and CXCR4 following HBO treatment. Results of this study suggested that the effects of HBO treatment in promoting neovascularization may be explained by the upregulation of SDF‑1 and CXCR4 expression in the skin flaps of rats.

Enhancing in vivo survival of adipose-derived stromal cells through Bcl-2 overexpression using a minicircle vector

Tissue regeneration using progenitor cell-based therapy has the potential to aid in the healing of a diverse range of pathologies, ranging from short-gut syndrome to spinal cord lesions. However, there are numerous hurdles to be overcome prior to the widespread application of these cells in the clinical setting. One of the primary barriers to effective stem cell therapy is the hostile environment that progenitor cells encounter in the clinical injury wound setting. In order to promote cellular survival, stem cell differentiation, and participation in tissue regeneration, relevant cells and delivery scaffolds must be paired with strategies to prevent cell death to ensure that these cells can survive to form de novo tissue. The Bcl-2 protein is a prosurvival member of a family of proteins that regulate the mitochondrial pathway of apoptosis. Using several strategies to overexpress the Bcl-2 protein, we demonstrated a decrease in the mediators of apoptosis in vitro and in vivo. This was shown through the use of two different clinical tissue repair models. Cells overexpressing Bcl-2 not only survived within the wound environment at a statistically significantly higher rate than control cells, but also increased tissue regeneration. Finally, we used a nonintegrating minicircle technology to achieve this in a potentially clinically applicable strategy for stem cell therapy.

A Prospective Randomized Study Comparing Non-absorbable Polypropylene (Prolene®) and Delayed Absorbable Polyglactin 910 (Vicryl®) Suture Material in Mass Closure of Vertical Laparotomy Wounds

Wound dehiscence is a postoperative complication encountered following abdominal surgery. A prospective randomized study was conducted to compare the incidence of wound dehiscence with a delayed absorbable and a nonabsorbable suture material in the mass closure of vertical laparotomy wounds. In one group, 100 patients were analyzed after closure with Prolene®, and in another group, 100 patients were analyzed after closure with Vicryl®. The incision was closed by continuous far and near suture technique using polypropylene (Prolene) suture in one group and a synthetic delayed absorbable polyglactin 910 (Vicryl) suture in the other group. There was significant difference in the incidence of wound dehiscence between the two groups: 6 % with Prolene and 17 % with Vicryl, (χ (2) = 5.944, 1 DF, P value = 0.0148). The overall incidence of wound dehiscence was 11.5 % in this study. The incidence of wound dehiscence in both the study groups was higher than expected as compared to previous literature. There was a significant difference between the two suture materials. In our study, Prolene is a better suture material for closure of vertical laparotomy wounds.

RKIP: much more than Raf kinase inhibitory protein

From its discovery as a phosphatidylethanolamine-binding protein in bovine brain to its designation as a physiological inhibitor of Raf kinase protein, RKIP has emerged as a critical molecule for maintaining subdued, well-orchestrated cellular responses to stimuli. The disruption of RKIP in a wide range of pathologies, including cancer, Alzheimer's disease, and pancreatitis, makes it an exciting target for individualized therapy and disease-specific interventions. This review attempts to highlight recent advances in the RKIP field underscoring its potential role as a master modulator of many pivotal intracellular signaling cascades that control cellular growth, motility, apoptosis, genomic integrity, and therapeutic resistance. Specific biological and functional niches are highlighted to focus future research towards an enhanced understanding of the multiple roles of RKIP in health and disease.

Oxygen and wound care: a review of current therapeutic modalities and future direction

While the importance of oxygen to the wound healing process is well accepted, research and technological advances continue in this field and efforts are ongoing to further utilize oxygen as a therapeutic modality. In this paper, the authors briefly review the role of oxygen in wound healing and discuss the distinct mechanism of action as well as the advantages and disadvantages of the three major oxygen-based therapies currently in clinical use (Hyperbaric Oxygen and Topical Oxygen and Continuous Diffusion of Oxygen), as well as review the existing literature regarding these distinct therapeutic modalities.

Hyperbaric oxygen therapy as adjunctive treatment for diabetic foot ulcers

Hyperbaric oxygen therapy (HBOT) has been suggested to improve healing of hard-to-heal diabetic foot ulcers. Although the wide use of HBOT as a treatment for diabetic foot ulcers has been founded on weak scientific ground, 2 well-designed randomized, double-blind, placebo-controlled studies have in recent years put HBOT on firmer ground as treatment for diabetic patients with chronic foot ulcers. The recognition of inclusion criteria in these studies may help identify a select group of diabetic patients with hard-to-heal ulcers who might benefit from HBOT. In this review, we discuss the rationale behind the use of HBOT, its clinical application, and possible treatment complications.

Fluorinated methacrylamide chitosan hydrogel systems as adaptable oxygen carriers for wound healing

In this study a series of novel, biocompatible hydrogels able to repeatedly takeup and deliver oxygen at beneficial levels have been developed by conjugating various perfluorocarbon (PFC) chains to methacrylamide chitosan via Schiff base nucleophilic substitution, followed by photopolymerization to form hydrogels. The synthesized fluorinated methacrylamide chitosan (MACF) hydrogels were confirmed by high resolution (19)F NMR. Synthesized MACF hydrogels were tested for their ability to takeup and then release oxygen for future use in dermal wound healing. Depending on the PFC substitution type maximum O(2) uptake was observed within 2-6h, followed by complete release to the surrounding environment (5% CO(2)) within 12-120h at oxygen partial pressures of 1-25mm Hg h(-1), providing outstanding system tuning for wound healing and regenerative medicine. MACFs with the most fluorines per substitution showed the greatest uptake and release of oxygen. Interestingly, adding PFC chains with a fluorinated aromatic group considerably enhanced oxygen uptake and extended release compared with a linear PFC chain with the same number of fluorine molecules. MACF hydrogels proved to be readily reloaded with oxygen once release was complete, and regeneration could be performed as long as the hydrogel was intact. Fibroblasts were cultured on MACFs and assays confirmed that materials containing more fluorines per substitution supported the most cells with the greatest metabolic activity. This result was true, even without oxygenation, suggesting PFC-facilitated oxygen diffusion from the culture medium. Finally, MACF gradient hydrogels were created, demonstrating that these materials can control oxygen levels on a spatial scale of millimeters and greatly enhance cellular proliferative and metabolic responses.

Hypercapnia accelerates wound healing in endothelial cell monolayers exposed to hypoxia

INTRODUCTION

While tissue hypoxia is known to play a critical role in the process of vascular injury and repair, the effect of hypercapnia on this process remains uncertain. We investigated whether hypercapnia might influence endothelial cell wound healing under the influence of hypoxia.

MATERIALS AND METHODOLOGY

Monolayers of human umbilical venous endothelial cells (HUVECs) were scratch-wounded and incubated under different levels of O2, CO2, and pH in the environment.

RESULTS

Inhibition of wound healing was observed in the HUVEC monolayers under the hypoxic condition as compared to the normoxic condition. Both hypercapnic acidosis and buffered hypercapnia, but not normocapnic acidosis improved the rate of wound healing under the influence of hypoxia. The beneficial effect of hypercapnia was associated with stimulation of cell proliferation, without effects on cell adhesion, migration or apoptosis. On the other hand, the stimulatory effect of hypercapnia on wound healing and cell proliferation was not noted under normoxic conditions.

CONCLUSION

These results suggest that hypercapnia, rather than acidosis per se, accelerated the wound healing in HUVEC monolayers cultured under hypoxic conditions. The effect of hypercapnia on wound healing was due, at least in part, to the stimulation of cell proliferation by hypercapnia.

Inflammatory neovascularization during graft-versus-host disease is regulated by αv integrin and miR-100

Acute graft-versus-host disease (GvHD) is a complex process involving endothelial damage and neovascularization. Better understanding of the pathophysiology of neovascularization during GvHD could help to target this process while leaving T-cell function intact. Under ischemic conditions, neovascularization is regulated by different micro RNAs (miRs), which potentially play a role in inflamed hypoxic GvHD target organs. We observed strong neovascularization in the murine inflamed intestinal tract (IT) during GvHD. Positron emission tomography imaging demonstrated abundant αvβ3 integrin expression within intestinal neovascularization areas. To interfere with neovascularization, we targeted αv integrin-expressing endothelial cells, which blocked their accumulation in the IT and reduced GvHD severity independent of immune reconstitution and graft-versus-tumor effects. Additionally, enhanced neovascularization and αv integrin expression correlated with GvHD severity in humans. Expression analysis of miRs in the inflamed IT of mice developing GvHD identified miR-100 as significantly downregulated. Inactivation of miR-100 enhanced GvHD indicating a protective role for miR-100 via blocking inflammatory neovascularization. Our data from the mouse model and patients indicate that inflammatory neovascularization is a central event during intestinal GvHD that can be inhibited by targeting αv integrin. We identify negative regulation of GvHD-related neovascularization by miR-100, which indicates common pathomechanistic features of GvHD and ischemia.

Should perioperative supplemental oxygen be routinely recommended for surgery patients? A Bayesian meta-analysis

OBJECTIVE

The purpose of this study is to use updated data and Bayesian methods to evaluate the effectiveness of hyperoxia to reduce surgical site infections (SSIs) and/or mortality in both colorectal and all surgery patients. Because few trials assessed potential harms of hyperoxia, hazards were not included.

BACKGROUND

Use of hyperoxia to reduce SSIs is controversial. Three recent meta-analyses have had conflicting conclusions.

METHODS

A systematic literature search and review were performed. Traditional fixed-effect and random-effect meta-analyses and Bayesian meta-analysis were performed to evaluate SSIs and mortality.

RESULTS

Traditional meta-analysis yielded a relative risk of an SSI with hyperoxia among all surgery patients of 0.84 [95% confidence interval (CI): 0.73-0.97] and 0.84 (95% CI: 0.61-1.16) for the fixed-effect and random-effect models, respectively. The probabilities of any risk reduction in SSIs among all surgery patients were 77%, 81%, and 83% for skeptical, neutral, and enthusiastic priors. The subset analysis of colorectal surgery patients increased the probabilities to 86%, 89%, and 92%. The probabilities of at least a 10% reduction were 57%, 62%, and 68% for all surgery patients and 71%, 75%, and 80% among the colorectal surgery subset.

CONCLUSIONS

There is a moderately high probability of a benefit to hyperoxia in reducing SSIs in colorectal surgery patients; however, the magnitude of benefit is relatively small and might not exceed treatment hazards. Further studies should focus on generalizability to other patient populations or on treatment hazards and other outcomes.

Infection following operations on the central nervous system: deconstructing the myth of the sterile field

Neurosurgical patients are at a high risk for infectious sequelae following operations. For neurosurgery in particular, the risk of surgical site infection has a unique implication given the proximity of the CSF and the CNS. Patient factors contribute to some degree; for example, cancer and trauma are often associated with impaired nutritional status, known risk factors for infection. Additionally, care-based factors for infection must also be considered, such as the length of surgery, the administration of steroids, and tissue devascularization (such as a craniotomy bone flap). When postoperative infection does occur, attention is commonly focused on potential lapses in surgical “sterility.” Evidence suggests that the surgical field is not free of microorganisms. The authors propose a paradigm shift in the nomenclature of the surgical field from “sterile” to “clean.” Continued efforts aimed at optimizing immune capacity and host defenses to combat potential infection are warranted.

Prevention of anastomotic leakage after total gastrectomy with perioperative supplemental oxygen administration: a prospective randomized, double-blind, controlled, single-center trial

BACKGROUND

The role of supplemental oxygen therapy in the healing of esophagojejunal anastomosis is still very much in an experimental stage. The aim of the present prospective, randomized study was to assess the effect of administration of perioperative supplemental oxygen therapy on esophagojejunal anastomosis, where the risk of leakage is high.

METHODS

We enrolled 171 patients between January 2009 and April 2012 who underwent elective open esophagojejunal anastomosis for gastric cancer. Patients were assigned randomly to an oxygen/air mixture with a fraction of inspired oxygen (FiO2) of 30 % (n = 85) or 80 % (n = 86). Administration commenced after induction of anesthesia and was maintained for 6 h after surgery.

RESULTS

The overall anastomotic leak rate was 14.6 % (25 of 171): 17 patients (20 %) had an anastomotic dehiscence in the 30 % FiO2 group and 8 (9.3 %) in the 80 % FiO2 group (P < 0.05). The risk of anastomotic leak was 49 % lower in the 80 % FiO2 group (relative risk 0.61; 95 % confidence interval 0.40-0.95) versus 30 % FiO2.

CONCLUSIONS

Supplemental 80 % FiO2 provided during and for 6 h after major gastric cancer surgery to reduce postoperative anastomotic dehiscence should be considered part of ongoing quality improvement activities related to surgical care, with few risks to the patient and little associated cost.

Supplemental oxygen therapy: Important considerations in oral and maxillofacial surgery

The administration of supplemental oxygen is an essential element of appropriate management for a wide range of clinical conditions; crossing different medical and surgical specialities. The present review summarizes the role of supportive oxygen therapy in various clinical conditions encountered in our day-to-day practice in the speciality of oral and maxillofacial surgery; including major trauma, shock, sepsis; perioperative and postoperative considerations and in patients with various other medical comorbidities. Regular and judicious use of oxygen as a drug is thus recommended in our day-to-day practice in oral and maxillofacial surgery to reduce the morbidity and improve the prognosis of patients.

An update review on risk factors and scales for prediction of deep sternal wound infections

Surgical site infections are the most common nosocomial infections in surgical patients. The preventable and the unmodifiable risk factors for deep sternal wound infections (DSWI) have been amply assessed in the literature. The aim of this review was to describe the results of the numerous published studies to describe all the DSWI risk factors and the scales devised to predict SWI, with a view to providing an update on this issue. A comprehensive search of the Medline and Embase databases was performed (considering studies from January 1995 to April 2011); and a manual search was also conducted using references cited in original publications and relevant review articles. There are several risk factors associated with DSWI, which could be classified in four categories as demographic (e.g. sex and age), behavioural (e.g. smoking and obesity), baseline clinical conditions (e.g. diabetes, hypertension and COPD) and surgical operative risk factors (e.g. duration of operation and emergency operation). Six scales for predicting the risk of DSWI are described in the literature: they vary not only in accuracy but also in ease of application and they are applied at different times (some only preoperatively and others also postoperatively). This study provides a broad update on our knowledge of the risk factors for DSWI and the scales for prediction with a view to improving the management of infections at cardiosurgery units.

Acid and base secretion in freshly excised nasal tissue from cystic fibrosis patients with ΔF508 mutation

BACKGROUND

Cystic fibrosis (CF) is caused by a misfunctional CF transmembrane conductance regulator (CFTR) protein, which is believed to contributes to the regulation of the airway surface liquid (ASL) pH. This study investigated acid and base secretion in freshly excised human nasal tissues from CF patients homozygous for the ΔF508 mutation.

METHODS

Human nasal mucosa was collected during sinus surgery and investigated in Ussing chambers. Mucosal equilibrium pH values and rate of acid and base secretion were determined using the pH-stat technique.

RESULTS

The equilibrium pH of nasal epithelia from ΔF508 CF patients with chronic rhinosinusitis (CRS) was pH = 7.08 ± 0.09 and was significantly lower compared to nasal epithelia from CRS patients without CF (pH = 7.33 ± 0.06) and normal subjects (pH = 7.34 ± 0.08, n = 6). The rate of base secretion in CF nasal tissues was 11.8 ± 2.4 nmol · min(−1) · cm(−2), which was significantly lower than normal (57.2 ± 9.2 nmol · min(−1) · cm(−2)). The HCO3(−) secretory rate was further increased by forskolin by 16.1% in normal, but not in CF tissues.

CONCLUSION

Our data suggests that CF patients exhibited significantly lower base secretion by the nasal airway epithelium. It is possible that improper regulation of ASL pH in CF may negatively impact the innate host defense system.

Understanding the host inflammatory response to wound infection: an in vivo study of Klebsiella pneumoniae in a rabbit ear wound model

Wound infection development is critically dependent on the complex interactions between bacteria and host. Klebsiella pneumoniae has become an increasingly common wound pathogen, but its natural history within wounds has never been studied. Using a validated, in vivo rabbit ear model, wounds were inoculated with K. pneumoniae at different concentrations (10²-10⁷ colony-forming units) with measurement of viable and nonviable bacterial counts, histological wound-healing parameters, and host inflammatory gene expression at multiple time points postinoculation (48, 96, and 240 hours). Bacteria and wound morphologies were evaluated with scanning electron microscopy. Comparable experiments were performed in ischemic ears to model immune response impairment. All wounds, despite different inoculants, equilibrated to similar bacterial concentrations by 96 hours. With a 10⁶ colony-forming units inoculant, wounds at 240 hours showed decreased bacterial counts (p < 0.01), with a corresponding improvement in healing (p < 0.01) and a decrease in inflammatory response (p < 0.05). In contrast, ischemic wounds revealed impaired inflammatory gene expression (p < 0.05) resulting in higher steady-state bacterial concentrations (p < 0.01), impaired healing (p < 0.05), and biofilm formation on scanning electron microscopy. We conclude that a normal inflammatory response can effectively stabilize and overcome a K. pneumoniae wound infection. An impaired host cannot control this bacterial burden, preventing adequate healing while allowing bacteria to establish a chronic presence. Our novel study quantitatively validates the host immune response as integral to wound infection dynamics.

Comparison of tissue oxygen saturation in ovariohysterectomized dogs recovering on room air versus nasal oxygen insufflation

OBJECTIVE

To compare tissue oxygen saturation in ovariohysterectomized dogs recovering postoperatively on room air versus nasal oxygen insufflation.

DESIGN

Prospective clinical study.

SETTING

University teaching hospital.

ANIMALS

Twenty dogs undergoing ovariohysterectomy.

INTERVENTIONS

Dogs were randomized to breathe either room air or 100 mL/kg/min of nasal oxygen insufflation for 2 hours postoperatively. Tissue oxygen saturation (StO(2)) was evaluated at 2 mm and 20 mm lateral to the surgical incision, as well as in the inguinal region using a noninvasive tissue oximeter.

MEASUREMENTS AND MAIN RESULTS

In dogs recovered on nasal oxygen insufflation (n = 10), tissue oxygen saturation was significantly higher--20 mm from the surgical site (88.44 ± 2.50%, P = 0.02) and in the inguinal region (83.56 ± 1.91%, P = 0.032)-- compared to dogs recovered on room air (n = 10, 79.11% ± 2.50 and 77.12% ± 1.91, respectively).

CONCLUSIONS

In ovariohysterectomized dogs, oxygen supplementation for 2 hours postoperatively improves tissue oxygen saturation 20 mm adjacent to the linea alba and in the inguinal region. Oxygen supplementation in postoperative dogs is an inexpensive and easily applicable method to improve tissue oxygen saturation.

Hyperbaric oxygen therapy as treatment of diabetic foot ulcers

Hyperbaric oxygen therapy (HBO) could be described as a short-term, high-dose oxygen inhalation and diffusion therapy, delivered systemically through airways and blood, achieved by having the patient breathing concentrated oxygen at a pressure higher than 1 absolute atmosphere. In clinical practice, monoplace or multiplace hyperbaric chambers are used to achieve this. Treatment is usually given as daily 90- to 120-min-long HBO sessions at pressures between 2.0 and 2.5 absolute atmosphere, aiming for 30-40 treatment sessions. The use of HBO as treatment of diabetic foot ulcers has been founded on weak scientific ground, although the outcomes from previous studies are in concert with the conclusions from preclinical studies and supports the theoretical framework of HBO reversing hypoxia-induced pathology. Two well-designed randomized double-blind trials have put HBO on firmer ground and may justify adjunctive HBO treatment to a selected group of patients with nonhealing diabetic foot ulcers. Some health economic studies suggest potential cost effectiveness, but these studies are limited by deficient primary clinical data and should be interpreted with caution. Several issues remain to be addressed, such as developing robust criteria to improve treatment protocols, determining which patients are likely to benefit, and when to start and stop treatment.

Colorectal Infraperitoneal anastomosis: the effects of perioperative supplemental oxygen administration on the anastomotic dehiscence

BACKGROUND

The role of supplemental oxygen therapy in the healing of colorectal anastomosis is still very much at an experimental stage. The aim of the present study, prospective randomized, was to assess the effect of administration of perioperative supplemental oxygen therapy on infraperitoneal anastomosis, where the risk of leakage is higher.

METHODS

We enrolled 72 patients between February, 2008 and February, 2011, who underwent elective open infraperitoneal anastomosis for rectal cancer (middle and low). Patients were assigned randomly to an oxygen/air mixture with a fraction of inspired oxygen (FiO2) of 30% (n = 37) or 80% (n = 35). Administration was commenced after induction of anesthesia and maintained for 6 h after surgery.

RESULTS

The overall anastomotic leak rate was 16.6% (12 out of 72); 8 patients (21.6%) had an anastomotic dehiscence in the 30% FiO2 group and 4 (11.4%) in the 80% FiO2 group (p < 0.05). The risk of anastomotic leak was 46% lower in the 80% FiO2 group (RR, 0.63; 95% confidence interval, 0.42–0.98) vs. the 30% FiO2.

CONCLUSION

Therefore, supplemental 80% FiO2 during and for 6 h after major rectal cancer surgery, reducing postoperative anastomotic dehiscence, should be considered part of ongoing quality improvement activities related to surgical care, with few risks to the patient and little associated cost.