[Postoperative wound infections. Pathophysiology, risk factors and preventive concepts]

Analysing predictors of surgical site infections in patients undergoing emergency surgery for traumatic pulmonary haemorrhage

Identifying predictors for surgical site infections (SSIs) after emergency surgical treatment for traumatic pulmonary haemorrhage (TPH) is crucial for improving patient outcomes. This study aims to ascertain these predictors. In this comprehensive retrospective study, conducted from January 2020 to December 2023 at our institution, 75 patients were analysed, including a case group of 25 patients with SSIs and a control group of 50 without SSIs post-TPH surgery. Inclusion criteria focused on patients aged 18 and above undergoing thoracotomy or minimally invasive thoracic surgery for TPH. Exclusion criteria included compromised immune systems, chronic pulmonary diseases, prior thoracic surgery or active infections at admission. We assessed several predictors: anaemia; operation time over 2 h; hospital stay over 5 days; intraoperative blood loss exceeding 500 mL; body mass index (BMI) ≥25 kg/m2; age ≥ 50 years; use of surgical drains; the presence of open wounds; diabetes mellitus and non-prophylactic antibiotic use. Statistical analysis involved univariate and multivariate logistic regression, using SPSS Version 27.0. Univariate analysis revealed significant associations between SSIs and surgical drain placement, diabetes mellitus, open wounds and non-prophylactic antibiotic use (p < 0.01). Multivariate analysis confirmed these factors as significant predictors of SSIs, with notable odds ratios. Other variables like anaemia, extended hospital stay, excessive intraoperative blood loss, older age and higher BMI did not significantly predict SSIs. Significant predictors for SSIs following TPH surgery include surgical drain placement, diabetes mellitus, open wounds and non-prophylactic antibiotic use. Identifying and managing these risks is crucial in clinical practice to reduce SSIs incidence and improve patient outcomes.

Human skin biofilm model: translational impact on swabbing and debridement

OBJECTIVE

Wound biofilms are one of the greatest challenges in the therapy of hard-to-heal (chronic) wounds, as potent antimicrobial substances fail to eradicate bacteria within short incubation periods. Preclinical investigations using novel model systems that closely mimic the human wound environment and wound biofilm are required to identify new and effective therapeutic options. This study aims to identify bacterial colonisation patterns that are relevant for diagnosis and therapy.

METHOD

In this study, a recently established human plasma biofilm model (hpBIOM) was incorporated into a wound within human dermal resectates after abdominoplasty. The interaction of the biofilm-forming bacteria meticillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa with the skin cells was investigated. Possible effects on wound healing processes in correlation with the persistence of the biofilm in the wound environment were analysed in patients with leg ulcers of different aetiologies and biofilm burden.

RESULTS

Using haematoxylin and eosin staining, species-dependent infiltration modes of the bacteria into the wound tissue were determined for the pathogens MRSA and Pseudomonas aeruginosa. The spreading behaviour correlated with clinical observations of the spatial distributions of the bacteria. In particular, the clinically prominent Pseudomonas aeruginosa-specific distension of the wound margin was identified as epidermolysis due to persistent infiltration.

CONCLUSION

The hpBIOM applied in this study represents a potential tool for preclinical analyses dealing with approval processes for new antimicrobial applications. In terms of clinical practice, a microbiological swabbing technique including the wound margin should be routinely applied to prevent wound exacerbation.

Does the use of epicutaneous vacuum-assisted closure after revision surgery on the spine reduce further wound revision surgery?

PURPOSE

This study aimed to investigate the effect of epicutaneous vacuum therapy on the rate of unplanned spinal wound revisions compared with conventional wound dressing.

METHODS

This retrospective study included patients who underwent unplanned revision spine surgery after primary aseptic spine surgery who were treated at a level I spine centre between December 2011 and December 2019. Patients with revision surgery who required a further unplanned revision surgery during the inpatient stay were considered a treatment failure. The epicutaneous vacuum-assisted closure (Epi-VAC) therapy was the standard treatment method beginning in 2017 (the epi-VAC group). Before, conventional wound dressing was used (the control group (CG)). In addition, a one-to-one matched-pair comparison analysis was performed between both groups.

RESULTS

Of 218 patients, 48 were in the epi-VAC group. The mean age was 65.1 years (epi-VAC 68.2 to CG 64.3 years (P = 0.085)), and the mean body mass index (BMI) was 28.2 kg/m² (epi-VAC 29.4 to CG 27.9 kg/m² (P = 0.16)). No significant differences in the treatment failure rate could be detected between the two groups (epi-VAC 25% to CG 22.4% (P = 0.7)). There was also no significant difference for the matched-pair analysis (epi-VAC 26.1% to CG 15.2% (P = 0.3)). An elevated CRP level (C-reactive protein) immediately before the first wound revision was a significant risk factor for further revision surgery (treatment failure: 135.2 ± 128.6; no treatment failure: 79.7 ± 86.1 mg/l (P < 0.05)).

CONCLUSION

Concerning repeat unplanned wound revision after spinal revision surgery, we cannot demonstrate an advantage of the epicutaneous vacuum therapy over conventional wound dressing.

Antimicrobials cetylpyridinium-chloride and miramistin demonstrate non-inferiority and no "protein-error" compared to established wound care antiseptics in vitro

Concern about microbial tolerance and resistance to established antimicrobials drives research into alternatives for local antiseptic wound treatment. Precise efficacy profiles are thereby important in the evaluation of potential alternative antimicrobials, and protein interference ("protein error") is a key factor. Here, the antimicrobial efficacy of cetylpyridinium chloride (CPC) and miramistin (MST) was compared to the established antimicrobials octenidine (OCT), povidon-iodine (PVP-I), polyhexamethylene-biguanide (PHMB) and chlorhexidine (CHX). Efficacy was evaluated after 0.5, 1, 3, 5 and 10 min against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Enterococcus faecium and Candida albicans using an in vitro quantitative suspension method (based on DIN EN 13727). To investigate protein interference, 0.3% or 3% bovine albumin was used as the challenge. OCT and PVP-I demonstrated a significant efficacy within 0.5 min, regardless of the microbial organism and protein challenge (p < 0.01). CPC and MST showed no inferiority in efficacy, with only MST needing up to 3 min to achieve the same microbial reduction. PHMB and CHX also achieved significant reduction rates over the tested time-course, yet demonstrated a necessity for prolonged exposure (up to 10 min) for comparable reduction. A protein interference was predominantly observed for PHMB against S. aureus, but without statistically significant differences in antimicrobial efficacy between the 0.3% and 3% protein challenges. All other tested agents showed no relevant interference with the presence of protein. CPC and MST proved to be non-inferior to established wound antiseptics agents in vitro. In fact, CPC showed a more efficient reduction than PHMB and CHX despite there being an introduced protein challenge. Both agents demonstrated no significant "protein error" under challenging conditions (3% albumin), posing them as valid potential candidates for alternative antimicrobials in wound management.

Preoperative Octenidine Application in Breast Reconstruction Surgery

BACKGROUND/AIM

Postoperative infection in implant-based reconstructive breast surgery is a common problem. The preoperative application of a disinfecting washing agent may reduce postoperative infection rates. This retrospective analysis aimed to evaluate whether preoperative Octenisan^® application yields a reduction in postoperative complications or infection rates in breast reconstructive surgery.

PATIENTS AND METHODS

Between 2016 and 2019, 127 women received implant-based breast reconstruction at the municipal hospital of Cologne, Holweide, Germany. A total of 197 treatments were performed. After giving consent, patients were asked to use Octenisan^® wash lotion for five days before breast reconstructive surgery. All patients were asked by a simple questionnaire whether they performed showering and washing according to the proposed protocol. In 96 cases patients did adhere to the protocol. In 101 cases they did not. Patient cohorts were then divided into patients who had applied Octenisan^® wash lotion and patients who had not. Endpoints were defined as minor complications with no implant loss and major complications with consecutive implant loss.

RESULTS

Patient adherence to the application regimen was 48.7%. Overall minor complications occurred in 34.4% with preoperative Octenidine usage and 36.6% without preoperative Octenidine usage. Major complications happened in 7% with preoperative Octenidine and 5% without Octenidine. Overall, there was no significant difference concerning minor or major complication rates.

CONCLUSION

Preoperative washing protocols involving the Octenisan^® wash lotion is relatively cheap and easy to follow. There is evidence that washing protocols result in a reduction of S. aureus infections leading to a better perioperative outcome. Octenisan^® is safe to use in implant-based breast reconstructive surgery and is not associated with higher risks for patients. Our study did not yield any significant reduction in perioperative and postoperative complication and infection rates. This is attributed to a relatively low study population. Wash lotion compliance was only 48.7%. Proper patient education is crucial. With those preliminary data, it is now possible to design a larger analysis since patient adherence to washing protocol with Octenisan^® wash lotion has been established.

Comparative analysis of biofilm models to determine the efficacy of antimicrobials

Biofilms are one of the greatest challenges in today's treatment of chronic wounds. While antimicrobials kill platonic bacteria within seconds, they are rarely able to harm biofilms. In order to identify effective substances for antibacterial therapy, cost-efficient, standardized and reproducible models that aim to mimic the clinical situation are required. In this study, two 3D biofilm models based on human plasma with immune cells (lhBIOM) or based on sheep blood (sbBIOM) containing S. aureus or P. aeruginosa, are compared with the human biofilm model hpBIOM regarding their microscopic structure (scanning electron microscopy; SEM) and their bacterial resistance to octenidine hydrochloride (OCT) and a sodium hypochlorite (NaOCl) wound-irrigation solution. The three analyzed biofilm models show little to no reaction to treatment with the hypochlorous solution while planktonic S. aureus and P. aeruginosa cells are reduced within minutes. After 48 h, octenidine hydrochloride manages to erode the biofilm matrix and significantly reduce the bacterial load. The determined effects are qualitatively reflected by SEM. Our results show that both ethically acceptable human and sheep blood based biofilm models can be used as a standard for in vitro testing of new antimicrobial substances. Due to their composition, both fulfill the criteria of a reality-reflecting model and therefore should be used in the approval for new antimicrobial agents.

Clinical Evaluation of Wound Healing in Split-Skin Graft Donor Sites Using Microscopic Quantification of Reepithelialization

OBJECTIVE

Impaired or delayed wound healing is a common health problem. However, it remains challenging to predict whether wounds in patients will heal without complication or will have a prolonged healing time. In this study, the authors developed an objective screening tool to assess wound healing using microscopic quantification of reepithelialization in a split-thickness skin graft wound model and used this tool to identify risk factors for defective wound healing.

DESIGN

Thirty patients (16 male and 14 female) were included in this prospective study. Anterior thigh skin biopsies from the donor site region of partial-thickness skin grafts were dressed with moisture-retentive dressings, and biopsies were examined on days 0, 2, 5, and 10 postoperatively by microscopy. Images were then transferred to a computer for image analysis and epithelial measurements (epithelial thickness and total reepithelialized surface). The effects of gender, age, body mass index, and smoking behavior on these wound healing parameters were determined.

RESULTS

The authors found comparable results for the computer and traditional measure methods. However, the time required to perform the measurements using the semiautomated computer method was less than half the time of the traditional method. Image capturing, enhancing, and analysis with the new method required approximately 2 minutes 30 seconds, whereas the traditional methods took up to 7 minutes per image. The total size of the reepithelialized surface (P = .047) and percentage of the biopsy resurfaced with epithelia (P = .011) at day 10 were both significantly higher in male patients compared with female patients. In patients younger than 55 years, reepithelialized areas were significantly thicker than in patients older than 55 years (P = .008), whereas the size of the reepithelialized surface showed no differences. No significant differences in reepithelialization parameters were found concerning body mass index and smoking behavior.

CONCLUSIONS

Both male gender and older age impair reepithelialization rate and epithelial thickness in partial-thickness skin graft donor site wounds. In contrast, body mass index and smoking behavior have not been shown to be influencing factors on reepithelialization. Thus, microscopic quantification of reepithelialization might be a suitable method for predicting complications associated with wound healing.

Biocompatibility of magnesium implants in primary human reaming debris-derived cells stem cells in vitro

BACKGROUND

Use of magnesium for resorbable metal implants is a new concept in orthopaedic and dental medicine. The majority of studies on magnesium's biocompatibility in vitro have assessed the short-term effect of magnesium extract on cells. The aim of this study was to evaluate the influence of direct exposure to magnesium alloys on the bioactivity of primary human reaming debris-derived (HRD) cells.

MATERIALS AND METHODS

Pure Mg, Mg2Ag, WE43 and Mg10Gd were tested for biocompatibility. The study consisted of assessment of cell viability by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test, evaluation of alkaline phosphatase (ALP) content, and study of cell morphology under light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), along with determination of calcification and pH changes induced by magnesium.

RESULTS

The number of viable cells in the presence of Mg2Ag was high over the entire observation period. Inhibition of ALP content in osteogenic differentiating HRD was caused by pure Mg at day 14 and 28. All other magnesium alloys did not affect the ALP content. Exposure of HRD to magnesium increased the amount of lysosomes and endocytotic vesicles. Cellular attachment was generally the best for those crystals that formed on the surface of all materials. A decrease was observed in Ca(2+) in the medium from day 1 to day 14.

CONCLUSIONS

In terms of cell morphology, cell viability and differentiation, cell density and the effect on the surrounding pH, Mg2Ag showed the most promising results. All magnesium materials induced calcification, which is beneficial for orthopaedic and dental applications.

Extracellular micronutrient levels and pro-/antioxidant status in trauma patients with wound healing disorders: results of a cross-sectional study

Background

Disorders in wound healing (DWH) are common in trauma patients, the reasons being not completely understood. Inadequate nutritional status may favor DWH, partly by means of oxidative stress. Reliable data, however, are lacking. This study should investigate the status of extracellular micronutrients in patients with DWH within routine setting.

Methods

Within a cross-sectional study, the plasma/serum status of several micronutrients (retinol, ascorbic acid, 25-hydroxycholecalciferol, α-tocopherol, β-carotene, selenium, and zinc) were determined in 44 trauma patients with DWH in addition to selected proteins (albumin, prealbumin, and C-reactive protein; CRP) and markers of pro-/antioxidant balance (antioxidant capacity, peroxides, and malondialdehyde). Values were compared to reference values to calculate the prevalence for biochemical deficiency. Correlations between CRP, albumin and prealbumin, and selected micronutrients were analyzed by Pearson’s test. Statistical significance was set at P < 0.05.

Results

Mean concentrations of ascorbic acid (23.1 ± 15.9 μmol/L), 25-hydroxycholecalciferol (46.2±30.6 nmol/L), β-carotene (0.6 ± 0.4 μmol/L), selenium (0.79±0.19 μmol/L), and prealbumin (24.8 ± 8.2 mg/dL) were relatively low. Most patients showed levels of ascorbic acid (<28 μmol/L; 64%), 25-hydroxycholecalciferol (<50 μmol/L; 59%), selenium (≤ 94 μmol/L; 71%) and β-carotene (<0.9 μmol/L; 86%) below the reference range. Albumin and prealbumin were in the lower normal range and CRP was mostly above the reference range. Plasma antioxidant capacity was decreased, whereas peroxides and malondialdehyde were increased compared to normal values. Inverse correlations were found between CRP and albumin (P < 0.05) and between CRP and prealbumin (P < 0.01). Retinol (P < 0.001), ascorbic acid (P < 0.01), zinc (P < 0.001), and selenium (P < 0.001) were negatively correlated with CRP.

Conclusions

Trauma patients with DWH frequently suffer from protein malnutrition and reduced plasma concentrations of several micronutrients probably due to inflammation, increased requirement, and oxidative burden. Thus, adequate nutritional measures are strongly recommended to trauma patients.

Bone wax in dermatologic surgery

Bone wax is an inert, malleable material used as a hemostatic agent in treating surgical defects. Healing by secondary intention is an appropriate approach for certain situations in dermatologic surgery. When surgical wounds are deep enough for such tissues as bone or cartilage to be exposed, dressings may adhere to granulation tissue, making removal and subsequent wound care difficult and painful. In such cases bone wax can be molded around deep tissues to create an ideal occlusive, hemostatic microenvironment that facilitates second-intention wound healing.

[EzPAP® therapy of postoperative hypoxemia in the recovery room : experiences with the new compact system of end-expiratory positive airway pressure]

BACKGROUND

Postoperative hypoxemia is a common complication in the anesthesia recovery room (ARR), which is predominantly based on the development of atelectasis, excessive intraoperative fluid shift and insufficient ventilation. The goal of this prospective observational study was to compare the effect of standard oxygen administration via a face mask with oxygen administration using the EzPAP® system, a device which additionally provides a positive end-expiratory pressure (PEEP).

METHODS

This study included 210 patients with postoperative hypoxemia (S(p)O(2) < 93%) subdivided into the control group (105 patients) and the EzPAP group (105 patients). Postoperative residual paralysis was excluded using relaxometry and a train of four (TOF) ratio of 0.9 was assumed to ensure sufficient recovery of respiratory function from neuromuscular blockade. Patients who received a reversal of neuromuscular blockade were excluded. In cases of hypoxemia (S(p)O(2) < 93%) control patients were treated with oxygen (6 l/min) using a face mask, whereas the EzPAP group received oxygen using the EzPAP® system. In order to adjust the PEEP in the EzPAP group, the O(2) flow was verified and measured by a manometer. After 1 h of oxygen therapy, the oxygen supply was stopped. In cases of reoccurring hypoxemia (S(p)O(2) < 93%, persistence > 5 min), the oxygen therapy was restarted in both groups via a facemask. Both groups were compared using repeat measurement analysis of variance (ANOVA), the unpaired t-test, the Mann-Whitney U-test, Fisher's exact test and the χ(2)-test. The correlation of O(2) flow and PEEP was evaluated by regression analysis and p < 0.05 was considered to be statistically significant. Apart from this a subgroup analysis was performed depending on body-mass index (BMI), American Society of Anesthesiologists (ASA) classification, intraoperative airway management, the use of neuromuscular blocking agents and co-existing disorders, e.g. chronic obstructive lung disease (COLD), obesity and chronic heart failure.

RESULTS

All patients were equally distributed between both groups with respect to demographic data, ASA classification, BMI, co-existing disorders and surgical procedures. The S(p)O(2) values did not differ between the EzPAP patients and the control group, except for 0.5 min after initiation of oxygen therapy: EzPAP group 96 ± 3.7% (mean ± standard deviation) versus the control group 93.8 ± 4.4% (p < 0.001). However, restarting oxygen therapy was less common in the EzPAP group (EzPAP group 25 versus control group 41, p = 0.03), as well as the occurrence of postoperative complications (EzPAP group 13 versus control group 25, p = 0.02), e.g. nosocomial pneumonia (0 versus 4) and wound infections (2 versus 3). Furthermore, patients with obesity and pulmonary disorders, such as COLD had a benefit from oxygen administration using the EzPAP device and showed higher postoperative than preoperative S(p)O(2) values. In contrast, the subgroup analysis of patients with heart failure did not reveal any differences between both groups and both groups did not differ in terms of time spent in the recovery room (EzPAP group 113 min versus control group 174.8 min, p = 0.2).

CONCLUSIONS

In this observational study oxygen supply using the EzPAP® system appeared to be at least equally as effective in the therapy of postoperative hypoxemia compared to standard oxygen supply using a face mask. In patients with a high risk of postoperative hypoxemia, such as patients with obesity and/or pulmonary disorders, oxygen administration using the EzPAP® system possibly improves pulmonary oxygenation more effectively and is longer lasting compared to standard oxygen supply via a face mask. Hence, the EzPAP® system represents a well-tolerated, effective, cost-effective and easily operated tool to improve postoperative oxygenation. In order to investigate the possibilities of this promising tool more intensively, randomized clinical trials are warranted.

Topical application of Sadat-Habdan mesenchymal stimulating peptide (SHMSP) accelerates wound healing in diabetic rabbits

Objective. Diminished wound healing is a common problem in diabetic patients due to diminished angiogenesis. SHMSP was found to promote angiogenesis. The present study was carried out to examine the effect of this peptide in healing of wounds in diabetic rabbits. Materials and Methods. Twenty male New Zealand rabbits were used in this study. Diabetes mellitus was induced and the rabbits were randomly divided into two equal groups: control group and peptide group. A-full thickness punch biopsy was made to create a wound of about 10 mm on the right ears of all rabbits. Every day, the wound was cleaned with saline in control groups. In the peptide group, 15 mg of SHMSP was applied after cleaning. On day 15th, all animals were sacrificed, and the wounds were excised with a rim of 5 mm of normal surrounding tissue. Histo-pathological assessment of wound healing, inflammatory cell infiltration, blood vessel proliferation, and collagen deposition was performed. Results. There were no deaths among the groups. There was significant increase in wound healing, blood vessel proliferation and collagen deposition, and significant decrease in inflammatory cell infiltration in the peptide group compared to the control group. Conclusion. Topical application of SHMSP improves wound healing in diabetic rabbits.

[Rational use of oxygen in anesthesiology and intensive care medicine]

Oxygen (O(2)) is the most frequently used pharmaceutical in anesthesiology and intensive care medicine: Every patient receives O(2) during surgery or during a stay in the intensive care unit. Hypoxia and hypoxemia of various origins are the most typical indications which are mentioned in the prescribing information of O(2): the goal of the administration of O(2) is either an increase of arterial O(2) partial pressure in order to treat hypoxia, or an increase of arterial O(2) content in order to treat hypoxemia. Most of the indications for O(2) administration were developed in former times and have seldom been questioned from that time on as the short-term side-effects of O(2) are usually considered to be of minor importance. As a consequence only a small number of controlled randomized studies exist, which can demonstrate the efficacy of O(2) in terms of evidence-based medicine. However, there is an emerging body of evidence that specific side-effects of O(2) result in a deterioration of the microcirculation. The administration of O(2) induces arteriolar constriction which will initiate a decline of regional O(2) delivery and subsequently a decline of tissue oxygenation. The aim of the manuscript presented is to discuss the significance of O(2) as a pharmaceutical in the clinical setting.